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736


Journal of Paleontology 89(5):730–747


Occurrence.—Two species are known: M. zealandicus and M. kawhiae (Schäfer and Grant-Mackie, 1994) from the Upper Triassic (Norian) of New Zealand. M. zealandicus is recorded from the Upper Triassic (Norian) of New Caledonia.


Etymology.—The genus is named from the genus Stenodiscus Crockford, 1947 because of its similarity (prefix meta- comes from Greek (μετά) and means “after,”“post-”).


Remarks.—The new genus is similar to Stenodiscus Crockford, 1945 because of monilae-shaped walls in the exozone, abundant autozooecial diaphragms and acanthostyles of two sizes. How- ever, the new genus differs in the presence of cystiphragms. Typically, Stenodiscus has two distinct sizes of acanthostyles: large acanthostyles and much smaller “microacanthostyles” between them. Acanthostyles in Metastenodiscus show a large range of size within the same colony. Metastenodiscus is also similar to Dyscritellopsis Schäfer and Grant-Mackie, 1994, but differs by its irregularly thickened walls and the presence of cystiphragms.


Metastenodiscus zealandicus (Schäfer and Grant-Mackie, 1994) Figures 7.1–7.8, 8.1–8.3; Table 1


1994 Stenodiscus zealandicus Schäfer and Grant-Mackie, p. 9, figs. 5–8.


Holotype.—OU17942a. Otago University, Dunedin, New Zealand.


Diagnosis.—Massive and encrusting colonies. Massive colo- nies up to 35mm in thickness. Secondary overgrowths com- mon, individual sheets 1.9–8.0mmthick. Exozone not distinctly separated from endozone. Autozooecia long, prismatic, poly- gonal in cross section growing from a laminated epitheca. Autozooecial apertures rounded-polygonal and strongly peta- loid due to indenting acanthostyles. Autozooecial diaphragms usually abundant throughout colony, straight or slightly curved distally, locally cystoidal. Heterozooecia rare, short, with rounded-polygonal apertures, restricted to exozone. Acantho- styles moderate to large, varying in size throughout the colony, possessing narrow cores of hyaline material and wide laminated sheaths, originating both in endo-and exozone, 2-11 surround- ing each autozooecial aperture. Macroacanthostyles two to three times larger than ordinary ones, possessing wide cores of hyaline material and wide laminated sheaths, locally surround- ing apertures in one row. Autozooecial walls laminated, inte- grated with visible zooecial boundaries, 0.0107–0.015mmthick in endozones; merged, showing distinct convex lamination without visible zooecial boundaries, often strongly beaded, with serial thickenings throughout the colony, 0.025–0.063mmthick in exozones.


Material.—Otapirian of Ile Hugon: NC/f4 (AU7148), NC/f7 (AU7149a-(1-5)), NC/f8 (AU7795), NC/f120 (Au-7180a (210a)), NC/f503 (AU7147-(4, 5)), NC/f509 (AU7154-(15-19, 21-22)); Otapirian of Ile Ducos: NC/f50 (AU7194), NC/f82 (AU7799), NC/f83 (AU7796-(2, 3, 4, 8)), NC/f87 (AU7168),


NC/f97 (AU9677-(7, 11)); Warepan of Ile Page: NC/f334 (AU7782-(1-3)), NC/f336 (AU7786-(2-4)).


Occurrence.—New Zealand; lower to middle Norian, Otamitan. New Caledonia, Ile Ducos; Upper Triassic, Rhaetian, Otapirian. New Caledonia, Ile Page. Upper Triassic, Norian, Warepan. New Caledonia, Ile Hugon; Upper Triassic, Rhaetian, Otapirian.


Remarks.—Metastenodiscus zealandicus (Schäfer and


Grant-Mackie, 1994) differs from M. kawhiae (Schäfer and Grant-Mackie, 1994) in its slightly larger autozooecial apertures (average autozooecial width 0.26mm vs. 0.24m in M. kawhiae).


Genus Dyscritellopsis Schäfer and Grant-Mackie, 1994


Type species.—Dyscritellopsis isoseptatus Schäfer and Grant-Mackie, 1994. Triassic, Orietian (upper Carnian – lower Norian); New Zealand.


Diagnosis.—Colonies cylindrical to columnar, branching, or encrusting. Distinction between endozone and exozone commonly poor. In endozone, budding pattern acyclic from zooecial corners; autozooecia circular to polygonal in transverse section; acanthostyles absent or placed at autozooecial corners. Autozooecia gradually bending outward in exozone and meeting colony surface almost at right angles. Autozooecial apertures circular or polygonal with rounded corners. Autozooecial diaphragms present, commonly more abundant in exozone than in endozone. Autozooecial walls in exozone irregularly thickened, displaying a distinctly lamellar skeletal microstructure. Acanthostyles common, varying in size, origi- nating in endo- or base of exozone. Tube-like heterozooecia present, containing diaphragms.


Occurrence.—Lower-Upper Triassic; USA, New Zealand, New Caledonia.


Remarks.—Dyscritellopsis Schäfer and Grant-Mackie, 1994 differs from Dyscritella Girty, 1911 in the presence of diaphragms in both autozooecia and heterozooecia.


Dyscritellopsis isoseptatus Schäfer and Grant-Mackie, 1994 Figures 8.4–8.8, 9.1–9.5; Table 2


Holotype.—BZ160. Institute of Geological and Nuclear Sciences Limited (GNS Science), Lower Hutt, New Zealand.


Diagnosis.—Branched and encrusting colonies, secondary overgrowths common. In branched colonies, branch diameter 3.6–8.2mm, with


1.3–3.9mm wide endozones, 0.85–2.70mm wide exozones. Secondary overgrowths 1.1–2.2mm thick. Encrusting colonies 1.3–3.5mm thick. Autozooecia long in the endozone of branched colonies, having polygonal shape in transverse section, bending at angles of 33°–55° in exozone and intersecting colony surface at angles of 83°–88°; in encrusting colonies autozooecia growing from laminated epitheca. Auto- zooecial apertures oval to rounded-polygonal. Autozooecial


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