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Alterbidinium earnleyense
From Fensome et al., 2019:
AIterbidinium earnleyense, (Islam, 1983b, p.336, pl.1, figs.10–11) Lentin and Williams, 1985, p.14.
Holotype: Islam, 1983b, pl.1, fig.10.
Originally Alterbia? (generic name illegitimate), subsequently (and now) Alterbidinium?.
Questionable assignment: Lentin and Williams (1985, p.14).
Age: Middle Eocene.
Locus typicus: Hampshire Basin, S England
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Original description as ?AIterbia earnleyense: [Islam, 1983, p. 336]:
Diagnosis:
Pericyst dorsoventrally compressed peridinioid with short, conical apical horn having pointed or rounded tip, broadening proximally to merge with epipericyst ambitus, and only left antapical horn which is similarly conical, broad-based and equally long with pointed or rounded tip; right antapical horn, if present, vestigial; endocyst oblate and subspherical; both phragma thin and chagrinate, sometimes wrinkled; proximate and cornucavate to narrowly bicavate; folding in periphragm always defining paracingulum, which is slightly helicoidal and sometimes sunken; parasulcus sometimes indicated by slight depression;
archeopyle intercalary type lll with standard hexa style, operculum attached or free; epipericoel may or may not be in communication to exterior.
Dimensions:
Holotype: pericyst 54 x 44 µm, endocyst 37 x 43 µm, archeopyle index 0.51.
Range: pericyst length 58(53)49 µm, breadth 52(48)44 µm; endocyst length 48(39)31 µm, breadth 51(47)43 µm; archeopyle index 0.59(0.52)0.49 (5 specimens). Specimens measured: 11.
Affinities:
The remarks made on the generic assignment of A. bicellula are also relevant to this species. The holotype of A. earnleyense (pl. 1, fig. 10) vaguely indicates the presence of accessory sutures adjacent to the archeopyle, implying possible involvement of other adjacent paraplates in archeopyle formation. But this could not be conclusively determined, as most of the specimens did not indicate an archeopyle.
Alterbia earnleyense differs from ?A. bicellula in possessing one antapical horn. This distinction may possibly be argued to be infraspecific, but the two species are distinguished because of their relative stratigraphic significance. Alterbia earnleyense is stratigraphically younger.
AIterbidinium earnleyense, (Islam, 1983b, p.336, pl.1, figs.10–11) Lentin and Williams, 1985, p.14.
Holotype: Islam, 1983b, pl.1, fig.10.
Originally Alterbia? (generic name illegitimate), subsequently (and now) Alterbidinium?.
Questionable assignment: Lentin and Williams (1985, p.14).
Age: Middle Eocene.
Locus typicus: Hampshire Basin, S England
---------------------------------------------------------------------------------------------------
Original description as ?AIterbia earnleyense: [Islam, 1983, p. 336]:
Diagnosis:
Pericyst dorsoventrally compressed peridinioid with short, conical apical horn having pointed or rounded tip, broadening proximally to merge with epipericyst ambitus, and only left antapical horn which is similarly conical, broad-based and equally long with pointed or rounded tip; right antapical horn, if present, vestigial; endocyst oblate and subspherical; both phragma thin and chagrinate, sometimes wrinkled; proximate and cornucavate to narrowly bicavate; folding in periphragm always defining paracingulum, which is slightly helicoidal and sometimes sunken; parasulcus sometimes indicated by slight depression;
archeopyle intercalary type lll with standard hexa style, operculum attached or free; epipericoel may or may not be in communication to exterior.
Dimensions:
Holotype: pericyst 54 x 44 µm, endocyst 37 x 43 µm, archeopyle index 0.51.
Range: pericyst length 58(53)49 µm, breadth 52(48)44 µm; endocyst length 48(39)31 µm, breadth 51(47)43 µm; archeopyle index 0.59(0.52)0.49 (5 specimens). Specimens measured: 11.
Affinities:
The remarks made on the generic assignment of A. bicellula are also relevant to this species. The holotype of A. earnleyense (pl. 1, fig. 10) vaguely indicates the presence of accessory sutures adjacent to the archeopyle, implying possible involvement of other adjacent paraplates in archeopyle formation. But this could not be conclusively determined, as most of the specimens did not indicate an archeopyle.
Alterbia earnleyense differs from ?A. bicellula in possessing one antapical horn. This distinction may possibly be argued to be infraspecific, but the two species are distinguished because of their relative stratigraphic significance. Alterbia earnleyense is stratigraphically younger.