Protoceratidae is an extinct family of

herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

artiodactyls Artiodactyls are placental mammals belonging to the order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other thre ...

(even-toed ungulates) that lived during the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

through

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Ruminantia Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, principa ...

Tylopoda Tylopoda (meaning "calloused foot") is a suborder of terrestrial herbivorous even-toed ungulates belonging to the order Artiodactyla. They are found in the wild in their native ranges of South America and Asia, while Australian feral camel ...

Classification

Protoceratidae was erected by

Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of paleontology. A prolific fossil collector, Marsh was one of the preeminent paleontologists of the nineteenth century. Among his legacies are the discovery or ...

in 1891, with the type genus '' Protoceras'' and assigned to the

Artiodactyla Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof ...

. It was later assigned to

Pecora Pecora is an Order (biology), infraorder of Artiodactyla, even-toed hoofed mammals with ruminant digestion. Most members of Pecora have cranial appendages projecting from their frontal bones; only two extant genera lack them, ''Hydropotes'' and ...

, and more recently to

Ruminantia Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, principa ...

. However, recently a relationship to

chevrotain Chevrotains, or mouse-deer, are small, even-toed ungulates that make up the family Tragulidae, and are the only living members of the infraorder Tragulina. The 10 extant species are placed in three genera, but several species also ar ...

s in the infraorder

Tragulina Tragulina (also known as Traguliformes) is an infraorder of even-toed ungulates. Only the chevrotains survive to the present, including the genera ''Tragulus'' (the mouse deer) and '' Hyemoschus'', all within the family Tragulidae. Taxonomy and ...

has been proposed.

Morphology

When alive, protoceratids would have resembled

deer A deer (: deer) or true deer is a hoofed ruminant ungulate of the family Cervidae (informally the deer family). Cervidae is divided into subfamilies Cervinae (which includes, among others, muntjac, elk (wapiti), red deer, and fallow deer) ...

, though they were not directly related. Protoceratids ranged from 1 to 2 m in length, from about the size of a roe deer to an

elk The elk (: ''elk'' or ''elks''; ''Cervus canadensis'') or wapiti, is the second largest species within the deer family, Cervidae, and one of the largest terrestrial mammals in its native range of North America and Central and East Asia. ...

. Unlike many modern ungulates, they lacked

cannon bone The limbs of the horse are structures made of dozens of bones, joints, muscles, tendons, and ligaments that support the weight of the equine body. They include three apparatuses: the suspensory apparatus, which carries much of the weight, preve ...

s in their legs. Their dentition was similar to that of modern deer and cattle, suggesting they fed on tough grasses and similar foods, with a complex stomach similar to that of

camel A camel (from and () from Ancient Semitic: ''gāmāl'') is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provid ...

s. At least some forms are believed to have lived in

herd A herd is a social group of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with this is called '' herding''. These animals are known as gregarious animals. The term ''herd'' ...

s. The most dramatic feature of the protoceratids, however, were the horns of the males. In addition to having horns in the more usual place, protoceratids had additional, rostral horns above their noses. These horns were either paired, as in '' Syndyoceras'', or fused at the base, and branching into two near the tip, as in ''

Synthetoceras ''Synthetoceras tricornatus'' is a large, extinct Protoceratidae, protoceratid, endemic to North America (Nebraska) during the Late Miocene, 12.5—4.7 Annum, Ma, existing for approximately . Fossils have been recovered from Nebraska and Texas. ...

''. In life, the horns were probably covered with skin, much like the

ossicone Ossicones are columnar or conical skin-covered bone structures on the heads of giraffes, male okapi, and some of their extinct relatives. Ossicones are distinguished from the superficially similar structures of Horn (anatomy), horns and antlers ...

s of a

giraffe The giraffe is a large Fauna of Africa, African even-toed ungulate, hoofed mammal belonging to the genus ''Giraffa.'' It is the Largest mammals#Even-toed Ungulates (Artiodactyla), tallest living terrestrial animal and the largest ruminant on ...

. The females were either hornless, or had far smaller horns than the males. Horns were therefore probably used in sexual display or competition for mates. In later forms, the horns were large enough to have been used in sparring between males, much as with the

antler Antlers are extensions of an animal's skull found in members of the Cervidae (deer) Family (biology), family. Antlers are a single structure composed of bone, cartilage, fibrous tissue, skin, nerves, and blood vessels. They are generally fo ...

s of some modern deer.

Genera by epoch

Eocene

* '' Heteromeryx'' * '' Leptoreodon'' * ''

Leptotragulus ''Leptotragulus'' is an extinct genus of protoceratid, endemic to North America. It lived during the Middle Eocene epoch (Uintan to Chadronian stage) 40.2—33.9 Ma, existing for approximately .It was invented by a famous scientist Lev Levich E ...

'' * '' Poabromylus'' * '' Pseudoprotoceras'' * '' Toromeryx'' * '' Trigenicus''

Oligocene

* '' Protoceras''

Miocene

* '' Paratoceras'' * '' Lambdoceras'' * ''

Prosynthetoceras ''Prosynthetoceras'' is an extinct genus of Artiodactyla, of the family Protoceratidae, endemic to North America. It lived from the Early to Middle Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period a ...

'' * ''

'' * '' Syndyoceras''

Pliocene

* '' Kyptoceras''

References

{{Taxonbar, from=Q133821 Eocene Artiodactyla Miocene Artiodactyla Pliocene Artiodactyla Zanclean extinctions Prehistoric mammals of North America Prehistoric mammal families