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Alligator bone growth rings paper + Valdoraptor and other news

From: Ben Creisler

A new paper in PeerJ that may be of interest:

Holly N. Woodward, John R. Horner & James O. Farlow (2014)
Quantification of intraskeletal histovariability in Alligator
mississippiensis and implications for vertebrate osteohistology.
PeerJ 2:e422
doi: http://dx.doi.org/10.7717/peerj.422

Bone microanalyses of extant vertebrates provide a necessary framework
from which to form hypotheses regarding the growth and
skeletochronology of extinct taxa. Here, we describe the bone
microstructure and quantify the histovariability of appendicular
elements and osteoderms from three juvenile American alligators
(Alligator mississippiensis) to assess growth mark and tissue
organization within and amongst individuals, with the intention of
validating paleohistological interpretations. Results confirm previous
observations that lamellar and parallel fibered tissue organization
are typical of crocodylians, and also that crocodylians are capable of
forming woven tissue for brief periods. Tissue organization and growth
mark count varies across individual skeletal elements and reveal that
the femur, tibia, and humerus had the highest annual apposition rates
in each individual. Cyclical growth mark count also varies
intraskeletally, but data suggest these inconsistencies are due to
differing medullary cavity expansion rates. There was no appreciable
difference in either diaphyseal circumference or cyclical growth mark
circumferences between left and right element pairs from an individual
if diaphyses were sampled from roughly the same location. The
considerable intraskeletal data obtained here provide validation for
long-held paleohistology assumptions, but because medullary expansion,
cyclical growth mark formation, and variable intraskeletal growth
rates are skeletal features found in tetrapod taxa living or extinct,
the validations presented herein should be considered during any
tetrapod bone microanalysis.


Darren Naish blog on paper identifying Valdoraptor as ornithomimid


Cast of Maidstone Iguanodon back on display



Placodonts explainer