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Enneadocysta dictyostila
From Fensome et al., 2019:
Enneadocysta dictyostila (Menéndez, 1965, p.11–12, pl.2, fig.6; pl.3, figs.18–22) Stover and Williams, 1995, p.109. Emendations: Sarjeant, 1981, p.115, as Areosphaeridium dictyostilum; Fensome et al., 2007, p.396–397, as Enneadocysta dictyostila. Holotype: Menéndez, 1965, pl.2, fig.6; pl.3, figs.18–20. Originally Hystrichosphaeridium, subsequently Oligosphaeridium?, thirdly Areosphaeridium, fourthly Enneadocysta?, fifthly (and now) Enneadocysta. Stover and Williams (1995, p.109) questionably assigned this species to Enneadocysta; however Fensome et al. (2007, p396) included it without question. Taxonomic senior synonym: Hystrichosphaeridium (now Areosphaeridium) diktyoplokum, according to Eaton (1971, p.359) — however, Sarjeant (1981, p.115) retained Areosphaeridium (now Enneadocysta?) dictyostilum. Taxonomic junior synonyms: Enneadocysta partridgei, according to Fensome et al. (2007, p.396); Areosphaeridium (now Enneadocysta) arcuatum and Cordosphaeridium
(now Cooksonidium) capricornum, both according to Sarjeant (1981, p.115–116) — however, Lentin and Williams (1985, p.26) retained Areosphaeridium (now Enneadocysta) arcuatum and Cordosphaeridium (now Cooksonidium) capricornum. Age: Tertiary.
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Original description Menéndez, 1965:
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Emended description Sarjeant, 1981:
Emended Diagnosis. Cyst subspherical to subovoidal or subpolygonal, skolochorate. Processes intratabular, with solid fibrous stems of length varying in the range one-third to one-half the short diameter of the cyst. Each process is distally expanded and bifurcate (licrate) ; the attitude of the bifurcations varies from patulate to recurved. The two branches are of variable relative and absolute length; they vary in breadth from
slender, with a denticulate distal margin, to broad, with an irregular distal margin and sometimes a net-like structure. Fenestration may be developed in the process stems, producing stem branches which are sometimes distally free. Paratabulation: 4', 6", Oc, 6'", 1p, 1"" (not always fully reflected, since the processes representing paraplates 6", 6"' and 1p may be lacking). The cingular Zone is typically devoid of processes; the antapex, with its single process, is typically offset to the right of the mid-ventral line. Between the postcingular processes and the antapical process there may be one or occasionally two additional processes. Archaeopyle apical (type m), tetratabular: operculum free.
Discussion. In his classic paper on the evolution of the group of skolochorate dinoflageilate cysts thenceforth placed into the genus Areosphaeridium, EATON (1971) dismissed the species dictyostilum as a junior synonym of KLUMPP'S diktyoplokus and, at the same time, set up a new species, A. arcuatum, to embrace forms with licrate, rather than clypeate, processes. This procedure was incorrect: MENENDEZ'S
brief diagnosis for dictyostilum embraces forms with processes of both types and his illustrations of the holotype (1965, pl. 2 fig. 6, pl. 3 figs. 18-20) make it clear that this specimen corresponds in morphology not with diktyoplokus, but with arcuatum. In consequence, the name dictyostilum has priority over the name arcuatum; it is here reinstated and an emended diagnosis, rephrased from the excellent one given by
EATON for the invalid arcuatum, is provided. To further complicate matters, COOKSON and EISENACK, in a paper published later in the same year as that by MENENDEZ, proposed a new species which they named Cordosphaeridium capricornum. Thirteen years later, STOVER and EVITT (1978) correctly perceived that it comprised forms referable to Areosphaeridium and transferred the species to that genus. An examination of the original illustrations (1965a, pl. 15 figs. 1-9) shows specimens that would be referable, according to the later study of EATON (1971), to his species arcuatum and multicornutum. The holotype of capricornum clearly lacks cingular processes (COOKSON and EISENACK, 1965, pl. 15 fig. 7). This species must thus also be considered a senior synonym of Areosphaeridium arcuatum but it is in turn junior, by a matter of months, to dictyostilum. Though others of the forms illustrated by COOKSON and EISENACK (1965a, pl. 15 Figs. 3-6) appear referable to Areosphaeridium multicornutum EATON, the latter name retains its validity. The two names Areosphaeridium arcuatum EATON and Areosphaeridium capricornum (COOKSON and EISENACK) must, in contrast, be abandoned as subjective junior Synonyms of A. dictyostilum (MENENDEZ). The species dictyostilum, as here redefined, appears confined in stratigraphical range to the Upper Eocene and characteristic of cool waters. From the Southern Hemisphere, it has as yet been recorded only from southernmost Argentina (MENENDEZ, 1965) and Victoria, Australia (COOKSON
and EISENACK, 1965a). In the Northern Hemisphere, it is known from England (EATON, 1971, 1976), the English Channel and France (GRUAS-CAVAGNETTO, 1976a), the Netherlands (DE CONINCK, 1977), ltaly (GRUAS-CAVAGNETTO, 1974) and the Grand Banks and Scotia Shelf, North Atlantic Ocean (JENKINS al., 1974; BARSS, BUJAK and WILLIAMS, 1979).
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Emended description (Fensome et al., 2007):
Emended diagnosis: A species of Enneadocysta with 6 precingular and 3-5 cingular processes and ragged clypeate to licrate process terminations.
Emended description
Shape: Cyst chorate with a slightly dorsoventrally flattened, subspherical central body that may be symmetrical or slightly asymmetrical in outline.
Wall relationships: Autophragm up to 1.5Itm thick.
Wall features: Autophragm smooth to faintly granulate, occasionally pitted. The central body bears 22 to 23 processes, mostly mesotabular but at least three (two antapical and the posterior sulcal) apparently obtabular to penitabular, with 10 epicystal, 9 hypocystal, and 3-5 (usually 4) cingular. Processes predominantly simple, but may occasionally be branched or form a linear complex. Process stems are solid, occasionally faintly fibrous and may be perforate or fenestrate; they vary in width, cingulars being the narrowest. One of the dorsal apical processes (on the operculum) may have a wider stem or may be twinned. Occasionally, cingular processes are minute protuberances without distal expansions.
Processes vary distally from bifid to most commonly ragged clypeate (text-figure 8).
Archeopyle: Apical, type (tA), tetratabular, operculum simple, free.
Enneadocysta dictyostila (Menéndez, 1965, p.11–12, pl.2, fig.6; pl.3, figs.18–22) Stover and Williams, 1995, p.109. Emendations: Sarjeant, 1981, p.115, as Areosphaeridium dictyostilum; Fensome et al., 2007, p.396–397, as Enneadocysta dictyostila. Holotype: Menéndez, 1965, pl.2, fig.6; pl.3, figs.18–20. Originally Hystrichosphaeridium, subsequently Oligosphaeridium?, thirdly Areosphaeridium, fourthly Enneadocysta?, fifthly (and now) Enneadocysta. Stover and Williams (1995, p.109) questionably assigned this species to Enneadocysta; however Fensome et al. (2007, p396) included it without question. Taxonomic senior synonym: Hystrichosphaeridium (now Areosphaeridium) diktyoplokum, according to Eaton (1971, p.359) — however, Sarjeant (1981, p.115) retained Areosphaeridium (now Enneadocysta?) dictyostilum. Taxonomic junior synonyms: Enneadocysta partridgei, according to Fensome et al. (2007, p.396); Areosphaeridium (now Enneadocysta) arcuatum and Cordosphaeridium
(now Cooksonidium) capricornum, both according to Sarjeant (1981, p.115–116) — however, Lentin and Williams (1985, p.26) retained Areosphaeridium (now Enneadocysta) arcuatum and Cordosphaeridium (now Cooksonidium) capricornum. Age: Tertiary.
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Original description Menéndez, 1965:
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Emended description Sarjeant, 1981:
Emended Diagnosis. Cyst subspherical to subovoidal or subpolygonal, skolochorate. Processes intratabular, with solid fibrous stems of length varying in the range one-third to one-half the short diameter of the cyst. Each process is distally expanded and bifurcate (licrate) ; the attitude of the bifurcations varies from patulate to recurved. The two branches are of variable relative and absolute length; they vary in breadth from
slender, with a denticulate distal margin, to broad, with an irregular distal margin and sometimes a net-like structure. Fenestration may be developed in the process stems, producing stem branches which are sometimes distally free. Paratabulation: 4', 6", Oc, 6'", 1p, 1"" (not always fully reflected, since the processes representing paraplates 6", 6"' and 1p may be lacking). The cingular Zone is typically devoid of processes; the antapex, with its single process, is typically offset to the right of the mid-ventral line. Between the postcingular processes and the antapical process there may be one or occasionally two additional processes. Archaeopyle apical (type m), tetratabular: operculum free.
Discussion. In his classic paper on the evolution of the group of skolochorate dinoflageilate cysts thenceforth placed into the genus Areosphaeridium, EATON (1971) dismissed the species dictyostilum as a junior synonym of KLUMPP'S diktyoplokus and, at the same time, set up a new species, A. arcuatum, to embrace forms with licrate, rather than clypeate, processes. This procedure was incorrect: MENENDEZ'S
brief diagnosis for dictyostilum embraces forms with processes of both types and his illustrations of the holotype (1965, pl. 2 fig. 6, pl. 3 figs. 18-20) make it clear that this specimen corresponds in morphology not with diktyoplokus, but with arcuatum. In consequence, the name dictyostilum has priority over the name arcuatum; it is here reinstated and an emended diagnosis, rephrased from the excellent one given by
EATON for the invalid arcuatum, is provided. To further complicate matters, COOKSON and EISENACK, in a paper published later in the same year as that by MENENDEZ, proposed a new species which they named Cordosphaeridium capricornum. Thirteen years later, STOVER and EVITT (1978) correctly perceived that it comprised forms referable to Areosphaeridium and transferred the species to that genus. An examination of the original illustrations (1965a, pl. 15 figs. 1-9) shows specimens that would be referable, according to the later study of EATON (1971), to his species arcuatum and multicornutum. The holotype of capricornum clearly lacks cingular processes (COOKSON and EISENACK, 1965, pl. 15 fig. 7). This species must thus also be considered a senior synonym of Areosphaeridium arcuatum but it is in turn junior, by a matter of months, to dictyostilum. Though others of the forms illustrated by COOKSON and EISENACK (1965a, pl. 15 Figs. 3-6) appear referable to Areosphaeridium multicornutum EATON, the latter name retains its validity. The two names Areosphaeridium arcuatum EATON and Areosphaeridium capricornum (COOKSON and EISENACK) must, in contrast, be abandoned as subjective junior Synonyms of A. dictyostilum (MENENDEZ). The species dictyostilum, as here redefined, appears confined in stratigraphical range to the Upper Eocene and characteristic of cool waters. From the Southern Hemisphere, it has as yet been recorded only from southernmost Argentina (MENENDEZ, 1965) and Victoria, Australia (COOKSON
and EISENACK, 1965a). In the Northern Hemisphere, it is known from England (EATON, 1971, 1976), the English Channel and France (GRUAS-CAVAGNETTO, 1976a), the Netherlands (DE CONINCK, 1977), ltaly (GRUAS-CAVAGNETTO, 1974) and the Grand Banks and Scotia Shelf, North Atlantic Ocean (JENKINS al., 1974; BARSS, BUJAK and WILLIAMS, 1979).
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Emended description (Fensome et al., 2007):
Emended diagnosis: A species of Enneadocysta with 6 precingular and 3-5 cingular processes and ragged clypeate to licrate process terminations.
Emended description
Shape: Cyst chorate with a slightly dorsoventrally flattened, subspherical central body that may be symmetrical or slightly asymmetrical in outline.
Wall relationships: Autophragm up to 1.5Itm thick.
Wall features: Autophragm smooth to faintly granulate, occasionally pitted. The central body bears 22 to 23 processes, mostly mesotabular but at least three (two antapical and the posterior sulcal) apparently obtabular to penitabular, with 10 epicystal, 9 hypocystal, and 3-5 (usually 4) cingular. Processes predominantly simple, but may occasionally be branched or form a linear complex. Process stems are solid, occasionally faintly fibrous and may be perforate or fenestrate; they vary in width, cingulars being the narrowest. One of the dorsal apical processes (on the operculum) may have a wider stem or may be twinned. Occasionally, cingular processes are minute protuberances without distal expansions.
Processes vary distally from bifid to most commonly ragged clypeate (text-figure 8).
Archeopyle: Apical, type (tA), tetratabular, operculum simple, free.