2026-04-14 イェール大学
Photographs and anatomical drawings of the skull of Eosphorosuchus lacrimosa, viewed from the right/bottom (a, c) and the top/left (b, d). Credit: Miranda Margulis-Ohnuma
＜関連情報＞
- https://news.yale.edu/2026/04/14/210-million-year-old-crocodile-cousin-was-built-biting
- https://royalsocietypublishing.org/rspb/article/293/2069/20260130/481353/A-short-snouted-sphenosuchian-with-unusual-feeding
吻が短く、摂食様式が特異な「スフェノスクス類」は、生態学的特殊化がワニ形類の進化の初期に起こったことを示している A short-snouted ‘sphenosuchian’ with unusual feeding anatomy demonstrates that ecological specialization occurred early in crocodylomorph evolution
Miranda Margulis-Ohnuma ;Alexander A. Ruebenstahl;Dalton L. Meyer;Bhart-Anjan S. Bhullar
Proceedings of the Royal Society B
DOI:https://doi.org/10.1098/rspb.2026.0130
Abstract
The early evolution and diversification of Crocodylomorpha is a key component of vertebrate evolution on land but is somewhat poorly understood as a result of limited data. We describe Eosphorosuchus lacrimosa gen. et sp. nov., an early crocodylomorph from the Late Triassic of Ghost Ranch, New Mexico, whose cranial anatomy is divergent from that of other early crocodylomorphs (including Hesperosuchus agilis, to which it had been tentatively assigned), featuring an unusually short and osteologically reinforced facial region. A robust upper temporal arch and prominent surangular ridge indicate the presence of well-developed superficial external adductor musculature, which is divergent relative to pseudosuchians generally. These autapomorphies suggest specialization for a powerful bite. Bayesian and maximum parsimony phylogenetic analyses find E. lacrimosa outside of an H. agilis clade, near the base of Crocodylomorpha. The specializations of E. lacrimosa therefore represent the beginnings of ecological diversification within Crocodylomorpha among animals of a similar size, predating the Late Triassic appearance of Crocodyliformes and the Jurassic radiation of mesoeucrocodylians. Coexistence in the same single-event death assemblage of E. lacrimosa and H. agilis—two small early crocodylomorphs with functionally significant anatomical differences—suggests partitioning of terrestrial carnivorous niches within the ‘sphenosuchian’ grade.
