Hesperocyon is an extinct genus of canids (subfamily Hesperocyoninae, family Canidae) that was endemic to North America, ranging from southern Canada to Colorado. It appeared during the Uintan age, –Bridgerian age (NALMA) of the Mid-Eocene– 42.5 Ma to 31.0 Ma. (AEO).[1] Hesperocyon existed for approximately 11.5 million years.
| Hesperocyon Temporal range:
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|---|---|
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| Skeleton of H. gregarius at the Smithsonian National Museum of Natural History | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Family: | Canidae |
| Subfamily: | †Hesperocyoninae |
| Genus: | †Hesperocyon Scott, 1890 |
| Type species | |
| †Hesprocyon gregarius | |
| Species | |
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Taxonomy
Hesperocyon was assigned to Borophagini by Wang et al. in 1999[2] and was the earliest of the canids to evolve after the Caniformia-Feliformia split some 42 million years ago. Fossil evidence dates Hesperocyon gregarius to at least 37 mya, but the oldest Hesperocyon has been dated at 39.74 mya from the Duchesnean North American land mammal age.[3]
The Canidae subfamily Hesperocyoninae probably arose out of Hesperocyon to become the first of the three great dogs groups: Hesperocyoninae (~40–30 Ma), Borophaginae (~36–2 Ma), and the Caninae lineage that led to the present-day canids (including grey wolves, foxes, coyotes, jackals and dogs). At least 28 known species of Hesperocyoninae evolved out of Hesperocyon, including those in the following five genera: Ectopocynus (32–19 mya), Osbornodon (32–18 mya), Paraenhydrocyon (20–25 mya), Mesocyon (31–15 mya) and Enhydrocyon (31–15 mya).[2][4]
Evolution
It is believed that Hesperocyon evolved through from Miacis. In addition to being the oldest subfamily of canids, it was the first subfamily to become extinct.[5]
Morphology
This early, 80-centimeter-long (2 ft 7 in) canine looked more like a civet or a small raccoon. Its body and tail were long and flexible, while its limbs were weak and short. Still, the build of its ossicles and distribution of its teeth showed it was a canid. It may have been an omnivore—unlike the hypercarnivorous Borophaginae that later split from this canid lineage.
Fossil record
The oldest fossil evidence was recovered from Saskatchewan dating from 42.5 mya to 31.0 Ma. The youngest fossil was recovered from the Dog Jaw Butte site, Goshen County, Wyoming dating to the Arikareean age (NALMA) of the Oligocene and Miocene 42.5 mya—31.0 Ma. (AEO).[6][failed verification – see discussion]
References
- ^ Paleobiology Database Collection 16626, Swift Current Creek, Saskatchewan, Canada. Authorized by Dr. John Alroy, entered by J. Alroy on February 18, 1993
- ^ a b Wang, Xiaoming; Tedford, Richard H. & Taylor B. E. (1999). "Phylogenetic systematics of the Borophaginae (Carnivora: Canidae)". Bulletin of the American Museum of Natural History. 243: 1–391.
- ^ Benton, Michael J.; Philip C.J. Donoghue (2007). "Paleontological Evidence to Date the Tree of Life". Molecular Biology and Evolution. 24 (1): 26–53. doi:10.1093/molbev/msl150. PMID 17047029.
- ^ Wang X (1994). "Phylogenetic systematics of the Hesperocyoninae (Carnivora, Canidae)". Bulletin of the American Museum of Natural History. 221: 1–207.
- ^ Wang, Xiaoming; Tedford, Richard H.; Antón, Mauricio (2010). Dogs: their fossil relatives and evolutionary history. New York: Columbia University Press. pp. 47–48. ISBN 978-0-231-13529-0.
- ^ Paleobiology Database, Collection 17492, Dog Jaw Butte site, Goshen County, Wyoming. Authorized and entered by Dr. John Alroy, March 26, 1995.