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Dimetrodon species in Texas



From: Ben Creisler
bcreisler@gmail.com


A new online paper:



Christen D. Shelton, P. Martin Sander, Koen Stein and Herman Winkelhorst (2013)
Long bone histology indicates sympatric species of Dimetrodon (Lower
Permian, Sphenacodontidae).
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S175569101300025X
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9016348&fulltextType=RA&fileId=S175569101300025X

The Briar Creek Bonebed (Artinskian, Nocona Formation) in Archer
County is one of the richest sources of Dimetrodon bones in the Lower
Permian of Texas, USA. Based on size, a small (D. natalis), an
intermediate (D. booneorum), and a large species (D. limbatus) have
been described from this locality. It has been proposed that these
traditionally recognised species represent an ontogenetic series of
only one species. However, the ontogenetic series hypothesis is
inconsistent with the late ontogenetic state of the small bones, as
suggested by their osteology and degree of ossification. Histological
analysis of newly excavated material from the Briar Creek Bonebed has
resolved some of the discretion between these two competing
hypothesis, confirming the coexistence of a small (D. natalis) with at
least one larger Dimetrodon species. An external fundamental system is
present in the largest sampled long bones identified as D. natalis.
The histology of D. natalis postcrania is described as incipient fibro
lamellar bone. This tissue is a combination of parallel-fibred and
woven-fibred bone that is highly vascularised by incipient primary
osteons. The species status of D. booneorum and D. limbatus remain
unresolved.