Crotalia jafari: a new weakly calcified holococcolithophore genus and species from the Southwest Indian Ocean

We here describe a distinctive weakly calcified holococcolithophore Crotalia jafari gen. et sp. nov. from the Southwest Indian Ocean phytoplankton. The coccospheres of Crotalia jafari measure 8–15 ?m in diameter, and possess 430–538 coccoliths, with each coccolith measuring less than 1 ?m in diameter. The coccoliths are tightly attached to each other by an organic layer. Their central area appears open. Finger-shaped extensions are present in the peripheral coccoliths, and stretch from the hexagonal surface layer towards the basal plate. The basal plate is flat and composed of irregular wall fabric. The crystallites of the coccoliths are small. These morphological features make this holococcolithophore unique among the extant and fossil coccolithophores. The described species is therefore placed into the new genus ‘Crotalia’. This study also suggests that high diversity of weakly calcified (and still undescribed) holo- and heterococcolithophores may exist in the Southern Ocean, which requires additional careful observation.