Origin and evolution of the genera Lonsdaleia and Actinocyathus: Insights for the Mississippian palaeogeography from the western Palaeotethys

Abstract

Representatives of the subfamily Lonsdaleiinae Chapman, 1893 are common in the Mississippian of the western Palaeotethys. A general analysis of the origin, distribution and evolution of that subfamily has been undertaken. The most probable hypothesis for the origin of the genus Lonsdaleia McCoy, 1849 is to acquire colonialism via the genus Axophyllum Milne Edwards and Haime, 1851. Actinocyathus d’Orbigny, 1849 would be a descendant of Lonsdaleia by increasing integration in the colonies. The first occurrences of Lonsdaleia have been recorded in the lower Visean from northern Britain and northern Tianshan Mountains of northwestern China, but the diversification and migration to the whole Palaeotethys only happened in the late Visean. Three hypotheses are proposed on that matter. The Serpukhovian was also a period of migrations and diversification for these genera. Both Lonsdaleia and Actinocyathus have been recorded in Bashkirian refuges, the Sverdrup Basin in northern Laurasia and the Tindouf Basin in northern Africa, respectively. The division of the western Palaeotethys into six subprovinces based on the distribution of corals is proposed.