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Nannoceratopsis reticulata
Nannoceratopsis reticulata Mantle, 2005, p.260,262, pl.4, figs.1–9.
Holotype: Mantle, 2005, pl.4, figs.1–3.
Age: Callovian–early Oxfordian.
Original description (Mantle, 2005):
Nannoceratopsis reticulata sp. nov. ( Plate IV, 1–9).
Holotype and type locality: Challis 11 ST2 well, sidewall core at 1842 m, Single grain mount, EF L47/0. CPC no. 38828 ( Plate IV, 1–3).
Etymology: Latin, reticulatus (netlike); with reference to the netlike ectophragm.
Diagnosis: Cysts proximate, triangular to subtriangular in laterally compressed orientation, with two antapical horns of equal length. Narrow neck-like paracingulum separating minute epicyst from large hypocyst. Dorsal and ventral margins convex, antapical margin concave. Cryptotabulate. Broad sagittal band usually present. Archeopyle cingular. Autophragm surmounted by coarsely reticulate ectophragm. Antapical horns commonly exhibiting distal cavation.
Description: A proximate, laterally compressed cyst, with a triangular to rounded subtriangular outline, possessing two antapical horns separated by a deep concavity. The rounded subtriangular outline is due to slightly convex ventral and dorsal margins. The maximum width of the cyst is variably attained close to the tips of the antapical horns or midway between tip and paracingulum. The antapical horns are typically pointed distally, but may be somewhat rounded and occasionally curved inward; antapical horns usually of equal length but very occasionally the ventral horn is shorter than the dorsal horn. Minute epicyst and large hypocyst connected by well-developed, deeply depressed paracingulum bordered by thickened ridges. The paracingulum is ca. twice the width of the epicyst. The archeopyle is formed by the loss of one or more cingular paraplates. A longitudinal furrow is occasionally distinguishable in the apical portion of the sagittal band on the ventral side. The cyst is thickened around the sagittal area, producing, in lateral view, conspicuous ridges rimming the hypocyst. The autophragm is characteristically surmounted by a comprehensively reticulate ectophragm; the lumen width varies from 0.5 to 3 μm and is often broadest across the centre of the large H2 and H3 paraplates. A small distal cavation is commonly developed at the ends of the antapical horns.
Dimensions (based on 22 specimens): Overall length of cyst, 67 (98) 107 μm; maximum width of cyst, 44 (55) 78 μm; thickness of cyst wall, 1 (2) 3 μm; paracingulum width, 2 (3) 5 μm; mean width of lumina, 0.5 (1) 3 μm.
Holotype: Overall length of cyst, 103 μm; maximum width of cyst, 63 μm; thickness of cyst wall, 2–3 μm; paracingulum width, 4 μm; mean width of lumina, 1–2 μm.
Comparison: Nannoceratopsis reticulata sp. nov. and N. evae Prauss, 1989 differ from all other species of the genus in having a coarsely reticulate ectophragm. However, the weakly developed or absent antapical horns and short, poorly defined epicyst of N. evae readily distinguish this species. Nannoceratopsis reticulata is broadly similar in overall size and morphology to N. pellucida Deflandre, 1939 emend. Evitt, 1961, but differs in featuring a coarsely reticulate ectophragm, thickened sagittal band, and slightly larger size. Nannoceratopsis radiata Kumar, 1986 is considerably larger than N. reticulata and, furthermore, is always widest at the tips of the antapical horns and has an areolate to finely reticulate autophragm. Nannoceratopsis spiculata Stover, 1966 is similarly cavate at the distal terminations of the antapical horns, but in contrast to N. reticulata, has a more rounded lateral outline and areolate or scabrate autophragm. Nannoceratopsis raunsgardii Poulsen, 1996 possesses only very short antapical horns with a shallow concavity between them. Nannoceratopsis reticulata is distinguished from all other members of the genus by having two equal antapical horns.
Holotype: Mantle, 2005, pl.4, figs.1–3.
Age: Callovian–early Oxfordian.
Original description (Mantle, 2005):
Nannoceratopsis reticulata sp. nov. ( Plate IV, 1–9).
Holotype and type locality: Challis 11 ST2 well, sidewall core at 1842 m, Single grain mount, EF L47/0. CPC no. 38828 ( Plate IV, 1–3).
Etymology: Latin, reticulatus (netlike); with reference to the netlike ectophragm.
Diagnosis: Cysts proximate, triangular to subtriangular in laterally compressed orientation, with two antapical horns of equal length. Narrow neck-like paracingulum separating minute epicyst from large hypocyst. Dorsal and ventral margins convex, antapical margin concave. Cryptotabulate. Broad sagittal band usually present. Archeopyle cingular. Autophragm surmounted by coarsely reticulate ectophragm. Antapical horns commonly exhibiting distal cavation.
Description: A proximate, laterally compressed cyst, with a triangular to rounded subtriangular outline, possessing two antapical horns separated by a deep concavity. The rounded subtriangular outline is due to slightly convex ventral and dorsal margins. The maximum width of the cyst is variably attained close to the tips of the antapical horns or midway between tip and paracingulum. The antapical horns are typically pointed distally, but may be somewhat rounded and occasionally curved inward; antapical horns usually of equal length but very occasionally the ventral horn is shorter than the dorsal horn. Minute epicyst and large hypocyst connected by well-developed, deeply depressed paracingulum bordered by thickened ridges. The paracingulum is ca. twice the width of the epicyst. The archeopyle is formed by the loss of one or more cingular paraplates. A longitudinal furrow is occasionally distinguishable in the apical portion of the sagittal band on the ventral side. The cyst is thickened around the sagittal area, producing, in lateral view, conspicuous ridges rimming the hypocyst. The autophragm is characteristically surmounted by a comprehensively reticulate ectophragm; the lumen width varies from 0.5 to 3 μm and is often broadest across the centre of the large H2 and H3 paraplates. A small distal cavation is commonly developed at the ends of the antapical horns.
Dimensions (based on 22 specimens): Overall length of cyst, 67 (98) 107 μm; maximum width of cyst, 44 (55) 78 μm; thickness of cyst wall, 1 (2) 3 μm; paracingulum width, 2 (3) 5 μm; mean width of lumina, 0.5 (1) 3 μm.
Holotype: Overall length of cyst, 103 μm; maximum width of cyst, 63 μm; thickness of cyst wall, 2–3 μm; paracingulum width, 4 μm; mean width of lumina, 1–2 μm.
Comparison: Nannoceratopsis reticulata sp. nov. and N. evae Prauss, 1989 differ from all other species of the genus in having a coarsely reticulate ectophragm. However, the weakly developed or absent antapical horns and short, poorly defined epicyst of N. evae readily distinguish this species. Nannoceratopsis reticulata is broadly similar in overall size and morphology to N. pellucida Deflandre, 1939 emend. Evitt, 1961, but differs in featuring a coarsely reticulate ectophragm, thickened sagittal band, and slightly larger size. Nannoceratopsis radiata Kumar, 1986 is considerably larger than N. reticulata and, furthermore, is always widest at the tips of the antapical horns and has an areolate to finely reticulate autophragm. Nannoceratopsis spiculata Stover, 1966 is similarly cavate at the distal terminations of the antapical horns, but in contrast to N. reticulata, has a more rounded lateral outline and areolate or scabrate autophragm. Nannoceratopsis raunsgardii Poulsen, 1996 possesses only very short antapical horns with a shallow concavity between them. Nannoceratopsis reticulata is distinguished from all other members of the genus by having two equal antapical horns.