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Hystrichosphaeropsis somphosa
Hystrichosphaeropsis somphosa Warny and Wrenn 1997
Holotype: Warny and Wrenn 1997: Plate I, 1 -4
Type locality: Bou Regreg S Core, Sale, Riffian Corridor, Morocco.
Stratum typicum: Messinian
Stratigraphic range: Messinian/latest Miocene
Original diagnosis: Warny and Wrenn 1997, p. 284-287
A species of Hystrichosphaeropsis whose periphragm is consistently perforate, to a greater or lesser degree, particularly on the hypocyst. The holes vary widely in size, with some of the largest fenestrations representing sulcal and posterior intercalary paraplates. The antapical paraplates are represented by a large antapical opening formed by the hypocystal periphragm that flares out like a skirt (see Plate I, 1-3; Plate II, 6-9).
Description: Warny and Wrenn 1997, p. 284-287
Shape: Cyst bicavate and suturocavate. The pericyst shape is ellipsoidal to polygonal, reminiscent of an obelisk in some specimens. The epicyst bears a well-developed but short horn that generally occurs near the apex, though displaced ventrally rather than on the true apex of the cyst. Many specimens have a widely flared anterior periphragm, similar to a cowl or a monk"s hood, that extends up the sides and above the archeopyle. The hypocyst may be distally flared, forming a quadrate hypocystal structure that is open antapically. The subspherical to ellipsoidal endocyst may bear a small (see Plate II, 5) apical protrusion comparable in position to the horn on the pericyst. On rare specimens, the sub-apical horn of the pericyst and the sub-apical protrusion of the endocyst are joined, forming a biconical sub-apical tube that connects the pericyst and endocyst. Phragma: The endophragm is smooth to slightly granular. The smooth periphragm is typically perforated by holes ranging in size from 3 to 15 Ám in diameter. Some holes delimit paraplates, others appear to be randomly distributed. The cysts are bicavate and suturocavate. Where the periphragm and endophragm are in contact, they appressed in the center of paraplates. The antapical paraplate (4"") which is represented by the open end of the antapical pericyst. The hypocyst typically bears two large holes or fenestrations on the ventral antapical surface. These represent the 1P and the PS paraplates; the larger of the two plates is the 1P paraplate. Some specimens exhibit extreme separation of the endo- and periphragm, similar to that observed on Galeacysta etrusca (Corradini and Biffi, 1988). Archeopyle: The archeopyle is precingular, Type P (3" only). Paratabulation: Most of the paratabulation is clearly delimited by the suturocavate septa or fenestrations in the periphragm. Paratabulation formula is: 5" 6" 6C 6"" 1P 1"", PS. Other parasulcal plates are not clearly differentiated. Paracingulum: The paracingulum is well defined by suturocavate septa bordering transversely elongate areas where the periphragm and the endophragm are closely appressed. The laevorotatory paracingulum is offset in a posterior/anterior direction, a distance equal to two times the width of the paracingulum. Parasulcus: The parasulcus is generally undivided, but the posterior parasulcal (PS) plate is represented by a large fenestration at the posterior end of the pericyst.
Dimensions: Holotype: Length of endocyst 47.6Ám, length of pericyst 96.9Ám, width of endo- and pericyst 47.6Ám. Mean (x) and extreme values for n=22: length of endocyst 41.6-(47.9)-52.7Ám, length of pericyst 71.4-(90.2) -102.0Ám, width of endo- and pericyst at the cingulum 38.3-(43.3)-54.4Ám.
Comparison: The overall appearance and shape of Hystrichosphaeropsis somphosa is very similar to H. obscura Habib (Habib, 1972), but differs by having a highly perforated periphragm and well delimited paratabulation.
Comments: Warny and Wrenn 1997, p. 284-287
It is interesting to note that this unusual dinocyst, characterised by a perforated periphragm, existed during the Messinian (latest Miocene) in the western Mediterranean Sea. At precisely the same time, but in the north central Mediterranean Sea, another fenestrate species (e.g., Galeacysta etrusca Corradini et Biffi, 1988) was present. Is it possible that environmental conditions were in some way involved in initiating this unusual morphology simultaneously in two different dinocyst lineages? This supposition is reinforced by the occurrence in the upper Quaternary of the Black Sea of Spiniferites cruciformis ( Wall and Dale, 1973), another species characterised by a perforated phragma. Concerning this species, the ornamentation is also typically most pronounced at the antapex and less in the ventral area. In this case, the perforations could possibly be linked to the influx of glacial melt water, which induced the fresh- or brackish-water environment of the Black Sea (Wall and Dale, 1973). The morphology of tll-s perforated taxa seems to be linked to abnormal salinity conditions.
Holotype: Warny and Wrenn 1997: Plate I, 1 -4
Type locality: Bou Regreg S Core, Sale, Riffian Corridor, Morocco.
Stratum typicum: Messinian
Stratigraphic range: Messinian/latest Miocene
Original diagnosis: Warny and Wrenn 1997, p. 284-287
A species of Hystrichosphaeropsis whose periphragm is consistently perforate, to a greater or lesser degree, particularly on the hypocyst. The holes vary widely in size, with some of the largest fenestrations representing sulcal and posterior intercalary paraplates. The antapical paraplates are represented by a large antapical opening formed by the hypocystal periphragm that flares out like a skirt (see Plate I, 1-3; Plate II, 6-9).
Description: Warny and Wrenn 1997, p. 284-287
Shape: Cyst bicavate and suturocavate. The pericyst shape is ellipsoidal to polygonal, reminiscent of an obelisk in some specimens. The epicyst bears a well-developed but short horn that generally occurs near the apex, though displaced ventrally rather than on the true apex of the cyst. Many specimens have a widely flared anterior periphragm, similar to a cowl or a monk"s hood, that extends up the sides and above the archeopyle. The hypocyst may be distally flared, forming a quadrate hypocystal structure that is open antapically. The subspherical to ellipsoidal endocyst may bear a small (see Plate II, 5) apical protrusion comparable in position to the horn on the pericyst. On rare specimens, the sub-apical horn of the pericyst and the sub-apical protrusion of the endocyst are joined, forming a biconical sub-apical tube that connects the pericyst and endocyst. Phragma: The endophragm is smooth to slightly granular. The smooth periphragm is typically perforated by holes ranging in size from 3 to 15 Ám in diameter. Some holes delimit paraplates, others appear to be randomly distributed. The cysts are bicavate and suturocavate. Where the periphragm and endophragm are in contact, they appressed in the center of paraplates. The antapical paraplate (4"") which is represented by the open end of the antapical pericyst. The hypocyst typically bears two large holes or fenestrations on the ventral antapical surface. These represent the 1P and the PS paraplates; the larger of the two plates is the 1P paraplate. Some specimens exhibit extreme separation of the endo- and periphragm, similar to that observed on Galeacysta etrusca (Corradini and Biffi, 1988). Archeopyle: The archeopyle is precingular, Type P (3" only). Paratabulation: Most of the paratabulation is clearly delimited by the suturocavate septa or fenestrations in the periphragm. Paratabulation formula is: 5" 6" 6C 6"" 1P 1"", PS. Other parasulcal plates are not clearly differentiated. Paracingulum: The paracingulum is well defined by suturocavate septa bordering transversely elongate areas where the periphragm and the endophragm are closely appressed. The laevorotatory paracingulum is offset in a posterior/anterior direction, a distance equal to two times the width of the paracingulum. Parasulcus: The parasulcus is generally undivided, but the posterior parasulcal (PS) plate is represented by a large fenestration at the posterior end of the pericyst.
Dimensions: Holotype: Length of endocyst 47.6Ám, length of pericyst 96.9Ám, width of endo- and pericyst 47.6Ám. Mean (x) and extreme values for n=22: length of endocyst 41.6-(47.9)-52.7Ám, length of pericyst 71.4-(90.2) -102.0Ám, width of endo- and pericyst at the cingulum 38.3-(43.3)-54.4Ám.
Comparison: The overall appearance and shape of Hystrichosphaeropsis somphosa is very similar to H. obscura Habib (Habib, 1972), but differs by having a highly perforated periphragm and well delimited paratabulation.
Comments: Warny and Wrenn 1997, p. 284-287
It is interesting to note that this unusual dinocyst, characterised by a perforated periphragm, existed during the Messinian (latest Miocene) in the western Mediterranean Sea. At precisely the same time, but in the north central Mediterranean Sea, another fenestrate species (e.g., Galeacysta etrusca Corradini et Biffi, 1988) was present. Is it possible that environmental conditions were in some way involved in initiating this unusual morphology simultaneously in two different dinocyst lineages? This supposition is reinforced by the occurrence in the upper Quaternary of the Black Sea of Spiniferites cruciformis ( Wall and Dale, 1973), another species characterised by a perforated phragma. Concerning this species, the ornamentation is also typically most pronounced at the antapex and less in the ventral area. In this case, the perforations could possibly be linked to the influx of glacial melt water, which induced the fresh- or brackish-water environment of the Black Sea (Wall and Dale, 1973). The morphology of tll-s perforated taxa seems to be linked to abnormal salinity conditions.