Convergent evolution of jaw-opening muscles in lepidosirenid lungfishes and tetrapods

Abstract

Lepidosiren and Protopterus have a jaw-opening muscle which is topographically and functionally similar to the depressor mandibulae of salamanders. The similarity is so close that it poses the question whether the lepidosirenid jaw-opening system is homologous to that of tetrapods. New information presented here confirms that the muscle is absent in Neoceratodus forsteri, the living sister species of Lepidosiren and Protopterus, and paleontological evidence shows that the muscle was absent in phylogenetically primitive lungfishes. There are also developmental differences between the mandibular depressor of lepidosirenids and the depressor mandibulae of tetrapods. Based on this, I conclude that the mandibular depressor of lepidosirenids has evolved independently from the functionally equivalent muscle of amphibians.