In Elginerpeton pancheni, a prototetrapod from the late Frasnian, basic tetrapod characteristics in the lower jaw and the cranium are observed. The taxon is believed to fill the gap between elpistostegalid fishes and well-preserved Devonian tetrapods. The Elginerpeton is considered more derived than the elpistostegalid fishes due to presence of paired fangs on the parasymphysial toothplate, a slender shaped anterior coronoid, and in the loss of the intracranial joint and coronoid fossa.Ahlberg, P. E., & Clack, J. A. (1998). Lower jaws, lower tetrapods–a review based on the Devonian genus Acanthostega. Transactions of the Royal Society of Edinburgh: Earth Sciences, 89(01), 11-46. The loss of the intercranial joint was a direct functional necessity to strengthen the broad and long platybasic skull when the animal was out of the water. The tubular lower jaw of the Elginerpeton, compared to the flat-lamina jaw shape of fishes gave it superior cross-sectional force, required when not supported in an aquatic setting – allowing for opening of the mouth outside of water. The adaptation may also be interpreted as a specialization for buccopharyngeal breathing. It is speculated to be the first step towards aerial respiration in the transition from fish to tetrapod.
