Early evolution of the family Siderastraeidae (Scleractinia; Cretaceous-extant)

Critical review of Mesozoic and Paleogene fossil type material and morphological comparison with the type genus Siderastrea of the family Siderastraeidae propose that the earliest members of the family date from the Late Valanginian (Early Cretaceous) and gained diversity during the Early Cretaceous. The most common member is the new genus Eosiderastrea, which encompasses all Cretaceous material that was formerly assigned to the extant coral genus Diploastrea. The new genus is characterised by an astreoid, rarely plocoid or cerioid calicular arrangement, and a subregular septal symmetry representing hexameral, heptameral, octameral and decameral symmetries. The septal blades are made of medium-large trabeculae. Synapticulae are present. Eighteen Cretaceous species are assigned to the new genus. The genus Eosiderastrea occurs worldwide and ranges from the Late Valanginian to the Santonian. Cretaceous material formerly assigned to Siderofungia is assigned to the new genus Palaeosiderofungia, which is characterised by a thamnasterioid calicular arrangement with calices predominantly arranged in rows and an extended coenosteum. The septal blades are made of medium-large trabeculae; synapticulae are present. There is no septal symmetry. Apart from the type species Thamnasteria exigua, another four unnamed species are known. The new genus occurs only in the Boreal and Central to Western Tethys and ranges from the Aptian to Santonian. The occurrence of the extant Siderastrea in the Cretaceous cannot be ruled out. Isolated finds are reported from the Aptian onwards.