Temporal range: Late Jurassic, 160Ma
Xu et al., 2011
|Species:||† X. zhengi|
Xu et al., 2011
Xiaotingia is known from the holotype STM 27-2, an articulated and almost complete skeleton including the skull. It was probably collected in the Linglongta area, Jianchang, from the Tiaojishan Formation.
The initial analysis by Xu et al. showed that Xiaotingia formed a clade with Archaeopteryx, Dromaeosauridae and Troodontidae to the exclusion of other groups traditionally seen as birds. Xu et al therefore (re)defined the concepts of Deinonychosauria and Avialae to the extent that Archaeopteryx and Xiaotingia belonged to the Deinonychosauria in the clade Archaeopterygidae. This led to popular reports that "Archaeopteryx is no longer a bird", although Xu et al noted that there are several competing definitions of the clade Aves currently in use, pointing out that their definitions are compatible with a traditional Aves with Archaeopteryx as a specifier. This was challenged by an analysis using different methods published several months later however, in which Archaeopteryx was again recovered as an avialan, while Xiaotingia remained closely allied to Anchiornis within the Troodontidae. In 2012, an expanded and revised version of the initial analysis also found Archaeopteryx to be avialan and Anchiornis to be troodontid, but recovered Xiaotingia as the most primitive member of the clade Dromaeosauridae rather than a close relative of Anchiornis within Troodontidae.
Relationships found by the revised analysis of Senter et al., 2012:
Relationships found by the initial analysis of Xu et al., 2011:
- Xing Xu, Hailu You, Kai Du and Fenglu Han (28 July 2011). "An Archaeopteryx-like theropod from China and the origin of Avialae". Nature 475 (7357): 465–470. doi:10.1038/nature10288. PMID 21796204.
- "Feathers fly in first bird debate". BBC News. 27 July 2011.
- Lee, M.S.Y. and Worthy, T.H. (2011). "Likelihood reinstates Archaeopteryx as a primitive bird. Biology Letters, published online before print October 26, 2011, doi:10.1098/rsbl.2011.0884
- Senter, P., Kirkland, J.I., DeBlieux, D.D., Madsen, S., and Toth, N. (2012). "New Dromaeosaurids (Dinosauria: Theropoda) from the Lower Cretaceous of Utah, and the Evolution of the Dromaeosaurid Tail." PLoS ONE, 7(5) e36790. doi:10.1371/journal.pone.0036790 PMID 22615813