Palaeobiogeographic relationships and diversity of Upper Devonian ammonoids from Western Australia

WA Museum Records and Supplements | Updated 10 years ago

Abstract - Upper Devonian ammonoids from the Canning Basin of Western Australia represent one of the most diverse faunas globally known. It consists of cosmopolitan (pantropical), endemic and "spot" taxa (with disjunct distribution in few widely separated basin). Endemism is low at the generic but very significant (ca. 50%) at the species level. Linked with regional facies change and eustatic influences, there were alternating episodes with lowdiverse, relatively highly endemic or with species-rich and rather cosmopolitan faunas. Faunal similarities both in the Frasnian and Famennian were closest with Germany, slightly less with North Africa, SW England, the Ardennes, and the Montagne Noire. Frasnian faunal links with the Timan and eastern North America were severed after the Frasnian-Famennian boundary whilst relationships with the Urals and Poland became closer. Faunal similarities were clearly more dependent on regional facies developments of plates than on their spatial distance. The regional diversity curve reflects both global extinctions and radiations as well as effects of Canning Basin structural evolution. Three major extinctions, the Bugle Gap, Lower Kellwasser and Upper Kellwasser Events occurred in the Frasnian. Not a single ammonoid species regionally survived the Frasnian-Famennian boundary and the basal Famennian lacked ammonoids all over Australia. The post-Annulata Event regression regionally initiated a strong final decline of ammonoid faunas.