|Reconstructed skeleton of a Lagosuchus talampayensis|
Dinosauromorpha is a clade of archosaurs that includes the clade Dinosauria (dinosaurs), and all animals more closely related to dinosaurs than to pterosaurs. Birds are the only surviving dinosauromorphs.
The name was coined by Michael J. Benton in 1984. The first clade definitions were by Paul Sereno in 1991 who defined the concept as a node clade: the last common ancestor of Lagerpeton chanarensis, Marasuchus lilloensis, Pseudolagosuchus major and the Dinosauria (including Aves) and all its descendants.
Dinosauromorphs appeared by the Anisian stage of the Middle Triassic around 242 to 244 million years ago, splitting from other ornithodires. Early Triassic footprints reported in October 2010 from the Świętokrzyskie (Holy Cross) Mountains of Poland may belong to a dinosauromorph. If so, the origin of dinosauromorphs would be pushed back into the Early Olenekian, around 249 Ma. The oldest Polish footprints are from a small quadrupedal animal named Prorotodactylus, but footprints belonging to the ichnogenus Sphingopus that have been found from Early Anisian strata show that moderately large bipedal dinosauromorphs had appeared by 246 Ma. The tracks show that the dinosaur lineage appeared soon after the Permian-Triassic extinction event. Their age suggests that the rise of dinosaurs was slow and drawn out across much of the Triassic.
Basal forms include Saltopus, Marasuchus, the perhaps identical Lagosuchus, the lagerpetid Lagerpeton from the Ladinian of Argentina and Dromomeron from the Norian of Arizona, New Mexico, and Texas (all in the United States), Ixalerpeton polesinensis and an unnamed form from the Carnian (Santa Maria Formation) of Brazil, and the silesaurids, which include Silesaurus from the Carnian of Poland, Eucoelophysis from the Carnian-Norian of New Mexico, Lewisuchus and the perhaps identical Pseudolagosuchus from the Ladinian of Argentina, Sacisaurus from the Norian of Brazil, Technosaurus from the Carnian of Texas, Asilisaurus from the Anisian of Tanzania, and Diodorus from the Carnian(?) to Norian of Morocco.
Cladogram simplified after Nesbitt (2011):
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