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Isabelidinium marshallii
Isabelidinium marshallii Roncaglia, 2000, p.138–139,142–143,145, figs.3A–N,4A–N.
Holotype: Roncaglia, 2000, figs.3A–B.
Age: Campanian.
Original description (Roncaglia, 2000):
Isabelidinium marshallii sp. nov. (Figs 3, 4)
Holotype. FRF no. O32/t"217, IGNS SM 4751 (Fig. 3A, B)
Paratypes. 1. FRF no. O32/1218, IGNS SM4674 (Fig. 4A); 2. FRF no. O32/t218, IGNS SM 4678 (Fig. 4M); 3. FRF no. O32/f217, IGNS SM 4745 (Fig. 4E, F)
Repository. The palynological type collection, Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand.
Type locality. Haumuri Bluff north face, southern Marlborough, New Zealand.
Type stratum. Conway Siltstone, from 120 to 195 m above the contact with the Torlesse Supergroup, Campanian. A correlative level occurs in the Conway River section, from 106 to 152 m above the contact with the Torlesse Supergroup.
Occurrence. From the lower to middle Campanian Satyrodinium haumuriense Interval Zone of Marshall (1990) to the middle to upper Campanian Isabelidinium korojonense Zone of Roncaglia et al. (1999), at the Haumuri Bluff north face and Conway River railway cutting (this paper; as Satyrodinium "punctutum" in Roncaglia & S chi¢ler 1997; as Satyrodinium? sp. 1 in Roncaglia et al. 1999).
Etymology. After Dr. Neil G. Marshall in recognition of his contributions to palynology in the southern hemisphere.
Diagnosis. Large, bicavate, dorso-ventrally compressed, elongate, peridinioid cyst, with one apical and one left antapical horn. The pericyst is thin-walled, smooth to granulated. The endocyst is located centrally, oval to subcircular in shape, thin-walled and smooth. The parasulcus is indicated by divergent, longitudinal folds on the periphragm and a shallow groove on the midventral surface. Occasionally, the paracingulum is indicated by parallel, low ridges or transverse folds in the periphragm. The archeopyle is intercalary, type I(2a), iso- to steno-deltaform; the operculum is always attached posteriorly.
Description. Cyst large, bicavate, elongate, dorso-ventrally compressed, with one apical and one left antapical horn. The epicyst and hypocyst are approximately equal in size. The pericyst is thin-walled (0.5-1 µm), smooth to granulated. When occurring, the granulae are evenly distributed near the poles, but sparse to absent on the mid-ventral and mid-dorsal surface of the pericyst (Fig. 4A, B). The apical horn is hollow, 5 to 30 lain long, and distally rounded; occasionally, the apical horn bears a solid, sharp spine on the top (Figs 3E, 4N). The left antapical horn is hollow, long (10-25 µm) and sharp. The right antapical horn is absent or poorly developed. The endocyst is oval to subcircular and centrally located. The endophragm is thin and smooth, closely appressed to the mid-ventral and mid-dorsal part of the pericyst. In most specimens, the endophragm is transparent and the endocyst barely visible. The parasulcus is indicated by two, divergent, longitudinal folds on the periphragm, separated by a shallow groove on the mid-ventral surface of the hypocyst (Figs 3M, 4F). When expressed, the paracingulum is indicated by either 2 parallel, partite, low ridges or transverse folds on the periphragm (Figs 3I, 4C-F). An iso- to steno-deltaform intercalary archeopyle, type I(2a), is always present; archeopyle index (mean value in brackets): 0.3 (0.4) 0.52. The operculum is always attached posteriorly. The paratabulation is indicated by the parasulcus, archeopyle and occasionally the paracingulum.
Dimensions (in µm; mean value in brackets). Pericyst (15 specimens measured): overall length 137 (166) 195, holotype 184; overall width 70 (88) 110, holotype 91. Endocyst (10 specimens measured) length 43 (73) 90, holotype 70; width 57 (75) 95, holotype 91.
Comparison. lsabelidinium marshallii differs from I. greenense by having a thin, smooth endophragm, by having a single, sharp, left antapical horn and indication of parasulcus. lsabelidinium marshallii closely resembles I. glabrum in general outline. However, it differs from the latter by being bicavate, larger in size, having an iso- to steno-deltaform archeopyle and having indication of a parasulcus. In addition, I. glabrum always has a readily discernible endophragm, lsabeliclinium marshallii differs from I. bakeri, L belfastense, I. korojonense, and I. pellucidum by being larger, having an iso- to steno-deltaform peri-archeopyle, and having a single, sharp, left antapical horn.
Discussion. lsabelidinium marshallii resembles species of the genus Alterbidinium in outline and archeopyle shape. Lentin & Williams (1985) proposed and Khowaja-Ateequzzaman et al. (1991) emended the genus Alterbidinium to accomodate proximate, dorso-ventrally compressed, circumcavate cysts, with one apical and two unequal antapical horns, indication of paracingulum, and intercalary, steno-/isodeltaform peri-archeopyle (Fig. 6). However, being bicavate, the new taxon cannot be included within the genus Alterbidinium. Few circumcavate specimens with the pericyst outline similar to 1. marshallii and a distinctive endocyst were observed within the assemblages (Fig. 5I)). These specimens are considered transitional between/. marshallii and Alterbidinium longicornutum Roncaglia et al. (1999). lsabelidinium marshallii resembles Amphidiadema rectangularis in size and archeopyle shape. However, the new species differs by having one apical horn, the operculum attached, and indication of paratabulation other than the archeopyle (the parasulcus and, occasionally, paracingulum are expressed in I. marshallii), lsabelidinium marshallii differs further from species of Amphidiadema by lacking epi- and hypo-coels that are narrower than the width of the endocyst. lsabelidinium marshallii resembles specimens of ManumieUa seymourensis Askin (1999) with apical and left antapical horn (see Askin 1999, fig. 3.3). However,/. marshalliidiffers from the latter by being bicavate, more elongate, and by having an iso- to steno-deltaform periarcheopyle. Furthermore, the average size of I. marshallii is significantly larger than M. seymourensis (Fig. 5I), and the length ranges of the two species do not overlap. Figure 7 shows the stratigraphic range of 13 selected peridinioid dinoflagellates from the Coniacian-Maastrichtian interval in southern Marlborough (after Schi¢ler & Wdson 1998; Roncagliaet al. 1999). In southern Marlborough, the stratigraphic range of M. seymourensis (asManumiella sp. 3 of Askin 1988 in Roncaglia et al. 1999) overlaps the range of/. marshallii and Satyrodinium species (Fig. 7). Lentin & Williams (1975) defined Isabelidinium for bicavate to circumcavate, elongate, peridinioid cysts, with one apical and two antapical horns, indications of paracingulum, and intercalary, omegaform peri-archeopyle (Fig. 6). Marshall (1988) emended lsabelidinium for elongate peridinioid cysts with a deltaform to thetaform peri-archeopyle. Based on Marshall (1988), the genus Isabelidinium may include taxa with an iso- to steno-deltaform peri-archeopyle (Fig. 6). Therefore, the new taxon is included in Isabelidinium. Isabelidinium marshallii closely resembles S. haumuriense in size, archeopyle shape, and hypocyst outline (Fig. 5A, B, L). Abundant, wellpreserved specimens of I. marshallii and S. haumuriense were recovered at Haumuri Bluff and in the Conway River section. In particular, the assemblages document the continuous morphologic gradation betweenI, marshallii and S. haumuriense. Lentin & Manum (1986, p. 112) proposed the genus Satyrodinium for bicavate, compressed elongate, peridinioid cysts, with two to three apical and one or more antapical horns, with a mid-apical pore-like structure between the apical horns, and without indication of paratabulation apart from the archeopyle (Fig. 6). Thus, the original diagnosis of the genus Satyrodinium (Lentin & Manum 1986, p.l12) implies the presence of at least 2 apical horns. The new taxon differs from S. haumuriense by having only one apical horn, and indication of parasulcus; thus it cannot be included in Satyrodinium (Fig. 6). The overall similarity between the species S. haumuriense and I. marshallii suggests a close relationship between Satyrodinium and Isabelidinium. Despite the attribution of S. haumuriense and I. marshallii within two different genera, one of the two species may have evolved from the other. In New Zealand, S. haumuriense and I. marshallii first occur above Isabelidinium species (i.e. 1. belfastense, I. cretaceum, and I. glabrum) and below S. bengalense, the only other species of the genus (Fig. 7). According to Wilson (1984b, p. 554), S. haumuriense is characterised by a broadly truncated apex with a central notch and, occasionally, short rounded projection (Fig. 5A, B, L). The type species of Satyrodinium, S. bengalense, bears two well-developed lateral apical horns which tend to recurve towards the apex, and a central apical notch which might develop into a low mid-apical horn (Lentin & Manum 1986, p. 114; Fig. 5C). Specimens showing a transition between S. haumuriense and S. bengalense, as well as transitional specimens between I. marshallii and S. bengalense were encountered in southern Marlborough, and do occur in the Late Cretaceous of New Zealand (Wilson, pers. comm. 1999). These specimens have either the epicyst of I. marshallii (single central apical horn) or the epicyst of S. haumuriense (truncate apex with central notch), combined to the hypocyst ofS. bengalense. Four transitional morphotypes are illustrated in Fig. 5E-H. Based on the continuous morphologic gradation observed between the end-forms I. marshallii, S. haumuriense and S. bengalense, and the stratigraphic range oflsabelidinium and Satyrodinium species in southern Marlborough (Fig. 7), it may be inferred that I. marshallii represents one of the linking morphotypes between the genus Isabelidinium, and S. haumuriense and S. bengalense. Thus, the genus Satyrodinium may have evolved from lsabelidinium, lsabelidinium marshallii, S. haumuriense, S. bengalense and their intergradational variants last occur within the upper Campanian I. korojonense Zone in southern Marlborough (Fig. 7). In conclusion, a highly variable morphological complex spanning populations of Alterbidinium, Isabelidinium and Satyrodinium occurs in the Campanian of New Zealand. It is uncertain whether the morphotypes observed within the complex indicate palaeoenvironmental and/or palaeogeographical variations. However, even though the generic attribution of species from the complex may change, the stratigraphic value of discrete populations such as I. marshallii, S. haumuriense and S. bengalense should remain firm.
Holotype: Roncaglia, 2000, figs.3A–B.
Age: Campanian.
Original description (Roncaglia, 2000):
Isabelidinium marshallii sp. nov. (Figs 3, 4)
Holotype. FRF no. O32/t"217, IGNS SM 4751 (Fig. 3A, B)
Paratypes. 1. FRF no. O32/1218, IGNS SM4674 (Fig. 4A); 2. FRF no. O32/t218, IGNS SM 4678 (Fig. 4M); 3. FRF no. O32/f217, IGNS SM 4745 (Fig. 4E, F)
Repository. The palynological type collection, Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand.
Type locality. Haumuri Bluff north face, southern Marlborough, New Zealand.
Type stratum. Conway Siltstone, from 120 to 195 m above the contact with the Torlesse Supergroup, Campanian. A correlative level occurs in the Conway River section, from 106 to 152 m above the contact with the Torlesse Supergroup.
Occurrence. From the lower to middle Campanian Satyrodinium haumuriense Interval Zone of Marshall (1990) to the middle to upper Campanian Isabelidinium korojonense Zone of Roncaglia et al. (1999), at the Haumuri Bluff north face and Conway River railway cutting (this paper; as Satyrodinium "punctutum" in Roncaglia & S chi¢ler 1997; as Satyrodinium? sp. 1 in Roncaglia et al. 1999).
Etymology. After Dr. Neil G. Marshall in recognition of his contributions to palynology in the southern hemisphere.
Diagnosis. Large, bicavate, dorso-ventrally compressed, elongate, peridinioid cyst, with one apical and one left antapical horn. The pericyst is thin-walled, smooth to granulated. The endocyst is located centrally, oval to subcircular in shape, thin-walled and smooth. The parasulcus is indicated by divergent, longitudinal folds on the periphragm and a shallow groove on the midventral surface. Occasionally, the paracingulum is indicated by parallel, low ridges or transverse folds in the periphragm. The archeopyle is intercalary, type I(2a), iso- to steno-deltaform; the operculum is always attached posteriorly.
Description. Cyst large, bicavate, elongate, dorso-ventrally compressed, with one apical and one left antapical horn. The epicyst and hypocyst are approximately equal in size. The pericyst is thin-walled (0.5-1 µm), smooth to granulated. When occurring, the granulae are evenly distributed near the poles, but sparse to absent on the mid-ventral and mid-dorsal surface of the pericyst (Fig. 4A, B). The apical horn is hollow, 5 to 30 lain long, and distally rounded; occasionally, the apical horn bears a solid, sharp spine on the top (Figs 3E, 4N). The left antapical horn is hollow, long (10-25 µm) and sharp. The right antapical horn is absent or poorly developed. The endocyst is oval to subcircular and centrally located. The endophragm is thin and smooth, closely appressed to the mid-ventral and mid-dorsal part of the pericyst. In most specimens, the endophragm is transparent and the endocyst barely visible. The parasulcus is indicated by two, divergent, longitudinal folds on the periphragm, separated by a shallow groove on the mid-ventral surface of the hypocyst (Figs 3M, 4F). When expressed, the paracingulum is indicated by either 2 parallel, partite, low ridges or transverse folds on the periphragm (Figs 3I, 4C-F). An iso- to steno-deltaform intercalary archeopyle, type I(2a), is always present; archeopyle index (mean value in brackets): 0.3 (0.4) 0.52. The operculum is always attached posteriorly. The paratabulation is indicated by the parasulcus, archeopyle and occasionally the paracingulum.
Dimensions (in µm; mean value in brackets). Pericyst (15 specimens measured): overall length 137 (166) 195, holotype 184; overall width 70 (88) 110, holotype 91. Endocyst (10 specimens measured) length 43 (73) 90, holotype 70; width 57 (75) 95, holotype 91.
Comparison. lsabelidinium marshallii differs from I. greenense by having a thin, smooth endophragm, by having a single, sharp, left antapical horn and indication of parasulcus. lsabelidinium marshallii closely resembles I. glabrum in general outline. However, it differs from the latter by being bicavate, larger in size, having an iso- to steno-deltaform archeopyle and having indication of a parasulcus. In addition, I. glabrum always has a readily discernible endophragm, lsabeliclinium marshallii differs from I. bakeri, L belfastense, I. korojonense, and I. pellucidum by being larger, having an iso- to steno-deltaform peri-archeopyle, and having a single, sharp, left antapical horn.
Discussion. lsabelidinium marshallii resembles species of the genus Alterbidinium in outline and archeopyle shape. Lentin & Williams (1985) proposed and Khowaja-Ateequzzaman et al. (1991) emended the genus Alterbidinium to accomodate proximate, dorso-ventrally compressed, circumcavate cysts, with one apical and two unequal antapical horns, indication of paracingulum, and intercalary, steno-/isodeltaform peri-archeopyle (Fig. 6). However, being bicavate, the new taxon cannot be included within the genus Alterbidinium. Few circumcavate specimens with the pericyst outline similar to 1. marshallii and a distinctive endocyst were observed within the assemblages (Fig. 5I)). These specimens are considered transitional between/. marshallii and Alterbidinium longicornutum Roncaglia et al. (1999). lsabelidinium marshallii resembles Amphidiadema rectangularis in size and archeopyle shape. However, the new species differs by having one apical horn, the operculum attached, and indication of paratabulation other than the archeopyle (the parasulcus and, occasionally, paracingulum are expressed in I. marshallii), lsabelidinium marshallii differs further from species of Amphidiadema by lacking epi- and hypo-coels that are narrower than the width of the endocyst. lsabelidinium marshallii resembles specimens of ManumieUa seymourensis Askin (1999) with apical and left antapical horn (see Askin 1999, fig. 3.3). However,/. marshalliidiffers from the latter by being bicavate, more elongate, and by having an iso- to steno-deltaform periarcheopyle. Furthermore, the average size of I. marshallii is significantly larger than M. seymourensis (Fig. 5I), and the length ranges of the two species do not overlap. Figure 7 shows the stratigraphic range of 13 selected peridinioid dinoflagellates from the Coniacian-Maastrichtian interval in southern Marlborough (after Schi¢ler & Wdson 1998; Roncagliaet al. 1999). In southern Marlborough, the stratigraphic range of M. seymourensis (asManumiella sp. 3 of Askin 1988 in Roncaglia et al. 1999) overlaps the range of/. marshallii and Satyrodinium species (Fig. 7). Lentin & Williams (1975) defined Isabelidinium for bicavate to circumcavate, elongate, peridinioid cysts, with one apical and two antapical horns, indications of paracingulum, and intercalary, omegaform peri-archeopyle (Fig. 6). Marshall (1988) emended lsabelidinium for elongate peridinioid cysts with a deltaform to thetaform peri-archeopyle. Based on Marshall (1988), the genus Isabelidinium may include taxa with an iso- to steno-deltaform peri-archeopyle (Fig. 6). Therefore, the new taxon is included in Isabelidinium. Isabelidinium marshallii closely resembles S. haumuriense in size, archeopyle shape, and hypocyst outline (Fig. 5A, B, L). Abundant, wellpreserved specimens of I. marshallii and S. haumuriense were recovered at Haumuri Bluff and in the Conway River section. In particular, the assemblages document the continuous morphologic gradation betweenI, marshallii and S. haumuriense. Lentin & Manum (1986, p. 112) proposed the genus Satyrodinium for bicavate, compressed elongate, peridinioid cysts, with two to three apical and one or more antapical horns, with a mid-apical pore-like structure between the apical horns, and without indication of paratabulation apart from the archeopyle (Fig. 6). Thus, the original diagnosis of the genus Satyrodinium (Lentin & Manum 1986, p.l12) implies the presence of at least 2 apical horns. The new taxon differs from S. haumuriense by having only one apical horn, and indication of parasulcus; thus it cannot be included in Satyrodinium (Fig. 6). The overall similarity between the species S. haumuriense and I. marshallii suggests a close relationship between Satyrodinium and Isabelidinium. Despite the attribution of S. haumuriense and I. marshallii within two different genera, one of the two species may have evolved from the other. In New Zealand, S. haumuriense and I. marshallii first occur above Isabelidinium species (i.e. 1. belfastense, I. cretaceum, and I. glabrum) and below S. bengalense, the only other species of the genus (Fig. 7). According to Wilson (1984b, p. 554), S. haumuriense is characterised by a broadly truncated apex with a central notch and, occasionally, short rounded projection (Fig. 5A, B, L). The type species of Satyrodinium, S. bengalense, bears two well-developed lateral apical horns which tend to recurve towards the apex, and a central apical notch which might develop into a low mid-apical horn (Lentin & Manum 1986, p. 114; Fig. 5C). Specimens showing a transition between S. haumuriense and S. bengalense, as well as transitional specimens between I. marshallii and S. bengalense were encountered in southern Marlborough, and do occur in the Late Cretaceous of New Zealand (Wilson, pers. comm. 1999). These specimens have either the epicyst of I. marshallii (single central apical horn) or the epicyst of S. haumuriense (truncate apex with central notch), combined to the hypocyst ofS. bengalense. Four transitional morphotypes are illustrated in Fig. 5E-H. Based on the continuous morphologic gradation observed between the end-forms I. marshallii, S. haumuriense and S. bengalense, and the stratigraphic range oflsabelidinium and Satyrodinium species in southern Marlborough (Fig. 7), it may be inferred that I. marshallii represents one of the linking morphotypes between the genus Isabelidinium, and S. haumuriense and S. bengalense. Thus, the genus Satyrodinium may have evolved from lsabelidinium, lsabelidinium marshallii, S. haumuriense, S. bengalense and their intergradational variants last occur within the upper Campanian I. korojonense Zone in southern Marlborough (Fig. 7). In conclusion, a highly variable morphological complex spanning populations of Alterbidinium, Isabelidinium and Satyrodinium occurs in the Campanian of New Zealand. It is uncertain whether the morphotypes observed within the complex indicate palaeoenvironmental and/or palaeogeographical variations. However, even though the generic attribution of species from the complex may change, the stratigraphic value of discrete populations such as I. marshallii, S. haumuriense and S. bengalense should remain firm.