[1] The holotype specimen is remarkably complete for a Late Cretaceous enantiornithine, possessing a three dimensionally-preserved skull and partial skeleton.

Unlike most enantiornithines, the skull of Yuornis was completely toothless and convergently similar to that of neornithines (modern birds).

Unlike modern birds, the premaxilla makes up a smaller portion of the lower edge of the snout, while the quadratojugal is unusually large and complex.

[1] The phylogenetic analysis of Xu et al. (2021) positioned Yuornis as the sister taxon to Gobipteryx, another toothless Late Cretaceous enantiornithean.

However, the traits supporting this relationship were all related to tooth loss, a condition which is known to have convergently evolved many times in Mesozoic bird lineages.