Borophaginae

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Borophaginae
Temporal range: 34–2.5 
Ma
Oligocene-Earliest Pleistocene
Aelurodon stirtoni
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Subfamily: Borophaginae
Simpson (1945)[1]
Genera

See text

The extinct Borophaginae form one of three

endemic to North America during the Oligocene to Pliocene and lived roughly 34—2.5 million years ago, existing for about 33.5
million years.

Origin

Canid subfamilies
 Canidae 

Hesperocyoninae

Borophaginae

Caninae

The Borophaginae descended from the subfamily Hesperocyoninae. The earliest and most primitive borophagine is the genus Archaeocyon, which is a small fox-sized animal mostly found in the fossil beds in western North America. The borophagines soon diversified into several major groups. They evolved to become considerably larger than their predecessors, and filled a wide range of niches in late Cenozoic North America, from small omnivores to powerful, bear-sized carnivores, such as Epicyon.[5]

Species

There are 66 identified borophagine species, including 18 newly identified species that range from the

Aelurodontina, and Borophagina (all erected as new tribes or subtribes). The Borophaginae begins with a group of small fox-sized genera, such as Archaeocyon, Oxetocyon, Otarocyon, and Rhizocyon, in the Orellan through early Arikareean stages.[5]
These canids reached their maximum diversity of species around 28 million years ago.

Often generically referred to as "bone-crushing dogs" for their powerful

phylogeny, showing that the group was highly diverse in its heyday.[5] All Borophaginae had a small fifth toe on their rear feet (similar to the toes that bear dew claws on the front feet), where as all modern Caninae have only four toes normally.[7]

Noteworthy genera in this group are

.

Phylogeny of borophagines by R.L. Tedford, 1977
Fluctuation of species within Canidae over 40 million years

Classification

Borophagine taxonomy, following Wang et al.[5] (million years=in existence)

Cladogram showing borophagine interrelationships, following Wang et al., figure 141:[5]

Extinction

According to an analysis of the fossil record of North American fossil

felids and canines.[8] Felids invaded the continent from Eurasia about 20 million years ago and were better ambush predators, in part due to their retractable claws.[9] Climate change, which led to the replacement of North American forests with grasslands, may also have been a factor;[10] borophagines were less suited to running down prey than canines.[8]
Although these specific species developed powerful limbs that are capable of cracking bones in vicious pounce attacks, other carnivorous species that rely on quick ambush for catching prey were likely more successful than the slower Borophaginae. [11]

References

Further reading