The skull of Sanajeh indicus, a Cretaceous snake with an upper temporal bar, and the origin of ophidian wide-gaped feeding

Author(s)

Zaher, Hussam ; Mohabey, Dhananjay M. ; Grazziotin, Felipe G. ; Wilson Mantilla, Jeffrey A.

• Document type: Journal article
• Source: ZOOLOGICAL JOURNAL OF THE LINNEAN SOCIETY; v. N/A, p. 42-pg., 2022-05-13.

Abstract

Recent phylogenetic analyses differ in their interpretations of the origin and interrelationships of snakes, resulting in polarized views of snake ecology, habit and acquisition of features associated with wide-gaped feeding (macrostomy). Here, we report a new specimen of the Late Cretaceous nest predator Sanajeh indicus that helps to resolve the origin of macrostomy. The new specimen preserves an ossified upper temporal bar and a posteriorly expanded otooccipital region that lacks a free-ending supratemporal bone and retains a lizard-like palatomaxillary arch that allows limited movements during swallowing. Phylogenetic analyses of a large-scale total evidence dataset resolve Sanajeh near the base of Pan-Serpentes, as the sister group of Najash, Dinilysia and crown-group Serpentes. The Cretaceous Tetrapodophis and Coniophis represent the earliest-diverging members of Pan-Serpentes. The Cretaceous hindlimbed pachyophiids and Cenozoic Australian 'madtsoiids' are inside crown Alethinophidia, whereas mosasaurs are recovered invariably within anguimorphs. Our results suggest that the wide-gape condition in mosasaurs and snakes might have evolved independently, as functionally distinct mechanisms of prey ingestion. The intermediate morphology preserved in Sanajeh indicates that ingestion of large prey items (macrophagy) preceded wide-gaped, unilateral feeding (macrostomy), which appeared 35 Myr later, in the common ancestor of pachyophiids, Cenozoic Australian 'madtsoiids' and alethinophidians. (AU)

• FAPESP's process: 18/11902-9 - Origin and higher-level diversification of snakes: basal key-taxa and the Colubroidean Cenozoic radiation (Squamata)
• Grantee: Hussam El Dine Zaher
• Support Opportunities: Scholarships abroad - Research
• FAPESP's process: 11/50206-9 - Origin and evolution of snakes and their diversification in the Neotropics: a multidisciplinary approach
• Grantee: Hussam El Dine Zaher
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants