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1-2012

An Elusive Carnivore Skeleton Discovered at The Ashfall Beds

Rick E. Otto University of Nebraska - Lincoln, [email protected]

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This Article is brought to you for free and open access by the Museum, University of Nebraska State at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Programs Information: Nebraska State Museum by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. An Elusive Carnivore Skeleton Discovered

at The Ashfall Fossil Beds

One of the most exciting recent discoveries at the Ashfall site was a small “dog” skeleton during the summer of 2010. The find was realized when interns Bill Mausbach and Amanda Millhouse were in the process of revealing a large male rhino. While excavating a pedestal around the front legs of the rhino, Bill found a set of bones from a much smaller –hidden under the rhino’s leg. Weeks of painstaking pick and brushwork revealed that there was a small carnivore – of some kind - underneath the mature barrel-bodied rhino skeleton. Everyone knows that good things can take a long time, and patience and perseverance are necessary nutritious; rich in fat and a source of protein. in paleontology. It was not until the following An interesting thing about the little dog summer, 2011, that Bill, along with museum uncovered at Ashfall, is that it is too small to chief preparator Greg Brown, exposed the have been much of a bone-crusher. The modest-sized skeleton in more detail. The molar teeth are more blunt than the bigger teeth in the skull were brushed clean and it species of bone-crushing dogs, and, in many was indeed a dog. A “dog” in a broader ways resemble the cheek teeth of raccoons. taxonomic sense, because this fox-sized The shearing teeth are small as well. It is very species, (as well as the largest dog species likely “raccoon-dogs” as they are sometimes from 12 million years ago, ) all belong called, were omnivores like raccoons and to a sub-family of fossil dogs known as bone- probably lived in similar ways; stalking frogs crushers, or Borophaginae (boro-fa-jeen-ae) . and crayfish along stream banks, and around There were seven or eight species of waterholes; munching on insects, or feeding borophagines in North America at Ashfall on fruit and nuts. time, while only two or three species of Cynarctus (sine-ark-tuss) was first , the lineage that eventually evolved described from a lower jaw found in into and .. northeast Colorado around 1900. William Diller Matthew of the American Museum of Bone-crushers in general have broad molars with blunt cusps, an adaptation Natural History coined the term Cynarctus, similar to hyenas for cracking bone. Bone and noted the reduced size of the shearing itself is not very digestible, but the marrow tooth and broadened molars. In the 1930’s paleontologist Paul McGrew proposed that inside of leg bones and ribs is highly previously mentioned species, C. crucidens, or C. voorhiesi. This is not the first fossil of Cynarctus to have been recovered at the Ashfall site. Occasional “raccoon-dog” were found by Mike Voorhies and crew in 1978, and a single lower jaw in 1995. This is the first skeleton, and it is the only known skeleton of any species of Cynarctus from the fossil record. In 2008, when an excavation crew was clearing a path in the fossil bed for the foundation of the Hubbard Rhino Barn, several isolated legs, ribs, and lower jaws were found, including a complete skull. To Paleontologist Nick Famoso examines Cynarctus stress the rarity of well-preserved fossils skull and jaws recovered in 2008. from the taxa, this is the only complete skull that has ever been recovered.

References

Barbour, E.H. and H.J. Cook. 1914. Two new fossil dogs of the Cynarctus from Nebraska. Nebraska Geological Survey 4:225-227.

Matthew, W.D. 1902. New from the of Colorado. Bulletin of the American Museum of Natural History 16:281-290

McGrew, P.O. 1937. The genus Cynarctus. Journal of Paleontology 11:444-449.

Wang, X. and R.H. Tedford. 2008. Dogs: Their Fossil Relatives & Evolutionary History. New Bill Mausbach and Rick Otto discuss the York:Columbia University Press. freshly exposed Cynarctus skeleton. Wang, X. and R.H. Tedford, B.E. Taylor 1999. Phylogenetic Systematics of the Borophaginae (:Canidae) Bulletin of the American Cynarctus be included in the raccoon family Museum of Natural History 243:1-391. (Procyonidae). Some years later, Richard Tedford of the American Museum of Natural History placed Cynarctus in the Borophaginae. Credits Four species of Cynarctus are now recognized, Cynarctus illustration by Mark Marcuson and the genus is only known from North Photographs by Rick E. Otto America. Cynarctus crucidens was described by former UNSM director Erwin Barbour (and Harold Cook) in 1914. Cynarctus voorhiesi was named in honor of Ashfall paleontologist Mike Voorhies by Xiaoming Wang and Tedford in 1999. After detailed study, the Ashfall specimen could be one of the