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Temporal range: Late Jurassic
Jaw of Macelognathus vagans
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Family: Hallopodidae
Genus: Macelognathus
Marsh, 1884
Type species
M. vagans
Marsh, 1884

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

Skeletal restorations

The type species, Macelognathus vagans, was described by Othniel Charles Marsh in 1884 as a turtle based on a partial jaw from the Late Jurassic Morrison Formation at Como Bluff, Wyoming. After being referred to the Dinosauria by Moodie in 1906 it was later reclassified by Ostrom in 1971 as a crocodilian relative. Based on new material from the Morrison Formation at Fruita, Colorado, in 2005 Göhlich et al. identified it as a basal crocodylomorph ("sphenosuchian"). It is considered an example of convergent evolution, due to the similarities to caenagnathid dinosaurs, with which it was not closely related. It was 3.9-6.2 feet long.

It is possibly a junior synonym of Hallopus victor.


  • Göhlich, U., L.M. Chiappe, J.M. Clark, and H.-D. Sues (2005) The systematic position of the Late Jurassic alleged dinosaur Macelognathus (Crocodylomorpha: Sphenosuchia). Canadian Journal of Earth Sciences 42: 307–321.
  • Marsh, O.C. 1884. A new order of extinct Jurassic reptiles (Macelognatha). American Journal of Sciences 27(3): 341.
  • Moodie, R.L. 1908. The relationship of the turtles and plesiosaurs. Kansas University Scientific Bulletin, 4: 319–327.
  • Ostrom, J.H. (1971). "On the systematic position of Macelognathus vagans". Postilla 153:1-10.

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