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Chatangiella packhamii
Chatangiella packhamii, Marshall, 1990
Holotype: Marshall, 1990, figs.11A, 23G-H
Locus typicus: Southeastern Australia
Stratum typicum: Campanian
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Original description: [Marshall, 1990, p.20, 22]:
Description:
Ventrodorsal outline elongate subpentagonal. Lateral margins on epicyst tapering towards apex, or more commonly, modified by 2 rounded shoulders. Apex bearing a prominent apical horn with a rounded tip. Lateral margins on hypocyst tapering towards 2 antapical horns: left horn subtriangular, right horn indicated by a weak to distinct rounded bulge. Cysts bicavate, often with isolated pericoels below paracingular ridges. Ventrodorsal outline of endocyst subcircular to ovoidal, width greater than length.
Endophragm surface usually with fine grana or rods up to 0.5 µm wide and 2.0 µm high. Sculptural elements isolated or fused to form discontinuous rugulae. Rods occasionally extremely fine, densely packed, and linked distally, producing a fibrous layer. Periphragm scabrate to finely granulate equatorially: grana less than 0.5 µm high and wide, becoming scabrate towards the poles.
Paracingulum partite, marked by 2 parallel rows of ridges 6-8 µm apart with smooth, irregular, or denticulate crests.
Periarcheopyle Type la, isodeltaform to isothetaform, operculum usually attached along its posterior margin. Endoarcheopyle often indicated by a transverse split between adjoining boundaries of paraplates 2-4" and 1-3a, and frequently, by additional incomplete sutures between adjoining margins of paraplates 1-3a (Fig. 12D).
Dimensions:
Pericyst length 115(158)194 µm width 74(84)100 µm; endocyst length 49(65)80 µm, width 67(79)96 µm (19 specimens).
Affinities:
There is considerable variation in the length of the apical and antapical horns and development of shoulders on either side of the apex (fig.11). The most common forms encountered are similar to those in Fig. 11A-E. The ornament on both wall layers is also variable, and examples with the coarser endophragm sculpture also have the coarser periphragm sculpture.
Chatangiella packhamii is similar to C. tripartita (Cookson and Eisenack) Lentin and Williams 1976, but differs in being larger and having a more prominent sculpture on the periphragm. It is distinguished from the specimens of C. victoriensis (Cookson & Manum) Lentin and Williams 1976 recorded by Cookson and Manum (1964, p. 522, pl. 76, figs 3-8) from the Otway Basin, southern Australia, in having a finer, more evenly distributed sculpture on the equatorial part of the pericyst and in usually being larger. Examples of C. victoriensis studied by Marshall (1988) from the Gippsland Basin with the weaker periphragm sculpture are more difficult to separate from C. packhamii and the most obvious difference is the predominantly larger size of the latter.
Holotype: Marshall, 1990, figs.11A, 23G-H
Locus typicus: Southeastern Australia
Stratum typicum: Campanian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Marshall, 1990, p.20, 22]:
Description:
Ventrodorsal outline elongate subpentagonal. Lateral margins on epicyst tapering towards apex, or more commonly, modified by 2 rounded shoulders. Apex bearing a prominent apical horn with a rounded tip. Lateral margins on hypocyst tapering towards 2 antapical horns: left horn subtriangular, right horn indicated by a weak to distinct rounded bulge. Cysts bicavate, often with isolated pericoels below paracingular ridges. Ventrodorsal outline of endocyst subcircular to ovoidal, width greater than length.
Endophragm surface usually with fine grana or rods up to 0.5 µm wide and 2.0 µm high. Sculptural elements isolated or fused to form discontinuous rugulae. Rods occasionally extremely fine, densely packed, and linked distally, producing a fibrous layer. Periphragm scabrate to finely granulate equatorially: grana less than 0.5 µm high and wide, becoming scabrate towards the poles.
Paracingulum partite, marked by 2 parallel rows of ridges 6-8 µm apart with smooth, irregular, or denticulate crests.
Periarcheopyle Type la, isodeltaform to isothetaform, operculum usually attached along its posterior margin. Endoarcheopyle often indicated by a transverse split between adjoining boundaries of paraplates 2-4" and 1-3a, and frequently, by additional incomplete sutures between adjoining margins of paraplates 1-3a (Fig. 12D).
Dimensions:
Pericyst length 115(158)194 µm width 74(84)100 µm; endocyst length 49(65)80 µm, width 67(79)96 µm (19 specimens).
Affinities:
There is considerable variation in the length of the apical and antapical horns and development of shoulders on either side of the apex (fig.11). The most common forms encountered are similar to those in Fig. 11A-E. The ornament on both wall layers is also variable, and examples with the coarser endophragm sculpture also have the coarser periphragm sculpture.
Chatangiella packhamii is similar to C. tripartita (Cookson and Eisenack) Lentin and Williams 1976, but differs in being larger and having a more prominent sculpture on the periphragm. It is distinguished from the specimens of C. victoriensis (Cookson & Manum) Lentin and Williams 1976 recorded by Cookson and Manum (1964, p. 522, pl. 76, figs 3-8) from the Otway Basin, southern Australia, in having a finer, more evenly distributed sculpture on the equatorial part of the pericyst and in usually being larger. Examples of C. victoriensis studied by Marshall (1988) from the Gippsland Basin with the weaker periphragm sculpture are more difficult to separate from C. packhamii and the most obvious difference is the predominantly larger size of the latter.