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.