Sinornithosaurus millenii Xu, Wang & Wu, 1999 (feathery dromaeosaurid)

[Dinogeorge@aol.com]

The following article will appear in tomorrow's issue of Nature:

Nature 401, 262 - 266 (1999) © Macmillan Publishers Ltd. 

A dromaeosaurid dinosaur with a filamentous integument from the Yixian 
Formation of China

XING XU, XIAO-LIN WANG & XIAO-CHUN WU

Dromaeosaurids, despite their notoriety, are poorly characterized 
meat-eating dinosaurs, and were previously known only from 
disarticulated or fragmentary specimens. Many studies have denied their 
close relationship to birds. Here we report the best represented and 
probably the earliest dromaeosaurid yet discovered, Sinornithosaurus 
millenii gen. et sp. nov., from Sihetun, the famous Mesozoic 
fish-dinosaur-bird locality in China. Sinornithosaurus not only greatly 
increases our knowledge of Dromaeosauridae but also provides evidence 
for a filamentous integument in this group. It is remarkably similar to 
early birds postcranially. The shoulder girdle shows that terrestrial 
dromaeosaurids had attained the prerequisites for powered, flapping 
flight, supporting the idea that bird flight originated from the ground 
up. The discovery of Sinornithosaurus widens the distribution of 
integumentary filaments among non-avian theropods. Phylogenetic analysis 
indicates that, among known theropods with integumentary filaments or 
feathers, Dromaeosauridae is the most bird-like, and is more closely 
related to birds than is Troodontidae.