Braincase of<i>Enaliornis</i>, an Early Cretaceous bird from England

Abstract

ABSTRACT The braincase of the Early Cretaceous bird Enaliornis is indicative of a primitive avian brain with a relatively large medulla oblongata, a small cerebellum, small cerebral hemispheres broadly separated from the labyrinth, and a strong basilordotic bend of the whole brain, the latter being characteristic of an airencephalic skull. The reduction of the dorsal pneumatic recess, the large size of the auricular fossa, and possibly the lack of interfoliar ridges on the roof of the cerebellar fossa suggest diving habits and thus support the association of the braincases with the type tarsometatarsus of Enaliornis. The braincase of Enaliornis is most similar to those of Hesperornis, Phaethon, Diomedeidae and Fregata. Most of the similarities to these taxa are primitive for birds.