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Dinosaur origins



From: Ben Creisler
bcreisler@gmail.com


A new online paper:

Kevin Padian (2013)
The problem of dinosaur origins: integrating three approaches to the
rise of Dinosauria.
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000431
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9016653&fulltextType=RA&fileId=S1755691013000431



The problem of the origin of dinosaurs has historically had three
dimensions. The first is the question of whether Dinosauria is
monophyletic, and of its relationships to other archosaurs. This
question was plagued from the beginning by a lack of relevant fossils,
an historical burden of confusing taxonomic terms and a rudimentary
approach to devising phylogenies. The second dimension concerns the
functional and ecological adaptations that differentiated dinosaurs
from other archosaurs, a question also marred by lack of phylogenetic
clarity and testable biomechanical hypotheses. The third dimension
comprises the stratigraphic timing of the origin of dinosaurian groups
with respect to each other and to related groups, the question of its
synchronicity among various geographic regions, and some of the
associated paleoenvironmental circumstances. None of these dimensions
alone answers the question of dinosaur origins, and they sometimes
provide conflicting implications. Since Dinosauria was named, one or
another set of questions has historically dominated academic
discussion and research. Paradigms have shifted substantially in
recent decades, and current evidence suggests that we are due for more
such shifts. I suggest two changes in thinking about the beginning of
the “Age of Dinosaurs”: first, the event that we call the
(phylogenetic) origin of dinosaurs was trivial compared to the origin
of Ornithodira; and second, the “Age of Dinosaurs” proper did not
begin until the Jurassic. Re-framing our thinking on these issues will
improve our understanding of clade dynamics, timing of
macroevolutionary events, and the effects of Triassic climate change
on terrestrial vertebrates.