Genus: Liaoningosaurus Xu, Wang, & You, 2001

Classification: Dinosauria - Ornithischia - Thyreophora - Ankylosauria - Nodosauridae

Etymology: Generic name refers to Liaoning Province.

Synonyms: none

Type species: L. paradoxus Xu, Wang, & You, 2001

Other Species: none

Diagnosis: as for type species

Species: Liaoningosaurus paradoxus Xu, Wang, & You, 2001

Etymology: specific name refers to the surprising characteristics of this animal.

Synonyms: none

Holotype: IVPP V12560, a nearly complete skeleton.

Referred Specimens: none

Time: Lower Cretaceous.

Horizon: Yixian Formation.

Location: WangJiagou, Yixian, Liaoning Province, China.

Total length: 34 cm (juvenile individual), 2-3 m (adult individual).

Mass: ?

Diagnosis: An ankylosaurian that differs in having: shell-like ventral armour, trapezoidal sternum with slender and distally pointed posterolateral process and short medial articular margin, and pes more than twice as long as manus (Xu, Wang, & You, 2001).

Comments: Juvenile ankylosaur specimens are very rare. Liaoningosaurus paradoxus based on a beautifully preserved juvenile ankylosaur specimen from the famous Yixian Formation of Liaoning, China. Liaoningosaurus has a large bony plate (somewhat shell-like) shielding the abdomen. This discovery represents the first record of such a structure among dinosaurs. Although it has a number of distinct
features seen in the family Ankylosauridae, a cladistic analysis placed Liaoningosaurus in the sister-family Nodosauridae. The ‘intermediate’ status of this taxon between the two ankylosaur families further supports the monophyly of Ankylosauria. This finding also documents the smallest known ankylosaur specimen and first complete nodosaurid specimen from Asia (Xu, Wang, & You, 2001).

IVPP V12560 represents a juvenile individual, as indicated by the unfused centra and neural arches of vertebrae. It is less than 34 cm in length and represents the smallest ankylosaur specimen reported to
date (Xu, Wang, & You, 2001).

Liaoningosaurus is unique among ankylosaurs in displaying a large, ventral abdominal plate. Ankylosaurs show evidence of some ventral dermal armour; however, this is, in all other known examples
(such as Minmi), restricted to small unfused elements that do not form a large plate or shield-like structure (Xu, Wang, & You, 2001).

Illustrations:
Liaoningosaurus paradoxus (IVPP V12560, holotype). a photograph, b line-drawing of the holotype. Abbreviations: cu clawlike ungual, ftr fourth trochanter, la left astragalus, lc left calcanium, lf left fibula, lh left humerus, lic left ischium, lil left ilium, lm left manus, lr left radius, ls left sternum, lt left tibia, ltr lesser trochanter, lu left ulna, lvp large ventral plate, m maxilla, md mandible, pl plate, pm premaxilla, pmt premaxillary teeth, q quadrate, rp right pes, rs right scapula, vp vertical plate. Scalenbar = 4 cm (modified from Xu, Wang, & You, 2001).

Liaoningosaurus paradoxus classification (modified from Xu, Wang, & You, 2001).

References:
Xu X., Wang X., & You H., 2001. A juvenile ankylosaur from China . Naturwissenschaften, 88: 297-300.

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