A large brachyopoid from the Middle Triassic of northern Arizona and the diversity of brachyopoid temnospondyls from the Moenkopi Formation

Abstract

Brachyopoids represent a diverse and late surviving temnospondyl group, lasting until the Early Cretaceous. Here, we report on brachyopoid material previously assigned to Hadrokkosaurus bradyi that represents a distinct brachyopoid taxon, characterised by a smaller number of large, robust mandibular teeth, a feature rarely observed in other temnospondyls. We also revisit an angular previously referred to Hadrokkosaurus potentially belonging to other temnospondyl taxa present in the Middle Triassic of North America. In light of the abundance of material of possible taxa distinct from Hadrokkosaurus, we express the need to re-examine previously collected specimens as new information changes the landscape of palaeontology. Parsimony analyses using exclusively mandibular characters recover the new brachyopoid taxon from the locality in a polytomy with Hadrokkosaurus and Vanastega at the base of Brachyopoidea, adding to a diversity of mandibular morphology of temnospondyls in the Middle Triassic of North America.