Back
Palaeostomocystis senilis
Palaeostomocystis senilis McIntyre and Brideaux, 1980
Now Fromea. Originally Palaeostomocystis, subsequently (and now) Fromea.
Holotype: McIntyre and Brideaux, pl.5, fig.12; pl.6, fig.1
Locus typicus: Martin Creek, District of Mackenzie, Canada
Stratum typicum: Valanginian
Original diagnosis: McIntyre and Brideaux, p. 18
Shape: Autocyst - Ambitus ovoid, the length/width ratio from 1.11 to 1.96 (mean 1.54); apex and antapex rounded, maximum diameter at or near mid-latitude of
autocyst; extreme compresslon.
Phragma: Autophragm - About 0.5 Ám thick; surface sculpture pattern a complex densely spaced anastomosing network of minute folds or obvermiculate ridges from
2-12 Ám long and up to 0.5 Ám wide and high.
Paratabulation: Autophragm - Evidence for paratabulation lacking except in the vicinity of the archeopyle where faint indications are denoted by weakly
developed angularity and, in places on some specimens, weakly developed accessory ?precingular parasutures. Autocingulum - Present, denoted by a peristent pattern of several major folds near the mid-latitude of the autocyst; folds on some specimens pass laterally into an ill-defined pair of parasutural ridges near the ambitus of the autocyst, and on several specimens the folds are associated with slight invaginations of the autocyst at the periphery. Autosulcus - Not observed.
Archeopyle: Apical, Type A(?1"-4"). Operculum not observed, presumably simple and free.
Dimensions: Autocyst length - 108-212 Ám (mean, 157 Ám), width - 90-156 Ám (mean, 110 Ám).
Affinities:
McIntyre and Brideaux, 1980, p. 18: Fromea fragilis (Cookson and Eisenack) Stover
and Evitt, 1978, differs in possessing a smooth or scabrate autophragm, generally has a smaller mean length and width and does not exhibit the consistent set of transverse folds in the latitude of the autocingulum.
Now Fromea. Originally Palaeostomocystis, subsequently (and now) Fromea.
Holotype: McIntyre and Brideaux, pl.5, fig.12; pl.6, fig.1
Locus typicus: Martin Creek, District of Mackenzie, Canada
Stratum typicum: Valanginian
Original diagnosis: McIntyre and Brideaux, p. 18
Shape: Autocyst - Ambitus ovoid, the length/width ratio from 1.11 to 1.96 (mean 1.54); apex and antapex rounded, maximum diameter at or near mid-latitude of
autocyst; extreme compresslon.
Phragma: Autophragm - About 0.5 Ám thick; surface sculpture pattern a complex densely spaced anastomosing network of minute folds or obvermiculate ridges from
2-12 Ám long and up to 0.5 Ám wide and high.
Paratabulation: Autophragm - Evidence for paratabulation lacking except in the vicinity of the archeopyle where faint indications are denoted by weakly
developed angularity and, in places on some specimens, weakly developed accessory ?precingular parasutures. Autocingulum - Present, denoted by a peristent pattern of several major folds near the mid-latitude of the autocyst; folds on some specimens pass laterally into an ill-defined pair of parasutural ridges near the ambitus of the autocyst, and on several specimens the folds are associated with slight invaginations of the autocyst at the periphery. Autosulcus - Not observed.
Archeopyle: Apical, Type A(?1"-4"). Operculum not observed, presumably simple and free.
Dimensions: Autocyst length - 108-212 Ám (mean, 157 Ám), width - 90-156 Ám (mean, 110 Ám).
Affinities:
McIntyre and Brideaux, 1980, p. 18: Fromea fragilis (Cookson and Eisenack) Stover
and Evitt, 1978, differs in possessing a smooth or scabrate autophragm, generally has a smaller mean length and width and does not exhibit the consistent set of transverse folds in the latitude of the autocingulum.