Melanopsis from the Pleistocene of the Hula Valley (Gastropoda: Cerithioidea)

Abstract

Pleistocene Melanopsis from three cores in the Hula Valley (a northern section of the Jordan Valley) were reinvestigated, and six species were found: buccinoidea, costata, obediensis, multiformis, corrugata, and turriformis. These species are described, compared, and their chronological appearance in the cores presented in terms of depths beneath the surface. There appears to have been an overall continuity in the Melanopsis fauna of the Jordan Valley throughout the Pleistocene. Some of the previously reported variation in the isotopic records of Melanopsis shells from the Hula cores may perhaps represent the different physiology of different species. Fossil hybrids of the Jordan Valley, as found also in this study, offer the earliest direct evidence of hybridization among molluscs that is still going on today in the same region and aquatic system, among the same species. Correlations with lithology suggest that none of the Melanopsis species dwelt in swamps; obediensis, multiformis, and corrugata were lake dwellers; and turriformis dwelt also in transitional habitats, between lakes and swamps. Correlations with recent species suggest that the paleo-landscape of buccinoidea consisted of a spring or stream, and that of costata of a bank of a river or a lake. Where both costata and buccinoidea were found, the paleo-landscape may have consisted of a spring or stream flowing into a river or lake. About a quarter of the local extinctions coincided with brief spreading of swamps. Incomplete evidence may perhaps suggest a competitive succession among the three fossil lake-dwelling species.