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Pareodinia brachythelis
Pareodinia brachythelis Fensome, 1979, p.29–31, pl.4, figs.3,5–7; text-figs.11A–E. Emendation: Below, 1990, p.58, as Paraevansia brachythelis.
Now Paraevansia. Originally Pareodinia, subsequently (and now) Paraevansia.
Holotype: Fensome, 1979, pl.4, fig.5, text-fig.11E
Locus typicus: Jameson Land, Greenland
Stratum typicum: Bajocian-Callovian
Diagnosis: Fensome 1979, p.29-30
A species of Pareodinia having a thick cyst wall densely ornamented by coarse granules or verrucae. The cyst is ovoidal with a smoothly rounded outline, and surmounted by a distinct, short mamelon-like apical horn which is often itself surmounted by a rod-like or irregularly shaped solid apicular structure; similar structures may occur elsewhere on the cyst wall, notably at the antapex. The archaeopyle is intercalary, involving the loss of three (occasionally possibly four or more) paraplates. The operculum is compound. The paracingulum is usually only weakly indicated or absent. There is no other indication of a paratabulation.
Dimensions (36 specimens):
length; breadth; apical; horn; apicular struct.
Holotype: 52 µm; 37µm; 5 µm; 2 µm
Paratype: 54 µm; 32 µm; 4 µm; 2 µm
Range: 45(54)66 µm; 31(36)42 µm; 3(6)8 µm; 2(3.5)5 µm
Description: Fensome 1979, p.29-30
The apical horn is of characteristic shape, with a broad base and a usually well rounded distal extremity (exclusive of any apicular structure). The horn is usually distinct from the rest of the cyst; it is variable in length but, in the type material, this does not exceed one sixth of the overall length of the cyst. Rarely the horn may be very short; indeed one specimen superficially resembles a form of Chytoeisphaeridia. The presence of a rod-like or irregularly shaped apicular structure at the distal tip of the apical horn often gives the apex a more pointed or irregular shape. Solid protruberances of irregular outline may rarely occur elsewhere on the cyst surface, especially at the antapex. The paratype appears to possess a pre-apical paraplate on its apical horn differentiated from the rest of the cyst by a more lightly stained portion of the cyst wall; this is ornamented by a scatter of coarse, wart-like verrucae. A pre-apical paraplate was not observed on any other specimen from Jameson Land.
Archaeopyle: large; operculum: compound; it is formed by three or perhaps occasionally four or more anterior intercalary paraplates. Each opercular piece may be attached or detached from the archaeopyle margin; detached opercular pieces often occur within the cavity of the cyst.
Paracingulum: may be faintly indicated by a slight depression in the cyst wall or by folding; similarly a slight depression may indicate the position of the parasulcus. Otherwise, there is no indication of furrows or of a paratabulation on the cyst surface except at the archaeopyle and rarely at the apex. None of the specimens observed possesses a kalyptra.
Affinities:
Fensome 1979, p.31: Pareodinia brachythelis resembles P. alaskensis Wiggins, 1975 in its possession of a coarse ornamentation, a thick cyst wall, a short apical horn and usually a type 3I archaeopyle. However, P. alaskensis is larger, more elongate and more spindle-shaped than P. brachythelis, which has an inflated, regularly rounded appearance.
P. minuta Wiggins, 1975 is of similar size to P. brachythelis and also possesses a coarse surface ornamentation and probably a three-paraplate intercalary archaeopyle. However, like P. alaskensis, P. minuta is spindle-shaped and not rounded in outline; it also differs from P. brachythelis in the morphology of its apical horn. The ornamentation of P. verrucosa (Vozzhennikova, 1967) Wiggins, 1975, and of P. cf. P. verrucosa (herein)is distinctly coarser than that of P. brachythelis. P. verrucosa and P. kondratjevii (Vozzhennikova, 1967) Wiggins, 1975 have much longer apical horns than P. brachythelis. P. robusta Wiggins, 1975 differs from P. brachythelis in its unevenly distributed ornamentation, its elongate shape and its type 2I archaeopyle.
P. brachythelis is closely similar in shape, surface ornamentation, the nature of its archaeopyle and apical morphology to Pareodinia sp. B of Wiggins, 1975; indeed, Wiggins" specimen is probably attributable to P. brachythelis. Wiggins (1975, p.108) notes that a pre-apical series occurs at the apex of this specimen. This appears to be analogous to the pre-apical paraplate observed on the paratype of P. brachythelis.
Now Paraevansia. Originally Pareodinia, subsequently (and now) Paraevansia.
Holotype: Fensome, 1979, pl.4, fig.5, text-fig.11E
Locus typicus: Jameson Land, Greenland
Stratum typicum: Bajocian-Callovian
Diagnosis: Fensome 1979, p.29-30
A species of Pareodinia having a thick cyst wall densely ornamented by coarse granules or verrucae. The cyst is ovoidal with a smoothly rounded outline, and surmounted by a distinct, short mamelon-like apical horn which is often itself surmounted by a rod-like or irregularly shaped solid apicular structure; similar structures may occur elsewhere on the cyst wall, notably at the antapex. The archaeopyle is intercalary, involving the loss of three (occasionally possibly four or more) paraplates. The operculum is compound. The paracingulum is usually only weakly indicated or absent. There is no other indication of a paratabulation.
Dimensions (36 specimens):
length; breadth; apical; horn; apicular struct.
Holotype: 52 µm; 37µm; 5 µm; 2 µm
Paratype: 54 µm; 32 µm; 4 µm; 2 µm
Range: 45(54)66 µm; 31(36)42 µm; 3(6)8 µm; 2(3.5)5 µm
Description: Fensome 1979, p.29-30
The apical horn is of characteristic shape, with a broad base and a usually well rounded distal extremity (exclusive of any apicular structure). The horn is usually distinct from the rest of the cyst; it is variable in length but, in the type material, this does not exceed one sixth of the overall length of the cyst. Rarely the horn may be very short; indeed one specimen superficially resembles a form of Chytoeisphaeridia. The presence of a rod-like or irregularly shaped apicular structure at the distal tip of the apical horn often gives the apex a more pointed or irregular shape. Solid protruberances of irregular outline may rarely occur elsewhere on the cyst surface, especially at the antapex. The paratype appears to possess a pre-apical paraplate on its apical horn differentiated from the rest of the cyst by a more lightly stained portion of the cyst wall; this is ornamented by a scatter of coarse, wart-like verrucae. A pre-apical paraplate was not observed on any other specimen from Jameson Land.
Archaeopyle: large; operculum: compound; it is formed by three or perhaps occasionally four or more anterior intercalary paraplates. Each opercular piece may be attached or detached from the archaeopyle margin; detached opercular pieces often occur within the cavity of the cyst.
Paracingulum: may be faintly indicated by a slight depression in the cyst wall or by folding; similarly a slight depression may indicate the position of the parasulcus. Otherwise, there is no indication of furrows or of a paratabulation on the cyst surface except at the archaeopyle and rarely at the apex. None of the specimens observed possesses a kalyptra.
Affinities:
Fensome 1979, p.31: Pareodinia brachythelis resembles P. alaskensis Wiggins, 1975 in its possession of a coarse ornamentation, a thick cyst wall, a short apical horn and usually a type 3I archaeopyle. However, P. alaskensis is larger, more elongate and more spindle-shaped than P. brachythelis, which has an inflated, regularly rounded appearance.
P. minuta Wiggins, 1975 is of similar size to P. brachythelis and also possesses a coarse surface ornamentation and probably a three-paraplate intercalary archaeopyle. However, like P. alaskensis, P. minuta is spindle-shaped and not rounded in outline; it also differs from P. brachythelis in the morphology of its apical horn. The ornamentation of P. verrucosa (Vozzhennikova, 1967) Wiggins, 1975, and of P. cf. P. verrucosa (herein)is distinctly coarser than that of P. brachythelis. P. verrucosa and P. kondratjevii (Vozzhennikova, 1967) Wiggins, 1975 have much longer apical horns than P. brachythelis. P. robusta Wiggins, 1975 differs from P. brachythelis in its unevenly distributed ornamentation, its elongate shape and its type 2I archaeopyle.
P. brachythelis is closely similar in shape, surface ornamentation, the nature of its archaeopyle and apical morphology to Pareodinia sp. B of Wiggins, 1975; indeed, Wiggins" specimen is probably attributable to P. brachythelis. Wiggins (1975, p.108) notes that a pre-apical series occurs at the apex of this specimen. This appears to be analogous to the pre-apical paraplate observed on the paratype of P. brachythelis.