Back
Dioxya armata
Dioxya armata Cookson and Eisenack, 1958; emend. Morgan, 1977
Holotype: Cookson and Eisenack, 1958, pl.11, fig.11, text-fig.20
Locus typicus: Omati, Papua
Stratum typicum: Albian
Original description: Cookson and Eisenack, 1958, p. 59
Shell broadly fusiform with one end sharply pointed and smooth, the other broader, slightly truncate and with a few small terminal spines. The surface is covered with relatively thick, finger-like or occasionally pointef outgrowth, which in the type are irregulary arranged, and in other specimens are in parallel equatorial rows. The wall is rather thick, firm and transparent. In the type, the outline of a small squarish pylome is suggested near the more pointed end of the shell.
Dimensions: Type 55x40 Ám overall. Paratype 48x38 Ám overall.
Emended description:Morgan, 1977, p. 131-132, 134
Ambitus ovoidal, apex drawn into a broad, truncate apical horn, antapex into a broad, eccentrically located antapical bulge, often bearing a long spine. Epicyst and hypocyst of similar size, the epicyst usually slightly larger. Apparent autophragm usually about 0.5 Ám thick bearing sparse, usually 1-3 Ám long (shorter towards the apex), solid, subcylindrical, blunt spines. Rare specimens, including the holotype, have 1.0 Ám thick autophragm and larger (to 7 Ám long and 2 Ám thick) subcylindrical spines. Autophragm does not accept stain. Spines nontabular except at paracingulum and parasulcus. Paracingulum defined by two rows of aligned spines (Pl. 2, figs. 1a, 1d, 2a, 2c). Area of paracingulum between parasutures devoid of ornamentation. Parasulcus delineated by absence of ornamentation (Pl. 2, figs. 1d, 2c) extends slightly onto epicyst and almost to antapex on hypocyst. Archeopyle probably standard hexa intercalary la (Pl. 2, figs. 1b, 1c, 2a).
Dimensions: 48-55 Ám long and 38-40 Ám broad.
Comment: D. armata and Spinidinium styloniferum Cookson and Eisenack (1962) have similar ambitus and ornamentation, but differ in wall structure; D. armata has an apparent autophragm, S. styloniferum has a periphragm and endophragm, with small pericoels located beneath the horns. The two species are most common in the Albian, D. armata in Papua, S. styloniferum in more southerly latitudes in Australia, and they sometimes occur together. It seems likely that wall separation at the horns may not be as taxonomically significant as has been thought. Such separation may be produced by environmental influences, or perhaps, as in some spores and pollen, may be induced sometimes by chemical treatment.
Affinities:
Morgan, 1977, p. 134: Dioxya armata is characterized by the thick apparent autophragm, ovoidal ambitus with a broad, truncate apical horn and a single, eccentrically located antapical bulge, and sparse, 13 Ám long, nontabular, solid, subcylindrical, blunt spines.
Other species of Dioxya are: D. apertura (Wilson 1967) comb.nov., ?D. extensa (Stover 1973), ?D. filigrana (Benedek 1972), D. rotunda (Wilson 1967), ?D. tenella (Morgenroth 1966), D. tenera (Krutsch 1962), and D. villosa Eisenack and Cookson 1960.
D. tenera, ?D. tenella and D. villosa differ from D. armata by having two symmetrically located antapical horns, not one eccentrically located antapical horn. D. tenera bears sparse sharp, 1-2 Ám, spines and has small, unequal antapical horns; ?D. tenella bears very sparse, sharp, 3-4 Ám spines and has strong, subequal antapical horns; D. villosa has dense, 2-3 Ám, sharp spines, with two small unequal antapical horns. D. villosa has a standard hexa archeopyle, but no archeopyle is known on ?D. tenella and D. tenera.
?D. extensa and ?D. filigrana differ from Dioxya by having broad hexa, not standard hexa archeopyles. ?D. extensa has an ovoidal ambitus with broad bulges marking the apical and two weak antapical horns, dense, tabular, 3-4 Ám spines, and ?D. filigrana has an ovoidal ambitus with small pericoels marking the weak apical and single antapical bulges, and fine short spines.
D. apertura and D. rotunda are very similar to D. armata, but differ by having acuminate, not blunt spines. D. apertura and D. rotunda both have a broad, truncate apical horn and single, sharp, eccentrically located antapical horn, sparse, 3-4 Ám, sharp, nontabular spines, and a standard hexa archeopyle. D. apertura differs from D. rotunda by having an ovoidal, not subcircular, ambitus.
Holotype: Cookson and Eisenack, 1958, pl.11, fig.11, text-fig.20
Locus typicus: Omati, Papua
Stratum typicum: Albian
Original description: Cookson and Eisenack, 1958, p. 59
Shell broadly fusiform with one end sharply pointed and smooth, the other broader, slightly truncate and with a few small terminal spines. The surface is covered with relatively thick, finger-like or occasionally pointef outgrowth, which in the type are irregulary arranged, and in other specimens are in parallel equatorial rows. The wall is rather thick, firm and transparent. In the type, the outline of a small squarish pylome is suggested near the more pointed end of the shell.
Dimensions: Type 55x40 Ám overall. Paratype 48x38 Ám overall.
Emended description:Morgan, 1977, p. 131-132, 134
Ambitus ovoidal, apex drawn into a broad, truncate apical horn, antapex into a broad, eccentrically located antapical bulge, often bearing a long spine. Epicyst and hypocyst of similar size, the epicyst usually slightly larger. Apparent autophragm usually about 0.5 Ám thick bearing sparse, usually 1-3 Ám long (shorter towards the apex), solid, subcylindrical, blunt spines. Rare specimens, including the holotype, have 1.0 Ám thick autophragm and larger (to 7 Ám long and 2 Ám thick) subcylindrical spines. Autophragm does not accept stain. Spines nontabular except at paracingulum and parasulcus. Paracingulum defined by two rows of aligned spines (Pl. 2, figs. 1a, 1d, 2a, 2c). Area of paracingulum between parasutures devoid of ornamentation. Parasulcus delineated by absence of ornamentation (Pl. 2, figs. 1d, 2c) extends slightly onto epicyst and almost to antapex on hypocyst. Archeopyle probably standard hexa intercalary la (Pl. 2, figs. 1b, 1c, 2a).
Dimensions: 48-55 Ám long and 38-40 Ám broad.
Comment: D. armata and Spinidinium styloniferum Cookson and Eisenack (1962) have similar ambitus and ornamentation, but differ in wall structure; D. armata has an apparent autophragm, S. styloniferum has a periphragm and endophragm, with small pericoels located beneath the horns. The two species are most common in the Albian, D. armata in Papua, S. styloniferum in more southerly latitudes in Australia, and they sometimes occur together. It seems likely that wall separation at the horns may not be as taxonomically significant as has been thought. Such separation may be produced by environmental influences, or perhaps, as in some spores and pollen, may be induced sometimes by chemical treatment.
Affinities:
Morgan, 1977, p. 134: Dioxya armata is characterized by the thick apparent autophragm, ovoidal ambitus with a broad, truncate apical horn and a single, eccentrically located antapical bulge, and sparse, 13 Ám long, nontabular, solid, subcylindrical, blunt spines.
Other species of Dioxya are: D. apertura (Wilson 1967) comb.nov., ?D. extensa (Stover 1973), ?D. filigrana (Benedek 1972), D. rotunda (Wilson 1967), ?D. tenella (Morgenroth 1966), D. tenera (Krutsch 1962), and D. villosa Eisenack and Cookson 1960.
D. tenera, ?D. tenella and D. villosa differ from D. armata by having two symmetrically located antapical horns, not one eccentrically located antapical horn. D. tenera bears sparse sharp, 1-2 Ám, spines and has small, unequal antapical horns; ?D. tenella bears very sparse, sharp, 3-4 Ám spines and has strong, subequal antapical horns; D. villosa has dense, 2-3 Ám, sharp spines, with two small unequal antapical horns. D. villosa has a standard hexa archeopyle, but no archeopyle is known on ?D. tenella and D. tenera.
?D. extensa and ?D. filigrana differ from Dioxya by having broad hexa, not standard hexa archeopyles. ?D. extensa has an ovoidal ambitus with broad bulges marking the apical and two weak antapical horns, dense, tabular, 3-4 Ám spines, and ?D. filigrana has an ovoidal ambitus with small pericoels marking the weak apical and single antapical bulges, and fine short spines.
D. apertura and D. rotunda are very similar to D. armata, but differ by having acuminate, not blunt spines. D. apertura and D. rotunda both have a broad, truncate apical horn and single, sharp, eccentrically located antapical horn, sparse, 3-4 Ám, sharp, nontabular spines, and a standard hexa archeopyle. D. apertura differs from D. rotunda by having an ovoidal, not subcircular, ambitus.