File:Neohipparion affine (slender three-toed horse) foot bones (Ash Hollow Formation, Miocene, 11.83 Ma; Ashfall Fossil Beds, Nebraska, USA).jpg

English: Neohipparion affine (Leidy, 1869) - slender three-toed horse foot bones from the Miocene of Nebraska, USA.

This fossil horse foot was excavated from a volcanic ash deposit at Nebraska's Ashfall Fossil Beds. The ash was derived from the Bruneau-Jarbidge Volcanic Field in southwestern Idaho's Snake River Plain. The wind-blown ash buried a vertebrate-rich biota at what was originally a Miocene waterhole.

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From exhibit info.:

EVOLUTION IN ACTION - HORSE FEET -

Was Darwin right? Today's horses have a single toe (hoof) on each foot. Scientists of Darwin's day predicted that ancestral horses with more toes would someday be found as fossils.

Ashfall proved them right! As you can see in these front feet of horse skeletons from the ash bed, most kinds had 3 toes but one has a single hoof.

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Slender Three-toed Horse Neohipparion

The long, slender legs of this three-toed horse show that it was a fast runner. The large functional "side hooves" (one on each side of the main hoof) suggest that it was a good dodger as well and perhaps was better at dealing with soft, treacherous ground than the single-toed horses. Like the other four species of horses found in the ash bed, this one has tall-crowned molar teeth capable of grinding tough, silica-rich grss into digestible mush. The species found at Ashfall, Neohipparion affine, is larger than its ancestors found in older fossil beds and smaller than its descendants found in younger deposits.

Single teeth of Neohipparion can be difficult to distinguish from those of Cormohipparion, hence the question marks about its occurrence above and beow the ash bed.

Remains of this animal have been found: ? In the "RECOVERY" layer (sandstone above the ash) X In the "DISASTER" layer (volcanic ash bed) ? In the "WATERHOLE" layer (sandstone below the ash)

Neohipparion was 4 feet (1.2 meters) at the shoulder.

When the first fossils of three-toed horses were found in Europe, they were named Hipparion. When a skeleton of a similar horse was found later in South Dakota, it was named Neohipparion ('neo' means new) because of its occurrence in the New World.

The Greek word for horse is "hippos" and "-arion" means "small" or "diminutive".

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Classification: Animalia, Chordata, Vertebrata, Mammalia, Perissodactyla, Equidae

Stratigraphy: Cap Rock Member, Ash Hollow Formation, Ogallala Group, Miocene, 11.83 Ma

Locality: Ashfall Fossil Beds State Historical Park, northeastern Nebraska, USA

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Info. at:

en.wikipedia.org/wiki/Ashfall_Fossil_Beds