Cretaceous gastropods: contrasts between Tethys and the temperate provinces

Abstract

During the Cretaceous Period, gastropod faunas show considerable differences in their evolution between the Tethyan Realm (tropical) and the Temperate Realms to the north and south. Like Holocene faunas, prosobranch gastropods constitute the dominant part of Cretaceous marine snail faunas. Entomotaeneata and opisthobranchs usually form all of the remainder. In Tethyan faunas the Archaeogastropoda form a consistent high proportion of total taxa but less than the Mesogastropoda throughout the period. In contrast, the Temperate faunas beginning in Albian times show a decline in percentages of archaeogastropod taxa and a significant increase in the Neogastropoda, until they constitute over 50 percent of the taxa in some faunas. The neogastropods never attain high diversity in the Cretaceous of the Tethyan Realm and are judged to be of Temperate Realm origin.Cretaceous Tethyan gastropod faunas are closely allied to those of the “corallien fades” of the Jurassic and begin the period evolutionarily mature and well diversified. Greatest diversity in Tethys occurs in the lagoonal shales associated with the rudist or coral framework environments of the Cretaceous carbonate platforms. Their distribution was pan-tropical, extending in instances across the vast reaches of the Pacific. Three categories of Tethyan gastropods are analyzed. The first group consists of those of Jurassic ancestry. Except for the Nerineacea, these taxa are long ranging but evolutionarily conservative, showing only moderate diversification during the Cretaceous, and becoming extinct with the close of the era. The second group originates mainly during the Barremian and Aptian, reaches a climax in diversification during middle Cretaceous time, and usually declines during the latest Cretaceous, with most not lasting through the terminal event. The third group originates late in the Cretaceous and consists of taxa that manage to either survive the Cretaceous-Tertiary crisis or give rise to forms of prominence among Tertiary warm water faunas.There is a trend among the Tethyan gastropod assemblages for increased provincialism with time. Early and middle Cretaceous taxa are especially widely distributed, but the latest Cretaceous is a time of restricted occurrence for many forms.Temperate Realm gastropod faunas are less diverse than those of Tethys during the Early Cretaceous. Their source is among long lived, extra-Tethys groups, but is increased, especially during major phases of transgression, by immigrants from Tethys. They show a steady increase in diversity, primarily among the Mesogastropoda and Neogastropoda. This trend culminates in latest Cretaceous times when the gastropod assemblages of the clastic provinces of the inner shelf contain an abundance of taxa outstripping that of any other part of the Cretaceous of either realm.Extinction at the Cretaceous-Tertiary boundary is much less pronounced in the Temperate Realm than in the Tethys. Among the Temperate Realm assemblages loss is of generic and species level taxa, unlike the extinction of the family Actaeonellidae or the superfamily Nerineacea and a host of less prominent groups in Tethys. In essence, by the late Maastrichtian, gastropod faunas of the Temperate Realm had attained a modern faunal aspect.

A comparison of recent and fossil large, high-spired gastropods and their environments: the Nopparat Thara tidal flat in Krabi, South Thailand, versus the Swiss Kimmeridgian carbonate platform

“…The nerineoids were a diverse superfamily of Mesozoic gastropods (Sohl 1987) with over 90 published genera (Barker 1990). The superfamily Nerineoidea (Zittel 1873) ranges from the Hettangian to the Maastrichtian (Pchelintsev 1965;Barker 1990Barker , 1994, although the earliest forms have been reported from the Triassic of Turkey and Germany (Peter W. Skelton, pers.…”

The paleoecological significance of nerineoid mass accumulations from the Kimmeridgian of the Swiss Jura Mountains

“…The Nerineoidea was one of the most diverse gastropod superfamilies in the Tethyan realm (Sohl, 1987), and the Late Jurassic represents the phase of maximum radiation (Korotkov, 1997). Nerineoid occurrences have been reported from Mesozoic deposits around the world, including Asia, Europe, Africa, and North and South America (e.g., Wieczorek, 1992).…”

“…They are also known locally from Pacific seamounts and the Caribbean (e.g., Woodring, 1952). They had both wide longitudinal and latitudinal representation, although they are less common at higher paleolatitudes (Ziegler, 1964;Sohl, 1987;Saul and Squires, 2002). The superfamily Nerineoidea ranges from the Hettangian to the Maastrichtian (Pchelintsev, 1965;Barker, 1990Barker, , 1994.…”

The Cretaceous and Paleocene pleurotomariid (Gastropoda: Vetigastropoda) fauna of Seymour Island, Antarctica

“…Many mollusks also survived the K-T extinction event (Stilwell et al, 2004). Sohl (1987Sohl ( , p. 1105 noted that Pleurotomariidae had a cosmopolitan distribution during the Jurassic and Early Cretaceous but experienced a marked reduction in the number of genera surviving into the Tertiary. More recently, Pacaud (2004, fig.…”

“…20) documented the survival of three genera into the Danian of northern Europe. Pleurotomariid diversity at the species level was greatest during the Cenomanian, declined rapidly by the Turonian, and remained relatively stable during the remainder of the Cretaceous (Sohl, 1987(Sohl, , p. 1105 fig. 10).…”