A beaked basal ornithurine bird (Aves, Ornithurae) from the Lower Cretaceous of China

We report here one of the earliest known beaked ornithurine birds from the Lower Cretaceous deposits in Liaoning, northeast China. The new basal ornithurine, Archaeorhynchus spathula gen. et sp. nov., has a rhynchokinetic skull with toothless jaws. It also contains over three dozen preserved gizzard stones, suggesting an herbivorous diet. The distal end of the tibiotarsus is unfused, enabling recognition of the astragalus with a broad ascending process, generally similar to that of Archaeopteryx. The new discovery sheds new light on our understanding of the early radiation and diet diversification of early birds in the Lower Cretaceous.