Lagosuchus

Lagosuchus is an extinct genus of avemetatarsalian archosaur from the Late Triassic of Argentina. The type species of Lagosuchus, Lagosuchus talampayensis, is based on a small partial skeleton recovered from the early Carnian-age Chañares Formation. The holotype skeleton of L. talampayensis is fairly fragmentary, but it does possess some traits suggesting that Lagosuchus was a probable dinosauriform, closely related to dinosaurs.

A second potential species of Lagosuchus, L. lilloensis, is based on an assortment of slightly larger and more well-preserved fossils. These larger specimens have been considered much more diagnostic and informative than the original small L. talampayensis skeleton. As a result, some paleontologists have placed the larger specimens into a new genus, Marasuchus. Marasuchus is generally considered one of the more complete early dinosauriforms, useful for estimating ancestral traits for the origin of dinosaurs. This would also render Lagosuchus a nomen dubium, simply a name referring to a fossil which is too fragmentary to have a formal genus. However, other paleontologists support the argument that Lagosuchus is a valid genus, and that Marasuchus is a junior synonym of it.