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Amphorosphaeridium
From Fensome et al., 2019:
Amphorosphaeridium, Davey, 1969c, p.30.
Taxonomic senior synonym: Lanternosphaeridium, according to Norvick (1975, p.50) -- however, Stover and Evitt (1978, p.140–141) retained Amphorosphaeridium.
Type: Davey, 1969c, pl.3, figs.1–2, as Amphorosphaeridium fenestratum.
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Original description: [Davey, 1969]:
Description:
Subspherical to ovoidal chorate dinoflagellate cysts possessing a two-layered wall. The periphragm layer is fibrous and variably pitted. Intratabular processes well developed. They are fibrous and typically hollow. Apical and usually antapical processes distinctive. Archaeopyle precingular (type P).
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Modified description:
Stover and Evitt, 1978, p. 140:
Synopsis:
Cysts skolochorate, acavate; body subspherical with fibrous, hollow processes; processes nontabular, or combination of nontabular and infrequent intratabular; apical and usually antapical processes distinctive; paratabulation expressed clearly by archeopyle only; archeopyle precingular, Type P.
Description:
Shape: Body subspherical.
Wall Relationships: Endophragm and periphragm appressed between processes.
Wall Features: No parasutural features. Processes nontabular, or combination of nontabular and infrequent intratabular; tubular, fibrous, simple or branched, and generally open distally; apical and usually antapical processes distinctive. Periphragm fibrous and variably pitted.
Paratabulation: Generally indicated by archeopyle only; indicated additionally by occasional intratabular processes.
Archeopyle: Precingular, Type P (3" only); operculum free.
Paracingulum: Generally not indicated; position may be suggested by faint alignment of processes.
Parasulcus: Not indicated.
Size: Large.
Affinities:
Amphorosphaeridium differs from Fibrocysta in having a spherical instead of an ellipsoidal body and in lacking a short to long protrusion at one or both poles. It differs from Cordosphaeridium in having more numerous, mainly nontabular processes and distinctive polar processes. It differs from Exochosphaeridium in having hollow and more complex processes, which on Exochosphaeridium are apparently solid and less branched distally. Morphology of the type species does not support the synonymy with Lanternosphaeridium claimed by Norvick (in Norvick & Burger 1976).
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Emended diagnosis. Gonyaulacacean (leptodinioid) chorate cysts of intermediate size, with subspheroidal to ovoidal central body and numerous processes. Central body and process walls are more or less fibrous. The processes are relatively robust, generally tapering and hollow, occasionally solid (or partially solid), intratabular, one to five per plate area; neighbouring processes sometimes are joined proximally or are completely fused. Apical and antapical prominences are occasionally present, expressed by enlarged (widened or fused) processes. The tabulation formula is 40, 60’, 6c, 60’’, 1p, 5 s, 10’’’, more or less clearly expressed by distribution of the processes, indicating sexiform antapex, L-type ventral plate arrangement, and neutral torsion of the hypocyst. The archaeopyle is precingular, type 1 P (30’), operculum is free or attached.
Remarks. The diagnosis of the genus is here emended to emphasise the leptodinioid tabulation pattern recognised in the type species (see Figure 3; Plate 1, figures 1–12). Although Davey (1969) did not recognise the tabulation pattern in A. fenestratum, and it cannot be clearly inferred from illustrations of the holotype alone (Davey 1969, pl. 3, figs 1, 2), he noticed some process alignment in the type species (Davey 1969, p. 31). In overall morphology, Amphorosphaeridium most resembles Exochosphaeridium Davey et al. 1966, which, however, belongs to the subfamily Cribroperidinioideae (see Helenes 2000, p. 137, 138, 140; Fensome et al. 2009, p. 31). Peyrot (2011, p. 284) synonymised Amphorosphaeridium fenetratum of Davey 1969, pl. 3, figs 1, 2 (the holotype of the species and the type species of the genus) with Exochosphaeridium majus (Lejeune-Carpentire 1940) Peyrot 2011, indicating the synonymy of the two genera, although not expressis verbis. However, the two species differ significantly: the processes in E. majus are solid or hollow (more commonly solid), whereas A. fenestratum generally bears hollow processes (only the slimmest, mainly sulcal processes may be solid distally, but proximally they are hollow). Furthermore, in E. majus the antapical prominence is never developed, while A. fenestratum may bear prominences at both poles. Comparison. Similarly to Amphorosphaeridium, the genus Exochosphaeridium has fibrous (or fibro-pitted) central body wall and processes, but the two genera differ in the development of processes and their distribution. In Exochosphaeridium the processes are generally more slender; they are commonly acuminate or hair-like and generally solid. Hollow processes, when present, are usually hollow only proximally. Occasionally, Exochosphaeridium possesses an enlarged apical process, sometimes irregularly branched distalward (see Plate 1, figure 16). Furthermore, the processes in Exochosphaeridium are generally nontabular, rarely contabular, vaguely indicating the tabulation (recognised in only single species, E. alisitosense; see Helenes 2000). In contrast, processes in Amphorosphaeridium are more robust, distinctly hollow, and less fibrous, and their arrangement more clearly indicates tabulation. Moreover, Amphorosphaeridium may possess prominences at both poles. Fibrocysta Stover & Evitt 1978 has an ellipsoidal central body, generally horn-like protrusions at the cyst poles, and more slender processes. Cordosphaeridium Eisenack 1963b has fewer processes (1 meso- to obtabular process per plate; Fensome et al. 2009). Operculodinium Wall 1967 has generally solid processes, which usually are uniform in size and shape, and tend to be isolated. Turbiosphaera Archangelsky 1969a has fewer, intratabular (one per plate), wider, and taeniate processes.
Amphorosphaeridium, Davey, 1969c, p.30.
Taxonomic senior synonym: Lanternosphaeridium, according to Norvick (1975, p.50) -- however, Stover and Evitt (1978, p.140–141) retained Amphorosphaeridium.
Type: Davey, 1969c, pl.3, figs.1–2, as Amphorosphaeridium fenestratum.
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Original description: [Davey, 1969]:
Description:
Subspherical to ovoidal chorate dinoflagellate cysts possessing a two-layered wall. The periphragm layer is fibrous and variably pitted. Intratabular processes well developed. They are fibrous and typically hollow. Apical and usually antapical processes distinctive. Archaeopyle precingular (type P).
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Modified description:
Stover and Evitt, 1978, p. 140:
Synopsis:
Cysts skolochorate, acavate; body subspherical with fibrous, hollow processes; processes nontabular, or combination of nontabular and infrequent intratabular; apical and usually antapical processes distinctive; paratabulation expressed clearly by archeopyle only; archeopyle precingular, Type P.
Description:
Shape: Body subspherical.
Wall Relationships: Endophragm and periphragm appressed between processes.
Wall Features: No parasutural features. Processes nontabular, or combination of nontabular and infrequent intratabular; tubular, fibrous, simple or branched, and generally open distally; apical and usually antapical processes distinctive. Periphragm fibrous and variably pitted.
Paratabulation: Generally indicated by archeopyle only; indicated additionally by occasional intratabular processes.
Archeopyle: Precingular, Type P (3" only); operculum free.
Paracingulum: Generally not indicated; position may be suggested by faint alignment of processes.
Parasulcus: Not indicated.
Size: Large.
Affinities:
Amphorosphaeridium differs from Fibrocysta in having a spherical instead of an ellipsoidal body and in lacking a short to long protrusion at one or both poles. It differs from Cordosphaeridium in having more numerous, mainly nontabular processes and distinctive polar processes. It differs from Exochosphaeridium in having hollow and more complex processes, which on Exochosphaeridium are apparently solid and less branched distally. Morphology of the type species does not support the synonymy with Lanternosphaeridium claimed by Norvick (in Norvick & Burger 1976).
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Emended diagnosis. Gonyaulacacean (leptodinioid) chorate cysts of intermediate size, with subspheroidal to ovoidal central body and numerous processes. Central body and process walls are more or less fibrous. The processes are relatively robust, generally tapering and hollow, occasionally solid (or partially solid), intratabular, one to five per plate area; neighbouring processes sometimes are joined proximally or are completely fused. Apical and antapical prominences are occasionally present, expressed by enlarged (widened or fused) processes. The tabulation formula is 40, 60’, 6c, 60’’, 1p, 5 s, 10’’’, more or less clearly expressed by distribution of the processes, indicating sexiform antapex, L-type ventral plate arrangement, and neutral torsion of the hypocyst. The archaeopyle is precingular, type 1 P (30’), operculum is free or attached.
Remarks. The diagnosis of the genus is here emended to emphasise the leptodinioid tabulation pattern recognised in the type species (see Figure 3; Plate 1, figures 1–12). Although Davey (1969) did not recognise the tabulation pattern in A. fenestratum, and it cannot be clearly inferred from illustrations of the holotype alone (Davey 1969, pl. 3, figs 1, 2), he noticed some process alignment in the type species (Davey 1969, p. 31). In overall morphology, Amphorosphaeridium most resembles Exochosphaeridium Davey et al. 1966, which, however, belongs to the subfamily Cribroperidinioideae (see Helenes 2000, p. 137, 138, 140; Fensome et al. 2009, p. 31). Peyrot (2011, p. 284) synonymised Amphorosphaeridium fenetratum of Davey 1969, pl. 3, figs 1, 2 (the holotype of the species and the type species of the genus) with Exochosphaeridium majus (Lejeune-Carpentire 1940) Peyrot 2011, indicating the synonymy of the two genera, although not expressis verbis. However, the two species differ significantly: the processes in E. majus are solid or hollow (more commonly solid), whereas A. fenestratum generally bears hollow processes (only the slimmest, mainly sulcal processes may be solid distally, but proximally they are hollow). Furthermore, in E. majus the antapical prominence is never developed, while A. fenestratum may bear prominences at both poles. Comparison. Similarly to Amphorosphaeridium, the genus Exochosphaeridium has fibrous (or fibro-pitted) central body wall and processes, but the two genera differ in the development of processes and their distribution. In Exochosphaeridium the processes are generally more slender; they are commonly acuminate or hair-like and generally solid. Hollow processes, when present, are usually hollow only proximally. Occasionally, Exochosphaeridium possesses an enlarged apical process, sometimes irregularly branched distalward (see Plate 1, figure 16). Furthermore, the processes in Exochosphaeridium are generally nontabular, rarely contabular, vaguely indicating the tabulation (recognised in only single species, E. alisitosense; see Helenes 2000). In contrast, processes in Amphorosphaeridium are more robust, distinctly hollow, and less fibrous, and their arrangement more clearly indicates tabulation. Moreover, Amphorosphaeridium may possess prominences at both poles. Fibrocysta Stover & Evitt 1978 has an ellipsoidal central body, generally horn-like protrusions at the cyst poles, and more slender processes. Cordosphaeridium Eisenack 1963b has fewer processes (1 meso- to obtabular process per plate; Fensome et al. 2009). Operculodinium Wall 1967 has generally solid processes, which usually are uniform in size and shape, and tend to be isolated. Turbiosphaera Archangelsky 1969a has fewer, intratabular (one per plate), wider, and taeniate processes.