| Merriamoceros Temporal range: Early Miocene, | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | Antilocapridae |
| Subfamily: | † Merycodontinae |
| Genus: | † Merriamoceros Merriam, 1913 |
| Species: | †M. coronatus |
| Binomial name | |
| †Merriamoceros coronatus Merriam, 1913 | |
Merriamoceros is an extinct genus of pronghorn. It is known from a single species, which is also the type species, M. coronatus.
The type specimen (UCMP 20052) that defines this species is named Merriamoceros coronatus taking after its discoverer, J.M. Merriam. It is known from a partial skull (a single fragmentary horn or antler). Remains of Merriamoceros were found in rock formations dating to the Early Miocene period, 15.9 to 13.6 million years ago. Its type locality is Barstow, which is in a Barstovian terrestrial horizon in the Barstow Formation of California. [1]
Merriamoceros was originally named as a subspecies of Ramoceros , but later J. T. Gregory elevated it to a generic level, stating that its palmate style horns were distinct characteristics and required a separate classification. [2] The developmental series discussed by C. Frick further supports the hypothesis of homology between the horns of Ramoceros and Merriamoceros, with young Merriamoceros presenting three horns, reminiscent of those of Paramoceros . [3] The horn ontogeny of these two separate genera marks an evolutionarily distinct lineage. [4]
Merriamoceros was a prehistoric relative of modern pronghorn ( Antilocapra americana ), which is a species of artiodactyl mammal indigenous to interior western and central North America. Its remains were found in California, and were characterized by a small body size and palmate horns. [4] It is the oldest known member of the Antilocapridae family, also known as the pronghorns. [1] It was closely related to Ramoceros and Merycodus .
It was, like its relatives, a quadruped herbivore and grazed on the grassy plains of its time. It is not known if Merriamoceros had any predators and much is still unknown about its paleobiology, but it is assumed that it was similar to the present day pronghorn and its extinct relatives. Merriamoceros was covered in a short fur and was likely a good runner. Merriamoceros had some of the most intricate cranial appendages in the family, where the tines were on top and along the outside edges of the horns. Like related species, these were likely initially covered in skin, which gradually rubbed off to expose the bone. [1]
Ungulates are members of the diverse clade Euungulata which primarily consists of large mammals with hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined to be a polyphyletic and thereby invalid clade based on molecular data. As a result, true ungulates had since been reclassified to the newer clade Euungulata in 2001 within the clade Laurasiatheria while Paenungulata has been reclassified to a distant clade Afrotheria. Living ungulates are divided into two orders: Perissodactyla including equines, rhinoceroses, and tapirs; and Artiodactyla including cattle, antelope, pigs, giraffes, camels, sheep, deer, and hippopotamuses, among others. Cetaceans such as whales, dolphins, and porpoises are also classified as artiodactyls, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving. Two other orders of ungulates, Notoungulata and Litopterna, both native to South America, became extinct at the end of the Pleistocene, around 12,000 years ago.
Artiodactyls are mammals belonging to the order Artiodactyla. Typically, they are ungulates which bear weight equally on two of their five toes: the third and fourth, often in the form of a hoof. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, most perissodactyls bear weight on an odd number of the five toes. Another difference between the two is that many artiodactyls digest plant cellulose in one or more stomach chambers rather than in their intestine as perissodactyls do. The advent of molecular biology, along with new fossil discoveries, found that cetaceans fall within this taxonomic branch, being most closely related to hippopotamuses. Some modern taxonomists thus apply the name Cetartiodactyla to this group, while others opt to include cetaceans within the existing name of Artiodactyla. Some researchers use "even-toed ungulates" to exclude cetaceans and only include terrestrial artiodactyls, making the term paraphyletic in nature.
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 "Pecora" comes from the Latin word pecus, which means "cattle". Although most pecorans have cranial appendages, only some of these are properly called "horns", and many scientists agree that these appendages did not arise from a common ancestor, but instead evolved independently on at least two occasions. Likewise, while Pecora as a group is supported by both molecular and morphological studies, morphological support for interrelationships between pecoran families is disputed.
The Antilocapridae are a family of artiodactyls endemic to North America. Their closest extant relatives are the giraffids. Only one species, the pronghorn, is living today; all other members of the family are extinct. The living pronghorn is a small ruminant mammal resembling an antelope.
Hayoceros is an extinct genus of the artiodactyl family Antilocapridae, endemic to North America during the Pleistocene epoch, existing for about 1.5 million years.
Stupendemys is an extinct genus of freshwater side-necked turtle, belonging to the family Podocnemididae. It is the largest freshwater turtle known to have existed, with a carapace over 2 meters long. Its fossils have been found in northern South America, in rocks dating from the Middle Miocene to the very start of the Pliocene, about 13 to 5 million years ago. Male specimens are known to have possessed bony horns growing from the front edges of the shell and the discovery of the fossil of a young adult shows that the carapace of these turtles flattens with age. A fossil skull described in 2021 indicates that Stupendemys was a generalist feeder.
Daeodon is an extinct genus of entelodont even-toed ungulates that inhabited North America about 23 to 20 million years ago during the latest Oligocene and earliest Miocene. The type species is Daeodon shoshonensis, described by a very questionable holotype by Cope. Some authors synonymize it with Dinohyus hollandi and several other species, but due to the lack of diagnostic material, this is questionable at best.
Megapaloelodus is an extinct genus of stem flamingo of the family Palaelodidae. Megapaloelodus is primarily known from Miocene America, from South Dakota and Oregon in the north to Argentina in the south, but the species Megapaloelodus goliath was found in Europe. Additionally, one unnamed species was discovered in Miocene sediments from Namibia. Due to a lack of skull material, little can be said about the ecology of Megapaloelodus. Species of this genus are typically larger than those of Palaelodus and appear to have inhabited similar brackish lake environments. Additionally, they may have been capable of "locking" their legs in a standing position.
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 unique development and a permanent covering of skin and fur.
Sinotherium is an extinct genus of single-horned elasmotheriine rhinocerotids that lived from the late Miocene to Early Pliocene. It was ancestral to Elasmotherium, demonstrating a very important evolutionary transition from nasal-horned elasmotheriines to frontal-horned elasmotheriines. Its fossils have been found in the Karabulak Formation of Kazakhstan, lower jaw and teeth have been found in Mongolia, and a partial skull is known from the upper part of the Liushu Formation of western China. Sinotherium diverged from the ancestral genus, Iranotherium, first found in Iran, during the early Pliocene. Some experts prefer to lump Sinotherium, and Iranotherium into Elasmotherium.
Osbornoceros is an extinct artiodactyl genus of the family Antilocapridae. All antilocaprid species are extinct except for the pronghorn. Osbornoceros osborni is the only known species of the genus Osbornoceros. Osbornoceros lived during the Late Miocene around 7 to 6 million years ago in what is now North America. It is well represented in fossil discoveries, with nearly a dozen specimens having been found to date. All come from the Chamita Formation in a quarry near Lyden, New Mexico, the site of numerous other finds such as that of Chamitataxus, a prehistoric badger that lived at the same time. The holotype specimen of Osbornoceros was discovered in 1937 and many more were found nearby during further expeditions.
Protoceratidae is an extinct family of herbivorous North American artiodactyls that lived during the Eocene through Pliocene. While early members of the group were hornless, in later members males developed elaborate cranial oramentation. They are variously allied with Ruminantia or Tylopoda.
Gazella praegaudryi was a small species of prehistoric gazelle described from late Miocene sediments near Bou Hanifia, Algeria. It had lightly compressed horn cores and no forward turning metaconid of its P4 premolars, differentiating it from the earlier Miocene Gazella dentition recovered at Fort Ternan.
Kipsigicerus is an extinct genus of East African antelope from the Middle Miocene. Its closest living relative is the four-horned-antelope.
Rhynchotherium is an extinct genus of proboscidea endemic to North America and Central America during the Miocene through Pliocene from 13.650 to 3.6 Ma, living for approximately 10 million years.
Ramoceros is an extinct genus of the artiodactyl family Antilocapridae endemic to Middle Miocene (Clarendonian) North America.
Scaphohippus is an extinct Miocene genus of equine, with two known species, known from fossils found in California, New Mexico, Montana, and Nebraska.
Lophocetus is an extinct genus of dolphin belonging to the clade Delphinida that is known from late Miocene (Tortonian) marine deposits in California and Maryland. Although usually placed in Kentriodontidae, recent studies have found it only distantly related to Kentriodon.
Capromeryx was a genus of dwarf pronghorns (Antilocapridae) that originated in North America during the Pliocene about 5 million years ago. The closest living relative and only surviving member of the family is the North American pronghorn.
Euprox is an extinct genus of deer that lived in Eurasia during the Miocene.
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