鸟类和爬行动物,统称为sauropsids,可以在系统发育上细分为恐龙(鸟类,鳄鱼),Testistines(海龟),鳞片(蜥蜴,蛇)和rhynchocephalia(tuatara)。表皮附属物的结构框架,其中包括羽毛,爪子和鳞片,以前用电子显微镜来表征,红外光谱和X射线衍射分析,以及通过对组成β-角蛋白(也称为角膜β-蛋白)的氨基酸序列的研究。这项工作的一个重要遗漏,然而,是缺乏与棘突(tuatara)的表皮附属物有关的序列和结构数据,鳞龙的两个分支之一。对tuatara基因组进行测序已经付出了相当大的努力,虽然这还没有完成,现在有足够的序列数据可以得出结论,可以得出tuatara中β-角蛋白与sauropsids其他成员的相似性。这些结果,并比较了tuatara爪与海鸥羽毛和Goanna爪的X射线衍射图,确认所有树体的β-角蛋白都有一个共同的结构计划,不仅仅是那些包括恐龙(鸟类和鳄鱼)的人,testistines(海龟)和鳞片(蜥蜴和蛇)。
The birds and reptiles, collectively known as the sauropsids, can be subdivided phylogenetically into the archosaurs (birds, crocodiles), the testudines (turtles), the squamates (lizards, snakes) and the
rhynchocephalia (tuatara). The structural framework of the epidermal appendages from the sauropsids, which include feathers, claws and scales, has previously been characterised by electron microscopy, infrared spectroscopy and X-ray diffraction analyses, as well as by studies of the amino acid sequences of the constituent β-keratin proteins (also referred to as the corneous β-proteins). An important omission in this work, however, was the lack of sequence and structural data relating to the epidermal appendages of the
rhynchocephalia (tuatara), one of the two branches of the lepidosaurs. Considerable effort has gone into sequencing the tuatara genome and while this is not yet complete, there are now sufficient sequence data for conclusions to be drawn on the similarity of the β-keratins from the tuatara to those of other members of the sauropsids. These results, together with a comparison of the X-ray diffraction pattern of tuatara claw with those from seagull feather and goanna claw, confirm that there is a common structural plan in the β-keratins of all of the sauropsids, and not just those that comprise the archosaurs (birds and crocodiles), the testudines (turtles) and the squamates (lizards and snakes).