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Stoveracysta conerae
Stoveracysta conerae Biffi and Manum, 1988
Holotype: Biffi and Manum, 1988, pl. 6, fig. 10-11
Locus typicus: Bisciaro Fm., Monte Conero section, Marche region, Italy
Stratum typicum: Early Miocene
Original description: Biffi and Manum, 1988, p. 192-194.
Diagnosis: Proximate cyst of subsphaerical shape; autophragm with smooth to slightly granular surface. Penitabular septa, 2-4 µ high, which reveal a gonyaulacacean paratabulation with formula 4", 6"", ?6c, 6""", 1p, 1"""", ?4s. Apical archeopyle (type tA), with simple operculum, normally detached. Outline of paraplate 6"" roughly quadrangular; paraplate 1""", very small and poorly delimited (pl. 6, fig. 15); paraplate 1"""" sexiform.
Dimensions: Holotype: overall cyst breadth 70 µm; archeopyle breadth 50 µm; length of septa 2-3 µm. Mean values (bracketed) and extremes (n = 20): overall cyst breadth 60(69)78 µm; archeopyle breadth 40(46)60 µm; height of septa 2-4 µm.
Description (annotated): Penitabular septa of variable prominence create confusing optical images. They tend to bend towards the parasutures with their crests forming distinctive double contour along archeopyle and operculum outlines (pl. 6, fig. 15-16), else along parasutures they are often seen as distinct lines running parallel to septa bases; in optical section, as observed along the cyst periphery, septa may appear to produce a dome-like structure over the parasutures. The autophragm appears to be composed of an unstructured basal layer supporting densely spaced granules to columella-like elements producing a corrugate surface texture of variable prominence; some specimens are almost smooth (pl. 6, fig. 15). In the well preserved specimens the paratabulation is distinct except for vaguely defined cingular paraplates, the formula being: 4", 6"", (?)6c, 6""", 1p, 1"""", (?)4s. The four apicals are of different size (1" < 4" < 3" < 2") and a very small preapical area may be present. The sulcal area shows rudimentary parasutures, but in favourable conditions the as, rs, 1s, and ps paraplates can be recognized (pl. 6, fig. 15). Paraplate 6"" is subquadrangular, the postcingular 1""" is very small and quite indistinct, intimately associated to the cingulum. The antapical 1"""" appears to be sexiform (pl. 6, fig. 11). The archeopyle is apical, type tA with deep accessory sutures and sulcal notch.
Affinities:
Biffi and Manum, 1988, p. 194: Clowes (1985) established the genus Stoveracysta to accomodate forms superficially resembling Alicocysta Stover and Evitt (1978), but differing in having a sexiform rather than a quinqueform hypocystal plate topology. Stoveracysta conerae n. sp. differs from S. kakanuiensis Clowes, 1985 in being subsphaerical to oblate in shape, in having more strongly defined paracingulum, a 6"" paraplate quadrangular rather than triangular. S. conerae resembles S. ornata in its overall shape and paratabulation. A more marked paratabulation, a wider spacing of penitabular septa and a thicker wall characterize S. ornata.
Holotype: Biffi and Manum, 1988, pl. 6, fig. 10-11
Locus typicus: Bisciaro Fm., Monte Conero section, Marche region, Italy
Stratum typicum: Early Miocene
Original description: Biffi and Manum, 1988, p. 192-194.
Diagnosis: Proximate cyst of subsphaerical shape; autophragm with smooth to slightly granular surface. Penitabular septa, 2-4 µ high, which reveal a gonyaulacacean paratabulation with formula 4", 6"", ?6c, 6""", 1p, 1"""", ?4s. Apical archeopyle (type tA), with simple operculum, normally detached. Outline of paraplate 6"" roughly quadrangular; paraplate 1""", very small and poorly delimited (pl. 6, fig. 15); paraplate 1"""" sexiform.
Dimensions: Holotype: overall cyst breadth 70 µm; archeopyle breadth 50 µm; length of septa 2-3 µm. Mean values (bracketed) and extremes (n = 20): overall cyst breadth 60(69)78 µm; archeopyle breadth 40(46)60 µm; height of septa 2-4 µm.
Description (annotated): Penitabular septa of variable prominence create confusing optical images. They tend to bend towards the parasutures with their crests forming distinctive double contour along archeopyle and operculum outlines (pl. 6, fig. 15-16), else along parasutures they are often seen as distinct lines running parallel to septa bases; in optical section, as observed along the cyst periphery, septa may appear to produce a dome-like structure over the parasutures. The autophragm appears to be composed of an unstructured basal layer supporting densely spaced granules to columella-like elements producing a corrugate surface texture of variable prominence; some specimens are almost smooth (pl. 6, fig. 15). In the well preserved specimens the paratabulation is distinct except for vaguely defined cingular paraplates, the formula being: 4", 6"", (?)6c, 6""", 1p, 1"""", (?)4s. The four apicals are of different size (1" < 4" < 3" < 2") and a very small preapical area may be present. The sulcal area shows rudimentary parasutures, but in favourable conditions the as, rs, 1s, and ps paraplates can be recognized (pl. 6, fig. 15). Paraplate 6"" is subquadrangular, the postcingular 1""" is very small and quite indistinct, intimately associated to the cingulum. The antapical 1"""" appears to be sexiform (pl. 6, fig. 11). The archeopyle is apical, type tA with deep accessory sutures and sulcal notch.
Affinities:
Biffi and Manum, 1988, p. 194: Clowes (1985) established the genus Stoveracysta to accomodate forms superficially resembling Alicocysta Stover and Evitt (1978), but differing in having a sexiform rather than a quinqueform hypocystal plate topology. Stoveracysta conerae n. sp. differs from S. kakanuiensis Clowes, 1985 in being subsphaerical to oblate in shape, in having more strongly defined paracingulum, a 6"" paraplate quadrangular rather than triangular. S. conerae resembles S. ornata in its overall shape and paratabulation. A more marked paratabulation, a wider spacing of penitabular septa and a thicker wall characterize S. ornata.