Table 2.

Summary table comparing life history distribution across amniotes

	Characteristics of distribution
Body mass	All unimodal and right skewed Squamata < Aves <  < Mammals
Offspring/female size	Offspring/female size ratio approximately the same across placental mammals, birds and squamates (7–8%) marsupials <  <  < turtles <  < birds ≈ placentals ≈ squamates
Brood size	Mode is 1 in mammals, 2 in birds and squamates
Reproductive frequency	The overall mode and distribution of reproductive frequency is extremely similar across amniote groups
Relative brood mass	All unimodal and right skewed. But no placental mammal has a relative brood mass higher than 70%. Small in turtles, very small in marsupials
Yearly fecundity	Distribution of reptiles and birds very similar (right skewed distribution with a mode of 4–6 young). Mammalian mode is 1–2 offspring per year
Reproductive output	Similar overall in squamates, birds and mammals (low intercepts associated with steep slopes), low intercept in turtles, very low intercept, and shallow slope in marsupials