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Rhynchodiniopsis foveata
Rhynchodiniopsis foveata Snape, 1992
Holotype: Snape, 1992, fig.7h (length 112 µm, width 73 µm, apical horn 14 µm long and 8 µm wide at the base)
Locus typicus: Sharp Valley, James Ross Island, Antarctica
Stratum typicum: Middle Tithonian
Diagnosis. Snape, 1992, p. 277
Cyst is proximate, acavate and ovoidal in shape with a perforated apical horn. Paratabulation gonyaulacean indicated by parasutural ornament and penitabular fovea. Kofoidian formula: 4", 6"", ?6c, 6""", 1p,1"""" The archaeopyle is precingular, type P.
Description: Snape, 1992, p. 277
The cyst proximate, acavate and ovoidal in shape with a prominent perforated apical horn, 13-18 µm long. The distal tip of the horn may be accuminate or truncated. The autophragm is ornamented with parasutural ridges that are commonly solid (1-2 µm high) but occasionally grade into ragged septa (up to 6 µm high). The septa may be fenestrate or rarely trabeculate. Penitabular rows of fovea are present and are best developed in the paracingular area. The fovea are commonly 1-3 µm in diameter and up to 1 µm deep. Intratabular areas are otherwise smooth. The archaeopyle is precingular, enlarged type P, with the loss of the 3"" paraplate. The paracingulum is 4-5 µm wide, the pre- and postcingular paraplates are relatively large and the 1"""" paraplate is relatively small.
Dimensions (µm):MinMeanMax
Overall length102116130
Overall width6582107
Apical horn length121618
Specimens measured: 20
Affinities: Snape, 1992, p. 277
R. foveata is distinguished by its large ovoidal ambitus, parasutural features and penitabular ornamentation. The perforated apical horn is the other notable feature of this taxon. R. pennata has a similar ambitus and parasutural features, but lacks the penitabular fovea and is smaller in size. R. cladophora, R. gochtii and R. serrata differ from R. foveata in each having a polygonal ambitus and having short processes ornamenting the parasutures.
R. fimbriata differs by having a polygonal, almost biconical ambitus with fimbriate parasutural ornament.
Holotype: Snape, 1992, fig.7h (length 112 µm, width 73 µm, apical horn 14 µm long and 8 µm wide at the base)
Locus typicus: Sharp Valley, James Ross Island, Antarctica
Stratum typicum: Middle Tithonian
Diagnosis. Snape, 1992, p. 277
Cyst is proximate, acavate and ovoidal in shape with a perforated apical horn. Paratabulation gonyaulacean indicated by parasutural ornament and penitabular fovea. Kofoidian formula: 4", 6"", ?6c, 6""", 1p,1"""" The archaeopyle is precingular, type P.
Description: Snape, 1992, p. 277
The cyst proximate, acavate and ovoidal in shape with a prominent perforated apical horn, 13-18 µm long. The distal tip of the horn may be accuminate or truncated. The autophragm is ornamented with parasutural ridges that are commonly solid (1-2 µm high) but occasionally grade into ragged septa (up to 6 µm high). The septa may be fenestrate or rarely trabeculate. Penitabular rows of fovea are present and are best developed in the paracingular area. The fovea are commonly 1-3 µm in diameter and up to 1 µm deep. Intratabular areas are otherwise smooth. The archaeopyle is precingular, enlarged type P, with the loss of the 3"" paraplate. The paracingulum is 4-5 µm wide, the pre- and postcingular paraplates are relatively large and the 1"""" paraplate is relatively small.
Dimensions (µm):MinMeanMax
Overall length102116130
Overall width6582107
Apical horn length121618
Specimens measured: 20
Affinities: Snape, 1992, p. 277
R. foveata is distinguished by its large ovoidal ambitus, parasutural features and penitabular ornamentation. The perforated apical horn is the other notable feature of this taxon. R. pennata has a similar ambitus and parasutural features, but lacks the penitabular fovea and is smaller in size. R. cladophora, R. gochtii and R. serrata differ from R. foveata in each having a polygonal ambitus and having short processes ornamenting the parasutures.
R. fimbriata differs by having a polygonal, almost biconical ambitus with fimbriate parasutural ornament.