Table 1.

Higher taxa assigned to the two morphological/functional groups discussed in the text

Passive (nonmobile) animals	Active (self-mobile) animals
Porifera, P, m	Various molluskan groups: Rostroconchs, Hyolithids, C
Archaeocyatha, C	Gastropods, p, M
Anthozoa (corals), P, m	Infaunal bivalves, p, M
Bryozoa, P, M	Cephalopods, P, m
Brachiopods, C, P	Polychaetes, C, p, M
Epifaunal (attached and cemented) bivalves, p, M	Arthropods, C, P, M
Pelmatazoan echinoderms, P	Echinoids, M
Graptolites, c, p	Conodonts, p
Tube-dwelling incertae sedis, c	Chordates, M

Letters following taxon names identify the categories to which their containing classes were assigned in Sepkoski's 1981 analysis (13). C, factor I (the Cambrian Fauna); P, factor II (the Paleozoic Fauna); M, factor III (the Modern Fauna). The variation in factor loadings of different classes in Sepkoski's factor analysis is noted by uppercase letters (for major contribution to that evolutionary fauna) and lowercase letters (moderate contribution to that evolutionary fauna).