Placodontiformes Neenan et al., 2013
Placodontia Cope, 1871
Placodontoidea Nopcsa, 1923
Paraplacodus Peyer, 1931a, 1931b
Paraplacodus broilii Peyer, 1931a, 1931b
Material: maxilla fragment (MTM VER 2019.124.)
Age: Trinodosus Zone, late Anisian (Middle Triassic) (Vörös et al. 2003)
Locality: Forrás Hill, Felsőörs, Balaton Highland (Transdanubian Range) (Fig. 1)
Stratigraphic range and facies: Felsőörs Limestone Formation Bed 92; well-bedded, laminated brownish grey limestone with interbedding yellow clay (Haas 1985; Vörös et al. 2003; Fig. 2). This sedimentary unit corresponds to a deep water pelagic facies (Haas 1985).
Description: The maxilla fragment is poorly preserved with only a small, ventral part of the lateral wall (anteroposterior length: 2.8 cm), and its processes connecting to the surrounding cranial elements are missing (Fig. 3a). It contains four well-preserved teeth with posteriorly increasing size in the tooth row. Directly below the fourth functional tooth, a replacement tooth can be observed (Fig. 3b). The enamel is black and shiny. In occlusal view, the teeth have rounded to rectangular shape, and the first tooth is particularly more expanded labiolingually than mesiodistally. The occlusal surface on the first and second teeth is rounded on the labial half of the crown, whereas lingually there is a shoulder-like depression with rough surface (Fig. 3c). The third and fourth teeth lack this depression but have a blunt, worn crown with a mesiodistally directed groove occlusally, though their overall morphology was originally probably similar to that of the first two teeth (Fig. 3c).
Comparisons: There are no useful characters preserved on the bone itself but the fragmentary maxilla can be easily placed within Placodontoidea based on the rectangular shape of the characteristic teeth. The size of the teeth is similar to that of Paraplacodus broilii Peyer 1931a, which has relatively much smaller maxillary teeth than Placodus gigas Agassiz 1833-1843. The more labiolingually expanded appearance of the teeth is observable in Paraplacodus, while the teeth of Placodus are rather square shaped except for the first tooth. The shoulder-like depression on the lingual side of the teeth in the Felsőörs specimen is typical for Paraplacodus (Mazin 1989; Rieppel 2000), being more pronounced on the anterior teeth and disappearing gradually with tooth wear posteriorly in the tooth row. However, similar depression can occur on the unworn maxillary teeth of Placodus as well (e.g. SMF R 362), but that is not a shoulder-like depression but rather a triangular surface with three main grooves. In labial view, Paraplacodus teeth have slightly conical shape with large tooth crown height, in contrast to the flatter, lower crowns of Placodus (Mazin 1989; Rieppel 2000). Though the tooth crowns in the Felsőörs maxilla fragment are apparently also flattened like in Placodus, this can be attributed to tooth wear. Thus, the Felsőörs maxilla fragment can be identified as Paraplacodus broilii based on morphological features of its teeth.
Cyamodontoidea Nopcsa, 1923
Cyamodontida Nopcsa, 1923
Cyamodus Meyer, 1863
Material: maxilla (MTM PAL 2019.227.1.), palatine (MTM PAL 2019.228.1.), dentary (MTM PAL 2019.229.1.), 85 isolated teeth (MTM VER 2013.15., MTM VER 2019.15. ─ 2019.99.)
Age: late Ladinian (Middle Triassic) (Nagy and Nagy 1976; Török 1998)
Locality: Somssich Hill, Villány, Villány Mountains (Fig. 1)
Stratigraphic range and facies: the Templomhegy Dolomite Member of the Csukma Dolomite Formation is characterised by four lithotypes: dolomite; dolomarl; reddish calcareous mudstone and claystone; sandstone (Botfalvai et al. 2019; Fig. 2). This formation corresponds to a subtidal to peritidal zone of an inner ramp depositing in a shelf-lagoon (Török 2000; Haas 2001; Botfalvai et al. 2019).
Maxilla: The 6.3 cm long maxilla fragment contains an oval shaped functional, as well as a replacement tooth (Fig. 4a, b). Only the palatal process is preserved, and the other processes for connecting other cranial bones are missing. The length/width ratio of the functional tooth is 1.3 cm/1.05 cm = 1.238. The enamel surface is shiny with some shallow pits, but the original ornamentation on its surface cannot be observed. There is a bulge on the middle of the occlusal surface of the 5-mm-high crown. The replacement tooth is 2–3 mm thick and has shifted laterally due to diagenetic processes.
Palatine: A left palatine fragment has a 1-cm-high medial margin preserved. This part of the palatine is in the sagittal plane for connection to the right palatine. Ventrally, the bone bears a larger posterior and a smaller anterior tooth, the length/width ratio of which are 2.5/1.6 cm = 1.56 and 0.85/0.65 cm = 1.3, respectively (Fig. 4c, d). The larger tooth is emplaced directly next to the sagittal plane, but the distal part of the tooth turns in labial direction. The smaller tooth is very close to the larger one.
The smaller tooth is oval-shaped with domed tooth crown. It becomes slightly pointed mesiodistally, and its labial side is convex, while the lingual is straight. In the middle of the crown, there is a circular, 3-mm-diameter bulge surrounded by small pits. The enamel is shiny and smooth, and no original ornamentation can be observed.
The larger tooth is much flatter, but its appearance is similar to that of the smaller one. The enamel is shiny; however, the convex labial part of the crown is smooth and worn, while its lingual part is more pitted. Due to diagenetic alteration, the teeth are slightly misplaced from their original positions.
Dentary: A 5.5-cm-long right dentary fragment contains two teeth (Fig. 4e–g). Anteriorly, the dentary preserves only the posterior part of the symphysis and the small portion of bone on which the teeth are sitting.
The smaller tooth has an oval-shaped and domed crown with a 1/0.8 cm = 1.25 length/width ratio. It bears a 0.2-cm-diameter bulge centrally. The enamel surfaces of the teeth are pitted showing the original texture of the crown surface, but in a great part of the crown, this surface is slightly eroded due to feeding. There is a replacement tooth under the smaller tooth, which has a similar appearance and size ratio.
The larger tooth is mesiodistally elongated bean–shaped with the lingual margin being the concave side. The length/width ratio is 3.2 cm/1.7 cm = 1.88. The tooth crown is flat and is covered with pits similar to those on the smaller tooth. These pits can be the traces of the original ornamentation, namely radial striations that have been eroded away.
Isolated teeth: Of the preserved 85 isolated teeth 16 specimens represent one (referred to here as first) morphotype that are flat and more elongated longitudinally (MTM VER 2013.15., MTM VER 2019.27.-2019.42.; Fig. 5a, b). Their length/width ratio varies between 1.8 cm/1.2 cm = 1.5 and 3.1 cm/1.8 cm = 1.7. These teeth have a bean-like shape with a strongly convex and a slightly concave or in some cases straight side. Tooth crowns become slightly pointed mesiodistally and many pits and radial striations can be observed on the enamel. There is no bulge on the tooth crown. This tooth type can be identified as the last dentary tooth.
Twelve specimens of enlarged teeth can be referred to a second morphotype (MTM VER 2019.15.-2019.26.). These teeth are large and have a slightly oval or circle shape in occlusal view; their length/width ratios are relatively low, e.g. 1.9/1.45 cm = 1.31 (Fig. 5c) or 2.8/1.9 cm = 1.47 (Fig. 5d). They are slightly pointed distally and expanded labiolingually. The tooth crown is flat or slightly domed with low height. Macrowear features can be observed almost only on the convex part of the occlusal surface, and the dentine is not exposed. On the well-preserved teeth, a small circle-like bulge in the middle of the crown as well as some fine radial striations can be observed. Furthermore, small shallow radially positioned pits are also present on the enamel. Enamel thickness, as visible at the broken margins, varies between 0.4 and 1.1 mm. In cyamodontoid placodonts, enlarged teeth occur in the last position of the dentary and the palatine (Rieppel 2001). Based on the transversally slightly expanded shape, this second morphotype can be the last (second) palatine tooth because the dentary tooth is relatively narrower transversally.
Thirteen button-like teeth represent the third morphotype (MTM VER 2019.43.-2019.55.; Fig. 5e–h). Their crown has a circular or slightly oval shape in occlusal view, the length/width ratio varies between 0.5 cm/0.4 cm = 1.25 and 1.2 cm/0.9 cm = 1.3. The crowns are strongly domed, only the worn teeth can be relatively flat. On the well-preserved crowns, a bulge surrounded by small pits can be observed. However, these pits are caused by tooth wear. There are some teeth where the enamel is smooth and there is no ornamentation. It is hard to determine the position of these type of teeth because the maxillary, the anterior palatal and anterior dentary teeth in cyamodontids are usually similar in shape, sometimes having smaller or larger teeth in the lower and upper jaws.
In the material, there are five very small fragmentary teeth (MTM VER 2019.56., MTM VER 2019.57., MTM VER 2019.58., MTM VER 2019.59., MTM VER 2019.60.; Fig. 5i, j). These are slightly triangular in occlusal view and differ from the other morphotypes. They have a more elongated shape; moreover, they are strongly pointed mesially or distally. A bulge can be observed in the middle of the crown similar to the other morphotypes. These forms are probably maxillary or anterior dentary teeth.
The rest of the 87 isolated teeth has not been assigned to either of the abovementioned morphotypes.
Comparisons: The oval shape of the Villány teeth is most similar to those of the Cyamodontoidea (Rieppel 2001; Crofts et al. 2015). The last palatine teeth differ from the much larger and rhomboid palatine teeth of Macroplacus raeticus Schubert-Klempnauer, 1975 (BSP 1967 I 324), and from the subcircular shaped and higher crowned teeth of Protenodontosaurus italicus Pinna, 1990 (MFSN 1819GP). Furthermore, Henodus chelyops Huene, 1936 (GPIT/RE/07290) and Parahenodus atancensis Chaves, Ortega et Pérez-García, 2018 (MUPA ATZ0104), are different from those from Villány, in having much smaller, strongly elongated and flattened teeth with a longitudinal central depression (Reif and Stein 1999; Chaves et al. 2018). The button-like circular shape of maxillary (or first palatine) teeth from Villány are distinguishable from the ovoid shaped teeth of Protenodontosaurus and from the slightly oval shaped teeth of Macroplacus. Furthermore, in these species, no bulge is present centrally on the tooth crown. The Villány maxillary and palatine teeth differ from the more complex crown morphology of Placochelys placodonta and Psephoderma alpinum Meyer, 1858. The palatine teeth of these species are slightly elongated and pointed distally. On the palatine teeth of Psephoderma, there is a broad crescent-shaped depression ornamented labially with deep radial furrows. Teeth of Placochelys preserved in the paratype skull (MB.R. 1765) have two main domed surfaces separated by a deep, narrow groove wrinkled at its mesial and distal ends. The Villány maxillary (or first palatine) teeth are also distinct from those of Psephoderma in being elongated, mesially and distally pointed and ornamented with a depression and deep striations. They also differ from the stockier maxillary teeth of Placochelys that have a crescent-shape depression occlusally.
The Villány teeth are most similar to those of Cyamodus based on their outline and occlusal ornamentation. The last palatine teeth of Cyamodus muensteri Agassiz, 1839 (BSP As VII 1210) and Cyamodus rostratus Münster, 1839 (SMNS 17403) are slightly pointed mesiodistally, but they are more convex transversally compared with the Villány specimens. Cyamodus kuhnschnyderi Nosotti et Pinna, 1993 and Cyamodus hildegardis Peyer, 1931b have nearly circular palatine teeth. The teeth of these four species are much more robust and have higher tooth crowns than the Villány specimens. Tooth crowns are usually more or less worn in most Cyamodus species; thus, the original morphology can be studied only in a few specimens. Radial striations on the palatine teeth, as seen on the Villány teeth, can be observed in C. kuhnschnyderi, C. rostratus and C. hildegardis, while in C. muensteri, there is no ornamentation. On the unworn teeth of C. kuhnschnyderi (SMNS 15855) and Cyamodus sp. (SMF R 4039), there is a longitudinally deep, short groove in the middle of the crown from which wrinkles extend radially towards both ends of the crown. Furthermore, the whole occlusal surface of the teeth is covered by strong, deep striations. Therefore, the Villány palatine teeth are distinct from those of C. kuhnschnyderi because they have only fine striations and a small bulge in the middle of the crown. Such a bulge can be observed, for example, in younger individuals of C. hildegardis (e.g. PIMUZ T58).
Maxillary (or first palatine) teeth (the third morphotype) have similar circular or button-like appearance in all Cyamodus species (e.g. Rieppel 2001), similar to the Villány specimens. In this tooth type, a bulge also appears in C. hildegardis and two Cyamodus sp. (SMF R 4039 and SMF R 4040) specimens. Dentary teeth of Cyamodus are morphologically similar to palatine and maxillary teeth; however, their last teeth are slightly more elongated mesiodistally, a condition also seen in the Villány teeth. The bean-shaped, enlarged dentary tooth is similar to Cyamodus sp. from Slovenia (Buffetaut and Novak 2008), but the Hungarian form does not have an elongate (“bowl shaped”) depression on the occlusal surface. MTM VER 2019.56. and MTM VER 2019.57. with their more elongated and pointed shape are distinguished from all Cyamodus species and similar shape can only be observed in the case of the maxillary teeth of Protenodontosaurus.
The cyamodontid form from the Villány Mountains is comparable with the genus Cyamodus because of some tooth crown morphological features (e.g. bulge and striations on the crown, the button-like appearance of the maxillary teeth). However, due to the dental wear, the morphology cannot be examined in most species, and the shape of the teeth is varied within the species. Therefore a more precise (species-level) identification is not possible, and based on the teeth, the abovementioned placodont remains from Villány are identified as Cyamodus sp. in the present paper.
Dermal armour fragments: Eleven fragments can be referred to the dermal armour. They are covered by purple crust (caused by diagenetic processes), and the external bone surfaces of the plates are usually pitted. The greatest length of the most complete dermal armour fragment (MTM PAL 2019.230.1.) is 9.9 cm. It is composed of various small (0.9 × 0.9 cm length-width) pentagonal elements (Fig. 6a) that have a similar thickness of app. 0.3 cm. The whole fragment is slightly bent, but this might be due to diagenetic processes.
In case of the 7.9 cm long MTM PAL 2019.231.1. armour fragment, four (2.25 × 2.5 cm length-width) hexagonal or heptagonal flat elements are fused (Fig. 6b, c). One of these elements is surrounded by smaller (1 × 0.7 cm length-width) elements with similar shape. The polygonal outline of the individual armour plates can be observed only from one side of the armour blocks that is most probably the ventral side. The dorsal side of the dermal armour block has a fine but recognisable ornamentation (schematic drawing of Fig. 6b). Centrally, they bear a shallow, most probably antero-posteriorly oriented crest or protuberance from where shallow furrows extend radially towards the margin of the elements. No ornamentation can be observed on the elements that would extend onto the neighbouring polygonal armour plates.
The MTM VER 2019.100. associated block consists of two intact hexagonal flat elements with similar size and a bigger fragmented one (Fig. 6d). The thickness is 3 mm. The specimens MTM VER 2019.101. and the MTM VER 2019.102. are also associated blocks, but they are not well preserved, and the shape of the individual elements is not determinable (Fig. 6e, f).
Five isolated fragments (MTM PAL 2019.232.1., MTM VER 2019.103., MTM VER 2019.104., MTM VER 2019.105., MTM VER 2019.106.) with various sizes bear two parallel ridges (with app. 1 mm height) dorsally in the middle of the plate, where the distance is 2–5 mm between the ridges (Fig. 6g–j), and there is one fragment without parallel ridges (MTM VER 2019.107.; Fig. 6k). Their original shape cannot be determined; their thickness is app. 2 mm. The ornamentation can be observed as shallow furrows on one of their sides (probably dorsal, similarly to MTM PAL 2019.232.1.). MTM VER 2019.108. differs from the other isolated armour plates because it has a circular shape and it is convex dorsally and concave ventrally. It also has two parallel ridges on its dorsal surface.
Comparisons: The relatively flat dorsal surface of the dermal armour fragments differs from the conical or pyramidal armour elements of Placochelys placodonta, where this type of elements are ornamented with 8–10 ridges and grooves (Kormos 1917). However, on the edge of the carapace fragment of Placochelys, there are also small, flat, polygonal elements similar to the one from Villány. Psephosaurus suevicus Fraas, 1896 has also morphologically similar conical armour elements, as does Placochelys, too, and these elements are polygonal or rounded in ventral view in both taxa (Rieppel 2002a). However, Psephosaurus has flattened, pentagonal or hexagonal elements varying in size (15–25 mm), and these elements are ornamented with radial furrows. Some armour plates described as Psephosaurus also have a depression in the middle of the dorsal side (e.g. SMNS 2091). In contrast, the Villány armour plates have no such conical ornamentation but the furrows are similar to Psephosaurus. Flattened armour plates are not present in Cyamodus kuhnschnyderi and it has enlarged, keeled, octagonal armour plates with rectangular dorsolateral ridge, but pyramidal- and triangular-shaped elements also occur (Rieppel 2002a). In the case of C. hildegardis, the tubercular armour plates are only known in two dimensions, laying on the lateral margin of the carapace (Rieppel 2002a). C. hildegardis has ovoid, keeled elements (e.g. PIMUZ T58; e.g. Pinna 1980; Scheyer 2010), and some pits can be observed on the dorsal side, while ventrally it is rough and convex.
The carapace of Cyamodus orientalis Wang et al., 2019 and Psephoderma alpinum is built up by flat elements (Mazin and Pinna 1993; Rieppel 2002a; Wang et al. 2019). The polygonal, irregular-shaped and different-sized specimens from Villány are distinguishable from the regular hexagonal (sometimes pentagonal) armour plates of Psephoderma and from the hexagonal, but irregular-shaped and -sized armour plates of C. orientalis. In Psephoderma, three rows of armour plates have slightly bending parasagittal crests extending across the whole dorsal armour (Mazin and Pinna 1993; Rieppel 2002a). Cyamodus orientalis has no such crest (Wang et al. 2019). In contrast, the individual Villány armour plates have two parallel ridges that are sharper, lower and narrower than the crests in Psephoderma. C. orientalis has a shallow radial structure dorsally to form a polygonal texture inside each armour plate, while on the dorsal side of the Psephoderma armour plates, a shallow, circular depression or emmersion can be observed that is surrounded by a circular groove (e.g. PIMUZ A500) and deep furrows appear on the entire dorsal surface of some of the armour plates (e.g. BSP 1963 VI 176 and BSP 1966 XXIX 32).
The armour plates of the Villány placodont are similar in shape to those of Psephoderma alpinum and Cyamodus orientalis. The two parallel ridges (Fig. 6g–j) on the Villány specimens appear to be a unique feature among known placodonts. The species-level identification of these dermal armour is, however, quite difficult due to the poor preservation of armour plates of the genus Cyamodus, as well as to their scarcity in the fossil record. In addition, some features, such as the flat, polygonal morphology and the shallow radially oriented ridges on the dorsal surface of the armour plates appear in several species. Thus, we tentatively refer these armour plates here as Cyamodontoidea indet. until more complete material will be available.
Vertebrae: The four vertebral centra are preserved without neural arches and are slightly compressed (Fig. 7a–f). The vertebral centrum is slightly elongated (length/width ratio varies between 2.5/2.25 cm = 1.11 and 1.35/0.6 cm = 2.25), amphicoelous and bears a depression laterodorsally. The largest specimen (MTM VER 2019.120.) is 2.5 cm long and 2.25 cm wide with massive appearance probably representing a dorsal vertebra (Fig. 7a–c). A smaller (1.35 cm × 0.6 cm) elongated centrum (MTM VER 2019.123.) is interpreted as a caudal vertebra (Fig. 7f) because this type of vertebra in placodonts is more elongated and slender, unlike the other type.
Humerus: The 5.8-cm-long right humerus (MTM VER 2013.11.) has a slight curvature (Fig. 7g–i). The distal articular surface is lateromedially extended and dorsoventrally flattened granting a fan-like appearance to it. The midshaft area consists of a slightly concave preaxial margin and a more concave postaxial margin. The dorsal side is almost completely straight in lateral view, while the ventral side is only curved proximally because of the protruding ridge.
Comparisons: The humerus referred here to placodonts (MTM VER 2013.11.) differs from that of Paraplacodus because the latter has the same width of the proximal and distal heads (Rieppel 2000; Klein and Hagdorn 2014). Its preaxial side is slightly concave or straight similarly to that of Placodus and Cyamodus (Rieppel 1995; Klein and Hagdorn 2014), but the fan-like widening of the distal head of the humerus MTM VER 2013.11. is not present in these forms. Furthermore, the humeri of Placodus and Cyamodus have similar morphology, and distinguishing them is based on size and stratigraphy (Vogt 1983; Rieppel 1995).
The vertebrae of the Villány placodont with amphicoelous centra are distinguishable from the slightly amphicoelous or platycoelous vertebrae of nothosaurs (Rieppel and Wild 1996). A depression laterally on the dorsal side of Villány specimens can be observed in placodonts, for example in the case of SMNS 54547 Placodus gigas and SMNS 59825 Cyamodus. Vertebral centra are not diagnostic at species level, but the neural arches can be useful for taxonomic purposes (Klein and Scheyer 2014; During et al. 2017).
Since non-armour plate postcranial elements of placodonts are usually difficult to diagnose at generic or species level, thus these elements are referred to as Placodontia indet. until more complete material will be available.
Cyamodontoidea Nopcsa, 1923
Placochelyda Romer, 1956
Placochelys Jaekel, 1902a, 1902b
Placochelys placodonta Jaekel, 1902a, 1902b
Material: right dentary fragment (MBFSZ Ob.2323, Vt.3), two isolated teeth (MBFSZ Ob.2323, Vt.3)
Remarks: Though inventoried under the same number, these specimens do not belong to the either the holotype or paratype (see above in Material and methods)
Age: Late Triassic, Carnian
Locality: Jeruzsálem Hill, Bakony Mountains (Transdanubian Range) (Jaekel 1902b, 1907) (Fig. 1)
Stratigraphic range and facies: Veszprém Marl Formation built up of grey clay marl, marl or silty marl with carbonate interbeddings (Fig. 2). The Veszprém Marl Formation represents a basin and slope facies deposited in fragmented subbasins between carbonate platforms, with limited connections to the open sea (Csillag and Haas 1993). Tamás Budai (pers. comm. to A.Ő.) suggested that the rocks embedding the Placochelys finds from Veszprém might not have belonged to the Veszprém Marl Formation but rather to the overlying (also Carnian) Sándorhegy Limestone Formation. Both formations represent different phases of the filling up of the basin, with the Sándorhegy Limestone Formation being the later in this process, deposited in a more shallow environment, with a transition from mainly terrigenous to dominantly carbonate sedimentation.
This argument still needs to be addressed but is out of the scope of the present paper.
Dentary: A 3.5-cm-long right dentary fragment (MBFSZ Ob.2323, Vt.3) has the last enlarged tooth (Fig. 8a–c). The part of the bone under the tooth is preserved to the base of the Meckel’s groove, the splenial is missing. The anterior part of the Meckelian canal is triangular-shaped in cross-section. The tooth is brownish, only slightly worn and well preserved; thus, the original morphology of the occlusal surface can be studied. The tooth has an elongated oval shape (length/width = 1.6), and it is more narrow mesially (Fig. 8c). In occlusal view, the labial side is more convex than the lingual one. The tooth crown consists of two distinct domed surfaces separated by a mesiodistal depression. Of these two “peaks”, the labial one is lower and is situated more mesially on the crown, while the higher, lingual one rises more distally.
Isolated teeth: One isolated tooth (MBFSZ Ob.2323, Vt.3, Fig. 8d) can be identified as dentary tooth and has the same ratios (length/width = 1.61) and similar morphology as the one in the mandible. This specimen is more fragmented but quite well preserved. The main difference is that there are well-visible radial striations on the entire crown which become finer basally.
There is another isolated tooth (Fig. 8e) under the same inventory number that is probably a maxillary tooth, but its more exact position cannot be determined. In occlusal view, it has a slightly elongated angular shape with a straight lingual and a convex labial side. On the lingual part of the occlusal surface, there is a crescent-shaped, mesiodistally extending depression, which has a straight lingual and a convex labial side. Inside this depression, some fine grooves run labiolingually; they seem to be slightly worn.
Comparisons: The shape of the abovementioned enlarged dentary teeth is similar to those of the holotype. The length/width ratio is almost the same, though the isolated dentary tooth is slightly more elongated. The enlarged dentary teeth of the holotype are heavily worn, and the dentine is exposed in most parts of the occlusal surface. Unlike in the isolated ones, the original tooth morphology such as striations, mesiodistal depression and domed surfaces cannot be observed on the dentary teeth.
The other small isolated tooth shows similarities with the maxillary teeth of the holotype skull. The first two teeth in the maxilla have a crescent depression on the lingual side like the isolated one; however, their shape is convex both labially and lingually. The third maxillary tooth of the skull is worn and has a straight lingual side similar to the isolated maxilla tooth. The size of the isolated tooth is almost the same as the first maxillary tooth of the holotype skull.
Cyamodontoidea Nopcsa, 1923
Material: fragmentary isolated tooth (MBFSZ T.1242)
Remarks: The specimen was mentioned as “Placochelys (?) palatine tooth” by Böckh and Lóczy (1912), citing Jaekel’s determination and has been inventoried as such. This was later modified to Placodus sp. by an unknown person in the catalogue.
Age: Late Triassic, Norian-Rhaetian
Locality: Akasztó Hill, Keszthely Mountains (Transdanubian Range) (Fig. 1)
Stratigraphic range and facies: Kössen Formation built up by dark grey clay marl and marl, formed in a closed, oxygen-depleted basin behind the Dachstein platform (Böckh and Lóczy 1912; Haas 1993; Fig. 2). Towards the platform, more and more limestone intercalations occur in the succession.
Description: The isolated tooth is a 1.8-cm-long and 1.4-cm-wide fragment, which has a pointed mesial or distal side (Fig. 9a). Occlusally, most of the enamel is missing; thus, the dentine is exposed. On the intact part of the enamel, a depression can be observed, which is a worn surface. The original shape of the tooth is probably non-rectangular and elongated with a relatively low tooth crown (0.35 cm). Its size and shape refers to an enlarged palatine or dentary tooth.
Comparison: Because of the non-rectangular, oval or elongated shape, this tooth can be well distinguished from the teeth of placodontoids (e.g. Placodus and Paraplacodus) (Mazin 1989). A pointed side can be observed in Placochelys and Psephoderma and also in some Villány specimens, but in Psephoderma, these teeth are more pointed than in Placochelys (e.g. PIMUZ A/III4495 Psephoderma alpinum and PIMUZ A/III4493 P. alpinum). Very similar tooth fragments have been described earlier under distinct names, such as Placodus sp. (PIMUZ A/III0497), aff. Placochelys (PIMUZ A/III0879; Fig. 9b) and Placochelys stoppanii (BSP As I 1468; a synonym of Psephoderma alpinum; Fig. 9c). Based on the age (Norian-Rhaetian) and the lithostratigraphy (Kössen Formation), the tooth from Rezi might have belonged to Psephoderma; however, this fragment does not allow a genus-level identification.