Petasaria heterolepis


Classification: non_cocco -> Haptophytes -> Prymnesiales -> Prymnesiaceae -> Petasaria -> Petasaria heterolepis
Sister taxa: P. heterolepis, P. protruberans,

Taxonomy:

Citation: Petasaria heterolepis Moestrup 1979
Rank: Species
Basionym: Petasaria heterolepis Moestrup 1979

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 peri-phery. 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.

Type images:

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 stage). Data source: [JRY]

References:

Jordan, R. W. et al. (2016). Observations on the morphological diversity and distribution of two siliceous nannoplankton genera, Hyalolithus and Petasaria. Micropaleontology. 61(6): 439-455. gs

Moestrup, Ø. (1979). Identification by electron microscopy of marine nanoplankton from New Zealand, including the description of four new species. New Zealand. Journal of Botany. 17: 61-95. gs


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Petasaria heterolepis compiled by Jeremy R. Young viewed: 21-9-2019

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