The taphonomy and paleoecology of a well-preserved mosasaur (DSM 10716) are reported from Oktibbeha County, Mississippi. The mosasaur was recovered from the Prairie Bluff Chalk, the exact stratigraphic position and age confirmed using established foraminiferal zonation for the Late Cretaceous of the U. S. Gulf Coastal Plain. A species identification of Mosasaurus cf. hoffmanni Mantell is given using shape and structure of the quadrate and jugal, as well as tooth counts for the dentary, maxilla, and pterygoid. DSM 10716 exhibits well-preserved trace fossils including feeding traces and the remains of encrusting bivalves. The associated fossils are probed for similar phenomena to modern whale falls and other ancient carcass falls. Based on associated fossils present on DSM 10716, evidence for a mobile scavenger stage, a possible enrichment opportunist stage, and a reef stage is established. No chemosynthetic organisms were detected to suggest the existence of a sulfophilic stage.