| 翻訳と辞書 |
TNM 02067
TNM 02067 (Tanzanian National Museums specimen 02067) is a fragmentary fossil dentary (lower jaw) from the Cretaceous (between 146 and 66 million years ago) of Tanzania. The short, deep bone is about long, but the back part is broken off. It contains a large, forward-inclined incisor with a root that extends deep into the jaw, separated by a diastema (gap) from five cheekteeth. Very little remains of the teeth, but enough to determine that they are hypsodont (high-crowned). The third cheektooth is the largest and the roots of the teeth are curved. First described in 2003, TNM 02067 has been tentatively identified as a sudamericid—an extinct family of high-crowned gondwanathere mammals otherwise known from South America, Madagascar, India, and Antarctica. If truly a gondwanathere, it would be the only African member of the group and may be the oldest. The describers could not exclude other possibilities, such as that the jaw represents some mammalian group known only from younger, Cenozoic times (less than 66 million years ago).
==Discovery and context==
TNM 02067 was discovered in 2002〔Stevens et al., 2007, p. 167〕 in the locality TZ-07 in the Mbeya Region of southwestern Tanzania, which has also yielded remains of various other vertebrates, including birds and other saurischian dinosaurs. The discovery was reported in a 2003 paper by David Krause and colleagues. TZ-07 lies in the "Red Sandstone Unit" (RSU), an informal, poorly defined rock unit. Age estimates for the RSU have ranged from middle Jurassic to Miocene, but according to Krause and colleagues, part of this discrepancy is the result of confusion between two superficially similar rock units that outcrop nearby; the older one, where TZ-07 is located, is undoubtedly Mesozoic and the younger is Cenozoic.〔Krause et al., 2003, p. 322〕 Based on the presence of non-avian dinosaurs and osteoglossomorph fishes, Krause and colleagues assigned TZ-07 to the Cretaceous (146–66 million years ago).〔Krause et al., 2007, p. 323〕 In 2007, Nancy Stevens and colleagues identified the unit that produced TNM 02067 as likely belonging to the middle part of the Cretaceous (around Aptian to Cenomanian).〔Stevens et al., 2007, pp. 167–168〕 TNM 02067 is significant as one of the very few mammals from the Cretaceous of the southern continents (Gondwana).〔Krause et al., 2003, pp. 322–323〕
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「TNM 02067」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.
|
|