North Dakota Stratigraphy Palaeolagus ROCK ROCK UNIT COLUMN PERIOD EPOCH AGES MILLIONS OF YEARS AGO Common Name: Holocene Oahe .01 Ancient rabbit Coleharbor Pleistocene QUATERNARY Classification: 1.8 Pliocene Unnamed 5 Miocene Class: Mammalia 25 Arikaree Order: Lagomorpha Family: Leporidae Brule Oligocene 38 South Heart Chadron Chalky Buttes Skull of the rabbit, Palaeolagus. Oligocene Brule Formation. Camels Butte Eocene Golden Stark County. 30 mm long. North Dakota State Fossil Collection. 55 Valley Bear Den Sentinel Description: Butte TERTIARY Palaeologus is in the Order Lagomorpha which includes the pikas, rabbits, and hares. Because of their small size and continually growing, gnawing teeth, they were much like rodents Bullion except lagomorphs have two pairs of gnawing teeth (incisors), one Paleocene Creek immediately behind the other, in the upper jaws compared to a single pair in rodents. The chewing action is also different between Slope the two groups, in lagomorphs the jaws work sideways and in Cannonball rodents the jaws work backward and forward. Palaeolagus was Ludlow 65 similar in appearance to the modern rabbit except its hind legs Hell Creek were proportionally shorter which suggests that they were more adapted for scampering, similar to a ground squirrel, than hopping. Fox Hills Palaeolagus grew to lengths of about 10 inches. They were common vegetarian inhabitants of the North Dakota savanna 30 million years ago. ACEOUS Pierre CRET 84 Niobrara Carlile Carbonate Calcareous Shale Claystone/Shale Siltstone Sandstone Sand & Gravel Mudstone Lignite Glacial Drift Palaeolagus. Painting courtesy of Simon and Schuster Publishing Company. Locations where fossils have been found ND State Fossil Collection Prehistoric Life of ND Map North Dakota Geological Survey Home Page.