Kingdom Animalia Clade Dinosauria Suborder Theropoda Scientific name Averostra | Phylum Chordata Order Saurischia Clade Neotheropoda Higher classification Neotheropoda | |
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Lower classifications Coelurosauria, Bird, Ceratosauria, Allosaurus, Carnosauria | ||
Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.
DefinitionEdit
Averostra was named by Gregory S. Paul in 2002 as an apomorphy-based clade defined as the group including the Dromaeosauridae and Avepoda with (an ancestor with) a promaxillary fenestra. It was later re-defined by Martin Ezcurra and Gilles Cuny in 2007 as a node-based clade containing Ceratosaurus nasicornis, Allosaurus fragilis, their last common ancestor and all its descendants.