Lower Cretaceous marine rocks exposed in New Mexico, southcastcrn Colorado, Oklahoma, and Kansas contain well-preserved faunal assemblages that formed either as in-place, disturbed-neighborhood, or transported assemblages. Five faunal associations characterize lithofacies of the bay-to-shoreface depositional model and possess uniquc structures. The Nucula-Nuculana association represents a speciediverse, infaunal detritus-suspension community occupying the open-bay muddy substrate. The Corbula-Breviarca association was a species-dominant, infaunal suspension feeding community on the lower shoreface. The Texigryphaea-Lopha community formed biostromes on the shoreface. The mid-shoreface supported a species-diverse, infaunol suspension feeding community of Scabrotrigonia and Turritella. The Arenicolites trace fossil association characterizes the upper shoreface-beach habitat.