Nannotax3 - ntax_Farinacci - Asinithistimorfi

Original descriptions of taxa - also emended descriptions for a few 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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Citation: Asinithistimorfi Bowman & Varol 2021

Type species: Asinithistimorfi aubryae Bowman and Varol 2021

Type repository: the author's collection

Diagnosis: An elliptical heliolith comprises two non-birefringent discs and a moderate-high column hollow and closed by a plug, generally appearing rough or unstructured.

Description: Two non-birefringent discs and a column characterize this moderate large and elliptical heliolith. The moderate-high column and plug possess a rough appearance. The median disc is slightly wider than the proximal disc, and a narrow canal may be visible in some specimens at the side view. The discs may only be observed under phase-contrast and bright-field settings (Plate 2, figs. 20 and 24). In plan-view, the column and plug artificially resemble overgrown Dictyococcites under polarized light.

Optical properties: In plan-view, the discs appear non-birefringent, whereas the column and plug appear strongly birefringent. Entire species appear birefringent in the side-view. In cross polarized light, the distal side shows a dextrogyre-type extinction pattern (e.g. Pl. 3, figs. 10, 14), whereas the proximal side is characterized by a laevogyre-type extinction pattern (e.g. Pl. 3, figs. 11, 15). When using the gypsum plate, with the species orientated in the north-south position, the distal view will show the blue regions corresponding to the horizontal axis, while the proximal view will show the blue sectors corresponding to the vertical axis. The terminology of Asinithistimorfi is presented in Fig. 8.

From Greek Asinithisti, unusual, and morfi, form—referring to the bizarre appearance that characterizes the general structure of the genus.

Remarks: The bizarre rough appearance of the plug and the elliptical shape of the species are diagnostic identification features. Asinithistimorfi is distinguished from Caycedoae by the following: Asinithistimorfi is an elliptical form composed of two discs, whereas Caycedoae is circular/broadly elliptical forms consisting of one disc. In both genera, the disc(s) are non-birefringent in plan-view, separating these genera from other helioliths.

References:

Bowman, A. R. & Varol, O. (2021). A taxonomic revision of Heliolithaceae—Applications in resolving the problematic calcareous nannofossil biostratigraphy of the Paleocene. In, Montenari, M. (ed.) Stratigraphy & Timescales 6. Academic Press (2): 43-223. gs

CATALOG - Asinithistimorfi

References:

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