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Did early squamates have live birth?
From: Ben Creisler
A paper about squamate origins now officially published that has not
been mentioned on the DML :
R. Alexander Pyron and Frank T. Burbrink (2014)
Early origin of viviparity and multiple reversions to oviparity in
Ecology Letters 17(1): 13–21
Viviparity has putatively evolved 115 times in squamates (lizards and
snakes), out of only ~ 140 origins in vertebrates, and is apparently
related to colder climates and other factors such as body size.
Viviparity apparently evolves from oviparity via egg-retention, and
such taxa may thus still have the machinery to produce thick-shelled
eggs. Parity mode is also associated with variable diversification
rates in some groups. We reconstruct ancestral parity modes accounting
for state-dependent diversification in a large-scale phylogenetic
analysis, and find strong support for an early origin of viviparity at
the base of Squamata, and a complex pattern of subsequent transitions.
Viviparous lineages have higher rates of speciation and extinction,
and greater species turnover through time. Viviparity is associated
with lower environmental and body temperatures in lizards and
amphisbaenians, but not female mass. These results suggest that parity
mode is a labile trait that shifts frequently in response to
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