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Evansia
From Williams et al., 2017:
[Evansia, Pocock, 1972, p. 95; Emendations: Jansonius, 1986, p. 208; Below, 1990, p. 72.
Type species: Evansia granulata, Pocock, 1972 (pl.24, fig.7)]
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Original description: [Pocock, 1972]:
Diagnosis:
Vesicle dorso-ventrally flattened, outline oval to ovoid. Apex with apical horn.
Archeopyle intercalary with free simple operculum.
No tabulation or prominent ornamentation.
Equatorial girdle not visible, or faintly visible.
Affinities:
Very similar to Apteodinium Eisenack, but the latter possess a simple precingular archaeopyle. Tenua Eisenack possesses an apical archaeopyle, and six precingular plates.
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Emended description:
Jansonius, 1986:
Diagnosis:
Body spheroidal to subspheroidal, with apical protrusion or horn, antapical protrusion lacking or rudimentary. Wall two-layered, layers closely appressed; inner layer thin, smooth, hyaline; outer layer thicker, with granulose texture, may form solid appendix on apical horn. Surface sculpture granulate, finely spinate, reticulate, or shagreenate.
Archaeopyle intercalary, composed of three hexagonal paraplates, which are lost individually.
Cingulum and sulcus not differentiated or rudimentary.
Affinities:
Pareodinia differs by a more elongate shape, and its archaeopyle is not know, or not developed. After accepting Evansia as emended here, Glomodinium has to be considered as a junior synonym.
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Below, 1990: (Translation: LPP):
Diagnosis:
Vesicle-/plate-arrangement of the dinoflagellate amphiesma cop, pop, cap, 3`, 3a-4a, 6`` (-7``), 7c, 6```, 2````, as, FM, ls, rs, ps, 1` insert. Growth of thecal plates gonyaulacoidal.
Cyst proximate, proximochorate, acavate to cavate, spheroidal, ovaloidal, poluhedrical, fusiform, also with apical protruberance. Wall consisting of pedium and luxuria, surface smooth, ornamented, with or without kalyptra. Nonareate, partially or entirely reflecting thecal tabulation. Areation scheme NR Pr/XPR/cop, pop, cap, NR`/3`, NRa/3a-4a, NR``/6`` (-7``), NRc/Xc/7c, NR```/6```, NR````/2````, NRs/Xs, FM, ls, rs, ps.
Archaeopyle anteriorly intercalary, 1a+2a+3a or 2a+3a(+4a) or 2a(+3a). Operculum solvate, opercular plates secate, general opercular formula 1a(s)+2a(s)+3a(s) or 2a(s)+3a(s)(+4a(s)) or 2a(S)(+3a(s)).
Affinities:
(annotated) For cysts with a Pareodinia-like habit, but with a tritabular anterior intercalary archaeopyle, Dodekova (1975) erected the genus Glomodinium, which differs from Pareodinia, which has only 2 anterior intercalaries. This conception is followed by Dörhöfer and Davies, 1980, Davies, 1983 and Below, 1990. Wiggins, 1975 and Stover and Evitt, 1978 consider Glomodinium to be a synonym of Pareodinia, because in their opinion Pareodinia includes species with 1I, 2I or 3I archaeopyles. Jansonius, 1986, proved that the type species of Evansia, E. granulata, possesses, just like Glomodinium, a 3I, instead of a monotabular archaeopyle, as described by Pocock, 1972. Thus, Glomodinium is a synonym of Evansia.
For a cavate species with 3I archaeopyle (the original diagnosis of a variable 3I to 5I archaeopyle I consider incorrect), Wolfard and Van Erve erected the genus Crussolia. I emended the diagnosis of Evansia to include all cavate forms, either cornucavate, circumcavate or holocavate, so that Crussolia becomes a synonym of Evansia.
If seen under the lightmicroscope, the array of forms around Evansia granulata is a homogenous group. As opposed to the smaller, bitabular archaeopyle of Pareodinia, the larger anterior intercalary archaeopyle is clearly tritabular, in E. eschachensis sometimes also quadratabular. Lightmicroscopically, an areation, sufficient for the reconstruction of the entire scheme, is not yet determined in any of the Evansia species. However, with SEM, two different arrangements of the three apicals can be observed for a similar habit and tritabular intercalary archaeopyle.
The first type, presumed to apply to Evansia, has a steno VI 1`, and touches the apex. Anteriorly it borders 2` and 3`, and thus is insert.
The apical areation scheme of the second type is identical to the arrangement of 1`, 2` and 3` in the genera Gresslyodinium and Paragonyaulacysta. 1` is very small and does not touch 2` or PR, because 2` and 3` join ventrally. 1` thus is exsert.
This results in the topical taxonomical problem, that without SEM analysis of type-material, the determination of the apical areation of all species with a definite, striking 3I archaeopyle, and this includes the type species, is not possible. I assume, that in Evansia granulata 1` borders PR. Those species with definite or supposed Paragonyaulacysta-like apical areation (1` exsert), I place in the new genus Paraevansia.
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Stover and Evitt, 1978, p. 230:
Remarks:
No evidence of an archaeopyle is apparent on the genoholotype, and the specimen consists of a single wall layer, not two layers (L.E. Stover), as implied by Pocock`s drawing (1972, fig.12). Although no archaeopyle is evident on the type specimens, Pocock (pers. comm.) stated that other, unillustrated specimens do show an intercalary archaeopyle. Depending upon the kind of archaeopyle, Evansia could be a synonym of Pareodinia.
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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.
Evansia Pocock, 1972, emend. Jansonius, 1986, emend. Below, 1990, was emended by Below (1990, p.72 ) as follows, Arrangement of vesicles on the dinoflagellate amphiesma cop, pop, cap, 3`, 3-4a, 6"(7"), 7c, 6"', 2"'', as, FM, ls, rs, ps, insert. Cyst proximate, proximochorate, acavate to cavate, spheroidal, ovaloidal, ovoidal, polyhedral, fusiform, and with an apical protuberance. Wall smooth, ornamented, with or without kalyptra, nontabulate or partially or completely reflecting tabulation. Archeopyle anterior intercalary, 1a + 2a + 3a or 2a + 3a(= 4a) or 2a(+3a), operculum solvate, opercular pieces secate. Below (1990) included in synonymy the genera Crussolia Wolfard and van Erve, 1981, and Glomodinium Dodekova, 1975.
[Evansia, Pocock, 1972, p. 95; Emendations: Jansonius, 1986, p. 208; Below, 1990, p. 72.
Type species: Evansia granulata, Pocock, 1972 (pl.24, fig.7)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Pocock, 1972]:
Diagnosis:
Vesicle dorso-ventrally flattened, outline oval to ovoid. Apex with apical horn.
Archeopyle intercalary with free simple operculum.
No tabulation or prominent ornamentation.
Equatorial girdle not visible, or faintly visible.
Affinities:
Very similar to Apteodinium Eisenack, but the latter possess a simple precingular archaeopyle. Tenua Eisenack possesses an apical archaeopyle, and six precingular plates.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Jansonius, 1986:
Diagnosis:
Body spheroidal to subspheroidal, with apical protrusion or horn, antapical protrusion lacking or rudimentary. Wall two-layered, layers closely appressed; inner layer thin, smooth, hyaline; outer layer thicker, with granulose texture, may form solid appendix on apical horn. Surface sculpture granulate, finely spinate, reticulate, or shagreenate.
Archaeopyle intercalary, composed of three hexagonal paraplates, which are lost individually.
Cingulum and sulcus not differentiated or rudimentary.
Affinities:
Pareodinia differs by a more elongate shape, and its archaeopyle is not know, or not developed. After accepting Evansia as emended here, Glomodinium has to be considered as a junior synonym.
---------------------------
Below, 1990: (Translation: LPP):
Diagnosis:
Vesicle-/plate-arrangement of the dinoflagellate amphiesma cop, pop, cap, 3`, 3a-4a, 6`` (-7``), 7c, 6```, 2````, as, FM, ls, rs, ps, 1` insert. Growth of thecal plates gonyaulacoidal.
Cyst proximate, proximochorate, acavate to cavate, spheroidal, ovaloidal, poluhedrical, fusiform, also with apical protruberance. Wall consisting of pedium and luxuria, surface smooth, ornamented, with or without kalyptra. Nonareate, partially or entirely reflecting thecal tabulation. Areation scheme NR Pr/XPR/cop, pop, cap, NR`/3`, NRa/3a-4a, NR``/6`` (-7``), NRc/Xc/7c, NR```/6```, NR````/2````, NRs/Xs, FM, ls, rs, ps.
Archaeopyle anteriorly intercalary, 1a+2a+3a or 2a+3a(+4a) or 2a(+3a). Operculum solvate, opercular plates secate, general opercular formula 1a(s)+2a(s)+3a(s) or 2a(s)+3a(s)(+4a(s)) or 2a(S)(+3a(s)).
Affinities:
(annotated) For cysts with a Pareodinia-like habit, but with a tritabular anterior intercalary archaeopyle, Dodekova (1975) erected the genus Glomodinium, which differs from Pareodinia, which has only 2 anterior intercalaries. This conception is followed by Dörhöfer and Davies, 1980, Davies, 1983 and Below, 1990. Wiggins, 1975 and Stover and Evitt, 1978 consider Glomodinium to be a synonym of Pareodinia, because in their opinion Pareodinia includes species with 1I, 2I or 3I archaeopyles. Jansonius, 1986, proved that the type species of Evansia, E. granulata, possesses, just like Glomodinium, a 3I, instead of a monotabular archaeopyle, as described by Pocock, 1972. Thus, Glomodinium is a synonym of Evansia.
For a cavate species with 3I archaeopyle (the original diagnosis of a variable 3I to 5I archaeopyle I consider incorrect), Wolfard and Van Erve erected the genus Crussolia. I emended the diagnosis of Evansia to include all cavate forms, either cornucavate, circumcavate or holocavate, so that Crussolia becomes a synonym of Evansia.
If seen under the lightmicroscope, the array of forms around Evansia granulata is a homogenous group. As opposed to the smaller, bitabular archaeopyle of Pareodinia, the larger anterior intercalary archaeopyle is clearly tritabular, in E. eschachensis sometimes also quadratabular. Lightmicroscopically, an areation, sufficient for the reconstruction of the entire scheme, is not yet determined in any of the Evansia species. However, with SEM, two different arrangements of the three apicals can be observed for a similar habit and tritabular intercalary archaeopyle.
The first type, presumed to apply to Evansia, has a steno VI 1`, and touches the apex. Anteriorly it borders 2` and 3`, and thus is insert.
The apical areation scheme of the second type is identical to the arrangement of 1`, 2` and 3` in the genera Gresslyodinium and Paragonyaulacysta. 1` is very small and does not touch 2` or PR, because 2` and 3` join ventrally. 1` thus is exsert.
This results in the topical taxonomical problem, that without SEM analysis of type-material, the determination of the apical areation of all species with a definite, striking 3I archaeopyle, and this includes the type species, is not possible. I assume, that in Evansia granulata 1` borders PR. Those species with definite or supposed Paragonyaulacysta-like apical areation (1` exsert), I place in the new genus Paraevansia.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Stover and Evitt, 1978, p. 230:
Remarks:
No evidence of an archaeopyle is apparent on the genoholotype, and the specimen consists of a single wall layer, not two layers (L.E. Stover), as implied by Pocock`s drawing (1972, fig.12). Although no archaeopyle is evident on the type specimens, Pocock (pers. comm.) stated that other, unillustrated specimens do show an intercalary archaeopyle. Depending upon the kind of archaeopyle, Evansia could be a synonym of Pareodinia.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Evansia Pocock, 1972, emend. Jansonius, 1986, emend. Below, 1990, was emended by Below (1990, p.72 ) as follows, Arrangement of vesicles on the dinoflagellate amphiesma cop, pop, cap, 3`, 3-4a, 6"(7"), 7c, 6"', 2"'', as, FM, ls, rs, ps, insert. Cyst proximate, proximochorate, acavate to cavate, spheroidal, ovaloidal, ovoidal, polyhedral, fusiform, and with an apical protuberance. Wall smooth, ornamented, with or without kalyptra, nontabulate or partially or completely reflecting tabulation. Archeopyle anterior intercalary, 1a + 2a + 3a or 2a + 3a(= 4a) or 2a(+3a), operculum solvate, opercular pieces secate. Below (1990) included in synonymy the genera Crussolia Wolfard and van Erve, 1981, and Glomodinium Dodekova, 1975.