The osteology of the early-diverging dinosaur Daemonosaurus chauliodus (Archosauria: Dinosauria) from the Coelophysis Quarry (Triassic: Rhaetian) of New Mexico and its relationships to other early dinosaurs

Abstract

The early evolution of dinosaurs is documented by abundant postcranial material, but cranial material is much rarer and comparisons of cranial features among early dinosaurs are limited to only a few specimens. Here, we fully detail the osteology of the unusual early-diverging dinosaur Daemonosaurus chauliodus from the latest Triassic Coelophysis Quarry in northern New Mexico, USA. The taxon possesses a unique and curious suite of character states present in a variety of early dinosaurs, and the morphology of D. chauliodus appears to link the morphology of Herrerasaurus with that of later diverging eusaurichians. Our phylogenetic analyses places D. chauliodus at the base of dinosaurs and our interpretation of the unusual mix of character states of D. chauliodus does not lead to a firm conclusion about its nearest relationships or its implications for the evolution of character state transitions at the base of Dinosauria. The combination of character states of D. chauliodus should not be ignored in future considerations of character evolution in early dinosaurs. As one of the last members of the earliest radiation of saurischians in the Carnian-early Norian, D. chauliodus demonstrates that members of the original diversification of dinosaurs survived until nearly the end of the Triassic Period.