PALEO-DISTRIBUTION OF FOSSIL DECAPOD POPULATIONS DURING MIDDLE CRETACEOUS IN NORTH-EAST TEXAS

The decapod crustacean collection from Weno and Pawpaw formations, Comanche Series, Cretaceous in northeast Texas, has increased substantially based upon recent collecting and availability of specimens from amateur collectors in the area. Due to local topography and shallow dipping beds, the specimens have been collected from outcrops with a limited stratigraphic interval. Incorporating these new specimens and the field data permit construction of a spatial density and diversity map, of the decapods from mid Cretaceous deposits, in the Ft. Worth area.

The specimens collected there belong to the superfamilies Galatheoidea Samouelle, 1819; Palinuroidea Latreille, 1802; Raninoidea De Haan, 1839; Nephropoidea Dana, 1852; Callianassoidea Dana, 1852; Dorippoidea MacLeay, 1838; Erymoidea Van Straelen, 1924 [imprint 1925]; and others. They document a paleoenvironment with a high diversity and abundance of decapods, and fossils in general.

More than 1000 specimens collected from 21 sites around Ft Worth, Texas, have been used to create maps of diversity and abundance of Cretaceous decapods. These maps reveal that in a small geographic area there are some significant variations in diversity and abundance. In some localities, the crabs are the dominant taxa whereas the lobsters are present in small numbers, and in other localities the lobsters dominate. At the localities where crabs dominate the fauna, Xanthosia spp. are the main taxa Hoploparia sp. and Linuparus sp. are the lobsters that represent the majority of the taxa in the lobster-dominated localities.

Analysis of this kind of map will permit definition of a paleo-distribution of the decapod population at the family or even generic level. In order to better understand the association patterns of fossil decapods and compare them to patterns of living decapod population, maps of present day distribution and association will be analyzed and compared with the paleo-distribution map.

Future research will concentrate on interpreting environmental conditions present at these localities that are contributing to these notable differences in density and diversity of Cretaceous decapods in northeast Texas.