1 Introduction

Sauropod dinosaurs are certainly among the most conspicuous elements of Mesozoic terrestrial vertebrate faunas. They include the largest terrestrial vertebrates and were the dominant herbivores in many Jurassic and Cretaceous ecosystems, probably accounting for a great part of vertebrate body mass in many environments in which they were abundant (e.g. Foster 2003). Their systematics were long thought to be especially problematic (Romer 1966), but research in the past fifteen years has greatly helped to resolve the general interrelationships of sauropods, although the exact placement of several taxa remains enigmatic (see e.g. Upchurch et al. 2004; Carballido and Sander 2014). However, the origin and early evolution of the group is still less well understood, and the interrelationships of non-sauropodan sauropodomorphs and the question of the timing and biogeography of the origin of sauropods are still controversial (see Peyre de Fabrègues et al. 2015; McPhee and Choiniere 2018). The origin of sauropods from more basal sauropodomorphs—the group formerly known as “prosauropods”, which is now generally considered to be paraphyletic (see e.g. McPhee et al. 2015; Otero et al. 2015; Apaldetti et al. 2018)—has recently come into focus with the identification of several “prosauropod” taxa as close relatives of sauropods (e.g. Yates 2004, 2007) and the discovery of other Late Triassic and Early Jurassic sauropodomorphs that are close to the origin of this clade (e.g. Buffetaut et al. 2000; Yates and Kitching 2003; Yates et al. 2010; Pol et al. 2011; McPhee et al. 2015, 2018; Otero et al. 2015; Peyre de Fabrègues and Allain 2016; Apaldetti et al. 2018). Together with the sauropods, these taxa are united in a clade named Sauropodiformes, defined as all sauropodomorphs that are more closely related to Saltasaurus than to Massospondylus (McPhee et al. 2014).

Sauropodomorph dinosaurs from the Late Triassic of Europe have long been known, ever since the original descriptions of Thecodontosaurus (Riley and Stutchbury 1836) and Plateosaurus (Meyer 1837), and numerous species have been described since, although the validity of many taxa remains debated (see e.g. Huene 1932; Galton 2001a, b; Yates 2003; Prieto-Marquez and Norell 2011). However, there is general consensus that the vast majority of European Triassic sauropodomorphs represents basal, non-sauropodiform taxa, including Thecodontosaurus, Pantydraco, Efraasia, Ruehleia, and Plateosaurus (e.g. Apaldetti et al. 2013; McPhee et al. 2015; Otero et al. 2015; Wang et al. 2017). The only European Triassic sauropodomorph that probably represents a basal sauropodiform is the poorly known Camelotia borealis from the Rhaetian of England (Galton 1985, 1998). Sauropodiforms seem to be generally rare, although widely distributed in the Late Triassic. Apart from the European Camelotia, taxa described so far include Lessemsaurus and Ingentia from the Norian/Rhaetian Los Colorados Formation of Argentina (Bonaparte 1999; Pol and Powell 2007a; Apaldetti et al. 2018), and Blikanasaurus, Melanorosaurus and Meroktenos from the Late Triassic Lower Elliot Formation of South Africa and Lesotho (Galton 1985; Galton and Heerden 1985; Yates 2007; Peyre de Fabrègues and Allain 2016). Three further sauropodiform taxa are usually said to be Late Triassic in age, the Argentinean Mussaurus (Bonaparte and Vince 1979; Pol and Powell 2007b; Otero and Pol 2013), the South African Antetonitrus (Yates and Kitching 2003; McPhee et al. 2014), and the genus Isanosaurus from Thailand (Buffetaut et al. 2000). However, the Laguna Colorada Formation that yielded Mussaurus has recently been dated as Early Jurassic (D. Pol, pers. com. to OR, 2016), and recent fieldwork in the area where Antetonitrus was found indicates that the type locality is placed in the Upper Elliot Formation and thus also Early Jurassic in age (McPhee et al. 2017). Likewise, the Upper Nam Phong Formation that has yielded Isanosaurus has recently been dated as Early Jurassic (Racey and Goodall 2009).

Triassic sauropodomorph dinosaurs from Switzerland were long only known from the fragmentary type material of Gresslyosaurus ingens, which was found in 1856 by geologist A. Gressly in sediments of the Keuper at Niederschönthal near Basel. The species was named by Rütimeyer in the same year (Rütimeyer 1856a, b) and more fully described a year later (Rütimeyer 1857). This animal was subsequently regarded as a teratosaurid (a supposedly carnivorous family of prosauropods) by Huene (1907-8, 1932), but has recently usually been regarded as belonging to Plateosaurus, either within the species Plateosaurus engelhardti (e.g. Galton 1986, 2001b), or as a separate species, Plateosaurus ingens (e.g. Yates 2007; Yates et al. 2010; McPhee et al. 2015; Otero et al. 2015).

The most important sauropodomorph locality in the Triassic of Switzerland is certainly the Gruhalde Quarry at Frick, which has yielded a mass accumulation of Plateosaurus from the Norian Upper Variegated Marls (Sander 1992; Hofmann and Sander 2014). Sauropodomorph fossils from this locality were first excavated by Urs Oberli in the late 1970s and scientifically described by Galton (1986), and since then, many partial to complete articulated skeletons have been found in at least three levels (Pabst, pers. com. in Hofmann and Sander 2014).

Further sauropodomorph remains were found in the Norian/Rhaetian beds of the Canton Schaffhausen, but these have only received a preliminary description so far. First remains were reported from the locality of Hallau by Peyer (1943a), who referred a dorsal vertebra to the genus Gresslyosaurus. This material, plus additional specimens collected in the vicinity of Schleitheim, were subsequently briefly described and referred to Plateosaurus engelhardti by Galton (1986). The aim of the current paper is a revision of materials found at Schleitheim, including the remains described by Galton (1986) and so far undescribed elements in the collections of the Museum zu Allerheiligen in Schaffhausen, as well as remains from a recent excavation led by one of us (HF).

2 Materials and methods

The material described here comes from the Upper Triassic (probably upper Norian) of Canton Schaffhausen, northern Switzerland. Remains referred to basal sauropodomorph dinosaurs in the collection of the Palaeontological Institute and Museum, University of Zurich (PIMUZ) came from two localities, Hallau and Schleitheim, both in the Canton Schaffhausen (Fig. 1). In Hallau (locality Bratelen), two separate excavation campaigns, one in 1915 by F. Schalch (Schaffhausen), and a second in 1942 by B. Peyer (University of Zurich), exposed the Jurassic-Triassic boundary, and numerous vertebrate remains were collected from the “Rhät-Bonebed” between the Lower Hettangian “Psilonotenschichten” and the underlying “Zanclodonmergel” (an equivalent of the Knollenmergel of south-western Germany; see Schalch and Peyer 1919; Peyer 1943a, b, 1956). The material from Schleitheim (locality Santierge) was collected by E. Schutz (Neunkirch) in 1952–1954 and donated to the University of Zurich in 1955. Some of these remains were briefly described and figured by Galton (1986), who referred all of this material to Plateosaurus engelhardti.

Fig. 1
figure 1

Geological map with the localities Schleitheim-Santierge, Hallau-Bratelen and Hallau-Schwärzibuck in the western part of Canton Schaffhausen, Switzerland (license for reproduction of the geological map by swisstopo, December 11, 2019)

Galton (1986: Fig. 5) identified a distal end of a femur and one dorsal vertebral centrum as coming from Hallau, and a distal part of a humerus and a proximal ulna (Galton 1986: pl. 1, Figs. 21, 22 and 23) as being derived from Schleitheim. He noticed that the provenance of the rest of material was unclear, as Peyer (1943b) did not specify the material found at Hallau, apart from one dorsal vertebra, and the material from Schleitheim had never been described.

During a recent re-examination of the material, we noticed that several of the bones were marked with the letter “J”, which Schutz used to identify material coming from Schleitheim-Santierge, including the distal end of the femur. Furthermore, several fragments marked with this letter were found to belong to a single, large right ilium, on which also the element described as ulna by Galton (1986) fitted, representing the pubic peduncle. This element clearly represents a new taxon and is made the holotype of a new species below. Two of the caudal vertebrae showed the mark mentioned above, and one of the dorsal vertebrae was identified as being derived from the same locality on an old, hand-written label, whereas an anterior dorsal could be united with its neural arch that also showed the mark. As the remaining posterior cervical and two dorsal vertebral centra fit in size, morphology and preservation with the two vertebrae positively identified as coming from Schleitheim, we interpret them as also coming from this locality and probably representing the same individual. A distorted anterior caudal vertebra without locality information fits in size with the last preserved dorsal vertebra and is therefore also tentatively referred to the same animal. A small distal caudal vertebra fits in preservation and, probably, size, but cannot be positively identified as coming from Schleitheim. The element is described below, but a possible referral to the same taxon should be seen as tentative. Likewise, a pedal ungual differs from vertebrate remains of Hallau in colour and preservation and thus might also represent the specimen from Schleitheim. Unfortunately, Schutz (unpublished notes, MzA) noted the stratigraphic position of the remains he excavated, but did not record their spatial distribution, so the association of the remains cannot be established. As all of the material [including the humerus already noted to be derived from Schleitheim by Galton (1986)] is of fitting size to represent a single individual, and there is no duplication of elements, we interpret all of these remains as representing a single animal. This interpretation is supported by the presence of the pubic peduncle of the left ilium, which fits exactly in size and morphology with the pubic peduncle of the right ilium. However, it might be noted that there is at least one sauropodomorph element from the excavation of Schutz that does not fit in size with the rest of the material, an isolated right astragalus (see below).

A number of additional specimens from the same locality, but collected much later (mainly in the 1980s), are present in the collections of the Museum zu Allerheiligen in Schaffhausen. These specimens include seven vertebrae and a partial right humerus. They are comparable in size and morphology to the material described above. Especially the humerus is noteworthy in this respect, as it represents the other (right) side than the humerus in the collections in Zurich (left humerus), is of the same size, and coincides in all comparable characters with this specimen. Thus, this material probably represents the same taxon or, at least partially, even the same individual as the material collected by Schutz, although at least some of the remains were collected from the surface some 20–30 m away from the original excavation site.

Finally, one of us (HF) led an excavation in the Upper Triassic sediments of Schleitheim-Santierge in autumn of 2016, at the approximate locality where the right humerus mentioned above was found, some 20–30 m away from the original excavation site of Schutz. In this excavation, bones were found in a thin (ca. 30 cm) series of partially conglomeratic carbonate sandstones to fine conglomerates intercalated as lenticular layers in brownish mud (Fig. 2), just on top of the yellow-violet marls of the Gruhalde Member of the Klettgau Formation (former “Zanclodonmergel” or “Knollenmergel”). Most of the larger skeletal elements represent sauropodomorphs remains, and at least some of them fit in size with the material collected by Schutz. Although it seems possible that all of these remains belong to a single, partially reworked skeleton, any referral of this material to the same taxon as the remains collected by Schutz is tentative at best. However, this material will also be documented briefly.

Fig. 2
figure 2

Correlation of Upper Triassic to Lower Jurassic sections in the localities Hallau-Bratelen and Schleitheim-Santierge

Further basal sauropodomorph material was collected by E. Schutz in the area of Hallau, at the locality Hallau-Schwärzibuck (Fig. 1) in 1954 from a correlating “Rhät-Bonebed”. Here, Schutz collected a scapula, a distal end of a femur, and two phalanges of a large, basal sauropodomorph. This material cannot be referred to the same taxon as the one identified from Schleitheim, but will be documented briefly, as will be a vertebra from the excavation by Schalch and Peyer at Hallau-Bratelen. A list of specimens and their current identification can be found in Table 1.

Table 1 List of materials detailing provenance and identification proposed here

In order to test the phylogenetic position of the sauropodomorph from Schleitheim, we included the new taxon in the matrix of Apaldetti et al. (2018), with several changes added based on McPhee et al. (2015), an addition of several new characters and changes in some codings based on own observations. One character [absence or presence of a tibiofibular crest in the femur; c. 360 of Apaldetti et al. (2018)] was excluded, as it was found to be invariable in the ingroup after recoding, and character 366 of Apaldetti et al. (2018) was subsumed in their character 305, as modified by McPhee et al. (2015: c. 310). The morphology of one other character [Buttress between preacetabular process and the supraacetabular crest of the ilium: present (0); absent (1); c. 250 of Apaldetti et al. (2018)] was unclear as defined, and thus we modified its wording to “Supraacetabular crest on the anterodorsal margin of the acetabulum: absent (0), present (1)” in order to better reflect the original character of Gauthier (1986), the source for this character identified by Otero et al. (2015). All taxa were recoded accordingly. We furthermore added four additional basal sauropod taxa from the Early or early Middle Jurassic, including Ohmdenosaurus (Wild 1978), Amygdalodon (Cabrera 1947; Casamiquela 1963; Rauhut 2003a), Spinophorosaurus (Remes et al. 2009; codings mainly based on McPhee et al. 2015), and Volkheimeria (Bonaparte 1979, 1986). On the other hand, the very incomplete and poorly preserved Gresslyosaurus ingens (Plateosaurus ingens in the source matrices) was excluded, as the material is currently being re-prepared and is in need of revision (Meyer et al. 2003); any codings for this taxon in previous matrices should therefore be regarded as tentative. The resulting matrix thus had 66 taxa scored for 382 characters. The matrix was analysed using TNT 1.1 (Goloboff et al. 2008), using heuristic tree search starting from 1000 replicates of Wagner trees (with random addition sequence of taxa) followed by TBR branch swapping (saving 10 trees per replicate). Given the somewhat uncertain association of the remains of the original excavation of Schutz, we ran three analyses, one including all of the material of the original excavation of Schutz that we interpret as probably belonging to a single individual (though not the material collected later that we tentatively refer to the same taxon), and further analyses with character codings restricted to the type ilium and the referred material, respectively. Furthermore, in a further analysis we reanalysed the dataset including all of the material using implied weights with a k = 12, as outlined by Goloboff et al. (2018). Character support for the different nodes and character transformations were analysed in Mesquite 3.51 (Maddison and Maddison 2018). The character list can be found in the appendix, and the matrices are deposited at Morphobank (http://www.morphobank.org) under project 2320.

Concerning the definition of Sauropoda, we follow the emerging consensus to use the node-based definition originally proposed by Salgado et al. (1997), who defined the clade as Vulcanodon and Saltasaurus and all descendants of their most recent common ancestor (see Peyre de Fabrègues et al. 2015; McPhee and Choiniere 2018).

Institutional abbreviations BSPG, Bayerische Staatssammmlung für Paläontologie und Geologie, Munich, Germany; MB, Museum für Naturkunde, Berlin, Germany; MCP, Museu de Ciências e Tecnologia PUCRS, Porto Alegre, Brazil; MzA, Museum zu Allerheiligen, Schaffhausen, Switzerland; PIMUZ, Palaeontological Institute and Museum of the University of Zurich, Switzerland; PVL, Paleontolgía de Vertebrados, Instituto Muíguel Lillo, Tucumán, Argentina; PVSJ, Paleontología de Vertebrados, Universidad Nacional de San Juan, San Juan, Argentina; SAM, Iziko South African Museum, Cape Town, South Africa; SMNS, Staatliches Museum für Naturkunde Stuttgart, Germany; UFSM, Universidade Federal de Santa Maria, Brazil.

3 Geology and stratigraphy

Hallau and Schleitheim are municipalities of the Klettgau, about 10 km east of the city of Schaffhausen, forming the boundary region of Canton Schaffhausen (Switzerland) to Baden-Württemberg (Germany) in the Wutach valley. Its hills and valleys expose sections of Upper Triassic to Lower Jurassic sediments, which allow good stratigraphic correlations from south-western Germany to the Tabular and Folded Jura in northern and western Switzerland (Figs. 1, 2). The Upper Triassic (Mittelkeuper) documents a continental environment with the sandy “Schilfsandstein” and “Stubensandstein” and the overlying marls of the “Zanclodonmergel” or “Knollenmergel”, renamed as Stuttgart, Steigerwald, Löwenstein and Trossingen Formations in south-western Germany (Etzold and Schweitzer 2005), and as new members of the Klettgau Formation in northern Switzerland (Jordan et al. 2016). Peyer (1943b) noted several bones of Gresslyosaurus sp. (vertebrae, fragments of limb bones, and a tooth) at the top of his unit c (see Fig. 2; “Zanclodonmergel”, now Gruhalde Member, Jordan et al. 2016) at Hallau (locality Bratelen), but the material could not be identified in the collections. Achilles and Schlatter (1986) dated the upper part of the “Zanclodonmergel” at Hallau (locality Bratelen) using palynostratigraphy as upper Middle Keuper (= upper Norian).

The overlying “Rhät-Bonebed” at Hallau was described by Schalch and Peyer (1919) and Peyer (1943b) as a compact conglomerate with cemented dolomitic clasts (unit d, thickness 0.25 m) and a loose marly bonebed (unit e, thickness 1.00 m). More than eight tons of material were washed in 1915 and 1942, and numerous isolated teeth, scales and bones of fish, reptiles and early mammaliaforms were separated. Schalch and Peyer (1919) published a short list of vertebrate remains (Gresslyosaurus sp., Termatosaurus alberti, Megalosaurus sp., other not yet identified reptiles, labyrinthodont amphibians, Hybodus sp., Hybodoconchus, ganoid scales), and figured several teeth of the dipnoan Ceratodus parvus and the actinopterygian Sargodon tomicus, both used as their main criteria to presume a Rhaetian age of the bonebed. Peyer (1943a, p. 261) notes again the dinosaur bones and the tooth found in 1915 and 1942, as belonging to Gresslyosaurus ingens, and added, that these dinosaur remains could be reworked from the underlying “Zanclodonmergel”. Peyer (1956) described 71 teeth of mammals and mammal-like reptiles from the “Rhät-Bonebed”, which were later revised by Clemens (1980). This author discussed the presumed Rhaetian age of the bonebed and wrote: “… the Hallau bonebed local fauna might be of Rhaetian age. It is probably not older than Middle Keuper (Norian) and no younger than the Psiloceras johnstoni Zone, early, but not earliest Hettangian”. Tatarinov (1985) identified another supposed dinosaur tooth in Peyer’s material as representing a heterodontosaurid, but this identification was challenged by Butler et al. (2006), who could only identify this tooth as an undetermined archosaur. A new genus and species of rhynchocephalian lepidosaur from Peyer’s vertebrate material was published by Whiteside et al. (2017) who also introduced the new lithostratigraphic name Bratelen Bonebeds.

Further vertebrate material was collected by E. Schutz in 1954 from a 2.10 m thick “Rhät-Bonebed” from an outcrop in a forest near Schwärzibuck, 350 m NNW of the locality Hallau-Bratelen. He donated the sieved material, some hundred fish teeth and small lepidosaurs in 1955 to the University of Zurich (Whiteside et al. 2017). Some larger dinosaur bones were deposited in a local museum at Neunkirch; these fossils are described below and are now in the inventory of the Museum zu Allerheiligen, Schaffhausen.

As noted above, the dinosaur material from Schleitheim (locality Santierge) was collected in 1952–1954. According to the unpublished notes of E. Schutz, deposited at the MzA, the big bones came from a hard conglomeratic layer in grey greenish to reddish marls with a thickness of c. 30 cm, together with teeth of Ceratodus and ostracods. The remains were recovered in situ in a small excavation “c. 50 m in front of the quarry in the Liassic, c. 20 m below the highest road at the margin of a recently created field” (translated from the notes of E. Schutz).

Hofmann (1981) mapped the area of Hallau and Schleitheim in detail and noted a larger bone fragment that he identified as Gresslyosaurus ingens, found as isolated fossil in a field, covering the “Rhät-Tone, Bonebed usw.” (Hofmann 1981, p. 11) at the locality Harnischbogen, only 600 m ENE of the locality Schleitheim-Santierge.

Achilles and Schlatter (1986), who studied a new section about 200 m east of Peyer’s 1942 excavation at Hallau-Bratelen, did not find any bonebed. They identified a typical Liassic palynomorph assemblage from bed f (Planorbis to Liasicus Zone; Fig. 2) overlying directly bed c (“Knollenmergel”) with palynomorphs from the upper Middle Keuper (= upper Norian). They also studied samples from the “Rhät-Bonebed” from other sections at Hallau and Schleitheim, but could not find any palynomorphs. They suggest that the “Rhät-Bonebed” represents probably a bonebed of the upper Middle Keuper (= Upper Norian).

In 2016, one of us (HF) led a small excavation in the Upper Triassic sediments of Schleitheim-Santierge (Fig. 2), some 20–30 m away from the original excavation site of Schutz. The unpublished sketch of the section made by Schutz in 1954 could be confirmed, studying a 15 m long and 3 m deep trench in a gently sloping, just harvested field. The bedding was nearly horizontal, but slightly deformed by a landslide. Above the yellow to violet dolomitic marls of the Gruhalde Member with calcrete nodules (former “Zanclodonmergel” or “Knollenmergel”), disarticulated dinosaur bones were found together with vertebrae, teeth and scales of phytosaurs, amphibians, osteichthyan and chondrichthyan fishes (Bratelen Bonebeds, Fig. 2). Ostracods were the only invertebrate fossils; indeterminable coaly plant remains were rare. The often fragmentary and abraded fossils were embedded in pebbly mudstones and carbonate sandstones to fine conglomerates intercalated as three, up to 15 cm thick lenticular cemented layers in brownish marl. The carbonate sandstones to fine conglomerates never include quartz, feldspar nor mica grains, but well rounded clasts of limestone and dolomite with diameters from 1 to 10 mm. Up to 5 cm large intraclasts of red marl and calcrete nodules must be eroded from the underlying Gruhalde Member. The in total 35 cm thick Bratelen Bonebeds were overlain by more than 2 m of green-grey calcareous clay with several layers of white calcrete nodules of probably late Triassic age. A tooth and a bone fragment of a phytosaur were the only vertebrate fossils, but ostracods are very common. Test samples on palynomorphs were negative (E. Schneebeli-Hermann, pers. comm.). The section in the 3 m deep trench was deeply weathered and the base of the Lower Jurassic was not reached. Calcareous clay together with bonebeds were also mapped and described from Santierge and a few other natural and artificial outcrops in the Klettgau by Hofmann (1981: p. 10/11, “Rhät-Tone, Bonebed usw.”). However, the Rhaetian age was not proved.

The “Rhät-Bonebed” or Bratelen Bonebeds (Whiteside et al. 2017) from Hallau and Schleitheim are directly overlain by black marls and limestone of the “Psilonotenschichten” (Fig. 2; Hallau Bed of the Schambelen Member, Staffelegg Formation; Reisdorf et al. 2011). Schalch and Peyer (1919) and also Achilles and Schlatter (1986) found ammonites of the Lower Hettangian in the Hallau section (unit f); however, the lowermost subzone of the planorbis zone could not be identified. This lowermost subzone was found near Beggingen, 4 km northeast of Schleitheim (Schlatter 1983). As a consequence, a hiatus of some million years at the Triassic-Jurassic boundary is typical for the area, spanning the whole Rhaetian and locally also the earliest Hettangian. It could have been a long time of non-deposition during the Rhaetian or important erosion in the latest Rhaetian and earliest Hettangian.

Extensive fieldwork by one of us (HF) documents that the Bratelen Bonebeds (former “Rhät-Bonebeds”) in the Klettgau form a characteristic lithostratigraphic bed on top of the Gruhalde Member, where all the studied sauropodomorph material from Hallau and Schleitheim was found (Fig. 2). Variable in composition and thickness, and even locally missing, the Bratelen Bonebeds records an important erosional event at the end or after the deposition of the Gruhalde Member (late Norian?). Rhaetian sediments have never been proved by litho-, bio- or chronostratigraphy in the Canton Schaffhausen. The Bratelen Bonebeds, without any siliciclastic sand grains, clearly differ from the dark mud-, silt- and sandstones with sandy bonebeds, dated by palynostratigraphy to lower, middle and upper Rhaetian in south-western Germany (Exter Formation; Etzold and Schweitzer 2005) and also in the Tabular and Folded Jura of northern Switzerland (Belchen Member of the Klettgau Formation in Canton Baselland and Solothurn; Jordan et al. 2016; Schneebeli-Hermann et al. 2018; Looser et al. 2018).

4 Systematic palaeontology

Dinosauria OWEN, 1842.

Sauropodomorpha HUENE, 1932.

Sauropodiformes SERENO 2007 (sensu McPhee et al. 2014).

Schleitheimia n. gen.

Type species. Schleitheimia schutzi sp. nov.

Etymology. Genus name refers to the type locality at Schleitheim, Canton Schaffhausen, Switzerland.

Diagnosis. As for type and only known species.

Schleitheimia schutzi sp. nov.

Etymology. Species epithet honours the collector of the type material, Emil Schutz (1916–1974).

Holotype. PIMUZ A/III 550, partial right ilium.

Referred material. Centrum of posterior cervical vertebra (PIMUZ A/III 538), anterior dorsal vertebra (PIMUZ A/III 540), centra of two mid-dorsal vertebrae (PIMUZ A/III 539 and 541), centrum of posterior dorsal vertebra (PIMUZ A/III 545), centrum of anterior caudal vertebra (PIMUZ A/III 548), two centra of posterior mid-caudal vertebrae (PIMUZ A/III 542, 543), posterior caudal vertebra (PIMUZ A/III 544; referral tentative), distal end of left humerus (PIMUZ A/III 549), pubic peduncle of left ilium (PIMUZ A/III 4390), possible pubic fragment (PIMUZ A/III 4398), partial left femur (PIMUZ A/III 551), ungual of right pedal digit I (PIMUZ A/III 547; referral tentative). Further tentatively referred specimens were collected considerably later and include three fragmentary dorsal vertebral centra (MzA NAT15051, NAT15052 and NAT15058), a sacral centrum (MzA NAT15050), three caudal vertebrae (MzA NAT15047, NAT15048, NAT15049), and a partial right humerus (MzA NAT15046). As discussed above, all of these remains come from the same general locality, are consistent in morphology, and probably represent the same taxon and at least partially the same individual as the holotype.

Type locality and horizon. The type locality is Santierge (Fig. 1), a hill situated 900 m south of the church of Schleitheim in the Swiss Canton Schaffhausen (47° 44′ 30″ N, 8° 29′ 13″ S). The material, collected in the Bratelen Bonebed (“Rhät-Bonebed”), was most probably derived from the uppermost part of the ‚Zanclodonmergel‘(= Knollenmergel), now called Gruhalde Member of the Klettgau Formation, uppermost Norian (Jordan et al. 2016).

Diagnosis. The new taxon can be diagnosed by the following autapomorphies: medial brevis shelf of ilium developed as dorsoventrally broad, rounded ridge just below the mid-height of the iliac blade on the medial side that ends in a large, round expansion at the posterior end of the ilium; fourth trochanter of the femur very robust and arises gradually out of the posterior surface of the bone at about its mid-width towards its apex at the posteromedial margin; crista tibiofibularis of the femur exceptionally broad and only very slightly offset medially from the lateral margin of the shaft, so that no posteriorly facing shelf is present lateral to the crista.

5 Description

5.1 Original material of Schutz

5.1.1 Axial skeleton

A total of nine vertebrae are present in the original material of Schutz, representing cervical, dorsal and caudal vertebrae. Five presacral vertebral centra are present, representing one posterior cervical and four dorsal elements, based on the absence/presence and the position of the parapophysis on the centrum. The specimen PIMUZ A/III 538 is the poorly preserved centrum of a posterior cervical vertebra (Fig. 3). Due to the rather poor preservation, its exact position in the vertebral column cannot be established, but, assuming that Schleitheimia had ten cervicals, as other non-sauropodan sauropodomorphs, it probably represents one of cervicals eight to ten. The centrum was rather short (ratio of centrum length to anterior centrum height approximately 1.3) and amphicoelous, as in other basal sauropodomorphs. The anterior articular surface is almost round, being very slightly wider than high; the posterior surface is largely broken. The centrum is strongly constricted between the articular ends, its minimal width (35 mm) being only 37% of the width of the anterior articular surface (94 mm). The parapophyses are placed at the anteroventral end of the centrum and are slightly offset posteriorly from the rim of the anterior articular end. They form lateroventral projections and have concave articular surfaces that are teardrop-shaped in outline, with the pointed end pointing posteriorly. Their ventral and dorsal surfaces are anteroposteriorly convex, unlike the recessed dorsal surface of the parapophyses in eusauropods. A stout, rounded edge extends posteriorly from the posterior end of the parapophysis and separates the lateral side of the centrum from its ventral side; this edge corresponds to the ventrolateral ridge of Wilson (2012). The ventral surface of the centrum forms two flat surfaces that converge medially towards a low, transversely rounded midline keel that becomes slightly more conspicuous anteriorly (Fig. 3f). At the anterior end, the ventral surfaces lateral to the keel are slightly concave between the latter and the projection of the parapophyses, but a marked depression, as it is present in some sauropods, is absent. A large, but shallow depression is present on the lateral side of the centrum.

Fig. 3
figure 3

Posterior cervical vertebra of Schleitheimia schutzi n. gen., n. sp., PIMUZ A/III 538. a, b left and right lateral views; c dorsal view; d anterior view; e posterior view; f ventral view. aas, anterior articular surface; na, neural arch; ld, lateral depression; nc, neural canal; pap, parapophysis; vk, ventral keel; vlr, ventrolateral ridge. Scale bar equals 5 cm

Not much can be said about the morphology of the neural arch, as it is mostly broken away. A small portion of the neurocentral suture is visible on the left side of the vertebra; the rest of suture cannot be made out, probably due to preservation. It separates the neural arch pedicle from the lateral side of the centrum and extends ventrally to approximately 1/3 of the centrum height anteriorly. Only the bases of the anterior and posterior centrodiapophyseal laminae are preserved. These laminae were obviously stout and extended obliquely towards the transverse process in the central part of the vertebra, the ventral end of the anterior centrodiapophyseal lamina being offset posteriorly from the anterior end of the neural arch pedicle. The neural canal is narrow and was obviously high, indicating a dorsoventrally high neural arch. It becomes narrower in its central part, where it is also deeply incised into the dorsal side of the centrum.

Specimen PIMUZ A/III 540 is a rather poorly preserved anterior dorsal vertebra, including parts of the neural arch and spine (Fig. 4). The centrum is amphicoelous, being more deeply concave posteriorly than anteriorly. In ventral view, it is strongly constricted, but the minimal width is reached approximately 1/3 of the length posterior to the anterior end; from this point the centrum strongly expands posteriorly. A rather sharply defined, but low midline keel extends anteriorly from the minimal width of the centrum. The posterior part of the ventral side is broad, with apparently a small, but poorly preserved midline ridge towards the posterior end and marked, but also poorly preserved lateroventral ridges on either side (Fig. 4d).

Fig. 4
figure 4

Anterior dorsal vertebra of Schleitheimia schutzi n. gen., n. sp., PIMUZ A/III 540. a, b left and right lateral views; c anterior view; d ventral view; e dorsal view. acdl, anterior centrodiapophyseal lamina; nc, neural canal; pap, prapophysis; pcdl, posterior centrodiapophyseal lamina; podl, postzygapophyseal diapophyseal lamina; prdl, prezygodiapophyseal lamina; psf, prespinal fossa; spdl, spinodiapophyseal lamina; vk, ventral keel; vlr, ventrolateral ridge. Scale bar equals 5 cm

The lateral side of the centrum is poorly preserved. The parapophysis is placed at about the half height of the centrum. It is relatively small, oval in outline, and notably displaced posteriorly from the anterior end, its posterior rim lying at approximately one-third of the length of the centrum. The anterior rim of the parapophysis is connected to the rim of the anterior articular surface by a low, rounded ridge. The articular surface of the parapophysis faces posterolateroventrally. A deep and marked centrodiapophyseal fossa is present posterodorsal to the parapophysis, but there is no pleurocoel posterior or posterodorsal to the parapophysis, nor is the dorsal part of the centrodiapophyseal fossa deepened, as it is the case in some basal sauropods (e.g. Bonaparte 1986). The neural arch is low, the height from the centrum to the dorsal surface of the transverse process being approximately two-thirds of the height of the centrum. The base of the broken transverse process is placed slightly anterior to the mid-length of the centrum on the neural arch. It is connected to the centrum by relatively short and stout anterior and posterior centrodiapophyseal laminae that meet at an angle of slightly less than 90°. The anterior centrodiapophyseal lamina is slightly more steeply inclined than the posterior centrodiapophyseal lamina and the ventral bases of both lamina are notably offset from the respective rim of the centrum. Short, but robust prezygodiapophyseal and postzygodiapophyseal laminae extend from the transverse process anteriorly and posterodorsally, respectively, but the zygapophyses are missing. This well-developed neural arch lamination results in the presence of large prezygapophyseal-centrodiapophyseal, centrodiapophyseal and postzygapophyseal-centrodiapophyseal fossae, of which the latter two are slightly larger and deeper than the former. On the right side of the neural arch, the postzygodiapophyseal lamina is partially complete and shows that this lamina formed a laterally extensive and stout roof over the postzygapophyseal-centrodiapophyseal fossa. The slightly dorsally protruding stalks for the prezygapophyses diverge slightly anteriorly and define a wide and deep prespinal fossa. The roof of the neural arch ascends towards the missing postzygapophyses posteriorly. The neural spine was anteroposteriorly short, placed approximately above the mid-length of the centrum and robust. Anteriorly, a broad, roughened surface for the attachment of the interspinal ligaments is present. The neural spine expands transversely towards its posterior end and was obviously connected to the postzygapophyses by stout spinodiapophyseal laminae that define a large postspinal fossa, although this region is poorly preserved. The dorsal part of the neural spine is missing, so nothing can be said about its height. In anterior view, the spine expands slightly and gradually dorsally. As in the cervical vertebra, the neural canal is narrow, round in outline anteriorly and deeply incised into the dorsal side of the centrum in its central part.

PIMUZ A/III 539 (Fig. 5a–d) and 541 (Fig. 5e, f) are mid-dorsal vertebral centra. The centra are amphicoelous, with slightly more deeply concave anterior than posterior articular surfaces. The centra are only moderately constricted between the articular ends and the ventral sides are broadly transversely rounded. A notable elongate lateral depression is present on the dorsal part of the lateral surface on either side, but these depressions have no sharply defined rims and thus cannot be considered to be true pleurocoels (sensu Carballido and Sander 2014). As in the anterior dorsal, the base of the broken posterior centrodiapophyseal lamina is very stout and the neural canal is narrow, high and deeply incised into the dorsal side of the centrum.

Fig. 5
figure 5

Mid and posterior dorsal vertebrae of Schleitheimia schutzi n. gen., n. sp. ad Mid dorsal vertebral centrum, PIMUZ A/III 539, in right (a) and left (b) lateral, anterior (c), and ventral (d) views; e, f mid dorsal vertebral centrum, PIMUZ A/III 541, in lateral (e) and posterior (f) views; gi posterior dorsal vertebral centrum, PIMUZ A/III 545, in lateral (g), dorsal (h) and ventral (i) views. ld, lateral depression; nc, neural canal; pas, posterior articular surface; pcdl, posterior centrdiapophyseal lamina. Scale bar is 5 cm

Specimen PIMUZ A/III 545 is a posterior dorsal centrum, probably of one of the most posterior dorsals (Fig. 5g–i). The centrum is notably short (ratio of length to posterior width about 0.8) and massive, being broad and rounded ventrally. The centrum is amphicoelous, with a more deeply concave posterior than anterior side. As in the mid-dorsal centra, a marked lateral depression is present in the dorsal half of the lateral side; this depression is somewhat smaller, but more clearly defined than in the mid-dorsal vertebrae, without, however, having sharply defined borders. The base of the broken posterior centrodiapophyseal lamina is massive. The neural canal is relatively wider than in the mid-dorsal vertebrae, but is very deeply and abruptly incised into the dorsal side of the centrum, its deepest part being placed more than 30 mm below the rim of the articular surfaces.

A large and strongly distorted anterior caudal vertebral centrum without precise locality information (PIMUZ A/III 548; Fig. 6) fits in size with the posterior dorsal vertebra and thus might also represent the same animal. The centrum is amphicoelous, being more strongly concave anteriorly than posteriorly. It is notably short, its anteroposterior length (c. 90 mm) being only about 60% of its anterior height (c. 150 mm), although both of these measurements should be seen with caution due to the distortion. The ventral rim of both the anterior and posterior articular surface flexes slightly ventrally. The centrum is constricted in the middle, and there seems to have been a broad, flattened to very slightly transversely concave surface on the ventral side, ending in a short groove posteriorly between the chevron facets. The lateral side of the centrum is smooth and does not show any notable depression below the transverse processs. The base of the broken transverse process is placed on the neurocentral suture. It is massive and extends over almost the entire length of the centrum. Anteriorly, the base of the process is slightly higher than posteriorly, and a short, stout ridge connects its anteroventral edge with the anterodorsal end of the centrum. The neural canal is narrow and somewhat incised into the dorsal surface of the centrum, but most of the neural arch is missing.

Fig. 6
figure 6

Anterior caudal vertebra of Schleitheimia schutzi n. gen., n. sp., PIMUZ A/III 538. a, b right and left lateral view; c ventral view; d anterior view; e posterior view; f dorsal view. Abbreviations: aas, anterior articular surface; cf, chevron facet; na, neural arch; nc, neural canal; pas, posterior articular surface; tp, transverse process. Scale bar equals 5 cm

Three posterior mid- to distal caudals are present in the collections of the PIMUZ (Fig. 7). While two of them can positively identified as coming from the locality of Schleitheim (PIMUZ A/III 542 and 543; Fig. 7a–d), the provenance of the third vertebra (PIMUZ A/III 544; Fig. 7e, f) is uncertain. However, its preservation is consistent with the other material from this locality, and we tentatively refer it to the same animal. All of them are poorly preserved and miss most of the neural arch. The caudal centra are amphicoelous and rather massive. They are rounded ventrally and do not show any ventral groove or ridge. The articular ends are only complete in the smallest vertebra (PIMUZ A/III 544; Fig. 7e, f) and show no signs of chevron facets. No transverse process is present in any of the elements, although it cannot be ruled out that this process was present on the missing neural arch of the most anterior specimen, PIMUZ A/III 542. The specimen PIMUZ A/III 543 has a dorsoventrally somewhat flattened centrum and a stout longitudinal ridge on the lateral side, resulting in a longitudinal depression on this side between the ridge and the attachment of the neural arch (Fig. 7d). PIMUZ A/III 544 has parts of the neural arch preserved. The pedicles of the arch do not extend over the entire length of the centrum, but are offset from the posterior end. The neural arch is rather low, with a transversely rounded dorsal roof anterior to the broken neural spine. The prezygapophyses obviously overhung the centrum anteriorly, but are broken away. The neural canal is round in outline. Measurements of the axial elements can be found in Table 2.

Fig. 7
figure 7

Middle and distal caudal vertebrae of Schleitheimia schutzi n. gen., n. sp. ac Middle caudal vertebral centrum, PIMUZ A/III 542, in right lateral (a), dorsal (b) and anterior (c) views; d posterior mid-caudal vertebra, PIMUZ A/III 543, in left lateral view; e, f distal caudal vertebra, PIMUZ A/III 544 in left lateral (e) and anterior (f) views. nc, neural canal. Scale bar equals 5 cm

Table 2 Measurements of vertebrae of the original Schutz excavation; probably belonging to type individual of Schleitheimia

5.1.2 Appendicular skeleton

Appendicular elements preserved include a partial humerus, ilium, a pubis fragment, a partial femur, and a pedal ungual. The only element of the forelimb recovered is the distal third or fourth of a large and massive left humerus (PIMUZ A/III 549; Fig. 8). The other element mentioned and figured by Galton (1986: 175; pl. 1, Fig. 23) as the proximal part of the right ulna is the pubic peduncle of the right ilium (see below). The distal end of the humerus is notably expanded, from a minimal transverse width of the shaft at the proximal break of 92 mm to a maximal distal width of c. 175 mm. The shaft is anteroposteriorly flattened, with a maximal anteroposterior depth of c. 46 mm at the proximal break. The posterior side of the bone is occupied by a large, shallow depression, as in most basal saurischians. On the anterior side, a large, rounded and rather deep flexor fossa is present towards the distal end between the distal condyles. The fossa is well defined proximally by stout, distally diverging, broadly rounded ridges. On the lateral side of the lateral of these ridges, the side of the bone forms a flat, anterolaterally facing surface that meets the slightly curved posterolateral side in a well-defined ridge at about the anteroposterior mid-width of the lateral side. This lateral ridge becomes less conspicuous towards the proximal break, but is well-marked on the lateral side of the distal condyles. The anteromedial surface is less steeply inclined and gradually curves into the posterior side on the posterior edge of the medial side of the bone.

Fig. 8
figure 8

Distal end of left humerus of Schleitheimia schutzi n. gen., n. sp., PIMUZ A/III 549. a anterior view; b lateral view; c posterior view; d medial view; e distal view; f, proximal view of proximal break. dp, posterior depression; ff, flexor fossa; lr, lateral ridge; rc, radial condyle; uc, ulnar condyle. Scale bar equals 5 cm

The distal articular surface is more or less hourglass-shaped in distal view (Fig. 8e). The radial condyle is slightly more massive and more strongly expanded anteriorly than the ulnar condyle. Both condyles are well separated by anterior and posterior indentations, but more or less continuous in anterior or posterior view distally. The anteromedial edge of the ulnar condyle is broken, but the condyle seems to have curved gradually proximomedially on the medial side, unlike in many basal sauropodomorphs, where there is a marked, mediodistally inclined flat area on the medial side of the ulnar condyle. The distal surface is not smoothly convex, but has several marked pits and grooves. One groove traverses the distal side of the radial condyle obliquely from anterolateral to posteromedial; in its medial part, this groove opens anteriorly onto a large, mediolaterally concave facet that separates the humeral condyles on the anterodistal side. At least two oblique grooves are also present on the ulnar condyle and extend from anteromedial posterolaterally.

A good part of the right ilium was preserved in numerous fragments (PIMUZ A/III 550; Fig. 9a–f). Several of these fit together to form the entire acetabular margin of the ilium and the iliac peduncles. Other fragments represent much of the postacetabular blade and the dorsal margin of the ilium, which is here designated as the holotype of Schleitheimia schutzi gen. et sp. nov.

Fig. 9
figure 9

af Partial right ilium PIMUZ A/III 550, holotype of Schleitheimia schutzi n. gen., n. sp., and g distal end of left pubic peduncle PIMUZ A/III 4390. a dorsal view of preserved parts of iliac blade; b preserved parts in approximate original configuration in lateral view; c postacetabular process in medial view; d ischial peduncle in distal view; e acetabular region in ventral view; f pubic peduncle in distal view; g left pubic peduncle in distal view PIMUZ A/III 4390. ac, acetabulum; ip, ischial peduncle; mbs, medial brevis shelf; pap, postacetabular process; pp, pubic peduncle. Scale bar equals 5 cm

As in all sauropodomorphs, the pubic peduncle is considerably longer than the ischial peduncle. Whereas the expansion of the latter from the base of the postacetabular process is about 65 mm, the pubic peduncle expands for approximately 210 mm from the base of the preacetabular process. The pubic peduncle is almost straight, and its lateral surface slightly and gradually expands distally. The acetabular rim of the pubic peduncle is notably concave transversely, although this is somewhat exaggerated by compression. The lateral surface is flat proximally but becomes slightly anteroposteriorly convex distally. The anterior margin of the peduncle is much more narrow than the acetabular rim and rounded transversely, whereas the medial surface faces slightly anteromedially and is flattened. The distal articular surface for the pubis is comma-shaped in outline, tapering posteromedially. It is flat to very slightly convex and has a roughened, pitted surface. A stout supraacetabular crest was obviously present, but is only preserved in its dorsal part. The broken base of the crest starts on the lateral acetabular margin at about one-third of the length of the pubic peduncle from the distal end of the latter. The crest seems to have had its greatest extension at the anterodorsal part of the acetabulum, where it overhangs the latter, forming a markedly ventrally concave hood. The crest ends slightly posterior to the mid-length of the acetabulum and does not extend onto the base of the ischial peduncle, although the rim of the acetabulum protrudes slightly laterally almost to the distal end of this peduncle.

The acetabular rim on the ischial peduncle is slightly wider transversely than on the pubic peduncle, and it is slightly convex transversely. The lateral surface of the peduncle is slightly concave anteroposteriorly between the raised acetabular rim and the base of the postacetabular process, but becomes convex towards the distal end. The distal end of the ischial peduncle is considerably wider transversely than long anteroposteriorly and has a strongly anteroposteriorly convex distal articular surface for the ischium. As in the pubic peduncle, this articular surface is rugosely pitted. The distal end of the ischial peduncle is slightly expanded posteriorly, resulting in a dorsoventrally concave posterior margin of the peduncle. The ischial peduncle seems to have been especially short in respect to the level of the ventral margin of the postacetabular blade: whereas the latter is placed above the level of the dorsal rim of the acetabulum in most non-sauropodan sauropodomorphs (e.g. Galton and Upchurch 2004), it is at this level or below in Schleitheimia, as in sauropods (e.g. Bonaparte 1986). Although the direct contact between the ischial peduncle and postacetabular blade is not preserved in PIMUZ A/III 550, any arrangement that places the ventral rim of the blade above the level would result in an anteroventrally sloping dorsal iliac margin, which would be highly unusual.

The base of the broken preacetabular process is transversely widened to form a ventrally facing shelf, whereas the dorsal part of the process forms a thin bony lamina that is dorsoventrally convex laterally. A large, anteroventrally facing nutrient foramen is present proximally in the lateral side of the ventrally facing shelf. The base of the postacetabular process faces slightly lateroposteriorly, and the lateral surface of the proximal part of this process was obviously slightly concave anteroposteriorly.

The posterior end of the postacetabular process forms a large, lobe-shaped expansion. Its ventral margin is anteroposteriorly concave and meets the posterior margin in a sharp angle of c. 60°. The posterior margin is dorsoventrally notably convex, but the transition into the dorsal margin posterodorsally is marked by a short, slightly concave edge. Anterior to this, the dorsal margin is slightly undulating, with a low, but notable, rounded dorsal expansion towards the supraacetabular region. The lateral surface of the posterior end of the postacetabular blade is markedly convex dorsoventrally. More anteriorly, the dorsal two-thirds of the lateral surface of the iliac blade become slightly dorsoventrally concave. The posterior end is strongly thickened transversely, and the posterior surface of this thickened region is strongly rugose, with the rugosities forming a laterally protruding margin in the posterodorsal part. Dorsally, the dorsal part of the postacetabular blade forms a broad, dorsally and slightly laterally facing surface, which becomes gradually narrower anteriorly and has a slightly rugose texture. In the anteriormost preserved part of the dorsal rim, this surface is still slightly rugose, but not markedly thicker than the iliac blade, the thickness of which decreases from posterior towards the anterior break.

The medial side of the postacetabular process is poorly preserved, but a stout, but rather low medial brevis shelf is clearly visible and extends posteriorly some one-third of the height of the process from the ventral margin and approxmately parallel to the latter. The shelf becomes dorsoventrally wider and more marked towards the posterior margin, where it forms a notable semicircular medial expansion of the posterior surface.

Only the distal end of the pubic peduncle of the left ilium is present (PIMUZ A/III 4390; Fig. 9g). It corresponds to the pubic peduncle of the right ilium in size and shape, but is slightly more massive mediolaterally, confirming the assumption that the latter has suffered from compression.

A poorly preserved bone fragment might represent the distal end of the right pubis (PIMUZ A/III 4389). The bone is anteroposteriorly thickened laterally and becomes gradually more slender medially, indicating that the pubis apex was slightly thickened, as in many large basal sauropodomorphs.

Portions of the left femur are preserved in two parts (PIMUZ A/III 551a and b; Fig. 10). A small piece of the posteromedial side of the shaft preserves the fourth trochanter (Fig. 10a, b). The latter is developed as a large posteromedial expansion. In medial view, it is more or less symmetrical in outline, with sloping proximal and distal margins and a straight posterior margin of the central part. This is unlike the fourth trochanter in many basal sauropodomorphs, which is asymmetrical and shows a marked posterodistal angle. It is notably thick in posterior view, with approximately the medial width of the shaft gradually rising towards the apex of the trochanter, which is placed at the posteromedial edge. Thus, the lateral side of the trochanter is convex in both mediolateral and proximodistal direction. In contrast, the medial side is flat to very slightly proximodistally concave. However, a deep groove or rugose pit for the insertion of the musculus caudofemorlis longus, as it is present in many sauropods, is absent; the medial side of the femoral shaft is smooth and slightly convex anteroposteriorly.

Fig. 10
figure 10

Partial left femur of Schleitheimia schutzi n. gen., n. sp., PIMUZ A/III 551. a, b Fragment of the mid-shaft in posterior (a) and medial (b) view; cg distal end in lateral (c), posterior (d), medial (e), and distal (f) views, and proximal view of proximal break (g). Abbreviations: IV, fourth trochanter; fc, fibular condyle; tc, tibial condyle. Scale bar equals 5 cm

The other part of the femur represents the distal end (Fig. 10c–g). The preserved portion is almost completely straight, with only the proximal part of the preserved shaft showing a very weak curvature. At the proximal break, the shaft is oval in outline and anteroposteriorly flattened, its transverse width (117 mm) being more than 130% of its anteroposterior depth (c. 88 mm). Distally, the bone considerably but gradually expands to a maximal distal width of 227 mm. The anterior side of the shaft and also the distal end is damaged, but there was obviously a shallow longitudinal depression in the central part of the anterior side, slightly displaced medially, which leads to a broad but very shallow extensor groove at the distal end. Lateral and medial to the groove, the anterior side curves gradually into the lateral and medial side, respectively. The posterior condyles are massive and separated by a wide, deep, U-shaped incision. A small posteriorly directed tubercle is present within this intercondylar groove towards the distal end. The intercondylar groove continues a short way proximal from the condyles onto the posterior side of the shaft, where it becomes less deep and wider. The condyles are subequal in transverse width, but the tibial condyle extends slightly further posteriorly than the crista tibiofibularis. In distal view, the posterolateral margin of the tibial condyle is rounded, whereas posteromedially, the posterior margin forms an almost right angle with the medial margin. The massive lateral condyle has a flattened posterior side that faces slightly posteromedially. In distal view, the posterolateral corner of the condyle forms a slightly sharp angle, so that the condyle overhangs a shallow longitudinal depression on the lateral side of the bone. However, in contrast to most other saurischians, the lateral condyle is not offset medially from the lateral side of the shaft, and a posterolaterally facing shelf lateral to the condyle is absent. Proximally, the flattened posteromedial surface of the condyle is offset from the shaft by a notable step.

The distal surface of the tibial condyle is gently rounded anteroposteriorly, whereas the distal surface of the crista tibiofibularis is flat. While the distal surface of the tibial condyle is continuous with the distal articular surface of the femur, that of the crista tibiofibulris is offset from the anteroposteriorly slightly convex anterior part of the distal articular surface by a shallow transverse indentation. The distal articular surface is covered by irregularly arranged pits and grooves, as in sauropods.

A small ungual (PIMUZ A/III 547; Fig. 11) is present, but it is somewhat uncertain if this element comes from the same locality or might have been found during an excavation of the “Rhaetic bonebed” at Hallau (see Peyer 1943a, b). However, its preservation is consistent with the other material from Schleitheim, whereas other bones from Hallau, including one other sauropodomorph ungual, are usually darker. Thus, we assume that this ungual also comes from the former locality and represents the same animal as the other remains.

Fig. 11
figure 11

Pedal ungual tentatively referred to Schleitheimia schutzi n. gen., n. sp., PIMUZ A/III 547. a lateral view; b dorsal view; c anterior view. Scale bar equals 1 cm

In comparison with unguals of Antetonitrus (McPhee et al. 2014) and Lessemsaurus (Pol and Powell 2007a), this element represents the ungual of the first pedal digit, and it closely resembles the same element in these two taxa. It is dorsoventrally flattened, only little recurved and strongly asymmetrical. The proximal articular end is missing. The ventral side is triangular in outline and flattened, being only very slightly convex transversely. On one side it forms a sharp angle towards the lateral or medial side of the bone, and the edge separating the two sides is offset ventrally from the claw groove. On the other side, the ventral side much more gradually curves into the side of the ungual, and the claw groove is placed directly dorsal to this curve. The dorsal side of the ungual is broad and transversely rounded.

5.2 Tentatively referred material from the MzA Schaffhausen

5.2.1 Vertebrae

Seven fragmentary to partial vertebrae from the locality Schleitheim-Santierge are present in the MzA. Three of these vertebrae represent dorsal vertebrae, one seems to be a sacral vertebra and three elements belong to the caudal series. Measurements of the elements can be found in Table 3.

Table 3 Measurements of vertebral remains from Schleitheim Santierge held in the MzA, tentatively referred to Schleitheimia

MzA NAT15051 is a dorsal vertebra, possibly one of the anteriormost dorsals. Only the poorly preserved centrum and the basalmost parts of the neural arch pedicles are preserved. The centrum is short and high, its better preserved posterior articular surface being higher than the length of the centrum. The anterior end is largely missing, and the remains are poorly preserved, so that nothing can be said about the possible presence and position of a parapophysis on the centrum. In ventral view, the centrum is strongly waisted and narrow in its central part, with the ventral side forming a narrow, rounded keel. As in the dorsal vertebrae described above, a broad, poorly defined depression is present on the lateral side of the centrum. Of the neural arch, only the basal part of a stout anterior centrodiapophyseal lamina is preserved. This lamina is placed at the anterior end of the centrum and steep, whereas the broken base of the less steeply inclined posterior centrodiapophyseal lamina is slightly offset from the posterior end of the centrum. As in the vertebrae described above, the neural canal is deeply incised into the dorsal side of the vertebral centrum and widens dorsally.

The other two dorsal vertebrae are too poorly preserved to yield much useful information. MzA NAT15052 seems to be generally similar to MzA NAT15051 in that the centrum is short and waisted, being narrow in its central part. MzA NAT15058, the most recently found specimen (in April 2016), seems to be a poorly preserved more posterior dorsal, with a broad, ventrally broadly rounded centrum. Both of these vertebrae share the character of a deeply incised neural canal with the dorsal vertebrae of Schleitheimia and MzA NAT15051.

The specimen MzA NAT15050 is a large, deformed and strongly abraded vertebral centrum of presumably the last sacral vertebra. The centrum is massive and shorter than high, with the posterior articular surface being oval, higher than wide, and only slightly concave. The attachments of the transverse process are massive and extend from the dorsal part of the centrum anteriorly over the entire base of the neural arch. The neural canal is widened in its central part, but narrows posteriorly. At about mid-length of the centrum, a narrow, deep groove incises into the dorsal surface of the centrum from the neural arch.

MzA NAT15049 is the poorly preserved centrum of an anterior caudal vertebra. The centrum is massive, shorter than high and amphicoelous, with the anterior articular surface being more deeply concave than the posterior surface, as is often the case in saurischians. The centrum is broadly rounded ventrally, without any ventral keel or groove, and the lateral sides are convex dorsoventrally and lack the lateral depression seen in the dorsal vertebrae. The massive attachment of the transverse process is placed on the posterior part of the neurocentral suture. The neural canal is narrow, but not incised into the dorsal surface of the centrum.

The specimen MzA NAT15047 (Fig. 12a–c) represents a mid-caudal vertebra and is the best preserved vertebral specimen from Schleitheim–Santierge in the collections of the MzA, preserving the entire centrum and the neural arch, but lacking transverse processes, zygapophyses and the neural spine. The centrum is massive and longer than high, with the articular surfaces being subcircular in outline. The articular surfaces are markedly amphicoelous, being considerably concave both anteriorly and posteriorly, both with a slight protuberance just above mid-height. In lateral view, the anterior articular surface is slightly angled anteroventrally, similar to the situation seen in the proximal caudals of a specimen of Plateosaurus from Bavaria (Wellnhofer 1993; Moser 2003). The ventral margins of the articular surfaces are flexed ventrally to form the facets for the haemapophyses. Whereas the anterior margin forms a single, undivided and only moderately developed anteroventral facet, the posterior facet is clearly subdivided into two, posteroventrally facing facets. The ventral surface of the centrum is broad and flattened, with two low edges extending from the posterior chevron facets anteriorly and defining a very shallow longitudinal depression on the ventral surface.

Fig. 12
figure 12

Material from the locality Schleitheim-Santierge in the MzA, tentatively referred to Schleitheimia schutzi n. gen., n. sp. a-c Mid-caudal vertebra, MzA NAT15047, in right lateral (a), ventral (b) and posterior (c) view; d posterior mid-caudal vertebra, MzA NAT15048, in left lateral view; e, f partial right humerus, MzA NAT15046, in anterior (e) and lateral (f) view. af, anterior fossa; dpc, deltopectoral crest; ns, neural spine; tp, transverse process; vg, ventral groove. Scale bars equal 10 cm

The neural arch extends over most of the centrum and is only slightly more displaced from the posterior rim of the centrum than from its anterior rim. Only the broken attachment of the transverse process is present; it extends from the stalk of the prezygapophysis over almost the entire length of the neural canal. The roof of the neural canal adjacent to the base of the neural spine is anteroposteriorly concave. The neural canal is oval in outline and wider than high. The transversely narrow base of the neural spine is placed more over the posterior part of the centrum, but largely broken away. Anteriorly, weakly developed ridges represent the spinoprezygapophyseal laminae and define a very shallow, anteriorly widening prespinal fossa.

The caudal vertebra MzA NAT15048 (Fig. 12d) represents a posterior mid-caudal. Its centrum is generally similar to that of MzA NAT15047, but more slender, being slightly higher than wide. In the neural arch, the transverse process is placed on the posterior end of the neurocentral suture and anteroposteriorly short, but connected to the broken stalks of the prezygapophysis by a broad, stout prezygodiapophyseal lamina, as it was most probably also present in the vertebra described above. As in the former, this lamina is slightly curved, resulting in a similar, anteroposteriorly concave depression adjacent to the base of the neural spine. The base of the broken neural spine is placed slightly more posteriorly than in the vertebra described above, and there are no spinoprezygapophyseal laminae, nor a prespinal fossa.

5.2.2 Humerus

The right humerus, MzA NAT15046 is almost complete, but misses the proximal end and the distal condyles are damaged, especially the lateral condyle (Fig. 12e, f). As preserved, the humerus is 380 mm long, and, based on the position of the distal end of the deltopectoral crest, which ends 240 mm above the distal end, its total length can be estimated to be between 450 and 500 mm. As preserved the distal end is c. 145 mm wide, with 30-40 mm missing, and the bone is thus of closely matching size as the distal end of the left humerus referred to Schleitheimia and described above.

The shaft of the humerus is stout, and whereas the distal half is more or less straight in medial view, the proximal end curves posteriorly, so that the proximal half of the bone is posteriorly concave. The deltopectoral crest is well-developed, placed on the anterolateral edge of the proximal shaft and directed anteriorly, but its proximal parts and its distal extremity are broken off. Distally, the crest seems to be sharply offset from the shaft at an approximately right angle, with a marked, flat area anterolaterally just distal to it. The minimal width of the shaft, just distal to this area and c. 200 mm from the distal end, is 68 mm; at this level, the shaft is c. 62 mm deep. The minimal depth of c. 48 mm is reached just at the base of the distal transverse expansion of the bone, some 130 mm proximal to the distal end. The cross-section of the shaft distal to the deltopectoral crest is ovoid, with a broader, almost laterally flattened lateral side, and a pointed medial side. Distally, the bone is considerably expanded transversely and has stout medial and lateral condyles, although the lateral condyle is largely broken off. As in the humerus of Schleitheimia, the posterior side shows a large, shallow, triangular depression, whereas there is a smaller, but deeper and well-defined fossa between the distal condyles on the anterior side of the bone. This latter fossa has well-defined medial and proximomedial margins, but fades more gradually laterally. Distally it becomes more shallow towards a narrow, but well-defined intercondylar groove.

5.3 Other sauropodomorph material from Canton Schaffhausen

5.3.1 Sauropodomorph astragalus of Schutz’ excavation at Santierge

The material collected in situ by Schutz includes an isolated right astragalus (PIMUZ A/III 4391; Fig. 13), which closely matches the astragalus of Plateosaurus specimen SMNS 13200 in size (Huene 1926), and is thus too small to belong to the same individual as the type and referred material of Schleitheimia, in which comparable measurements of the ilium and femur, for example, are approximately 150% of those of this specimen of Plateosaurus.

Fig. 13
figure 13

Right astragalus of Plateosaurus sp. from Schleitheim-Santierge, PIMUZ A/III 4391. a Anterior view; b posterior view; c proximal view; d lateral view. asp, ascending process. Scale bar equals 10 cm

The astragalus is considerably broader transversely (c. 15 cm) than deep anteroposteriorly (max. c. 7.8 cm). The body of the astragalus was placed entirely below the tibia, as indicated by its proximal articular surface, and is c. 5 cm thick proximodistally. In proximal view, the anterior margin is very gently concave, almost straight, whereas the posterior margin is convex and flexes anteriorly towards its medial end. Thus, whereas the lateral margin is straight, the medial margin is strongly convex posteriorly; its anteromedial edge is damaged. The ascending process is placed anteriorly on the lateral two-thirds of the astragalar body and gradually ascends laterally to a moderate height of maximally c. 2 cm. The posterior margin of the anteroposteriorly broad ascending process separates an anterior facet from the medially flat to slightly concave proximal articular surface for the tibia. With increasing height of the ascendings process, this facet faces gradually more anteriorly than proximally towards the lateral side, until it forms an anteroproximally inclined facet that stands at an angle of 50°–60° towards the main articular facet for the tibia. The articular surface for the tibia posterior to the ascending process is slightly concave anteroposteriorly, with only a slightly raised posteromedial margin. The proximal edge of the lateral rim of the astragalus slightly overhangs the facet for the calcaneum so that the latter is slightly concave proximodistally. The distal articular surface is anteroposteriorly convex, though with a notable depression on the anterodistal surface. There are several large pits or foramina on the anterodistal surface, most notably directly below the maximal expansion of the ascending process.

This astragalus very closely resembles the astragalus of Plateosaurus (SMNS 13200) in size and shape. Especially the subequal anteroposterior breadth throughout its mediolateral width argues for a referral to this taxon, as the medial side is anteroposteriorly expanded in many other taxa (e.g. Langer et al. 2003; Martínez 2009; Apaldetti et al. 2013). Thus, we tentatively identify this astragalus as Plateosaurus sp.

5.3.2 Material resulting from new excavation at Santierge

The excavation at Santierge led by one of us (HF) in 2016 resulted in the recovery of numerous vertebrate remains, including remains of six dorsal vertebrae, four caudal vertebrae, a dorsal rib, a gastral rib, and a metacarpal of sauropodomorphs. Although it cannot be excluded that at least some of these elements might represent Schleitheimia and could even be derived from the same individual as the holotype (e.g. the metacarpal, which would fit in size with the remains referred to that taxon above), the remains represent animals of different sizes, and thus any referral would be tentative at best. This material can currently only be regarded as Sauropodomorpha indet. and is described here briefly. Measurements of the vertebrae recovred can be found in Table 4.

Table 4 Measurements of vertebrae recovered in a recent excavation at Schleitheim Santierge

Dorsal vertebrae Whereas two dorsal vertebrae (MzA NAT15059 and 15104) are only represented by their neural arches and one (MzA NAT15058) by a partial centrum, the other elements (MzA NAT15090, 15095 and 15100) preserve the centrum and at least parts of the neural arch and spine. However, many of these elements are also moderately to strongly deformed, making detailed descriptions difficult.

MzA NAT15104 is a relatively small, strongly anteroposteriorly compressed anterior dorsal neural arch. The relatively short transverse processes are directed laterodorsally and supported ventrally by a stout posterior centrodiapophyseal lamina, whereas the anterior centrodiapophyseal lamina is only indicated by a slight swelling at the anterior rim of the transverse process. Pre- and postzygodiapophyseal lamina are well developed, as is the centroprezygapophyseal lamina. The neural spine is anteroposteriorly short, slightly lower than the height of the neural arch and notably expanded transversely dorsally. The spinoprezygapophyseal laminae are very short, almost absent, whereas the spinopostzygapophyseal laminae strongly diverge towards the postzygapophyses. An incipient hyposphene is present between the postzygapophyses.

MzA NAT15059 is a poorly preserved partial anterior dorsal neural arch (Fig. 14a–c) that was found on the surface close to the excavated area. The neural spine, distal ends of the transverse processes and the posterior end of the neural arch are missing. The presence of a large, high oval parapophysis on the anteroventral end of the neural arch identifies this element as an anterior dorsal. The prezygapophysis is large, approximately as wide as long and flexed ventrally medially to form a hypantrum. Posteriorly, the incision between the zygapophyses widens to form a rounded dorsal opening onto the neural canal in front of the prespinal fossa, as in the theropod Condorraptor (Rauhut 2005). The lateral neural arch lamination is well developed, with an almost vertical posterior centrodiapophyseal lamina, a robust prezygodiapophyseal lamina and an almost horizontal paradiapophyseal lamina, which is almost parallel to the prezgodiapophyseal lamina and meets the posterior centrodiapophyseal lamina below the junction of the transverse process and the prezygodiapophyseal lamina. The laminae define deep prezygodiapophyseal and centrodiapophyseal fossae. The neural spine was obviously anteroposteriorly short and slightly thickened transversely.

Fig. 14
figure 14

Sauropodomorph vertebrae resulting from the recent excavation at Schleitheim-Santierge. ac Anterior dorsal neural arch, MzA NAT15059, in posterior (a), left lateral (b) and dorsal (c) view; d, e mid-dorsal vertebra, MzA NAT15090, in left lateral (d) and posterior (e) view; f mid-dorsal vertebra, MzA NAT15095, in right lateral view; g anterior caudal vertebral centrum, MzA NAT15091, in right lateral view; hj distal caudal vertebra, MzA NAT15097, in right lateral (h), posterior (i) and dorsal (j) view. cf, chevron facet; ex, prespinal expansion of intraprezygapophyseal slit; hy, hyposphene; ns, neural spine; pap, parapophysis; pcdl, posterior centrodiapophyseal lamina; podl, postzygodiapophyseal lamina; poz, postzygapophysis; ppdl, paradiapophyseal lamina; prdl, prezygodiapophyseal lamina; prz, prezygapophysis; spol, spinopostzygapophyseal lamina; sprl, spinoprezygapophyseal lamina; tp, transverse process; tprl, intraprezygapophyseal lamina. Scale bars equal 10 cm

The specimen MzA NAT15090 is a strongly deformed middle dorsal vertebra (Fig. 14d, e). The vertebral body is amphi- to platycoelous, elongate, higher than wide and strongly constricted. The ventral side is rounded and a shallow depression is present on the lateral side. The neural arch reaches approximately two-thirds of the height of the centrum. The parapophysis is placed on the anterior end of the neural arch; it is high oval in outline and relatively large. The neural arch lamination is similar to that seen in MzA NAT15059, with a vertical pcdl that does not reach the centrum, and parallel prdl and ppdl. A stout podl connects the transverse process with the lateral margin of the postzygapophysis. The prezygapophysis is relatively smaller than in MzA NAT15059, only very slightly medially inclined and forms a well-developed hypantrum medially; as in the specimen described above, the interprezygapophyseal slit widens slightly in front of the neural spine. The postzygapophyses overhang the centrum posteriorly. They are narrowly placed, elongate oval in outline and almost horizontal. A well-developed, ventrally widening hyposphene is present medioventral to them. The neural spine is broken off; it extended over the posterior two-thirds of the neural arch, was almost as long as the centrum, and plate-like. The sprl are short and do not reach the rim of the prezygapophyses, whereas the also short, but stout spol define a narrow, but deep postspinal fossa.

The specimen MzA NAT15095 is a strongly elongated, considerably compressed and thus poorly preserved dorsal vertebra (Fig. 14f). The vertebral centrum is considerably longer (13.5 cm) than high (9.8 cm anteriorly) and slightly flattened ventrally. The parapophysis is placed on the anteroventral end of the neural arch. The prezygapophysis is elongate oval in shape and overhangs the centrum anteriorly. It is connected with the transverse process by a slender prezygodiapophyseal lamina, but the paraprezygapophyseal lamina is only indicated by a broad swelling, and nothing can be said about the possible presence of a paradiapophyseal lamina. The transverse process is placed over the posterior half of the centrum and is directed posterolaterally and slightly dorsally. It is supported ventrally by a stout posterior centrodiapophyseal lamina.

Specimen MzA NAT15100 is an also strongly compressed, large dorsal vertebra with partially preserved neural arch. The vertebral centrum was relatively short and high and strongly constricted between the articular ends. The neural canal is slightly incised into the centrum. The neural arch is too poorly preserved to describe any details. Likewise, specimen MzA NAT15058 is a poorly preserved posterior half of a strongly constricted dorsal vertebra, but does not present much useful information. Interestingly, though, the centrum seems to be hollow ventrally.

Caudal vertebrae Caudal vertebrae include centra (with parts of the neural arch preserved) of an anterior caudal (MzA NAT15091; Fig. 14g) and two mid-caudals (MzA NAT15089 and 15098), as well as a rather well-preserved distal caudal vertebra (MzA NAT15097; Fig. 14h–j).

The most anterior caudal vertebra preserved, MzA NAT15091, has a massive centrum that is slightly higher than long and has high oval articular surfaces (Fig. 14g). The ventral surface is broad and rounded, without a ventral groove, and offset from the lateral sides by rounded ridges. The broken remnant of a stout transverse process is present on the posterior half of the base of the neural arch. The neural canal is narrow and has a level ventral margin, which is not incised into the centrum.

Specimen MzA NAT15098 represents an anterior mid-caudal that seems to be generally similar to the previous element, but is relatively more elongate and has well-developed chevron facets posteriorly. No transverse process is visible, but the dorsal part of the centrum is considerably eroded. Likewise, MzA NAT15089 is an even more elongate caudal vertebra with a centrum that is longer dorsally than ventrally and has a notable lateral swelling at the dorsal margin of the centrum, but the presence of a transverse process is uncertain.

In contrast, the distal caudal vertebra MzA NAT15097 is rather well preserved (Fig. 14h–j). The centrum is elongate, but rather massive, being only slightly constricted and broadly rounded ventrally. Well-developed chevron facets are present posteriorly. A lateral swelling is present at the base of the neural arch, being offset from the lateral side of the centrum by a narrow and shallow longitudinal groove. The neural arch is low and the neural canal is small, being broader than high anteriorly and round posteriorly. The prezygapophyses are broken, but they overhung the centrum anteriorly and are medially connected by a broad intraprezygapophyseal lamina. The postzygapophyses are developed as oval, lateroventrally facing articular facets at the base of the posterior end of the neural spine and overhang the centrum posteriorly for half of their length. The neural spine is anteroposteriorly short and placed over the posteriormost end of the neural arch. It is slightly inclined posteriorly and seems to have been low, although the distal end is missing.

Ribs and chevrons Specimen MzA NAT15105 is a large, probably anterior dorsal rib. The proximal end has a well offset tuberculum that is not connected to the capitulum by a bony webbing, as is the case in some basal sauropods (e.g. Rauhut 2003a). The shaft is only slightly flexed and somewhat transversely flattened, but without the plank-like appearance of dorsal ribs in sauropods. A weakly developed longitudinal anterolateral groove is present.

A slender, rod-like bone, MzA NAT15106, is obviously a gastral rib (Fig. 15a). Although gastralia are rarely reported from sauropodomorphs, they are present in both basal forms (e.g. Fechner and Gößling 2014) as well as sauropods (see e.g. Tschopp and Mateus 2013). The preserved element is 34.5 cm long, but maximally only 1.2 cm wide, and thus very slender, as it is usual for gastralia. The element is slightly bowed and tapers towards both ends. A longitudinal groove is present in one side of the element, probably for the contact with the adjacent medial or lateral element, but extends for less than half of its length.

Fig. 15
figure 15

Sauropodomorph material resulting from the recent excavation at Schleitheim-Santierge. a gastral rib, MzA NAT15106, in dorsal or ventral view; b chevron, MzA NAT15081, in posterior view; ce right metacarpal I, MzA NAT15082, in dorsal (c), distal (d) and medial (e) view. lg, longitudinal groove. Scale bars equal 10 cm

A large anterior caudal chevron, MzA NAT15081 (Fig. 15b), has a dorsally bridged, triangular hemal canal and a simple, transversely compressed and distally slightly anteroposteriorly expanded shaft. The proximal facets for the contact with the vertebrae are gently convex anteroposteriorly, but not clearly subdivided. The total length of the element is ca. 22 cm.

Metacarpal A poorly preserved right metacarpal I of a large basal sauropodomorph, MzA NAT15082 (Fig. 15c–e), is present in the newly collected material. The element is strongly compressed and misses the proximal end. However, the proximalmost part of the lateral side expands notably and abruptly, indicating that not much is missing here. Regardless of the compression, the bone was obviously considerably broader transversely than high dorsoventrally, and it was probably only slightly longer proximodistally than broad; as preserved, the bone is 7.3 cm long (missing an estimated 1–1.5 cm) and 6.5 cm wide distally. Two well-developed distal condyles are present and separated by a broad groove. As is usual in saurischian first metacarpals, the condyles are asymmetrical, with the lateral condyle extending notably further distally than the medial condyle. Whereas the former tapers distally, the latter is broad and rounded. A weakly developed extensor groove is present on the dorsal side. The medial condyle flares medially on the ventral side, thus bordering a large, but shallow collateral ligament pit on the medial side. The medial extremity of this medial expansion is eroded.

5.3.3 Dorsal vertebra from Hallau–Bratelen

A rather well-preserved, though slightly deformed dorsal vertebral centrum, MzA NAT 15075, was found in Hallau-Bratelen (Fig. 16). The centrum is massive, but strongly constricted, with a broad, rounded ventral surface. As in the vertebrae of Schleitheimia, large, but shallow depressions are present on the lateral sides of the centrum. Only small parts of the neural arch, including a part of the left posterior centrodiapophysial lamina, are preserved. The neural arch was obviously narrow and moderately incised into the centrum. Although the general characteristics of this vertebra are consistent with those seen in the vertebrae of Schleitheimia, the element is too incomplete to refer it to any taxon beyond Sauropodomorpha indet.

Fig. 16
figure 16

Sauropodomorph dorsal vertebra from Hallau-Bratelen, MzA NAT 15075. a Left lateral view; b posterior view. nc, neural canal; pcd, pleurocentral depression; pcdl, posterior centrodiapophyseal lamina. Scale bar equals 10 cm

5.3.4 Material from Hallau-Schwärzibuck

Scapula The left scapula MzA NAT15067 (Fig. 17a, b) from Hallau-Schwärzibuck misses the distal end and large parts of the acromion process. The bone is large and robust, being considerably curved in the preserved, proximal portion. As preserved, the bone is c. 500 mm long, and was originally probably not longer than 700 mm. The minimal height of the shaft is c. 105 mm, c. 240 mm distal to the margin of the glenoid; distal to this point, the shaft expands again, most notably on its anterodorsal border. Proximally, the shaft expands towards the acromion process, which was high and well-developed, so that the anterodorsal margin of the shaft is concave in outline. The posteroventral margin of the shaft is straight to very slightly convex and shows a marked, slightly rugose convexity below the level of the base of the acromion process. The glenoid region expands posteroventrally from the shaft, though less than the acromion process. The glenoid facet is large, semioval in outline and strongly concave transversely and anteroposteriorly, although this might be slightly exaggerated by deformation. A supraglenoid fossa was obviously present on the acromion process and is bordered by a sharp edge posterodorsally in its dorsal part.

Fig. 17
figure 17

Sauropodomorph material from Hallau-Schwärzibuck. a, b Left scapula, MzA NAT15067, in ventral (a) and lateral (b) view; c, d distal end of left femur, MzA NAT15065, in posterior (c) and distal (d) view; e, f pedal phalanx, MzA NAT15068, in dorsal (e) and lateral (f) view; g, h pedal phalanx, MzA NAT15069, in dorsal (e) and lateral (f) view. clg, collateral ligament groove; fc, fibular condyle; g, groove; gl, glenoid; rc, rugose convexity; tc, tibial condyle. Scale bar equals 10 cm

Femur The distal end of a large left femur from Hallau-Schwärzibuck, MzA NAT15065 (Fig. 17c, d), is considerably deformed, most notably compressed anteroposteriorly. As preserved, it is c. 220 mm wide mediolaterally and maximally 115 mm deep anteroposteriorly at the lateral condyle. Both distal condyles are well developed, the tibial condyle being wider and more massive than the fibular condyle. The fibular condyle is triangular in distal outline, with a flattened posteromedial side. Both condyles are separated by a wide, subrectangular intercondylar groove. The fibular condyle seems to be offset from the lateral margin of the bone by a wide, rounded shelf, in contrast to the condition in Schleitheimia, where such a shelf is apomorphically absent. However, it cannot be completely ruled out that the shelf in this specimen might have at least partially been exaggerated by distortion. On the distal surface, the distal articular surface of the fibular condyle is separated from the strongly convex articular surface on the distal end of the lateral part of the femur by a narrow, oblique groove. Anteriorly, a shallow depression seems to be present on the distal end of the femur, but a deep anterior intercondylar groove is absent.

Pedal phalanges Two pedal phalanges, MzA NAT15068 and NAT15069, were found in the same locality (Fig. 17e–h). Both elements are stout and robust, but whereas MzA NAT15069 is longer proximodistally (73 mm) than wide mediolaterally (61 mm) proximally, MzA NAT15068 is approximately as wide as long (67 mm). The proximal articular surface is broad, semioval in outline and both dorsoventrally and transversely concave in both elements, indicating that they might represent first phalanges that directly articulated with their respective metatarsal. The distal end is gynglimoidal, with broadly separated condyles and well developed collateral ligament pits.

Identification of material from Hallau-Schwärzibuck As there is no detailed information about the possible association of these remains, it cannot be established if all of these elements might represent the same taxon or even the same individual. However, all of the remains are of fitting size and apparently represent a large, robustly built basal sauropodomorph. The scapula is considerably more robust than scapulae of Plateosaurus (e.g. Huene 1926) and also differs from this taxon in the presence of the conspicuous ventral convexity in the shaft below the base of the acromion process. On the other hand, the distal femur differs markedly from the similarly sized femur of Schleitheimia in that the crista tibiofibularis is notably more slender than the medial condyle, has a more posteriorly pointed outline in distal view, and is markedly offset from the lateral margin of the distal femoral shaft. Thus, under the assumption that all of this material from Hallau-Schwärzibuck represents the same taxon, a referral to both Plateosaurus and Schleitheimia seems unlikely. These remains thus most probably indicate the presence of a third, large and robustly built sauropodomorph in the Late Triassic of Schaffhausen. As there is no overlap in material with the also large and robust Gresslyosaurus ingens from the Late Triassic (Norian) of Niederschönthal, close to Basel (see Huene 1907-8, 1932; Galton 1986), it cannot be said whether this material might represent the latter taxon.

6 Discussion

6.1 Comparison of Schleitheimia with other basal sauropodomorphs

As noted in the introduction, Galton (1986) referred all the material from Canton Schaffhausen to the genus Plateosaurus. However, the material from Schleitheim of the excavation of Schutz shows numerous differences from that genus and other sauropodomorphs for which comparable material is known. The posterior cervical vertebra is notably short, with a length/anterior height ratio of approximately 1.3. This is considerably shorter than in most sauropodomorphs. The same ratio is approximately 1.6 in the shortest posterior cervical of Plateosaurus (Huene 1926) and a similar ratio is present in a posterior cervical of Mussaurus (Otero and Pol 2013). In massospondylids, the cervical vertebrae are even more elongated, and posterior cervicals are typically more than twice as long as high (Martínez 2009; Apaldetti et al. 2013; Barrett et al. 2019). Even in the large and massive Lessemsaurus, the probably last cervical vertebral centrum has a length/height ratio of c. 1.5 (Pol and Powell 2007a). Sauropod cervicals tend to be even more elongate. The only other non-sauropodan sauropodomorph which seems to have similarly short posterior cervicals is Lamplughsaura (Kutty et al. 2007).

Another noteworthy feature of Schleitheimia is the morphology of the anterior dorsal vertebra. As noted in the description, the centrum is strongly constricted, with the constriction being asymmetrical in ventral view, the narrowest portion being placed at approximately one-third of centrum length. This differs from the more symmetrical constriction in Plateosaurus (MB Skelett XXV; Huene 1926; Moser 2003), other non-sauropodiform sauropodomorphs (e.g. Saturnalia: MCP 3844-PV; Plateosauravus: SAM-PK 3342; Unaysaurus: UFSM 11069; Jingshanosaurus: Zhang and Yang 1994; Adeopapposaurus: PVSJ 610), and basal sauropodiforms (e.g. Xingxiulong: Wang et al. 2017; in which the narrowest portion of the vertebra is placed more or less at mid-length of the element. A similar condition as in Schleitheimia is, however, present in Lessemsaurus (Pol and Powell 2007b), the possibly derived sauropodiform Lamplughasaura (Kutty et al. 2007) and basal sauropods (e.g. Tazoudasaurus: Allain and Aquesbi 2008; Patagosaurus: PVL 4170). Thus, the asymmetrical constriction of the anterior dorsal might be another character supporting a derived sauropodiform placement of Schleitheimia. A further unusual character of the anterior dorsal, the marked lateroventral ridges on the posterior half of the centrum, have not been described or observed by us in any other non-sauropodan sauropodomorph and might thus also represent an apomorphic character of the new taxon.

A further noteworthy character of the vertebrae of Schleitheimia is the shape of the neural canal, which is deeply incised into the dorsal surface of the vertebral centra in its middle course, but becomes shallower towards the anterior and posterior exits of the canal. Unfortunately, the absence or presence of this character is often difficult to evaluate in specimens that are preserved with their neural arches attached, and it is even more rarely described. However, such a deep incision of the neural arch is absent in basal sauropodomorphs such as Saturnalia (MCP 3844-PV) and Plateosaurus (SMNS and BSPG, numerous specimens). A similar situation to that seen has been described in an anterior caudal of the basal sauropod Vulcanodon (Cooper 1984) and the dorsals of the basal sauropod Amygdalodon (Rauhut 2003a), and it might also be present in the lessemsaurid Antetonitrus (McPhee et al. 2014). Thus, this character might be another feature of sauropodiforms or a subclade thereof, but more data on its distribution is needed. It might be noted, though, that the floor of the neural canal is flat in the dorsal vertebral centra of the basal sauropod Volkheimeria (PVL 4077).

A further character shared between Schleitheimia and Lessemsaurus is the low length/height ratio of the posterior dorsal vertebrae. This ratio is approximately 0.8 in Schleitheimia and 0.7 in Lessemsaurus (Pol and Powell 2007b), whereas it is around one in Plateosaurus (Huene 1926) and even more in taxa such as Massospondylus (Barrett et al. 2019) and Jingchanosaurus (Zhang and Yang 1994). The basal sauropod Tazoudasaurus also has relatively short posterior dorsals, with a length/height ratio of c. 0.74 (Allain and Aquesbi 2008).

The reconstructed ilium of Schleitheimia is superficially rather similar to that of other basal sauropodomorphs (Fig. 18). However, one should keep in mind that this partially depends on the reconstruction of the missing portions, and several differences with most other basal sauropodomorphs are found in detailed morphology. One of these characters concerns the articular surface of the ischial peduncle of the ilium. In most basal sauropodomorphs, such as Ruehleia (MB.R. 4737, 4718.103), Plateosaurus (SMNS 91269), Adeopapposaurus (PVSJ 610), or Lessemsaurus (Pol and Powell 2007b), the distal end of the peducle is flattened or bluntly convex. In Schleitheimia and basal sauropods, such as Volkheimeria (PVL 4077), as well as a few non-sauropodan sauropodomorphs, including Leonerasaurus (Pol et al. 2011), the peduncle is semicircular in lateral view and transversely widened.

Fig. 18
figure 18

Comparison of outlines of the right ilia of several non-sauropodan sauropodomorphs. a Reconstruction of the ilium of Schleitheimia. bPlateosaurus (based on Galton and Upchurch 2004). cAdeopapposaurus (left ilium reversed; based on Martínez 2009). dLessemsaurus (based on Pol and Powell 2007b). ac, acetabulum; ip, ischial peduncle; pp, pubic peduncle. Not to scale; drawn to the same length over the pubic and ischial peduncles

Another character concerns the development of the medial brevis shelf. In basal sauropodomorphs, including Rhueleia (MB.R. 4737) and Plateosaurus (SMNS 91269), a distinct brevis fossa is present, bound medially by a medial brevis shelf that ascends steeply from the posteromedial side of the ischial peduncle to the posterior end of the postacetabular blade. The third sacral rib attaches to the medial brevis shelf from medially. In other sauropodomorphs, including sauropods, a distinct brevis fossa is absent, and the medial brevis shelf is developed as a medial ridge for the attachment of the sacral rib (the sacricostal ridge of Barrett et al. 2019). In Schleitheimia, this ridge is prominent, rounded in cross-section and expands posteriorly into a semicircular expansion, a morphology that seems to be unique to this taxon (Fig. 19).

Fig. 19
figure 19

Stereophotograph of the medial side of the postacetabular process of the ilium of Schleitheimia, PIMUZ A/III 550, showing the unusual development of the medial brevis shelf (mbs). Posterior is to the top

Finally, the distal femur of Schleitheimia is notably robust, with especially the lateral condyle (the crista tibiofibularis) being very wide transversely and massive anteroposteriorly (Fig. 20). One unusual character is the lack of a posteriorly facing shelf lateral to the crista tibiofibularis. A marked lateral expansion of the main femoral body, leading to the formation of such a shelf is present in most saurischians, but only a small, broad, rounded expansion is present in the femur of Schleitheimia (Fig. 20d). Although a similar condition is present in some basal saurischians (e.g. Eoraptor; Fig. 20a), and a few other basal sauropodomorphs (e.g. Ruehleia; MB.R. 4718.99), the vast majority of basal sauropodomorphs and also sauropods (e.g. Isanosaurus. Buffetaut et al. 2000; Volkheimeria: PVL 4077; Patagosaurus: PVL 4170) show this marked expansion and the associated shelf, so that the absence of this feature can be seen as a local autapomorphy of Schleitheimia.

Fig. 20
figure 20

Comparison of the distal outlines of the left femora of a basal saurischian (a) and several non-sauropodan sauropodomorphs (bd). aEoraptor (right femur reversed; based on Sereno et al. 2013). bPlateosaurus (right femur reversed; based on Huene 1926). cColoradisaurus (based on Apaldetti et al. 2013). dSchleitheimia. Abbreviations: ctf, crista tibiofibularis; le, lateral expansion, forming a posteriorly facing shelf lateral to the crista tibiofibularis on the distal femur in Plateosaurus and Coloradisaurus; mc, medial condyle. Arrows point to the flattened posteromedial surface of the crista tibiofibularis in the sauropodomorph taxa. Not to scale; drawn to the same distal width

6.2 Phylogenetic position of Schleitheimia

The phylogenetic analysis resulted in the recovery of 7632 equally parsimonious trees with a length of 1551 steps (CI 0.293, RI 0.655, RC 0.192). The strict consensus tree (Additional file 1: Figure S1) is reasonably well resolved, and in general accordance with the results of McPhee et al. (2015), Otero et al. (2015), and Apaldetti et al. (2018), although with several differences in the placements of individual taxa. A polytomy at the basis of Sauropodomorpha includes the genera Chromogisaurus, Pampadromeus, Panphagia, and Saturnalia. Apart from a number of intercalated single taxa, three clades are recognized in basal, non-sauropodan sauropodomorphs: the Plateosauridae (including Unaysaurus, Plateosaurus gracilis, and Plateosaurus engelhardti), a clade comprising Eucnemesaurus and Riojasaurus, and the Massospondylidae. Interestingly, the latter clade does not only include the genera usually placed in Massospondylidae (Massospondylus, Leyesaurus, Adeopapposaurus, Lufengosaurus, Glacialisaurus and Coloradisaurus; McPhee et al. 2015; Otero et al. 2015; McPhee and Choiniere 2018), but also Jingshanosaurus, Seitaad, and Yunnanosaurus, which form a distinct subclade within massospondylids. Above this clade, Xingxiulong was found as the most basal sauropodiform, followed by two large polytomies. The first of these polytomies includes the genera Aardonyx, Anchisaurus, Leonerasaurus, Meroktenos, Mussaurus, and Sefapanosaurus, whereas the second includes Antetonitrus, Blikanasaurus, Camelotia, Gongxianosaurus, Ingentia, Lessemsaurus, Melanorosaurus, and Pulanesaura. Finally, the new taxon, Schleitheimia, and Isanosaurus are found in a polytomy as direct outgroups to Sauropoda.

Reduced consensus methods identify several problematic taxa, the a posteriori exclusion of which considerably improves resolution of the tree (Fig. 21a). Thus, at the basis of Sauropodomorpha, the highly incomplete Chromogisaurus (Ezcurra 2010) is identified as problematic taxon, and its exclusion results in the recovery of a monophyletic clade including Panphagia and Pampadromeus as the most basal sauropodomorphs, followed by Saturnalia. At the base of Sauropodiformes, Leonerasaurus and Sefapanosaurus take several equally parsimonious positions, and exclusion of these two taxa leads to a pectinate arrangement of Anchisaurus, Mussaurus and a polytomy of Meroktenos and Aardonyx below the more derived sauropodiforms. The second polytomy in Sauropodiformes is caused by Blikanasaurus and Camelotia, and excluding these taxa leads to three additional nodes below Schleitheimia, with Melanorosaurus being the most basal taxon in this pectinate arrangement, followed by a polytomy including Antetonitrus, Ingentia and Lessemsaurus, and a second polytomy including Pulanesaura and Gongxianosaurus. Thus, in contrast to Apaldetti et al. (2018) we do not recover a monophyletic Lessemsauridae even in the reduced consensus tree, although such an arrangement is found with a frequency of 86% in the majority rule consensus tree.

Fig. 21
figure 21

Reduced consensus cladograms of basal sauropodomorph relationships resulting from a phylogenetic analysis of 382 characters scored for 66 taxa (see text for details), showing the phylogenetic position of Schleitheimia. a Maximum parsimony analysis using equal weights. b Maximum parsimony analysis using implied weights (k = 12). Numbered nodes: 1, Sauropodomorpha; 2, Plateosauridae; 3, Massopoda; 4, Massospondylidae; 5, Sauropodiformes; 6, Sauropoda

Characters supporting a position of Schleitheimia as a derived, non-sauropodan sauropodiform include the following: Lateral depression on the cervical vertebrae (C 129; shared with sauropods); marked lateral depressions on the dorsal vertebral centra (C 148; shared with sauropods); anteroposteriorly short posterior dorsals (C 152; shared with most sauropods); short posterior caudal vertebrae (C 184; synapomorphy of Sauropodiformes); triangular outline of bases of anterior caudal vertebral transverse processes (C 186; shared with Pulanesaura and sauropods); dorsoventrally deep anterior caudal transverse processes (C 190; shared with sauropods); rounded entepicondyle of distal humerus (C 219; reversal to basal saurischian condition; shared with all sauropodiforms that are more derived than Melanorosaurus, with the exception of Pulanesaura); rounded distal end of the ischial peduncle of the ilium (C 266; shared with sauropods); shortened ischial peduncle of ilium (C 268; shared with sauropods); symmetrical fourth trochanter on the femur (C 309; shared with sauropods); mediolaterally wide crista tibiofibularis on the distal femur (C 315; shared with Melanorosaurus and more derived sauropodiforms); pitted surfaces of the articular ends of limb bones (C 279; shared with sauropods).

In order to evaluate the support for the position of Schleitheimia as probable outgroup to sauropods, we tested alternative topologies using constrained analyses in TNT. A referral of the material from Schleitheim to Plateosaurus or the Plateosauridae, as argued by Galton (1986), requires an additional 12 steps; given that only 45 characters could be coded for Schleitheimia, this difference makes it extremely unlikely that Schleitheimia represents a plateosaurid or can even be synonymized with Plateosaurus. Likewise, a position of Schleitheimia outside Sauropodiformes requires 9 additional steps and is thus also rather unlikely. Even a position of the new taxon one node further outside Sauropoda requires four additional steps and is therefore also considerably less parsimonious.

The analysis using all material referred to Schleitheimia and implied weights resulted in 5 equally parsimonious trees with a score of 68.58801. The consensus of these trees generally agrees with the results from the unweighted analysis; however, after the a posteriori deletion of the unstable taxon Ohmdenosaurus (which is placed in several positions as a derived non-sauropodan sauropodiform), a fully resolved tree was found (Fig. 21b). In this analysis, Leonerasaurus and Anchisaurus form a clade at the base of sauropodiforms above the basalmost taxon Xingxiulong, followed by a pectinate arrangement of Mussaurus, Aardonyx, Sefapanosaurus, Meroktenos, Melanorosaurus, Camelotia, and higher sauropodiforms. The latter include a monophyletic Lessemsauridae, including Lessemsaurus, Antetronitus and Ingentia, at the base and Blikanasaurus, Pulensasaura, Gongxianosaurus, Schleitheimia, Isanosaurus, and Tazoudasaurus as consecutively closer outgroups to Sauropoda. Within sauropods, Vulcanodon represents the most basal taxon (by definition of that clade), followed by Amygdalodon, Spinophorosaurus, Volkheimeria, Cetiosaurus, a Patagosaurus + Barapasaurus clade, Shunosaurus, Mamenchisaurus, and an Omeisaurus + Neosauropoda clade. However, as the character list is mainly constructed to resolve non-sauropodan sauropodomorph relationships, results within Sauropoda should be seen with caution.

Our separate analyses of the type ilium or the referred material separately confirm the position of the new taxon and support the association of the remains (Fig. 22). The analysis of the type ilium only resulted in the recovery of 5244 equally parsimonious trees with a length of 1546 steps. The strict consensus of this analysis finds the type ilium in a large polytomy outside Sauropoda, together with all other non-sauropodan sauropodiforms more derived than Meroktenos. Reduced consensus methods again place the new taxon as sister taxon of Sauropoda (Fig. 22a), though with an uncertain position for Pulanesaura (which was removed by reduced consensus methods), for which no ilium is known (McPhee and Choiniere 2018). Likewise, the analysis of the referred material without the type ilium resulted in the recovery of 7632 trees with 1550 steps. This analysis finds the material from Schleitheim in a polytomy with Isanosaurus outside Sauropoda already in the strict consensus tree (Fig. 22b), thus mirroring the results of the analysis of all of the material.

Fig. 22
figure 22

Separate phylogenetic analysis of the holotype ilium only (a) and the referred material of Schleitheimia, showing congruent results (b). Only simplified sauropodiform interrelationships are shown (see Additional file 2: Figure S2 and Additional file 3: Figure S3 for complete strict consensus trees)

6.3 Basal sauropodomorph diversity in the Triassic of Switzerland

With the description of Schleitheimia, the Late Triassic (Norian) sauropodomorph fauna from Switzerland includes at least three different taxa of non-neosauropodan sauropodomorphs. The Gruhalde Quarry in Frick, Kanton Aargau, has yielded numerous specimens of the genus Plateosaurus (Galton 1986; Sander 1992; Meyer and Thüring 2003; Hofmann and Sander 2014), although it is still somewhat uncertain if these remains represent the same species of this genus as the famous lagerstätten in Baden-Württemberg or other localities in Germany. The astragalus of Plateosaurus from Santierge described above provides further evidence that this genus was also widespread in the Norian of Switzerland. Schleitheimia represents a considerably larger and more derived sauropodiform sauropodomorph, and the material of Hallau-Schwärzibuck seems to indicate another, large non-sauropodan sauropodomorph, so that at least three medium-sized to large sauropodomorph taxa were present in the Late Triassic of Switzerland.

Another formally named taxon is Gresslyosaurus ingens from Niederschönthal in the Canton Basel-Landschaft. This taxon is based on a partial sacrum, some caudal vertebrae, a metacarpal and fragments of the hindlimbs, including partial left and right tibiae, an almost complete fibula, and pedal elements (Huene 1907-8; Galton 1986). Galton (1986) referred this material to Plateosaurus, and this assignment was followed by most subsequent authors and has been supported in several recent phylogenetic analyses (e.g. Yates 2007; McPhee et al. 2015; Otero et al. 2015). However, Moser (2003) found significant differences in the sacral vertebrae between Gresslyosaurus and Plateosaurus and questioned the referral of the former to the latter, a conclusion with which we agree (OR, pers. obs, 2017). As noted above, the material is currently being re-prepared, and a detailed revision of all the material from Niederschönthal will certainly help to identify the affinities of this taxon. The material represents an animal of comparable size to both Schleitheimia and the remains from Hallau-Schwärzibuck. Unfortunately, however, as there is very limited overlap of remains, it cannot currently be decided with certainty whether it might represent either of these, or a third large basal sauropodomorph taxon from the Late Triassic of Switzerland. Gresslyosaurus is similar to Schleitheimia in that the neural canal in the sacral vertebrae is deeply incised into the vertebral centra, but, as noted above, this seems to be a more general character found in derived non-sauropodan sauropodiforms and basal sauropods. However, a possible difference between Gresslyosaurus and Schleitheimia is that the sacral vertebrae of the former are rather elongate (length/height ration of approximately 1.4), whereas both the posterior dorsals and anterior caudals of Schleitheimia are short (length/height ratio of 0.8 or less). As the sacral vertebrae tend to be similar in relative length to the last dorsals in sauropodmorphs, this might be an argument against a synonymy of the two taxa. A further difference is found in the caudal vertebrae. The poorly preserved mid-caudals of Gresslyosaurus are unusual in being slightly wedge-shaped in lateral view, the ventral side being shorter than the dorsal side (NMB N B 1573, 1577). This character is absent in Schleitheimia, in which the mid-caudal vertebrae are rectangular in lateral view. Thus, these—admittedly limited—comparisons indicate that Schleitheimia is different from Gresslyosaurus.

6.4 Implications for basal sauropodomorph evolution and the origin of sauropods

Disregarding the recent discussion of the definition of Sauropoda (see Peyre de Fabrègues et al. 2015; McPhee and Choiniere 2018), the origin and early evolution of this clade has received considerable attention lately, due to improved resolution of basal sauropodomorph relationships (e.g. Yates 2004, 2007; Upchurch et al. 2007a; Apaldetti et al. 2014, 2018), new discoveries (or interpretations) of close sauropod relatives (e.g. Yates and Kitching 2003; Upchurch et al. 2007b; Yates et al. 2010; Pol et al. 2011; McPhee et al. 2015, 2018; Otero et al. 2015), and several studies on the evolution of the sauropod body plan in relation to their gigantism (e.g. Rauhut et al. 2011; Sander et al. 2011; Sander 2013; Bates et al. 2016; McPhee et al. 2018). As for the timing of sauropod origins, there seems to be a conflict between osteological and ichnological evidence. Whereas the late Early Jurassic (Pliensbachian-Toarcian; McPhee et al. 2017) Vulcanodon is generally regarded as the oldest osteological evidence for sauropods, tantalizing trackway evidence from the Late Triassic of Argentina (Marsicano and Barredo 2004) and, especially, Greenland (Lallensack et al. 2017) indicate the existence of sauropods already in the Late Triassic. As the putative Late Triassic sauropod Isanosaurus (Buffetaut et al. 2000; here found as one of the immediate outgroups to Sauropoda) has recently been argued to be no older than Pliensbachian in age (Racey and Goodall 2009), the placement of the probably Late Norian Schleitheimia as probable sister taxon to Sauropoda lends support to the origin of the latter clade already in the Late Triassic. Interestingly, however, Lallensack et al. (2017) identified several characters in the sauropod tracks of Greenland that indicate a foot morphology more derived than the Early Jurassic Vulcanodon and Tazoudasaurus. If confirmed, this would signify an early, Triassic split of vulcanodontids from the lineage leading to Eusauropoda and a survival of at least two sauropod lineages of the Triassic/Jurassic boundary. However, pedal anatomy of most sauropodiforms close to the origin of sauropods is still poorly known, and thus there is the possibility that the condition in vulcanodontids represents a reversal, as argued by Yates et al. (2010; see also Wilson 2005), and the Late Triassic sauropod-like tracks might have been made by large, graviportal non-sauropodan sauropodiforms, such as Schleitheimia. As argued by McPhee and Choiniere (2018), several pedal morphologies might have evolved in parallel in sauropodiforms on the lineage towards sauropods.

However this may be, the results of our phylogenetic analyses further highlight three aspects in early sauropodomorph evolution: the marked radiation of the clade already in the Late Triassic, the relatively limited effect of the Triassic/Jurassic extinction event on sauropodomorph evolution and diversity, and an apparently delayed ascent of sauropods in the late Early to Middle Jurassic (Fig. 23). Under the phylogenetic hypothesis presented here, all major clades of basal sauropodomorphs, including true sauropods, originated in the Late Triassic, with only the oldest representatives coming from Carnian sediments, while most taxa, including Schleitheimia as possible immediate outgroup to Sauropoda appear in the Norian. Furthermore, whereas many of the Carnian taxa for which cranial remains are known still show clear evidence for a carnivorous or at least omnivorous diet (see Cabreira et al. 2016), Norian sauropodomorphs seem to show increasing adaptations towards a herbivorous diet. This is thus in accordance with a rapid radiation of sauropodomorphs in the Late Carnian and early Norian, following an extinction of other large-bodied herbivores during the Carnian Pluvial Episode in the mid-Carnian, as recently suggested (Bernardi et al. 2018).

Fig. 23
figure 23

Time-calibrated cladogram of basal sauropodomorph relationships (based on the unweighted analysis), showing the survival of numerous lineages (including sauropods) across the Triassic-Jurassic boundary

On the other hand, the presence of basically all non-eusauropod lineages already in the Triassic [especially if the trackway record from Greenland represents a sauropod more derived than Vulcanodontidae, as argued by Lallensack et al. (2017)] indicates that, apart from single taxa, only few lineages disappeared before the Jurassic, and most seem to have crossed the Triassic-Jurassic boundary (Fig. 23). Apart from the Panphagia/Pampadromeus clade, which might represent a first small mid-Carnian radiation that disappeared before the main radiation of sauropodomorphs in the latest Carnian and Norian, only the Plateosauridae and the Riojasaurus/Eucnemesaurus clade did not extend into the Jurassic. On the other hand, given the Late Triassic age of Schleitheimia, the nesting of Coloradisaurus with Glacialisaurus and Lufengosaurus, and the relationships among sauropodiforms, at least thirteen lineages of sauropodomorphs survived the end-Triassic extinction. Apart from the three distinct subclades of the Massospondylidae, the Sauropoda and the Lessemsauridae (if this clade is monophyletic and Antetonitrus is Early Jurassic in age; see McPhee et al. 2017), these are lineages that lead to single, Early Jurassic taxa, the origin of which must have been in the Norian at the latest. Thus, although the end-Triassic event might have had some effect on sauropodomorph diversity, it neither seems to have had a devastating effect on the early radiation of this clade, nor does it seems to have kick-started their great success in the later Mesozoic.

An interesting consideration in this respect concerns the sauropods. As this clade must have originated by the Late Triassic, if Schleitheimia is considered to be its immediate outgroup (and notwithstanding the unresolved position of Isanosaurus), sauropods thus remained a seemingly little diverse side lineage of sauropodomorphs over most of the Early Jurassic, as the main dinosaur faunas known from that time (Upper Elliot and Clarens Formations of South Africa, Early Jurassic units in San Juan and Chubut provinces of Argentina, Kayenta Formation of North America, Lufeng Formation of China) were largely dominated by other basal sauropodomorph lineages, usually massospondylids (as recovered in the current analysis), both in terms of taxa represented and number of specimens found. Only after the disappearance of these basal, non-sauropodan forms towards the end of the Jurassic (none of the occurrences of these clades is demonstrably younger than Pliensbachian), sauropods seem to have become more common and then radiated rapidly. Indeed, the recent discoveries of probable neosauropods from the early Middle Jurassic (Carballido et al. 2017; Xu et al. 2018) indicate that this radiation must have been extremely fast in the latest early to early Middle Jurassic. This pattern is consistent with the suggestion by Allain and Aquesbi (2008; see also Allain and Läng 2009) that sauropod radiation and success was associated with and probably triggered by the Pliensbachian/Toarcian extinction event, as it has recently also been suggested for theropod dinosaurs (Pol and Rauhut 2012; Rauhut et al. 2016). What exact ecological changes led to this apparently drastic event, which also affected other clades of terrestrial vertebrates and seemed to have been even more marked in the terrestrial realm than in marine environments, remains unknown and requires further investigation.

7 Conclusions

Fragmentary sauropodomorph remains from the probably Late Norian of Schaffhausen, Switzerland, that were long considered to represent the common central European genus Plateosaurus can be shown to represent a separate taxon of non-sauropodan sauropodomorphs, Schleitheimia schutzi. The recognition of this new taxon, together with an evaluation of other sauropodomorph material from the Late Triassic of Schaffhausen shows that at least three different basal sauropodomorph taxa were present in the Norian of Switzerland. Schleitheimia is a derived sauropodiform and might even represent the immediate outgroup to sauropods. In the context of a phylogenetic analysis, the new taxon indicates that the Triassic/Jurassic extinction event probably only had a minor effect on sauropodomorph evolution, and that the ascent of sauropods was delayed until the late Early Jurassic, when other basal sauropodomorph lineages perished in the Pliensbachian/Toarcian extinction event and gave way to an explosive radiation of that clade.