| iDinosauromorpha
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Lagerpeton |
Dinosauromorpha is the name of a clade of archosaurs that includes the direct sister groups of dinosaurs, and the order Dinosauria itself. Basal forms, from the Ladinian, are Marasuchus, the perhaps identical Lagosuchus, and Lagerpeton. Birds are the only surviving dinosauromorphs.
The name was coined by Benton in 1984. The first clade definitions were by Paul Sereno in 1991 who accidentally defined the concept as both a node clade: the last common ancestor of Lagerpeton chanarensis, Lagosuchus talampayensis, Pseudolagosuchus major and the Dinosauria (including Aves) and all its descendants, and a stem clade: those Ornithodira more closely related to Dinosauria than to Pterosauria. As a stem clade definition was more functional, considering that only few basal Dinosauromorpha are known, and the relationship with Pterosauria is growing ever more problematic, a more prudent and exact definition was given by Sereno in 2005: the group consisting of Passer domesticus (Linnaeus 1758) and all species closer to Passer than to Pterodactylus antiquus (Soemmerring 1812), Ornithosuchus woodwardi (Newton 1894) and Crocodylus niloticus (Laurenti 1768). Should the pterosaurs not be closely related to the dinosaurs, this new definition would still be relevant, defining also the relation to the Crurotarsi; in that case it would be an older synonym of Avemetatarsalia.