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: A new crested theropod, Shuangbaisaurus anlongbaoensis gen. et sp. nov., is reported. The new taxon is recovered from the Lower Jurassic Fengjiahe Formation of Shuangbai County, Chuxiong Yi Autonomous Prefecture, Yunnan Province, and is represented by a partial cranium. Shuangbaisaurus is unique in possessing parasagittal crests along the orbital dorsal rims. It is also distinguishable from the other two lager-bodied parasagittal crested Early Jurassic theropods (Dilophosaurus and Sinosaurus) by a unique combination of features, such as higher than long premaxillary body, elevated ventral edge of the premaxilla, and small upper temporal fenestra. Comparative morphological study indicates that “Dilophosaurus” sinensis could potentially be assigned to Sinosaurus, but probably not to the type species. The discovery of Shuangbaisaurus will help elucidate the evolution of basal theropods, especially the role of various bony cranial ornamentations had played in the differentiation of early theropods.
分类: 生物学 >> 生物物理学 >> 基因表达调控与表观遗传学 提交时间: 2016-05-11
摘要: CD1, as the third family of antigen-presenting molecules, is previously only found in mammals and chickens, which suggests that the chicken and mammalian CD1 shared a common ancestral gene emerging at least 310 million years ago. Here, we describe CD1 genes in the green anole lizard and Crocodylia, demonstrating that CD1 is ubiquitous in mammals, birds, and reptiles. Although the reptilian CD1 protein structures are predicted to be similar to human CD1d and chicken CD1.1, CD1 isotypes are not found to be orthologous between mammals, birds, and reptiles according to phylogenetic analyses, suggesting an independent diversification of CD1 isotypes during the speciation of mammals, birds, and reptiles. In the green anole lizard, although the single CD1 locus and MHC I gene are located on the same chromosome, there is an approximately 10-Mb-long sequence in between, and interestingly, several genes flanking the CD1 locus belong to the MHC paralogous region on human chromosome 19. The CD1 genes in Crocodylia are located in two loci, respectively linked to the MHC region and MHC paralogous region (corresponding to the MHC paralogous region on chromosome 19). These results provide new insights for studying the origin and evolution of CD1.