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Heslertonia pellucida
Heslertonia pellucida Gitmez, 1970
Holotype: Gitmez, 1970, pl.14, fig.2, text-fig.26
Locus typicus: Kimmeridge Clay from 100 ft. above the second dolerite sill, east of Digg, Staffin Bay, Skye (SS 627), England
Stratum typicum: Early Kimmeridgian
Original diagnosis: Gitmez, 1970, p.297-298
Heslertonia having a spheroidal to polyhedral shell without an apical horn. Tabulation: 4", 6", 6c, 6""", 1p, 1pv and 1"""". Borders of the plates characteristically formed by broad winged edges. Cingulum broad and slightly laevorotatory; sulcus broad and short, mainly extending on the hypotract. Shell wall transparent and surface smooth. Precingular archaeopy]e present, formed by loss of plate 3".
Dimensions: Holotype: shell diameter 30x30 Ám; height of the crests 4-8 Ám; breadth of the cingulum 5-6 Ám. Dimensions of the second specimen: shell diameter 28x 28 Ám; height of the crests 6-8 Ám; breadth of the cingulum 5-6 Ám.
Original description: Gitmez, 1970, p.298
A small proximochorate cyst, characterized by the high crests rising from the plate boundaries. Neither an apical horn nor any appendages are developed.
Four apical and six precingular plates form the epitract. Plate 1" is elongate; the other three apical plates are polygonal in shape. Plate 3" is larger than plates 2" and 4", which are almost equal in size. No anterior intercalary plate was observed. The precingular plates are polygonal and more or less uniform in size.
The slightly laevorotatory cingulum is occupied by six cingular plates: plate 1c is smallest, plate 4c is longest of the cingular plates. The ends of the cingulum are widely separated by a broad sulcus.
Six postcingular plates are present. Plate 1""" is reduced to accommodate the posterior intercalary plate 1p. The other postcingular plates are relatively large. The two posterior intercalary plates are small; plate 1pv is tetragonal and placed in the posterior prolongation of the sulcus. A single large antapical plate occupies the antapex.
Affinities:
Gitmez, 1970, p. 298: The remarkably well preserved, but transparent specimens were observed in the basal Kimmeridgian assemblages (one from Stretham and one from Staffin Bay). Tabulation is difficult to determine because of the high crests between the plates and the transparent shell wall.
This new species of Heslertonia differs from the only previously known species of the genus (H. heslertonensis) in the form of its crests and the tabulation. This is the first species of the genus recorded from Jurassic strata. Although only two specimens were found, it was considered that their excellent preservation and clearly distinguishable characters fully justified their differentiation as a second species of this genus.
Poulsen 1996, p. 84
Heslertonia? pellucida Gitmez 1970, Pl. 15, Fig. 9
Remarks. Heslertonia? pellucida is here regarded as a provisionally accepted species of Heslertonia since it may have a precingular archeopyle.
Recorded occurrences.
Denmark: Scriniodinium crystallinum Zone, Subzone d - Gochteodinia villosa Zone, Rotosphaeropsis thula Subzone.
Poland: Bimammatum - Sokolovi Zones.
Holotype: Gitmez, 1970, pl.14, fig.2, text-fig.26
Locus typicus: Kimmeridge Clay from 100 ft. above the second dolerite sill, east of Digg, Staffin Bay, Skye (SS 627), England
Stratum typicum: Early Kimmeridgian
Original diagnosis: Gitmez, 1970, p.297-298
Heslertonia having a spheroidal to polyhedral shell without an apical horn. Tabulation: 4", 6", 6c, 6""", 1p, 1pv and 1"""". Borders of the plates characteristically formed by broad winged edges. Cingulum broad and slightly laevorotatory; sulcus broad and short, mainly extending on the hypotract. Shell wall transparent and surface smooth. Precingular archaeopy]e present, formed by loss of plate 3".
Dimensions: Holotype: shell diameter 30x30 Ám; height of the crests 4-8 Ám; breadth of the cingulum 5-6 Ám. Dimensions of the second specimen: shell diameter 28x 28 Ám; height of the crests 6-8 Ám; breadth of the cingulum 5-6 Ám.
Original description: Gitmez, 1970, p.298
A small proximochorate cyst, characterized by the high crests rising from the plate boundaries. Neither an apical horn nor any appendages are developed.
Four apical and six precingular plates form the epitract. Plate 1" is elongate; the other three apical plates are polygonal in shape. Plate 3" is larger than plates 2" and 4", which are almost equal in size. No anterior intercalary plate was observed. The precingular plates are polygonal and more or less uniform in size.
The slightly laevorotatory cingulum is occupied by six cingular plates: plate 1c is smallest, plate 4c is longest of the cingular plates. The ends of the cingulum are widely separated by a broad sulcus.
Six postcingular plates are present. Plate 1""" is reduced to accommodate the posterior intercalary plate 1p. The other postcingular plates are relatively large. The two posterior intercalary plates are small; plate 1pv is tetragonal and placed in the posterior prolongation of the sulcus. A single large antapical plate occupies the antapex.
Affinities:
Gitmez, 1970, p. 298: The remarkably well preserved, but transparent specimens were observed in the basal Kimmeridgian assemblages (one from Stretham and one from Staffin Bay). Tabulation is difficult to determine because of the high crests between the plates and the transparent shell wall.
This new species of Heslertonia differs from the only previously known species of the genus (H. heslertonensis) in the form of its crests and the tabulation. This is the first species of the genus recorded from Jurassic strata. Although only two specimens were found, it was considered that their excellent preservation and clearly distinguishable characters fully justified their differentiation as a second species of this genus.
Poulsen 1996, p. 84
Heslertonia? pellucida Gitmez 1970, Pl. 15, Fig. 9
Remarks. Heslertonia? pellucida is here regarded as a provisionally accepted species of Heslertonia since it may have a precingular archeopyle.
Recorded occurrences.
Denmark: Scriniodinium crystallinum Zone, Subzone d - Gochteodinia villosa Zone, Rotosphaeropsis thula Subzone.
Poland: Bimammatum - Sokolovi Zones.