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Morrison Formation sauropod neural spine bifurcation (free pdf)

From: Ben Creisler

This new open-access paper has not been mentioned yet:

Mathew J. Wedel, M.J. & Michael P. Taylor (2013)
Neural Spine Bifurcation in Sauropod Dinosaurs of the Morrison
Formation: Ontogenetic and Phylogenetic Implications.
PalArch’s Journal of Vertebrate Palaeontology 10(1) (2013), 1-34.
ISSN 1567-2158. 34 pages + 25 figures, 2 tables.
Free pdf:

It has recently been argued that neural spine bifurcation increases
through ontogeny in several Morrison Formation sauropods, that
recognition of ontogenetic transformation in this ‘key character’ will
have sweeping implications for sauropod phylogeny, and that Suuwassea
and Haplocanthosaurus in particular are likely to be juveniles of
known diplodocids. However, we find that serial variation in sauropod
vertebrae can mimic ontogenetic change and is therefore a powerful
confounding factor, especially when dealing with isolated elements
whose serial position cannot be determined. When serial position is
taken into account, there is no evidence that neural spine bifurcation
increased over ontogeny in Morrison Formation diplodocids. Through
phylogenetic analysis we show that neural spine bifurcation is not a
key character in sauropod phylogeny and that Suuwassea and
Haplocanthosaurus are almost certainly not juveniles of known
diplodocids. Skeletochronology based on the sequence of skeletal
fusions during ontogeny can provide relative ontogenetic ages for some
sauropods. Although such data are sparsely available to date and often
inconsistent among sauropod genera they provide another line of
evidence for testing hypotheses of ontogenetic synonymy. Data from
skeletal fusions suggest that Suuwassea and Haplocanthosaurus are both
valid taxa and that neither is an ontogenetic morph of a known