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Pterocysta cruciformis
Pterocysta cruciformis Rochon in Rochon et al., 2003, p.97–98,100,102, pl.1, figs.1–9; pl.2, figs.1–9; text-fig.2A–D.
Holotype: Rochon et al., 2003, pl.1, figs.1,4.
Age: late Pleistocene.
Original description (Rochon et al., 2003):
Pterocysta cruciformis Rochon (Plate 1,1-9; Plate 2, 1-9)
Holotype. Slide M98-4,130 cm. Plate 1, figures 1 and 4, from Late Pleistocene, southwest Black Sea, 41C 27.26'N, 29° 16.01'E, core M98-4, 130 cm.
Repository. Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, Dartmouth, Nova Scotia.
Derivation of name. From Latin, crux (cross), and formis (shape); with reference to the cruciform shape of the endocyst.
Diagnosis. A camocavate gonyaulacacean cyst with a Stype sulcal tabulation characterized by the separation of the endophragm and periphragm in the sulcal area, forming a wing-like fenestrate structure covering a pericoel on the ventral side. The endocyst is cruciform, with a cross shape with rounded extremities in dorso-ventral view and moderate dorso-ventral compression. The archeopyle is precingular, type P, with attached or free operculum. The wall surface ornamentation varies from shagreenate to verrucate.
Description. In equatorial view, the endocyst has a distinctive rounded cruciform shape and is moderately dorso-ventrally compressed. The epi- and hypocyst are notably expanded in the paracingular area, above and below which the endocyst sides are strongly concave, particularly on the epicyst. In lateral and polar views, the endocyst is oval to rectangular in shape, with the paracingular area being slightly broader than the apices. The epicyst and hypocyst are similar in size and the apices are rounded. The periphragm and endophragm vary from shagreenate to verrucate. On some specimens, the dorsal wall is ornamented with scattered minute projections about 1 urn high. The paratabulation is of gonyaulacacean type: 4', 6", 6c, 6s, 6'", lp, 1"". It is expressed on the endocyst by the precingular 3" archeopyle and in apical and antapical regions by low (1-3 microns high) ridges that gradually disappear toward the paracingular area (Text-fig. 2). The plates marked by * (Text-fig. 2) are interpreted as being homologues of a standard gonyaulacacean pattern (Fensome et al., 1993). The archeopyle is iso-deltaform camerate, and rounded anteriorly at the contact with plates *2' and *3'. The archeopyle is simple and usually free, but a few specimens had an attached operculum. The paracingular area does not show any sign of tabulation. The crest, which is narrow (ca. 1/2 to 2/3 of the body width) and fenestrate, is formed by the separation of the periphragm and endophragm in the sulcal area on the ventral surface, forming a wide cavity, or pericoel, that extends from apex to antapex. It is attached to the endocyst at the apex, antapex, and on both sides of the paracingular area, probably at the junction between plates lc-2c, and 5c-6c (Text-fig. 2). The sulcal paratabulation, together with plates *V, *4', 1", 6", lc, 6c, and lp are expressed on the crest by raised ridges and perforations of the periphragm. On some specimens the plates * 1' and *4' seem to be fused.
Dimensions. Holotype - overall height = 51 µm; endocyst width=48 um; crest width=26 µm; endocyst: crest-width ratio = 0.5. Observed average and extreme dimensions - overall height: 37(46)59 µm (39 specimens measured); endocyst width: 36(41)48 µm (21 specimens measured); endocyst dorso-ventral thickness: 26(29)34 µm (21 specimens measured); dorso-ventral width (including periphragm): 45(54)66 µm (22 specimens measured); crest width: 20(26)32 µm (3 specimens measured); endocyst- crest width ratio = 0.60.
Stratigraphic range. Late Pleistocene (Marine Isotopic Stages 3-2).
Holotype: Rochon et al., 2003, pl.1, figs.1,4.
Age: late Pleistocene.
Original description (Rochon et al., 2003):
Pterocysta cruciformis Rochon (Plate 1,1-9; Plate 2, 1-9)
Holotype. Slide M98-4,130 cm. Plate 1, figures 1 and 4, from Late Pleistocene, southwest Black Sea, 41C 27.26'N, 29° 16.01'E, core M98-4, 130 cm.
Repository. Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, Dartmouth, Nova Scotia.
Derivation of name. From Latin, crux (cross), and formis (shape); with reference to the cruciform shape of the endocyst.
Diagnosis. A camocavate gonyaulacacean cyst with a Stype sulcal tabulation characterized by the separation of the endophragm and periphragm in the sulcal area, forming a wing-like fenestrate structure covering a pericoel on the ventral side. The endocyst is cruciform, with a cross shape with rounded extremities in dorso-ventral view and moderate dorso-ventral compression. The archeopyle is precingular, type P, with attached or free operculum. The wall surface ornamentation varies from shagreenate to verrucate.
Description. In equatorial view, the endocyst has a distinctive rounded cruciform shape and is moderately dorso-ventrally compressed. The epi- and hypocyst are notably expanded in the paracingular area, above and below which the endocyst sides are strongly concave, particularly on the epicyst. In lateral and polar views, the endocyst is oval to rectangular in shape, with the paracingular area being slightly broader than the apices. The epicyst and hypocyst are similar in size and the apices are rounded. The periphragm and endophragm vary from shagreenate to verrucate. On some specimens, the dorsal wall is ornamented with scattered minute projections about 1 urn high. The paratabulation is of gonyaulacacean type: 4', 6", 6c, 6s, 6'", lp, 1"". It is expressed on the endocyst by the precingular 3" archeopyle and in apical and antapical regions by low (1-3 microns high) ridges that gradually disappear toward the paracingular area (Text-fig. 2). The plates marked by * (Text-fig. 2) are interpreted as being homologues of a standard gonyaulacacean pattern (Fensome et al., 1993). The archeopyle is iso-deltaform camerate, and rounded anteriorly at the contact with plates *2' and *3'. The archeopyle is simple and usually free, but a few specimens had an attached operculum. The paracingular area does not show any sign of tabulation. The crest, which is narrow (ca. 1/2 to 2/3 of the body width) and fenestrate, is formed by the separation of the periphragm and endophragm in the sulcal area on the ventral surface, forming a wide cavity, or pericoel, that extends from apex to antapex. It is attached to the endocyst at the apex, antapex, and on both sides of the paracingular area, probably at the junction between plates lc-2c, and 5c-6c (Text-fig. 2). The sulcal paratabulation, together with plates *V, *4', 1", 6", lc, 6c, and lp are expressed on the crest by raised ridges and perforations of the periphragm. On some specimens the plates * 1' and *4' seem to be fused.
Dimensions. Holotype - overall height = 51 µm; endocyst width=48 um; crest width=26 µm; endocyst: crest-width ratio = 0.5. Observed average and extreme dimensions - overall height: 37(46)59 µm (39 specimens measured); endocyst width: 36(41)48 µm (21 specimens measured); endocyst dorso-ventral thickness: 26(29)34 µm (21 specimens measured); dorso-ventral width (including periphragm): 45(54)66 µm (22 specimens measured); crest width: 20(26)32 µm (3 specimens measured); endocyst- crest width ratio = 0.60.
Stratigraphic range. Late Pleistocene (Marine Isotopic Stages 3-2).