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Molassedinium
Molassedinium, Soliman and Slimani, 2019, p. 663
Type species: Molassedinium bicornutum, Soliman and Slimani, 2019, (Plate 1, figures 1–4).
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Original description: [Soliman and Slimani, 2019]:
Diagnosis:
Molassedinium gen. nov. is a holocavate gonyaulocoid dinoflagellate cyst characterised by apical and antapical ectophragmal horns and by an apical archaeopyle. It is here assigned to the subfamily Leptodinioideae, since it is a gonyaulacacean in which there is an L-type ventral organisation, neutral torsion and four climactal plates (here four apical plates 1'–4') (Fensome et al. 1993, p. 86).
Description:
Intermediate, subspherical to ovoidal holocavate dinoflagellate cyst with a thick autophragm and a thin ectophragm. Ectophragm supported by short penitabular processes rising from the autophragm, but detached at the polar areas to form apical and antapical horns.
Autophragm with sutural ridges and granulate to verrucate intratabular areas and ectophragm may be perforate
Gonyaulacoid, characteristic of the subfamily Leptodinioideae, indicated by sutural ridges on the autophragm and also by aligned sutural perforations and/or cracks on the ectophragm, formula 4', 6'', 6c, 6''', 1p, 1'''', as, ps, xs. Cingulum slightly laevorotatory. L-type ventral organisation indicated mainly by the contact between the apical plate 1' and the precingular plate 6''. Neutral torsion indicated by the boundary between the precingular plates (3''/4''), which is in line with the boundary between the postcingular plates (4'''/5''') (Figure 3; Plate 2, figure 4). A sexiform hypocystal plate organisation is suggested since the antapical plate 1'''' seems to be hexagonal and touches the postcingular plate 6''' and the posterior sulcal plate (ps) does not touch the postcingular plate 1'''. Anterior sulcal plate (as) well developed and remaining sulcal plates poorly delimited.
Apical archaeopyle type (tA) with a zigzag margin, accessory sutures and a sulcal notch.
Operculum simple polyplacoid, mostly free, occasionally in place
Affinities:
Biconodinium is also gonyaulocoid and bicornucavate with an apical archaeopyle, according to Stover and Williams (1987, p. 39), but differs from the new genus by its fusiform shape and its wall consisting of an endophragm and a periphragm, which are usually appressed except at the base of the horns, where they are detached. In contrast, Molassedinium gen. nov. has a holocavate central body with an autophragm and an ectophragm, which is supported by short processes rising from the autophragm.
Regarding the shape, tabulation and general morphology, the central body of the new genus resembles that of Alisocysta, Eisenackia, Lithodinia and Stoveracysta, but these genera differ in having an autophragm only rather than an autophragm and ectophragm, and in lacking horns.
Gardodinium resembles the new genus in being holocavate, but differs in having processes supporting the ectophragm covering the whole autophragm rather than restricted to the penitabular areas, by the absence of an antapical horn, and by its tabulation faintly visible only on the ectophragm rather than expressed by sutural crests on the autophragm.
Membranigonyaulax is also a holocavate gonyaulacoid cyst with sutural crests and intratabular ornamentation, which together support distally an ectophragm (Slimani 1994; Slimani and Louwye, 2012, p. 110–111, plate 1). This genus also has an apical archaeopyle (tA), but differs from the new genus mainly by the absence of apical and antapical horns. The ectophragm may be highly perforated or interrupted in the sutural areas, showing similar tabulation to that in the autophragm, and the hypocystal arrangement is sexiform rather than quinqueform in Membranigonyaulax. Furthermore, Molassedinium has a neutral (Leptodinioideae) rather than sinistral (Gonyaulacoideae) torsion as in Membranigonyaulax.
Type species: Molassedinium bicornutum, Soliman and Slimani, 2019, (Plate 1, figures 1–4).
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Original description: [Soliman and Slimani, 2019]:
Diagnosis:
Molassedinium gen. nov. is a holocavate gonyaulocoid dinoflagellate cyst characterised by apical and antapical ectophragmal horns and by an apical archaeopyle. It is here assigned to the subfamily Leptodinioideae, since it is a gonyaulacacean in which there is an L-type ventral organisation, neutral torsion and four climactal plates (here four apical plates 1'–4') (Fensome et al. 1993, p. 86).
Description:
Intermediate, subspherical to ovoidal holocavate dinoflagellate cyst with a thick autophragm and a thin ectophragm. Ectophragm supported by short penitabular processes rising from the autophragm, but detached at the polar areas to form apical and antapical horns.
Autophragm with sutural ridges and granulate to verrucate intratabular areas and ectophragm may be perforate
Gonyaulacoid, characteristic of the subfamily Leptodinioideae, indicated by sutural ridges on the autophragm and also by aligned sutural perforations and/or cracks on the ectophragm, formula 4', 6'', 6c, 6''', 1p, 1'''', as, ps, xs. Cingulum slightly laevorotatory. L-type ventral organisation indicated mainly by the contact between the apical plate 1' and the precingular plate 6''. Neutral torsion indicated by the boundary between the precingular plates (3''/4''), which is in line with the boundary between the postcingular plates (4'''/5''') (Figure 3; Plate 2, figure 4). A sexiform hypocystal plate organisation is suggested since the antapical plate 1'''' seems to be hexagonal and touches the postcingular plate 6''' and the posterior sulcal plate (ps) does not touch the postcingular plate 1'''. Anterior sulcal plate (as) well developed and remaining sulcal plates poorly delimited.
Apical archaeopyle type (tA) with a zigzag margin, accessory sutures and a sulcal notch.
Operculum simple polyplacoid, mostly free, occasionally in place
Affinities:
Biconodinium is also gonyaulocoid and bicornucavate with an apical archaeopyle, according to Stover and Williams (1987, p. 39), but differs from the new genus by its fusiform shape and its wall consisting of an endophragm and a periphragm, which are usually appressed except at the base of the horns, where they are detached. In contrast, Molassedinium gen. nov. has a holocavate central body with an autophragm and an ectophragm, which is supported by short processes rising from the autophragm.
Regarding the shape, tabulation and general morphology, the central body of the new genus resembles that of Alisocysta, Eisenackia, Lithodinia and Stoveracysta, but these genera differ in having an autophragm only rather than an autophragm and ectophragm, and in lacking horns.
Gardodinium resembles the new genus in being holocavate, but differs in having processes supporting the ectophragm covering the whole autophragm rather than restricted to the penitabular areas, by the absence of an antapical horn, and by its tabulation faintly visible only on the ectophragm rather than expressed by sutural crests on the autophragm.
Membranigonyaulax is also a holocavate gonyaulacoid cyst with sutural crests and intratabular ornamentation, which together support distally an ectophragm (Slimani 1994; Slimani and Louwye, 2012, p. 110–111, plate 1). This genus also has an apical archaeopyle (tA), but differs from the new genus mainly by the absence of apical and antapical horns. The ectophragm may be highly perforated or interrupted in the sutural areas, showing similar tabulation to that in the autophragm, and the hypocystal arrangement is sexiform rather than quinqueform in Membranigonyaulax. Furthermore, Molassedinium has a neutral (Leptodinioideae) rather than sinistral (Gonyaulacoideae) torsion as in Membranigonyaulax.