Hyaenodon spp. 1870
In 1853 (shortly after the publication of "Ancient Fauna of Nebraska") Joseph Leidy reported on the fossil remains of two new mammal predators from the White River Badlands (2). He named them Hyaenodon cruciens and Hyaenodon horridus. They were similar to a mammal discovered in France, but the larger of the two, Hyaenodon horridus, was far more impressive than anything from Europe. In his 1869 monograph ("On the Extinct Mammalia of Dakota and Nebraska"), Leidy wrote:
"...probably the most sanguinary and dreaded enemy of it numerous ruminant associates, the oreodons, etc., greatly exceeded in size any of the dreaded European species, its skull fully equal that of the largest individual of the Black Bear, Ursus americanus."
Side views of the skulls of Hyaenodon crucians (left) and Hyaenodon horridus (right). These two fossils are shown to scale, with the Hyaenodon crucians fossil measuring 5 inches (13 cm) and that of Hyaenodon horridus measuring 11 inches (28 cm). These images were first published in On the Extinct Mammalian Fauna of Dakota and Nebraska (1869). Each image is a detail of a lithograph. Click on either image to view the full lithograph.
Hyaenodon belongs to an extinct group of mammals called creodonts. Creodonts were the predominant and most diverse group of mammalian predators during the Eocene and Oligocene. There are two families of creodonts. The oxyaenids were generally small-bodied forms with short limbs that became extinct at the end of the Eocene. The Hyaenodontidae (named by Leidy) had longer limbs. They were more diverse, longer-lived and more widely distributed. Hyaenodonts were greatly reduced in the late Oligocene, but one genus from Asia survived into the Pliocene.
Creodonts were more primitive than the true carnivores, (3) although their teeth were clearly adapted for eating meat, they were less specialized than those of the carnivores. Their limbs were also not as well adapted for running. Some paleontologist believe that they were unable to cope with the faster ungulates that appeared at the beginning of the Miocene.
Notes:
- Etymology:
Hyaenodon (high-EE-no-don) = hyaena tooth
horridus (HOR-rid-us) = horrible
crucians (CREW-see-ans) = torture, hard violence
[go back] - The
first specimens of Hyaenodon were sent to Leidy by Dr. John Evans, who
conducted a geological survey of the White River Badlands for David Dale Owen.
Additional specimens were provided by Benjamin Shumard, Ferdinand V. Hayden and
Mr. Meek.
[go back] - Carnivores
are the dominant mammalian predators today. They include bears, cats, dogs, ferrets,
otters, pandas, seals and raccoons.
[go back]