Mesonyx

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Mammalia
Subclassis: Theria
Infraclassis: Eutheria
Superordo: Laurasiatheria
Ordo: †Mesonychia
Familia: Mesonychidae
Genus: Mesonyx

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]

Species

* Genus Mesonyx
o Mesonyx obtusidens
o Mesonyx uintensis

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.