The podotrematous crab family Dakoticancridae includes four genera, Dakoticancer Rathbun, Tetracarcinus Weller, Avitelmessus Rathbun, and Seorsus Bishop, all known solely from the Late Cretaceous of North America. Lathelicocarcinus Bishop, originally referred to the family, must be reassigned. Fine details of anatomy, preserved on specimens of D. overanus Rathbun and A. grapsoideus Rathbun, permit description of genital openings and interpretation of functional morphology of appendages. Although one species, D. australis Rathbun, has been found associated with burrow structures, all were probably vagrant epifaunal animals on fine- to medium-grained siliciclastic substrata. Food was probably obtained by generalized low-level predation and scavenging. Results of a cladistic analysis are consistent with the stratigraphic data suggesting that T. subquadrata Weller is nearest the rootstock of the family and that other taxa within the family are derived from it.