*3Chapter 1 Marine Molluscan Larval Types and Their Behavior

In a series of publications, Frýda et al. (2008; Frýda, 2004) used gastropod protoconch characters to indicate the presence of planktotrophic and nonplanktotrophic larvae back into the earlier Paleozoic, including data for many extinct higher taxa. Their data indicate that a high level of heterochrony has always been characteristic of gastropods. Changes from a planktotrophic to a nonplanktotrophic larval life style have evidently occurred repeatedly.