Dwarf megateuthidid belemnites from the Bathonian of Kachchh (India: Gujarat) and their significance for palaeobiogeography

摘要

We describe in detail new finds of dwarf megateuthidid belemnites from the Middle-Late Bathonian of Kachchh (Western India), previously only rarely mentioned in the literature. The material is assigned to a new genus and species, Challinoria challinori gen. et sp. nov. Extensive morphological comparison together with analysis of the biogeographical distribution of comparable taxa suggests affinity of the newly described taxon with Early Bajocian megateuthidids from South America, showing the existence of a previously unknown megateuthidid habitat area in the Southern Hemisphere during the Bajocian and Bathonian. The biogeographical patterns and trans-equatorial migration routes of Middle Jurassic megateuthidids are discussed. The occurrence of the newly described taxon in the Bathonian of India, along with the lack of Mediterranean and Indo-Pacific records of similar age, may be connected with the short-term opening of a marine trans-Gondwanan seaway.