Early Permian rugose coral Cyathaxonia faunas from the Sibumasu Terrane (Southeast Asia) and the southern Sydney Basin (Southeast Australia): Paleontology and paleobiogeography

Abstract

The Sibumasu Terrane consists of allochthonous blocks located between Gondwana and Eurasia and had a tectonic evolutionary history characterized by rifting from Gondwana during the Early Permian, northward drifting during the Mid–Late Permian, and final amalgamation with Eurasia during the Triassic. The rugose coral Cyathaxonia faunas, which are typically composed of small, solitary, and non-dissepimented rugose corals, occur in the Lower Permian of the Sibumasu Terrane in Southeast Asia and the southern Sydney Basin of southeastern Australia. These Cyathaxonia faunas suggest cold or cool water shallow marine conditions, which is also supported by the occurrence of glaciomarine dropstones and diamictites in associated sediments and immediately underlying strata. Significant differences in the composition of coral faunas between the Sibumasu Terrane and the Cathaysian continent (comprising tectonic blocks such as South China and Indochina) indicate that the Sibumasu was probably located at the northern margin of Gondwana during the Early Permian, as opposed to Cathaysia then located near the Paleo-equator in the eastern Paleotethys. The Middle Permian coral faunas in the Sibumasu Terrane are dominated by both solitary and compound Waagenophyllidae. The latter is a common element in the Cathaysian continent. But, some distinctive and endemic taxa occurred in the Sibumasu Terrane during this time, suggesting that it was still an independent (isolated) paleobiogeographical entity, located at a certain distance from the Cathaysian continent. A total of eleven small solitary coral species from the Sibumasu Terrane and the southern Sydney Basin are described in detail. Of these five are new (Ufimia khaokaeonoi, Zaphrentites shidianense, Euryphyllum khaokaeoyai, E. kanchanaburi, and ?Claviphyllum baoshanense).