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Nyktericysta tripenta
Nyktericysta tripenta (Bint, 1986, p.158,160, pl.6, figs.9–17; pl.7, fig.8; text-figs.6A–B) Fensome et al., 2009, p.46. Holotype: Bint, 1986, pl.6, figs.10,14–16; text-fig.6B; Fensome et al., 1995, figs.1,4,7 — p.1851. Originally Balmula, subsequently (and now) Nyktericysta. Age: late Albian.
Original description: Bint, 1986, p.158, 160
Large, dorso-ventrally compressed ceratioid cysts with an apical and two subequal antapical horns, and with or without two lateral horns. Lateral horns are postcingular and are long and conspicuous on some specimens but completely absent on others. All horns are long, narrow, and distally rounded. Apical horn may bear a solid projection at its tip. Left antapical horn may be slightly longer than right.
Cysts two-layered. Endocyst has three or five prominent horns: apical, two antapicals, and two laterals which may or may not be present. Periphragm lies close to endophragm, but usually separated from it, and comes to an irregular termination toward ends of horns so that the distal portion of the horn is formed by endophragm only. Both walls are smooth and thin.
Paratabulation not expressed. Cingulum is indicated by faint transverse lines, sulcus is not indicated. Archeopyle apical, suture is weakly angular or ragged, operculum usually remains in place and thus is probably adnate.
Size. Length of complete five-horned specimen 120(130)148 µm, 8 measurements; length of two specimens with operculum broken away 82 and 90 µm; width excluding lateral horns 45(53)59 µm; 10 specimens measured. Length of complete threehorned specimen 118(133)177 µm, 9 measurements; length of one specimen with operculum broken away 88 µm; width 41(48)56 µm; 10 specimens measured. Approximate lengths of horns: apical 37-80 µm, lateral 20-35 µm, antapical 25-45 µm.
Remarks. Two distinct morphotypes of Balmula tripenta can be recognized based on the presence or absence of the lateral horns. The first type (Plate 6, figs. 9, 10, 13) possesses two long, narrow, distally rounded postcingular horns formed by the endocyst with the periphragm terminating before the ends of the horns. These specimens have a total of five horns, one apical, two lateral, and two antapical. The second morphotype (Plate 6, figs. 11, 12) completely lacks the two lateral horns and has a total of only three horns--one apical and two antapical-but the distinctive termination of the periphragm near the horn tips clearly marks it as the same species.
Affinities:
Bint, 1986, p.160 The prolongation of the endocyst into long horns with the periphragm terminating before the ends of the horns, and the variable presence or absence of the lateral horns make Balmula tripenta distinctive. B. pentaradiata differs by having the periphragm formed into a circlet of three to five spinules at the horn tips. Also the body is broader and the two walls are appressed. No specimens lacking the two lateral horns have been reported for the latter species.
Original description: Bint, 1986, p.158, 160
Large, dorso-ventrally compressed ceratioid cysts with an apical and two subequal antapical horns, and with or without two lateral horns. Lateral horns are postcingular and are long and conspicuous on some specimens but completely absent on others. All horns are long, narrow, and distally rounded. Apical horn may bear a solid projection at its tip. Left antapical horn may be slightly longer than right.
Cysts two-layered. Endocyst has three or five prominent horns: apical, two antapicals, and two laterals which may or may not be present. Periphragm lies close to endophragm, but usually separated from it, and comes to an irregular termination toward ends of horns so that the distal portion of the horn is formed by endophragm only. Both walls are smooth and thin.
Paratabulation not expressed. Cingulum is indicated by faint transverse lines, sulcus is not indicated. Archeopyle apical, suture is weakly angular or ragged, operculum usually remains in place and thus is probably adnate.
Size. Length of complete five-horned specimen 120(130)148 µm, 8 measurements; length of two specimens with operculum broken away 82 and 90 µm; width excluding lateral horns 45(53)59 µm; 10 specimens measured. Length of complete threehorned specimen 118(133)177 µm, 9 measurements; length of one specimen with operculum broken away 88 µm; width 41(48)56 µm; 10 specimens measured. Approximate lengths of horns: apical 37-80 µm, lateral 20-35 µm, antapical 25-45 µm.
Remarks. Two distinct morphotypes of Balmula tripenta can be recognized based on the presence or absence of the lateral horns. The first type (Plate 6, figs. 9, 10, 13) possesses two long, narrow, distally rounded postcingular horns formed by the endocyst with the periphragm terminating before the ends of the horns. These specimens have a total of five horns, one apical, two lateral, and two antapical. The second morphotype (Plate 6, figs. 11, 12) completely lacks the two lateral horns and has a total of only three horns--one apical and two antapical-but the distinctive termination of the periphragm near the horn tips clearly marks it as the same species.
Affinities:
Bint, 1986, p.160 The prolongation of the endocyst into long horns with the periphragm terminating before the ends of the horns, and the variable presence or absence of the lateral horns make Balmula tripenta distinctive. B. pentaradiata differs by having the periphragm formed into a circlet of three to five spinules at the horn tips. Also the body is broader and the two walls are appressed. No specimens lacking the two lateral horns have been reported for the latter species.