Protoceratidae is an extinct family of

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

n artiodactyls (even-toed ungulates) that lived during the

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

through

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among ...

in 1891, with the type genus ''

Protoceras ''Protoceras'' ('first horns') is an extinct genus of Artiodactyla, of the family Protoceratidae, endemic to North America. It lived from the Oligocene to the Early Miocene 33.3—16.0 Ma, existing for approximately . Morphology ''Protoceras ...

'' and assigned to the

Artiodactyla The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...

. It was later assigned to

Pecora Pecora is an infraorder of 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 '' Moschus''. The name “P ...

, and more recently to

Ruminantia Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...

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 camels ...

. However, recently a relationship to

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

s in the infraorder Tragulina has been proposed.

Morphology

When alive, protoceratids would have resembled

deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the re ...

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

roe deer The roe deer (''Capreolus capreolus''), also known as the roe, western roe deer, or European roe, is a species of deer. The male of the species is sometimes referred to as a roebuck. The roe is a small deer, reddish and grey-brown, and well-adapt ...

to an elk. Unlike many modern ungulates, they lacked

cannon bone Good conformation in the limbs leads to improved movement and decreased likelihood of injuries. Large differences in bone structure and size can be found in horses used for different activities, but correct conformation remains relatively simil ...

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: la, camelus and grc-gre, κάμηλος (''kamēlos'') from Hebrew or Phoenician: גָמָל ''gāmāl''.) is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. ...

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'' i ...

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''. 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 horns and antlers by their uniqu ...

s of a

giraffe The giraffe is a large African hoofed mammal belonging to the genus ''Giraffa''. It is the tallest living terrestrial animal and the largest ruminant on Earth. Traditionally, giraffes were thought to be one species, '' Giraffa camelopardal ...

. 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. Antlers are a single structure composed of bone, cartilage, fibrous tissue, skin, nerves, and blood vessels. They are generally found only on ...

s of some modern deer.

Genera by epoch

Eocene

* '' Heteromeryx'' * '' Leptoreodon'' * '' Leptotragulus'' * '' Poabromylus'' * ''

Pseudoprotoceras ''Pseudoprotoceras'' is an extinct genus of Artiodactyla, of the family Protoceratidae, endemic to central North America. It lived during the Late Eocene 37.2—33.9 Ma, existing for approximately . ''Pseudoprotoceras'' resembled hornlessEmry, R ...

'' * ''

Toromeryx ''Toromeryx'' is a medium-sized extinct genus of Artiodactyla, of the family Protoceratidae, endemic to southwestern North America from the Eocene epoch (Late Uintan stage) 46.2—42 Ma, existing for approximately . Taxonomy ''Toromeryx'' was n ...

'' * '' Trigenicus''

Oligocene

* ''

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 20.6—13.6 Ma, existing for approximately . In appearance, ''Prosynthetoceras'' looke ...

'' * '' Synthetoceras'' * '' Syndyoceras''

Pliocene

* '' Kyptoceras''

References

{{Taxonbar, from=Q133821 Eocene even-toed ungulates Miocene even-toed ungulates Pliocene even-toed ungulates Zanclean extinctions Prehistoric mammals of North America Prehistoric mammal families