The Chelydridae have a long fossil history, with extinct species reported from North America, all over Asia and Europe, far outside their present range. The earliest described chelydrid is Emarginachelys cretacea, known from well-preserved fossils from the Maastrichtian stage of the Late Cretaceous of Montana. Another well-preserved fossil chelydrid is the Late PaleoceneProtochelydra zangerli from North Dakota. The carapace of Protochelydra is higher domed than that of the recent Chelydra, a trait conjectured to be associated with the coexistence of large, chelonivorous (i.e., turtle-eating) crocodilians. Another genus, Chelydropsis, contains several well-known Eurasian chelydrid species that existed from the Oligocene to the Pliocene.citation needed
de Broin, F. 1969. Contribution a l’etude des cheloniens. Cheloniens continentaux du Cretace Superieur et du Tertiaire de France. Memoires du Muséum National d'Histoire Naturelle. Vol. C, No. XXVIII
Ericson, B. R. 1973. A new chelydrid turtle (Protochelydra zangerli), from the late Paleocene of North Dakota. Scientific Publications of the Science Museum of Minnesota, New Series 2(2):1-16
Gaffney, E. S. 1975. Phylogeny of the chelydrid turtles: a study of shared derived characters in the skull. Fieldiana Geology, 33:157-178
Parham, J. F., C.R. Feldman, and J. R. Boore. The complete mitochondrial genome of the enigmatic bigheaded turtle (Platysternon): description of unusual genomic features and the reconciliation of phylogenetic hypotheses based on mitochondrial and nuclear DNA. BMC Evol Biol. 2006; 6: 11. Published online February 7, 2006. doi:10.1186/1471-2148-6-11.
Whetstone, K. N. 1978. A new genus of cryptodiran turtles (Testudinoidea, Chelydridae) from the Upper Cretaceous Hell Creek Formation of Montana. University of Kansas Science Bulletin. Lawrence, Kansas. 51(17):539-563.