First Record of Three Pleistocene Scleractinian Coral Families in Seir Peninsula, Farasan Islands: Expanding Red Sea Biodiversity

ABSTRACT The Pleistocene reef terraces of the Red Sea serve as a valuable geological archive, reflecting past marine conditions and environmental fluctuations. Among these, the Farasan Islands, located in the southern Red Sea off the Saudi Arabian coast, host a remarkable diversity of coral families, including Acroporidae, Agariciidae, Euphylliidae, Fungiidae, Lobophylliidae, Merulinidae, Pocilloporidae, and Poritidae, underscoring the region's ecological significance during the Pleistocene epoch. This study focuses on the taxonomy, biogeography, and evolutionary trends of three previously unreported scleractinian coral families Diploastraeidae, Pachyseridae, and Rhizangiidae from the Pleistocene reef units at the Seir Peninsula, Farasan Islands. We document, for the first time, the occurrence of Diploastrea heliopora and Pachyseris inattesa in the Pleistocene of the Red Sea, with P. inattesa representing the first known fossil record of this species globally. A comparison between Pleistocene and extant populations reveals a significant decline in D. heliopora abundance, reflecting substantial environmental and ecological shifts over time. P. inattesa , historically misidentified under different taxonomic names, is an endemic Red Sea species with a cryptic nature, whose first fossil occurrence in this study provides new insights into its evolutionary history and biogeographic distribution. This study advances our understanding of coral diversity and environmental changes in the Red Sea's Pleistocene reefs. It highlights the importance of fossil records in tracking biodiversity shifts and underscores the need for further research on the geographic distribution and conservation of these coral genera.