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Kentrosaurus (Stegosauria) bone histology and growth rates

From: Ben Creisler

A new online paper:

Ragna Redelstorff, Tom R. Hübner, Anusuya Chinsamy & P. Martin Sander (2013)
Bone Histology of the Stegosaur Kentrosaurus aethiopicus
(Ornithischia: Thyreophora) from the Upper Jurassic of Tanzania.
The Anatomical Record (advance online publication)
DOI: 10.1002/ar.22701

Using bone histology, a slow growth rate, uncommon for most dinosaurs,
has been interpreted for the highly derived stegosaur Stegosaurus
(Ornithischia: Thyreophora) and the basal thyreophoran Scutellosaurus.
In this study, we examine whether this slow growth rate also occurs in
the more basal stegosaur Kentrosaurus from the Tendaguru beds of
Tanzania. The bone histology of six femora of Kentrosaurus
representing an ontogenetic series from subadult to adult was studied,
as well as one scapula. The primary bone is mainly highly vascularized
fibro-lamellar bone with some reticular organization of the vascular
canals. In addition to LAGs and annuli, distinctive shifts in the
pattern of vascularization occur, which have been interpreted as
potential growth marks. The variation in the development of growth
marks may reflect annual climatic fluctuations. The overall bone
depositional rate, and hence growth rate in Kentrosaurus appears to be
higher than in Stegosaurus and Scutellosaurus. Considering that
Stegosaurus is the larger-sized of the two stegosaurs, this would be
contrary to an earlier supposition that small-bodied dinosaurs have
slower growth rates than larger ones. Our finding of rapid rates of
bone deposition in Kentrosaurus suggests that slow growth rates
previously reported in Scutellosaurus and Stegosaurus are not a
phylogenetic characteristic of the Thyreophora. Thus, slow growth
rates are not plesiomorphic for the Thyreophora. We propose that the
slow growth rates documented in the highly derived Stegosaurus could
have been secondarily derived or alternatively that Kentrosaurus is
the exception having increased growth rates.