Re-discovery of a “living fossil” coccolithophore from the coastal waters of Japan and Croatia

Abstract

The extant coccolithophore Tergestiella adriatica Kamptner, which had not been reported since its original description in 1940, was recently re-discovered in coastal-nearshore waters at Tomari, Tottori (Japan) and offshore Rovinj (Croatia). Morphological analysis shows that extant Tergestiella and the Mesozoic genus Cyclagelosphaera (Watznaueriaceae), thought to have been extinct since the early Eocene (~ 54 Ma), are virtually identical. Molecular phylogenetic study supports the inference that T. adriatica is a direct descendent of Cyclagelosphaera . It is therefore a remarkable example of a living fossil. Our documentation of patchy coastal distribution in living T. adriatica and records of rare occurrences of fossil Cyclagelosphaera in Oligocene–Miocene shallow water sediments , from the New Jersey shelf, suggest that Tergestiella / Cyclagelosphaera was restricted to nearshore environments during much of the Cenozoic. This restricted ecology explains the lack of fossil Tergestiella / Cyclagelosphaera recorded in open ocean sediments deposited during the last 54 myr. Floristic study of coccolithophores in the coastal and offshore waters of Tomari over a six-year period, show that T. adriatica occurs synchronously with the unusual neritic species, Braarudosphaera bigelowii , in mid-June. The environmental factors that induce the co-occurrence of these two taxa are uncertain, and T. adriatica did not co-occur with B. bigelowii at any other sites. • Extant Tergestiella adriatica Kamptner was re-discovered from coastal waters. • Mesozoic genus Cyclagelosphaera is a synonym of extant Tergestiella . • Cyclagelosphaera did not go extinct in the early Eocene. • Calcareous plankton survivors of the K/Pg event were predominantly neritic.