Article: Callovian colonial corals from the Tuwaiq Mountain Limestone of Saudi Arabia

The earliest development of coral-bearing strata in Central Saudi Arabia took place during deposition of the Tuwaiq Mountain Limestone (upper Middle-Upper Callovian). It does not appear to constitute a major barrier reef, but rather a series of isolated corals and coral biohcrms; coral heads (20-50 cm in diameter) are scattered in life position within an extensive sheet of pure limestone (20^1-0 m thick) stretching for more than 1000 km along strike in Central Saudi Arabia. This sheet could be described as an extensive biostrome. A striking feature of the Tuwaiq Mountain Limestone coral fauna is the low diversity of species that persisted throughout the development of the formation. These species are: Meandraraea gazaensis Alloiteau and Farag, Ovalastraea caryophylloides Goldfuss, Trigerastraea collignoni (Alloiteau), Columnocoenia lamherti Alloiteau and Brachthelia sp. A possible explanation for the low diversity of the fauna is inimical ecological conditions or palaeobiogeographical barriers which could have prevented the historical accumulation of species from neighbouring areas. Similar factors are responsible also for the endemism of the Jurassic Arabian fauna including ammonites, foraminifers, algae, ostracods, nautiloids, brachiopods and echinoids.