Cephalic anatomy of the rare Indonesian snake Anomochilus weberi

Abstract

The head of Anomochilus weberi combines features seen in living uropeltines and scolecophidians, two clades of fossorial snakes that appear to have the most specialized and, at the same time, the most divergent modifications of the head. However, the weakly supported premaxilla of Anomochilus departs from both scolecophidian and uropeltine modes of reinforcing the anterior tip of the snout, suggesting that Anomochilus is a less specialized burrower. Its skull also has a number of features unusual among snakes, including a unique buttress on the anterior ends of the septomaxillae, an ectopterygoid reduced to a splint that touches neither maxilla nor pterygoid, a short maxillary tooth row oriented a t 45" to the long axis of the skull, and a braincase and snout complex that are uniformly wide. The features of the upper jaw are predicted to confer behavioural and mechanical attributes intermediate between those of typhlopid scolecophidians and uropeltines.

Morphology of the skull of the white‐nosed blindsnake, Liotyphlops albirostris (Scolecophidia: Anomalepididae)

“…The medial closure of the cupola is incomplete in L. albirostris ( Fig. 5C), as is also the case in all non-macrostomatan snakes and autarchoglossan lizards (Cundall and Rossman, 1993). In alethinophidian snakes, the vomer contributes to the posterior closure of the vomeronasal cupola.…”

“…It has a strongly convex outer surface, a relatively straight ventral margin, a dorsal apex that enters between the nasal and frontal, a tapering anterior end that defines the posterodorsal margin of the external naris alongside the nasal, and a tapering posterior end that defines the anterior margin of the orbit alongside the frontal. As such, the prefrontal is an integral component of the ''outer shell design'' of the typhlopid skull as described by Cundall and Rossman (1993). The leptotyphlopid prefrontal exhibits a different morphology (Fig.…”

“…The snout complex of the scolecophidian skull is expanded (''telescoped'' sensu Haas, 1930), corresponding to the ''outer shell design'' (Cundall and Rossman, 1993), in adaptation to burrowing. The ''outer shell'' of the snout complex comprises, in Leptotyphlopidae, the premaxilla, nasals (variably fused in leptotyphlopids), prefrontals, and the rigidly suspended maxillae (List, 1966) (Fig.…”

“…In their landmark paper on the head anatomy of the basal alethinophidian snake Anomochilus weberi, Cundall and Rossman (1993) recognized two fundamentally different designs of skull morphology in adaptation to burrowing, the ''outer shell design'' characteristic of scolecophidians and the ''central rod design'' characteristic of such burrowing alethinophidians as uropeltines. The scolecophidian skull is paradigmatic of the ''outer shell design'' (Cundall and Rossman, 1993), in which the principal load-bearing elements are the premaxillae, nasals, and prefrontals, the latter abutting the laterally descending frontal flanges.…”

“…The scolecophidian skull is paradigmatic of the ''outer shell design'' (Cundall and Rossman, 1993), in which the principal load-bearing elements are the premaxillae, nasals, and prefrontals, the latter abutting the laterally descending frontal flanges. In snake skulls that correspond to the ''central rod design'' the premaxilla and nasals are presumed to be the major load-bearing elements during burrowing, further transmitting that load to the frontals at the nasofrontal joint.…”