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Mussaurus (sauropodomorph) bone histology and growth



From: Ben Creisler
bcreisler@gmail.com

A new advance online paper:


Ignacio Alejandro, Cerda Diego Pola & Anusuya Chinsamy (2013)
Osteohistological insight into the early stages of growth in Mussaurus
patagonicus (Dinosauria, Sauropodomorpha).
Historical Biology (advance online publication)
DOI:10.1080/08912963.2012.763119
http://www.tandfonline.com/doi/full/10.1080/08912963.2012.763119


Here, we describe the bone histology of juvenile specimens of the
basal sauropodomorph Mussaurus patagonicus and interpret its
significance in terms of the early growth dynamics of this taxon. Thin
sections from three juvenile specimens (femur length, 111–120 mm) of
Mussaurus were analysed. The sampled bones consist of multiple
postcranial elements collected from the Late Triassic Laguna Colorada
Formation (El Tranquilo Group, Patagonia). The cortical bone is
composed of fibrolamellar bone tissue. Vascularisation is commonly
laminar or plexiform in the long bones. Growth marks are absent in all
the examined samples. The ‘epiphyses’ of long bones are all formed by
well-developed hypertrophied calcified cartilage. The predominance of
woven-fibred bone matrix in cortical bones indicates a fast growth
rate in the individuals examined. Moreover, given the existence of
growth marks in adult specimens of Mussaurus, as in other
sauropodomorphs, and assuming that the first lines of arrested growth
was formed during the first year of life, the absence of growth marks
in all the bones suggest that the specimens died before reaching their
first year of life. Compared with the African taxon Massospondylus
carinatus (another basal sauropodomorph for which the bone histology
has been previously studied), it appears that Mussaurus had a higher
early growth rate than Massospondylus.