Velonalithus emelinesalleyae Varol, 2025
From the Greek velona, meaning needle, refers to its shape
The elongated form Velonalithus consists of three blades pointed at both ends. In its natural settling profile, Velonalithus exhibits strong birefringence, displaying white to yellowish-white interference colours. Notably, it demonstrates parallel extinction (with an extinction angle of 0°) and length slow (+) elongation. This optical property distinguishes it from Triquetrorhabdulus, which exhibits length-fast (-) elongation.
Velonalithus differs from Orthorhabdus by having pointed ends, whereas the latter is pointed at one end but truncated at the other. Additionally, Orthorhabdus exhibits inclined extinction, while Velonalithus shows parallel extinction.
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222