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Deflandrea webbii
From Fensome et al., 2019:
Deflandrea webbii Wrenn and Hart, 1988, p.352–353, fig.22, nos.2–4, fig.23, nos.4–5, fig.40, nos.1–4, fig.41 nos.1–4, fig.42,
no.2. Holotype: Wrenn and Hart, 1988, fig.22, nos.2–4. Age: Eocene.
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Original description: [Wrenn and Hart, 1988]:
Deflandrea webbii sp. nov.
Figures 22.2-4, 23.4-5, 40.1-4, 41.1-4, 42.2
Deflandrea antarctica Wilson, 1967, pro parte, Goodman and Ford, 1983, p. 864.
Diagnosis. A species of Deflandrea bearing well-developed pandasutural striae that delineate paraplate boundaries. Intraparaplate areas are reticulate and bear verracae that may mark the location of trichocyst pores on the theca. A complex flagellar scar lies on the ventral surface at the intersection of the parasulcus and the paracingulum.
Description.
Shape: The pericyst is peridinioid in outline, whereas the shape of the endocyst varies from subcircular to subpentagonal in outline. The hypocyst bears two short antapical horns. The antapex may be truncated or slightly concave. The length of the apical horn varies.
Phragma: The thin periphragm (<0.5 μm) is divided into paraplates by pandasutural striae that may be as much as 17 μm wide. The paraplates are irregularly reticulate and bear scattered verrucae that may correspond to trichocyst pores on the original thecae. The endophragm is
granular and nontabulate.
Paratabulation: Pandasutural striae are well developed, and delineate a paratabulation of 4', ?3a, 7", 6-7C, 5'", 2"", ?5S.
Paracingulum: The paracingulum is laevorotatory and offset approximately the width of the paracingulum. The paracingulum is variably incised, bordered by low denticulate ridges and divided into six or seven paraplates by pandasutural striae. The paraplates within the paracingulum are reticulate and bear verrucae.
Parasulcus: The parasulcal depression widens posteriorly and is bordered by low pandasutural striae. As many as five parasulcal paraplates are delineated by pandasutural striae. A complex flagellar scar is present in the parasulcal area just posterior of the paracingulum. The right parasulcal paraplate projects over the flagellar scar and is convex toward the sulcus; i.e., toward the specimen's left.
Archeopyle: The broad hexa 2a archeopyle appears to be Type I/I; some specimens, however, suggest a Type I/3I archeopyle. Free, broad hexa 2a (I/I) opercula bearing pandasutural striae along parasutures H2- H6 have been observed. The endoperculum remains attached to the
perioperculum. No free 1a or 3a paraplates have been observed, nor have opercula composed of paraplates 1a, 2a, and 3a. This strongly suggests that the archeopyle is Type I/I and not a Type I/31.
Dimensions. Observed range (six specimens): pericyst length, 81 to 110 μm (mean, 94 μm); pericyst width, 68 to 77 μm (mean, 72 μm);
endocyst length, 51 to 80 μm (mean, 63 μm); endocyst width, 50 to 76 μm (mean, 66 μm); endoarcheopyle height, 12 to 22 μm (mean, 15
μm); endoarcheopyle width, 34 to 48 μm (mean, 42 μm). Periarcheopyle (1 measurable specimen): length, 28 μm; width, 46 μm.
Discussion and Comparison with Similar Forms.
The distinctive characteristics of Deflandrea webbii sp. nov. are the presence of pandasutural striae, reticulate intraparaplate areas bearing verrucae, and a very complex flagellar scar. One of us has observed very faint and scattered pandasutural striae on D. phosphoritica (J. H. Wrenn, unpublished data) but never so distinctly or completely developed as that on D. webbii sp. nov.
The flagellar scar is morphologically complex, and the flap that projects over it appears to protect one or more pores. If the pores were the functional site of flagellar insertion, Deflandrea webbii sp. nov. is not a cyst but a schizont. This interpretation is supported by the fact that the
pandasutural striae are not mere surface features. The striae actually run under the surface paraplate reticulation (Fig. 41.1,3), just as they would if they had been formed by wall growth. The overall shape and the flat truncated antapex observed on some specimens is similar to that of D. antarctica. However, D. webbi sp. nov. differs in having distinctive surface sculpture, a consistently thinner endophragm and by never developing paratabular grana or spines like those on D. antarctica.
Holotype. Slide 8511, 117.8 × 7.9 (G23), E/1. Sample 8511. Section 19, La Meseta Formation, middle to late Eocene, Seymour Island, Antarctica.
Stratigraphic Occurrence. La Meseta Formation (Section 3, late early Eocene; Section 19, middle to late Eocene).
Selected Previous Occurrences. Atlantic Ocean, Falkland Plateau, DSDP 511 (middle Eocene-early Oligocene: Goodman and Ford, 1983;
as Deflandrea antarctica, in part).
Derivation of Name. Deflandrea webbi sp. nov. named after Peter N. Webb in recognition of his pioneering contributions to Antarctic micropaleontology.
Deflandrea webbii Wrenn and Hart, 1988, p.352–353, fig.22, nos.2–4, fig.23, nos.4–5, fig.40, nos.1–4, fig.41 nos.1–4, fig.42,
no.2. Holotype: Wrenn and Hart, 1988, fig.22, nos.2–4. Age: Eocene.
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Original description: [Wrenn and Hart, 1988]:
Deflandrea webbii sp. nov.
Figures 22.2-4, 23.4-5, 40.1-4, 41.1-4, 42.2
Deflandrea antarctica Wilson, 1967, pro parte, Goodman and Ford, 1983, p. 864.
Diagnosis. A species of Deflandrea bearing well-developed pandasutural striae that delineate paraplate boundaries. Intraparaplate areas are reticulate and bear verracae that may mark the location of trichocyst pores on the theca. A complex flagellar scar lies on the ventral surface at the intersection of the parasulcus and the paracingulum.
Description.
Shape: The pericyst is peridinioid in outline, whereas the shape of the endocyst varies from subcircular to subpentagonal in outline. The hypocyst bears two short antapical horns. The antapex may be truncated or slightly concave. The length of the apical horn varies.
Phragma: The thin periphragm (<0.5 μm) is divided into paraplates by pandasutural striae that may be as much as 17 μm wide. The paraplates are irregularly reticulate and bear scattered verrucae that may correspond to trichocyst pores on the original thecae. The endophragm is
granular and nontabulate.
Paratabulation: Pandasutural striae are well developed, and delineate a paratabulation of 4', ?3a, 7", 6-7C, 5'", 2"", ?5S.
Paracingulum: The paracingulum is laevorotatory and offset approximately the width of the paracingulum. The paracingulum is variably incised, bordered by low denticulate ridges and divided into six or seven paraplates by pandasutural striae. The paraplates within the paracingulum are reticulate and bear verrucae.
Parasulcus: The parasulcal depression widens posteriorly and is bordered by low pandasutural striae. As many as five parasulcal paraplates are delineated by pandasutural striae. A complex flagellar scar is present in the parasulcal area just posterior of the paracingulum. The right parasulcal paraplate projects over the flagellar scar and is convex toward the sulcus; i.e., toward the specimen's left.
Archeopyle: The broad hexa 2a archeopyle appears to be Type I/I; some specimens, however, suggest a Type I/3I archeopyle. Free, broad hexa 2a (I/I) opercula bearing pandasutural striae along parasutures H2- H6 have been observed. The endoperculum remains attached to the
perioperculum. No free 1a or 3a paraplates have been observed, nor have opercula composed of paraplates 1a, 2a, and 3a. This strongly suggests that the archeopyle is Type I/I and not a Type I/31.
Dimensions. Observed range (six specimens): pericyst length, 81 to 110 μm (mean, 94 μm); pericyst width, 68 to 77 μm (mean, 72 μm);
endocyst length, 51 to 80 μm (mean, 63 μm); endocyst width, 50 to 76 μm (mean, 66 μm); endoarcheopyle height, 12 to 22 μm (mean, 15
μm); endoarcheopyle width, 34 to 48 μm (mean, 42 μm). Periarcheopyle (1 measurable specimen): length, 28 μm; width, 46 μm.
Discussion and Comparison with Similar Forms.
The distinctive characteristics of Deflandrea webbii sp. nov. are the presence of pandasutural striae, reticulate intraparaplate areas bearing verrucae, and a very complex flagellar scar. One of us has observed very faint and scattered pandasutural striae on D. phosphoritica (J. H. Wrenn, unpublished data) but never so distinctly or completely developed as that on D. webbii sp. nov.
The flagellar scar is morphologically complex, and the flap that projects over it appears to protect one or more pores. If the pores were the functional site of flagellar insertion, Deflandrea webbii sp. nov. is not a cyst but a schizont. This interpretation is supported by the fact that the
pandasutural striae are not mere surface features. The striae actually run under the surface paraplate reticulation (Fig. 41.1,3), just as they would if they had been formed by wall growth. The overall shape and the flat truncated antapex observed on some specimens is similar to that of D. antarctica. However, D. webbi sp. nov. differs in having distinctive surface sculpture, a consistently thinner endophragm and by never developing paratabular grana or spines like those on D. antarctica.
Holotype. Slide 8511, 117.8 × 7.9 (G23), E/1. Sample 8511. Section 19, La Meseta Formation, middle to late Eocene, Seymour Island, Antarctica.
Stratigraphic Occurrence. La Meseta Formation (Section 3, late early Eocene; Section 19, middle to late Eocene).
Selected Previous Occurrences. Atlantic Ocean, Falkland Plateau, DSDP 511 (middle Eocene-early Oligocene: Goodman and Ford, 1983;
as Deflandrea antarctica, in part).
Derivation of Name. Deflandrea webbi sp. nov. named after Peter N. Webb in recognition of his pioneering contributions to Antarctic micropaleontology.