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Phthanoperidinium coreoides

Phthanoperidinium coreoides (Benedek, 1972, p.20, pl.9, figs.4a–c) Lentin and Williams, 1976, p.76. Emendation: Benedek and Sarjeant, 1981, p.328–330, as Phthanoperidinium coreoides.

Originally Hystrichogonyaulax, subsequently (and now) Phthanoperidinium.
Taxonomic senior synonym: Peridinium (now Phthanoperidinium) comatum, according to Stover and Evitt (1978, p.118) — however, Benedek and Sarjeant (1981, p.328–330) retained Phthanoperidinium coreoides.
Taxonomic junior synonym Phthanoperidinium tritonium, according to Fensome et al. (2009, p.54–55), which species had previously been considered a taxonomic junior synonym of Phthanoperidinium comatum by Bujak in Bujak et al. (1980, p.72)

Holotype: Benedek, 1972, pl.9, fig.4a-c; Benedek and Sarjeant, 1981, fig.3, nos.2,4; fig. 5
Paratype: Benedek, 1972
Locus typicus: Tönisberg, Lower Rhine Embayment, Germany
Stratum typicum: Middle Oligocene
Translation Benedek, 1972: LPP

Original dignosis: Benedek, 1972, p.20: Hystrichogonyaulax coreoides
A species of Hystrichgonyaulax with following tabulation formula: 4", ?1a, 6"", 6c, 5-6""", 1p, 0-1(sic), 1"""". The egg-shaped, slightly polyedrical theca is pointed apical. Sutures thickened and ornamented with thin thorns. Transverse furrow slightly indented and spiral. Longitudinal furrow clearly delimited.

Original description: Benedek, 1972, p.20
The small theca is tabulate and has a weakly granulate surface. Sutures better developed with irregular distributed thin, solid thorns. In the apical and antapical regions longer (10 µm/12 µm), distally furcate thorns are developed. Archaeopyle results from the loss of plate 2a or the upper part of plate 3"""(sic). Epitheca elongated, egg-shaped and seperated from the hypotheca by a weakly indented cingulum consisting of 5-6 plates. Hypotheca smaller and more rounded than epitheca.
Dimensions: Capsule length 36-38 µm, capsule breadth c. 26 µm (10 specimens).

Supplemental diagnosis: Benedek and Sarjeant, 1981, p. 328
Cyst proximate, elongate-ovoidal, with a small apical prominence and rounded antapex. Epitract markedly larger than hypotract. Paratabulation: 1-?2pa, 4", 3a, 7", 7c, 5""", 1pv, 2"""". Paraplate boundaries marked by low ridges from which arise well-spaced, rather stiff gonal and intergonal spines of moderate length with evexate, swollen, capitate or very briefly bifurcate tips. Paracingulum broad, moderately laevorotatory: parasulcus broad and short. Surface faintly granulate. Archaeopyle intercalary, formed by loss of a single paraplate (Type 1): archaeopyle index around 0.5; operculum free.

Supplemental description: Benedek and Sarjeant, 1981, p. 328-329
The cyst ambitus is somewhat like that of a Palaeolithic hand-axe, rounded at the posterior end and tapering in a smooth curve to the more pointed anterior end. The apical prominence is very small and may be seen only in favourable orientations. The distribution of spines on the sutures is irregular: many are gonal, some intergonal, but they are lacking from some paraplate junctions and many intergonal positions. Their length varies, being longest near the apex and antapex, shortest on the ventral surface. The phragma appears to be two-layered, sutural ridges and processes arising from the periphragm. Paraplate 1" is unusually large and broad but does not reach to the apex, which is occupied by one or more preapicals. The apical paraplates are small. Of the three anterior intercalary paraplates considered to be present, 2a (lost in archaeopyle formation) is the largest and of shape intermediate between the "standard" and "broad hexa" types of Lentin and Williams (1975). The shape of la was not established with confidence. Paraplate 4" is short and almost square, the other precingulars of fairly uniform size. Seven cingulars may be distinguished, though 1c is very small and 2c and 7c also small.
Paraplate 1""" shows an inbend of its posterior boundary with the parasulcus, suggesting possible descent from forms with a posterior intercalary paraplate: but such a paraplate is here lacking. Paraplates 1""" and 5""" are smaller than the others of the postcingular series and distinctly smaller than most precingulars. Three paraplates are grouped fairly symmetrically about the antapex; all could be regarded as antapicals, but the ventral situation and greater breadth of one allows it to be considered rather as a posterior ventral. Paraplates 1"""" and 2"""" are of closely similar size and shape. A roughly crescentic flagellar mark is visible on the parasulcus, just anterior to the paracingulum, in some specimens (see Fig. 5). In addition, a number of wart-like swellings may be visible on the parasulcus, in particular between the two ends of the paracingulum.
Dimensions: Holotype--length 40 µm, breadth 26 µm, length of spines up to 6 µm. Range of dimensions: Length 36-40 µm, breadth ca. 26 µm, length of processes 6-8 µm. Material: 12 specimens.
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