Back
Phthanoperidinium polytrix
Phthanoperidinium polytrix (Benedek, 1972, p.20, pl.6, figs.1a–b) Lentin and Williams, 1976, p.76. Emendation: Benedek and Sarjeant, 1981, p.330–333, as Phthanoperidinium polytrix.
Originally Hystrichogonyaulax, subsequently Phthanoperidinium?, thirdly (and now) Phthanoperidinium. At the time of the transfer, Lentin and Williams, 1976 questionably included this species in Phthanoperidinium. The emendation by Benedek and Sarjeant, 1981 removes the need for a tentative assignment.
Holotype: Benedek, 1972, pl.6, figs.la-b; Benedek and Sarjeant, 1981, fig.2, nos.4,6, fig.6
Paratypes: Benedek, 1972
Locus typicus: Tönisberg, Lower Rhine Embayment, Germany
Stratum typicum: Middle Oligocene
Translation Benedek, 1972: LPP
Original diagnosis: Benedek, 1972, p.20: Hystrichogonyaulax polytrix
A species of Hystrichogonyaulax with hair-like processes on sutures. The stoudy polyedrical capsule is divided by a spiral cingulum in a hypocyst and a epicyst of nearly equal size.
Original description: Benedek, 1972, p.20: Hystrichogonyaulax polytrix
The thin-walled capsule has a granulate surface with irregularly distributed tubercles. Sutural ridges with 6-10 µm long thorns which may be furcate.
Emended Diagnosis: Benedek and Sarjeant 1981, p. 330-333
Cyst proximate, ovoidal, with a broad, rounded apical prominence and rounded antapex. Epitract slightly larger than hypotract. Paratabulation 4", 3a, 7", 7c, 6"", Ipv, 2"". Paracingulum broad, moderately laevorotatory; parasulcus narrow in its epitractal portion, much broader in its hypotractal portion, and divided in its median portion by faint ridges into small paraplates. Sutures between paraplates marked by low ridges, giving rise to well-spaced, flexible gonal and intergonal spines of moderate length, with evexate, swollen or capitate tips. Well-marked penitabular ridges parallel the forms of the paraplates of the precingular and postcingular series: elsewhere the surface is granular, with a scatter of small tubercles. Archaeopyle intercalary, formed by loss of a single paraplate (Type I); archaeopyle index somewhat greater than 0.5: operculum free
Description: Benedek and Sarjeant 1981, p. 330-333
The cyst, with its ovoidal ambitus, rounded apical prominence and short, well-spaced processes, has something of the appearance of a rotund beetle! As in P. coreoides, the distribution of spines on the sutures is irregular; some are gonal and some intergonal, but spines are lacking from some paraplate junctions and many intergonal positions. The spines are shorter (and fewer) on the ventral surface, but are otherwise of fairly consistent length; they exhibit considerable flexibility. The phragma appears to be two-layered, the ridges and spines arising from the periphragm.
Paraplate 1" is narrow, situated in the anterior prolongation of the parasulcus and extending to the apex: 3" is the largest of the apicals. Paraplate 2a is lost in archaeopyle formation; it is intermediate in shape between the "standard" and "broad hexa" forms of Lentin and Williams (1975). The square paraplate posterior to it is, if we have correctly reconstructed the paratabulation, not 4" as is usual in Phthanoperidinium, but 3"; the other precingulars appear of fairly uniform size, though 7" is rather narrow.
The paracingulum forms a laevorotatory spiral such that its two ends differ in anteroposterior position roughly by its breadth. Cingular paraplate Ic is extremely small; 2c and 7c are the smaller c,f the other six cingulars. Immediately posterior to paraplate Ic, a linear strip of the parasulcus is demarcated by a very low ridge; conceivably this demarcates a past (or a potential) extra postcingular paraplate, since there is an area between it and the posterior ventral paraplate corresponding in shape and position to an undeveloped posterior intercalary. Other faint ridges in the mid-ventral region suggest the incomplete development of sulcal paraplates; and a flagellar mark is indented Paraplates I "" and 6"" are the smallest postcingulars, the others being of fairly uniform size. A broad posterior ventral paraplate extends to the antapex on the ventral side; the two antapical paraplates occupy the dorsal side. Penitabular ridges, lower than the crests but broader and in general quite well-marked, parallel in reduced form the shapes of the precingular and postcingular paraplates. Sometimes the resultant "periplates" are relatively small (e.g. paraplate 3"": Fig. 6), sometimes they occupy almost the whole paraplate (e.g. paraplate 6"": Fig. 6) and sometimes they may be only faintly or incompletely developed (e.g. paraplates 3" and 6": Fig. 6).
Dimensions: Holotype: length 40 µm, breadth 26 µm, length of spines c. 8 µm . Range of Dimensions: Length 36-50 µm (mean 40 µm), breadth 24-40 µm (mean 31 µm), length of spines 6-10 µm. Material: 64 specimens
Remarks: Benedek and Sarjeant 1981, p. 330-333
When Lentin and Williams transferred this species to the genus Phthanoperldinium (1976), they did so tentatively, since much remained to be learned about its morphology. Even after our restudy, some hesitation remains about the generic assignation since, if our interpretation is correct, the paratabulation of this species differs from that typical for the genus. In particular, we consider that six, rather than five, postcingulars are developed and that the paraplate posterior to the archaeopyle appears to be 3", not 4" as in other species of this genus. These features would fully justify the erection of a new genus to accommodate this species. However, in view of difficulties encountered in interpreting the specimens examined, we believe that more searching studies are necessary, preferably under the scanning electron microscope, before such a taxonomic step is taken.
The species most similar to Phthanoperidinium? polytrix is unquestionably P. comatum (Morgenroth, 1966b) Lisenack and Kjellstrom, 1971a, from the Lower Oligocene of Germany. However, it differs in paratabulation (there are only five postcingulars and a posterior ventral paraplate is apparently not developed) and in the much greater length and dissimilar form of the processes arising from the crests.
Originally Hystrichogonyaulax, subsequently Phthanoperidinium?, thirdly (and now) Phthanoperidinium. At the time of the transfer, Lentin and Williams, 1976 questionably included this species in Phthanoperidinium. The emendation by Benedek and Sarjeant, 1981 removes the need for a tentative assignment.
Holotype: Benedek, 1972, pl.6, figs.la-b; Benedek and Sarjeant, 1981, fig.2, nos.4,6, fig.6
Paratypes: Benedek, 1972
Locus typicus: Tönisberg, Lower Rhine Embayment, Germany
Stratum typicum: Middle Oligocene
Translation Benedek, 1972: LPP
Original diagnosis: Benedek, 1972, p.20: Hystrichogonyaulax polytrix
A species of Hystrichogonyaulax with hair-like processes on sutures. The stoudy polyedrical capsule is divided by a spiral cingulum in a hypocyst and a epicyst of nearly equal size.
Original description: Benedek, 1972, p.20: Hystrichogonyaulax polytrix
The thin-walled capsule has a granulate surface with irregularly distributed tubercles. Sutural ridges with 6-10 µm long thorns which may be furcate.
Emended Diagnosis: Benedek and Sarjeant 1981, p. 330-333
Cyst proximate, ovoidal, with a broad, rounded apical prominence and rounded antapex. Epitract slightly larger than hypotract. Paratabulation 4", 3a, 7", 7c, 6"", Ipv, 2"". Paracingulum broad, moderately laevorotatory; parasulcus narrow in its epitractal portion, much broader in its hypotractal portion, and divided in its median portion by faint ridges into small paraplates. Sutures between paraplates marked by low ridges, giving rise to well-spaced, flexible gonal and intergonal spines of moderate length, with evexate, swollen or capitate tips. Well-marked penitabular ridges parallel the forms of the paraplates of the precingular and postcingular series: elsewhere the surface is granular, with a scatter of small tubercles. Archaeopyle intercalary, formed by loss of a single paraplate (Type I); archaeopyle index somewhat greater than 0.5: operculum free
Description: Benedek and Sarjeant 1981, p. 330-333
The cyst, with its ovoidal ambitus, rounded apical prominence and short, well-spaced processes, has something of the appearance of a rotund beetle! As in P. coreoides, the distribution of spines on the sutures is irregular; some are gonal and some intergonal, but spines are lacking from some paraplate junctions and many intergonal positions. The spines are shorter (and fewer) on the ventral surface, but are otherwise of fairly consistent length; they exhibit considerable flexibility. The phragma appears to be two-layered, the ridges and spines arising from the periphragm.
Paraplate 1" is narrow, situated in the anterior prolongation of the parasulcus and extending to the apex: 3" is the largest of the apicals. Paraplate 2a is lost in archaeopyle formation; it is intermediate in shape between the "standard" and "broad hexa" forms of Lentin and Williams (1975). The square paraplate posterior to it is, if we have correctly reconstructed the paratabulation, not 4" as is usual in Phthanoperidinium, but 3"; the other precingulars appear of fairly uniform size, though 7" is rather narrow.
The paracingulum forms a laevorotatory spiral such that its two ends differ in anteroposterior position roughly by its breadth. Cingular paraplate Ic is extremely small; 2c and 7c are the smaller c,f the other six cingulars. Immediately posterior to paraplate Ic, a linear strip of the parasulcus is demarcated by a very low ridge; conceivably this demarcates a past (or a potential) extra postcingular paraplate, since there is an area between it and the posterior ventral paraplate corresponding in shape and position to an undeveloped posterior intercalary. Other faint ridges in the mid-ventral region suggest the incomplete development of sulcal paraplates; and a flagellar mark is indented Paraplates I "" and 6"" are the smallest postcingulars, the others being of fairly uniform size. A broad posterior ventral paraplate extends to the antapex on the ventral side; the two antapical paraplates occupy the dorsal side. Penitabular ridges, lower than the crests but broader and in general quite well-marked, parallel in reduced form the shapes of the precingular and postcingular paraplates. Sometimes the resultant "periplates" are relatively small (e.g. paraplate 3"": Fig. 6), sometimes they occupy almost the whole paraplate (e.g. paraplate 6"": Fig. 6) and sometimes they may be only faintly or incompletely developed (e.g. paraplates 3" and 6": Fig. 6).
Dimensions: Holotype: length 40 µm, breadth 26 µm, length of spines c. 8 µm . Range of Dimensions: Length 36-50 µm (mean 40 µm), breadth 24-40 µm (mean 31 µm), length of spines 6-10 µm. Material: 64 specimens
Remarks: Benedek and Sarjeant 1981, p. 330-333
When Lentin and Williams transferred this species to the genus Phthanoperldinium (1976), they did so tentatively, since much remained to be learned about its morphology. Even after our restudy, some hesitation remains about the generic assignation since, if our interpretation is correct, the paratabulation of this species differs from that typical for the genus. In particular, we consider that six, rather than five, postcingulars are developed and that the paraplate posterior to the archaeopyle appears to be 3", not 4" as in other species of this genus. These features would fully justify the erection of a new genus to accommodate this species. However, in view of difficulties encountered in interpreting the specimens examined, we believe that more searching studies are necessary, preferably under the scanning electron microscope, before such a taxonomic step is taken.
The species most similar to Phthanoperidinium? polytrix is unquestionably P. comatum (Morgenroth, 1966b) Lisenack and Kjellstrom, 1971a, from the Lower Oligocene of Germany. However, it differs in paratabulation (there are only five postcingulars and a posterior ventral paraplate is apparently not developed) and in the much greater length and dissimilar form of the processes arising from the crests.