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Bolong (Ornithopoda) juvenile from Lower Cretaceous of China.

From: Ben Creisler

A new online paper:

Wenjie Zheng, Xingsheng Jin, Masateru Shibata & Yoichi Azuma (2013)
An early juvenile specimen of Bolong yixianensis (Ornithopoda:
Iguanodontia) from the Lower Cretaceous of Ningcheng County, Nei
Mongol, China.
Historical Biology (advance online publication)

We describe an early juvenile specimen (ZMNH M8812) of Bolong
yixianensis from the Yixian Formation (Lower Cretaceous) of Ningcheng
County, Nei Mongol, China. The specimen consists of an almost complete
skeleton preserved two-dimensionally on a slab. The short and deep
skull proportions and unfused neurocentral sutures in most preserved
vertebrae suggest that the ZMNH M8812 is a juvenile individual.
Osteohistological study confirms a very early developmental stage. The
study reveals the ontogenetic changes of Bolong for the first time.
The specimen revealed one additional autapomorphy for Bolong
yixianensis: the lingual face of the maxillary crown is bounded by
thickened mesial and distal margins and bisected by a prominent median
principal ridge. The study revealed the following ontogenetic trends
of Bolong: increased tooth rows in both maxilla and dentary, increased
robustness of the jugal and scapula, the radius and ulna become more
robust and shorter relative to the hindlimb and the metatarsals become
proportionally shorter. ZMNH M8812 represents the first juvenile
non-hadrosaurid iguanodontian specimen described from the Lower
Cretaceous of eastern Asia.