The shallow-water strata of the lower West Falls Group (Upper Devonian) in New York can be subdivided into three units on the basis of extensive black shale tongues from the deep-water Rhinestreet Shale. These units are the “Millport equivalent,” “Beers Hill equivalent,” and “Meads Creek equivalent” in ascending stratigraphic order. Two distinctive community-types developed during lower West Falls deposition: a shallower water spiriferacean-rhynchonellide-bivalve species ensemble, and a deeper water assemblage of unattached epibenthic and sessile semi-infaunal brachiopods. During deposition of the “Beers Hill equivalent,” an additional diverse assemblage—the Nervostrophia-Devonochonetes Community—developed in a unique array of muddy, delta platform environments flanked by seaward, delta front sand bars. The evolution of lower West Falls marine ecosystems represents a complex interaction of biological and physical patterns, of which regional differences in substratum type, and the evolution of those differences through time, played a major role.