分类： 生物学 >> 动物学 提交时间： 2022-06-07 合作期刊: 《古脊椎动物学报》
摘要： Nothosaurus luopingensis n. sp. from Member II of the Guanling Formation (Anisian, Middle Triassic) of Luoping, Yunnan, China is described based on a specimen comprising the skull and most of the postcranial skeleton. The specimen is assigned to Nothosaurus of Eosauropterygia as suggested by a series of skull characters, such as the maxillary tooth row extending posteriorly beyond the level of the anterior margin of the upper temporal fenestra, the longitudinal diameter of the upper temporal fenestra is more than twice as long as that of the orbit, and the presence of maxillary fangs. Compared with Lariosaurus, the following morphological features of the pectoral girdle and the limbs also support the assignment of the specimen to Nothosaurus, i.e., the clavicles with expanded anterolateral corners, the characteristically curved humerus with a straight preaxial angle and a postaxial concavity, the distinct deltopectoral crest on the proximal part of the humerus, no hyperphalangy in the manus, and the absence of pachyostosis in the vertebrae and ribs. On the other hand, the specimen possesses some postcranial features that were previously considered to occur mainly in Lariosaurus, such as there being more than three ossifications in the carpus, having four sacral ribs, and an interclavicle without any trace of a posterior stem. These postcranial characters may no longer be used as the diagnostic features of Lariosaurus. N. luopingensis is distinguished from other Nothosaurus species by a unique combination of derived characters, including that the jugal enters the orbit, the nasals are separated, the posterior end of the frontal is bifurcate, pedal digits V and IV are long and subequal in length, and the ungula phalanx is stout. Our phylogenetic analysis reconfirms the monophyly of Nothosaurus and suggest that N. luopingensis is the sister group of N. yangjuanensis within the genus.
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： The transformation from a long reptilian tail to a shortened tail ending in a pygostyle and accompanied by aerodynamic fanning rectrices is one of the most remarkable adaptations of early avian evolution. However, no fossils directly capture this transition, and information regarding the structural morphology and the early evolution of the pygostyle in Mesozoic birds and their integuments is relatively limited. Here we provide a review of the pygostyle morphology of Early Cretaceous birds with comparison to the structure in living birds. This study emphasizes the convergent evolution of distally co-ossified caudal vertebrae in non-avian maniraptorans and early birds. There further exist distinct differences in pygostyle morphology between Sapeornithiformes, Confuciusornithiformes, Enantiornithes, and Ornithuromorpha. The morphology of the pygostyle and rectrices in early ornithuromorphs appear similar to that of extant birds, whereas the pygostyle in more primitive birds does not appear morphologically capable of supporting the rectricial bulbs and musculature necessary to control an aerodynamic fan-shaped tail. The rectricial bulbs and rectricial fan appear to have coevolved with the plough-shaped pygostyle early in the evolution of the Ornithuromorpha. This study also shows that the confuciusornithiform pygostyle was more similar to that of enantiornithines than previously recognized, consistent with the presence of nearly identical ornamental tail feathers in both groups.
分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-11
Yan, Liming
Wang, Wei
Rao, Zihe
Lou, Zhiyong
Sun, Sha
Shi, Juanming
Hu, Xiaoyu
Hu, Junjie
Sun, Sha
Shi, Juanming
Hu, Xiaoyu
Hu, Junjie
Rao, Zihe
Hu, Junjie
Wang, Wei
Wang, Shiyan
Su, Dan
Su, Dan
Rao, Zihe
Lou, Zhiyong
摘要： Homotypic membrane fusion of the endoplasmic reticulum is mediated by dynamin-like guanosine triphosphatases (GTPases), which include atlastin (ATL) in metazoans and Sey1p in yeast. In this paper, we determined the crystal structures of the cytosolic domain of Sey1p derived from Candida albicans. The structures reveal a stalk-like, helical bundle domain following the GTPase, which represents a previously unidentified configuration of the dynamin superfamily. This domain is significantly longer than that of ATL and critical for fusion. Sey1p forms a side-by-side dimer in complex with GMP-PNP or GDP/AlF4- but is monomeric with GDP. Surprisingly, Sey1p could mediate fusion without GTP hydrolysis, even though fusion was much more efficient with GTP. Sey1p was able to replace ATL in mammalian cells, and the punctate localization of Sey1p was dependent on its GTPase activity. Despite the common function of fusogenic GTPases, our results reveal unique features of Sey1p.
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