Mesonyx

Mesonyx Temporal range: Middle Eocene–Late Eocene PreЄ Є O S D C P T J K Pg N
Mesonyx by Charles R. Knight
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Mesonychia
Family:	Mesonychidae
Genus:	Mesonyx Cope, 1872
Species
Mesonyx obtusidens Mesonyx uintensis

Mesonyx ("middle claw") was a wolf-like mammal of the family Mesonychidae, the type family of the order Mesonychia (sometimes referred to by its older name, "Acreodi"), existing 51.8—51.7 Ma (AEO)^[1]. It may have been ancestral to cetaceans.

It was a fast predator from the Middle Eocene of Wyoming, and it probably hunted hoofed plant eaters, moving lightly on its toes. However, instead of claws, Mesonyx's toes ended in small hooves. Its long skull had a relatively large sagittal crest above the braincase to anchor large jaw muscles and give it a powerful bite.

The skull of Mesonyx (left), compared to other carnivore skulls

Mesonyx specimens have been unearthed in Colorado, Wyoming, and Utah. Mesonyx uintensis from the Upper Eocene of Wyoming is described as having a total cranium length of 429 mm. (17 inches) and a facial length of 206 mm (8 inches). Another specimen of Mesonyx uintensis is known from the Upper Eocene of northern Utah.^[2]

References

• Much of the introductory information in the first paragraph is from Dinosaur Encyclopedia

1. ^ Paleobiology Database, Mesonyx, collection #16240, Huerfano II site, Huerfano County, Colorado, authorized by John Alroy
2. ^ Osborn, Henry Fairfield (November 11, 1924). "Andrewsarchus, giant mesonychid of Mongolia". American Museum Novitates (The American Museum of Natural History) (146). http://digitallibrary.amnh.org/dspace/bitstream/2246/3226/1/N0146.pdf. Retrieved 2007-08-05.