The fossil record of cyanobacteria is rich throughout more than 2000 Ma of Proterozoic time (Schopf & Klein, 1992), but is comparatively poor for the 543 Ma of the Phanerozoic Era. Many Proterozoic microfossils are preserved in early diagenetic silica deposits. In contrast, most fossils of algae and cyanobacteria recovered from Phanerozoic strata are preserved in carbonates. Many of them were calcified during or immediately after their lifetime, which facilitated their preservation (Riding, 1991; Pentecost, 1991).
Many Proterozoic cyanobacterial microfossils have morphotypically close modern counterparts, thus testifying to an early evolutionary origin, early ecological specialization and conservative maintenance of the basic adaptive properties of this group of the original oxygenic phototrophs (Knoll et alii, 1986; Knoll & Golubic, 1992).
This contribution examines a microfossil common in southern Europe in the Cretaceous strata of Periadriatic carbonate platforms, which are sedimentologically comparable with the modern carbonate platforms of Florida and the Bahamas (see D'Argenio, 1970; D'Argenio et alii, 1975; Radoičić & D'Argenio, 1999; Vlahović et alii, 2002). The fossil was originally described as Aeolisaccus kotori and attributed to the problematic fossil worm: Aeolisaccus Elliott, 1958 (Radoičić, 1959). Based on a detailed study of morphology and the morphometric evaluation of a large fossil population, De Castro (1975) provided a convincing re-interpretation of this fossil as the remains of an ancient cyanobacterium. In support of his interpretation, De Castro invoked possible modern counterparts among mat-forming cyanobacteria, described by Monty (1967) from the mudflats on Andros Island, Bahamas. Here we investigate the state of preservation of this fossil using high resolution SEM imaging to compare it with the modern mat-forming Scytonema populations of Andros Island, Bahamas. Based on confirmed cyanobacterial identity, and in accordance with the rules of zoological nomenclature, we propose to change the name of this fossil.