A new amphibamiform from the Early Permian of Texas elucidates patterns of cranial diversity among terrestrial amphibamiforms

Abstract

Amphibamiform temnospondyls are at the forefront of discourse surrounding modern amphibian evolutionary origins. Here we present a new amphibamiform, Kermitops gratus gen. et sp. nov., from the Lower Clear Fork Formation of the Early Permian of Texas. Kermitops reveals a mosaic of features shared with other amphibamiforms and possesses unique characteristics, including an internarial fontanelle formed by the premaxillae without contribution of the nasals. It possibly possesses a basioccipital that contributes to the occipital condyle, which has significant implications for recent hypotheses of the evolution of the modern amphibian neurocranium. Parsimony analyses recover non-traditional amphibamiform relationships but place Kermitops within Amphibamiformes. Bayesian inference analysis captures a more traditional hypothesis of amphibamiform relationships; however, the time-calibrated analysis under the fossilized birth–death model recovers a topology that mirrors the parsimony topologies. The low robusticity of topologies across different permutations employing traditional and modern methods suggest a need for improvement of current morphological datasets of lissamphibian origins. A morphometric analysis of the crania of terrestrial amphibamiforms reveals the evolution of disparate cranial morphologies among coeval taxa from the Early Permian of Texas.