Pliohippus Tooth-Oklahoma 005

Taxa: Pliohippus sp.

Geology: Ogallala formation

Age: Pliocene

Locality: Texas County, Oklahoma

Size: 2.5x0.5x1" or 6.8x2.7x1.3 cm

 No repairs or restorations

Pliohippus

Pliohippus is an extinct genus of three-toed equid that lived during the Miocene epoch in North America, thriving from about 15 to 5 million years ago. Although historically misidentified as a direct ancestor of the modern horse due to its single-hoof-like appearance in early reconstructions, it was actually a close side-branch characterized by prominent side toes that did not touch the ground, robust limbs, and relatively straight, high-crowned teeth adapted for grazing on harsh, open-country grasses. As one of the most successful and widespread savanna-dwelling horses of its time, Pliohippus represents a key transitional phase in equid evolution, showcasing the adaptive shift from forest-dwelling browsers to fast-running grazers of the expanding grasslands.

Ogallala Formation

The Ogallala Formation is a vast, continental geologic deposit stretching across the central High Plains of the United States, from South Dakota down to Texas. Laid down primarily during the Miocene and early Pliocene epochs, it consists of gravel, sand, silt, and clay eroded from the rising Rocky Mountains and spread eastward by a network of braided streams and rivers. Interbedded with occasional volcanic ash falls and hardened caliche layers, this thick blanket of sediment forms the primary geological host for the Ogallala Aquifer, one of the world's largest underground freshwater reservoirs that sustains the vital agricultural economy of the American Great Plains.