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Tenua
From Fensome et al., 2019:
Tenua Eisenack, 1958a, p.410.
Emendations: Sarjeant, 1968, p.230–231; Pocock, 1972, p.94; Sarjeant, 1985a, p.94; Fensome et al., 2019a, p.45.
Junior homonym: Tenua Davey, 1978.
Taxonomic senior synonym: Cyclonephelium, according to Sarjeant and Stover (1978, p.49) -- however, Sarjeant (1985a, p.93) and Lentin and Williams (1989, p.365) retained Tenua Eisenack.
Taxonomic junior synonyms: Cerbia, according to Sarjeant (1985a, p.93–94) and Sarjeant (1992b, p.678) -- however, Duxbury (2002, p.76,78) retained Cerbia; Doidyx, according to Fensome et al.(2019a, p.45).
Duxbury (2002, p.78) considered that Tenua Eisenack may be the taxonomic senior synonym of Circulodinium.
Type: Eisenack, 1958a, pl.23, fig.1, as Tenua hystrix.
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Original description: [Eisenack, 1958]: (Translation: Norris and Sarjeant, 1965):
Diagnosis:
Thin-walled, oval shells without tabulation or fields, which are comparatively thickly set with short, solid, rod-sharped spines.
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Emended description: [Sarjeant, 1968]:
Diagnosis:
Proximate cyst, sphaeroidal, ellipsoidal or ovoidal in shape.
Tabulation lacking: cingulum and sulcus may, however, be indicated by alignment or by absence of spines. Wall composed either of a single layer or of two layers closely appressed.
Ornamentation very variable - extremely coarse granules or tubercles: very squat wart-like spines (separate or with limited interconnection); or short rod-like spines, simple or branching, sometimes solid, always with closed tips.
Archaeopyle apical, polygonal, with slits extending posteriorly from the angles, producing a typically ragged appearance.
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Pocock, 1972:
Diagnosis:
Vesicle dorso-ventrally flattened. Archeopyle apical with offset sulcal notch and six precingular plates which are not always visible. Outline varies from more or less circular or oval without indications of horns, to rounded sub-triangular with one apical and one or two antapical horns indicated by rounded lobes or angles. Vesicle smooth or with processes, some of which may be in sutural or tabular arrangement. Tips of processes free or interconnected.
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Sarjeant, 1985:
Diagnosis:
Proximate to proximochorate cysts, penitabulate, lenticular and consisting of autophragm only. Ambitus circular, oval or rounded-pentagonal. Apex rounded or with a slight outbulge; antapex concave, rounded or with asymmetrical or symmetrical outbulges. Autophragm smooth or sculptured. Peniplates outlined by continuous or discontinuous lines of tubercles or short, solid processes; intratabular processes lacking. Paratabulation 4`, 0a, 6``, X-6c, 5-?6```, 1p, 1````, Xs.
Archaeopyle formed by loss of all apical paraplates (type "tA"), as a unit or as opercular pieces.
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Emended description Fensome et al., 2019a:
Emended diagnosis. Areoligeracean cysts that are proximate to proximochorate; central body dorsoventrally compressed, with a subcircular, broadly subovoidal to asymmetrically lenticular ambitus, usually with an apical horn; posteriorly rounded to asymmetrical, with one or two weak to moderately developed antapical horns. Ornamentation absent or consists of free-standing elements, some of which may be aligned to reflect aspects of tabulation; however, processes are more or less uniformly distributed or present but may be substantially reduced in density in dorsoventral areas. Archaeopyle apical, type A(1-4'), operculum free; parasulcal notch offset to the left.
Comments. As we have noted, intergradation is a major problem in the Cyclonephelium group of genera. This problem is exacerbated when the type of a key genus has an unclear or “intermediate” morphology. Such is the case for the holotype of Tenua hystrix, the type of Tenua Eisenack 1958. Tenua is one of the earliest generic names in the group, but its morphology, especially process distribution, has been much debated, despite the fact that several authors have published new photographs of the type. After reviewing these images (referenced in the introductory sections), we conclude that the dorsoventral areas of the type are not devoid of ornament (as is the case in Circulodinium), although it is not uniformly distributed or distributed to clearly reflect tabulation (as in Cerbia and Canningopsis). Hence we propose the use Tenua for forms in which the ornament extends over the dorsovental areas, whether densely and uniformly or in a somewhat reduced and patchy manner, as in the type of Tenua hystrix. We consider that this retains to some extent the early intent and usage of the genus and will cause fewer taxonomic problems than would alternative interpretations. We emend the generic diagnosis accordingly.
Sarjeant (1966, p. 205–206) provided the following original diagnosis for Doidyx.
Proximate dinoflagellate cysts with flattened biconical shell, pronouncedly asymmetrical. Epitract in form of high cone which may be drawn out into an apical horn, giving a mammillate appearance: hypotract in form of flattened cone, with or without antapical prominence. Shell bulging out to one side more than the other; lateral horns lacking. Greater part of shell covered with short spines, simple or bifurcate: arrangement is in general random, but sometimes in rows, suggesting traces of tabulation. Equatorial zone, corresponding to cingulum, lacking spines: not hollowed. No pattern of sutures visible, no clear indication of sulcus. Apical archaeopyle formed by schism of shell on angular line of breakage.
This diagnosis largely parallels our concept of Tenua, and hence we treat Doidyx as a junior synonym of the former genus; but the type of Doidyx, the holotype of Doidyx anaphrissa, better fits our concept of Tenua. Sarjeant & Stover (1978) and Bint (1986) considered Doidyx to be a taxonomic junior synonym of Aptea and Pseudoceratium respectively. However, Pseudoceratium has a distinct lateral horn and Aptea has linear ornament. Although the type of Doidyx has a lateral bulge, Sarjeant (1966) stated unequivocally that the species lacks a lateral horn, as is apparent from the type.
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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.
Tenua Eisenack, 1958a, emend. Sarjeant, 1968, emend. Pocock, 1972, emend.Sarjeant, 1985a. Emendation by Sarjeant (1985a, p.94), proximate to proximochorate cysts, penitabulate, lenticular and consisting of autophragm only. Ambitus circular, oval or rounded-pentagonal. Apex rounded or with a slight outbulge; antapex concave rounded or with two asymmetrical or symmetrical outbulges. Autophragm smooth or sculptured. Peniplates outlined by continuous or discontinuous lines of tubercles or short, solid processes. Intratabular processes lacking. Paratabulation 4`, 0a, 6", x-6c, 5-?6"' , 1p, 1"'' , xs. Archeopyle formed by loss of all apical paraplates (type tA), as a unit or as opercular pieces. Sarjeant (1985a) considered Cerbia to be a taxonomic junior synonym of Tenua.
Tenua Eisenack, 1958a, p.410.
Emendations: Sarjeant, 1968, p.230–231; Pocock, 1972, p.94; Sarjeant, 1985a, p.94; Fensome et al., 2019a, p.45.
Junior homonym: Tenua Davey, 1978.
Taxonomic senior synonym: Cyclonephelium, according to Sarjeant and Stover (1978, p.49) -- however, Sarjeant (1985a, p.93) and Lentin and Williams (1989, p.365) retained Tenua Eisenack.
Taxonomic junior synonyms: Cerbia, according to Sarjeant (1985a, p.93–94) and Sarjeant (1992b, p.678) -- however, Duxbury (2002, p.76,78) retained Cerbia; Doidyx, according to Fensome et al.(2019a, p.45).
Duxbury (2002, p.78) considered that Tenua Eisenack may be the taxonomic senior synonym of Circulodinium.
Type: Eisenack, 1958a, pl.23, fig.1, as Tenua hystrix.
---------------------------------------------------------------------------------------------------
Original description: [Eisenack, 1958]: (Translation: Norris and Sarjeant, 1965):
Diagnosis:
Thin-walled, oval shells without tabulation or fields, which are comparatively thickly set with short, solid, rod-sharped spines.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description: [Sarjeant, 1968]:
Diagnosis:
Proximate cyst, sphaeroidal, ellipsoidal or ovoidal in shape.
Tabulation lacking: cingulum and sulcus may, however, be indicated by alignment or by absence of spines. Wall composed either of a single layer or of two layers closely appressed.
Ornamentation very variable - extremely coarse granules or tubercles: very squat wart-like spines (separate or with limited interconnection); or short rod-like spines, simple or branching, sometimes solid, always with closed tips.
Archaeopyle apical, polygonal, with slits extending posteriorly from the angles, producing a typically ragged appearance.
--------------------------------------
Pocock, 1972:
Diagnosis:
Vesicle dorso-ventrally flattened. Archeopyle apical with offset sulcal notch and six precingular plates which are not always visible. Outline varies from more or less circular or oval without indications of horns, to rounded sub-triangular with one apical and one or two antapical horns indicated by rounded lobes or angles. Vesicle smooth or with processes, some of which may be in sutural or tabular arrangement. Tips of processes free or interconnected.
--------------------------------------
Sarjeant, 1985:
Diagnosis:
Proximate to proximochorate cysts, penitabulate, lenticular and consisting of autophragm only. Ambitus circular, oval or rounded-pentagonal. Apex rounded or with a slight outbulge; antapex concave, rounded or with asymmetrical or symmetrical outbulges. Autophragm smooth or sculptured. Peniplates outlined by continuous or discontinuous lines of tubercles or short, solid processes; intratabular processes lacking. Paratabulation 4`, 0a, 6``, X-6c, 5-?6```, 1p, 1````, Xs.
Archaeopyle formed by loss of all apical paraplates (type "tA"), as a unit or as opercular pieces.
------------------------------------------------------------------------------------
Emended description Fensome et al., 2019a:
Emended diagnosis. Areoligeracean cysts that are proximate to proximochorate; central body dorsoventrally compressed, with a subcircular, broadly subovoidal to asymmetrically lenticular ambitus, usually with an apical horn; posteriorly rounded to asymmetrical, with one or two weak to moderately developed antapical horns. Ornamentation absent or consists of free-standing elements, some of which may be aligned to reflect aspects of tabulation; however, processes are more or less uniformly distributed or present but may be substantially reduced in density in dorsoventral areas. Archaeopyle apical, type A(1-4'), operculum free; parasulcal notch offset to the left.
Comments. As we have noted, intergradation is a major problem in the Cyclonephelium group of genera. This problem is exacerbated when the type of a key genus has an unclear or “intermediate” morphology. Such is the case for the holotype of Tenua hystrix, the type of Tenua Eisenack 1958. Tenua is one of the earliest generic names in the group, but its morphology, especially process distribution, has been much debated, despite the fact that several authors have published new photographs of the type. After reviewing these images (referenced in the introductory sections), we conclude that the dorsoventral areas of the type are not devoid of ornament (as is the case in Circulodinium), although it is not uniformly distributed or distributed to clearly reflect tabulation (as in Cerbia and Canningopsis). Hence we propose the use Tenua for forms in which the ornament extends over the dorsovental areas, whether densely and uniformly or in a somewhat reduced and patchy manner, as in the type of Tenua hystrix. We consider that this retains to some extent the early intent and usage of the genus and will cause fewer taxonomic problems than would alternative interpretations. We emend the generic diagnosis accordingly.
Sarjeant (1966, p. 205–206) provided the following original diagnosis for Doidyx.
Proximate dinoflagellate cysts with flattened biconical shell, pronouncedly asymmetrical. Epitract in form of high cone which may be drawn out into an apical horn, giving a mammillate appearance: hypotract in form of flattened cone, with or without antapical prominence. Shell bulging out to one side more than the other; lateral horns lacking. Greater part of shell covered with short spines, simple or bifurcate: arrangement is in general random, but sometimes in rows, suggesting traces of tabulation. Equatorial zone, corresponding to cingulum, lacking spines: not hollowed. No pattern of sutures visible, no clear indication of sulcus. Apical archaeopyle formed by schism of shell on angular line of breakage.
This diagnosis largely parallels our concept of Tenua, and hence we treat Doidyx as a junior synonym of the former genus; but the type of Doidyx, the holotype of Doidyx anaphrissa, better fits our concept of Tenua. Sarjeant & Stover (1978) and Bint (1986) considered Doidyx to be a taxonomic junior synonym of Aptea and Pseudoceratium respectively. However, Pseudoceratium has a distinct lateral horn and Aptea has linear ornament. Although the type of Doidyx has a lateral bulge, Sarjeant (1966) stated unequivocally that the species lacks a lateral horn, as is apparent from the type.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Tenua Eisenack, 1958a, emend. Sarjeant, 1968, emend. Pocock, 1972, emend.Sarjeant, 1985a. Emendation by Sarjeant (1985a, p.94), proximate to proximochorate cysts, penitabulate, lenticular and consisting of autophragm only. Ambitus circular, oval or rounded-pentagonal. Apex rounded or with a slight outbulge; antapex concave rounded or with two asymmetrical or symmetrical outbulges. Autophragm smooth or sculptured. Peniplates outlined by continuous or discontinuous lines of tubercles or short, solid processes. Intratabular processes lacking. Paratabulation 4`, 0a, 6", x-6c, 5-?6"' , 1p, 1"'' , xs. Archeopyle formed by loss of all apical paraplates (type tA), as a unit or as opercular pieces. Sarjeant (1985a) considered Cerbia to be a taxonomic junior synonym of Tenua.