Back
Aptea plera
From Fensome et al., 2019:
Aptea plera, Duxbury, 1983, p.22,25, pl.1, figs.7–8,11; pl.10, fig.3; text-figs.5–6.
Holotype: Duxbury, 1983, pl.1, fig.7.
NOW Canningia.
Originally Aptea, subsequently Pseudoceratium, thirdly (and now) Canningia.
Age: early Aptian.
Locus typicus: Atherfield section, Isle of Wight, England
---------------------------------------------------------------------------------------------------
Original description: [Duxbury, 1983, p. 22-23]:
Diagnosis:
A large, dorso-ventrally flattened cyst with well-developed right lateral and left antapical horns. Poorly developed left lateral and right antapical horns may be present and the antapex may vary from convex to concave. Short, solid, distally and proximally flaring rods cover paraplate areas and these are distally united by a fine reticulum. Parasutural areas are free of such ornament and a paratabulation pattern of the formula 4", 6", 6c, 6""", 1p, 1"""", 1a.s., 2s may be inferred. The "parasulcal" notch is offset to the left and the archeopyle is apical, formed by detachment of the whole apical series.
Dimensions:
Holotype - 82 x 102 µm. Complete specimens - 131 (125) 113 x 116 (99) 90 µm. Operculum detached - 102 (84) 70 x 116 (96) 75 µm.
Affinities:
The presence of well-defined areas of ornament which express paratabulation in A. plera allows comparisons to be made between this species and other, similar genera and species, particularly with the ceratiacean types described in Wall & Evitt, 1975. In their excellent drawings of Ceratium, Wall & Evitt have illustrated a tabulation of the formula 4", 6", 5-6c, 6""", 1p, 1"""", plus two or more sulcal platelets. The paratabulation pattern of A. plera is almost identical to this and its distribution is remarkably similar to that demonstrated for Ceratium carolinianum in Wall & Evitt, 1975. Their Text-Fig. 5 A and B is reproduced here (Text-Fig. 10) with the apical series deleted so that direct comparisons may be made between the morphology of C. carolinianum and that of A. plera. It is interesting to note that the sulcus in C. carolinianum occupies the comparative position of the two paraplates designated ls and 2s in A. plera. Paraplate ls is equivalent to that small paraplate frequently designated 1""" in gonyaulacacean paratabulation diagrams but its clear homology with part of the sulcus in Ceratium must dictate its being classed as a parasulcal paraplate. Similarly, 2s is probably equivalent to that paraplate frequently termed 1 p.v.
Davey & Verdier (1974, P. 641) have stressed the "typical and characteristic asymmetry" of Aptea which they consider distinguishes that genus from the similar genera Cyclonephelium, Canningia and Tenua. Such asymmetry has prompted the present author to include Aptea plera in that genus. However, that species termed Canningia cf. reticulata in Duxbury, 1977 has been re-examined by the author and, as well as possessing similar body ornament, distal reticular areas and ornament-free pandasutural regions to A. plera, it also has remarkably similar paratabulation and paraplate distribution. In fact, the only relevant difference between A. plera and C. cf. reticulata is the absence in the latter of the "typical and characteristic asymmetry" of Aptea, largely because of its lack of horns or possession of generally shorter horns (see remarks under Cerbia below). The presence or absence of the Aptea asymmetry may prove a difficult criterion to maintain at generic level.
Aptea plera, Duxbury, 1983, p.22,25, pl.1, figs.7–8,11; pl.10, fig.3; text-figs.5–6.
Holotype: Duxbury, 1983, pl.1, fig.7.
NOW Canningia.
Originally Aptea, subsequently Pseudoceratium, thirdly (and now) Canningia.
Age: early Aptian.
Locus typicus: Atherfield section, Isle of Wight, England
---------------------------------------------------------------------------------------------------
Original description: [Duxbury, 1983, p. 22-23]:
Diagnosis:
A large, dorso-ventrally flattened cyst with well-developed right lateral and left antapical horns. Poorly developed left lateral and right antapical horns may be present and the antapex may vary from convex to concave. Short, solid, distally and proximally flaring rods cover paraplate areas and these are distally united by a fine reticulum. Parasutural areas are free of such ornament and a paratabulation pattern of the formula 4", 6", 6c, 6""", 1p, 1"""", 1a.s., 2s may be inferred. The "parasulcal" notch is offset to the left and the archeopyle is apical, formed by detachment of the whole apical series.
Dimensions:
Holotype - 82 x 102 µm. Complete specimens - 131 (125) 113 x 116 (99) 90 µm. Operculum detached - 102 (84) 70 x 116 (96) 75 µm.
Affinities:
The presence of well-defined areas of ornament which express paratabulation in A. plera allows comparisons to be made between this species and other, similar genera and species, particularly with the ceratiacean types described in Wall & Evitt, 1975. In their excellent drawings of Ceratium, Wall & Evitt have illustrated a tabulation of the formula 4", 6", 5-6c, 6""", 1p, 1"""", plus two or more sulcal platelets. The paratabulation pattern of A. plera is almost identical to this and its distribution is remarkably similar to that demonstrated for Ceratium carolinianum in Wall & Evitt, 1975. Their Text-Fig. 5 A and B is reproduced here (Text-Fig. 10) with the apical series deleted so that direct comparisons may be made between the morphology of C. carolinianum and that of A. plera. It is interesting to note that the sulcus in C. carolinianum occupies the comparative position of the two paraplates designated ls and 2s in A. plera. Paraplate ls is equivalent to that small paraplate frequently designated 1""" in gonyaulacacean paratabulation diagrams but its clear homology with part of the sulcus in Ceratium must dictate its being classed as a parasulcal paraplate. Similarly, 2s is probably equivalent to that paraplate frequently termed 1 p.v.
Davey & Verdier (1974, P. 641) have stressed the "typical and characteristic asymmetry" of Aptea which they consider distinguishes that genus from the similar genera Cyclonephelium, Canningia and Tenua. Such asymmetry has prompted the present author to include Aptea plera in that genus. However, that species termed Canningia cf. reticulata in Duxbury, 1977 has been re-examined by the author and, as well as possessing similar body ornament, distal reticular areas and ornament-free pandasutural regions to A. plera, it also has remarkably similar paratabulation and paraplate distribution. In fact, the only relevant difference between A. plera and C. cf. reticulata is the absence in the latter of the "typical and characteristic asymmetry" of Aptea, largely because of its lack of horns or possession of generally shorter horns (see remarks under Cerbia below). The presence or absence of the Aptea asymmetry may prove a difficult criterion to maintain at generic level.