History of Horses

MacFadden (1994) states that at any granted dodo locality in North America from close to 50-55 to 20-25 million years ago, it is usually possible to find 2-4 species of caters that front to get to lived side-by-side. However, from about 20-10 million years ago, the fossil learn indicates that horses evolved rapidly, adapting to various environments and ways of life. MacFadden (1994) also says that horse diversity increase so dramatically that at some fossil sites from 15 million years ago, as many as a dozen species have been found.

What this suggests, in the view of many professionals, is that a cladogenetic or pronged speciation took attitude during the Eocene and continued into the Oligocene, with rapid diversification becoming characteristic of the early Miocene (Hulbert, 1996). Earlier, MacFadden (1994) and Simpson (1951) agree that an anagenetic macroevolutionary transformation took place, steer to limited diversity and numbers of species. The fossil record, says MacFadden (1992), is an excellent sensitive for examining both anagenesis and cladogenesis. It is the purpose of this report to draw upon the literature to canvass the fossil record from the late Eocene and the Oligocene with specific reference to Miohippus and Mesohippus. such(prenominal) an examination will demonstrate that from the Oligocene period on, cladogenetic evolution of

Ridgeway, W. (1972). The Origin and Influence of the Thoroughbred Horse. unused York: Benjamin Blom.

the horse was occurring - a process that is rooted in the Eocene, but most readily observable in the last mentioned period.

Gould (1987) claims that Simpson held a life-long commitment to the predominant role of evolution by transformational change within populations rather than by accumulation across numerous events of discrete, branching speciation.

However, MacFadden (1992) has convincingly argued that despite the inherent limitations of the fossil record, it is becoming increasingly obvious that during the second half of horse evolution, represented by the adaptive radiation of hypsodont forms, the pattern was unimpeachably cladogenetic. Thus, the following discussion will identify a cladogenetic branching pattern in the North American equine fossil record, beginning in the late Eocene and continuing into and beyond the Oligocene.

MacFadden, B.J. (1999). antediluvian patriarch diets, ecology, and extinction of 5-million-year-old horses from Florida. Science, 283 (5403), 824 - 828.

Simpson, G.G. (1951). Horses. New York: Oxford University Press.

Originating from the late Oligocene Miohippus, two main lines of fall are recognized from the early Miocene of North America. The anchitheres retained the low-crowned, relatively simple teeth and padded feet of Miohippus, but reached a significant size, comparable to modern Equus and achieving a body angle of 200 to 400 kilograms. Ultimately, it was the Equinae in which significant cladogenetic branching took place (Hulbert, 1996). Hulbert (1996) further suggests that the sensory development of Equinae may well have been superior to that of other species, thus facilitating its survival and advancement.

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