Oxydactylus wyomingensis fossil camel (Harrison Formation, Lower Miocene; Platte County, Wyoming, USA) 1 : 無料・フリー素材/写真
Oxydactylus wyomingensis fossil camel (Harrison Formation, Lower Miocene; Platte County, Wyoming, USA) 1 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Oxydactylus wyomingensis (Loomis, 1936) - fossil camel skeleton from the Miocene of Wyoming, USA. (UW 215, University of Wyoming Geological Museum, Laramie, Wyoming, USA)This species is also known as Gentilicamelus wyomingensis. The skeleton may be a juvenile of Oxydactylus campestris.From museum signage:"Camels originated and evolved in North America. During the middle part of the Tertiary Period they were numerous and extremely diversified. Near the end of the Tertiary, about a million years ago. They migrated to South America and to the Old World where they survive today. In North America they became extinct before the arrival of man."-----------------"TylopodaCamels and their extinct relatives are members of the suborder Tylopoda. The Tylopoda are classified within the order Artiodactyla, the even-toed ungulates. The Artiodactyla are characterized by their astragalus (a bone in the ankle), which has the shape of a double pulley.Besides the Tylopoda, the Artiodactyla include three other suborders: the Suoidea (pigs, peccaries, hippopotamuses plus several extinct groups), the Cetacea (whales and dolphins), and the Ruminantia (cattle, sheep, bison, pronghorns, giraffes, African antelopes, deer, elk, and several extinct groups). In addition, three other groups of artiodactyls (Oreodontoidea, Mixtotheriidae, and Anoplotherioidea) cannot be comfortably classified within any of the four suborders.The suborder Tylopoda includes modern camels, llamas, alpacas, guanacos, and vicunas (family Camelidae) as well as three extinct families, Xiphodontidae, Oromerycidae, and Protoceratidae. The Protoceratidae are unique among the tylopods because cranial appendages evolved in males. The living tylopods consist of three genera and six species, a shadow of their former diversity.All living tylopods, classified in the Camelidae, are characterized by a long and thin neck, small head, slender muzzle with a cleft upper lip, contracted hindquarters, a three-chambered, ruminating esophagus-stomach complex, and oval rather than round red blood corpuscles. Among mammals, the last character is unique to the living Camelidae. It is not known if extinct tylopod species also possessed the soft anatomy characters seen in the living species.All tylopods, living and extinct, are herbivores. Living tylopods are grazers, subsisting on grasses. They are ruminating herbivores that chew cud. The extinct Xiphodontidae and Oromerycidae were small, primitive browsers with unspecialized dentitions and skeletons. Based on their brachydont (low-crowned) cheek teeth and retracted nasals suggesting a broad moose-like snout, the Protoceratidae may have been browsers on semiaquatic plants.Living tylopods inhabit semiarid to arid plains, deserts, and grasslands. The ability to survive on limited amounts of water is characteristic of living camels, but not of llamas. South American tylopods (llamas, alpacas, guanacos, and vicunas) are adapted to living at high altitudes.The Xiphodontidae and Oromerycidae probably inhabited forests, a habitat they shared with many other taxa of primitive ungulates. The morphology of the limbs of the Protoceratidae suggests that they were less cursorial and adapted more for bushy habitats rather than open plains.The camel (Camelus) and the llama (Lama) have a running gate called pacing. This is a swinging stride in which the front and hind legs on the same side of the body move together. Pacing is unlike the running gaits of other cursorial mammals, such as the trot of a horse, in which the front and hind legs on opposite diagonals move together. Pacing allows for efficient running using a long stride in open terrain. The pacing gait evolved first in middle Miocene camelids. Trackway evidence supports this suggestion. Selection for the pacing gait appears to coincide with the expansion of grassland habitats in North America.Extinct tylopods show a much wider range of morphology and adaptation than seen in living tylopods. Derived species of teh Protoceratidae evolved cranial appendages on the skull, a convergent character with deer, elk, bison, antelope, and cattle. The cranial appendages were sexually dimorphic. They were probably used for visual display and intraspecific combat. Other extinct tylopods, such as Megatylopus and Titanotylopus, tended toward extremely large size. Still others, such as Aepycamelinae evolved very long legs and necks and may have functioned, ecologically, as giraffe ecomorphs.Living tylopods are also important economically for humans. Their milk and meat is edible, their hair can be spun into thread and woven into cloth, and they can carry both people and goods."-----------------[referring to the skeleton seen here]"A Miocene camel from near Cheyenne, Wyoming.Geologic Range: 23 million years ago (Early Miocene).Geographic Range: High Plains of southeastern Wyoming.Adult Size: About 30 (76.2 cm) at the shoulder.Habitat and Diet: Floodplains. Herbivore (plant eater).Characteristics: This skeleton (UW 215) of Oxydactylus wyomingensis was collected from the lowermost Harrison Formation in Platte County, Wyoming in 1933 by University of Wyoming students J. D. Love and Arthur Peterson. Oxydactylus is characterized by a combination of an elongated neck and limbs in combination with a primitive dentition. Some experts suggest that Oxydactylus represents a grade of evolution rather than a real clade (group of close related species).Compared to Eotylopus reedi, Oxydactylus wyomingensis is larger, has more elongated limbs and neck, and upper incisors that look like canines. There is a missing tooth at the back end of the upper and lower jaws. The missing tooth is the third molar, which does not erupt until late in life, thus indicating that this specimen is juvenile."Classification: Animalia, Chordata, Vertebrata, Mammalia, Artiodactyla, Tylopoda, CamelidaeStratigraphy: lower Harrison Formation, Lower MioceneLocality: several miles southwest of the Harding Ranch on Bear Creek, Platte County, southeastern Wyoming, USA------------------See info. at:en.wikipedia.org/wiki/Oxydactylusanden.wikipedia.org/wiki/Camelid |
| 撮影日 | 2011-07-07 14:45:21 |
| 撮影者 | James St. John |
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