Aristosuchus

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Compsognathidae (?)

Overview: Despite what the name “noble crocodile” would imply, Aristosuchus wasn’t a crocodilian or even especially closely related to them. It was a solid member of the Dinosauria. The name was chosen by the British paleontologist Harry G. Seeley, who established Aristosuchus as its own genus in 1887. Seeley interpreted the animal as representing a kind of transitional stage among members of the clade now known as the Archosauria, between crocodile-like animals and true dinosaurs – an idea for which he named it. Prior to then, the creature’s fossils were thought to represent a species of theropod in the genus Poekilopleuron. It was described as such in the 1870’s by England’s famed naturalist Sir Richard Owen. Seeley was correct in classifying it as a separate genus, but Owen was accurate in his interpretation of it as a member of the Theropoda. There is, however, debate over how it should be classified among other specific lineages within this larger grouping.

Phylogenetic research has often placed Aristosuchus within the Coelurosauria, specifically close to the famous Compsognathus, in the family Compsognathidae. With a length of about two meters, it would’ve been one of the larger members of this group. In recent years, however, paleontologists have begun to doubt the validity of the Compsognathidae. Some suspect many members are likely based on juveniles from lineages of larger theropods like the megalosaurids or allosauroids. As for Aristosuchus, most studies still classify it as a coelurosaur. The holotype fossils of Aristosuchus are known from the Wessex Formation on the Isle of Wight, off the southern coast of England. Studies find said specimen, consisting of only partial remains, was not itself fully grown, so its full adult size may be hard to determine until more fossils are found, or if it was the juvenile of another genus. It’s believed to have coexisted with genera like Eotyrannus, Neovenator, Iguanodon, and Polacanthus.