Original descriptions of taxa. For coccolithophores, and many calcispheres, these are pages from the Farinacci & Howe Catalog of Calcareous Nannofossils. In other cases (e.g. non-calcifying haptophytes) the data is directly compiled on this site. The "Catalogue of Calcareous Nannofossils" was originally compiled by Prof A. Farinacci 1969-1989, since 2000 it has been updated and extended by Richard Howe - see The Farinacci and Howe Catalog - an Introduction.
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Original Description Diagnosis: An elongated nannofossil with two unequal blades in the same plane and a median ridge. One end of the blades is often more pointed than the other. The surface of the wider blade (dentate blade) is frequently ornamented with transverse striations. The median ridge may be straight or curved. Etymology: From the Latin penna, wing, feather – refers to its blades. Extra details from original publication Optical properties: In the plan view, when the ridge is aligned with the microscope axis, Pennalithus is in constant extinction, with the optic axis perpendicular to the microscope stage in this orientation (Plate 19, Figs. 1-3, 5-7 and Plate 20, Figs. 1, 3, 5-7). Pennalithus displays high birefringence in the side view, parallel extinction (extinction angle is 0°), and exhibits length-slow (+) elongation (Plate 19, Figs. 9-11, 13-15 and Plate 20, Figs. 9-16).
Remarks:Pennalithus differs from Orthorhabdus by having parallel (straight) extinction, whereas the latter has inclined (oblique) extinction in their side view. Moreover, both ends of Pennalithus are pointed, whereas Orthorhabdus has one end pointed and the other truncated.
References:
Varol, O. (2025). A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222. gs
Pennalithus: Catalog entry compiled by Jeremy Young. Viewed: 12-2-2026