Cruralispennia

Cruralispennia is an extinct genus of enantiornithean bird. The only known specimen of Cruralispennia was discovered in the Early Cretaceous Huajiying Formation of China and formally described in 2017. The type species of Cruralispennia is Cruralispennia multidonta. The generic name is Latin for "shin feather", while the specific name means "many-toothed". The holotype of Cruralispennia is IVPP 21711, a semi-articulated partial skeleton surrounded by the remains of carbonized feathers.

Cruralispennia lived alongside several other species of enantiornitheans, such as Protopteryx, in the Sichakou Basin of the Huajiying Formation, approximately 130.7 million years ago. Despite being one of the earliest known ornithothoraces, this genus possessed several features of derived enantiornitheans as well as some unusual traits convergent with ornithuromorphs, a group containing modern birds. Cruralispennia is also notable for having crural feathers originally described as possessing a unique form unknown in any other feathered animal. However, it has also been hypothesized that the holotype specimen had recently molted, and that the unusual feathers were simply new feathers which had yet to lose the thick sheath around the rachis.