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AW: Proportion of torso devoted to pelvis query

--- David Peters <davidrpeters@charter.net> schrieb am Mi, 2.9.2009:

> Von: David Peters <davidrpeters@charter.net>
> Betreff: Proportion of torso devoted to pelvis query
> An: 
> Datum: Mittwoch, 2. September 2009, 20:15
> Was wondering if there are any
> studies detailing ratio of torso/pelvis?
> Was also wondering what the consensus is regarding number
> of sacrals captured in terrestrial species? Two is basal for
> amniotes. What does it mean when three, four, five, seven
> and ten are incorporated? 

The Pine/Wedel talk at SVP07 might be of interest:

"Increase in the number of sacral vertebrae is a pervasive evolutionary trend 
in nonavian dinosaurs. The primitive sacral count for Dinosauria is three. 
Increases in the number of sacrals occurred across Dinosauria as a clade, and 
also as repeated parallel events within clades. For example, the number of 
sacrals increased to five in basal theropods, and this count persisted along 
the âbackboneâ of theropod phylogeny from the base of Neotheropoda to the base 
of Aves (including Archaeopteryx). However, increases to six or more sacrals 
occurred independently in ceratosaurs, alvarezsaurs, therizinosaurs, 
oviraptorosaurs, troodontids, and dromaeosaurs. The number of sacral vertebrae 
also increased independently in sauropodomorphs, thyreophorans, ornithopods, 
and ceratopsians (and in many subclades thereof ). The increase in sacral 
vertebrae in Dinosauria passes all of the standard tests for a driven 
evolutionary trend (i.e., moving minimum, subclade, and
 ancestor-descendant tests). Further, it is homoplastic, with increases 
occurring independently in every major dinosaurian clade and in many of the 
subclades. Remarkably, the trend shows few or no reversals in non-avian 
dinosaurs; sacral count increases in all lineages but decreases are limited to 
a handful of singleton taxa, and even these reductions are doubtful (i.e., 
because of ontogenetic or
preservational factors). The incorporation of large numbers of vertebrae into 
the synsacrum in the evolution of birds can now be seen as an instance of this 
pervasive, homoplastic, apparently irreversible, driven evolutionary trend."