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Liesbergia abdounensis
Liesbergia abdounensis Soncini, 1992
Holotype: Soncini, 1992, pl.2, figs.4-6
Paratypes: Soncini, 1992
Locus typicus: Abdoun, Morocco
Stratum typicum: Ypresian
Original diagnosis: Soncini, 1992, p.332
Proximate, acavate, subspherical to subpolygonal cyst. Prominent truncated apical horn, broad-based, consisting of anastomosed trabeculae. External surface of autophragm covered by a dense pilate or clavate ornamentation, with occasional distal connections. Basal part of autophragm generally slightly protruding into the apical trabecular structure. Complete paratabulation underlined by ridges of distally linked projections, higher than intratabular ornamentation. Gonyaulacoid sexiform, Gonyaulacysta-type arrangement of paraplates. Distinctive topology of ventral area: A contacts ai, li narrow, roughly triangular, not in contact with lu, A larger than lu. Archeopyle P(4), operculum free.
Dimensions: holotype maximum length: 104.5 µm, maximum width: 81 µm, apical horn: 14 µm; range maximum length including apical horn: 70-105 µm (89 µm), maximum width: 60-85 µm (71 µm), maximum length of apical horn, between wall and tip of projections: 7-19 µm (12.5 µm); thickness of wall including surface"s ornamentation: 2-4 µm; parasutural ridges: 4.5-5.5 µm; 15 specimens measured.
Original description: Soncini, 1992, p.332
Moroccan cysts described here are proximate, acavate, subspherical to subpolygonal in outline; the hypocyst is rounded, and the epicyst is subconical (Plate II, 2). The prominent apical horn is variable in length, with a broad basis and a truncated tip. It consists exclusively of anastomosing"trabeculae, coming from the elongated elements of ornamentation (Fig.5). Autophragm bears a dense ornamentation on external surface (Plate II, 9), formed by short projections with rounded tips, that can be simple, bifurcate, and sometimes distally linked (Fig.5), drawing an irregular reticulate and granulate patterning in high focus observation. No continuous external layer can be delimited. The basal part of the autophragm generally shows a small protrusion into the apical anastomosed trabeculae structure (variable character) (Plate II, 9). A narrow paracingulum is delimited by two ridges formed by anastomosing and/or distally linked projections. The parasulcus is slightly hollow, with an ornamentation of lower relief. Archeopyle is of type P(4), the operculum is free. All the parasutures are underlined by ridges of irregular height7 higher than intratabular ornamentation (Plate Il, 2, 4-8) and composed of distally linked projections.
Paratabulation is Gonyaulacoid, of Gonyaulacysta-type (Fig.6). The apical area has not been observed; A/l u, B/C. C/A parasutures all disappear in the apical trabeculate network of the horn (Plate II, 9). There is a 6-sided central antapical paraplate Y (sexiform), probably in symmetrical arrangement (cf. text-fig. 2, Helenes, 1986). The ventral area seems to show a sigmoidal sulcus: S-type organization (Evitt, 1985). The arrangement of paraplates on ventral epicyst is hardly discernible (Plate II, 7), but li is evidently narrow, roughly triangular-shaped and clearly not in contact with lu. Consequently, A contacts ai: A/ai arrangement (Helenes, 1986). A is larger than lu, and there is no obliteration of their parasuture. Ii, Im, Iu are not distinct. Complete paratabulation of precingular, paracingular and postcingular areas have been observed (Fig.6).
Affinities:
Soncini, 1992, p. 332-333: At first sight, the moroccan dinocysts described could be assigned to the genus Apteodinium (Eisenack) Lucas-Clark 1987, due to the general outline, the prominent apical horn, the complexity of the wall with a microreticulate to spongy aspect according to the focus level, and the paratabulation hardly discernible. The best comparison could be made with A. granulatum (Eisenack) Lucas-Clark 1987. However, the distal network of trabeculae linking tips of adjacent pila or clava is here much less dense than on any Apteodinium species. No true outer layer can be delineated at high magnification, even discontinuous (Plate II, 9). The autophragm is variously ornamented but not 2 or 3-layered as described by Lucas-Clark (1987) for A. granulatum. Consequently, it seems unappropriate to consider the apical horn as a "cavation", as Sarjeant (1985) does about A. granulatum. The apical horn is here a projection of trabeculae, more or less loosely linked together (Fig.5). Although it is hardly discernible, paratabulation pattern has been partially reconstructed (Fig.6). It shows a typical affinity with Gonyaulax-type cysts, permanently excluding the attribution to any Apteodinium or Aldorfia species (cf. Cribroperidinium and Aptiana- Ventriosum Complex, Helenes, 1986; Lucas-Clark, 1987). Among Evitt"s Leprodinium Complex (1985), Acanthaulax is the most appropriate genus to compare moroccan specimens with, although these do not show any spine on parasuttural ridges or in intratabular ornamentation (Sarjeant, in Davey el al., 1966). The characteristic "dense spine cover" (Sarjeant, in Davey et al., 1966) is here a dense (simple or bifurcate) pila or clava cover. Moreover, the genus Liesbergia Berger 1986 has been erected to differentiate Acanthaulax-type cysts with a highly distinctive apical horn "only formed by development of the external ornamentation and not the entire periphragm" (Berger, 1986). Except the nature of ornamentation on the cyst surface (and their stratigraphic distribution).
L. scarburghensis (Sarjeant) Berger 1986 and moroccan cysts are quite similar, both showing "an irregular reticulate patterning" (Sarjeant, 1961) in over view of the wall surface, made of spiny projections more or less linked together on the former (low ridges described by Sarjeant, 1961), made of rounded projections (clava or pila) with, sometimes, connected tips on the latter. L. Iiesberghensis Berger 1986 differs from L. ahdounensis in having a scattered ornamentation and fewer trabeculae building the apical horn.
About the characteristics of the genus Liesbergia, Berger"s diagnosis lacks information about paraplates arrangements. A reexamination of Liesbergia type material should be of great interest to compare Paleogene and Jurassic specimens.
Remark: The stratigraphic gap between L. Iiesbergensis and L. scarburghensis (Oxfordian) and L. abdounensis (Thanetian-Ypresian) may be filled, perhaps, with a systematic review of all socalled Apteodinium cysts at high magnification: presumed non-tabulate taxa often prove to be "cryptotabulate" in fact. Then, one could discover some "Apteodinium" specimens with a paratabulation pattern not belonging to Aptiana-Ventriosum Complex but to Gonyaulacysta-type, during the Cretaceous interval. Perhaps new species of Liesbergia could then be erected.
Holotype: Soncini, 1992, pl.2, figs.4-6
Paratypes: Soncini, 1992
Locus typicus: Abdoun, Morocco
Stratum typicum: Ypresian
Original diagnosis: Soncini, 1992, p.332
Proximate, acavate, subspherical to subpolygonal cyst. Prominent truncated apical horn, broad-based, consisting of anastomosed trabeculae. External surface of autophragm covered by a dense pilate or clavate ornamentation, with occasional distal connections. Basal part of autophragm generally slightly protruding into the apical trabecular structure. Complete paratabulation underlined by ridges of distally linked projections, higher than intratabular ornamentation. Gonyaulacoid sexiform, Gonyaulacysta-type arrangement of paraplates. Distinctive topology of ventral area: A contacts ai, li narrow, roughly triangular, not in contact with lu, A larger than lu. Archeopyle P(4), operculum free.
Dimensions: holotype maximum length: 104.5 µm, maximum width: 81 µm, apical horn: 14 µm; range maximum length including apical horn: 70-105 µm (89 µm), maximum width: 60-85 µm (71 µm), maximum length of apical horn, between wall and tip of projections: 7-19 µm (12.5 µm); thickness of wall including surface"s ornamentation: 2-4 µm; parasutural ridges: 4.5-5.5 µm; 15 specimens measured.
Original description: Soncini, 1992, p.332
Moroccan cysts described here are proximate, acavate, subspherical to subpolygonal in outline; the hypocyst is rounded, and the epicyst is subconical (Plate II, 2). The prominent apical horn is variable in length, with a broad basis and a truncated tip. It consists exclusively of anastomosing"trabeculae, coming from the elongated elements of ornamentation (Fig.5). Autophragm bears a dense ornamentation on external surface (Plate II, 9), formed by short projections with rounded tips, that can be simple, bifurcate, and sometimes distally linked (Fig.5), drawing an irregular reticulate and granulate patterning in high focus observation. No continuous external layer can be delimited. The basal part of the autophragm generally shows a small protrusion into the apical anastomosed trabeculae structure (variable character) (Plate II, 9). A narrow paracingulum is delimited by two ridges formed by anastomosing and/or distally linked projections. The parasulcus is slightly hollow, with an ornamentation of lower relief. Archeopyle is of type P(4), the operculum is free. All the parasutures are underlined by ridges of irregular height7 higher than intratabular ornamentation (Plate Il, 2, 4-8) and composed of distally linked projections.
Paratabulation is Gonyaulacoid, of Gonyaulacysta-type (Fig.6). The apical area has not been observed; A/l u, B/C. C/A parasutures all disappear in the apical trabeculate network of the horn (Plate II, 9). There is a 6-sided central antapical paraplate Y (sexiform), probably in symmetrical arrangement (cf. text-fig. 2, Helenes, 1986). The ventral area seems to show a sigmoidal sulcus: S-type organization (Evitt, 1985). The arrangement of paraplates on ventral epicyst is hardly discernible (Plate II, 7), but li is evidently narrow, roughly triangular-shaped and clearly not in contact with lu. Consequently, A contacts ai: A/ai arrangement (Helenes, 1986). A is larger than lu, and there is no obliteration of their parasuture. Ii, Im, Iu are not distinct. Complete paratabulation of precingular, paracingular and postcingular areas have been observed (Fig.6).
Affinities:
Soncini, 1992, p. 332-333: At first sight, the moroccan dinocysts described could be assigned to the genus Apteodinium (Eisenack) Lucas-Clark 1987, due to the general outline, the prominent apical horn, the complexity of the wall with a microreticulate to spongy aspect according to the focus level, and the paratabulation hardly discernible. The best comparison could be made with A. granulatum (Eisenack) Lucas-Clark 1987. However, the distal network of trabeculae linking tips of adjacent pila or clava is here much less dense than on any Apteodinium species. No true outer layer can be delineated at high magnification, even discontinuous (Plate II, 9). The autophragm is variously ornamented but not 2 or 3-layered as described by Lucas-Clark (1987) for A. granulatum. Consequently, it seems unappropriate to consider the apical horn as a "cavation", as Sarjeant (1985) does about A. granulatum. The apical horn is here a projection of trabeculae, more or less loosely linked together (Fig.5). Although it is hardly discernible, paratabulation pattern has been partially reconstructed (Fig.6). It shows a typical affinity with Gonyaulax-type cysts, permanently excluding the attribution to any Apteodinium or Aldorfia species (cf. Cribroperidinium and Aptiana- Ventriosum Complex, Helenes, 1986; Lucas-Clark, 1987). Among Evitt"s Leprodinium Complex (1985), Acanthaulax is the most appropriate genus to compare moroccan specimens with, although these do not show any spine on parasuttural ridges or in intratabular ornamentation (Sarjeant, in Davey el al., 1966). The characteristic "dense spine cover" (Sarjeant, in Davey et al., 1966) is here a dense (simple or bifurcate) pila or clava cover. Moreover, the genus Liesbergia Berger 1986 has been erected to differentiate Acanthaulax-type cysts with a highly distinctive apical horn "only formed by development of the external ornamentation and not the entire periphragm" (Berger, 1986). Except the nature of ornamentation on the cyst surface (and their stratigraphic distribution).
L. scarburghensis (Sarjeant) Berger 1986 and moroccan cysts are quite similar, both showing "an irregular reticulate patterning" (Sarjeant, 1961) in over view of the wall surface, made of spiny projections more or less linked together on the former (low ridges described by Sarjeant, 1961), made of rounded projections (clava or pila) with, sometimes, connected tips on the latter. L. Iiesberghensis Berger 1986 differs from L. ahdounensis in having a scattered ornamentation and fewer trabeculae building the apical horn.
About the characteristics of the genus Liesbergia, Berger"s diagnosis lacks information about paraplates arrangements. A reexamination of Liesbergia type material should be of great interest to compare Paleogene and Jurassic specimens.
Remark: The stratigraphic gap between L. Iiesbergensis and L. scarburghensis (Oxfordian) and L. abdounensis (Thanetian-Ypresian) may be filled, perhaps, with a systematic review of all socalled Apteodinium cysts at high magnification: presumed non-tabulate taxa often prove to be "cryptotabulate" in fact. Then, one could discover some "Apteodinium" specimens with a paratabulation pattern not belonging to Aptiana-Ventriosum Complex but to Gonyaulacysta-type, during the Cretaceous interval. Perhaps new species of Liesbergia could then be erected.