Liaoningosaurus

Liaoningosaurus is a very unusual ankylosaur from the Lower Cretaceous. The holotype (IVPP V12560; Institute of Vertebrate Paleontology and Paleoanthropology, Beijing), an essentially complete juvenile skeleton, was collected from the Yixian Formation (Aptian) of Liaoxi, Yixian County, Liaoning Province, People's Republic of China.

The articulated skeleton measures approximately 34 cm in length, giving it the distinction of being the smallest-known ankylosaur. This taxon is unique among all known ankylosaurs in the retention of the external mandibular fenestra. Antorbital fenestrae may also be present.

Another unique feature is the presence of ventral armor plating, sculpted hexagonal and rhombic osteoderms, unknown in other ankylosaurians. Xu et al. (2001) place Liaoningosaurus within the Nodosauridae, while Vickaryous et al. (2004) have provisionally assigned it to the Ankylosauria incertae sedis.