Phosphoriguana peritechne, Lemierre & Georgalis, 2025

Phosphoriguana peritechne gen. et sp. nov.

Figure 13 View Fig

ZooBank registration. urn:lsid:zoobank.org:act:8C92DEA5-EE9E-427F-9929-D21F88366D87 .

Etymology. Te species epithet originates from the Greek word “peritechne ” (“περίτεΧνη”), meaning “elaborate”, “crafted with beautiful art”, referring to the beautiful, elaborate shape of the teeth of the new taxon.

Holotype. One complete left dentary ( UM-BFI 3057 ).

Differential Diagnosis. Phosphoriguana peritechne gen. et sp. nov. differs from Cadurciguana in: (1) having an opened sulcus Meckeli (closed and fused in C. hoffstetteri ) (see Augé, 2005); (2) having more developed accessory cusps; and (3) having a more arched ventrally margin of the dentary. Phosphoriguana peritechne gen. et sp. nov.

differs from Geiseltaliellus in lacking the presence of an inframeckelian lip narrowing or closing the sulcus Meckeli (see Augé, 2005; Smith, 2009b). Phosphoriguana peritechne gen. et sp. nov. differs from Geiseltaliellus lamandini in having an arched ventral margin of the dentary (see Augé, 2005). Phosphoriguana peritechne gen. et sp. nov. differs from Bifurcodentodon Čerňanský et al., 2023b in lacking the dentition made of two main cuspids, with several accessory cusps (see Čerňanský et al., 2023b). Phosphoriguana peritechne gen. et sp. nov. differs from Pseudolacerta De Stefano, 1903 , in lacking the strongly heterodont dentition and lacking the enlarged anterior caniniform teeth present in the latter genus (see Augé, 2005).

Type locality and age. La Bouffie, fissure fill located in the village of Vaylats (Lot, SW France); late Eocene ( MP 17 A); the species is so far known exclusively from the type locality .

Description of the holotype. UM-BFI 3057 is a complete dentary missing only a few teeth ( Fig. 13 View Fig ). Te dentary is elongated anteroposteriorly and large ( Fig. 13a, b View Fig ). 15 teeth are preserved, and at least six additional tooth positions can be identified, but the presence of sediment obscures most of the region, preventing a definitive total count ( Fig. 13c View Fig ). A broken tooth shows the implantation to be pleurodont; the dentition is heterodont ( Fig. 13a, c View Fig ). Te first three anterior teeth are monocuspid, with a posteriorly oriented triangular apex ( Fig. 13a, b View Fig ). Posteriorly, the teeth become tricuspid, with a large central cusp and two smaller mesial and distal accessory cusps of equal size well separated from the central one ( Fig. 13d View Fig ). Te posterior teeth are also larger and longer than the anterior ones ( Fig. 13a View Fig ). No sulcus dentalis seems to be present ( Fig. 13c View Fig ). Te subdental shelf is concave ventrally and expands only slightly anteriorly

( Fig. 13b View Fig ). On the ventral surface of the subdental shelf, a well-developed facet for the splenial extends anteriorly up to the sixth tooth position (starting from the anteriormost; Fig. 13a View Fig ). Te ventral side of the sulcus Meckeli also bears a facet for the splenial, extending from the second posteriormost tooth up to the third tooth position anteriorly. Te sulcus Meckeli is widely opened ventrolingually posteriorly, and progressively narrows anteriorly ( Fig. 13a View Fig ). At the level of the anteriormost five teeth, the subdental shelf covers lingually the sulcus Meckeli up to the symphysis ( Fig. 13a View Fig ). On the labial surface, a row of eight labial foramina opens mid-length of the surface ( Fig. 13b View Fig ). Both angular and coronoid processes are symmetrically developed ( Fig. 13b View Fig ). Moreover, there is a distinct groove on the posterolabial surface of the dentary for an anterolateral process of the coronoid. Tis groove seems to be more complex than usual (for pleurodontan standards), with an anteroposterior ridge running from front to back. It does not broaden anteriorly but might be dorsoventrally short ( Fig. 13a View Fig ).

Attribution and remarks. Two synapomorphies have been proposed on the dentary for Pleurodonta ( Gauthier et al., 2012): (1) the restriction of the sulcus Meckeli; and (2) the anteromedial process of the coronoid wrapping under the level of the teeth row. UM-BFI 3057 only possesses the second character and thus is tentatively referred to Pleurodonta.

Among known European pleurodontans, Phosphoriguana gen. nov. can be differentiated from all known genera (see Differential Diagnosis above). Outside Europe, a large number of pleurodontans is known from the Eocene of North America, pertaining to a number of extinct genera (e.g., Estes, 1983; Gilmore, 1928; Scarpetta, 2020; Smith & Gauthier, 2013; Smith, 2006, 2009a, 2011a, 2011b). Te shape and dentition of the holotype dentary UM-BFI 3057 does not also match with the corresponding morphology of the North American taxa. Tus, we establish a new genus and species in order to accommodate the dentary UM-BFI 3057.

Even though its distinctive anatomical features, the new taxon Phosphoriguana peritechne gen. et sp. nov. cannot be confidently referred to Pleurodonta based solely on the above-described features. As a matter of fact, pleurodont tooth implantation, tricuspid dentition, and lack of a sulcus dentalis are indeed typical features of pleurodontans, however, these can be also observed also in some members of Teiidae (e.g., genus Kentropyx Spix, 1825 ) and Lacertidae (e.g., Arnold et al., 2007). Furthermore, our current knowledge about potential synapomorphies in the jaws of Pleurodonta is still limited, and as a matter of fact, only a few have now been pointed out. Two were proposed by Smith (2009b): (1) in the maxilla, a separate foramen for the subnarial artery on the premaxillary process; and possibly (2) in the dentary, a wrapping of the anteromedial process of the coronoid underneath the tooth row. (that latter was suggested by Smith, 2009b but was recovered as a synapomorphy by Gauthier et al., 2012) Additionally, Gauthier et al. (2012) identified a third synapomorphy: (3) a restriction (but not closure, much less fusion) of the Meckelian groove as a synapomorphy of Pleurodonta and part of its stem. For further discussion of these characters, see Smith (2020a, 2020b, 2020c) definitions of Pan-Iguania, Pan-Acrodonta and Pan-Iguanidae. Te holotype dentary (UM-BFI 3057) of Phosphoriguana peritechne gen. et sp. nov. from La Bouffie seems to possess character (2) but not (3), so the evidence for its taxonomic attribution to Pleurodonta is somehow ambiguous. To the contrary, character (3) in UM-BFI 3057 really deviates from the typical pleurodontan pattern: practically, pleurodontans - with the exception of Hoplocercidae - conform to character (3) and do not normally show such a widely open Meckelian groove, as observed in the new taxon from La Bouffie. Outside Pleurodonta, an alternative, potential taxonomic allocation of Phosphoriguana peritechne gen. et sp. would be that this holotype dentary (UM-BFI 3057) pertains to the same taxon as the frontal from La Bouffie that was originally described as a tupinambine teiid by Augé and Brizuela (2020: fig. 2; specimen MNHN.F.BFI1877). All these being said, Phosphoriguana peritechne gen. et sp. is only tentatively referred to Pleurodonta and we anticipate that future (ideally articulated) specimens may shed some more light on its precise taxonomic affinities within other lizards.