Back
Canninginopsis
From Fensome et al., 2019:
Canninginopsis Cookson and Eisenack, 1962b, p.488.
Emendations: Marshall, 1990b, p.80–82; McLachlan et al. 2018, p.679–680.
Type: Cookson and Eisenack, 1962b, pl.1, fig.16, as Canninginopsis denticulata.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Cookson and Eisenack, 1962]:
Description:
Shell flat, roughly seven-sided in outline, with a slight apical prominence and an indented base. Girdle helicoid, approximately equatorial on the dorsal surface. Longitudinal furrow obliquely directed. Both surfaces of shell marked but into large fields that border both girdle and longitudinal furrow. Shell opening by the detachment of the proximal part of the epitheca.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 25:
Synopsis:
Cysts proximate, lenticular; paratabulation gonyaulacacean, indicated by alignment of low parasutural features on the autophragm; archeopyle apical, Type tA; parasulcal notch offset.
Modified description:
Shape: Lenticular; apical margin may be obtusely angular and antapical margin may have median concavity between subangular lobes.
Wall relationships: Autophragm only.
Wall features: Parasutural alignment of features of low relief conspicuous; autophragm otherwise unornamented.
Paratabulation: Indicated by archeopyle and parasutural features; gonyaulacacean, formula: 4`, 6", 6c, 5-6```, 1p, 1````, ?s. Paraplate 1```` encompasses the two antapical lobes.
Archeopyle: Apical, Type tA; transverse dimension greater than dorsal-ventral dimension; principal archeopyle suture zigzag with offset parasulcal notch; operculum free.
Paracingulum: Indicated by parallel, transverse, equatorial parasutural features.
Parasulcus: Delimited by parasutural features, which may also indicate several constituent paraplates.
Size: Intermediate to large.
Affinities:
Canninginopsis differs from Canningia in having parasutural features that indicate the paratabulation. Canningia lacks parasutural features and the paratabulation is indicated generally by the archeopyle only.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Marshall, 1990:
Emended synopsis:
Cysts proximate, lenticular; paratabulation sexiform gonyaulacoid, indicated by alignment of penitabular or parasutural projections on autophragm and outline of archeopyle suture; archeopyle apical, Type (tA), parasulcal notch offset.
Emended description:
Shape: Lenticular; ventrodorsal outline subcircular to subpentagonal, often modified by an apical and 1 or 2 antapical horns forming rounded bulges or subconical structures. Each lateral margin usually e convex, occasionally extended at its mid-length i to form a rounded bulge or horn of similar morphology to the others (Fig. 4).
Wall relationships: Autophragm only.
Wall features: Surface scabrate, granulate, or foveolate to foveoreticulate; also marked by granules, ridges or low septa aligned in penitabular or parasutural rows. Ventral surface can be unsculptured.
Paratabulation: Indicated by archeopyle and penitabular-parasutural projections; pattern sexiform gonyaulacoid. Paratabulation on ventral surface, especially in parasulcal area, often incomplete or absent. Paraplates within parasulcus offset to the right: paraplates fu and ai may or may not be in contact. Antipolar paraplate Y crescentic, mainly restricted to dorsal surface.
Archeopyle: Apical, Type (tA), principal archeopyle suture zigzag, parasulcal notch offset to the left. Accessory sutures frequently evident along lateral boundaries of polar and pre-equatorial paraplates. Operculum usually free.
Paracingulum: Indicated by an equatorial groove, and associated parasutural features.
Parasulcus: Often defined by a shallow longitudinal groove along midventral surface and associated parasutural features. Flagellar markings occasionally evident.
Size: Intermediate to large.
Remarks:
This description differs from that given by Stover and Evitt (1978; p. 25) in that there is greater variation in the ventrodorsal outline of the autocyst, sculpture on the autophragm, and distribution and morphology of the characters marking paratabulation.
Affinities:
Evitt (1985) divided the category of ventrodorsally compressed gonyaulacoids named Gv-cysts into three complexes, Areoligera, Membranophoridinium, and Canningia, which are distinguished by their wall structure and surface ornament.
Canninginopsis belongs to the Areoligera complex which is characterised by having either an autophragm or two appressed layers with the periphragm extended to form processes or septa. Paratabulation is rarely complete and is defined by parasutural, penitabular, or intratabular ornament. Taxa frequently have reduced sculpture on the ventral and dorsal surfaces relative to that around the periphery.
Of the genera assigned to the Areoligera complex by Evitt (1985), Cerbia Below 1981 and Areoligera Lejeune-Carpentier emend. Williams and Downie in Davey et al. 1966 display greatest similarity to Canninginopsis. Cerbia is ornamented with penitabular tubercles or short processes and this produces an apparent overlap in morphology with the variant of Canninginopsis with penitabular sculpture, which is C. intermedia. The species assigned to Cerbia can be distinguished from C. intermedia in that they have sculpture on the ventral surface. However, these species may prove to be cogeneric. The ventral surface of Areoligera may be featureless and the dorsal surface has rows of penitabular processes or septa arranged fields or arcs. The projections on Canninginopsis are considerably shorter and define a more complete paratabulation. Circulodinium Alberti 1961 differs from Canninginopsis in having a greater concentration of sculptural elements, grana, vermiculae, processes, on the autophragm, which mainly appear nontabulate.
Bint (1986) examined some Mid Cretaceous ceratioid cysts from the western interior of the USA, and he compared these forms with published records of ventrodorsally compressed cysts belonging to the Areoligera - Cyclonephelium complex of Wall and Evitt (1975). Some forms within this complex lacking indications of paratabulation other than the archeopyle outline are difficult to distinguish from Early Cretaceous ceratioids lacking the typical development of postcingular horns, such as some species of Pseudoceratium Gocht 1957. Bint suggested that these may be differentiated by the shape of the anterior margin of the pre-equatorial paraplate 2. He believed that this is planate on ceratioid cysts and camerate on ventrodorsally compressed gonyaulacoids. Bint considered that Canninginopsis has a gonyaulacoid paratabulation, however, noted that paraplate 2 was camerate/? planate margin (Bint, 1986, text-fig. 12). The species of Canninginopsis studied here confirm Bint`s proposal, in that the anterior margin of paraplate 2 seems to range from planate, to faintly to distinctly camerate. This places some uncertainty on this criterion for distinguishing gonyaulacoid and ceratioid cysts.
---------------------------------------------------------------------------
Emended diagnosis Fensome et al., 2019a:
Areoligeracean cysts that are proximate, with subpentagonal ambitus. Acavate. One apical horn. Antapex rounded to asymmetrical with two antapical horns. Outer wall occasionally forming spongeous thickenings or highest relief ornamentation along apical and antapical horn margins. Tabulation indicated by archaeopyle and alignment of sutural ornamentation which may be granulate, denticulate, verrucate, or spinous. Archaeopyle apical, with formula A(1–4’), operculum free; sulcal notch offset to the left.
Comparison. Canninginopsis differs from Circulodinium in having sutural alignment of granules and verrucae with less concentration of nontabulate sculptural elements on the autophragm. Canninginopsis can also be differentiated from Tenua in having low-relief sutural ornamentation rather than alignment of well-developed sutural to penitabular processes. Specimens of Canninginopsis may be distinguished from those of all other areoligeracean genera in bearing highest relief ornamentation or spongeous wall thickenings at the distal margins of the apical and antapical horns.
Canninginopsis Cookson and Eisenack, 1962b, p.488.
Emendations: Marshall, 1990b, p.80–82; McLachlan et al. 2018, p.679–680.
Type: Cookson and Eisenack, 1962b, pl.1, fig.16, as Canninginopsis denticulata.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Cookson and Eisenack, 1962]:
Description:
Shell flat, roughly seven-sided in outline, with a slight apical prominence and an indented base. Girdle helicoid, approximately equatorial on the dorsal surface. Longitudinal furrow obliquely directed. Both surfaces of shell marked but into large fields that border both girdle and longitudinal furrow. Shell opening by the detachment of the proximal part of the epitheca.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 25:
Synopsis:
Cysts proximate, lenticular; paratabulation gonyaulacacean, indicated by alignment of low parasutural features on the autophragm; archeopyle apical, Type tA; parasulcal notch offset.
Modified description:
Shape: Lenticular; apical margin may be obtusely angular and antapical margin may have median concavity between subangular lobes.
Wall relationships: Autophragm only.
Wall features: Parasutural alignment of features of low relief conspicuous; autophragm otherwise unornamented.
Paratabulation: Indicated by archeopyle and parasutural features; gonyaulacacean, formula: 4`, 6", 6c, 5-6```, 1p, 1````, ?s. Paraplate 1```` encompasses the two antapical lobes.
Archeopyle: Apical, Type tA; transverse dimension greater than dorsal-ventral dimension; principal archeopyle suture zigzag with offset parasulcal notch; operculum free.
Paracingulum: Indicated by parallel, transverse, equatorial parasutural features.
Parasulcus: Delimited by parasutural features, which may also indicate several constituent paraplates.
Size: Intermediate to large.
Affinities:
Canninginopsis differs from Canningia in having parasutural features that indicate the paratabulation. Canningia lacks parasutural features and the paratabulation is indicated generally by the archeopyle only.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Marshall, 1990:
Emended synopsis:
Cysts proximate, lenticular; paratabulation sexiform gonyaulacoid, indicated by alignment of penitabular or parasutural projections on autophragm and outline of archeopyle suture; archeopyle apical, Type (tA), parasulcal notch offset.
Emended description:
Shape: Lenticular; ventrodorsal outline subcircular to subpentagonal, often modified by an apical and 1 or 2 antapical horns forming rounded bulges or subconical structures. Each lateral margin usually e convex, occasionally extended at its mid-length i to form a rounded bulge or horn of similar morphology to the others (Fig. 4).
Wall relationships: Autophragm only.
Wall features: Surface scabrate, granulate, or foveolate to foveoreticulate; also marked by granules, ridges or low septa aligned in penitabular or parasutural rows. Ventral surface can be unsculptured.
Paratabulation: Indicated by archeopyle and penitabular-parasutural projections; pattern sexiform gonyaulacoid. Paratabulation on ventral surface, especially in parasulcal area, often incomplete or absent. Paraplates within parasulcus offset to the right: paraplates fu and ai may or may not be in contact. Antipolar paraplate Y crescentic, mainly restricted to dorsal surface.
Archeopyle: Apical, Type (tA), principal archeopyle suture zigzag, parasulcal notch offset to the left. Accessory sutures frequently evident along lateral boundaries of polar and pre-equatorial paraplates. Operculum usually free.
Paracingulum: Indicated by an equatorial groove, and associated parasutural features.
Parasulcus: Often defined by a shallow longitudinal groove along midventral surface and associated parasutural features. Flagellar markings occasionally evident.
Size: Intermediate to large.
Remarks:
This description differs from that given by Stover and Evitt (1978; p. 25) in that there is greater variation in the ventrodorsal outline of the autocyst, sculpture on the autophragm, and distribution and morphology of the characters marking paratabulation.
Affinities:
Evitt (1985) divided the category of ventrodorsally compressed gonyaulacoids named Gv-cysts into three complexes, Areoligera, Membranophoridinium, and Canningia, which are distinguished by their wall structure and surface ornament.
Canninginopsis belongs to the Areoligera complex which is characterised by having either an autophragm or two appressed layers with the periphragm extended to form processes or septa. Paratabulation is rarely complete and is defined by parasutural, penitabular, or intratabular ornament. Taxa frequently have reduced sculpture on the ventral and dorsal surfaces relative to that around the periphery.
Of the genera assigned to the Areoligera complex by Evitt (1985), Cerbia Below 1981 and Areoligera Lejeune-Carpentier emend. Williams and Downie in Davey et al. 1966 display greatest similarity to Canninginopsis. Cerbia is ornamented with penitabular tubercles or short processes and this produces an apparent overlap in morphology with the variant of Canninginopsis with penitabular sculpture, which is C. intermedia. The species assigned to Cerbia can be distinguished from C. intermedia in that they have sculpture on the ventral surface. However, these species may prove to be cogeneric. The ventral surface of Areoligera may be featureless and the dorsal surface has rows of penitabular processes or septa arranged fields or arcs. The projections on Canninginopsis are considerably shorter and define a more complete paratabulation. Circulodinium Alberti 1961 differs from Canninginopsis in having a greater concentration of sculptural elements, grana, vermiculae, processes, on the autophragm, which mainly appear nontabulate.
Bint (1986) examined some Mid Cretaceous ceratioid cysts from the western interior of the USA, and he compared these forms with published records of ventrodorsally compressed cysts belonging to the Areoligera - Cyclonephelium complex of Wall and Evitt (1975). Some forms within this complex lacking indications of paratabulation other than the archeopyle outline are difficult to distinguish from Early Cretaceous ceratioids lacking the typical development of postcingular horns, such as some species of Pseudoceratium Gocht 1957. Bint suggested that these may be differentiated by the shape of the anterior margin of the pre-equatorial paraplate 2. He believed that this is planate on ceratioid cysts and camerate on ventrodorsally compressed gonyaulacoids. Bint considered that Canninginopsis has a gonyaulacoid paratabulation, however, noted that paraplate 2 was camerate/? planate margin (Bint, 1986, text-fig. 12). The species of Canninginopsis studied here confirm Bint`s proposal, in that the anterior margin of paraplate 2 seems to range from planate, to faintly to distinctly camerate. This places some uncertainty on this criterion for distinguishing gonyaulacoid and ceratioid cysts.
---------------------------------------------------------------------------
Emended diagnosis Fensome et al., 2019a:
Areoligeracean cysts that are proximate, with subpentagonal ambitus. Acavate. One apical horn. Antapex rounded to asymmetrical with two antapical horns. Outer wall occasionally forming spongeous thickenings or highest relief ornamentation along apical and antapical horn margins. Tabulation indicated by archaeopyle and alignment of sutural ornamentation which may be granulate, denticulate, verrucate, or spinous. Archaeopyle apical, with formula A(1–4’), operculum free; sulcal notch offset to the left.
Comparison. Canninginopsis differs from Circulodinium in having sutural alignment of granules and verrucae with less concentration of nontabulate sculptural elements on the autophragm. Canninginopsis can also be differentiated from Tenua in having low-relief sutural ornamentation rather than alignment of well-developed sutural to penitabular processes. Specimens of Canninginopsis may be distinguished from those of all other areoligeracean genera in bearing highest relief ornamentation or spongeous wall thickenings at the distal margins of the apical and antapical horns.