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Isabelidinium brunae
Isabelidinium brunae Roncaglia et al., 1999, p.305,307, fig.14, nos.7–8,11.
Holotype: Roncaglia et al., 1999, fig.14, no.11.
Age: middle-late Campanian.
Original description (Roncaglia et al., 1999):
Isabelidinium brunae sp. nov. Figure 14.7, 8, 11
Holotype. Single specimen mount no. IGNS SM 4656 (Figure 14.11); from Fossil Record Sample no. O32/ f175/CR27.
Paratypes. Single specimen mount no. IGNS SM 4657 (Figure 14.7); from Fossil Record Sample no. O32/f175/CR27. Single specimen mount no. IGNS SM 4658 (Figure 14.8); from Fossil Record Sample no. O32/f175/CR27.
Type locality. Conway River railway cutting, southern Marlborough, New Zealand.
Stratigraphic occurrence. At 195 m in the Haumuri Bluff section; 152–168 m in the Conway River section. From the Isabelidinium korojonense Zone (new definition) to the I. pellucidum Zone of Roncaglia & Schiøler (1997), lower to upper Haumurian, middle to upper Campanian (Upper Cretaceous), in the Conway Siltstone, southern Marlborough, New Zealand.
Etymology. Named in memory of the senior author’s grandmother, Bruna Luppi Roncaglia.
Diagnosis. Bicavate, elongate peridinioid cyst, with one short to prominent, rounded apical horn and two unequal, divergent antapical horns. The endocyst is oval, typically broader than long, smooth and centrally located. The periphragm is thin, smooth to microgranulate. At the poles, epi- and hypo-pericoel are well developed, elongate and typically narrower than the width of the endocyst. The archeopyle is intercalary, type I(2a); operculum free. The paratabulation is indicated by the archeopyle only.
Description. Bicavate, elongate peridinioid cyst with one apical and two antapical horns. The apical horn is a short to prominent (length 1–5 µm) nipple-like structure, distally rounded. The length of the left antapical horn is variable (length 2–6 µm); when present, the right antapical horn is shorter than the left (length 1–3 µm). Both antapical horns are broadly rounded to truncate, occasionally conical with rounded tips; the tips diverge from each other. A median antapical bulge may occur between the antapical horns (Figure 14.7). The endocyst is oval, typically broader than long, and the endophragm is thin and smooth. The periphragm is thin and smooth to microgranulate; it is closely appressed to the endophragm in the equatorial and subequatorial area. At the poles, the periphragm forms large, elongate epiand hypo-pericoels, which are of similar size and typically narrower than the width of the endocyst. The paracingulum and parasulcus are not indicated. The archeopyle is intercalary, type I(2a), iso-thetaform to iso-deltaform, and the operculum is generally free. The paratabulation pattern is indicated by the archeopyle only.
Dimensions (in µm, 12 specimens measured): Holotype - Range:
Overall length: 100 - 63 (81) 100
Overall width: 74 - 33 (56) 74
Length endocyst: 43 - 28 (38) 50
Width endocyst: 74 - 33 (56) 74
Discussion. In I. brunae, the shape of the epi-pericoel varies with the size of the apical protrusion: specimens with a short apical protrusion have a subtrapezoidal epi-pericoel; specimens with a longer, prominent apical horn have a subtriangular epipericoel. The taxon resembles I. korojonense in size and general appearance, but lacks the generally quadrangular outline of the pericyst and the distinctive serrate shoulders characteristic of that species. Isabelidinium brunae differs from I. papillum in having antapical horns, epi- and hypo-pericoels that are narrower than the endocyst, and in having an isothetaform to iso-deltaform archeopyle. It is distinct from I. foucheri in being much shorter, in having a nipple-like, rounded apical horn, and an isothetaform to iso-deltaform archeopyle. It differs from I. amphiatum, I. bakeri, I. belfastense, and I. glabrum in being bicavate, and in having well-developed epiand hypo-pericoels that are, throughout their extent, narrower than the width of the endocyst. Amphidiadema denticulata and A. nucula resemble I. brunae in size, archeopyle shape, and in having epi- and hypopericoels that are narrower than the endocyst, but differ in lacking antapical horns, and in having an endocyst that is longer than broad. Furthermore, A. denticulata differs from I. brunae in having conspicuous granulae and denticles on the periphragm. Chatangiella tripartita is similar to I. brunae in general appearance, but differs in having a truncate, conical apical horn, an indication of a paracingulum, and an omegaform archeopyle.
Holotype: Roncaglia et al., 1999, fig.14, no.11.
Age: middle-late Campanian.
Original description (Roncaglia et al., 1999):
Isabelidinium brunae sp. nov. Figure 14.7, 8, 11
Holotype. Single specimen mount no. IGNS SM 4656 (Figure 14.11); from Fossil Record Sample no. O32/ f175/CR27.
Paratypes. Single specimen mount no. IGNS SM 4657 (Figure 14.7); from Fossil Record Sample no. O32/f175/CR27. Single specimen mount no. IGNS SM 4658 (Figure 14.8); from Fossil Record Sample no. O32/f175/CR27.
Type locality. Conway River railway cutting, southern Marlborough, New Zealand.
Stratigraphic occurrence. At 195 m in the Haumuri Bluff section; 152–168 m in the Conway River section. From the Isabelidinium korojonense Zone (new definition) to the I. pellucidum Zone of Roncaglia & Schiøler (1997), lower to upper Haumurian, middle to upper Campanian (Upper Cretaceous), in the Conway Siltstone, southern Marlborough, New Zealand.
Etymology. Named in memory of the senior author’s grandmother, Bruna Luppi Roncaglia.
Diagnosis. Bicavate, elongate peridinioid cyst, with one short to prominent, rounded apical horn and two unequal, divergent antapical horns. The endocyst is oval, typically broader than long, smooth and centrally located. The periphragm is thin, smooth to microgranulate. At the poles, epi- and hypo-pericoel are well developed, elongate and typically narrower than the width of the endocyst. The archeopyle is intercalary, type I(2a); operculum free. The paratabulation is indicated by the archeopyle only.
Description. Bicavate, elongate peridinioid cyst with one apical and two antapical horns. The apical horn is a short to prominent (length 1–5 µm) nipple-like structure, distally rounded. The length of the left antapical horn is variable (length 2–6 µm); when present, the right antapical horn is shorter than the left (length 1–3 µm). Both antapical horns are broadly rounded to truncate, occasionally conical with rounded tips; the tips diverge from each other. A median antapical bulge may occur between the antapical horns (Figure 14.7). The endocyst is oval, typically broader than long, and the endophragm is thin and smooth. The periphragm is thin and smooth to microgranulate; it is closely appressed to the endophragm in the equatorial and subequatorial area. At the poles, the periphragm forms large, elongate epiand hypo-pericoels, which are of similar size and typically narrower than the width of the endocyst. The paracingulum and parasulcus are not indicated. The archeopyle is intercalary, type I(2a), iso-thetaform to iso-deltaform, and the operculum is generally free. The paratabulation pattern is indicated by the archeopyle only.
Dimensions (in µm, 12 specimens measured): Holotype - Range:
Overall length: 100 - 63 (81) 100
Overall width: 74 - 33 (56) 74
Length endocyst: 43 - 28 (38) 50
Width endocyst: 74 - 33 (56) 74
Discussion. In I. brunae, the shape of the epi-pericoel varies with the size of the apical protrusion: specimens with a short apical protrusion have a subtrapezoidal epi-pericoel; specimens with a longer, prominent apical horn have a subtriangular epipericoel. The taxon resembles I. korojonense in size and general appearance, but lacks the generally quadrangular outline of the pericyst and the distinctive serrate shoulders characteristic of that species. Isabelidinium brunae differs from I. papillum in having antapical horns, epi- and hypo-pericoels that are narrower than the endocyst, and in having an isothetaform to iso-deltaform archeopyle. It is distinct from I. foucheri in being much shorter, in having a nipple-like, rounded apical horn, and an isothetaform to iso-deltaform archeopyle. It differs from I. amphiatum, I. bakeri, I. belfastense, and I. glabrum in being bicavate, and in having well-developed epiand hypo-pericoels that are, throughout their extent, narrower than the width of the endocyst. Amphidiadema denticulata and A. nucula resemble I. brunae in size, archeopyle shape, and in having epi- and hypopericoels that are narrower than the endocyst, but differ in lacking antapical horns, and in having an endocyst that is longer than broad. Furthermore, A. denticulata differs from I. brunae in having conspicuous granulae and denticles on the periphragm. Chatangiella tripartita is similar to I. brunae in general appearance, but differs in having a truncate, conical apical horn, an indication of a paracingulum, and an omegaform archeopyle.