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Evolutionary and Functional Anatomy of the Pelvic Limb in Fossil and Recent Equidae (Perissodactyla, Mammalia)
Author(s) -
Hussain S.
Publication year - 1975
Publication title -
anatomia, histologia, embryologia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.34
H-Index - 35
eISSN - 1439-0264
pISSN - 0340-2096
DOI - 10.1111/j.1439-0264.1975.tb00637.x
Subject(s) - hock , equidae , anatomy , tarsus (eyelids) , equus , tarsal joint , horse , hindlimb , phalanx , biology , medicine , zoology , surgery , paleontology , eyelid
Summary In Equidae, the limb structure adapted for fore and aft running motion first developed during late Paleocene ( Hyracotherium ). Since then, almost all the modifications contributed in developing a limb structure in which flexion and extension were primary movements. In Hyracotheriinae and Anchitheriinae, the hip and stifle joints were more flexed and had stronger semitendinosus muscles for fore and aft motion of the limb than in Equinae. Hyracotheriinae and Anchitheriinae had unstable hock joint and had significant intertarsal movement. In Hemphillian and earlier Equinae, the intertarsal movement was considerably reduced and in post Hemphillian Equinae it was negligible because of the presence of strong intertarsal ligaments. In the evolution of the horse the development of intertarsal ligaments, reduction of lateral digits and shortening of the astragalar neck contributed in providing the stability at the hock joint. Four types of limb structures are recognized in Equidae: (1) Hyracotheriinae, (2) Anchitheriinae, (3) Tridactyl Equinae, and (4) Monodactyl Equinae. Monodactyl tendencies appeared for the first time in Hemingfordian Parahippus (reduced metatarsals II and IV and their phalanges). The foot structure of this group is more like Equinae rather than Anchitheriinae, and is considered one of the Equinae in this paper. Early Clarendonian Pliohippus was the first equid to achieve monodactylism, but is not in the directancestry of Equus. Dinohippus became monodactyl at about the same time and has more in common with Equus (skull and dental characters) than Pliohippus.