Lacertidae indet., 2024
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publication ID |
https://dx.doi.org/10.3897/fr.27.e109123 |
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publication LSID |
lsid:zoobank.org:pub:66166492-B0A7-4887-B51A-42361B1C9FC2 |
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persistent identifier |
https://treatment.plazi.org/id/2BD4DEF1-7649-5DBA-91FC-93220A0CDBC9 |
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treatment provided by |
by Pensoft |
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scientific name |
Lacertidae indet. |
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Lacertidae indet. View in CoL View at ENA
Figs 5 View Figure 5 , 6 View Figure 6
Parasauromalus paleocenicus 1940a aff. Parasauromalus paleocenicus : Kuhn, p. 24, figs 4a, 5a nomen dubium.
Iguanosaurus paleocenicus 1944 aff. Iguanosaurus paleocenicus : Kuhn, tab. 20, fig. 7 nomen dubium.
Iguanosauriscus paleocenicus 1958 Iguanosauriscus paleocenicus : Kuhn, p. 382 nomen dubium.
Plesiolacerta paleocenica 1983 Plesiolacerta? paleocenica new comb.: Estes, p 104 nomen dubium.
Material.
One left dentary MLU.GeoS.4059; seven isolated dorsal vertebrae MLU.GeoS.4067, 4066, 4061-4064, 4068.
Description.
Dentary. The specimen MLU.GeoS.4059 represents a left dentary (Fig. 5 View Figure 5 ). It is in fair condition. Only the anterior region is missing. The smooth lateral surface of the bone is pierced by a line of labial foramina, four of which are preserved (Fig. 5A View Figure 5 ). In the anterior region, these foramina are located at mid-height on the dentary, but as the dentary deepens posteriorly, the last two foramina are located more-or-less in the dorsal one-third of the bone. The posteriormost foramen is located at the level of the eleventh tooth position (counted from posterior). The alveolar shelf supports 21 tooth positions. Seven complete teeth are still attached to the bone and eight teeth have partly preserved tooth bases. However, since its anterior region is missing, the total number of teeth is unknown, but it certainly would have been slightly higher. The Meckelian canal is fully open and exposed medially (Fig. 5B View Figure 5 ). It is narrow in the anterior region and widens slightly posteriorly. In the posterior region, it is only moderately broad. The alveolar canal (Fig. 5D View Figure 5 ) opens at the level of the seventh tooth position (counted from posterior). The intramandibular septum forms the ventromedial wall, separating this canal from the Meckelian canal. The ventral margin of the bone is nearly straight. Note, however, that its posterior portion is damaged. The subdental shelf roofs the Meckelian canal (sensu Rage and Augé 2010), which is only slightly concave in medial view - the shelf is more-or-less straight in the anterior section, whereas it rises slightly dorsally from the ninth tooth position (counted from posterior). It gradually becomes thinner posteriorly due to the presence of the facet for the splenial on its ventromedial surface. This facet is present on the ventral margin as well. Unfortunately, the posterior section of the shelf is damaged. The sulcus dentalis is developed, mainly in the anterior region of the dorsal surface of the shelf. Posterior to the tooth row, the bone tapers into the narrow and pointed coronoid process, which rises slightly dorsally. On the dorsolateral surface of the posterior end, the articulation for the coronoid is preserved, showing that the coronoid overlapped the dentary dorsally.
Dentition. The tooth implantation is pleurodont. The teeth are tall and heterodont, ranging from monocuspid in the anterior region of the dentary to bicuspid with a dominant, triangular (pointed) and slightly recurved main cusp and an additional smaller, well-separated mesial cusp (Fig. 5D-F View Figure 5 ). The bicuspidity starts around the 14th tooth position (counted from posterior). Note, however, that only one tooth (14th) is preserved in this region, possessing an incipient mesial cusp. The tooth crowns are lingually slightly concave. Weak, delicate radial striations (converge at the tip of the main cusp) are present on the lingual side of, at least, some of the tooth crowns (well seen especially in the teeth located in the mid-portion of the dentary; see Fig. 5F View Figure 5 ). In some cases, two dominant striae form a slightly developed lingual cusp. The tooth neck is slightly swollen lingually. Small circular resorption pits are present on the lingual aspects of tooth bases in some teeth. The narrow inter-dental gaps of the preserved teeth indicate that the teeth were closely spaced.
Remarks. The specimen MLU.GeoS.4059 is identical to the left dentary on which Kuhn (1940a: figs 4a, 5a) established the new species aff. Parasauromalus paleocenicus , although one anterior tooth subsequently broke off. The specimen is undoubtedly the same one described by Kuhn. It was also figured by Kuhn in 1944 (see Kuhn 1944: tab. 20, fig. 7).
The specimen MLU.GeoS.4059 represents a lacertid since it exhibits the synapomorphies of the family ( Estes et al. 1988; Gauthier et al. 2012), such as sulcus dentalis and lateral overlap of the posterodorsal margin of the dentary by the coronoid. The tooth morphology also indicates a lacertid rather than other groups: presence of bicuspid teeth, weak striations and sometimes a weakly-developed lingual cusp is common among members of Lacertidae , including Lacerta (see Kosma 2004; Čerňanský and Syromyatnikova 2019). Among scincoids, the lingual cusp is usually well separated. In scincids, the lingual cusp is usually framed by broadly mesially and distally running cristae lingualis anterior and posterior rather than more-or-less vertical striae dominans anterior and posterior (e.g., Caputo 2004; Kosma 2004; Čerňanský et al. 2020b; Čerňanský and Syromyatnikova 2021). Moreover, bicuspid teeth among scincoids are rare but present only in some cordyliformes (Estes, 1983) - bicuspid teeth are present in, e.g., Gerrhosaurus flavigularis and Zonosaurus quadrilineatus , tricuspid teeth with dominant central cusp are present in, e.g., Tracheloptychus , and even multicuspid teeth are present in a herbivorous gerrhosaurid - the posterior teeth of Gerrhosaurus (Angolosaurus) skoogi possess up to seven cusps Kosma 2004; Nance 2007). The presence of bicuspid and faintly tricuspid teeth is reported in a potential cordyliform Deccansaurus from the Deccan intertrappean strata (uppermost Cretaceous - lowermost Paleocene; Yadav et al. 2023). However, this taxon differs from the Walbeck lacertid by many aspects, e.g., the Meckelian canal is distinctly narrow (shallow) and exposed ventrally rather than medially, and a splenial is short. In teiids, the tricuspid teeth have extensive cementum depositions on tooth bases ( Estes 1983).
Vertebrae. Seven vertebrae are available in the material (three of them are figured, see Fig. 6 View Figure 6 ). The neural spine is moderately high (MLU.GeoS.4067; the short vertebrae with tall neural spines tend to be cervicals and thoracics) or rather low (MLU.GeoS.6066, 4061 and 4063) (Fig. 6 View Figure 6 ) and slightly inclined posteriorly. It originates on the anterior border of the neural arch, forming a median ridge here (prespinal lamina sensu Tschopp 2016). It rises progressively posteriorly, and its top is slightly rounded. This part is wider and drop-shaped in dorsal view. The neural canal is large and pentagonal in outline. The well-developed prezygapophyses are distinctly inclined dorsally, having well-defined, roughly elliptical articulation surfaces at the level of which the vertebra reaches its greater width. The postzygapophyses are oval in shape. Both pre- and postzygapophyses are slightly elongated and oriented obliquely but more anteroposteriorly than mediolaterally. The vertebrae are only slightly constricted between the pre- and postzygapophyses and consequently, they are relatively broad in dorsal view. In lateral view, the interzygapophyseal ridge (postzygoprezygapophyseal lamina sensu Tschopp 2016) is visible as a sharp ridge, connecting both pre-and postzygapophyses laterally. The synapophyses are well-developed, being located in the anterior region. The centrum gradually narrows posteriorly. In ventral view, it has a triangular shape. Its relative length varies among vertebrae, being short in MLU.GeoS.4067 and 4068, but rather long in MLU.GeoS.4066 and 4061. The ventral margin of the centrum is concave in lateral view. In ventral view, the centrum is pierced by two small foramina in its anterior third. The cotyle and condyle are mainly preserved in MLU.GeoS.4067 and 4066. They are moderately large, being rounded in MLU.GeoS.4067, but slightly depressed in 4066. The condyle is well demarcated from the centrum - the condyle (especially where the cartilage has been stripped from it) is narrower than the centrum. Note, however, that the true precondylar constriction seen in varanids (the width of the condyle is greater than the width of the centrum immediately anterior to it, e.g., Rieppel 1980; Estes 1983; Smith et al. 2008; Holmes et al. 2010; Čerňanský et al. 2022a) is absent in the herein described material.
Remarks.
Kuhn (1940a) originally described an isolated dorsal vertebra as Saniwa aff. ensidens , although stated that the specimen is by two-thirds smaller than a vertebra of this American varanoid. The vertebra described and figured by Kuhn (1940a: fig. 3) is identical to the material we describe here, although one cannot be sure if one of the vertebrae represents the same specimen Kuhn described. Thus, the oldest occurrence of Saniwa in Europe should be considered to be younger, namely from the earliest Eocene age locality Dormaal ( Augé et al. 2022). For the identification of the vertebrae described here, see Discussion.
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