Hesperocyoninae

From Palaeos.org

Introduction

Hesperocyoninae is most basal subfamily of Canidae. They first appear in fossil record at late Eocene of North-America. The early forms, such as Hesperocyon and Prohesperocyon, were small animals 1-2 kg in weight. They also were rather unspecialized and shared many anatomical features with their ancestral miacids. They remained as such till the end of Eocene but global cooling and the spread of grasslands that mark the beginning of Oligocene caused explosive radiation of Hesperocyonines. This was their hayday. their average body size incresed and specialized hypercarnivorous (Enhydrocyon) and hypocarnivorous (Osbornodon renjiei) forms evolved. Hesperocyonines remained diverse group troughout the Oligocene but at the earliest Miocene the hesperocyonine diversity started to decline. Last of the Hesperocyonine radiation was large (21 Kg) carnivorous form, Osbornodon fricki. By mid Miocene it too was extinct.

Characters

• Low septum in the bullae
• Medially located P4 protocone
• Elongated carnassial
• Reduced or lost anterior cingulum on M1
• Trenchant talonid of M1 (except in Osbornodon) in contrast to the basined talonids in the Borophaginae and the Caninae
• Absence of a metaconule in M1

  o HESPEROCYONINAE
  |
  `--+-- Prohesperocyon wilsoni
     `--+-- "Hesperocyon" pavidus
        |-- Hesperocyon gregarius
        |-- Caedocyon tedfordi
        |--+-- Ectopocyon antiquus
        |  `--+-- Ectopocyon intermedius
        |     `-- Ectopocyon simplicidens
        |
        |--+-- Paraenhydrocyon josephi
        |  `--+-- Paraenhydrocyon robustus
        |     `-- Paraenhydrocyon wallovianus
        |
        `--+-- "Hesperocyon" coloradensis
           `--+--  "Mesocyon" temnodon
              |--+-- Mesocyon brachyops
              |  |-- Mesocyon coryphaeus
              |  |--+-- Sunkahetenka geringensis
              |  |  `--+-- Philotrox condoni
              |  |     `--+-- Enhydrocyon pahinsintewakpa
              |  |        `--+-- Enhydrocyon crassidens
              |  |           `--+-- Enhydrocyon Stenocephalus
              |  |              `-- Enhydrocyon basilatus
              |  |
              |  `--+-- Cynodesmus thooides
              |     `-- Cynodesmus martini
              |
              `--+-- Osbornodon renjiei
                 `--+-- Osbornodon sesnoni
                    `--+-- Osbornodon lamonensis
                       `--+-- Osbornodon brachypus
                          `-- Osbornodon fricki

References

• Wang & Tedford: Mammoths, Dogs their fossil relatives & evolutionary history, Columbia University Press, 2008
• Wang, X. 1994. Phylogenetic systematics of the Hesperocyoninae (Carnivora, Canidae). Bulletin of the American Museum of Natural History, 221:1-207.