辽西热河生物群中国龟科一新材料研究

发布时间：2018-04-14 03:07

本文选题：早白垩世 + 中国龟科　；参考：《沈阳师范大学》2017年硕士论文

【摘要】：热河生物群中的龟类化石大多属于曲颈龟类一个原始类群——中国龟科,它们以背甲低平、背腹甲韧带联接等为特征,并以辽西地区的满洲满洲龟(Manchurochelys manchoukuoensis EndoShikama,1942)、辽西鄂尔多斯龟(Ordosemys liaoxiensis Ji,1995)、建昌辽龟(Liaochelys jianchangensis Zhou,2010)和内蒙古地区的宁城小龟(Xiaochelys ningchengensis ZhouRabi,2015)等为代表。本文研究了一件产自辽宁凌源四合当刘李沟早白垩世九佛堂组地层的中国龟科化石。该化石的鼻骨缺失;前额骨相互联接;眼眶间区窄;顶骨与鳞骨分离;上枕骨嵴比鳞骨嵴长;背甲低平近椭圆形,长大于宽;两个上臀板大小相当;后肢趾式为2-3-3-3-4。尽管这一特征组合不同于其它属种,但是由于该标本为一未成年个体且存在发育畸形现象,故此暂将其做为中国龟科中的一个未定属种。此外,新标本的趾式出现多趾现象;该情况也发生在现生的一些水生龟类,比如鳖类;表明了其对水生生活的一个形态适应。再有,新标本还发育了椎盾畸形的现象:椎盾比正常的5块多出了2块。在标本周围还保存有粪便化石。不过,在粪便化石中并未发现有明显的骨骼或者鳞片,暗示其可能已具有了与现生水生龟类相似的强消化能力。这些发现表明在中生代时期原始隐颈龟类已具有了与现生龟类相似的对水生习性的形态适应,以及发育畸形和消化生理机制等古生态学特征。
[Abstract]:Most of the turtle fossils in the Gehe biota belong to a primitive group of Tortoise, the Chinese tortoise family. They are characterized by low flat back armour and ligamentum dorsalis, etc.It is also represented by Manchurochelys manchoukuoensis Endo Shikamaa (1942), Ordosemys liaoxiensis liaoxiensis (1995), Liaochelys jianchangensis (2010) in western Liaoning and Xiaochelys ningchengensis Zhou Rabi (2015) in Ningcheng, Inner Mongolia.In this paper, a fossil of the Chinese tortoise family from the early Cretaceous Jiu Futang formation of Sihe Ligou, Lingyuan, Liaoning Province, has been studied.The fossil's nasal bone is missing; the prefrontal bone is connected to each other; the interorbital area is narrow; the parietal bone is separated from the squamous bone; the upper occipital ridge is longer than the squamous ridge; the dorsal nail is low near ellipse and grows wider; the two superior gluteal plates are of the same size; the hind toe is 2-3-3-3-4.Although this characteristic combination is different from other genera and species, because the specimen is a minor individual and has developmental malformation, it is temporarily regarded as an undetermined genus in the family Turtle of China.In addition, the phenomenon of polydactyly in the new specimen is also found in some present aquatic turtles, such as turtle, which indicates a morphological adaptation to aquatic life.In addition, the new specimen also developed the phenomenon of deformity of vertebra shield: two more than normal 5.Fossils of feces are also preserved around the specimens.However, no significant bone or scales were found in the faecal fossils, suggesting that they may already have strong digestibility similar to that of the present aquatic tortoises.These findings indicate that the primitive cryptophoric tortoises had the characteristics of paleoecology, such as morphological adaptation to aquatic habits, developmental deformities and digestive physiological mechanisms similar to that of present tortoises in the Mesozoic period.
【学位授予单位】：沈阳师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q915

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