Hipparionini

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Hipparionini: A short, simple overview

What is Hipparionini?
Hipparionini is an extinct group (a tribe) of three-toed horses in the horse family (Equidae). They looked similar to modern horses but had three toes on each foot and high-crowned teeth. They lived from the Early Miocene to the Early Pleistocene.

Where and when they lived
- Origin: North America, about 17 million years ago.
- Migration: They spread to the Old World (Europe, Asia, Africa) around 11 million years ago, with Africa reached a bit later and Asia there first, followed by Africa.
- Last members: In the Old World, they survived until about 1 million years ago in some areas. In North America, their numbers declined earlier and only small forms remained before they disappeared.

Size and build
- Hipparionini ranged from small to fairly large: a few species were as light as about 23 kg (50 lb), while others exceeded 300 kg (660 lb).
- They had longer leg bones than modern horses and three toes on each foot.
- Teeth were high-crowned, useful for tougher wear from grazing.

Evolution and spread
- They began in North America and became very diverse there during the Middle to Late Miocene.
- They moved into Eurasia and Africa, where they diversified even more in the Late Miocene to Early Pliocene.
- By the end of the Miocene, many Old World lines were already going extinct. In the Pliocene, some hipparionines grew larger and developed higher-crowned teeth to cope with changing environments.
- Around 2.6 million years ago, a group of Equus horses arrived in Eurasia and competed with hipparionines.
- Final Old World hipparionines include species like Proboscidipparion sinense (China) and Eurygnathohippus cornelianus (Africa), dating to the end of the Early Pleistocene.

Ecology (how they lived)
- In North America, some hipparionines were mixed feeders, eating both leaves and grasses.
- In the Old World, they started as browsers and mixed feeders, later showing a greater shift toward grazing in many groups.
- They showed niche differences in some regions, with smaller species browsing or mixing diets, while larger species tended to graze.
- Predators likely included saber-toothed cats, bear-dogs, and other Miocene-Pliocene carnivores.

Taxonomy (how scientists classify them)
North American genera:
- Hipparion (distinct from Old World species)
- Neohipparion
- Pseudhipparion
- Nannippus
- Cormohipparion

Old World genera (many descended from Cormohipparion):
- Hipparion (sensu stricto)
- Hippotherium
- Cremohipparion
- Sivalhippus
- Eurygnathohippus
- Plesiohipparion
- Proboscidipparion
- Shanxihippus

Key takeaway
Hipparionini were an important and diverse group of three-toed horses that thrived for millions of years across North America, Eurasia, and Africa. They adapted to different environments, but they eventually gave way to modern horses of the genus Equus as climates changed and new competitors arrived.