A paper from 2017 not yet mentioned. Unfortunately, the free pdf link does not seem to be working for this particular paper at the moment (zero content), although most of the other papers in the issue do work. I'll keep checking to see if the full pdf gets posted.
Microenantiornis vulgaris gen. et sp. nov.
WEI Zhao-ying & LI Li (2017)
Discovery of a new enantiornithine bird from Lower Cretaceous of western Liaoning, China.
Global Geology 36(3): 655-662 (Chinese edition)
For now, free fullÂ text preview at this link. Pages can be downloaded as images but pdf download seems to require login:
A new enantiornithine bird from Early Cretaceous Jiufotang Formation in Chaoyang of western Liaoning is described. This new small-sized bird shows several enantiornithine synapomorphies. Based on the morphological features of the hindlimb, this new specimen represents an arboreal enantiornithine bird. It has developmental forelimb and progressive coracoid, as well as lagging hindlimb and relatively primitive sternum morphology. The ratio of the length to the width of the sternum is approximately 1. Rostral margin of the sternum is rounded, the distal end of the outermost trabecula of the sternum is not expanded, and the distal end of the caudal trabecula is slightly expanded, with the keel of sternum absent. Its skeleton displays a mosaic of both primitive and derived characters, as well as the primitive sternum features. Its synthetic characters is distinguishable from other known small-sized enantiornithines, therefore this specimen represents a new genus and species: Microenantiornis vulgaris gen. et sp. nov.