sentences:  Because the species was named for a hatchling specimen, it cannot be matched with adult specimens, and so it is impossible to determine which, if any, birds from the same rocks represent adults of this species.Luis Chiappe and colleagues therefore regarded it as a "nomen vanum" ("empty name") or at least a "nomen dubium", and recommended that use of the name be abandoned.In 1999, Hou and Chen of the Nanjing Institute of Paleontology and Geology briefly described a specimen of very small bird obtained by the museum and named it "Liaoxiornis delicatus".