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Sentusidinium
From Fensome et al., 2019:
Sentusidinium, Sarjeant and Stover, 1978, p.49–50.
Emendations: Courtinat, 1989, p.192; Wood et al., 2016, p.79–80.
Taxonomic senior synonym: Batiacasphaera, according to Dörhöfer and Davies (1980, p.40) -- however, Lentin and Williams (1981, p.24,253) retained Sentusidinium. Taxonomic junior synonyms: Escharisphaeridia, Barbatacysta and Pilosidinium, all according to Wood et al. (2016, p.79); Pseudobohaidina, by implication since the type is now considered a taxonomic junior synonym of Sentusidinium ringnesiorum.
Nomenclatural junior synonym: Tenua Davey, which has the same type.
Type: Sarjeant, 1968, pl.1, fig.22; pl.2, fig.1, as Tenua rioultii.
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Original description: [Sarjeant and Stover, 1978]:
Diagnosis:
Proximate to proximochorate cyst, subspherical to ellipsoidal; wall single-layered or apparently so, and bearing short, usually evenly distributed nontabular projections such as coarse granulae, tuberculae, baculae, or spines with blunt, acuminate, capitate or branched tips. These surface features are generally isolate, but some adjacent projections may have confluent bases and/or interconnected tips. The length of the projections is consistently less than one-half, and typically less than one-third, of the shortest diameter of the cyst.
Paratabulation is indicated mainly by the type A apical archaeopyle, whose principal suture is generally zigzag (although the angulation may not be readily apparent on uncompressed specimens). Short, longitudinally directed accessory archaeopyle sutures are frequently present, their positions denoting the anterior boundaries between precingular paraplates. The operculum is free, its constituent paraplates not differentiated. An equatorial alignment of some projections, delimiting a lightly ornamented or unornamented paracingulum, may sometimes be observed; but this is usually inconspicuous and may not be developed. Other indications of paratabulation are lacking.
Overall size is generally less than 100 μm.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subspherical to ellipsoidal body, rather than one that is dorsoventrally flattened; in lacking an offset parasutural notch; and in not having medial areas without, or with reduced, ornamentation. In addition, Sentusidinium lacks an apical angularity and antapical lobations; however, it should be stressed that these are not developed in all species of Cyclonephelium. Sentusidinium differs from Parvulodinium Dodekova (1975) by having nontabular rather than intratabular ornamentation.
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Modified description:
Stover and Evitt 1978, p. 80-81:
Synopsis:
Cysts proximate to proximochorate; subspherical autophragm bears numerous short, generally evenly distributed, normally isolated, nontabular projection; archeopyle apical, Type tA.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm with numerous, generally evenly distributed and usually isolated nontabular features; these are most often short spines or cones, and may be granules, tubercules, bacules, or similar features of low to moderate relief.
Paratabulation: Generally indicated by archeopyle only, occasionally also by poorly delimited paracingulum.
Archeopyle: Apical, Type (tA); principal archeopyle suture zigzag; operculum free.
Paracingulum: Generally not indicated, or indicated by faint transverse alignment of nontabular features in the equatorial area.
Parasulcus: Not indicated.
Size: Small to intermediate.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subsphaerical body rather than a lenticular body, and in lacking the medial bald areas found on many species of Cyclonephelium.
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Emended description:
Courtinat, 1989: (Translation: LPP):
Diagnosis:
Subspherical to ovoidal apteate cyst with an autophragm only. The cyst has parasutural and intratabular processes. These processes may be joined at the bases or distally interconnected. The gonyaulacacean type paratabulation formula is, following the Kofoid notation: 4`, ?a, 6``, 6c, 6```, 1p, 1pv, 1````, ?s; following the Taylor-Evitt notation: A-C, 1u, ?K, au-fi, Iu-VI, X-Z, ?(ai, fu, Ii, Im). The operculum is free multiplated. The archaeopyle is apical type (tA); the accessory archaeopyle sutures are more or less well developed depending on the species.
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Emended description wood et al., 2016:
Emended diagnosis: Proximate to proximochorate, acavate gonyaulacacean dinoflagellate cysts with a subspheroidal to ovoidal central body. The autophragm may be psilate or bear isolated, nontabular sculptural elements that are usually of low to moderate relief and evenly distributed. Archaeopyle apical, type (tA), normally with a detached operculum; deep accessory archaeopyle sutures between the six precingular plates are typically present.
Emended description: Small to intermediate, proximate to proximochorate, acavate gonyaulacacean dinoflagellate cysts. The dorso-ventral outline subspherical, oval or elongate oval. The autophragm is variable in thickness and devoid of ornament or covered by numerous, mostly isolated nontabular sculptural elements of low tomoderate relief. The ornamentation is highly variable between species: for example, the autophragm may be psilate, shagreenate, scabrate, granulate, papillate, pustulate, verrucate, gemmate, tuberculate, pilate, clavate, baculate, echinate or setose (Fig. 1). Smooth (psilate and shagreenate) forms are less common than ornamented forms. The elements are typically evenly distributed, nontabular and short. Rarely, the ornamentation may be concentrated locally. Occasionally individual elements may be proximally confluent; distal connections or trabeculae are extremely rare. Occasionally a kalyptra may be developed. The archaeopyle is apical, type (tA), with a free operculum, although in some cases theoperculum does not always fully detach; accessory archaeopyle sutures between the precingular plates are typically well developed, particularly those of Late Jurassic age. The shapes of the archaeopyle and operculum and the angular principal archaeopyle suture are strongly indicative of the standard sexiform gonyaulacacean tabulation. Very rarely, the ornamentation may partially reflect and indicate the cingulum, but other indications of the tabulation are rarely if ever developed.
Comments: Sarjeant and Stover (1978, p. 49–50) derived the generic name Sentusidiniumfromthe Latin sentus,meaning thorny. The genus was emended by Courtinat (1989, p. 192), who gave a more concise diagnosis than the original, and presented a tabulation formula. He considered that the ornament (which he considered to consist of processes) is both intratabular and sutural. In our view, sutural ornamentation in Sentusidiniumis extremely rare; only a few species exhibit alignment of the ornamentation to indicate the cingulum(e.g. Sentusidinium fibrillosum). The overwhelming majority of the low-to-moderaterelief elements on cysts assigned to Sentusidinium are nontabular. Indeed, if tabulation is developed to any degree, assignment to another genus, such as Meiourogonyaulax, would be appropriate.
We regard the genera Barbatacysta, Escharisphaeridia and Pilosidinium to be taxonomic junior synonyms of Sentusidinium. The genus Escharisphaeridia was described by Erkmen and Sarjeant (1980) for psilate forms previously included in Chytroeisphaeridia that clearly have an apical archaeopyle. We consider forms of the Sentusidinium complex that are smooth, and do not conform to the morphologies of Pentafidia or Kallosphaeridium, to be attributable to Sentusidinium. Barbatacysta was erected by Courtinat (1989, p. 185) for ‘bearded cysts’ with a granular or verrucate autophragm, which have conical, subconical, buccinate, tubular or evexate intratabular processes that are distally acuminate, capitate, bifurcate or foliate. Courtinat (1989, p. 190) also introduced Pilosidinium, distinguishing it on the presence of capitate or bifurcate conical granules or spines, which may be interconnected and/or sutural. However, our appraisal of the species in Pilosidinium revealed that the processes are consistently isolated and nontabular. Consequently, we consider that the generic concepts of both Barbatacysta and Pilosidinium fall within the circumscription of Sentusidinium. The synonymy of Barbatacysta, Escharisphaeridia and Pilosidinium with Sentusidiniumhas clearly necessitated the transfer of their constituent species into Sentusidinium. During the course of our taxonomic review, it became clear that many of the species in the newly expanded Sentusidiniumare superfluous. As a consequence, 59 species are considered to be taxonomic junior synonyms of other species of Sentusidinium, the 38 species in Sentusidinium that we consider to be separate are discussed below. Of those 38, we consider that 34 belong unquestionably to Sentusidinium and four are problematical.
The 34 species that we include in Sentusidinium without question collectively have a stratigraphical range from the Jurassic to the Palaeogene (Fig. 3a–e); no exclusively Miocene species have been described. Most of the Jurassic species were described originally from Europe. However, all but one of the Cretaceous formswere described from Africa, Australia and North America; while most of the Palaeogene taxa
were described from China and India.
Comparison: Kallosphaeridium has an attached five-plate operculum, in contrast to the usually free, more conventionally gonyaulacacean four-plate operculum of Sentusidinium. Batiacasphaera has a reticulate to rugulate ornament. Pentafidia apparently has five precingular plates rather than six.
Sentusidinium, Sarjeant and Stover, 1978, p.49–50.
Emendations: Courtinat, 1989, p.192; Wood et al., 2016, p.79–80.
Taxonomic senior synonym: Batiacasphaera, according to Dörhöfer and Davies (1980, p.40) -- however, Lentin and Williams (1981, p.24,253) retained Sentusidinium. Taxonomic junior synonyms: Escharisphaeridia, Barbatacysta and Pilosidinium, all according to Wood et al. (2016, p.79); Pseudobohaidina, by implication since the type is now considered a taxonomic junior synonym of Sentusidinium ringnesiorum.
Nomenclatural junior synonym: Tenua Davey, which has the same type.
Type: Sarjeant, 1968, pl.1, fig.22; pl.2, fig.1, as Tenua rioultii.
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Original description: [Sarjeant and Stover, 1978]:
Diagnosis:
Proximate to proximochorate cyst, subspherical to ellipsoidal; wall single-layered or apparently so, and bearing short, usually evenly distributed nontabular projections such as coarse granulae, tuberculae, baculae, or spines with blunt, acuminate, capitate or branched tips. These surface features are generally isolate, but some adjacent projections may have confluent bases and/or interconnected tips. The length of the projections is consistently less than one-half, and typically less than one-third, of the shortest diameter of the cyst.
Paratabulation is indicated mainly by the type A apical archaeopyle, whose principal suture is generally zigzag (although the angulation may not be readily apparent on uncompressed specimens). Short, longitudinally directed accessory archaeopyle sutures are frequently present, their positions denoting the anterior boundaries between precingular paraplates. The operculum is free, its constituent paraplates not differentiated. An equatorial alignment of some projections, delimiting a lightly ornamented or unornamented paracingulum, may sometimes be observed; but this is usually inconspicuous and may not be developed. Other indications of paratabulation are lacking.
Overall size is generally less than 100 μm.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subspherical to ellipsoidal body, rather than one that is dorsoventrally flattened; in lacking an offset parasutural notch; and in not having medial areas without, or with reduced, ornamentation. In addition, Sentusidinium lacks an apical angularity and antapical lobations; however, it should be stressed that these are not developed in all species of Cyclonephelium. Sentusidinium differs from Parvulodinium Dodekova (1975) by having nontabular rather than intratabular ornamentation.
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Modified description:
Stover and Evitt 1978, p. 80-81:
Synopsis:
Cysts proximate to proximochorate; subspherical autophragm bears numerous short, generally evenly distributed, normally isolated, nontabular projection; archeopyle apical, Type tA.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm with numerous, generally evenly distributed and usually isolated nontabular features; these are most often short spines or cones, and may be granules, tubercules, bacules, or similar features of low to moderate relief.
Paratabulation: Generally indicated by archeopyle only, occasionally also by poorly delimited paracingulum.
Archeopyle: Apical, Type (tA); principal archeopyle suture zigzag; operculum free.
Paracingulum: Generally not indicated, or indicated by faint transverse alignment of nontabular features in the equatorial area.
Parasulcus: Not indicated.
Size: Small to intermediate.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subsphaerical body rather than a lenticular body, and in lacking the medial bald areas found on many species of Cyclonephelium.
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Emended description:
Courtinat, 1989: (Translation: LPP):
Diagnosis:
Subspherical to ovoidal apteate cyst with an autophragm only. The cyst has parasutural and intratabular processes. These processes may be joined at the bases or distally interconnected. The gonyaulacacean type paratabulation formula is, following the Kofoid notation: 4`, ?a, 6``, 6c, 6```, 1p, 1pv, 1````, ?s; following the Taylor-Evitt notation: A-C, 1u, ?K, au-fi, Iu-VI, X-Z, ?(ai, fu, Ii, Im). The operculum is free multiplated. The archaeopyle is apical type (tA); the accessory archaeopyle sutures are more or less well developed depending on the species.
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Emended description wood et al., 2016:
Emended diagnosis: Proximate to proximochorate, acavate gonyaulacacean dinoflagellate cysts with a subspheroidal to ovoidal central body. The autophragm may be psilate or bear isolated, nontabular sculptural elements that are usually of low to moderate relief and evenly distributed. Archaeopyle apical, type (tA), normally with a detached operculum; deep accessory archaeopyle sutures between the six precingular plates are typically present.
Emended description: Small to intermediate, proximate to proximochorate, acavate gonyaulacacean dinoflagellate cysts. The dorso-ventral outline subspherical, oval or elongate oval. The autophragm is variable in thickness and devoid of ornament or covered by numerous, mostly isolated nontabular sculptural elements of low tomoderate relief. The ornamentation is highly variable between species: for example, the autophragm may be psilate, shagreenate, scabrate, granulate, papillate, pustulate, verrucate, gemmate, tuberculate, pilate, clavate, baculate, echinate or setose (Fig. 1). Smooth (psilate and shagreenate) forms are less common than ornamented forms. The elements are typically evenly distributed, nontabular and short. Rarely, the ornamentation may be concentrated locally. Occasionally individual elements may be proximally confluent; distal connections or trabeculae are extremely rare. Occasionally a kalyptra may be developed. The archaeopyle is apical, type (tA), with a free operculum, although in some cases theoperculum does not always fully detach; accessory archaeopyle sutures between the precingular plates are typically well developed, particularly those of Late Jurassic age. The shapes of the archaeopyle and operculum and the angular principal archaeopyle suture are strongly indicative of the standard sexiform gonyaulacacean tabulation. Very rarely, the ornamentation may partially reflect and indicate the cingulum, but other indications of the tabulation are rarely if ever developed.
Comments: Sarjeant and Stover (1978, p. 49–50) derived the generic name Sentusidiniumfromthe Latin sentus,meaning thorny. The genus was emended by Courtinat (1989, p. 192), who gave a more concise diagnosis than the original, and presented a tabulation formula. He considered that the ornament (which he considered to consist of processes) is both intratabular and sutural. In our view, sutural ornamentation in Sentusidiniumis extremely rare; only a few species exhibit alignment of the ornamentation to indicate the cingulum(e.g. Sentusidinium fibrillosum). The overwhelming majority of the low-to-moderaterelief elements on cysts assigned to Sentusidinium are nontabular. Indeed, if tabulation is developed to any degree, assignment to another genus, such as Meiourogonyaulax, would be appropriate.
We regard the genera Barbatacysta, Escharisphaeridia and Pilosidinium to be taxonomic junior synonyms of Sentusidinium. The genus Escharisphaeridia was described by Erkmen and Sarjeant (1980) for psilate forms previously included in Chytroeisphaeridia that clearly have an apical archaeopyle. We consider forms of the Sentusidinium complex that are smooth, and do not conform to the morphologies of Pentafidia or Kallosphaeridium, to be attributable to Sentusidinium. Barbatacysta was erected by Courtinat (1989, p. 185) for ‘bearded cysts’ with a granular or verrucate autophragm, which have conical, subconical, buccinate, tubular or evexate intratabular processes that are distally acuminate, capitate, bifurcate or foliate. Courtinat (1989, p. 190) also introduced Pilosidinium, distinguishing it on the presence of capitate or bifurcate conical granules or spines, which may be interconnected and/or sutural. However, our appraisal of the species in Pilosidinium revealed that the processes are consistently isolated and nontabular. Consequently, we consider that the generic concepts of both Barbatacysta and Pilosidinium fall within the circumscription of Sentusidinium. The synonymy of Barbatacysta, Escharisphaeridia and Pilosidinium with Sentusidiniumhas clearly necessitated the transfer of their constituent species into Sentusidinium. During the course of our taxonomic review, it became clear that many of the species in the newly expanded Sentusidiniumare superfluous. As a consequence, 59 species are considered to be taxonomic junior synonyms of other species of Sentusidinium, the 38 species in Sentusidinium that we consider to be separate are discussed below. Of those 38, we consider that 34 belong unquestionably to Sentusidinium and four are problematical.
The 34 species that we include in Sentusidinium without question collectively have a stratigraphical range from the Jurassic to the Palaeogene (Fig. 3a–e); no exclusively Miocene species have been described. Most of the Jurassic species were described originally from Europe. However, all but one of the Cretaceous formswere described from Africa, Australia and North America; while most of the Palaeogene taxa
were described from China and India.
Comparison: Kallosphaeridium has an attached five-plate operculum, in contrast to the usually free, more conventionally gonyaulacacean four-plate operculum of Sentusidinium. Batiacasphaera has a reticulate to rugulate ornament. Pentafidia apparently has five precingular plates rather than six.