近完整的瑟莫波利斯始祖鸟标本（后编号 WDC CSG 100）保存可过伸第二趾、四射型腭骨以及不同于完全反转栖枝趾的拇趾；这种解剖镶嵌支持兽脚类亲缘，却不证明直系祖先或唯一“第一只鸟”。
claim:event:archaeopteryx-thermopolis-skeletonA well-preserved Archaeopteryx specimen with theropod features
Mayr, G.; Pohl, B.; Peters, D.S.
年份2005
来源角色primary-study
DOI / ID10.1126/science.1120331
适用范围
形态 · 拓扑
The Thermopolis specimen, later catalogued WDC CSG 100, documents an anatomical mosaic; it does not by itself establish direct ancestry or a unique first bird.