Orthorhabdus serratus

Orthorhabdus serratus Bramlette & Wilcoxon, 1967

An elongated nannofossil has two blades and a ridge truncated at one end and pointed at the other with a toot-like projection. This species can naturally settle in plan view and appear extinct (the c-axis is parallel to the microscope axis). Due to the development of tooth-like projection, very difficult to rotate it on its side view. Orthorhabdus serratus is a triangular shape displaying high birefringence with parallel extinction having a tangential c-axis (perpendicular to the length of the specimen).

Orthorhabdus serratus is distinguished from Triamutilaferrum martinii by having a parallel extinction at its side view and having a toot-like projection. The latter species has oblique inclined extinction and lacks tooth-like projection. Both above species differ from the biconical species of Triquetrorhabdulus by having a tangential c-axis, whereas species of Triquetrorhabdulus have an axial c-axis.

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., 1967a. Calcareous nannofossils from Neogene of Trinidad, Jamaica, and Gulf of Mexico. University of Kansas Paleontological Contributions, Papers 29, 1-7.

Martini, E., 1965. Mid-Tertiary calcareous nannoplankton from Pacific deep-sea cores. Colston Papers 17, 393-411.