Oromerycidae
Encyclopedia
Oromerycidae is a small (both in size and diversity) extinct family
of artiodactyls (even-toed hoofed mammal
s) closely related to living camel
s, known from the middle to late Eocene
of western North America
.
Oromerycids are placed in the artiodactyl suborder Tylopoda
, which also includes camels and a variable number of extinct families such as Protoceratidae
. Some researchers have viewed the similarity to camels as strong enough to warrant placement of oromerycids within the family Camelidae as a subfamily, Oromerycinae, but most have favored placement in a distinct family, albeit a closely related one.
Oromerycids were very similar to early members of other tylopod families, but they lack the specializations of those families, such as the bony protuberances on the skull
s of protoceratids or the strongly elongate limbs of camels. Like other tylopods, oromerycids had selenodont teeth and gracile limbs. In fact, oromerycids show only a few specializations that distinguish them from other tylopods, the most notable being fusion of the radius
and ulna
in the forearm
and the presence of a cleft between the entoconid and hypoconulid cusp
s on the last lower molar
.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of artiodactyls (even-toed hoofed mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s) closely related to living camel
Camel
A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...
s, known from the middle to late Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of western North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
Oromerycids are placed in the artiodactyl suborder Tylopoda
Tylopoda
Tylopoda is a suborder of terrestrial herbivorous even-toed ungulates belonging to Artiodactyla. They are extant in the wild in their native ranges of South America and Asia, while Australian feral camels are an introduced species. The group has a long fossil history in North America and Europe...
, which also includes camels and a variable number of extinct families such as Protoceratidae
Protoceratidae
Protoceratidae is an extinct family of herbivorous North American artiodactyls that lived during the Eocene through Pliocene at around 46.2—4.9 Ma., existing for approximately .-Taxonomy:...
. Some researchers have viewed the similarity to camels as strong enough to warrant placement of oromerycids within the family Camelidae as a subfamily, Oromerycinae, but most have favored placement in a distinct family, albeit a closely related one.
Oromerycids were very similar to early members of other tylopod families, but they lack the specializations of those families, such as the bony protuberances on the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
s of protoceratids or the strongly elongate limbs of camels. Like other tylopods, oromerycids had selenodont teeth and gracile limbs. In fact, oromerycids show only a few specializations that distinguish them from other tylopods, the most notable being fusion of the radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
and ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
in the forearm
Forearm
-See also:*Forearm flexors*Forearm muscles...
and the presence of a cleft between the entoconid and hypoconulid cusp
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...
s on the last lower molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
.