Extensive endemism among the maastrichtian non-marine ostracoda of India with implications for Palaeobiogeography and “out of India” dispersal

Abstract

An analysis of the 33 genera and 100 species of non-marine Ostracoda recorded from the Maastrichtian intertrappean deposits and the Lameta Formation of Peninsula India, and their comparison with key contemporary faunas from Mongolia, China, Alaska, Europe, Africa and South America, shows them to be much more diverse that the other faunas. They are also extremely endemic, as only two of the 100 species are known elsewhere. One of these, Cypridea cavernosa Galeeva, also occurs in Mongolia and China, while Frambocythere tumiensis Helmdach, occurs in China, Africa, France and Spain but as distinct subspecies. With near 100% endemism in India, it is perhaps not surprising that very few of the extremely abundant and diverse Chinese and Mongolian Maastrichtian genera such as Cypridea, Talicypridea, Limnocypridea (ex Quadracythere) and Mongolocypris were able to overcome the competition and colonise India, while others, such as Ziziphocypris, and Nanxiongium, are entirely absent and failed completely. Many Indian taxa, on the other hand seem to have dispersed out from India, such as Mongolianella, Cypridopsis, Limnocythere, Eucypris, Cyprois, and perhaps Candona, down diversity gradients to many parts of the Maastrichtian world. Genera such as Paracypretta are confined there and Gomphocythere virtually so. In general, this analysis of the Indian Maastrichtian non-marine Ostracoda supports the extended isolation of the sub-continent during the Cretaceous and the “Out of India” hypothesis with respect to its zoogeographical relations with other areas and their faunas. This is notwithstanding the extraordinary dispersal advantage that many non marine cypridacean ostracods enjoy, by virtue of their parthenogenetic means of reproduction and possession of a desiccation/freezing resistant egg that is capable of long-distant wind dispersal.