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Ianthodon (Synapsida: Sphenacodontia) anatomy (free pdf)

Ben Creisler

A new paper in open access:

F. Spindler, D. Scott, and R. R. Reisz (2015)[2014]
New information on the cranial and postcranial anatomy of the early
synapsid Ianthodon schultzei (Sphenacomorpha: Sphenacodontia), and its
evolutionary significance.
Fossil Record  18: 17-30

Newly identified material belonging to the holotype specimen of
Ianthodon schultzei substantially increases our knowledge of this
poorly known basal sphenacodont synapsid from the fossil site in
Garnett, Kansas (Missourian, Late Pennsylvanian). The original
description, based on a partial dermal skull roof, is augmented with
information on the palate and braincase, together with data on the
mandible and a few postcranial elements. The known skeletal morphology
resembles that of Haptodus garnettensis, another synapsid taxon known
from this locality, but with fewer marginal, distinctly recurved teeth
and smaller teeth on the transverse flange of the pterygoid. Although
recognizing that the holotype and only known specimen represents a
juvenile individual, Ianthodon appears to reflect a more basal
sphenacodontian condition than H. garnettensis. A restricted
phylogenetic analysis based on previous work and newly scored
characters for Ianthodon, Cutleria and Pantelosaurus supports this
hypothesis. The Garnett locality appears to preserve an assemblage of
synapsids (Haptodus, Ianthasaurus, Ianthodon) that are close to the
base of the large clade that includes Edaphosauridae and
Sphenacodontia, suggesting that an initial diversification of this
clade occurred well within the Carboniferous Period.