Analyses of large acatate sheet tracings, close-up photos and 105 sub-horizontal quadrat surfaces at four localities near the base of the Guadalupe Mountains Escarpment indicate that the biotic framework of the upper Capitan reef was built by about 35 species: one codiacean (Eugonophyllum sp.), 17 calcisponges, 9 bryozoans, one richthofenid brachipod, some crinoid (known only from columns), 4 Problematica and microbes. This widespread fossil community included members of the Constructor, Baffler and Binder Guilds. A re-evaluation of the Guild Concept (Fagerstrom, 1987, 1991) highlights the validity of the functional roles of the Constructor and Binder Guilds for reef construction. Members of the Baffler Guild, however, need to be revised and an interpretation of microbial micrite and cryptic biota remains controversial. Open surface phylloid algal and cryptic sponge-bryozoan dominated sub-communities were of only local importance. The upper Capitanmassive differs from its Permian conterparts in the low diversity and areal cover of the frame-building biota, low micrite content and abundant micro-frameworks, i.e, intergrown small sponges, Problematica and syndepositional cements (botryoidal and isopachous, fibrous calcite).