CRETACEOUS INOCERAMID BIOGEOGRAPHY - A REVIEW

Cretaceous inoceramid bivalves were widely distributed. They did not thrive in very shallow or very warm seas, and are therefore rare in Tethyan shallow deposits. In the Berriasian-Barremian interval they occurred mainly in the temperate seas, and their distribution is often bipolar. In the Albian-Cenomanian interval, inoceramids were varied and numerous, especially in clays and chalks, but rare in the greensand-type strata. Most inoceramid groups were cosmopolitan during this interval. From the Turonian onwards the North Pacific Province is characterized by endemic inoceramid faunas. Following the opening of the South Atlantic Ocean in the Turonian, new inoceramid lineages in the Southern Hemisphere from Brazil to Madagascar evolved in co-occurrence with other cosmopolitan groups. Many Coniacian and Santonian species were widely distributed and short-lived, but in the Campanian and Maastrichtian a homogeneous fauna was apparently confined to eastern North America and western Eurasia. Few of the last inoceramid species in the Upper Cretaceous have stratigraphic value, and, in contrast to the Lower Cretaceous, they are common in warm-water deposits, for example, in Libya, Nigeria, and Tunisia.