A new species of the theropod dinosaurSyntarsusfrom the Early Jurassic Kayenta Formation of Arizona

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Abstract
Until now, Syntarsus was based on a single species, S. rhodesiensis, known only from southern Africa. The discovery of Syntarsus in North America adds significantly to the increasingly detailed resemblance of African and North American Early Jurassic terrestrial vertebrate faunas. The new species, Syntarsus kayentakatae, is based on a complete skull and partial skeleton, and more fragmentary remains of at least 16 additional individuals, all from a narrow stratigraphie interval in the Kayenta Formation. Syntarsus kayentakatae is diagnosed by parasagittal cranial crests and fusion of the fibula to the calcaneum in adults. Syntarsus is the most derived member of the newly diagnosed theropod taxon Ceratosauria, possessing 22 apomorphies that arose subsequent to the divergence of ceratosaurs from other theropods. Syntarsus shares 20 of these with Coelophysis bauri, one of the earliest well-known theropods. By their first appearance, probably late Carnian, ceratosaurs already possessed a history involving considerable morphological transformation. A number of these characters arose convergently much later in time in ornithurine birds.