Mirusavis is a genus of Enantiornithes from the early Cretaceous (Aptian – Barremian) of China recovered in the Yixian Formation. It contains a single species, Mirusavis parvus.
The genus name Mirusavis comes from the Latin words Latin: mirus (unexpected) and words Latin: avis (bird), in reference to the unusual discovery of the holotype preserved during the laying cycle. The species name words Latin: parvus means "small" in Latin.
Wang et al. (2020) recovered Mirusavis to be closest related to Shangyang graciles.
The type and only specimen of Mirusavis was a partial subadult skeleton identified by the lack of ossification that would be seen in a mature individual. Medullary bone tissue was also recovered in the specimen, meaning that the fossil was a female that died during the egg-laying cycle. This find shows that Enantiornithes were unlike modern day birds in that they became reproductively active before completing the ossification of their skeleton.[1]