Abstract
Fourteen species of the solitary corals belonging to eight genera and six families were identified and illustrated from the Campanian - Maastrichtian Aruma Formation, northeast of Riyadh, Saudi Arabia. Cunnolites (Plesiocunnolites) riyadhensis, Actinoseris riyadhensis and Asteroseris arabica are believed to be new. Genus Cunnolites dominates the identified fauna with six species namely Cunnolites (C.) reussi, C. (P.) orbignyi, C. (P.) longifossata, C. (P.) scutellum, C. (C.) profundus and C. (P.) riyadhensis (n. sp.). The other species belong to Aulosmilia cuneiformis, Rennensismilia inflexa, Rennensismilia sp., Acrosmilia conica, Actinoseris riyadhensis (n. sp.), Asteroseris arabica (n. sp.), Montlivaltia sp. and Conicosmilotrochus sp. The solitary corals have various growthforms from cupolate to flabellate, trochoid, ceratoid, cylindrical and patellate. The studied taxa inhabit soft substrate in turbid water environment with low rate of sedimentation. Borings and scars are rare, encrustations occur on the lower surfaces of some specimens. Partial mortality, overgrowths, disorientation or any records of life impedences due to sedimentation and unstable substrate were not observed in the studied specimens. Pedestals and columnar growths are also absent. Bioerosion is observed in some specimens in the form of pittings produced by predators.