Marasuchus lilloensis (previously considered Lagosuchus talampayenisis, Romer 1971), Ladinian, Middle Triassic, ~230 mya, ~40cm was a small dinosauriform widely considered a sister taxon to Herrerasaurus outside the Dinosauria. Here Marasuchus nests within the Dinosauria. It was derived from a sister to Tawa and Segisaurus and phylogenetically preceded Procompsognathus.
Smaller and distinct from Tawa, the skull of Marasusuchus had a maxilla with a straight ventral rim and shorter teeth.
The cervicals rose in a stronger S-curve. Distinct from other theropods two sacrals were retained. The caudals stretched out to over three times their diameter as the tail became more gracile.
The scapulocoracoid was robust overall. The ilium anterior process was squared-off with a dorsally concave margin. Digits 1 was shorter than metatarsal 2. The foot was relatively longer and narrower with more asymmetrical digits.