Anomalepididae Taylor, 1939, 1996

Szyndlar, Zbigniew & Georgalis, Georgios L., 2023, An illustrated atlas of the vertebral morphology of extant non-caenophidian snakes, with special emphasis on the cloacal and caudal portions of the column, Vertebrate Zoology 73, pp. 717-886 : 717

Anomalepididae Taylor, 1939

General information.

Anomalepididae have been considered to represent the basalmost scolecophidians, mainly due to their peculiar cranial anatomy ( Rieppel et al. 2009; Scanlon and Lee 2011; Marra Santos and Reis 2019; Linares-Vargas et al. 2021). Nevertheless, recent molecular evidence suggests that Scolecophidia is a paraphyletic assemblage, with anomalepidids instead lying either as the sister group of Alethinophidia or either as more basal to leptotyphlopids and typhlopoids ( Vidal et al. 2010; Pyron and Burbrink 2012; Pyron et al. 2013; Zheng and Wiens 2016; Mirrales et al. 2018; Burbrink et al. 2020; Zaher et al. 2023), with considerably robust evidence for the former topology (see Miralles et al. 2018). Anomalepidids represent a very old lineage, with divergence date estimates suggesting that they appeared already during the Early Cretaceous ( Miralles et al. 2018).

Previous figures of vertebrae of extant Anomalepididae have been so far presented only by List (1966), Palci et al. (2020), and Herrel et al. (2021). Among these, vertebrae from the cloacal and caudal series were presented by Palci et al. (2020). Besides these figures, important observations on the vertebral morphology of anomalepidids were made by Dunn (1941) and Dunn and Tihen (1944).

Material examined.

Anomalepis mexicana Jan , 1860 in Jan & Sordelli 1860-1866 (FMNH 22853 [Morphosource. org: Media 000383763, ark:/87602/m4/383763]; MCZ Herp R-29220 [Morphosource. org: Media 000415858, ark:/87602/m4/415858]); Helminthophis frontalis (Peters, 1860) (MCZ Herp R-55117 [Morphosource. org: Media 000415384, ark:/87602/m4/415384); Liotyphlops albirostris (Peters, 1857) (UF Herp 43324 [Morphosource. org: Media 000493244, ark:/87602/m4/493244]); Liotyphlops beui (Amaral, 1924) (SAMA R40142 ); Liotyphlops bondensis Griffin, 1916 (X-rays of CPZ-UV 7290; CPZ-UV 7291; CPZ-UV 7292); Typhlophis squamosus (Schlegel, 1839 in Schlegel 1837 -1844) (MNHN-RA-1999.8306; KUBI 69819 [Morphosource.org: Media 000075052, ark:/87602/m4/ M75052 ]) .

Description (Figs 15-18>).

Trunk vertebrae. The morphology of the trunk vertebrae is strikingly similar to other scolecophidians. See the respective part in Leptotyphlopidae above.

Trunk / caudal transition. The morphology of these vertebrae is very similar to other scolecophidians. See the respective part in Leptotyphlopidae above.

Number of vertebrae. Anomalepis mexicana (FMNH 22853): 180 (170+4+6 [posteriormost caudal vertebrae are fused]); Anomalepis mexicana (MCZ Herp R-29220): 175 (167+4+6 [posteriormost caudal vertebrae are fused]); Helminthophis frontalis (MCZ Herp R-55117): 311 (296+5+10, including a final fusion); Liotyphlops albirostris (UF Herp 43324): 239 (226+3+10, including a final fusion); Liotyphlops bondensis (CPZ-UV 7290): 201 trunk and cloacal vertebrae plus 15 caudal vertebrae (posteriomost caudal vertebrae are fused); Liotyphlops bondensis (CPZ-UV 7291): 203 trunk and cloacal vertebrae plus 13 caudal vertebrae (posteriomost caudal vertebrae are fused); Liotyphlops bondensis (CPZ-UV 7292): 228 trunk and cloacal vertebrae plus 15 caudal vertebrae (posteriomost caudal vertebrae are fused); Typhlophis squamosus (KUBI 69819): 210 (201+3+6, including a final fusion).

Data from literature: Anomalepis aspinosus Taylor, 1939: 170 trunk vertebrae plus 3 cloacal vertebrae plus 5 caudal vertebrae (but some could be missing, especially from the caudal series) ( Dunn 1941); Liotyphlops albirostris : 204-247 trunk vertebrae plus 3-5 cloacal vertebrae plus 8-16 caudal vertebrae (posteriormost 2-3 caudal vertebrae are fused) ( List 1966); Liotyphlops albirostris : 229-247 trunk vertebrae plus 5 cloacal vertebrae (i.e., bearing forked ribs) plus 8-10 caudal vertebrae ("without ribs") ( Dunn and Tihen 1944); Liotyphlops ternetzii (Boulenger, 1896): 242 trunk and cloacal vertebrae plus 11 caudal vertebrae ( Alexander and Gans 1966).

In general, it seems that the total vertebral counts of anomalepidids are considerably low (although the available data are limited and should therefore be handled with cautiousness), with the notable exception of Helminthophis Peters, 1860, where this number surpasses the 300. Number of trunk vertebrae ranges between 170 and 296. Interestingly, the very low number (around 10 or less) of caudal vertebrae approaches that observed in many typhlopids, compared to most leptotyphlopids, where this number is higher. Of note is that species of Anomalepis and Typhlophis Fitzinger, 1843, seem to possess much lower (5-6) number of caudal vertebrae compared to species of Liotyphlops (8-16) and Helminthophis (10).