Upper Cretaceous

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Review of Palaeobotany and Palynology 106 (1999) 121–129 www.elsevier.com/locate/revpalbo

Alterbidinium austrinum Roncaglia et Schiøler, sp. nov., a new dinoflagellate from the Conway Siltstone (Upper Cretaceous), southern Marlborough, New Zealand Lucia Roncaglia a,Ł , Poul Schiøler b a

Universita` degli Studi di Modena e Reggio E., Dipartimento di Scienze della Terra, Via Universita` 4, I-41100 Modena, Italy b Geological Survey of Denmark and Greenland (GEUS), Thoravej 8, DK-2400 Copenhagen NV, Denmark Received 14 July 1998; revised version received 5 March 1999; accepted 10 March 1999

Abstract The new dinoflagellate Alterbidinium austrinum Roncaglia et Schiøler, sp. nov. from the uppermost lower Haumurian (mid-upper Campanian) Isabelidinium korojonense Interval Zone in New Zealand, is a large, circumcavate, dorso-ventrally compressed, peridinioid cyst with subpentagonal outline. The pericyst bears two lateral and two or three antapical horns. One or two projections=horns usually occur at the apex. The endocyst is thin-walled, subcircular, and located centrally. The paratabulation is expressed by the paracingulum and the intercalary hexa 2a peri-archeopyle. Alterbidinium austrinum was encountered in a narrow stratigraphic interval in the Conway Siltstone, and may be a potential stratigraphic marker.  1999 Elsevier Science B.V. All rights reserved. Keywords: New Zealand; dinoflagellates; taxonomy; Alterbidinium; Upper Cretaceous; Campanian

1. Introduction During an extensive palynological study on Upper Cretaceous sections from the South Island of New Zealand carried out as part of the New Zealand Time Scale Project, Alterbidinium austrinum Roncaglia et Schiøler, sp. nov. was encountered in the highly diversified and well preserved dinoflagellate assemblages from the Conway Siltstone in southern Marlborough. In New Zealand, the Conway Siltstone is a medium grey, soft, jarositic, very fine sandy siltŁ Corresponding

author. Tel.: C45-38-142704; Fax: C45-38142050; E-mail: [email protected]

stone to silty sandstone with scattered large, subspherical, calcareous concretions. The Conway Siltstone extends throughout the southern Marlborough and northern Canterbury region on the South Island of New Zealand; it was described by Warren and Speden (1978) from the north face section of Haumuri Bluff, in southern Marlborough (Fig. 1). In southern Marlborough, the Conway Siltstone overlies the Tarapuhi Grit and is overlain by the Claverley Sandstone (Fig. 2); in this area, the formation is deposited in an open marine environment with considerable influx of terrestrial material, and encompasses the lower Haumurian to lowermost upper Haumurian interval. Based on palynological data, the lower Haumurian to lowermost upper Hau-

0034-6667/99/$ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 3 4 - 6 6 6 7 ( 9 9 ) 0 0 0 0 5 - 6

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L. Roncaglia, P. Schiøler / Review of Palaeobotany and Palynology 106 (1999) 121–129

Fig. 1. Location map of the Haumuri Bluff north face and Conway River sections, southern Marlborough, New Zealand.

murian interval is correlated with the lower to upper Campanian interval (Roncaglia and Schiøler, 1997; Schiøler and Wilson, 1998; Roncaglia et al., 1999). In northern Canterbury, the Conway Siltstone overlies the Broken River Formation and underlies the Loburn Mudstone; in this area, it is deposited in a nearshore marine environment, and encompasses the upper Haumurian. Based on palynological data, the upper Haumurian is correlated with the upper Campanian–upper Maastrichtian interval (Roncaglia and Schiøler, 1997; Roncaglia et al., 1999). The new species occurs in the uppermost lower Haumurian (mid-upper Campanian) Isabelidinium korojonense Zone (Roncaglia et al., 1999) within a narrow stratigraphic interval.

2. Material and methods This paper is based on the study of dinoflagellate assemblages from 32 samples from two sections located in southern Marlborough; one at the north face of Haumuri Bluff and the other on the left side of the Conway River, in a railway cutting between Hundalee and Claverley (Fig. 1). Fig. 2 shows simplified lithologic logs of the Haumuri Bluff north face and Conway River sections with the position of the sample points. The measured lithologic logs from the Haumuri Bluff north face and the Conway River sections are kept at the Institute of Geological and Nuclear Sciences (IGNS), Lower Hutt, New Zealand, with the identification numbers O32c1 and


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Fig. 2. Simplified lithologic logs of the Haumuri Bluff north face and Conway River sections, showing the position of sample points. Asterisks indicate the samples where Alterbidinium austrinum Roncaglia et Schiøler, sp. nov. occurs. C D Conway Siltstone; CS D Claverley Sandstone; OS D Okarahia Sandstone; TG D Tarapuhi Grit.

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O32c3, respectively. Alterbidinium austrinum occurs in two samples only from the Conway Siltstone, at 195 and 152 m above the contact with the Torlesse Supergroup, in the Haumuri Bluff north face and Conway River section, respectively (Fig. 2). Standard palynological techniques, involving the use of HCl and HF (70%), were used. The residue was sieved on 15 µm filter cloth. Oxidation (2 min. in 36% nitric acid) and heavy liquid separation (using sodium polytungstate) were carried out. The macerate was mounted in glycerine jelly on microscope slides. The type specimen of Alterbidinium austrinum and all figured specimens are housed in the palynological type collection of IGNS, Lower Hutt, New Zealand. The illustrated specimens are either from single mounts or strew mounts, and are identified with either IGNS single mount number, or slide number and England Finder coordinates. In New Zealand, all fossil localities are registered in the Fossil Record File (FRF) which is a national database administered and updated by the Geological Society of New Zealand; it includes all sites and samples that have been investigated for fossils in New Zealand. The Fossil Record File is arranged according to the NZMS 260 series 1 : 50,000 topographical map sheet areas. The FRF sample numbers are provided herein for all illustrated specimens.

3. Systematic palynology Dinoflagellate species mentioned below are referenced in Williams et al. (1998); informal taxa are referenced herein. Division DINOFLAGELLATA (Bu¨tschli, 1885) Fensome et al., 1993 Subdivision DINOKARYOTA Fensome et al., 1993 Class DINOPHYCEAE Pascher, 1914 Subclass PERIDINIPHYCIDAE Fensome et al., 1993 Alterbidinium Lentin et Williams, 1985 emend. Khowaja-Ateequzzaman et al., 1991 Type: Alterbidinium acutulum (Wilson, 1967) Lentin et Williams, 1985 emend. Khowaja-Ateequzzaman et al., 1991.

Alterbidinium austrinum Roncaglia et Schiøler, sp. nov. (Fig. 3Fig. 2A–F; Plate I, 1–9; Plate II, 1–6) Holotype: FRF no. O32=f175, IGNS SM 4736 (Plate I, 1–2). Paratypes: (1) FRF no. O32=f175, IGNS SM 4737 (Plate I, 3); (2) FRF no. O32=f175, IGNS SM 4738 (Plate I, 5); (3) FRF no. O32=f175, IGNS SM 4741 (Plate II, 1). Repository: The palynological type collection, Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand. Type locality: Conway River railway cutting, southern Marlborough, New Zealand. Type stratum: Conway Siltstone, 152 m above the contact with the Torlesse Supergroup, uppermost lower Haumurian (sample FRF no. O32=f175). A correlative level occurs in the Haumuri Bluff north face section, at 195 m above the contact with the Torlesse Supergroup (sample FRF no. O32=f206). Occurrence: Uppermost lower Haumurian (midupper Campanian) Isabelidinium korojonense Zone (Roncaglia et al., 1999), in the Conway Siltstone at the Conway River railway cutting and Haumuri Bluff north face section. It is also present in the Herring Formation at a measured section in the upper reaches of Ben More Stream in the interval 70.5–106.5 m (IGNS section identification: P30c14); all sections are located in southern Marlborough, New Zealand. Etymology: Latin, austrinus, a, um D southern, austral. Diagnosis: Large, circumcavate, dorso-ventrally compressed, peridinioid cyst, with subpentagonal outline, and two lateral and two or three antapical horns. One or two projections=horns usually occur at the apex. The pericyst is thin-walled and smooth. The endocyst is located centrally, circular to subcircular in shape, smooth, and very thin-walled. The paracingulum is partially indicated on the lateral horns by short, transverse folds in the periphragm. The archeopyle is intercalary, type I(2a), steno- to iso-deltaform; the operculum is attached posteriorly. The paratabulation is indicated by paracingulum and archeopyle only. Description: Cyst large, circumcavate, dorso-ventrally compressed, subpentagonal in outline. The epicyst and hypocyst are approximately equal in size. The pericyst is smooth and thin-walled; it bears two


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Fig. 3. Variation in pericyst and endocyst outline of Alterbidinium austrinum Roncaglia et Schiøler, sp. nov. The specimens are to the same scale and also illustrated on Plates I and II. (A) Holotype, Plate I, 1–2. (B) Paratype 1, Plate I, 3. (C) Plate II, 2. (D) Plate I, 6. (E) Plate I, 4. (F) Plate II, 3.

lateral and two or three antapical horns. Usually, one or two apical projections occur on the pericyst. The length of the apical projections is highly variable (3– 38.5 µm). When single, the apical projection consists of a long (15–38.5 µm) hollow subconical horn with rounded, truncate or involute tip (Fig. 3A, B, E); when two apical projections are present, they consist of short solid bulges (Fig. 3C, F). A wart-like 3 µm long apical structure surrounded by concentric rings occurs centrally between the bulges, on the ventral side of the cyst (Plate II, 5). In some specimens, the apex may be truncate, and apical projections absent; however, the wart-like apical structure is still present on these specimens (Fig. 3D; Plate I, 6). The left antapical horn is well developed, subconical, with

acuminate, rounded or truncate termination; the right antapical horn is usually reduced in size and has a sharp to rounded termination. A third horn may occur between the left and right antapical horns, on the dorsal side of the cyst: it is shorter than the left antapical horn, hollow and with rounded or truncate termination (Fig. 3C; Plate II, 2, 4). The periphragm bears two lateral horns; they are hollow, subconical, distally rounded to truncate. Short transverse folds in the periphragm occur distally on the lateral horns. In the holotype and in a few more specimens, the left lateral horn terminates with a hook-shaped rounded tip. Generally, the left lateral horn is longer than the right [length range of the left lateral horn: 15 (24) 38 µm; length range of the right lateral horn: 11 (19) 34

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PLATE I



µm]. A small number of specimens with only a single left lateral and left antapical horn were encountered in the studied population (Plate I, 7; Plate II, 3, 6). The endocyst is located centrally, and is circular to subcircular in shape; it is smooth and very thin-walled, usually barely visible (Fig. 3A–F). The paracingulum is indicated by the transverse folds in the periphragm on the two lateral horns. Generally, the parasulcus is not expressed; however, it may be indicated by an axial invagination on the lower ventral side of the periphragm. A steno- to iso-deltaform intercalary archeopyle, type I(2a), is usually present; archeopyle index: 0.34 (0.41) 0.46. The operculum is attached posteriorly. The paratabulation pattern is indicated by the paracingulum and archeopyle only. Dimensions (in µm)

Holotype

Range

Pericyst (35 specimens measured) Overall length 211 Overall width 148

125 (186) 250 95 (137) 182

Endocyst (6 specimens measured) Length 68 Width 76

49 (57) 68 49 (62) 76

Discussion: Alterbidinium austrinum differs from Alterbidinium? distinctum (Wilson, 1967) Lentin et Williams, 1985 and Alterbidinium dictyotum Harker et Sarjeant in Harker et al. (1990) in being larger, in having two lateral horns, and in lacking clear indication of a parasulcus. It differs further from A.? distinctum in having a very thin, transparent endophragm, and from A. dictyotum in being circumca vate and in having a smooth periphragm. The new species

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differs from Alterbidinium? pentaradiatum (Cookson et Eisenack, 1965) Lentin et Williams, 1985 in having a smaller, thin-walled, and transparent endocyst, in having a reduced right antapical horn, and in lacking clear indication of a parasulcus. Alterbidinium austrinum resembles the informal taxon ‘Alterbidinium longicornutum’ Roncaglia et Schiøler, 1997 (pl. 2, 1–3), in size and archeopyle shape, but differs in having a subpentagonal outline, in having a smaller, smooth-walled, transparent endocyst, and in possessing two or three antapical horns. Alterbidinium austrinum resembles species of the genus Satyrodinium Lentin et Manum, 1986 in size, archeopyle shape and, occasionally, in the morphology of the apical and antapical areas. Some specimens of A. austrinum conform with the general diagnosis of Satyrodinium in having (1) an intercalary, type I(2a), iso-deltaform archeopyle, (2) a mid-apical wart-like structure between two apical bulges on the ventral surface (Fig. 3C, D, F; Plate I, 6–7; Plate II, 2, 3, 5), and (3) a median, reduced, third antapical horn developed between the two antapical horns (Fig. 3C; Plate II, 2, 4). However, the new species is readily distinguishable from the genus Satyrodinium in being circumcavate, in having a subpentagonal outline, in having two paracingular lateral horns, and in possessing clear indication of paracingulum. Furthermore, many specimens of A. austrinum have a single apical horn. Alterbidinium austrinum resembles Manumiella n. sp. 2 of Askin (1988, fig. 9, 4-5) in size and archeopyle shape, but lacks the readily discernible endophragm that characterises the latter taxon. The new species differs from other species of the genus

PLATE I Alterbidinium austrinum Roncaglia et Schiøler, sp. nov. from the Haumuri Bluff north face and Conway River sections, southern Marlborough, New Zealand. The same scale is used for all specimens. Scale bar in 1 D 30 µm. 1. Holotype. FRF no. O32=f175, IGNS SM 4736. Dorsal view, optical section. 2. Holotype. FRF no. O32=f175, IGNS SM 4736. Dorsal surface in high focus. 3. Paratype 1. FRF no. O32=f175, IGNS SM 4737. Dorsal surface in high focus. 4. FRF no. O32=f175, IGNS SM 4739. Ventral view, sectional focus. 5. Paratype 2. FRF no. O32=f175, IGNS SM 4738. Ventral view, sectional focus. 6. FRF no. O32=f175, L17315=4a (England Finder coordinates Y34-1). Ventral surface in high focus. Note wart-like structure at the apex. 7. FRF no. O32=f175, IGNS SM 4735. Ventral surface in high focus. Note single left lateral horn. 8. FRF no. O32=f175, IGNS SM 4740. Right lateral view, sectional focus. 9. FRF no. O32=f175, IGNS SM 4734. Dorsal surface in high focus.

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PLATE II

Alterbidinium austrinum Roncaglia et Schiøler, sp. nov. from the Haumuri Bluff north face and Conway River sections, southern Marlborough, New Zealand. All specimens are to the same scale except 4–5. Scale bar in 1 D 30 µm; scale bar in 5 D 20 µm. 1. Paratype 3. FRF no. O32=f175, IGNS SM 4741. Ventral view, sectional focus. 2. FRF no. O32=f175, L17315=5a (England Finder coordinates Z31-3). Ventral surface in high focus. 3. FRF no. O32=f175, IGNS SM 4742. Dorsal surface in low focus. 4. Same specimen as 2. Ventral surface, antapical area in high magnification. 5. Same specimen as 2. Ventral surface, apical area in high magnification. 6. FRF no. O32=f175, IGNS SM 4733. Dorsal surface in low focus.

Manumiella in its subpentagonal outline, its two paracingular lateral horns, and its steno- to isodeltaform peri-archeopyle. Despite the high morphologic variability observed in the apical, antapical and lateral regions of A. austrinum, its large size, its subpentagonal outline, and the very thin-walled endocyst, are invariable features that facilitate its identification. Alterbidinium aus-

trinum is figured by Roncaglia et al. (1999, figs. 13.7 and 17.6) as ‘dinocyst sp. 1’.

Acknowledgements Lucia Roncaglia acknowledges funding from the Ministry of University, Scientific Research and Tech-


nology (MURST, Rome, Italy); Poul Schiøler acknowledges a research grant from the Danish Natural Science Research Council and publishes with the permission of the Geological Survey of Denmark and Greenland. Thanks to Roger Tremain (IGNS, Lower Hutt, New Zealand) for processing the samples, and to Stefan Sølberg (GEUS, Copenhagen, Denmark) for drawing Fig. 1. The authors are grateful to Judith Lentin and Morten Smelror whose constructive criticism greatly improved the initial manuscript.

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