Back
Fromea senilis
Fromea senilis (McIntyre and Brideaux, 1980) Lentin and Williams, 1981
Originally Palaeostomocystis, subsequently (and now) Fromea.
Poulton et al., 1992, noted that the specimens of this species found in the Valanginian are probably recycled.
Holotype: McIntyre and Brideaux, 1980, 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: Palaeostomocystis senilis
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 compression.
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: Palaeostomocystis senilis
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.
Originally Palaeostomocystis, subsequently (and now) Fromea.
Poulton et al., 1992, noted that the specimens of this species found in the Valanginian are probably recycled.
Holotype: McIntyre and Brideaux, 1980, 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: Palaeostomocystis senilis
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 compression.
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: Palaeostomocystis senilis
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.