The skull of the gerrhonotine lizard Elgaria panamintina (Squamata: Anguidae)

Abstract

We provide the first description of the skull, osteoderms, and hyoid apparatus of the poorly known alligator lizard Elgaria panamintina, and compare the cranial osteology of that species to the widespread and well-studied taxon Elgaria multicarinata. Patterns of morphological variation resulting from ontogenetic transformations and pathology are discussed. We employed x-ray computed tomography (CT) scans to examine two adult specimens of Elgaria panamintina and two adult specimens of Elgaria multicarinata, in addition to examining multiple traditionally prepared skeletal specimens of the latter species. CT scans provide simultaneous study of both articulated and disarticulated elements, allowing us to describe and document the morphology of the skull with exceptional precision and detail. The description of the skull of Elgaria panamintina serves as a generalization for all Elgaria; here we provide the first complete description of the skull of this genus for future uses in morphological and phylogenetic studies of both extant species and fossils.

Variation in the skulls of Elgaria and Gerrhonotus (Anguidae, Gerrhonotinae) and implications for phylogenetics and fossil identification

“…The osteology of the group was previously studied by several researchers ( Cope, 1892 ; Tihen, 1949 ; McDowell & Bogert, 1954 ; Romer, 1956 ; Criley, 1968 ; Meszoely, 1970 ; Rieppel, 1980 ; Gauthier, 1982 ; Good, 1987 ; Good, 1988a ); however, only a few species from each group within Gerrhonotinae were sampled. Variation in gerrhonotine osteology was previously reported in studies of ontogenetic variation ( Good, 1995 ) and timing of fusion relative to sexual maturity ( Maisano, 2002 ) in Elgaria coerulea , and an osteological description of the skull of Elgaria panamintina ( Ledesma & Scarpetta, 2018 ). However, intra- and interspecific variation in other gerrhonotine species was not previously documented or was not described in detail.…”

“…3. Midline foramen on the anterior surface of the alveolar plate of the premaxilla (anterior premaxillary foramen of Ledesma & Scarpetta, 2018 ): 0=absent, Fig. 2A ; 1=present, Fig.…”

“…Juvenile specimens of E. multicarinata (TxVP M- 8982, TxVP M- 8578) possess a single row of pterygoid teeth, but a juvenile E. kingii (TxVP M- 8582) has a large patch of teeth. An unusual condition was observed in E. panamintina MVZ 75918, in which pterygoid teeth are absent, but a rugose texture and empty tooth sockets are present on the ventral surface of the palatal plate (see figure 10A of Ledesma & Scarpetta (2018) ). Gerrhonotus infernalis TxVP M- 13440 is the only specimen in which pterygoid teeth appear to be completely absent ( Fig.…”

“…Anatomical nomenclature follows Evans (2008) and Ledesma & Scarpetta (2018) unless otherwise noted. In several cases, multiple names of an anatomical feature are given in parentheses to facilitate interpretation.…”

Bipedalism in Mexican albian lizard (squamata) and the locomotion type in other cretaceous lizards

“…The work by Gans et al (2008) was used for identification of disarticulated lizard limb bones. Our current sample of organisms is not very extensive; however recent osteological studies with small sample sizes due to the availability of collection specimens have been known to yield good results with fewer than 30 specimens (Yildirim et al, 2017;Ledesma and Scarpetta, 2018;Paparella et al, 2020).…”