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Erymnodinium
From Fensome et al., 2019:
Erymnodinium, Lentin et al., 1994, p.579,581.
Type: de Verteuil and Norris, 1992, pl.9, figs.3–4, as Sumatradinium? delectabile.
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Original description: [Lentin et al., 1994]:
Diagnosis:
Acavate, dorsoventrally compressed peridinialean cysts with the single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 µm in diameter and muri about 1 µm in height.
Paratabulation, especially marginally, delineated by parasutural crests, which are sometimes reduced or absent between individual paraplates. The archeopyle is formed from the loss of the middorsal intercalary paraplate, which is large hexa, isodeltaform and posteriorly extends almost to the equator of the cyst.
Description:
Shape: Cyst dorsoventrally compressed, ambitus rounded pentagonal to peridinioid. Apex rounded, sometimes with a short apical boss formed from the sutural crests. Antapex weakly to strongly bilobate. Epicyst generally larger than hypocyst.
Wall relationships: Acavate with autophragm only or with closely appressed periphragm and endophragm.
Wall features: Periphragm or autophragm bearing a complete or incomplete reticulumt with lumina generally 0.5-1.5 µm in diameter and muri up to 1 µm high. Endophragm, where observed, less than 0.5 µm thick and psilate.
Mode of excystment: Archeopyle results from the loss of a large hexa isodeltaform middorsal intercalary paraplate, presumably 2a, posteriorly extending almost to the equator. This paraplate commonly appears slightly offset. The operculum is usually free.
Paratabulation: Generally indicated by parasutural crests, which are about 4-8 µm high, psilate, and sinuous in plan view. The crests do not delineate all paraplate boundaries and are usually not associated with the presumed 2a. Thus, especially on the dorsal surface, the crests appear to be predominantly ambital. The crests represent folds of the periphragm or autophragm, with the two sides being closely appressed. Some crests may occasionally have thickened bands and may be perforate proximally. The paracingulum is usually marked by well-developed anterior and posterior crests, which may not extend across the dorsal surface. The sulcus may be up to 20 µm wide and is indistinct.
Affinities:
Only one other peridinialean genus, Sumatradinium, has the same distinctive, incomplete to complete surface reticulum as that found in Erymnodinium. The two genera also have the same mode of excystment, although in some specimens of Sumatradinium more than one paraplate may be involved. However, Sumatradinium has processes, whereas Erymnodinium has sutural septa. The type species of Erymnodinium, E. delectabile, was questionably included in Sumatradinium by de Verteuil and Norris (1992). These authors (p. 92) noted, ``The new species is provisionally included with Sumatradinium until further data are available regarding the extent and significance of this feature [the presence of sutural crests]." Specimens recovered from samples in Evangeline H-98 have confirmed the distinctive morphology of this species and justify the erection of the genus Erymnodinium.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Erymnodinium Lentin et al., 1994, is acavate, with a single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 µm and muri about 1 µm high. Paratabulation, especially marginal, delineated by parasutural crests, which are reduced or absent between some plates. Archeopyle large hexa, isodeltaform.
Erymnodinium, Lentin et al., 1994, p.579,581.
Type: de Verteuil and Norris, 1992, pl.9, figs.3–4, as Sumatradinium? delectabile.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Lentin et al., 1994]:
Diagnosis:
Acavate, dorsoventrally compressed peridinialean cysts with the single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 µm in diameter and muri about 1 µm in height.
Paratabulation, especially marginally, delineated by parasutural crests, which are sometimes reduced or absent between individual paraplates. The archeopyle is formed from the loss of the middorsal intercalary paraplate, which is large hexa, isodeltaform and posteriorly extends almost to the equator of the cyst.
Description:
Shape: Cyst dorsoventrally compressed, ambitus rounded pentagonal to peridinioid. Apex rounded, sometimes with a short apical boss formed from the sutural crests. Antapex weakly to strongly bilobate. Epicyst generally larger than hypocyst.
Wall relationships: Acavate with autophragm only or with closely appressed periphragm and endophragm.
Wall features: Periphragm or autophragm bearing a complete or incomplete reticulumt with lumina generally 0.5-1.5 µm in diameter and muri up to 1 µm high. Endophragm, where observed, less than 0.5 µm thick and psilate.
Mode of excystment: Archeopyle results from the loss of a large hexa isodeltaform middorsal intercalary paraplate, presumably 2a, posteriorly extending almost to the equator. This paraplate commonly appears slightly offset. The operculum is usually free.
Paratabulation: Generally indicated by parasutural crests, which are about 4-8 µm high, psilate, and sinuous in plan view. The crests do not delineate all paraplate boundaries and are usually not associated with the presumed 2a. Thus, especially on the dorsal surface, the crests appear to be predominantly ambital. The crests represent folds of the periphragm or autophragm, with the two sides being closely appressed. Some crests may occasionally have thickened bands and may be perforate proximally. The paracingulum is usually marked by well-developed anterior and posterior crests, which may not extend across the dorsal surface. The sulcus may be up to 20 µm wide and is indistinct.
Affinities:
Only one other peridinialean genus, Sumatradinium, has the same distinctive, incomplete to complete surface reticulum as that found in Erymnodinium. The two genera also have the same mode of excystment, although in some specimens of Sumatradinium more than one paraplate may be involved. However, Sumatradinium has processes, whereas Erymnodinium has sutural septa. The type species of Erymnodinium, E. delectabile, was questionably included in Sumatradinium by de Verteuil and Norris (1992). These authors (p. 92) noted, ``The new species is provisionally included with Sumatradinium until further data are available regarding the extent and significance of this feature [the presence of sutural crests]." Specimens recovered from samples in Evangeline H-98 have confirmed the distinctive morphology of this species and justify the erection of the genus Erymnodinium.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Erymnodinium Lentin et al., 1994, is acavate, with a single or outer wall layer bearing a complete or incomplete reticulum, with lumina typically less than 2 µm and muri about 1 µm high. Paratabulation, especially marginal, delineated by parasutural crests, which are reduced or absent between some plates. Archeopyle large hexa, isodeltaform.