Reappraisal of the Permian dissorophidFayella chickashaensis

Abstract

The Permian temnospondyl Fayella chickashaensis from Oklahoma, a purported member of the intriguing clade of terrestrially adapted dissorophids, has been difficult to contextualize within the clade because of uncertainties related to the holotype, an isolated and badly weathered neurocranium. However, postcranial material that has been attributed to this taxon is particularly important for furthering our broader understanding of the patterns of temnospondyl evolution as it relates to their terrestrial diversification at the same time as the diversification of amniotes. Here we present a reevaluation of all material assigned to Fayella. Our examination of the holotype indicates that it is not referable below Temnospondyli indet., and Fayella chickashaensis is hence designated as a nomen dubium. Significant postcranial and the partial cranial material from a different locality than the holotype was referred to the taxon and is sufficiently diagnostic to be associated with the olsoniforms, the clade of large-bodied terrestrial dissorophoids. The presence of osteoderms and the absence of a subdivided naris exclude trematopids. This specimen can be differentiated from other dissorophid taxa by the proportions of the limbs and the elongation of the intercentra and is herein designated as the holotype of Nooxobeia gracilis gen. et sp. nov. The gracile limb proportions of Nooxobeia are particularly exaggerated relative to other olsoniforms and indicate an unusually active, agile predator that is interpreted here as an advanced stage of terrestrial adaptation among dissorophid temnospondyls.