| 翻訳と辞書 |
| Brachytrachelopan ： ウィキペディア英語版 |
Brachytrachelopan
''Brachytrachelopan'' is a short-necked sauropod dinosaur from the latest Jurassic Period (Tithonian) of Argentina. The holotype and only known specimen (Museo Paleontológico Egidio Feruglio MPEF-PV 1716) was collected from an erosional exposure of fluvial sandstone within the Cañadón Cálcero Formation on a hill approximately 25 km north-northeast of Cerro Cóndor, Chubut Province, in west-central Argentina, South America. Though very incomplete, the skeletal elements recovered were found in articulation and include eight cervical, twelve dorsal, and three sacral vertebrae, as well as proximal portions of the posterior cervical ribs and all the doral ribs, the distal end of the left femur, the proximal end of the left tibia, and the right ilium. Much of the specimen was probably lost to erosion many years before its discovery. The type species is ''Brachytrachelopan mesai''. The specific name honours Daniel Mesa, a local shepherd who discovered the specimen while searching for lost sheep. The genus name translates as "short-necked Pan", Pan being the god of the shepherds.
==Paleoecology and short neck==
This taxon's very short neck (approximately 40% shorter than other dicraeosaurids and the shortest of any known sauropod) is evidence that this lineage specialized to fill an ecological niche not exploited by other members of this infraorder. Small for a sauropod, ''Brachytrachelopan'' measured less than in length. Rauhut et al. (2005, 670) note that the high degree of fusion present between the preserved neural arches and their respective centra, as well as fusion between the sacral centra, sacral neural arches, and sacral neural spines is evidence that the holotype does not represent a juvenile animal. Hence, the small body size is not a relic of ontogeny.
Rauhut et al. (2005, 671-672) note that the tendency towards shorter-necks seen in dicraeosaurids, and most evident in ''Brachytrachelopan'', runs counter to the lengthening of the neck seen in most sauropod lineages (brachiosaurids, titanosaurs, diplodocids, etc.) and indicates that this group of sauropods was "progressively adapting for low browsing and might have been specialized on specific food sources, as has been suggested for ''Amargasaurus'' and ''Dicraeosaurus''." Moreover, the morphology of the cervical neural arches in ''Brachytrachelopan'' would have significantly restricted dorsal flexion of neck and most likely indicates that this sauropod was specialized to a diet of plants "growing at heights of between about 1 and 2 m." Rauhut et al. (2005, 672) also suggest that diet may have been a limiting factor in body size among dicraeosaurids, and that this may have placed them in the same ecological niche as "large low-browsing iguanodontian ornithopods." Such large iguanodontians are absent from the Late Jurassic Gondwanan sediments that have produced all known fossils of dicraeosaurids, while they are abundant in similar ecosystems of the same age in North America, where dicraeosaurids are absent. This may indicate that large iguanodontians and dicraeosaurids (especially ''Brachytrachelopan'') were ecological analogs, resulting from parallel evolution in two distantly related dinosaurian lineages.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Brachytrachelopan」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|