Janosikia ulmensis (Čerňanský & Klembara & Smith, 2016)

Čerňanský, Andrej, Klembara, Jozef & Smith, Krister T., 2016, Fossil lizard from central Europe resolves the origin of large body size and herbivory in giant Canary Island lacertids, Zoological Journal of the Linnean Society 176 (4), pp. 861-877 : 864-873

JANOSIKIA ULMENSIS ( GERHARDT, 1903) COMB. NOV.

FIGURES 1B , 3–7

1903 Ophisaurus ulmensis – Gerhardt, p. 5, fig. 1 – 5. 1983 Ophisaurus moguntinus – Estes, p. 141 [in part, SMNS specimens].

Newly referred specimens

SMNS 96582 ( Fig. 3A ), well-preserved adult individual, consisting of premaxilla, maxilla, left nasal, prefrontal, palpebral, frontal, parietal, supratemporal, squamosal, pterygoid, mandible (dentary, coronoid, angular, surangular), supraocular osteoderm, interclavicle, humerus, zeugopodium, phalanx, vertebrae, and ribs; SMNS 96579 ( Fig. 4 ), smaller partial skeleton representing a younger ontogenetic stage (probably late juvenile), and consisting of the premaxilla (covered in sediment under other bones), maxillae, nasals, parietal, pterygoid, ectopterygoid, postorbitofrontals, jugal,?squamosal,?otooccipital, basioccipital (+ basisphenoid?), quadrate, mandible (dentary, coronoids, surangular, angular, articular), supraocular osteoderm, vertebrae, and ribs; SMNS 96581, larger specimen consisting of dentary, jugal, and scapula; SMNS 96575, mandible; SMNS 95455 and 95456, dentaries; SMNS 95457, maxilla; and SNMS 95460, braincase.

Locality and horizon

Type locality of Ophisaurus ulmensis Gerhardt, 1903 , north-west of Ulm, Germany. The fossils derive from white or grey calcareous marls of the of the Lower Freshwater Molasse, dated to the middle Agenian (MN 2a), lower Miocene ( Heizmann et al., 1989).

Taxonomical comment

The newly referred jaws are identical to the type material of Ophisaurus ulmensis described from the same locality ( Gerhardt, 1903; Fig. 1B ): in tooth count, tooth morphology, presence of a sulcus dentalis, and the absence of splenial spine on the subdental shelf of the dentary. This species has been considered an anguid ( Gerhardt, 1903) or a cordylid ( Böhme & Ilg, 2003), but these assignments are untenable given the new specimens. Ophisaurus ulmensis lacks the following derived characters of Anguidae : splenial spine (the splenial anterior inferior alveolar foramen is located between the splenial and the dentary in Anguidae ), Meckel’s groove opens ventrally in the anterior region (not medially for most of length), retroarticular process wider (relative to glenoid fossa), distinct surangular process, interparietal scute overlaps frontal, supraocular osteoderms insert into sulcus along frontal supraorbital margin, and anteriorly located medial ridge of jugal ( Estes, de Queiroz & Gauthier, 1988; Gauthier et al., 2012; Černˇ anský, Smith & Klembara, 2014). It also lacks the following derived characters of Cordylidae : pterygoid teeth absent, medial ridge of jugal located posteriorly on postorbital process, dentary terminates clearly posteriorly to the level of coronoid apex on lateral face of mandible, transversely bicuspid teeth (presence of cusps labialis and lingualis on tooth crown), ventral processes of the parietal bone, and absence of occipital scute ( Estes et al., 1988; Kosma, 2004; Gauthier et al., 2012; Černˇ anský et al., 2014).

In contrast, the new specimens show the following synapomorphies of Lacertidae : sulcus dentalis, lateral overlap of the posterodorsal margin of the dentary by the coronoid, closure of the supratemporal fenestra by the postorbitofrontal, interparietal scute does not reach frontal bone ( Gauthier et al., 2012), and cristae cranii parietalis meet medially to form a sulcus. Thus, reference to Lacertidae is strongly supported.

Revised diagnosis

Very similar to Pseudeumeces cadurcensis but distinguished from it by the following characters: larger size; less ventrally convex dentary; angular process of dentary reduced, not reaching level of the coronoid apex; ratio of anterior and posterior region of frontal 3: 4, rather than 1: 2; stronger ornamentation; interparietal scute smaller and narrower than large occipital scute (in P. cadurcensis , the interparietal is large; see Augé & Hervet, 2009). Distinguished from extant gallotiine lizards by the presence of amblyodont dentition (sensu Hoffstetter, 1944).

Description

The skull length of Janosikia ulmensis comb. nov. is estimated to be 44 mm. Such a large skull size is known among extant lacertids in Gallotia , although some large individiuals of Timon lepidus can also reach this size (J.-C. Rage, pers. comm. 2015).

Cranial bones

The premaxilla is poorly preserved in the larger specimen (SMNS 96582; Fig. 5L ). CT reconstructions reveal the premaxilla in the smaller specimen (SMNS 96579), which is covered by other bones ( Fig. 6C, D ). It has seven tooth positions (five teeth are preserved). The maxillary processes are well developed, but relatively shorter in the smaller specimen than in the larger one. The nasal process is thin.

Comparison: The maxillary processes are usually reduced in members of Gallotia . The maxillary pro- cesses are reduced in Acantodactylus too, probably independently. They are of normal size in Psammodromus and many other lacertids. The premaxillary tooth count in Gallotia is usually seven, whereas in Psammodromus and Lacertinae it is nine or more.

The maxilla has around 16 teeth. The dorsal region of the tall facial process is arched and curves medially ( Fig. 5L–N ). Its external surface bears several osteoderms. The anterior margin of the facial process rises upwards to form the posterior margin of the external naris. This margin is continuous with the crista lateralis of the premaxillary process. Posteriorly it continues into the broad posterior process. The external surface is pierced by six labial foramina. In medial view, the carina maxillaris is well developed, tall. The superior alveolar foramen is located approximately at the level of the sixth tooth from the back.

The nasals are paired and grow wider anteriorly ( Fig. 5H, I ). A long pointed medial process is present anteriorly. The dorsal surface of the bone is ornament- ed, evincing a groove that marks the boundary between the prefrontal and frontonasal scutes. Ventrally the bone is slightly concave.

The prefrontal ( Fig. 5F, G ) has a long posterior process, the ventral surface of which forms the orbital surface. The dorsal surface possesses ornamentation, whereas the internal surface is excavated for the nasal capsule.

The palpebral is F-shaped ( Fig. 5J, K ). In the anterodorsal region, a facet for articulation with the prefrontal is present. The whole dorsal surface is slightly convex. The posterior end forms a process. Two blunt flanges are present, directed medially from the main body of the palpebral.

The frontals are paired in SMNS 96579, but CT reconstructions show partial fusion in the larger SMNS 96582. The anterior margin of the frontal bears two pairs of facets: an ovoid, medial pair for the nasals, and a wedge-shaped lateral pair for maxillae ( Fig. 5D ). The lateral margins are curved to form the orbit. The paired frontoparietal scutes, which are delineated from the frontal scute by the sulcus interfacialis, are anteriorly convex. The anterior portion of the frontal bone – that is, the portion anterior to the sulcus interfacialis – is nearly rectangular, its width increasing only slightly anteriorly. It is only slightly longer than the posterior portion of the frontal bone, which expands posteriorly. The ratio of the length of the posterior portion of the frontal to that of the anterior portion is 3: 4. The posterior margin shows strong interdigitations for the parietal. The dorsal surface is covered by an osteodermal crust. On the ventral surface, the cristae cranii frontalis are well developed and form strong subolfactory processes ( Fig. 5E ).

Comparison: Paired frontals are typical for members of Gallotiinae ( Arnold, 1973) ; however, there is a tendency towards fusion in adults of Gallotia atlantica , G. caesaris , G. galloti , and G. stehlini ( Barahona et al., 2000) . In most examined members of Lacertinae ( Acanthodactylus , Anatololacerta , Dalmatolacerta , Lacerta viridis , or Podarcis ), the length ratio of the posterior to anterior portions of the frontal is 1: 2, and in some cases nearly 1: 3: that is, the anterior region is much longer. In Timon lepidus , however, the ratio is 1: 1 (Černˇ anský, 2010). The ratio 3: 4 was found only in Gallotinae.

The parietal is a large element with elongate supratemporal processes ( Fig. 5A, B ). The right one is broken in SMNS 96582. The tip of the left one is also missing, but it left an impression in the sediment. The processes curve slightly laterally. Their bases are broad, but they taper distally. The parietal table is rectangular, longer than it is wide, and covered by an osteodermal crust. The centrally located interparietal scute contains the parietal foramen; it is rhomboidal with an elongate posterior portion. The triangular occipital scute is long and posteriorly wide. The anteri- or margin shows interdigitations for the frontal, and a pair of triangular parietal tabs project anteriorly in SMNS 96579 (they appear to be damaged in SMNS 96582). Ventrally, the cristae cranii parietalis originate from the anterolateral corners of the parietal and converge posteromedially. They diminish posteriorly but continue to the end of the bone. A very narrow parietal fossa is located between them on the posterior midline.

Comparison: The supratemporal processes in Lacertini are usually short ( Estes et al., 1988). The long supratemporal process are present among extant members of Gallotiinae , but also among the tribe Eremiadini (with more advanced skull morphology; Arnold, 1989) and in some species of Podarcis ( Klemmer, 1957) . The cristae cranii parietalis are posteriorly in contact, forming a median sulcus. This character occurs in most lacertids ( Peters, 1962); however, in many members of Lacertinae (e.g. Podarcis , Zootoca , Dalmatolacerta , or Acanthodactylus ), the cristae do not form a sulcus and are not connected centrally (see Klemmer, 1957). A relatively short, narrow interparietal scute and long, wide occipital scute are found in Gallotia (sometimes variably among juveniles). In contrast, in Psammodromus and examined members of Lacertinae , the interparietal scute is equal to or (more commonly) longer than the occipital scute. Timon usually has a much wider occipital scute, but its length is equal to that of the interparietal.

The supratemporal is wedge-shaped ( Fig. 5A, C ). Its dorsal edge is slender, narrowing anteriorly. In this view, the bone is slightly bent medially. In lateral view, the dorsal margin is arched. The nearly straight ventral edge is sharp, caused by the presence of facets on both sides.

The jugal consists of three processes: the suborbital, postorbital, and posterovental process. The posteroventral process is small, even in the large specimen ( Fig. 6H, I ). In medial view, the medial ridge is anteriorly located on the postorbital process and ventrally located on the suborbital process.

Comparison: The jugal also has a reduced posteroventral process in members of Gallotiinae , in contrast to the distinctive posteroventral process of Lacerta ( Arnold, 1989) , Dalmatolacerta , or Anatololacerta .

The postorbitofrontal comprises the fused postorbital and postfrontal, as seen in the smaller SMNS 96579 ( Fig. 6A, B ). The element is anteroposteriorly elongate, subrectangular in outline, tapering slightly posteriorly. In cross section, its ventral surface is slightly concave. Anteriorly, the postorbitofrontal is forked, thus embracing the frontoparietal suture as well as the anterodorsal margin of the ascending process of the jugal. The external surface bears a groove that separated the labial and parietal scutes.

Comparison: The postfrontal and postorbital are separate in the majority of Lacerta spp. , but fused at hatching in some members of Gallotia , in Psammodromus , and in some members of Lacertini ( Zootoca vivipara and Lacerta schreiberi ; see Arnold, 1973).

The squamosal is slender and hockey stick-shaped ( Fig. 5A ).

The pterygoid has a long quadrate process, ending bluntly ( Fig. 5Q ). Only the base of the transverse process is preserved. The palatine process bears teeth, which are pointed and of varying size.

Comparison: Teeth on the pterygoid are often found in species of Lacerta , Timon , Anatololacerta , Gallotia , and Psammodromus algirus ( Arnold, 1973; Barahona & Barbadillo, 1998).

The ectopterygoid is a short, robust, boomerangshaped bone. The lateral process is flatter, whereas the pterygoid process is taller and bifurcated ( Fig. 6G ).

Braincase: The unpaired basioccipital and paired otooccipitals (the units formed by co-ossification of the opisthotics and exoccipitals) are well preserved ( Fig. 6K, L ). The parocciptal processes are robust. The basioccipital is broad and rhomboidal in outline, forming the central region of the occipital condyle; it is dorsally slightly concave. The condyle is crescent-shaped in posterior view. In the larger specimen, the supraoccipital is badly preserved, and its identity is questionable. The element in question is subrectangular in shape.

The quadrate is convex anteriorly and expanded laterally into a sharp ridge: the tympanic crest ( Fig. 6E, F ). This crest is continuous from the cephalic to the mandibular condyle. The dorsal surface of the cephalic condyle protrudes slightly posteriorly. The mandibular condyle is saddle-shaped. The medial surface bears a medial crest.

The dentary is a robust, ventrally slightly arched element ( Fig. 7 ). In transverse section, it is C-shaped. The alveolar crest bears around 17 tooth positions. In medial view, Meckel’s groove is fully open, narrowing anteriorly. There is a slightly concave subdental shelf, which narrows posteriorly, because a facet for the splenial reaches anteriorly as far as the level of the sixth tooth from the back. On the dorsomedial side of the subdental shelf, a sulcus dentalis is present. The coronoid process of the dentary is long, with its posterodorsal limit being higher than the apices of the teeth. The angular process is short. The smooth external surface is pierced by seven mental foramina, located approximately at mid-height. Dorsolaterally at its posterior end, a wedge-shaped facet for the coronoid reaches approximately the level of the penultimate tooth.

Comparison: In Gallotia , the angular process of the dentary is reduced, its length being equal to or less than that of the coronoid process ( Fig. 8D ). With respect to the apex of the coronoid bone, the angular process does not usually reach so far posteriorly (this can be slightly variable, especially in non-adults). Among other lacertids, this character is otherwise observed only in Acathodactylus. In Psammodromus (sister group of Gallotia ), as well as in Lacerta , Dalmatolacerta , Anatololacerta , Timon , Podarcis , and Zootoca , the angular process is distictly longer than the coronoid process; with respect to the coronoid apex, the angular process extends as far as or surpasses it ( Fig. 8E ).

The coronoid process is of normal size in Gallotiinae , whereas it is more or less reduced in Lacertinae .

The low dentary tooth count and robust teeth of Janosikia ulmensis comb. nov. are similarities shared with members of Gallotiinae , especially Gallotia ( Fig. 8A, B ). Although the tooth number increases with the size of the individual ( Barahona et al., 2000), G. galloti has 17–20 robust teeth, G. atlantica has 18 robust teeth, G. caesaris has 17 robust teeth, and Psammodromus algirus has 21 robust teeth. Most members of Lacertinae have a higher number of more slender teeth, usually 20 or more: Lacerta agilis has 20, Lacerta trilineata Bedriaga, 1886 has 23–28, Podarcis sicula has 23, Takydromus sexlineatus has 30, Timon pater has 29, Zootoca vivipara has 22, and Acanthodactylus boskianus has 25 ( Kosma, 2004). In none of these species do the teeth increase markedly in robustness posteriorly.

The length of dentary equals that of the rest of the jaw in adults of Gallotia ( Fig. 8D ) and Psammodromus , whereas the dentary is slightly longer than the rest of the lower jaw in the members of Lacertinae examined ( Fig. 8E ).

Extant members of Gallotiinae are similar to Janosikia ulmensis comb. nov. in that the dentary is not strongly curved, the anterior region is not so elevated dorsally, and the symphyseal region is only slightly higher than the mid-portion of the subdental shelf ( Fig. 8A, B ). In Lacerta , Timon , Zootoca , Podarcis , and Acanthodactylus , in contrast, the anterior region is strongly curved and dorsally elevated ( Fig. 8C ).

The coronoid is triangular in shape ( Figs 3A , 4 and 7A, B ). It possesses an anterior and a posterior process, the angle between them being around 80°. The posterior region of the coronoid houses a fossa or depression. The anterior margin of this fossa is bordered by a distinctive ridge. Anteriorly, the coronoid has a dorsoventrally tall anteromedial process, which is almost twice as long as the posteromedial one. On the ventromedial side, it bears a facet for a dentary. The dorsal side of this region is thicker. A strong ridge forms the anterior margin of the bone.

Comparison: A broad angle between the anteromedial and posteromedial processes is also found in Gallotiinae ( Fig. 8A, B ), Dalmatolacerta , Anatololacerta , Zootoca , and Podarcis , whereas in Lacerta , Timon , and Acanthodactlyus the angle is more acute ( Fig. 8C ).

The angular is anteroposteriorly elongate ( Fig. 7A, B ). In lateral view, its ventral mid-region shows a constriction. More posteriorly, the bone grows taller, with a ventrally convex margin.

The surangular gradually narrows posteriorly ( Fig. 7A, B ). At its posterior end the bone is slightly elevated dorsally and forms the anterior border of the articular surface.

The articular is preserved only in the smaller specimen, forming the posterior and posteroventral margins of the mandible ( Fig. 4A ). It is a short element with an articular fossa for the quadrate on its posterodorsal side. The retroarticular process is short and has a fossa on its dorsal side.

The dentition is pleurodont. Premaxillary teeth are small. The anterior teeth of the cheek series are more acute and slender, whereas the posterior teeth are amblyodont, forming blunt cylinders. The crowns of the latter bear faint mesiodistal cutting edges, together with vertical striations ( Fig. 7C ). The teeth are closely spaced. The tooth bases are slightly swollen lingually. The fourth tooth from the posterior of the dentary is usually the largest. Although amblyodont dentition is present in the juvenile specimen, vestiges of mesial cusps are present on some anterior maxillary teeth.

Comparison: In extant lacertids, an ontogenetic change in the tooth morphology is sometimes seen, as in Gallotia stehlini , where the juvenile tricuspid teeth are replaced by multicuspid teeth in the adult ( Barahona et al., 2000). In fact, only in a few species do the blunt molariform teeth occur in juveniles (e.g., Dracaena guianensis and some species of the genus Tiliqua ; Estes & Williams, 1984).

The supraocular osteoderms have straight lateral margins, whereas the medial margins are rounded. They are apically flat and ornamented like the dermal roofing bones ( Fig. 5A ).

Postcranial bones

The interclavicle is cruciform. Its posterior process is thin and long. The lateral processes are directed laterally ( Fig. 5O ).

Comparison: The interclavicle is identical to that in Gallotiinae , where the lateral processes are directed laterally or (in Gallotia galloti ) very slightly posterolaterally, rather than anterolaterally, as in Acanthodactylus , Meroles , and Lacerta , and in the outgroup ( Klemmer, 1957; Arnold, 1989). Additionally, in Acanthodactylus and Meroles the posterior process is short.

The scapula is paddle-shaped ( Fig. 6J ). It gradually widens anterodorsally and has a rounded terminus. The narrow posteroventral surface contributes to the glenoid fossa.

Vertebrae: The preserved cervical vertebra is anteroposteriorly short with a high neural spine ( Fig. 5P ). The preserved caudal vertebra has an elongated centrum with long transverse processes ( Fig. 5R ).

The humerus is a large and robust bone ( Fig. 5O ). The proximal extremity is broad and elliptically rounded. The shaft is constricted. The distal extremity bears a well-developed, elliptical radial condyle with a larger ulnar condyle on its ventral aspect. The entepicondyle is robust and broad. The supinator process is distinctly smaller.

The zeugopodial bones are most likely the radius and ulna ( Fig. 3A ). The former is long and more robust than the latter, and its proximal end is slightly more expanded than the distal end. Close to the epiphyseal line of both bones, rugosities are present.

Figures

Figure 1. A, Ulm-Westtangente location. B, type material described by Gerhard (1903) as Ophisaurus ulmensis.

Figure 3. Janosikia ulmensis comb. nov., SMNS 96582. A, main prepared block of sediment, containing most cranial elements. B, reconstruction of the skull in dorsal view. C, life reconstruction of J. ulmensis comb. nov. from the early Miocene of Germany.

Figure 4. Janosikia ulmensis comb. nov., SMNS 96579, smaller partial skeleton. A, prepared block of sediment containing most of lower jaw together with postorbitofrontal. B, prepared block of sediment containing much of cranial skeleton.

Figure 5. Janosikia ulmensis comb. nov. SMNS 96582, detail of bones plus anatomical features as revealed by CT. Parietal in ventral view plus supratemporal, squamosal, supraocular osteoderms and?supraoccipital (A). Parietal in dorsal view (B). Supratemporal in posterodorsal view (C). and Frontal in dorsal (D) and right ventrolateral (E) views. Prefrontal in lateral (F) and medial (G) views. Nasal in ventral (H) and dorsal (I) views. Palpebral in lateral (J) and medial (K) views. Maxilla and premaxilla in external view (L). Maxilla of SMNS 95457 for comparison in lateral (M) and medial (N) views. Humerus, interclavicle and? scapula (O). Presacral vertebra in anterior view (P). Pterygoid (Q) and caudal vertebra (R).

Figure 6. Janosikia ulmensis comb. nov., SMNS 96579. A, B, postorbitofrontal in ventral (A) and dorsal (B) views. C, D, premaxilla in anterior (C) and posterior (D) views. E, F, quadrate in posterolateral (E) and medial (F) views. G, ectopterygoid. H, I, jugal in lateral (H) and medial (I) views. J, scapula. K, L, braincase in ventral (K) and posterior (L) views.

Figure 7. Janosikia ulmensis comb. nov. A, B, mandible of SMNS 96575 in lateral (A) and medial (B) views. C, dentary of SMNS 95455 in medial view and detail of tooth crowns. D, dentary of specimen SMNS 96581 in lateral view.

Figure 8. Comparison of dentary morphology of Gallotiinae and Lacertinae members in medial (A, B, C) and lateral (D, E) aspects: A, Gallotia galloti; B, D, Gallotia stehlini; C, E, Lacerta viridis.