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Evansia janeae
Evansia janeae Piasecki, 2001, p.20,22,24,26, figs.3A-I.
Holotype: Piasecki, 2001, fig.3B.
Age: Mid Bathonian-Mid Callovian.
Original description (Piasecki, 2001)
Derivation of name: Named after my wife Jane.
Diagnosis: A proximate, acavate dinoflagellate cyst with an ovoidal main body merging into a conical, hollow apical horn with a solid distal extension. The wall is solid and hyaline with one wall layer, and the surface is laevigate with sculpture of scattered, irregular granulae to short bacculae. The density of the sculpture varies significantly from dense to absent. A significant archaeopyle is formed by the loss of three wall pieces, wuivalent to three intercalary plates. Tabulation is indicated by the archaeopyle. The surface sculpture indicates cingulum whereas regular tabulation or the sulcus is rarely reflected.
Description: The main body is wide, ovoidal and merges into a short conical to long prominent apical horn. The cavity of the main body continues into the horn, which has a solid distal extension, an apicular structure. The shape of the main body varies from ovoidal, almost spherical, via elongated ovoirdal to damond shape in lateral view. The apical horn is mostly distinguished clearly from the main body but may be reducedto a rounded apex of the epicyst. The wall is hyaline and solid with only one wall layer visible, the autophragm, of approximately 1 µm in thickness. The surface is laevigate with or without sculpture of very irregular granulae to bacculae. The dimensions of the sculptural elements are approximately 1 µm. In the presence of a dense sculpture, cingulum is indicated but proper tabulation is rarely reflected in the cyst morphology, apart from the archaeopyle. The archaeopyle is formed by the loss of a composite operculum of three plates. Two, slightly smaller plates (equivalent to the intercalary plates 1a and 3a) together with a larger central plate (2a) separate and form a characteristic 3I archaeopyle. The margins of the archaeopyle are ragged.
Size: The total length varies from 61-87 µm, average 75 µm, and the width varies from 32-60 µm, average 52µm, measured on 24 specimens. The maximum length of the apical horn is 23µm, average 15µm, based on 20 specimens with horns reasonable discriminated from the main bodies. The holotype is 80µm long and 5-µm wide. The apical horn is approximately 16 µm long. The paratype is 84µm long and 47µm wide. The apical horn is 18 µm long.
Discussion: The general pareodinoid morphology indicated the taxonomic affinities of the new species. The archaeopyle of three intercalary plates indicate the affinity of the species towards the genera Evansia and Paraevansia Below 1990 in contrast to the genus Pareodinia, which has an archaeopyle equivalent to two intercalary plates. Below (1990) separates Evansia and Paraevansia on the bsis of differences in the apical tabulation. The first apical plate of Paraevansia is very reduced and the apical plates series is therfore positioned more towards to the anterior sulcal field. Consequently, the intercalary plate series of Paraevansia is situated closer to the apex (in the sens of the topmost point of the cyst). However, the two genera are not easily distinguished when the pattern of tabulation is not expressed by the cyst morphology. due to the relative wide area between the intercalary archaeopyle and the apex in the present species, it is referred to the genus Evansia. Evansia janeae is overall similar to the other boreal species of Eansia due to the large intercalary 3I archaeopyle. The shape of E. janeae varies significantly and the variations compare to the shape of many other pareodinoid species. The wall with one visible layer (autophragm) distinguishes E. janeae from the cavate species of Evansia. The well developed apical horn combined with the non-tabulate morphology and the relatively smooth surface distinguish E. janeae from all other species of Evansia. However, the strongly sculptured specimens show similarity to Evansia zabros. The antapex of E. zabros is pointed and may indicate a second, lateral antapical horn in contrast to the rounded antapex of Evansia janeae.
Holotype: Fig 3B, MGUH, GGU sample 234049
Paratype: Fig 3A, MGUH, GGU sample 234049
Type locality: Kosmocerasdal at Charcot Bugt, Milne Land, locality 3 in figures 1 and 2 in of Callomon & Birkelund (1980).
Type stratum: Charcot Bugt Formation, Milne Land.
Age and stratigraphical range: The stratigraphical range of Evansia janeae is from the Middle Bathonian, A. ishmae Zone, to the Middle Callovian, pre-P. atletha Chronozone based on material from successions on Store Koldewey, Hold with Hope and Milne Land, East Greenland. The occurence of Evansia janeae is then of Middle Bathonian to Middle Callovian age.
Geographical occurence: Evansia janeae is recorded from Middle Jurrasic successions on Store Koldewey, Hold with Hope, Jameson Land and Milne Land in East Greenland.
Holotype: Piasecki, 2001, fig.3B.
Age: Mid Bathonian-Mid Callovian.
Original description (Piasecki, 2001)
Derivation of name: Named after my wife Jane.
Diagnosis: A proximate, acavate dinoflagellate cyst with an ovoidal main body merging into a conical, hollow apical horn with a solid distal extension. The wall is solid and hyaline with one wall layer, and the surface is laevigate with sculpture of scattered, irregular granulae to short bacculae. The density of the sculpture varies significantly from dense to absent. A significant archaeopyle is formed by the loss of three wall pieces, wuivalent to three intercalary plates. Tabulation is indicated by the archaeopyle. The surface sculpture indicates cingulum whereas regular tabulation or the sulcus is rarely reflected.
Description: The main body is wide, ovoidal and merges into a short conical to long prominent apical horn. The cavity of the main body continues into the horn, which has a solid distal extension, an apicular structure. The shape of the main body varies from ovoidal, almost spherical, via elongated ovoirdal to damond shape in lateral view. The apical horn is mostly distinguished clearly from the main body but may be reducedto a rounded apex of the epicyst. The wall is hyaline and solid with only one wall layer visible, the autophragm, of approximately 1 µm in thickness. The surface is laevigate with or without sculpture of very irregular granulae to bacculae. The dimensions of the sculptural elements are approximately 1 µm. In the presence of a dense sculpture, cingulum is indicated but proper tabulation is rarely reflected in the cyst morphology, apart from the archaeopyle. The archaeopyle is formed by the loss of a composite operculum of three plates. Two, slightly smaller plates (equivalent to the intercalary plates 1a and 3a) together with a larger central plate (2a) separate and form a characteristic 3I archaeopyle. The margins of the archaeopyle are ragged.
Size: The total length varies from 61-87 µm, average 75 µm, and the width varies from 32-60 µm, average 52µm, measured on 24 specimens. The maximum length of the apical horn is 23µm, average 15µm, based on 20 specimens with horns reasonable discriminated from the main bodies. The holotype is 80µm long and 5-µm wide. The apical horn is approximately 16 µm long. The paratype is 84µm long and 47µm wide. The apical horn is 18 µm long.
Discussion: The general pareodinoid morphology indicated the taxonomic affinities of the new species. The archaeopyle of three intercalary plates indicate the affinity of the species towards the genera Evansia and Paraevansia Below 1990 in contrast to the genus Pareodinia, which has an archaeopyle equivalent to two intercalary plates. Below (1990) separates Evansia and Paraevansia on the bsis of differences in the apical tabulation. The first apical plate of Paraevansia is very reduced and the apical plates series is therfore positioned more towards to the anterior sulcal field. Consequently, the intercalary plate series of Paraevansia is situated closer to the apex (in the sens of the topmost point of the cyst). However, the two genera are not easily distinguished when the pattern of tabulation is not expressed by the cyst morphology. due to the relative wide area between the intercalary archaeopyle and the apex in the present species, it is referred to the genus Evansia. Evansia janeae is overall similar to the other boreal species of Eansia due to the large intercalary 3I archaeopyle. The shape of E. janeae varies significantly and the variations compare to the shape of many other pareodinoid species. The wall with one visible layer (autophragm) distinguishes E. janeae from the cavate species of Evansia. The well developed apical horn combined with the non-tabulate morphology and the relatively smooth surface distinguish E. janeae from all other species of Evansia. However, the strongly sculptured specimens show similarity to Evansia zabros. The antapex of E. zabros is pointed and may indicate a second, lateral antapical horn in contrast to the rounded antapex of Evansia janeae.
Holotype: Fig 3B, MGUH, GGU sample 234049
Paratype: Fig 3A, MGUH, GGU sample 234049
Type locality: Kosmocerasdal at Charcot Bugt, Milne Land, locality 3 in figures 1 and 2 in of Callomon & Birkelund (1980).
Type stratum: Charcot Bugt Formation, Milne Land.
Age and stratigraphical range: The stratigraphical range of Evansia janeae is from the Middle Bathonian, A. ishmae Zone, to the Middle Callovian, pre-P. atletha Chronozone based on material from successions on Store Koldewey, Hold with Hope and Milne Land, East Greenland. The occurence of Evansia janeae is then of Middle Bathonian to Middle Callovian age.
Geographical occurence: Evansia janeae is recorded from Middle Jurrasic successions on Store Koldewey, Hold with Hope, Jameson Land and Milne Land in East Greenland.