Bryozoa from the Maastrichtian Korojon Formation, Western Australia

Abstract

The first Australian Cretaceous bryozoan fauna is described from the Upper Campanian – Lower Maastrichtian Korojon Formation from the Giralia Anticline in north-western Western Australia. Bryozoans are the numerically dominant element in a sclerobiont community dependent on the abundant large inoceramids, utilizing both valves in life position as well as reworked shell fragments. A total of 68 species-level taxa are described (22 cyclostomes and 46 cheilostomes); 50 of these are new (12 cyclos-tomes and 38 cheilostomes) and the remaining 18 taxa are left at various levels of open nomenclature. They are referred to 47 genera (14 cyclostome and 33 cheilostome genera, 11 of which are new), with a total of 10 taxa left in open nomenclature. One new family, Cardabiellidae, is introduced. The total Late Cretaceous bryozoan fauna known from the Southern Hemisphere remnants of the Gondwana supercontinent – South America, Africa, India, Antarctica, Australia, Zealandia – is significantly less diverse than that known from the Northern Hemisphere, where the European Chalk Sea fauna constitutes the diversity hotspot. The addition of the Korojon fauna described here expands our knowledge of the Cretaceous bryozoan fauna from the Southern Hemisphere considerably, particularly with respect to the youngest bryozoan order, the Cheilostomata. And importantly, the Korojon fauna, more than doubles the proportion of Late Cretaceous cheilostome genera endemic to the Southern Hemisphere from 12.5% to more than 25% of the total number of Late Cretaceous genera presently known from this realm. We suggest that this significant expansion may well warrant a reassessment of the role of Southern Hemisphere bryozoan faunas in the recovery from the Cretaceous-Paleogene biotic turnover.