Developmental types of spatangoid echinoids. Left photos: Tests of a male and a female of the echinoid Brachysternaster chesheri. The brood pouches (bp) in the female and the difference in gonopore size in the two sexes are seen (gp; the male test is cleaned, whereas the female still has some of the organic material partially covering the gonopores; the black dot at the left side is inserted to indicate the size of the clean gonopore). Photos from http://www.nhm.ac.uk/research-curation/research/projects/echinoid-directory/taxa/taxon.jsp?id=429. Right diagram: Evolution of developmental types of Cretaceous spatangoid echinoids. Only the period from the Aptian to the Maastrictian is shown, but seven successive outgroups from the Valanginian to the Aptian all had pluteus larvae. Ap, Aptian; Al, Albian; Ce, Cenomanian; T, Turonian, C, Coniacian; S, Santonian; Ca, Campanian; M, Maastrichtian. Modified from .