Echinoderms and Aspects of Evolutionary Theory

Extract

Discussions of evolutionary theory in paleontology include the topics of overall diversity through time, the tempo and mode of evolution, and the consequences of the parallel between ontogeny and phylogeny. The first of these topics – diversity through time and the significance of major echinoderm radiations and extinctions – is the subject of other discussions in this short course and will not be considered here. Detailed evolutionary studies using echinoderms are complicated by the compound nature of their skeleton which tends to disarticulate very rapidly after death. Complete specimens usually reflect rapid burial, and large populations may be relatively rare in many stratigraphic sequences. Possible exceptions include the carboniferous blastoid Pentremites and various Teriary echinoid lineages. Indeed Paul (1977b) has concluded that the fossil record of echinoderms would seem to be of little use in testing evolutionary ideas. While not numerous, studies of echinoderms have contributed to evolutionary theory and selected cases will be discussed below.