Pliohippus
Skull, skeletal and foot of Pliohippus
- USA
- Mexico
Pliohippus is an extinct genus of the family Equidae that lived from the Middle Miocene to the Lower Pliocene before 16 to around 5 million years ago on the North American continent and in Central America.
Features
Pliohippus was a relative of today's horse of the genus Equus, resembling those already quite significantly, but was still slightly smaller and probably reached a maximum of the dimensions of the smallest known today Equus species, the weight was about 170 kg. A clear link to recent representatives is the presence of only a single toe per limb, which was also designed quite wide, which is a total to be interpreted as adaptations to life in the open grassy landscape and for rapid locomotion on the hard desert ground. However, there were two small lateral toes reduced ( splint bones ). A striking difference is the presence of a facial fossa ( fossa präorbitale ). Such pit formation is typical of the Neogene horses, but went lost in Equus. She was nearing the orbit, reaching a diameter of approximately 15 mm, it was almost completely surrounded by Knochenwülsten. The dentition consisted of the complete dentition of modern mammals, in contrast to most of today's horses Pliohippus had thus still a functional first premolars. In particular, the posterior dentition consisted of hochkronigen ( hypsdonten ) molars with strongly curved enamel wrinkles that were ideally suited to chew the tough grass food. However, the melting crease pattern differed somewhat from those of today's horses and were designed primitive. The molars reached crown heights from 5 to 6.5 cm, the entire Kaureihe was 14 to 18 cm long.
Fossil finds
Pliohippus was common during the Middle Miocene to the Lower Pliocene to around 16-5 million years over large parts of North America and is a very dominant herbivores have been. Proved it's of California in the west over the Great Plains in the north to the coast on the Gulf of Mexico to the east and south into Mexico. Significant findings come in part from the Mint Canyon Formation of the Upper Miocene, where, among other things, a nearly complete skull was discovered. A partial skeleton from the area of the Niobrara River in Nebraska served as the holotype for the first description. Part of complete skeletons are from the Ash Hollow Formation, which is also common in Nebraska. The animals arrived at the beginning of the Upper Miocene by a massive volcanic eruption to death. Very far south are finds from Oaxaca in Mexico include several molars and also provide Represents the phylogenetically oldest known material
Paleobiology
Not only the hochkronigen teeth of Pliohippus indicate a specialization on hard grass food, even by isotope studies could this be determined. The very far located in the south of Mexico finds from Oaxaca let's assume that was not only adapted to dry and cool steppe conditions, the equines but coped well with warmer climates. But they lived in large parts of its distribution in what is now southern part of the United States in open bush and grasslands, where it is assumed that an annual rainfall especially in the late Miocene from 1220 to 1360 mm.
System
Hipparionini
Protohippus
Calippus
Scaphohippus
Pliohippus
Astrohippus
Onohippus
Dinohippus
Equus
Pliohippus is an extinct genus of the family Equidae ( horses) and is presented within this in the modern subfamily equinae, which is characterized by a better adaptation to grass food and thereby developed hypsodont teeth. Here again, it belongs to the tribe of Equini and the subtribes of Pliohippina where it is placed at the base. Thus Pliohippus is the sister taxon to all other modern horses. The Pliohippina include einhufigen horses, a trait that all of today's representatives of the genus Equus have. Pliohippina in turn represent the sister group of the Protohippina that are designed somewhat primitive. The Equini in turn, are compared with the Hipparionini. As the closest relative to Pliohippus applies Astrohippus, which was originally performed as a subgenus of Pliohippus.
1874 The name was introduced pernix by Othniel Charles Marsh on the basis of a partial skeleton from Nebraska along with the type species P.. Later in 1918, Henry Fairfield Osborn differed total of 16 different species, of which some are today but too Equus, others Astrohippus and Dinohippus. Currently, a total of five species of the genus Pliohippus are recognized:
- P. fossulanus Cope, 1893
- P. mirabilis Leidy, 1858
- P. nobilis Osborn, 1918
- P. pernix Marsh, 1874
- Tantalus P. Merriam, 1913