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Psittacosaurus comparative juvenile histology

Ben Creisler

A new paper:

Shen Caizhi and Peter Dodson (2016)
Histologic examination of an assemblage of Psittacosaurus (Dinosauria:
Ceratopsia) juveniles from the Yixian Formation (Liaoning, China).
The Anatomical Record (advance online publication)
DOI: 10.1002/ar.23324
http: // onlinelibrary.wiley.com/doi/10.1002/ar.23324/abstract

Psittacosaurus is one of the most abundant dinosaurs known, which
allows for extensive study of its growth and form. Previous studies
have evaluated growth trajectories of Psittacosaurus using bone
histology. However, we present the first study of Psittacosaurus
comparative juvenile histology and describe the histology of
Psittacosaurus within its first year of life based on multiple
sections taken from an exquisite monospecific assemblage of juveniles
from the Yixian Formation in Liaoning, China. Specimens studied had
femur lengths ranging from 30–36 mm. The five juveniles examined all
have similar histologic patterns in the midshaft and epiphyseal
regions showing that there is limited plasticity in bone development
in juvenile Psittacosaurus and that all of the specimens in the
assemblage were likely the same age. The microstructure patterns are
compatible with the hypothesis that Psittacosaurus was precocial and
that these juveniles were neonates. Based on comparisons with other
juvenile ornithischians, juvenile Psittacosaurus had a growth rate
similar to Orodromeus, slower than that of Maiasaura, Dysalotosaurus,
or hadrosaurs consistent with small body size. Our results support
previous studies that demonstrated that the orientation of vascular
canals is likely not solely reflective of growth rate, but is also
affected by underlying biomechanical, structural processes. The number
of studies done on theropod and sauropodomorph histology dwarfs those
of ornithischians. More studies of ornithischian histology are
necessary in order to better establish phylogenetic trends in
microstructure and to learn more about growth in this important clade.