Borophagus

Borophagus[1] Temporal range: Middle Miocene to Late Pliocene, 12–2 Ma PreЄ Є O S D C P T J K Pg N
Borophagus secundus skull
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	Canidae
Subfamily:	†Borophaginae
Genus:	†Borophagus Cope, 1892
Type species
†Borophagus diversidens
Species
†B. diversidens †B. dudleyi †B. hilli †B. littoralis †B. orc †B. parvus †B. pugnator †B. secundus
Synonyms
†Cynogulo Kretzoi, 1968 †Hyaenognathus Merriam, 1903 †Porthocyon Merriam, 1903 †Osteoborus

Borophagus ("gluttonous eater") is an extinct genus of the subfamily Borophaginae, a group of canids endemic to North America from the Middle Miocene epoch through the Late Pliocene epoch 12—2 Mya.^[1]

Evolution

Restoration of two Borophagus preying on a camel

Borophagus, like other borophagines, are loosely known as "bone-crushing" or "hyena-like" dogs. Though not the most massive borophagine by size or weight, it had a more highly evolved capacity to crunch bone than earlier, larger genera such as Epicyon, which seems to be an evolutionary trend of the group (Turner, 2004). During the Pliocene epoch, Borophagus began being displaced by Canis genera such as Canis edwardii and later by Canis dirus. Early species of Borophagus were placed in the genus Osteoborus until recently, but the genera are now considered synonyms.^[1]

Taxonomy

Typical features of this genus are a bulging forehead and powerful jaws; Borophagus has been considered to be probably a scavenger by paleontologists in the past.^[2] Its crushing premolar teeth and strong jaw muscles would have been used to crack open bone, much like the hyena of the Old World. However, Borophagus fossils are so abundant and geographically widespread that some paleontologists now argue that Borophagus must have been both the dominant carnivore of its time, and thus an active predator because carrion feeding alone could not have sustained such a large population.^[3] They note that not all carnivores with bone-cracking ability are scavengers, such as the modern spotted hyena; instead, they interpret the bone-cracking ability as an adaptation to social hunting where complete utilization of a carcass was favored.^[3]

The adult animal is estimated to have been about 80 cm in length, similar to a coyote, although it was much more powerfully built.^[4]

Species

Restoration by Charles R. Knight, 1902

• Borophagus diversidens existed for 2.5 million years (synonymous with Felis hillianus, Hyaenognathus matthewi, Hyaenognathus pachyodon, Hyaenognathus solus, Porthocyon dubius)
• Borophagus dudleyi existed for 2 million years
• Borophagus hilli existed for 0.5 million years (synonymous with Osteoborus crassapineatus, Osteoborus progressus)
• Borophagus littoralis existed for 3 million years (syn. Osteoborus diabloensis)
• Borophagus orc existed for 2 million years
• Borophagus parvus existed for 2 million years
• Borophagus pugnator existed for 4 million years (synonymous with Osteoborus galushai)
• Borophagus secundus existed for 4 million years (synonymous with Hyaenognathus cyonoides, Hyaenognathus direptor)

Existence based on Figure 141 of Wang et al. (1999).^[1]

References

• Alan Turner, "National Geographic: Prehistoric Mammals" (Washington, D.C.: Firecrest Books Ltd., 2004), pp. 112–114. ISBN 0-7922-7134-3
• Xiaoming Wang, "The Origin and Evolution of the Dog Family" Accessed 1/30/06.

Further reading

• Picture of an Osteoborus skull in a museum, from "World of the Wolf." (Accessed 6/19/06)
• Russell Hunt, "Ecological Polarities Of the North American Family Canidae: A New Approach to Understanding Forty Million Years of Canid Evolution" (Accessed 1/30/06).
• Wang et al., "Phylogenetic Systematics of the Borophaginae (Carnivora:Canidae)." Bulletin of the American Museum of Natural History, No. 243, Nov. 17 1999. (PDF) (Accessed 4/11/06)
• Xiaoming Wang, Richard H. Tedford, Mauricio Antón, Dogs: Their Fossil Relatives and Evolutionary History, New York : Columbia University Press, 2008; ISBN 978-0-231-13528-3