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Titanosauriformes (Sauropoda) body size evolution



Ben Creisler
bcreisler@gmail.com

A new paper not yet mentioned:


L. M. de Souza and R. M. Santucci (2014)
Body size evolution in Titanosauriformes (Sauropoda, Macronaria).
Journal of Evolutionary Biology (advance online publication)
DOI: 10.1111/jeb.12456
http://onlinelibrary.wiley.com/doi/10.1111/jeb.12456/abstract



Titanosauriformes is a conspicuous and diverse group of sauropod
dinosaurs that inhabited almost all land masses during Cretaceous
times. Besides the diversity of forms, the clade comprises one of the
largest land animals found so far, Argentinosaurus, as well as some of
the smallest sauropods known to date, Europasaurus and Magyarosaurus.
They are therefore good candidates for studies on body size trends
such as the Cope's rule, the tendency towards an increase in body size
in an evolutionary lineage. We used statistical methods to assess body
size changes under both phylogenetic and nonphylogenetic approaches to
identify body size trends in Titanosauriformes. Femoral lengths were
collected (or estimated from humeral length) from 46 titanosauriform
species and used as a proxy for body size. Our findings show that
there is no increase or decrease in titanosauriform body size with age
along the Cretaceous and that negative changes in body size are more
common than positive ones (although not statistically significant) for
most of the titanosauriform subclades (e.g. Saltasaridae,
Lithostrotia, Titanosauria and Somphospondyli). Therefore, Cope's rule
is not supported in titanosauriform evolution. Finally, we also found
a trend towards a decrease of titanosauriform mean body size coupled
with an increase in body size standard deviation, both supporting an
increase in body size variation towards the end of Cretaceous.