“Half-claw”
Species: Mesonyx lanius, Mesonyx obtusidens
Time Period: Eocene (55-37 MYA)
Charles Knight's restoration of Mesonyx, public domain image from Early Image
The first know and the genera for which the Mesonychidae were named is Mesonxy, a wolf sized predator from Early Eocene, dentition similar to a dog but still somewhat broader, and were designed for both shearing meat and crushing bone. Unlike any predators alive today, Mesonxy had small hooves at the ends of its toes. As described in 1910 by paleontologist Henry Osborn, Mesonxy had a “…long low body, somewhat like a Tasmanian wolf, terminating in a powerful tail, short limbs, and flattened nails…” Osborn goes on to describe Mesonxy as a scavenger and omnivore, comparing its diet to that of a bear.
Despite the superficial similarities, Mesonychids are not related to bears or canids, but are more closely related to hoofed mammals like deer, and are believed by some paleontologists to be relatives of modern whales. Skull similarities indicate creatures like Mesonxy were distant ancestors of modern cetaceans (whales and dolphins).
Sources: "Vertebrate Paleontology,
Third Edition" Michael J. Benton. Blackwell Publishing, Malden MA. 2005
"Beasts of Eden" David Rains Wallace.
University of California Press, Los Angeles and Berkeley CA. 2004
"Horns, Tusks and Flippers: The Evolution of
Hoofed Mammals" Donald R. Prothero & Robert M Schoch. The John Hopkins
University Press, Baltimore MD. 2002