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Pareodinia robusta
Pareodinia robusta Wiggins, 1975, p.105, pl.3, figs.1–4.
Originally (and now) Pareodinia, subsequently Pareodinia?. Questionable assignment: Below (1990, p.65–66) as a "nomen dubium" — however, Poulsen (1996, p.62) retained the species in Pareodinia without question.
Taxonomic senior synonym: Pareodinia (now Evansia) alaskensis, according to Below (1990, p.72) — however, Poulsen (1996, p.62) retained Pareodinia robusta.
Holotype: Wiggins, 1975, pl.3, fig.1.
Age: Late Jurassic.
Original diagnosis: Wiggins, 1975, p. 105
Proximate fossil cysts, ambitus elongate ovoidal. Epitract and hypotract appear approximately equal, with little or no girdle representation. Cyst exhibits a distinct apical horn and a broadly rounded antapex. Reflected tabulation, other than the archeopyle outline and operculum, not noted. Archeopyle intercalary and Type 2I. Cyst wall granulate to verrucose, with intensity strongest at the poles. Apicular structure present in the form of a short, rod-like thickening.
Dimensions:
Holotype, 48 X 103 µm, paratypes average 44 X 104 µm.
Affinities:
Wiggins, 1975, p. 105: This species also resembles Pareodinia kondratjevi. However, the consistently short apical horn on P. robusta and the ornamentation intensity differential between the poles and median body region of the cyst separates these species.
Poulsen, 1996, p. 62-63
Pareodinia robusta Wiggins 1975
Pl. 5, Figs. 9-11
Remarks. A consistently short apical horn and the difference in intensity of the ornament between the poles and the median cyst body region separates P. robusta from Imbatodinium kondratjevii (Wiggins, 1975). Pareodinia robusta has a broadly rounded antapex (Wiggins, 1975). The cyst shape of both P. robusta and I. kondratjevii is elongate oval (Wiggins, 1975; Lentin and Vozzhennikova, 1990). The archeopyle is type 2I in both species, but Imbatodinium has a unidenilate archeopyle (see p. and Lentin and Vozzhennikova, 1990, p. 87).
The length of P. robusta is slightly more than 100 µm in the type material (Wiggins, 1975). Specimens of I. kondratjevii have a length of 81-108 µm (Vozzhennikova, 1971). Stevens and Helby (1987, p. 182) described Australian specimens of P. robusta which have a longer apical horn (9-40 µm), but in all other diagnostic features conform to the original description. They believed that apical horn length is not particularly diagnostic. Imbatodinium kondratjevii has a distinct deep paracingulum (Vozzhennikova, 1971; Lentin and Vozzhennikova, 1990). However, some of the specimens figured by Vozzhennikova (1971, e.g. pl. 11, figs. 1a, 2a, 2b), and Lentin and Vozzhennikova (1990, pl. 11, fig. 4) do not show this feature clearly.
Pending further re-examination of the type and other material, P. robusta is retained herein, differentiated from I. kondratjevii primarily on the basis of differences in the archeopyle formation; P. robusta has a type 2I archeopyle, with involvement of one five sided and one six sided paraplate, whereas the type 2I archeopyle of I. kondratjevii involves one six sided and one seven sided paraplate (Lentin and Vozzhennikova, 1990). Both species have a granulate to verrucate autophragm, the ornamentation increasing in size and density towards the hypocyst, and an apical horn with an apicular structure. Pareodinia robusta has, however, no indication of a paracingulum. Polish specimens of P. robusta are found in the same samples as l. kondratjevii. Pareodinia robusta species may be difficult to identify conclusively; often two small antapical lobes are present, or the numbers of sides in the archeopyle opening are only rarely completely distinct, or the apical horn may be lost due to breakage. The presence or absence of small antapical lobes is not regarded as particularly diagnostic. Development of more definite antapical horns is not seen in the Polish specimens of P. trobusta.
Recorded occurrences.
Poland: Tenuicostata- Scythicus Zones.
Originally (and now) Pareodinia, subsequently Pareodinia?. Questionable assignment: Below (1990, p.65–66) as a "nomen dubium" — however, Poulsen (1996, p.62) retained the species in Pareodinia without question.
Taxonomic senior synonym: Pareodinia (now Evansia) alaskensis, according to Below (1990, p.72) — however, Poulsen (1996, p.62) retained Pareodinia robusta.
Holotype: Wiggins, 1975, pl.3, fig.1.
Age: Late Jurassic.
Original diagnosis: Wiggins, 1975, p. 105
Proximate fossil cysts, ambitus elongate ovoidal. Epitract and hypotract appear approximately equal, with little or no girdle representation. Cyst exhibits a distinct apical horn and a broadly rounded antapex. Reflected tabulation, other than the archeopyle outline and operculum, not noted. Archeopyle intercalary and Type 2I. Cyst wall granulate to verrucose, with intensity strongest at the poles. Apicular structure present in the form of a short, rod-like thickening.
Dimensions:
Holotype, 48 X 103 µm, paratypes average 44 X 104 µm.
Affinities:
Wiggins, 1975, p. 105: This species also resembles Pareodinia kondratjevi. However, the consistently short apical horn on P. robusta and the ornamentation intensity differential between the poles and median body region of the cyst separates these species.
Poulsen, 1996, p. 62-63
Pareodinia robusta Wiggins 1975
Pl. 5, Figs. 9-11
Remarks. A consistently short apical horn and the difference in intensity of the ornament between the poles and the median cyst body region separates P. robusta from Imbatodinium kondratjevii (Wiggins, 1975). Pareodinia robusta has a broadly rounded antapex (Wiggins, 1975). The cyst shape of both P. robusta and I. kondratjevii is elongate oval (Wiggins, 1975; Lentin and Vozzhennikova, 1990). The archeopyle is type 2I in both species, but Imbatodinium has a unidenilate archeopyle (see p. and Lentin and Vozzhennikova, 1990, p. 87).
The length of P. robusta is slightly more than 100 µm in the type material (Wiggins, 1975). Specimens of I. kondratjevii have a length of 81-108 µm (Vozzhennikova, 1971). Stevens and Helby (1987, p. 182) described Australian specimens of P. robusta which have a longer apical horn (9-40 µm), but in all other diagnostic features conform to the original description. They believed that apical horn length is not particularly diagnostic. Imbatodinium kondratjevii has a distinct deep paracingulum (Vozzhennikova, 1971; Lentin and Vozzhennikova, 1990). However, some of the specimens figured by Vozzhennikova (1971, e.g. pl. 11, figs. 1a, 2a, 2b), and Lentin and Vozzhennikova (1990, pl. 11, fig. 4) do not show this feature clearly.
Pending further re-examination of the type and other material, P. robusta is retained herein, differentiated from I. kondratjevii primarily on the basis of differences in the archeopyle formation; P. robusta has a type 2I archeopyle, with involvement of one five sided and one six sided paraplate, whereas the type 2I archeopyle of I. kondratjevii involves one six sided and one seven sided paraplate (Lentin and Vozzhennikova, 1990). Both species have a granulate to verrucate autophragm, the ornamentation increasing in size and density towards the hypocyst, and an apical horn with an apicular structure. Pareodinia robusta has, however, no indication of a paracingulum. Polish specimens of P. robusta are found in the same samples as l. kondratjevii. Pareodinia robusta species may be difficult to identify conclusively; often two small antapical lobes are present, or the numbers of sides in the archeopyle opening are only rarely completely distinct, or the apical horn may be lost due to breakage. The presence or absence of small antapical lobes is not regarded as particularly diagnostic. Development of more definite antapical horns is not seen in the Polish specimens of P. trobusta.
Recorded occurrences.
Poland: Tenuicostata- Scythicus Zones.