orbitolina orbitolina orbitolina is an extinct genus of foraminifera belonging to the order textulariida and family orbitolinidae. fossils of this genus are widely found in beds deposited in the tethys ocean ranging from aptian (early cretaceous)) to cenomanian (early late cretaceous) in age. it has been used as a shallow carbonate platform facies marker and as a cretaceous index fossil. orbitolinatemporal range: aptian-cenomanian~ scientific classification domain: eukaryota clade: diaphoretickes clade: sar phylum: retaria infraphylum: foraminifera class: globothalamea order: textulariida family: †orbitolinidae subfamily: †orbitolininae genus: †orbitolinalamarck 1816 species orbitolina concava lamarck, 1816o. discoideaconoidea gras, 1852o. lenticulata lamarck, 1816 the test of the organism has the shape of a cone, with the proloculus (initial chamber) at the apex of the cone and increasingly large cuplike chambers forming the remainder of the test. each chamber is further subdivided by numerous partitions.