Borophagus secundus

Borophagus secundus ("devouring glutton") is an extinct species of the genus Borophagus of the subfamily Borophaginae, a group of canids endemic to North America from the Early Miocene epoch (23.0 Mya) through the Late Miocene epoch (5.3 Mya). Borophagus secundus existed for approximately 17.7 million years.^[2]

Overview

Borophagus secundus, like other Borophaginae, 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] Borophagus diversidens possibly led a hyena-like lifestyle scavenging carcasses of recently dead animals.

Taxonomy

Typical features of this genus are a bulging forehead and powerful jaws; it was probably a scavenger.^[3] Its crushing premolar teeth and strong jaw muscles would have been used to crack open bone, much like the hyena of the Old World. 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]

Morphology

Two fossil specimens of Borophagus secundus were measured by Legendre and Roth in 1988. They estimated that specimen one weighed 41 kg (90.3 lbs) and the second weighed 36.1 kg (79.5 lbs).^[5]

Fossil distribution

Borophagus secundus fossil specimens are very widespread from Honduras and El Salvador to central Mexico, Oklahoma panhandle, central and southern California, Nebraska, Kansas, and northern New Mexico.

Species

• Borophagus diversidens existed for 3.1 million years (synonymous with Felis hillianus, Hyaenognathus matthewi, Hyaenognathus pachyodon, Hyaenognathus solus, Porthocyon dubius)
• Borophagus dudleyi existed for 19.7 million years
• Borophagus hilli existed for 19.7 million years (synonymous with Osteoborus crassapineatus, Osteoborus progressus)
• Borophagus littoralis existed for 13 million years (syn. Osteoborus diabloensis)
• Borophagus orc existed for 5.4 million years
• Borophagus parvus existed for 6.4 million years
• Borophagus pugnator existed for 18 million years (synonymous with Osteoborus galushai)

Existence based on age of fossil collections and recombination with other species.

Sister genera

Carpocyon, Epicyon, Paratomarctus, Protepicyon

See also

• Borophaginae

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)