OUT WITH THE OLD, IN WITH THE NEW; HOW HAVE NEW GASTROPOD SYSTEMATIC SCHEMES AFFECTED FAUNAL COMPARISONS?

Instability of systematics in paleobiology at higher taxonomic ranks has occasionally caused reduced research interest in some groups while awaiting stability to re-emerge. Abandonment of the systematic organization of the Gastropoda some 20 years ago (Ponder, 1988; Ponder and Lindberg, 1997; Bouchet and Rocroi, 2005) may have “de-railed” what seemed to be an expansion of research interest in the group that was building in the mid 1970’s. At that time usage of higher taxa in the Gastropoda had stabilized sufficiently to encourage comparison of snail faunas at several taxonomic levels with an eye toward answering questions of community structure, paleobiogeography, provincial structure and paleoceanographic or paleocurrent modeling and faunal im- and emigration. Databases being used by paleobiologists are dependent on stability of the systematics for accurate comparability. Gastropodology would benefit greatly from such stability and Bouchet and Rocroi (2005) may be accepted by enough workers to provide (e.g. Squires, 2011) a basis for faunal analysis. To that end, we have re-visited studies of the marine snail faunas of the Maastrichtian Fox Hills (FH) and Tertiary (Paleocene) Cannonball Formations (Cb) in order to understand their compositions and structures across the K—T boundary, applying the taxonomy of Bouchet and Rocroi (2005). As an “out group”, the Paleocene snail fauna of the Agatdal Fm. (Ag) of Greenland (Kollman and Peel, 1983) was also re-examined.

Species were reassigned to higher taxa from original authors (Stanton, 1920; Erickson, 1974) to those of Bouchet and Rocroi, (2005). Comparisons indicate 2% of genera were common to all three units, 14% occurred only in the FH, 17% only in the Cb, and 67% in the Ag; 11% of all families were in common, 24% in the FH, 22% in the Cb, and 43% in the Ag; 10% of superfamilies occurred at all three, 28% in the FH, 21% in the Cb, and 41% in the Ag; 1% of all superfamilies were found in all three units, 28% in the FH, 21% in the Cb, and 41% in the Ag. Compared as well between the local fauna of the Fox Hills and Cannonball Seas, 15% of genera, 18% of families, and 26% of superfamilies occurred in both seas; 35% of genera, 41% of families, and 41% of superfamilies were unique to the FH Sea, and 50% of genera, 41% of families, and 33% of superfamilies occurred only in the Cb Sea.