Skull of Grippia Longirostris: no contradiction with a diapsid affinity for the Ichthyopterygia

Abstract

The skull of Grippia longirostris, one of the basal ichthyopterygians, is redescribed, based on a newly prepared referred specimen and the examination of others. Grippia had been considered to be the most basal ichthyopterygian until recently, and it has been suggested that the quadratojugal enters the upper temporal fenestra in this species. This and other unique features, which were considered plesiomorphic for ichthyopterygians, obscured the relationship of the group to other amniotes. It is shown here that the quadratojugal is much smaller than previously described, and does not enter the upper temporal fenestra. The skull configuration of the species is very similar to the condition in the recently‐described skull of Utatsusaurus hataii, another ichthyopterygian belonging to the basal grade of the group. The close similarity between the two help clarify ichthyopterygian plesiomorphies. There is no feature in the skull of Grippia that particularly contradicts the emerging consensus that ichthyopterygians are diapsids.