Английская Википедия:Borophaginae

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The extinct Borophaginae form one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Hesperocyoninae and extant Caninae. Borophaginae, called "bone-crushing dogs", were endemic to North America during the Oligocene to Pliocene and lived roughly 34—2.5 million years ago, existing for about Шаблон:Mya.

Origin

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.

Species

There are 66 identified borophagine species, including 18 newly identified species that range from the Orellan to Blancan ages. A phylogenetic analysis of the species was conducted using cladistic methods, with Hesperocyoninae as an archaic group of canids, as the outgroup. Aside from some transitional forms, Borophaginae can be organized into four major clades: Phlaocyonini, Cynarctina, 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. 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 ecosystems. Their good fossil record has also allowed a detailed reconstruction of their phylogeny, showing that the group was highly diverse in its heyday. 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.

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 (which they were a part of), Hyaenidae, and Procyonidae.

Файл:Wang Borophagine Construct.png

Phylogeny of borophagines by R.L. Tedford, 1977

Файл:Canidae Species Divesity.png

Fluctuation of species within Canidae over 40 million years

Classification

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

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

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

Extinction

According to an analysis of the fossil record of North American fossil carnivorans, the decline of borophagines from a diversity of about 30 species 15 million years ago to extinction was largely driven by competition with felids and canines. Felids invaded the continent from Eurasia about 20 million years ago and were better ambush predators, in part due to their retractable claws. Climate change, which led to the replacement of North American forests with grasslands, may also have been a factor; borophagines were less suited to running down prey than canines. 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.

Further reading

• Шаблон:Cite book
• Шаблон:Cite book