Late Ordovician agglutinated foraminifera from the Ra'an Shale Member, Qasim Formation of Saudi Arabia as indicators of the O40 maximum flooding surface

We report the first finding of Late Ordovician Foraminifera recovered from the Ra'an Shale Member exposed in theQassim region of Saudi Arabia. The foraminiferal assemblages consist entirely of agglutinated forms, predominantly monothalamids dominated by the genus Thuramminoides. Additionally, rare specimens of two-chambered, pseudochambered, and multichambered forms are also found in the assemblages. The O40 maximum flooding surface is placed at the level of maximum diversity of agglutinated foraminifera. The occurrence of the genus Subreophax in the Ra'an Shale Member revises the known evolutionary history of the pseudomultichambered agglutinated foraminifera.