Yanoconodon

The Qiaotou Member may correlate with the more well-known Early Cretaceous Yixian Formation, and so probably dates to around 122 Ma ago.

[1] Yanoconodon was a eutriconodont, a group composing most taxa once classified as "triconodonts" which lived during the time of the dinosaurs.

These were a highly ecologically diverse group, including large sized taxa such as Repenomamus that were able to eat small dinosaurs,[2] the arboreal Jeholodens, the aerial volaticotherines and the spined Spinolestes.

[7] The closely related eutriconodont Jeholodens lacks these lumbar ribs, and it has been suggested that this morphological difference is due to changes in the Hox genes, specifically in the Hox10 group.

These are of particular interest because of their "transitional" state: Yanoconodon has fundamentally modern middle ear bones, but these are still attached to the jaw by an ossified Meckel's cartilage.