This is the "Fossil Friday" post #18. Expect this to be a somewhat regular feature of the website. We will post any fossil pictures you send in to esconi.info@gmail.com. Please include a short description or story. Check the #FossilFriday Twitter hash tag for contributions from around the world!
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These fossil pictures here were contributed by ESCONI Board Member Keith Robitschek. The fossils are of unidentified Oreodonts and Canids from the Oligocene epoch of what is now the White River Badlands of Wyoming. Keith found these this summer. What great finds! Congratulations, Keith!
Oreodonts are extinct mammals. Their name means "mountain teeth". They belong to the Artiodactylids (even-toed mammals) and are closely related to camels and pigs. They looked something like a cross between a donkey and a pig. You can read more about them here.
Oreodonts are extinct Artiodactylids (even-toed mammals) most closely related to camels and pigs, with no close relatives living today. All are herbivorous, browsing on a diet of leaves and young shoots. Although tempting to think of them as feeding on "grass", true grasses did not appear until the late Oligocene, evolving and expanding widely during the Miocene as savannahs appeared during the cooling and drying of the that epoch.
Oreodonts fed on different types of vegetation than many modern artiodactylids do and therefore occupied an ecologically different niche than many living ungulates. True grazers such as equids did not start to appear until the middle Miocene when grasses became the dominant type of low forage. Found only in North America, oreodonts would eventually rival the large and diverse extant populations of modern bovid artiodactylids in Africa (antelopes, wildebeest, and buffalo) or the equally diverse populations of deer and goats of Asia.
Oreodonts are separated into two Families; Agriochoeridae was the earlier of the two families and consisted of a morphologically homogeneous group recorded from the latest Bridgerian or early Uintan North American Land Mammal Ages (NALMA) of the Lower to Middle Eocene to early Arikareean NALMA of the late Oligocene.
Canids are related to modern day foxes, dogs, and wolves. A full skeleton resembles that of a dog. Read more about them here.
Canidae - Dog or fox-like mammals, canids are familiarly dog-like, with straight, level backs, long, slender legs, large ears and long muzzles. All are built to run but many also use stealth and pouncing to secure birds and small mammals. Essentially monogamous, canids are unique among carnivores in regurgitating meat to feed pups and other non-hunting family members.
Although taxonomically diverse today, the geographically and ecologically broad distribution of canids is a relatively recent phenomenon. Prior to the latest Miocene (Hemphillian), all canids were restricted to North America where their members were more diverse in size, and presumably habit, than they are today. Canids first appeared in late Middle Eocene and went through three major successive and partly overlapping radiations. In the White River Badlands, the primitive Hesperocyon is the earliest canid of the North America and survived through the late Arikareean. The size of a small fox, later representatives of three different lineages would be much larger, occupying both predatory and scavenging niches. Regardless, early canid evolution was shaped by the spread of savanna and grassland environments as more tropical environments with their forest and woodland habitats gave way to transitional grassland and then arid vegetative regimes. Most modern taxa of canids did not appear until the Pliocene.
Oreodont skull
Various Oreodont bones, legs (front and back), partial spinal column, and ribs
Canid lower jaw (mandible)
Additional Canid mandible.
Various Oreodont and Canid bones. The skull is also shown above.
