Pseudeumeces kyrillomethodicus, Georgalis & Čerňanský & Klembara, 2021

Georgalis, Georgios L., Čerňanský, Andrej & Klembara, Jozef, 2021, Osteological atlas of new lizards from the Phosphorites du Quercy (France), based on historical, forgotten, fossil material, Geodiversitas 43 (9), pp. 219-293 : 227-236

Pseudeumeces kyrillomethodicus n. sp.

( Figs 6-14 )

urn:lsid:zoobank.org:act:FE001956-70BD-4493-8FD4-2F15E9A4778D

HOLOTYPE. — A left dentary ( NHMW 2019 /0051/0001).

PARATYPE. — A right dentary ( NHMW 2019/0051/0002).

ETYMOLOGY. — The new species epithet “ kyrillomethodicus ” honours Kyrillos (or Cyril; Greek: Κύριλλος) and Methodios (or Methodius; Greek: Μεθόδιος), the two Byzantine brothers from Thessaloniki that were sent by the Byzantine Emperor to the area of Bratislava (city of Dovina [currently Devin]) in 863 AD, where they created the first scripture for the people of Great Moravia. The name alludes to the fact that one of us (GLG) came from Thessaloniki to Bratislava (during which project also this paper was written) and generally to our nice collaboration among the three of us, Greek and Slovak scientists. Gender is masculine.

TYPE LOCALITY. — Imprecisely known locality, Phosphorites du Quercy, Department of Lot orTarn-et-Garonne, Occitanie, southern France; probably Oligocene.

DIAGNOSIS. — A medium sized lacertid, morphologically similar to Pseudeumeces cadurcensis , but differing from it in the following combination of features: 1) the last posterior three or four dentary teeth are reduced (instead of only the last one or two posterior teeth being reduced); 2) the dentary is short and massive rather than anteroposteriorly long relative to its dorsoventral height (the overall morphology of dentary in Pseudeumeces cadurcensis has narrower appearance relative to that in Pseudeumeces kyrillomethodicus n. sp.); 3) the facet for the anterolateral process of the coronoid reaches around the level of the 4 th tooth position (counted from posterior) rather than reaching the level of the posteriormost tooth position (in some cases, the level between the last and penultimate tooth positions); 4) the facet for anteromedial process of the coronoid reaches the level of the 3rd tooth position (counted from posterior) rather than only the level of the posteriormost tooth position; and 5) the dorsal elevation of the posterior section of the dentary is more pronounced.

DISTRIBUTION. — Oligocene, Phosphorites du Quercy, southern France.

DESCRIPTION

Holotype NHMW 2019 /0051/0001 ( Figs 6-9 )

The holotype left dentary NHMW 2019/0051/0001 is the most complete specimen ( Figs 6-9 ). The specimen measures

a total length of 16 mm. It is short, massively built, and ventrally deep. In cross-section, the dentary is C-shaped. In medial aspect, the dentary has a dorsally concave appearance and it gradually widens posteriorly. The CT scan reveals that the holotype dentary bears 15 tooth positions (see Fig. 9 ). On the medial side, the deep Meckel’s groove is fully open and distinctly broad posteriorly. It gradually narrows anteriorly, but it is still relatively wide even in this region. It disappears posterior to the large symphyseal region. CT images show that it continues inside to the bone further anteriorly only as a small internal canal. The alveolar foramen is small, being located at the level between the 4 th and 5 th tooth positions (counting from the posterior tooth; in other words, at the level of 11 th and 12 th tooth position counted from anterior). Further anteriorly, the alveolar canal is separated from the Meckel’s groove by the intramandibular septum, which is completely fused to the bone. Meckel’s groove is roofed dorsally by the subdental shelf, which bears a facet for the splenial on its ventral side. This facet reaches the level of around the 5th tooth position (counted from anterior) and its anterior end is well stepped. Dorsally, the subdental shelf bears the sulcus dentalis. The whole shelf gradually narrows posteriorly in medial aspect. The posterodorsal portion of the dentary is inclined dorsally, being well elevated. This inclination starts at the level of the 4th tooth position (counted from posterior). Posterior to the tooth row, there is a long and robust coronoid process. It reaches highly above the level of the largest tooth crowns. On its dorsomedial side, it bears a facet for the anteromedial process of the coronoid. It reaches the level of the 3 rd tooth position (counted from posterior). The posteroventral portion of the dentary is preserved. This region is slightly curved medially, forming a short angular process. Nevertheless, this region is also slightly weathered in this specimen.

The otherwise smooth lateral surface of the dentary is pierced by five labial foramina ( Figs 6A ; 7A ). The posteriormost one is located at the level of around the 5th tooth position (counted from posterior). In the posterodorsal region of the dentary, the wedge shaped facet for the anterolateral process of coronoid is present, being, however, very shallow. It appears to reach the level of the 4 th tooth position (counted from posterior).

Paratype NHMW 2019/0051/0002 ( Figs 10-14 )

Besides the holotype described above, only a single other dentary, the paratype NHMW 2019/0051/0002, can be confidently referred to Pseudeumeces kyrillomethodicus n. sp. This is rather similar to the holotype. The paratype NHMW 2019/0051/0002 is larger and more robust than

the holotype NHMW 2019/0051/0001 ( Figs 10-14 ). The posteroventral portion of the dentary that is preserved in the holotype is not preserved here and only 12 tooth positions can be therefore observed in the paratype NHMW 2019/0051/0002 (see Fig. 14 ). The facet for coronoid on the lateral side is more developed in the paratype dentary if compared to the holotype. When the specimen NHMW 2019/0051/0002 was originally complete and in the case it possessed 15 tooth positions as the holotype, then the facet for the anterolateral process of the coronoid reached the level of the 5th tooth position (counted from posterior).

If the tooth count was only 14, the coronoid reached the level of the 4th tooth position, the condition being identical to the holotype. However, the difference between this

specimen and the holotype is the position of the alveolar foramen, being located at the level of the 9th tooth position here (counted from anterior).

Dentition

The dentition is pleurodont and strongly heterodont. The teeth are closely spaced. While the tooth size increases posteriorly (except for the last three or four teeth that are again small, reduced), the teeth in the anterior portion of the tooth row are small and slender. The teeth in the posterior region are robust, forming blunt cylinders ( Figs 8 ; 12 ; 13 ). The teeth (especially those in the posterior half of the tooth row) are anteroposteriorly compressed. The tooth crowns bear delicate striations.

REMARKS

Pseudeumeces cadurcensis was originally established by Filhol (1877a) as a scincid of the extant genus Plestiodon Duméril & Bibron, 1839 . This taxonomic opinion was subsequently followed by others (e.g., Nopcsa 1908; Kuhn 1939), although affinities with the glyptosaurine Placosaurus also appeared in the literature ( Lydekker 1888b; Leenhardt 1926). Hoffstetter (1944) was the first to realize its lacertid affinities and placed it into its own genus, Pseudeumeces . So far, Pseudeumeces cadurcensis represented the only currently recognized species of this genus, as other two species that have in the past been referred to Pseudeumeces are now known to pertain to other genera or represent indeterminate lizards (i.e., Glyptosaurus walbeckensis Kuhn, 1940 , which was recombined into Pseudeumeces by Estes [1983], and Pseudeumeces pouiti Augé, 1993 , which was subsequently recombined to its own genus Ligerosaurus Augé, Bailon & Malfay, 2003 , as Ligerosaurus pouiti by Augé et al. [2003]).

We consider that the dentition and overall morphology of our new species Pseudeumeces kyrillomethodicus n. sp. appears to bear a resemblance with Pseudeumeces cadurcensis . Similarly to the case of our new taxon, the type material of Pseudeumeces cadurcensis also originates from an imprecise locality within the Phosphorites du Quercy ( Filhol 1877a; for this taxon see also Augé 2005; Augé & Hervet 2009; Čerňanský & Augé 2012; Čerňanský et al. 2016a; Bolet et al. 2017). Nevertheless, the material described herein clearly exhibits several obvious differences relative to Pseudeumeces cadurcensis (see Diagnosis above). Besides the features stated in the diagnosis, there is one additional difference – the dentary tooth number in Pseudeumeces cadurcensis is usually 17 (note that the tooth number in that taxon can range from 15-17; the holotype of the species [the left dentary AMNH FARB 241A] is incomplete but the preserved portion bears seven teeth and at least five other empty tooth positions), whereas the dentary tooth number of Pseudeumeces kyrillomethodicus n. sp., based on material described here, is around 14-15. Although such small differences in tooth counts can be informative in some cases, it should be noted that the tooth number in lacertids (see e.g., Čerňanský & Syromyatnikova 2019), like virtually all lizards, should not be interpreted as absolute due to its variability. So, whether it seems that the tooth number of Pseudeumeces cadurcensis appears to be slightly higher than the new species, we cannot fully demonstrate it and we refrain from formally considering this feature as a diagnostic character.

Besides the resemblance with Pseudeumeces cadurcensis discussed above, it should be noted also that the dentaries of Pseudeumeces kyrillomethodicus n. sp. slightly resemble those of Dracaenosaurus Pomel, 1846 , in the following features (see Müller 2004; Augé 2005; Čerňanský et al. 2016 a, 2017): 1) dentary is a rather short, massive, and deep element; 2) the presence of a dorsally elevated posterior portion of the dentary; 3) the presence of the amblyodont dentition, where the posterior robust teeth are low and form blunt cylinders (this is more pronounced in Dracaenosaurus ); and 4) the presence of striations on the tooth crown (note that the last two features are not unique to these two forms).

However, there are some important differences between these two forms, where Pseudeumeces kyrillomethodicus n. sp. can be differentiated from Dracaenosaurus croizeti Gervais, 1848 -1852, by the following combination of features (for Dracaenosaurus , see Müller 2004; Augé 2005; Čerňanský et al. 2016 a, 2017): 1) the dentary tooth number is around 14-15 rather than seven or eight; 2) the tooth size increases posteriorly, however, the largest tooth is the 4th or 5th one (counted from posterior), whereas the further posterior teeth decrease in size (to the contrary, the largest tooth in D. croizeti is usually the posteriormost one or sometimes the penultimate one); 3) the alveolar foramen, although its position can vary, is located further anteriorly (at the level between the 4th and 5th tooth positions in the holotype; counted from posterior) rather than at the level of the posteriormost tooth (or between last and penultimate tooth positions); 4) the facet for the anterolateral process of coronoid reaches around the level of the 4 th tooth position (counted from posterior) rather than terminating posterior to the tooth row; and 5) teeth (especially those in the posterior half of the tooth row) are anteroposteriorly compressed rather than mediolateraly compressed.

Note that for Dracaenosaurus we follow recent workers and treat Dracaenosaurus sauvagei (Filhol, 1882) as a junior synonym of the type species Dracaenosaurus croizeti (see e.g., Augé 2005). In any case, the holotype dentary of D. sauvagei is different from that of Pseudeumeces kyrillomethodicus n. sp. and its tooth count is within the range of D. croizeti .

In regards to our material, the specimen MNHN.F.QU17169 (see Augé & Hervet 2009: fig. 1) deserves a comment. This specimen, which has been allocated to Pseudeumeces cadurcensis by Augé (2005) and Augé & Hervet (2009), has only 12 tooth positions instead of usual 16-17. Moreover, the dentary of this specimen appears to be robust rather than narrow. This would point to a huge level of variability. However, in MNHN.F.QU17169, only the last posterior tooth is reduced and the coronoid reaches the level of this last posterior tooth position on both sides as it is typical, indeed, for Pseudeumeces cadurcensis (in contrast to our material described herein).

In general, it can be expected stratigraphically that not identical but slightly similar forms of a lineage (the exact age of our material is unfortunately unknown, as is also that of the type material of Pseudeumeces cadurcensis ) would exhibit a higher degree of morphological disparity reflecting the evolution through time than specimens collected from a single stratigraphic level. In those cases, it is of course difficult to add an exact border between such forms to distinguish taxa as units for science. However, we are convinced that all the above mentioned differences allow to erect a new taxon based on our type material. Even in extant herpetofaunas, lacertids include several morphologically cryptic species for which determination based on morphology can be even more difficult than the situation discussed here. Therefore, we consider the obvious differences in our material relative to the previously described forms as sufficient. Due to a high level of similarities of the currently known limited material with Pseudeumeces cadurcensis , we decided to allocate this new taxon Pseudeumeces kyrillomethodicus n. sp. to the same genus instead of erecting a new one.

It should be further noted that the extinct genera Pseudeumeces , Dracaenosaurus , and Janosikia Čerňanský, Klembara, & Smith, 2016, have been recovered as sister taxa to the extant Gallotia Boulenger, 1916 , from the Canary Islands, and all these taxa together with Psammodromus Fitzinger, 1826 , form the clade Gallotiinae . This was firstly observed by Čerňanský et al. (2016b, 2017), who also applied this revelation on the principles of the island rules, and later supported by Garcia-Porta et al. (2019) by their analyses based on a supermatrix relying on novel phylogenomic datasets. Therefore, we allocate Pseudeumeces kyrillomethodicus n. sp., as a member of Pseudeumeces , to the Gallotiinae as well.

Recently described fossil material from the early Eocene (MP 8-9) French locality of Mutigny (Paris Basin) indicates that not only stem but also morphologically mod- ern-like (potentially crown or close to crown) lacertids were present on the European continent already in the early Eocene ( Čerňanský et al. 2020). And later, lacertids were a rather diverse group during the Paleogene. The new taxon described herein, Pseudeumeces kyrillomethodicus n. sp., fully supports this high diversity and abundance of European Paleogene lacertids.

Figures

FIG. 6. — Pseudeumeces kyrillomethodicus n. sp. Photographs of the holotype left dentary NHMW 2019/0051/0001 in lateral (A), posterior (B), medial (C), and dorsal (D) views. Scale bar: 2 mm.

FIG. 7. — Pseudeumeces kyrillomethodicus n. sp. Virtual 3D models of the holotype left dentary NHMW 2019/0051/0001 in lateral (A), medial (B), ventromedial (C), and dorsal (D) views. Scale bar: 2 mm.

FIG. 8. — Pseudeumeces kyrillomethodicus n. sp. Close up photographs of posterior teeth of the holotype left dentary NHMW 2019/0051/0001 in medial (A) and dorsal (B) views. Scale bar: 1 mm.

FIG. 9. — Pseudeumeces kyrillomethodicus n. sp. Virtual slices of the holotype left dentary NHMW 2019/0051/0001: horizontal, with a special emphasis on the anterior and mid-section of the tooth row (A), horizonal, upper-more section with a special emphasis on the mid- and posterior section of the tooth row (B), and sagittal (C). Note the preserved tooth position showing the tooth number of 15. Scale bars: 2 mm.

FIG. 10. — Pseudeumeces kyrillomethodicus n. sp. Photographs of the paratype right dentary NHMW 2019/0051/0002 in lateral (A), medial (B), ventromedial (C), and dorsal (D) views. Scale bar: 2 mm.

FIG. 11. — Pseudeumeces kyrillomethodicus n. sp. Virtual 3D models of the paratype right dentary NHMW 2019/0051/0002 in lateral (A), medial (B), ventromedial (C), and dorsal (D) views. Scale bar: 2 mm.

FIG. 12. — Pseudeumeces kyrillomethodicus n. sp. Close up photographs of posterior teeth of the paratype right dentary NHMW 2019/0051/0002 in medial (A) and dorsal (B) view. Scale bar: 1 mm.

FIG. 13. — Pseudeumeces kyrillomethodicus n. sp. Close up photograph of the most robust tooth of the paratype right dentary NHMW 2019/0051/0002 in medial view. Note the prominent striations. Scale bar: 1 mm.

FIG. 14. — Pseudeumeces kyrillomethodicus n. sp. Virtual slices of the paratype right dentary NHMW 2019/0051/0002: horizontal (A) and sagittal (B). Note that the posterior section of the tooth row is missing. Scale bars: 2 mm.