Macelognathus

Macelognathus is an extinct genus of sphenosuchian crocodile from the Late Jurassic. Originally it was believed be a theropod dinosaur. It lived in what is now Wyoming, in North America.

The type species, Macelognathus vagans, was described by Marsh in the 1880s, and was later reclassified by Clark and Sues in 2002 when five new skeletons were discovered. It is considered an example of convergent evolution, due to the similarities to caenagnathids, with which it was not closely related.

It is possibly a junior synonym of Hallopus victor.