Scleractinian corals of the Albian (uppermost Lower Cretaceous)—overview, revision, evaluation

Abstract

Abstract. In the current study, scleractinian corals from the Albian (uppermost Lower Cretaceous; 112.6–99.7 Ma) including 337 species (280 taxa assigned to species; 57 taxa kept in open nomenclature) from 147 genera (six of which include subgenera) belonging to 42 families (two of which include subfamilies; and incertae sedis) are evaluated and revised. Two new species (Apoplacophyllia asiatica, new species and Trigerastraea sikharulidzeae, new species) are described and two lectotypes are designated. Some specimens are illustrated for the first time, and new material (from Austria) is presented. The coral material includes records from 30 regions in Africa, the Americas, the Arctic, Asia, Australasia, and Europe. The most extensive records of Albian corals are from tropical/subtropical and arid areas, including the U.S.A., Mexico, Greece, France, and Spain. Over three-quarters of the Albian taxa belong to morphological forms having little to no hermatypic character (sensu Coates & Oliver), including species of the cerioid-plocoid group (genera: 36.7%; species: 38.5%), solitary taxa (genera: 26.5%; species: 28%), and branching forms (genera: 26.5%; 39 species = 11.5%). The coral faunas of the Albian are dominated by corals of “modern” microstructural groups sensu Roniewicz & Morycowa (76 genera = 51.7%; 169 species = 50.1%). Compared to the lowermost Cretaceous (Berriasian), which showed that 91% of the species and 83% of the genera belonged to previously established microstructural groups, the Lower Cretaceous ends with “modern” groups having become dominant. During the lower and middle Albian, the vast majority of taxa belonged to colonial forms (both 74%). A shift took place during the upper Albian, significantly increasing the number of solitary species to over 40% of the Albian fauna (42.9%). Throughout the Albian, the most diverse coral assemblages include non-reefal faunas, suggesting that, in contrast to, e.g., the Barremian–Aptian time period, reefal developments were less crucial for coral recruitment during this time. This study of the Albian fauna was used as the basis for synthesizing classical taxonomic works with modern microstructural data and recent DNA analyses in order to propose both a modified taxonomic framework and a working hypothetical phylogenetic tree for 41 scleractinian families occurring in the fossil record.