Microhadrosaurus

Dong, Zhiming, 1979, Dinosaurs from the Cretaceous of South China, Mesozoic and Cenozoic Red Beds of South China: Selected Papers from the " Cretaceous-Tertiary Workshop ", Institute of Vertebrate Paleontology and Paleoanthropology & Nanjing Institute of Paleontology, Nanxiong, China: Science Press, pp. 342-350 : 5

Microhadrosaurus nanshiungensis gen. et sp. nov.

(Plate I, Figures 4 and 5)

Diagnosis: A rather small hadrosaur with a linear mandible, densely packed and planar dentition with vertical alveolae, and tooth count that does not exceed 45. The coronoid process is perpendicular to the mandible.

Material: A 13.2 cm long midsection of a left mandible collected by the Guangdong Provincial Regional Survey. IVPP specimen #V4732 .

Description: The specimen is principally represented by a posterior dentary with linear dorsal and ventral margins, its lateral midsection is inflated, dorsal margin is thin, medioventral margin is thick, and the Meckelian groove penetrates anteriorly and gradually attenuates. The medial side is flatter than the general hadrosaurian condition, the dentition is densely packed, 19 perpendicular and parallel aligned dental rows are preserved, and the apex of the coronoid process is slightly expanded into a shovel-shape.

Comparison and discussion: It is appropriate to assign the specimen to the subfamily Hadrosaurinae based upon the flat and straight mandible and relatively low dentary, indicating that the mandible is rather narrow and thus, the cranium is correspondingly elongated. This is a relatively small individual, being probably only three meters in length, and representing the smallest species of hadrosaur known. It resembles the North American Hadrosaurus and Canadian Anatosaurus in its planar dentition and relatively densely packed tooth grooves, however the former are much larger. Despite there being only a single mandible, it is sufficient to recognize that it represents a new taxon and is thus erected as Microhadrosaurus nanshiungensis gen. et sp. nov.

Figures

Figure 4. Pelvic girdle of Nanshiungosaurus brevispinus (x 1 / 10)