Triquetrorhabdulus extensus Theodoridis, 1984
Orthorhabdus extensus (Theodoridis, 1984) Young & Bown, 2014
Broad species of Pennalithus Varol have three unequal-sized blades. Its c-axis is vertical to the natural settling of the nannolith. The dentate blade enlarged further to look like a sail. Transverse striations ornament the surface of the dentate blade.
Pennalithus extensus differs from Pennalithus rugosus (Bramlette & Wilcoxon, 1967) and Pennalithus farnsworthii (Gartner, 1967) by having a massive sail like a dentate blade. It is further distinguished from Pennalithus farnsworthii by its straight median blade, whereas the latter has a distinctly curved median blade.
Pennalithus extensus is identified from Pennalithus striatus (Müller, 1974) by lacking additional longitudinal ridges.
Pennalithus extensus is differentiated from Pennalithus finifer (Theodoridis,1984) by having lateral blades in the same plane, whilst the latter has distinctly arched lateral blades.
Bramlette, M. N. & Wilcoxon, J. A., (1967): Middle Tertiary calcareous nannoplankton of the Cipero section, Trinidad, W.I. - Tulane Studies in Geology and Paleontology. 5: 93-131.
Gartner, S., (1967): Calcareous nannofossils from Neogene of Trinidad, Jamaica, and Gulf of Mexico. - University of Kansas Paleontological Contributions, Papers. 29: 1-7.
Müller, C., (1974): Calcareous nannoplankton, Leg 25 (Western Indian Ocean). - Initial Reports of the Deep Sea Drilling Project. 25: 579-633.
Theodoridis, S., (1984): Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. - Utrecht Micropaleontological Bulletin. 32: 1-271.
Young, J. R. & Bown, P. R., (2014): Some amendments to calcareous nannoplankton taxonomy. - Journal of Nannoplankton Research. 33(1): 39-46.
Late Miocene - Early Pliocene
DSDP Leg 23, Site 219, Laccadive-Chagos Ridge, Indian Ocean