A new species of Yanornis (Aves: Ornithurae) from the Lower Cretaceous strata of Yixian, Liaoning Province

A nearly complete specimen of Yanornis was recently discovered from the Early Cretaceous Yixian Formation at Yixian, Jinzhou City, Liaoning Province. This specimen shows typical characteristics of Yanornis, such as the straight dentary, about 2/3 the length of skull, with about 20 teeth on each side. The cervicals are long and heterocoelous. The synsacrum is composed of 9 sacrals. The length ratio of forelimb to hindlimb is about 1.1. The proximal pedal phalanges are longer and more robust than the distal ones. However, the new specimen is different from the type species-Yanornis martini, by having the following unique characteristics: the humerus has a large and strong deltoid crest, which is almost half the length of the shaft. The pubic symphysis is short, with the same length as the pygostyle, and is less than 1/6 the length of the pubis. The fibular is long, about 4/5 the length of femur and 2/3 the length of the tibiotarsus. The tarsometatarsus is short and completely fused, less than half the length of the tibiotarsus. This specimen can be erected as a new species of Yanornis-Yanornis guozhangi sp. nov., on the basis of its unique characteristics and a comparison with Yixianornis grabaui, Songlingornis linghensis and Yanornis martini. It is notable that three fish fossils were preserved along the neck of Yanornis guozhangi sp. nov., which provides important information for studying the living habit and growth pattern of Yanornis.