INCUBATION-TIME IN REPTILIAN EGGS

An allometric analysis of reptilian incubation time was performed. Inc ubation time increased with increasing egg mass (allometric exponent = 0.14, r(2) = 0.31). However, significant heterogeneity was found with in the Reptilia for this character. If periods of developmental arrest are excluded the orders Crocodylia, Testudinata, and the suborder Ser pentes have the shortest incubation times and the lizards the longest. Significant differences within lizard families were also observed (Ig uanidae, Agamidae, Gekkonidae, and Lacertidae have shorter incubation times than the Varanidae and Teiidae). Preliminary analyses indicate t he heterogeneity in incubation time observed within the Squamata is co rrelated with differences in brain mass; this is similar to findings f or mammals. The variation in incubation time indicates the existence o f differences in growth rates in reptilian groups and suggests a parti al explanation for the observed distribution of viviparity within the Squamata.