Viviparity does not affect the numbers and sizes of reptile offspring

Viviparity (live-bearing) has independently evolved from oviparity (egg-laying) in more than 100 lineages of squamates (lizards and snakes).
We might expect consequent shifts in selective forces to affect per-brood reproductive investment (RI = total mass of offspring relative to maternal mass) and in the way in which that output is partitioned (number versus size of offspring per brood). Based on the assumption that newly-born offspring are heavier than eggs, we predicted that live-bearing must entail either increased reproductive investment or a reduction in offspring size and/or fecundity.
However, our phylogenetically-controlled analysis of data on 1,259 squamate species revealed no significant differences in mean offspring size, clutch size or RI between oviparous and viviparous squamates.
We attribute this paradoxical result to (1) strong selection on optimal offspring sizes, unaffected by parity mode, (2) the lack of a larval stage in amniotes, favouring large eggs even ...