【作者】 姬书安；

【导师】 郝诒纯； 季强；

【作者基本信息】 中国地质大学（北京） ， 古生物学与地层学， 2003， 博士

【摘要】 近几年来，中国辽宁西部热河生物群研究取得了许多重大进展，尤其是一系列长有羽毛(皮肤衍生物)兽脚类恐龙化石的发现，为鸟类的兽脚类恐龙起源假说及鸟类飞行的陆地奔跑起源假说提供了极为重要的化石依据。但鸟类与哪一支兽脚类恐龙类群的系统关系最为接近、羽毛本身的起源及其早期演化如何、鸟类如何定义等问题，仍然没有得到彻底解决。2000年，辽西朝阳市上河首早白垩世九佛堂组地层中，发现了一件保存完好的长有羽毛的奔龙类化石，这是继北票四合屯、朝阳下三家子、凌源大王杖子之后长羽毛奔龙化石在辽西的又一次发现，为解决奔龙类的系统关系、羽毛的起源及早期演化提供了重要的实物资料。这件奔龙类标本(NGMC 00-12-A)保存极为完整，全长(头骨吻端至尾巴末端)约1m，是一个体较小的奔龙类。它具有许多中国鸟龙属Sinornithosaurus所特有的特征，如：齿骨后部分叉、前颌骨齿齿冠前后缘均无小锯齿、叉骨U形、第Ⅱ指第2指节很短、坐骨封闭突极大且具有坐骨后背突、第Ⅲ蹠骨部分窄足型等，因而无疑应归入该属中。然而这一标本个体较小，其前肢一些骨骼的长短比例与中国鸟龙属属型种Sinornithosaurus millenii相比存在一定差异，同时新标本头骨后部保存不好而不能提供更多信息，故暂将其作为中国鸟龙属未定种Sinornithosaurus sp．处理。这一标本不仅骨骼较为完整，而且还保存有大面积的羽毛，尤其是其前肢羽毛及尾部中后部的羽毛已经具有了较为发育的羽轴(羽干)及平行的羽枝，从而以确凿的证据表明奔龙类的羽毛也具备了现代羽毛的基本特征。 奔龙类是一类较为特殊的手盗龙类(Maniraptora)，它具有许多与始祖鸟Archaeopteryx甚至其它早期鸟类相似或接近的特征，主要表现在：叉骨U形与始祖鸟和孔子鸟类的相同，背肋钩状突在孔子鸟类和个别反鸟类中也存在，肩臼窝绝大部分指向侧方类似于始祖鸟，肩胛骨与乌喙骨间的夹角非常接近90°也和始祖鸟的相似，前肢从比例上讲显得较长，大的半月形腕骨使肘部能向侧方折过来，耻骨伸向后下方，距骨上升突与原始鸟类中的为同源结构，羽毛已有显著的分化且具备了现代羽毛的基本结构等等。这些特征表明：在进步的手盗龙类向鸟类演化的过程中，不仅许多特征在奔龙类阶段就已经完成或正在转变，而且羽毛与骨骼间亦存在着一定程度的协同演化现象。 奔龙类自成一科，即奔龙科(Dromaeosauridae)，它又可进一步分为奔龙亚科(Dromaeosaurinae)与疾走龙亚科(Velociraptorinae)。该科化石主要分布于东亚及北美的白垩纪地层中，此外在欧洲、非洲、南美等地也有零星发现，这类化石在研究兽脚类与鸟类的系统关系方面具有特殊重要的价值。迄今较为重要的属主要有北美的Dromaeosaurus、Deinonvchus、Saurornitholestes、Utahraptor、Bambiraptor以及东亚的Velociraptor、Achillobator、Adasaurus、Sinornithosaurus、Microraptor等，这些属之间的分支系统关系至今仍未解决。目前关于奔龙类在手盗龙类中的系统位置有几种不同的观点，本文支持奔龙类与Avialae的关系最为密切的观点，即奔龙类是与Avialae最为亲近的类群，两者构成姐妹群关系。本文给出的奔龙类系统关系图还显示：伤齿龙类poodonhdae）和窃蛋龙类（aptotidae也应该发育了具有羽干及羽片的羽毛结构，而且羽毛已不再是鸟类所特有的特征，它早在鸟类及其飞行产生之前就己经存在并且有相当程度的分化。 到目前为止，辽西热河生物群中己有几个不同的兽脚类恐龙类型被发现长有羽毛，它们是美颌龙类的site…ropteny、原始祖鸟类的w／arce。opterm、尾羽鸟类（窃蛋龙类）的CaH却作沙、镰刀龙类的＊一加0——一奔龙类的S初00掀…一及Mlerraptor等。此外，发现于蒙古的Athere罚a。dae科的h。…亦被证实具有原始羽毛。其中S切OJMropteny、＊一加0…、孙。…具有最为简单的原始羽毛状构造，这种构造不具备羽干及羽小枝；而 Proto17vaeoptepe、Ca。dhtepe。厂初ornMOJau。不仅发育有原始羽毛，同时还发育了具有羽干及羽小校的现代羽毛结构。这些化石揭示了原始羽毛的特征，它们在研究原始羽毛的定义、羽毛的起源及其早期演化模式等方面具有极为重要的意义。本文首次明确给出了原始羽毛卜otofeath一的定义：原始羽毛是指在羽毛（广义）发生演化的初期阶段，那些不具有显著分化的羽干或不具有羽轴、同时不具有羽小校的结构简单的羽毛类型。同时，本文还首次将原始羽毛分为3种不同的类型：丝状原始羽毛（if删cut－like protofeather）、雏绒羽状原始羽毛…atal－d皿n－ike pro由feather）、分枝状原始羽毛…ranch－like protofeather）。存在于C她却te叭、Jco。itbo。。等前肢上对称状的飞羽己具有了现代羽毛的典型结构，但作为飞羽来讲它则代表了一种较原始的结构。 关于羽毛的早期演化模式主要有两种看法，第一种认为羽毛的演化按鳞片拉长、羽校出现、羽轴（羽干）出现、羽小枝羽小钩出现的顺序进行，第二种观点认为羽毛的演化经历了鳞片拉长、羽轴出现、羽枝分化、羽小枝羽小钩出现这一系列的变化，这两种看法最主要的差别在于羽校与羽轴更多还原

【Abstract】 Recently, a series of the feathered dinosaurs have been found from the Jehol Biota of western Liaoning, Northeast China, which give extremely strong evidences of the theropod hypothesis of bird origin and of the cursorial hypothesis of the avian flight origin. But the origin and early evolution of feathers have still been unanswered. In late 2000, a well-preserved specimen of dromaeosaurids was excavated from the Early Cretaceous Jiufotang Formation of Shangheshou, suburb of Chaoyang City, western Liaoning. This new specimen (NGMC 00-12-A) is preserved not only by almost complete skeleton but also by many feathers. It is a quite small dromaeosaurid with the total length nearly 1 meter from the snout to the tip of the tail. It shows many typical characters seen in the type species of the genus of Sinornithosaurus, which discovered also from western Liaoning. NGMC 00-12-A can further be included in Sinornithosaurus by the dentary bifurcated posteriorly, unserrated premaxillary teeth, U-shaped furcula, extremely short manual phalanx III-2 in comparison with the length of phalanx III-l, very large and developed obturator process of the ischium, partially arctometatarsalian metatarsal III and so on. This specimen slightly differs from the type species of the same genus Sinornithosaurus milknii in the length proportions of some manual elements. Because its cranial posterior portion is badly preserved and difficult to be compared with the type species, it is temporarily identified as Sinornithosaurus sp. here. The feathers attached to the arms and the tail evidently possess the structures of "modern feathers", which consisting of the central shafts (rachis) and parallel barbs.Dromaeosaurids are unusual group of maniraptoran theropods. They share many similar or the same features with Archaeopteryx or other primitive birds, such as: U-shaped furcula, uncinate process, laterally facing glenoid of shoulder girdle, comparatively long forelimb, large semilunate carple, retroverted pubis, ascending process of astragalus, and "modern feathers" with rachis and barbs etc. These facts indicate not only that dromaeosaurids had developed many bird-like characters in course of the advanced maniraptorans toward birds, but also that there seemed to be the co-evolutionary trend between the feathers and the skeletal bones.Dromaeosaruid theropods can be restricted in the unique family Dromaeosauridae; furthermore, this family may also be subdivided into two subfamilies Dromaeosauridae and Velociraptorinae. About a dozen genera are referred to this group, most of which were collected from the Cretaceous beds including the North American Dromaeosaurus, Deinonychus, Saurornitholestes, Bambiraptor, Utahraptor, and the East Asian Velociraptor, Adasaurus, AchiUobator, Sinornithosaurus, Microraptor as well. But the interrelationships among these genera remain uncertain until now. A great quantity of features recognized in dromaeosaurids supports the view that Dromaeosauridae is the sister group of Avialae. The cladogram proposed in the present paper also suggests that the maniraptoran Troodontidae and Ovkaptoridae should have the branched feathers, and that feathersevolve and initially diversify in terrestrial theropod dinosaurs before the origin of birds and their flight.Up to now, several feathered theropods from western Liaoning have been uncovered, and one kind of another Mongolian theropod has also been proved to possess protofeathers. Sinosauropteryx (compsognathids), Beipzaosaums (therizinosaurids) and Shuvuuia (alvarezsaurids) have the filament-like protofeathers that lack the rachis and barbules. But in Protarchaeopteryx (protarchaeopterygians), Caudipteryx (caudipterygians or oviraptorosaurs) and Sinornithosaurus (dromaeosaurids), not only protofeathers but also the "modern feathers" that have evident rachis and barbules can be observed. These fossils are very important in the study of the definition of protofeathers and in the study of the origin and early evolution of feathers. In the present paper, protofeathers is更多还原