Europrotomus (Mollusca: Caenogastropoda: Strombidae): a new Middle Miocene European strombid genus (Revision of Euprotomus Gill, 1870. Part 4)
The medium-sized, strongly ornamented nominal species Strombus schroeckingeri Hörnes in Hoernes & Auinger, 1884 is well known from Langhian deposits of the Paratethys Sea. Its traditional generic affiliation in the literature with Euprotomus Gill, 1870, implicated a biogeographic relation of the Paratethys and the proto-Mediterranean with the Neogene Indo-West-Pacific region. This relation, however, is problematic because the Tethys Seaway was already closed or a very shallow, strongly evaporitic passage at that time. Despite its superficial similarity with extant genera of the IWP region, the genus is unrelated to all known strombid genera and represents a new genus, which is introduced herein as Europrotomus nov. gen. The genus comprises only one or maybe two species, which occur in the European Middle Miocene geological record. No ancestors are known so far. This sudden occurrence is discussed as immigration from an adjacent bioprovince rather than as a result of autochthonous evolution. Hypothetically, such a biogeographic source area might have been established along the coasts of tropical West Africa—a scenario that is already documented for Pleistocene times.
Die nominale Art Strombus schroeckingeri Hörnes in Hoernes & Auinger, 1884 ist ein stark ornamentierter Strombidae von mittlerer Größe, der aus dem Langhium der Paratethys gut dokumentiert ist. Die traditionelle generische Zuordnung zu Euprotomus Gill, 1870 implizierte eine biogeographische Beziehung zwischen der Paratethys und dem Proto-Mediterran sowie der neogenen Indo-West-Pazifischen Region. Diese Verbindung ist jedoch problematisch, da der Tethys-Seeweg zu dieser Zeit bereits geschlossen war oder nur eine sehr seichte, stark evaproritische Passage repräsentierte. Die Gattung zeigt keine nähere Verwandtschaft mit den bekannten Strombiden-Gattungen, trotz der oberflächlichen Ähnlichkeiten mit einigen modernen Vertretern in der IWP-Region. Daher wird hier für dieses Taxon Europrotomus nov. gen. als neue Gattung eingeführt. Diese Gattung beinhaltet nur ein oder zwei Arten, die ausschließlich aus dem europäischen Mittel-Miozän bekannt sind. Bisher konnten keine Vorgänger nachgewiesen werden, weshalb autochthone Evolution als eher unwahrscheinlich betrachtet wird. Stattdessen könnte dieses plötzliche Auftreten durch Immigration von einer benachbarten biogeographischen Provinz erklärt werden. Ein derartiges biogeograpohisches Herkunftsgebiet könnte hypothetisch entlang der tropischen Küsten West-Afrikas etabliert gewesen sein—ein Szenario, das auch aus dem Pleistozän dokumentiert ist.
Taxa with affinities with Indo-Pacific genera appearing in the proto-Mediterranean during the phase of ceasing connectivity are therefore highly interesting for discussions on biogeographic and palaeogeographic reconnections during the Middle Miocene (Grecchi 1978; Rögl 1998). One of these striking taxa is the nominal strombid species Strombus schroeckingeri Hörnes in Hoernes & Auinger, 1884, which is in some morphological characters reminiscent of representatives of the genus Euprotomus. A Middle Miocene occurrence of this purely IWP genus in the Mediterranean area would clearly imply a marine passage between the Indo-Pacific and the Mediterranean seas at that time. Moreover, it would even point to a western origin of the genus, which is known so far in the IWP only from Pliocene strata (Abbott 1960).
Thus, in the course of our research on the Paratethyan Persististrombus lineages (for some preliminary notes, see Harzhauser and Kronenberg 2008) and a continuation of the revision of Euprotomus Gill, 1870 (Kronenberg 1998, 1999, 2002a, b), we examined a number of specimens of the nominal taxon Strombus schroeckingeri Hörnes in Hoernes & Auinger, 1884.
Strombus schroeckingeri has usually been allocated to Monodactylus Mörch, 1852 (TS by SD (subsequent designation): Strombus adustus Chemnitz [not available] = Lambis aratrum Röding, 1798) by Hörnes in Hoernes & Auinger (1884: 165) and Cossmann (1904: 8), or Euprotomus Gill, 1870 (TS by monotypy Strombus aurisdianae Linnaeus, 1758) by e.g.; Csepreghy-Meznerics (1954: 398), Kojumdigieva and Strachimirov, (1960: 130), Strausz (1966: 223) and Atanackovic (1985: 128). Bandel (2007: 148) more or less explicitly advocated inclusion of S. schroeckingeri in Lentigo Jousseaume, 1886 (TS by monotypy Strombus lentiginosus Linnaeus, 1758). As Strombus schroeckingeri lived about the same time as the representatives of Persististrombus Kronenberg & Lee, 2007 [TS by OD (original designation] Strombus granulatus Swainson, 1822), in the southern basins of the Central Paratethys one might also expect a close relationship between S. schroeckingeri and one or more species allocated to Persististrombus. Therefore, we will take the opportunity to briefly discuss the taxonomic odyssey of the taxa involved.
Analysis of the concepts of Monodactylus, Euprotomus and Lentigo
Most authors allocated schroeckingeri Hörnes in Hoernes & Auinger, 1884, to Monodactylus Mörch, 1852, or to Euprotomus Gill, 1870. Based on shell characters, this allocation appears to be far-fetched, yet in light of the complex history of the genus-level taxon, this allocation is not as strange as one might think.
References to figures and descriptions referred to by Klein (1753) to his concept of Monodactylus
1. Lister 873/29 = Tricornis tricornis
2. Lister 871/25 = cf. Lobatus raninus
Petiver p. 189 no. 3
3. Lister 874/30 = Lobatus gallus
4. Buonanni 309; 310 = Lobatus gallus
5. a. Rumphius caption to pl. 37
Buonanni 301 = Euprotomus aurisdianae
Lister 872 = Euprotomus aratrum and E. bulla
b. Rumphius 111 # XI; text refers to E. aurisdianae and E. bulla
c. Buonanni 302 = Euprotomus bulla
Figure in Klein (1753) pl. 6/106 = cf. Tricornis tricornis
d. Lister 871/26 = Euprotomus cf. aurisdianae
e. Buonanni 306 = ?? „Tricornis“s.l.
Mörch (1852) was the first author to make the name Monodactylus, attributed to Klein (1753), meet the requirements of the International Commission on Zoological Nomenclature (1999). Unfortunately, the name was preoccupied by de Lacépède (1801) who had established it for a perciform fish. In his list of species allocated to Monodactylus, Mörch (1852: 62) mentioned four species that are now allocated to Euprotomus, but also the nominal taxa Strombus lentiginosus Linnaeus, 1758 (the type species of Lentigo Jousseaume, 1886) and S. fasciatus Born, 1778 (now allocated to Conomurex Bayle in P. Fischer, 1884). Both these species do not have a “monodactylus.” Adams and Adams (1853) returned to Klein’s original concept, i.e., included all “monodactyl” species in Monodactylus, and excluded both S. lentiginosus and S. fasciatus from that taxon. Although there is an overlap with Euprotomus, it should be noted that the concept of Monodactylus Mörch (non Lacépède) is not the same as the concept of Euprotomus.
Tryon (1885) was probably one of the first authors who used both Monodactylus and Euprotomus as valid genus level taxa. Like Mörch (1852) and Adams and Adams (1853), Tryon was not aware that the name Monodactylus was preoccupied as he selected S. pacificus Swainson, 1821 (= Lambis vomer Röding, 1798) as type species. Cossmann (1904: 7) did not follow this designation, but selected yet another species, viz. S. gallus Linnaeus, 1758, a species not listed by Mörch (1852), and therefore not eligible as type species of Monodactylus. Cossmann (1904) further listed two fossil species, viz. S. trigonus Grateloup and S. schroeckingeri, in Monodactylus. For a summary of type designations for Monodactylus, see Abbott (1960: 125).
Tryon (1885) designated Strombus laciniatus “Chemnitz” Dillwyn, 1817 (= Strombus sinuatus [Lightfoot], 1786) as type species of Euprotomus. This is an invalid designation as Strombus aurisdianae was the only species mentioned by Gill (1870). By his action, Tryon in fact changed the whole concept of Euprotomus. Apart from the type species, Tryon allocated five more species within Euprotomus. Of these, two are now allocated to Lentigo; the other four are now allocated to Sinustrombus Bandel, 2007, and Thersistrombus Bandel 2007. For a preliminary discussion on these taxa, see Kronenberg (2009). None of these species is currently allocated to Euprotomus.
In his influential work Abbott (1960) brought an end to the confusion about Monodactylus and Euprotomus. Abbott pointed out that Monodactylus Mörch was preoccupied and restricted the concept of Euprotomus. Indeed, Euprotomus sensu Abbott is a morphologically coherent group that is probably monophyletic. This has been confirmed by molecular data by Latiolais (2003, 2006). In the consensus tree as presented by Latiolais et al. (2006), the nominal taxa Lambis vomer (Röding, 1798), L. bulla (Röding, 1798) and Strombus aurisdianae Linnaeus, 1758—all allocated to Euprotomus by Abbott (1960)—plot out as a clade that is sister to the clade of Panamic, western and eastern Atlantic strombids.
Concepts of the genus level taxa Monodactylus, Euprotomus and Lentigo, by alphabetical arrangement of the species allocated to these taxa by different authors
Adams & Adams, 1853
Kronenberg et al., 2010/2011
Adustus (= aratrum) [Euprotomus]
aratrum (= vomer) [Euprotomus]
aurisdianae (= bulla) [Euprotomus]
striatogranulatus (= aurisdianae) [Euprotomus]
Adustus(= aratrum) [Euprotomus]
aratrum (= vomer) [Euprotomus]
australis (= iredalei) [Euprotomus]
costo-muricatus (= raninus) [Lobatus]
guttatus (= bulla) [Euprotomus]
striatogranulatus (= aurisdianae) [Euprotomus]
Aurisdianae (= aurisdianae + bulla)
aurisdianae var. melanostomus (= aratrum)
bituberculatus (= raninus) [Lobatus]
pacificus var. australis (= iredalei)
trigonus† [allocated to Tricornis by Abbott 1960]
Laciniatus (= sinuatus) [Sinustrombus]
papilio (= pipus) [Lentigo]
ponderosus (= thersites) [Thersistrombus]
Laciniatus (= sinuatus) [Sinustrombus]
Private collection Gijs C. Kronenberg, Eindhoven, the Netherlands; to be deposited in NCBNaturalis
Naturhistorisches Museum Wien, Austria
Family Strombidae Rafinesque,1815
GenusEuroprotomusKronenberg & Harzhauser gen. nov.
Type species designated herein:
Strombus (Monodactylus) schroeckingeri Hörnes in Hoernes & Auinger, 1884.
Strombid genus encompassing shells of medium size, with medium-sized spire, flaring outer lip with sharp rim, short anterior canal, distinct row of shoulder knobs on the last three whorls, becoming trifid, and diverging cords on abapertural side of the last whorl.
See description of Europrotomus schroeckingeri below.
Derivation of name:
Compound noun of “Euro,” referring to the European distribution of this genus as known so far, and “protomus” as allusion to the genus Euprotomus Gill, 1870, to which the type species has been allocated.
This fossil strombid genus is known so far only from the European Middle Miocene and was restricted to the Mediterranean Sea and the adjacent Paratethys Sea.
Other species assigned to Europrotomus gen. nov.: Strombus almerai Crosse, 1885; but see below.
Strombus (Monodactylus) schröckingeri Hörnes in Hoernes & Auinger: 165, pl. 19, figs. 6–7
Strombus (Monodactylus) schröckingeri Hörnes.—Cossmann: 8
Strombus (Euprotomus) schröckingeri Hörnes.—Csepreghy-Meznerics: 398, pl. 2, figs. 1–2
Strombus (Euprotomus) schroeckingeri Hörnes.—Kojumdgieva & Strachimirov: 130, pl. 35, figs. 5a–5b
Strombus (Euprotomus) schröckingeri Hörnes.—Strausz: 223, fig. 104
Canarium (Euprotomus) schroeckingeri (Hoernes).—Atanackovic: 128, Pl. 24, figs. 10–11
Strombus (Strombus) coronatus Defrance.—Nikolov (1993): 69, pl. 3, figs. 7–8
Strombus (Strombus) nodosus subcancellata (Grateloup).—Nikolov: 70, pl. 3, figs. 9–10
Strombus (Euprotomus) schroeckingeri (Hörnes).—Harzhauser et al.: 333, fig. 8
Strombus (Lentigo) schroeckingeri Hörnes, 1880 [sic!].—Bandel: 148
Strombus schröckingeri [sic!].—Hiden (2006): 6
- ? 1885
Strombus lentiginosus Linné Var.—Almera & Bofill y Poch: 32, pl. 1 figs 1, 2 [non Strombus lentiginosus Linnaeus, 1758]
- ? 1885
Strombus almerai Crosse: 242. nom nov. pro Strombus lentiginosus Almera & Bofill y Poch, non Linnaeus
- ? 1886
Strombus almerae Crosse.—Almera & Bofill y Poch: 402, pl. 10, figs. 1–2 [unjustified emendation of S. almerai Crosse]
Lectotype: designated herein: NHMW 1867/XIX/72; Fig. 2a; illustrated in Hoernes and Auinger (1884; pl. 19, fig. 7).
Locus typicus: Coşteiu de Sus, Romania; Transylvanian Basin.
Stratum typicum: marly sandstone of the lower Badenian (= lower Langhian).
Measurement: height: 43.4 mm.
Paralectotype 1: Coşteiu de Sus, Romania; Transylvanian Basin; height: 47.2 mm (Fig. 2b), NHMW 1855/XLIII/19b.
Paralectotype 2: Coşteiu de Sus, Romania; Transylvanian Basin; height: 53.8 mm (Fig. 2c), NHMW 1867/XIX/72; previously illustrated by Hoernes and Auinger (1884; pl. 19, fig. 6).
Paralectotype 3: Lăpugiu de Sus, Romania; Transylvanian Basin; height: 52 mm (Fig. 3a); NHMW 1855/XLIII/19a
Paralectotype 4: Lăpugiu de Sus, Romania; Transylvanian Basin; height: 52 mm (Fig. 3b); NHMW 1872/V/25;
NHMW 2007z0114/0005; Fig. 2d; height: 42 mm.
NHMW 2007z0114/0008; Fig. 2e; height: 52 mm.
NHMW 2007z0114/0007; Fig. 2f; height: 51.5 mm.
NHMW 2007z0114/0001; Fig. 3c; height: 23 mm (juvenile).
NHMW 2007z0114/0002; Fig. 3d; height: 23 mm (juvenile).
NHMW 2007z0114/0004; Fig. 3e; height: 30.5 mm (dwarf specimen).
NHMW 2007z0114/0006; Fig. 3f; height: 41 mm.
NHMW 2007z0114/0009; Fig. 3g; height: 49.5 mm.
Medium-sized shells of eight teleoconch whorls. Protoconch strongly abraded in all available specimens and seems to consist of about 2.5 rather high, moderately convex whorls. Up to three varix-like swellings appear on earliest teleoconch whorls aside from numerous oblique axial ribs, soon passing into pointed knobs or nodes. Spire whorls bear a prominent keel, situated variably in the area from the middle of the whorl to the anterior suture. Concave sutural ramp bearing distinct growth lines that are crossed by stronger spiral threads. Spiral threads accompanied by 8–10 blunt spiral ridges on the body whorl, which bears irregular nodes of variable strength; most prominent and pointed ones appear along the shoulder of the body whorl.
Outer lip expanding, attaches up to the 4th and 5th spire whorl; thickened posterior to the strombid notch but thin anterior to it. In the anterior 2/3 of the outer lip a swelling with strong lirae is developed about 5–7 mm deep in the aperture. Three (Hoernes and Auinger 1884: pl. 19 fig. 7a, b here refigured Fig. 2a) to seven (Hoernes and Auinger 1884: pl. 19 fig. 6a, b, here refigured Fig. 2c) broad, low axial lobes occur especially in its posterior part, but also extending to the lateral part as well, bordered by a narrow, moderately deep canal where the wing attaches to the spire. These lobes are a continuation of well-developed spiral cords on the dorsal side of the shell. The two to three most adapical of these cords develop only at the point where the outer lip starts to expand, but the others, when present, are a continuation of strong, knob-bearing, spiral cords already present on the dorsal side of the shell. Columellar callus extending on the base without covering it completely. Further lirae occur in the very anterior part and the posterior termination of the columella.
Comparison of shell characters:
the shells show a broad, glossy columellar callus partially covering the base. In this feature it is quite close to the modern representatives of Euprotomus. However, Europrotomus is readily distinguished from Euprotomus by the difference in the much shorter and the less bent anterior canal, and the absence of the finger-like digit on the outer lip. The sculpture of the outer lip has some counterpart in the shells of the modern Euprotomus vomer-hawaiensis-iredalei complex. Even the lirated axial ridge in the inner side of the outer lip is, although much weaker, still presented in the modern species group. Another similarity is the narrow posterior canal, the presence of varices on the early teleoconch whorls. The paucispiral protoconch of the extant Euprotomus iredalei (Abbott 1960) resembles that of Europrotomus schroeckingeri in its rather low, bulbous shape (about 2–2.5 whorls).
As far as Lentigo is concerned, the general appearance of Europrotomus is quite similar, and this is also true for the dorsal sculpture. In Lentigo there are however only two lobes on the posterior part of the outer lip, contrary to the three to seven in Europrotomus Moreover, in Europrotomus these lobes are clearly a continuation of the well-developed spiral cords, which is not the case in Lentigo. Also, the triangular projections on the strombid notch and flange between the strombid notch and anterior canal present in Lentigo are missing in Europrotomus.
In Persististrombus Kronenberg & Lee, 2007, the edge of the outer lip has no lobes at all, and the outer lip is attached to the shell much more abapically.
The presence of the lobes on the rim of the outer lip is slightly reminiscent of the lobes as seen in Sinustrombus sinuatus ([Lightfoot], 1786), but in the latter species the lobes are much better developed, the outer lip is attached much closer to the apex, and the flange between the strombid notch and the anterior canal. Also, in S. sinuatus the rim of the outer lip is bent sharply towards the columella when reaching adulthood, a character not observed in Europrotomus.
The continuation of the spiral cords into the lobes at the rim of the outer lip is somewhat reminiscent of the way the digits are formed in Lambis and Harpago. In Lambis and Harpago, however, these digits are much longer and are formed by distinct lobes at the mantle edge, where the lateral sides of the mantle edge are bent to reach other, thus forming a hollow cone that is subsequently filled with shell material. The place where the rims of the lobes touched each other remains visible as a very narrow furrow. Moreover, the anterior canal in Lambis is very much elongated.
Based on shell morphology, we conclude that S.schroeckingeri cannot be allocated to Persististrombus, nor can it be allocated to either Euprotomus or Lentigo. The previous taxonomic confusion is largely based on the strongly changing concepts of Monodactylus Mörch (non Lacépède) and Euprotomus. As no other genus level taxon within the family Strombidae appears to fit to accommodate this species, Europrotomus is introduced as a new genus.
A poorly preserved strombid from the Langhian and lower Serravallian of Spain, erroneously identified as Strombus lentiginosus (Almera & Bofill y Poch, 1885), was subsequently renamed by Crosse (1885) as S. almerai and accepted by Almera and Bofill y Poch (1886) as S. almerae. The change in spelling of the specific epithet is however an unjustified emendation of S. almerai (International Commission on Zoological Nomenclature (1999) Art. 33.2.3). This species closely resembles S. schroeckingeri in size and ornamentation. Unfortunately, the sculpture of the aperture is poorly described, except for some comments on granulations of the columella. Additionally, its wing is described as expanding and undulated in its posterior part, and a faint posterior canal is also mentioned by Almera and Bofill y Poch (1885, 1886). Differences, however, are the stout spire and the shoulder of the last whorl, which seems to be closer to the suture than in Europrotomus gen. nov. schroeckingeri. Hence, this specimen might be conspecific with the Paratethyan Europrotomus. schroeckingeri, but a clear decision depends on the availability of more material.
All specimens are found in marly silty sandstone in association with a diverse subtropical mollusc fauna pointing to shallow marine soft bottom environments with normal salinity. It is unknown from the Middle Miocene reefs and coral carpets of the Paratethys (own observation). It is only very rarely found associated with other Stromboidea except for Tibia dentata (Grateloup 1827).
Weitendorf, Wetzelsdorf (Styrian Basin, Austria); Sámsonháza, Márkháza (Cserhát Mountains, Hungary); Coşteiu de Sus, Lăpugiu de Sus (Transylvanian Basin, Romania); Hrvaćani (southern Pannonian Basin, Bosnia and Herzegovina), Tarnene and Pleven (Carpathian Basin, Bulgaria) (see Harzhauser et al. 2003 for map).
A guest from the east or a home-made western Tethyan element?
Europrotomus schroeckingeri displays a remarkable distribution. From literature references, it is seemingly confined to the Central Paratethys, which is possibly rather a matter of a lack of investigations in adjacent regions. Within the Paratethys it is restricted to the southern basins (Harzhauser et al. 2003). The rare shell is found in Romania, Bulgaria, Hungary, Bosnia and Herzegovina and in the Styrian Basin in Austria. It is unknown from the North Alpine Foreland Basin, the Vienna Basin and the more northern Carpathian Foredeep. During the early Middle Miocene, the southern Paratethys basins, e.g., the Styrian and Pannonian basins, had a direct connection to the proto-Mediterranean Sea, while the northern basins, e.g., the Vienna and Carpathian basins, were fed by a more eastern connection. Both water masses were probably separated by emerged areas that now form the Danube Basin. This assumption is supported by geochemical data on stable isotope composition of mollusc shell aragonite, which clearly indicates strongly deviating water chemistry between these two branches of the Paratethys Sea (Latal et al. 2005). Therefore, the strombid was hindered on its way to the north. In respect to the generally low endemicity of the southern Paratethyan mollusc faunas at that time (Harzhauser and Piller 2007), it may be expected that Europrotomus schroeckingeri was also distributed in the proto-Mediterranean area. Its absence from the fossil record may be explained by the fact that coeval Langhian deposits in the Mediterranean area are rare and mainly represented by deep water deposits (e.g., Mourik et al. 2011). None of the rare Langhian shallow water faunas from the Monte dei Cappuccini in the Turin Mountains (Sacco 1893) and from the Mut Basin in Turkey (Mandic et al. 2004) yielded Europrotomus schroeckingeri.
Only the occurrence of Europrotomus almerai (Crosse 1885) in the Middle Miocene of Spain suggests a wider distribution of the genus. Nevertheless, its sudden appearance and the lack of obvious ancestors might point to immigration from a nearby bioprovince.
Immigration from western Africa would be a realistic scenario. This hypothesis, however, is a hard test as there are no fossil-bearing Lower and Middle Miocene deposits known along the West African coast. The Paleocene molluscan fauna from Nigeria has been discussed by Newton (1905, 1922), Eames (1957) and Adegoke (1977), and from the Gold Coast (= Ghana) by Cox (1952), but although there are stromboideans discussed (Rimellidae. Rostellariidae and Seraphsidae) in those papers, no strombids are mentioned. It is quite unlikely that Europrotomus schroeckingeri arose from one of these stromboidean families. Therefore, no potential West African ancestor can be shown.
Immigration from the East is unlikely as there is also no evidence of E. schroeckingeri in the contemporaneous but always lowly diversified faunas of the Eastern Paratethys (Ilyina 1993). Hence, it would be tempting to explain this erratic appearance by immigration from either the Americas in the west or the proto-Indo-West-Pacific Region in the east. An arrival of Europrotomus from the western biogeographic units of the Central Americas, however, is extremely unlikely in respect to the fossil record (e.g., Jung and Heitz 2001). A connection of the Mediterranean or the Paratethys with the early Indo-Pacific existed during the Early Miocene (Rögl 1998; Harzhauser et al. 2007). Hypothetically, this marine connection would have allowed the immigration of Europrotomus. Nonetheless, it has to be kept in mind that all Oligocene-Miocene mollusc faunas of Arabia, Eastern Africa, Pakistan, India, Java and Borneo lack any clear evidence for a Europrotomus-Euprotomus-related strombid (see Vredenburg 1925; Beets 1941; Abbott 1960; Hoek Ostende et al. 2002; Harzhauser 2007, 2009; Harzhauser et al. 2009). Thus, there is little reason to hypothesize a westward immigration into the Mediterranean area. Moreover, during the Middle Miocene when Europrotomus appears, the eastern route via the Tethys Seaway was already closed or hard to cross (Rögl 1998, Harzhauser et al. 2007).
All the occurrences are concentrated in the southern basins of the Paratethys Sea, which was a northern gulf of the proto-Mediterranean Sea (Rögl 1998; Popov et al. 2004; Harzhauser and Piller 2007). Soon after, the genus vanishes completely from the Paratethys Sea and is unknown from deposits younger than 14–13 Ma. This range coincides conspicuously with the mid-Miocene Climatic Optimum (Zachos et al. 2001), while its sudden decline coincides with the Mid-Miocene climate transition (Shevenell et al. 2004). This climate-related stratigraphic and biogeographic pattern was documented for a wide range of Paratethyan taxa of gastropods and foraminifers (Harzhauser and Piller 2007) as well as bivalves (Harzhauser et al. 2003).
Hypothetical relations and roots
Although Europrotomus can easily be distinguished from other genus level taxa, morphological elements of the last whorl suggest some affinities with the genera to which it is compared above, e.g., Euprotomus, Lentigo, Persististrombus, Sinustrombus, Harpago and Lambis. In his thesis, Latiolais (2003: fig. 1) illustrates a maximum likelihood tree constructed from 325 bp of nuclear histone H3 for numerous species of Strombidae. Unfortunately, in the tree constructed from 640 bp of mitochondrial COI (Latiolais 2003: fig. 2), some of the species are not represented, so these species are also missing in the consensus tree (Latiolais 2003: fig. 3; Latiolais et al. 2006). Based upon the nuclear histone H3 results, Europrotomus gen. nov. may be derived from a Canarium-like ancestor and at the root of the clade that leads to all recent American and West African genera (Lobatus; Persististrombus; Strombus) and also the Indo-Pacific genera Conomurex, Euprotomus, Gibberulus, Harpago, Lambis, Lentigo, Sinustrombus, Thersistrombus and Tricornis (names following Kronenberg et al. 2010/2011). This may be an indication of a Miocene “explosion” of genus level taxa (Williams and Duda 2008).
The proposed relation with a Canarium-like ancestor, however, is highly speculative, as Europrotomus appears abruptly in the fossil record and is restricted to a rather narrow time span during the Middle Miocene. Only few strombid genera are present in the Early Miocene of the Western Tethys. Of these, only Persististrombus is recorded from numerous localities, documenting a continuous occurrence of the lineage from the Oligocene up to the Pliocene (Lozouet and Maestrati 1986; Harzhauser and Kronenberg 2008). A close relation of Persististrombus with Europrotomus, as discussed above, is very unlikely. Similarly, a phylogenetic relation with Dilatilabrum Cossmann, 1904, which occurs as a Palaeogene relic in the Lower Miocene of the Aquitaine Basin in France, can be ruled out. Representatives of Dilatilabrum are characterized by extremely solid shells with wing-like outer lips with straight edges. Finally, a third—still unnamed—strombid genus is known from the Lower Miocene of the Aquitaine Basin in France and the Turin Mountains in Italy. It is represented only by the species “Strombus” mitroparvus Sacco, 1893. This small elongate strombid with strong nodes and a narrow wing might be the earliest species of a lineage that is represented in the Miocene to Pleistocene of the IWP by “Strombus” micklei Ladd, 1972, and “Strombus” blanci Tröndlé & Salvat, 2010 (Ladd 1972; Tröndlé and Salvat 2010). “Strombus” mitroparvus, with its very narrow aperture and an insignificant wing that does not reach the spire, differs fundamentally from Europrotomus and is a very unlikely ancestor candidate.
The Neogene strombid fauna of the proto-Mediterranean and Paratethys seas was dominated by representatives of the Persististrombus lineage. Apart from Dilatilabrum and “Strombus” mitropravus from the Early Miocene, the only other genus present was Europrotomus known solely from the Middle Miocene. It remained rather rare and did not radiate as it is known so far only from a single species, although a second one, viz. Strombus almerai, might have existed in the western Mediterranean.
This taxon has no obvious roots in the fossil record and is unrelated to the known Early Miocene strombids of the entire Tethys Realm. Moreover, it has no direct relation with the modern genera to which it has been assigned in the literature so far. The lack of potential ancestor species in the Lower Miocene deposits of Eurasia might indicate that Europrotomus schroeckingeri is an immigrant, which expanded its tropical distribution area toward the north during the warm Langhian. As the connection into the early Indo-Pacific was already ceasing during the Middle Miocene, this passage is an unlikely immigration route. Hence, an arrival from the west would be more realistic. Especially the tropical coasts of West Africa might have acted as source area. This ad-hoc hypothesis, however, is hard to test because of the lack of Miocene faunas in West Africa. Some support for this hypothesis is a Pleistocene pendent scenario within the Persististrombus lineage. With the Pliocene cooling, this thermophilic strombid retreated from the Mediterranean Sea and survived as Persististrombus latus (Gmelin 1791) along the coasts of West Africa. From there, it re-entered the Mediterranean during the Marine Isotope Stages 7 and 5 (De Torres et al. 2009) and probably also during MIS 3 (Rögl et al. 1997; Zazo et al. 1984).
The case of Europrotomus, with its superficial similarities with extant IWP-genera, clearly documents the negative impact of outdated genus-concepts on biogeography and palaeogeography conclusions.
We would like to thank Anton and Thomas Breitenberger, Bad Vöslau and Pottenstein, Austria, for donating material to both NHMW and Gijs C. Kronenberg; this latter specimen will be donated to NCBNaturalis at some point in the future. Dr. Bernard Landau, Albufeira, Portugal, and an anonymous reviewer carefully read the manuscript and provided valuable suggestions for improvement.