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Stegosaurus plates and spikes histology with growth and age
From: Ben Creisler
bscreisler@yahoo.com
A new online advance paper:
SHOJI HAYASHI, KENNETH CARPENTER, MAHITO WATABE and LORRIE A. MCWHINNEY (2011)
Ontogenetic histology of Stegosaurus plates and spikes.
Palaeontology (advance online publication)
DOI: 10.1111/j.1475-4983.2011.01122.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2011.01122.x/abstract
The dinosaur Stegosaurus is characterized by osteoderms of alternating plates
and terminal paired spikes. Previous studies have described the histological
features and possible functions of these osteoderms. However, ontogenetic
changes are poorly documented. In this study, the ontogenetic changes of the
osteoderms are examined using eight different ontogenetic skeletons (a
juvenile, a subadult, a young adult, and five old adults based on the cortical
histology of their body skeletons). The juvenile plate and subadult spike show
thin cortex and thick cancellous bone. The young adult plates have an extensive
vascular network, which is also seen in old adults. Old adult spikes are
different from old adult plates in having a thick cortex and a large axial
channel. The cortical histology, in both plates and spikes, show
well-vascularized bone tissue consisting of dense mineralized fibres in young
adult forms. In old adult forms, the bone tissues in the
spikes become more compact and are extensively remodelled. This might
contribute to the structural reinforcement of the spikes. The plates in old
adult forms also show extensive remodelling and lines of arrested growth, but
only limited signs of compaction. The timing for acquisition of features seen
in old adults is different between plates (an extensive vascular network in the
young adult) and spikes (a thick cortex with a large axial channel in old
adults). The result suggests that the timing for plate and spike functions is
different. The extensive vascular networks seen in large plates suggest their
function is for display and/or thermoregulation. The thick cortical bone of
spikes of old adults suggests that spikes acquire a weapon function for defence
ontogenetically late.