Xu Xing, Norell Mark A, Kuang Xuewen, Wang Xiaolin, Zhao Qi, Jia Chengkai
Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China.
Nature. 2004 Oct 7;431(7009):680-4. doi: 10.1038/nature02855.
Tyrannosauroids are one of the last and the most successful large-bodied predatory dinosaur groups, but their early history remains poorly understood. Here we report a new basal tyrannosauroid from the Early Cretaceous Yixian Formation of western Liaoning, China, which is small and gracile and has relatively long arms with three-fingered hands. The new taxon is the earliest known unquestionable tyrannosauroid found so far. It shows a mosaic of characters, including a derived cranial structure resembling that of derived tyrannosauroids and a primitive postcranial skeleton similar to basal coelurosaurians. One of the specimens also preserves a filamentous integumentary covering similar to that of other coelurosaurian theropods from western Liaoning. This provides the first direct fossil evidence that tyrannosauroids had protofeathers.
暴龙类是最后且最成功的大型掠食性恐龙群体之一，但其早期演化历史仍鲜为人知。在此，我们报道了一种来自中国辽宁西部早白垩世义县组的新的基础暴龙类，它体型小且纤细，具有相对较长的前肢和三指的手。这个新分类单元是迄今为止已知最早的无疑义的暴龙类。它呈现出一系列特征的混合，包括类似进步暴龙类的衍生颅骨结构和类似于基础虚骨龙类的原始颅后骨骼。其中一个标本还保存了丝状的体表覆盖物，类似于辽宁西部其他虚骨龙类兽脚亚目恐龙的体表覆盖物。这提供了首个直接的化石证据，表明暴龙类具有原始羽毛。
