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Gonyaulacysta vesicula
Gonyaulacysta vesicula Dodekova 1994
Holotype Dodekova 1994: pl. X, figs. 15, 16, sli(le 857-25,
Locus typicus: outcrop Mahala Popska, Sevlievo, Central North Bulgaria.
Stratum typicum: Zlatarica-Cerni Osam Fm., Late Tithonian, Paraulacosphinctes transitorius Zone, Malbosiceras chaperi Subzone
Dimensions (in Ám). Holotype: length: 64, width: 50, apical horn: 11, crests: 3-4. Range: length: 57-68, width: 50-56, length of the apical horn: 11, height of the crests: 3-4 (15 specimens measured).
Description: Dodekova 1994, p. 38-39
Proximate cornucavate cyst, with spherical central body and prominent apical horn. The wall is two-layered, closely connected, a thicker endophragm and fine periphragm. The latter forms the crests and always blunt-tipped apical horn, sometimes with a small epipericoel at the basse. There is an apical outbulge on the endophragm but it is not constant feature. The intratabular areas are smooth or shagrinate. The sutural crests are low, being slightly higher in the gonal regions with outer margins irregularly denticulate-loricate, with rare vacuoles in the base which may be secondary. The relatively wide cingulum is weakly laevorotatory. The sulcus is straight, not sigmoidal. The tabulation formula: 1-2pr?, 4", Oa, 6", 6c, 6"", 1p, 1pv, 1"" (Fig. 5). The small dimensions of the cyst did not permit to distinguish with certitude the presence of the two preapical plates. The four apical plates are present, plates 2" and 3" are greater than plates l" and 4". This is why the apical horn has an eccentric appearance and ventral-sided position (pl. X, fig. 17). The plate 4" is shorter than plate 1" and its contact with the apical end of plate 6" is narrow Anterior intercalaries are not visible. The shape and the mutual relationships of the precingular, cingular and postcingular plates are as usual. The plate 1p is small, the antapical plate 1"" is convex ans slightly assymmetrical. The archeopyle is precingular, type 1 P (3").
Remarks: Dodekova 1994, p. 38-39
Relatively small size, almost spherical form, low crests, straight undivided sulcus and smooth intratabular areas differentiate G. vesicula sp. n. from all previously described species. The most similar species is Gonyaulacysta solara Davey, 1987 from Late Berriasian of Papua, New Guinea, but it has ornamented intratabular surfaces and twice smaller apical horn.
Occurrence. Outcrop Mahala Popska, Sevlievo, Zlatarica-Cerni Osam Fm., Late Tithonian, Paraulacosphinctes transitorius Zone, Malbosiceras chaperi Subzone, borehole R-l Junak (depth 1495-1498 m, Tica Fm., Late Tithonian-Berriasian, lowermost part, Calpionella Zone, C. alpina Subzone). This species is very important biostratigraphic marker for the Jurassic-Cretaceous boundary.
Holotype Dodekova 1994: pl. X, figs. 15, 16, sli(le 857-25,
Locus typicus: outcrop Mahala Popska, Sevlievo, Central North Bulgaria.
Stratum typicum: Zlatarica-Cerni Osam Fm., Late Tithonian, Paraulacosphinctes transitorius Zone, Malbosiceras chaperi Subzone
Dimensions (in Ám). Holotype: length: 64, width: 50, apical horn: 11, crests: 3-4. Range: length: 57-68, width: 50-56, length of the apical horn: 11, height of the crests: 3-4 (15 specimens measured).
Description: Dodekova 1994, p. 38-39
Proximate cornucavate cyst, with spherical central body and prominent apical horn. The wall is two-layered, closely connected, a thicker endophragm and fine periphragm. The latter forms the crests and always blunt-tipped apical horn, sometimes with a small epipericoel at the basse. There is an apical outbulge on the endophragm but it is not constant feature. The intratabular areas are smooth or shagrinate. The sutural crests are low, being slightly higher in the gonal regions with outer margins irregularly denticulate-loricate, with rare vacuoles in the base which may be secondary. The relatively wide cingulum is weakly laevorotatory. The sulcus is straight, not sigmoidal. The tabulation formula: 1-2pr?, 4", Oa, 6", 6c, 6"", 1p, 1pv, 1"" (Fig. 5). The small dimensions of the cyst did not permit to distinguish with certitude the presence of the two preapical plates. The four apical plates are present, plates 2" and 3" are greater than plates l" and 4". This is why the apical horn has an eccentric appearance and ventral-sided position (pl. X, fig. 17). The plate 4" is shorter than plate 1" and its contact with the apical end of plate 6" is narrow Anterior intercalaries are not visible. The shape and the mutual relationships of the precingular, cingular and postcingular plates are as usual. The plate 1p is small, the antapical plate 1"" is convex ans slightly assymmetrical. The archeopyle is precingular, type 1 P (3").
Remarks: Dodekova 1994, p. 38-39
Relatively small size, almost spherical form, low crests, straight undivided sulcus and smooth intratabular areas differentiate G. vesicula sp. n. from all previously described species. The most similar species is Gonyaulacysta solara Davey, 1987 from Late Berriasian of Papua, New Guinea, but it has ornamented intratabular surfaces and twice smaller apical horn.
Occurrence. Outcrop Mahala Popska, Sevlievo, Zlatarica-Cerni Osam Fm., Late Tithonian, Paraulacosphinctes transitorius Zone, Malbosiceras chaperi Subzone, borehole R-l Junak (depth 1495-1498 m, Tica Fm., Late Tithonian-Berriasian, lowermost part, Calpionella Zone, C. alpina Subzone). This species is very important biostratigraphic marker for the Jurassic-Cretaceous boundary.