A new rhytidosteid (Amphibia, Labyrinthodontia) from the Early Triassic Arcadia Formation of Queensland, Australia, and the relationships of Triassic temnospondyls

Abstract

The Early Triassic Arcadia Formation of Queensland, Australia, has yielded a second rhytidosteid labyrinthodont, the description of which allows reevaluation of the Triassic temnospondyls, which are here divided into two groups, trematosaurians and capitosaurians. Characters used in this division are discussed, and an hypothesis of relationships among the families of Triassic temnospondyls is proposed. The superfamily Rhytidosteoidea is rejected. The superfamily Trematosauroidea is increased to two families, the Trematosauridae and the Rhytidosteidae, the members of the family Indobrachyopidae being included in the Rhytidosteidae. The superfamily Brachyopoidea is included as the sister group of the Trematosauroidea within the trematosaurian group. The family Lydekkerinidae shares some trematosaurian group characters but lacks others and thus has been placed with some hesitation in the trematosaurian group. Description of the anatomy of the new rhytidosteid has led to a reexamination of certain aspects of labyrinthodont anatomy, in particular the ascending process of the pterygoid, and the postcondylar area of the lower jaw.