The Gray Fossil Site is an Early Pliocene assemblage of fossils dating between 4.5 and 4.9 million years old, located near the community of Gray in Washington County, Tennessee. The site was discovered during road construction on Tennessee State Route 75 by the Tennessee Department of Transportation in May 2000, after which local officials decided to preserve the site for research and education. The site became part of East Tennessee State University, and the Gray Fossil Site & Museum was opened on the site in 2007.
Titanis is a genus of phorusrhacid, an extinct family of large, predatory birds, in the order Cariamiformes that inhabited the United States during the Pliocene and earliest Pleistocene. The first fossils were unearthed by amateur archaeologists Benjamin Waller and Robert Allen from the Santa Fe River in Florida and were named Titanis walleri by ornithologist Pierce Brodkorb in 1963, the species name honoring Waller. The holotype material is fragmentary, consisting of only an incomplete right tarsometatarsus and phalanx, but comes from one of the largest phorusrhacid individuals known. In the years following the description, many more isolated elements have been unearthed from sites from other areas of Florida, Texas, and California. The species was classified in the subfamily Phorusrhacinae, which includes some of the last and largest phorusrhacids like Devincenzia and Kelenken.
Hipparion is an extinct genus of three-toed, medium-sized equine belonging to the extinct tribe Hipparionini, who lived about 10-5 million years ago. While the genus formerly included most hipparionines, the genus is now more narrowly defined as hipparionines from Eurasia spanning the Late Miocene. Hipparion was a mixed-feeder who ate mostly grass, and lived in the savannah biome. Hipparion evolved from Cormohipparion, and went extinct due to environmental changes like cooling climates and decreasing atmospheric carbon dioxide levels.
The evolution of the horse, a mammal of the family Equidae, occurred over a geologic time scale of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the modern horse. Paleozoologists have been able to piece together a more complete outline of the evolutionary lineage of the modern horse than of any other animal. Much of this evolution took place in North America, where horses originated but became extinct about 10,000 years ago, before being reintroduced in the 15th century.
Protohippus is an extinct three-toed genus of horse. It was roughly the size of a modern donkey. Fossil evidence suggests that it lived during the Late Miocene, from about 13.6 Ma to 5.3 Ma.
Pseudhipparion is an extinct genus of three-toed horse endemic to North America during the Miocene. They were herding animals whose diet consisted of C3 plants. Fossils found in Georgia and Florida indicate that it was a lightweight horse, weighing up to 90 pounds. In 2005, fossils were unearthed in Oklahoma. Seven species of Pseudhipparion are known from the fossil record which were very small, following the trend of Bergmann's rule.
Nannippus is an extinct genus of three-toed horse endemic to North America during the Miocene through Pleistocene, about 13.3—1.8 million years ago (Mya), living around 11.5 million years. This ancient species of three-toed horse grew up to 3.5 feet and weighed between 165 pounds to 199 pounds, which was around the same size as a domestic sheep.
Cormohipparion is an extinct genus of horse belonging to the tribe Hipparionini that lived in North America during the late Miocene to Pliocene. They grew up to 3 feet long.
Megahippus is an extinct genus of large Anchitheriine horses found throughout the southern portion of the United States during the middle Miocene. The animal represents one of the latest low-crowned horses, overlapping in time with more derived high-crowned horses.
Astrohippus is an extinct member of the Equidae tribe Equini, the same tribe that contains the only living equid genus, Equus. Fossil remains have been found in the central United States, Florida, and the Mexican states of Chihuahua, Jalisco, and Guanajuato. The fossils date in time from the oldest dating from the Barstovian in the Miocene to the youngest dating in the Hemphillian faunal stage of the early Pliocene.
Archaeohippus is an extinct three toed member of the family Equidae known from fossils of early Oligocene to middle Miocene age. The genus is noted for several distinct skeletal features. The skull possesses deeply pocketed fossa in a notably long preorbital region. The genus is considered an example of phyletic dwarfism with adults estimated at being on average 20 kilograms in weight. This is in contrast to the most common equid of the period, Miohippus. Characters of the teeth show a mix of both primitive and advanced traits. The advanced traits are very similar to those shown in the genus Parahippus. The noted similarities of Archaeohippus and Parahippus show them to be descended from a common ancestor. They are considered sister species.
The Thomas Farm site is an Early Miocene, Hemingfordian assemblage of vertebrate fossils located in Gilchrist County, northern Florida.
Hippotherium is an extinct genus of horse that lived in during the Miocene through Pliocene ~13.65—6.7 Mya, existing for 6.95 million years.
The Alachua Formation is a Miocene geologic formation in Florida. The claystones, sandstones and phosphorites of the formation preserve many fossils of mammals, birds, reptiles and fish, among others megalodon.
The Ash Hollow Formation of the Ogallala Group is a geological formation found in Nebraska and South Dakota. It preserves fossils dating back to the Neogene period. It was named after Ash Hollow, Nebraska and can be seen in Ash Hollow State Historical Park. Ashfall Fossil Beds State Historical Park is within this formation.
The Valentine Formation is a geologic unit formation or member within the Ogallala unit in northcentral Nebraska near the South Dakota border. It preserves fossils dating to the Miocene epoch of the Neogene period and is particularly noted for Canid fossils. This unit consists of loosely-consolidated sandstone that crumbles easily. These sands carry the water of the Ogallala Aquifer and is the source of much of the water in the Niobrara River. A particular feature of the Valentine is lenticular beds of green-gray opaline sandstone that can be identified in other states, including South Dakota, Nebraska, Kansas, and Colorado. Although three mammalian fauna stages can be mapped throughout the range of the Ogallala, no beddings of the Ogallala are mappable and all attempts of formally applying the Valentine name to any mappable lithology beyond the type location have been abandoned. Even so, opaline sandstone has been used to refer to this green-gray opalized conglomerate sandstone that is widely found in the lower Ogallala Formation.
The Gracias Formation is a geologic formation in Honduras. The mainly sandstones, siltstones and claystones preserve vertebrate fossils dating back to the Neogene period.
The Cucaracha Formation (Tca) is a geologic formation in Panama. It preserves vertebrate and plant fossils dating back to the Neogene period; Early to Middle Miocene epochs (Hemingfordian). Fossils of the crocodylian Centenariosuchus, the turtle Rhinoclemmys panamaensis and the artiodactyl Paratoceras have been found in the formation.
Sivalhippus is an extinct genus of horse that lived in Africa and the Indian subcontinent during the late Miocene.
Calippus is an extinct genus of hoofed mammals in the horse family (Equidae), known from the Middle Miocene through the Early Pliocene of North and Central America. Fossils have been found in the Central United States and the Eastern United States, ranging south to Honduras. These equines had high crowned teeth and a quadrangular, wide muzzle, and were small compared to their contemporary relatives, with C. elachistus weighing 49 kg, C. cerasinus weighing 102 kg, 132 kg for C. theristes and 73 kg for C. mccartyi.
