Petasaria heterolepis

Taxonomy:

Catalog entries: Petasaria heterolepis

Original description: Unicellular with a single flagellum which is 6-7 µm long (Figs 61, 62). The flagellum is without Flimmer-hairs, but very thin hair-shaped appendages are present, probably mucilaginous. The cell body is rounded, 4-6 µm in diameter, as seen in whole mounts, and covered by a periplast of two different scale categories. One scale type (Figs 64, 65) is shaped like a wide-brimmed hat (Latin: petasus), and it contains mainly silica. These scales measure 1.7 x 1.9 µm - 2.9 x 3.2 µm, the base being circular or oval-triangular. Part of the base is patternless and lined by a raised rim (e.g., Fig. 65), the other part is patterned by perforations of various sizes. In this latter area, which lacks a raised rim, the largest perforations are nearest the scale periphery. Near the scale centre, always in the perforated area, each scale carries a hollow projection, somewhat higher than the raised rim. This projection on the side away from the patternless basal part of the scale is also patternless, towards this side, however, an ornamentation which in some cells consists of small spines (Fig. 65), in others of a more elaborate crest, also perforated (Fig. 63). The other scale type is unmineralised, more-or-less regularly circular, c. 0.45 µm in diameter (Figs 65 and 65, inset). In each scale eight arms radiate from the centre to the circular periphery. The arms are generally equally spaced, though sometimes more irregular. In the central part the arms are interconnected and this gives the scale an appearance like a spider's web.

Geological Range:
Last occurrence (top): Extant. Data source: present in the plankton
First occurrence (base): within no known fossil record modern (0.00-0.00Ma, base in "Holocene" stage). Data source: [JRY]

Petasaria heterolepis compiled by Jeremy R. Young viewed: 20-5-2025 Taxon Search: Advanced Search Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=20285 Go to Archive.is to create a permanent copy of this page - citation notes

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