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Tringadinium
From Fensome et al., 2019:
Tringadinium Riding and Helby, 2001e, p.126,128.
Type: Riding and Helby, 2001e, fig.10Q–S, as Tringadinium bjaerkei.
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Original description: [Riding and Helby, 2001e]:
Diagnosis:
Small, proximate, acavate dinoflagellate cysts, rounded subpolygonal to subtriangular in outline, normally with an equatorial constriction. Autophragm generally exhibits intratabular inflations or protuberances, which may be covered by low relief paratabular, penitabular, intratabular or nontabular ornamentational features. Paratabulation indicated by intratabular inflations and/or parasutural, penitabular and intratabular ornamentation. Where developed, the paratabulation style is partiform gonyaulacalean; the paratabulation formula is: 4', ?a, 6", Xe, 6"', 2 '"', Xs. Archaeopyle apical, operculum simple and normally free. The paracingulum is distinct and located towards the anterior of the cyst. It is characterised by a lack of ornamentation and is not obviously subdivided into paraplates. A marked constriction is generally present in the paracingular area. Parasulcus situated midventrally and indicated by a lack of ornamentation and a concavity; not obviously subdivided.
Remarks:
Tringadinium is a small partiform genus with an apical archaeopyle. It has a distinct constriction at the paracingulum and a wide range of ornamentation. Typically, the paratabulation is expressed by penitabular/intratabular ornamentation or prominent intratabular rounded protuberances.
Affinities:
Tringadinium resembles Woodinia Riding & Helby (this volume) in shape, size and paratabulation pattern. However, Woodinia is characterised by extremely long postcingular paraplates, a paracingulum inserted close to the apical region and intratabular areas ('pads') of differentiated autophragm (Riding & Helby, this volume). The genus Tringadinium is also similar in shape and ornamentation to Parvocysta Bjaerke 1980, Reutlingia Drugg 1978 and Susadinium Dorhofer & Davies 1980, except that Tringadinium has an apical, rather than an anterior intercalary, archaeopyle. The genus Mikrocysta Bjaerke 1980 emend. Below 1987 superficially resembles Tringadinium, but lacks the ornamentation and intratabular inflations. The epicystal paratabulation of Mikrocysta is also different (Below, 1987b, fig. 4 ). The equatorially constricted Fosteria is superficially similar in shape to Tringadinium, but has parasutural denticles/ processes (see above). Representatives of Tringadinium also closely resemble Susadinium? australis Riding & Helby (this volume) in general morphology. However, the paratabulation patterns are different and Susadinium? australis has a combination, apical and anterior intercalary, archaeopyle with a compound operculum. Furthermore, Tringadinium lacks the consistent development of ridges or septa surmounting the intratabular protuberances, which are characteristic of Susadinium? australis. Tetrachacysta Backhouse 1988 is a quadrilobate cyst with an indented paracingular zone. Paratabulation is usually expressed only by the apical archaeopyle suture (Backhouse, 1988).
Tringadinium Riding and Helby, 2001e, p.126,128.
Type: Riding and Helby, 2001e, fig.10Q–S, as Tringadinium bjaerkei.
---------------------------------------------------------------------------------------------------
Original description: [Riding and Helby, 2001e]:
Diagnosis:
Small, proximate, acavate dinoflagellate cysts, rounded subpolygonal to subtriangular in outline, normally with an equatorial constriction. Autophragm generally exhibits intratabular inflations or protuberances, which may be covered by low relief paratabular, penitabular, intratabular or nontabular ornamentational features. Paratabulation indicated by intratabular inflations and/or parasutural, penitabular and intratabular ornamentation. Where developed, the paratabulation style is partiform gonyaulacalean; the paratabulation formula is: 4', ?a, 6", Xe, 6"', 2 '"', Xs. Archaeopyle apical, operculum simple and normally free. The paracingulum is distinct and located towards the anterior of the cyst. It is characterised by a lack of ornamentation and is not obviously subdivided into paraplates. A marked constriction is generally present in the paracingular area. Parasulcus situated midventrally and indicated by a lack of ornamentation and a concavity; not obviously subdivided.
Remarks:
Tringadinium is a small partiform genus with an apical archaeopyle. It has a distinct constriction at the paracingulum and a wide range of ornamentation. Typically, the paratabulation is expressed by penitabular/intratabular ornamentation or prominent intratabular rounded protuberances.
Affinities:
Tringadinium resembles Woodinia Riding & Helby (this volume) in shape, size and paratabulation pattern. However, Woodinia is characterised by extremely long postcingular paraplates, a paracingulum inserted close to the apical region and intratabular areas ('pads') of differentiated autophragm (Riding & Helby, this volume). The genus Tringadinium is also similar in shape and ornamentation to Parvocysta Bjaerke 1980, Reutlingia Drugg 1978 and Susadinium Dorhofer & Davies 1980, except that Tringadinium has an apical, rather than an anterior intercalary, archaeopyle. The genus Mikrocysta Bjaerke 1980 emend. Below 1987 superficially resembles Tringadinium, but lacks the ornamentation and intratabular inflations. The epicystal paratabulation of Mikrocysta is also different (Below, 1987b, fig. 4 ). The equatorially constricted Fosteria is superficially similar in shape to Tringadinium, but has parasutural denticles/ processes (see above). Representatives of Tringadinium also closely resemble Susadinium? australis Riding & Helby (this volume) in general morphology. However, the paratabulation patterns are different and Susadinium? australis has a combination, apical and anterior intercalary, archaeopyle with a compound operculum. Furthermore, Tringadinium lacks the consistent development of ridges or septa surmounting the intratabular protuberances, which are characteristic of Susadinium? australis. Tetrachacysta Backhouse 1988 is a quadrilobate cyst with an indented paracingular zone. Paratabulation is usually expressed only by the apical archaeopyle suture (Backhouse, 1988).