Extinct Horses in GURPS

Horses have a long evolutionary history. Here are some of the species well represented by the fossil record.

• Hippidion was a pony-sized horse from South America's Pleistocene.
• Pliohippus was a pony-sized steppe dweller from the Miocene of North America. Unlike all modern horses, stub toes were still present on either side of its main hoof on all of its feet.
• Protohippus was another three-toed horse from grasslands of North America's Miocene.
• Dinohippus lived in grasslands of North America's late Miocene and early Pliocene.
• Calippus was a dwarf horse from grasslands of North America's Miocene. Various species ranged in mass from 40 kg to 80 kg.
• Astrohippus lived in North American grasslands from the early-mid Miocene to the early Pliocene.
• Hipparion was a three-toed horse found in the plains of North America, Eurasia, and Africa from the Miocene to the Pleistocene.
• Hippotherium was a three-toed horse found in the plains of North America, Eurasia, and Africa from the Miocene to the Pliocene.
• Merychippus was a small, three-toed horse that was the first horse known to be fully adapted for grazing. It lived in North America from the early to middle Miocene.
• Parahippus was a three-toed horse from North America's early miocene. It is intermediate between older forest dwelling horses and the more recent plains dwelling horses, and may have been both a grazer and a browser. It was one of the first horses adapted for high speed over open ground.
• Kalobatippus was a browsing, forest-dwelling horse with long legs, sometimes called the "stilt-walking horse". It lived in North America during the early Miocene.
• Anchitherium was a browsing, forest-dwelling horse that probably descended from Kalobatippus. It originated in North America during the early Miocene, and spread to Eurasia where it survived into the Pliocene.
• Sinohippus is the likely descendant of Anchitherium, a browsing forest dweller of Eurasia's mid to late Miocene and Pliocene.
• Miohippus, despite its name, lived in the Oligocene, in North America's forests and plains. It was likely a mixed browser and grazer.
• Mesohippus represents the start of horse adaptation for plains life. It lived from the late Eocene to middle Oligocene in North America, in both forest and plains. It was likely a mixed browser and grazer, as it adapted to take advantage of the grasses that were spreading across the landscape. It walked on three hoofed toes rather than the single toe of later horses.
• Archaeohippus was a dwarf genus of forest-dwelling horses from North America's early to middle Miocene.
• Megahippus was a specialized browser, with a narrow face for selecting choice morsels from plants. It lived in the middle Miocene of middle North America.
• Hypohippus was a specialized browsing horse, whose three toes distributed its weight across soft forest soils. It was long necked, long bodied, long faced, and short-legged.
• Propalaeotherium was a small, compact, short-legged animal with a body shape more like a pig or tapir than a modern horse. It was a dweller of Eurasia's forests in the middle Eocene.
• Sifrhippus was a tiny forest-dwelling horse from the early Eocene of North America.
• Orohippus was a somewhat deer-like forest dwelling browser from the Eocene of North America. The front feet had four toes, the hind feet had three. Haplohippus and Epihippus were very similar.
• Eohippus was one of the earliest horses, a small deer-like animal from the early Eocene forests of North America. It had four toes on its front feet and three toes on its hind feet, a far cry from modern horses with only one hooved toe. Eohippus may be the same animal as Hyracotherium, or Hyracotherium may be a completely different animal, possibly not even a horse.

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