DECAPOD PALEOCOMMUNITY STRUCTURE OF NORTHERN MISSISSIPPI AND TENNESSEE

Decapod assemblages occur in the Upper Cretaceous Coon Creek Formation of the Mississippi Embayment. The Blue Springs Dakoticancer australis Assemblage resembles the South Dakota Dakoticancer Assemblages in faunal composition, mode of preservation and distribution, but differs significantly in taxonomic composition and taphonomic fabric. The Avitelmessus Assemblage may consist of the single decapod taxon, Avitelmessus grapsoideus, or of A. grapsoideus associated with a molluscan assemblage, and is preserved as repeated, discrete assemblage, a biocoenosis, in near shore shale-rich or clay-rich and muddy-sand lithosomes of the Coon Creek and Ripley Formations. The Blue Springs Dakoticancer australis Assemblage, preserved in an off shore facies, consists of at least two preservational cycles over-printed on a molluscan thanatocoenosis. Both decapod assemblages represent preserved Cretaceous crab community fractions and occupy intermediate positions in Late Cretaceous marine food chains and food webs. Hypothetical food chains and food webs are presented for these community fractions and their cohorts.