Caycedoae micheliorum Bowman & Varol, 2021
After Tatiana Caycedo (and the Caycedo family of Colombia), an educator in Houston, TX, USA.
Circular to broadly elliptical heliolith having a single non-birefringent disc, a birefringent column in various heights in plan view and a narrow central canal.
Circular-subcircular heliolith has one disc and a column. In the side-view, the disc appears slightly concave, and a depression is present on the proximal side. The column displays variable height and possesses a narrow central canal. The species of this genus are regularly observed in plan and side views because they have a tall column that allows them to settle naturally in both views. The terminology of Caycedoa is presented in Fig. 10 in Bowman & Varol (2021).
The species of this genus are often erroneously assigned to Bomolithus. The holotype of Bomolithus elegans (type species of Bomolithus) is an SEM micrograph (Roth, 1973; Pl. 15, figs. 1) revealing two different discs of equal diameter and a high column. The mobile mount technique used by Bowman & Varol (2021) indicates that Bomolithus elegans possesses birefringent discs, thereby proving that it is a different species. Subsequently, specimens comparable to the paratype (but not to the holotype) have been erroneously placed into Bomolithus elegans by many authors, including Perch-Nielsen (1977, 1985), Varol (1989) and Bown (2010, 2016). The mobile mount technique demonstrates that the forms comprising a non-birefringent disc and a birefringent column are very different from Bomolithus. These forms were assigned to the new genus Caycedoa by Bowman & Varol (2021).
Caycedoa and Heliolithus are differentiated based on the birefringent character of the disc observed in plan-view (e.g. Caycedoa is non-birefringent, Heliolithus is birefringent). In the side view, the column base is cone-shaped in Caycedoa but appears flat in Heliolithus.
Caycedoa is a circular to broadly elliptical form that consists of one disc, whereas Asinithistimorfi is an elliptical form composed of two discs. In both Caycedoa and Asinithistimorfi, the disc or discs are non-birefringent in plan-view, which a diagnostic criteria that separate these genera from other helioliths.
Bowman, A. R. & Varol, O. 2021. A Taxonomic Revision of Heliolithaceae - Applications in Resolving the Problematic Calcareous Nannofossil Biostratigraphy of the Paleocene. In: M. Montenary, M. (Ed.). Calcareous nannofossil biostratigraphy of the Stratigraphy and timescales. 6: 43-223.