Borophaginae

The subfamily Borophaginae is an extinct group of canids called "bone crushing dogs"^[1] that were endemic to North America during the Oligocene to Pliocene and lived roughly 36—2.5 million years ago and existing for approximately 33.5 million years.^[2]

Origin

The Borophaginae apparently 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.^[2][3]

Species

Borophagines are a total of 66 species that includes 18 new species which range from Orellan through Blancan ages. A phylogenetic analysis using cladistic methods with Hesperocyoninae as an archaic group of canids, as the outgroup. Most of the Borophaginae, aside from some transitional forms, can be organized in four major clades: Phlaocyonini, Cynarctina, Aelurodontina, and Borophagina (all erected from 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.^[4] These canids reached their maximum diversity of species around 28 million years ago.

Often generically referred to as "bone-crushing dogs" for their powerful teeth and jaws, and hyena-like features (although their dentition was more primitive than that of hyenas), their fossils are abundant and widespread; in all likelihood, they were probably one of the top predators of their ecosystem.^[3][1] Their good fossil record has also allowed a detailed reconstruction of their phylogeny, showing that the group was highly diverse in its heyday.^[3]

Noteworthy genera in this group are Aelurodon, Epicyon, and Borophagus (=Osteoborus). According to Xiaoming Wang, the Borophaginae played broad ecological roles that are performed by at least three living carnivoran families, Canidae, Hyaenidae, and Procyonidae.

Classification

Borophagine taxonomy, following Wang et al.^[3]

• Family Canidae

(million years=in existence)

• • Subfamily †Borophaginae
    • †Archaeocyon 33—26 Ma, existing 7 million years
    • †Oxetocyon 33—28 Ma, existing 4 million years
    • †Otarocyon 34—30 Ma, existing 4 million years
    • †Rhizocyon 33—26 Ma, existing 4 million years
    • Tribe †Phlaocyonini 33—13 Ma, existing 20 million years
      • †Cynarctoides 30—18 Ma, existing 12 million years
      • †Phlaocyon 30—19 Ma,11 million years
    • Tribe †Borophagini 30—3 Ma, existing 27 million years
      • †Cormocyon 30—20 Ma, existing 10 million years
      • †Desmocyon 25—16 Ma, existing 9 million years
      • †Metatomarctus 19—16 Ma, existing 3 million years
      • †Euoplocyon 18—16 Ma, existing 2 million years)
      • †Psalidocyon 16—13 Ma, existing 7 million years
      • †Microtomarctus 21—13 Ma, existing (7 million years
      • †Protomarctus 20—16 Ma, existing (4 million years
      • †Tephrocyon 16—14 Ma, existing 2.7 million years
      • Subtribe †Cynarctina 20—10 Ma, existing 10 million years
        • †Paracynarctus 19—16 Ma, existing 3 million years
        • †Cynarctus 16—12 Ma, existing 4 million years
      • Subtribe †Aelurodontina 20—5 Ma, existing 15 million years
        • †Tomarctus 23—16 Ma, existing 7 million years
        • †Aelurodon 16—12 Ma, existing 4 million years
      • Subtribe †Borophagina
        • †Paratomarctus 16—5 Ma, existing 11 million years
        • †Carpocyon 16—5 Ma, existing 11 million years
        • †Protepicyon 16—12 Ma, existing 2.7 million years
        • †Epicyon 12—10 Ma, existing 2 million years
        • †Borophagus (=Osteoborus) 12—5 Ma, existing (7 million years

Cladogram showing borophagine interrelationships, following Wang et al., figure 141:^[3]

References

• ^ Alan Turner, "National Geographic: Prehistoric Mammals" (Washington, D.C.: Firecrest Books Ltd., 2004), pp. 112–114. ISBN 0-7922-7134-3

Additional Reading

• 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