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Gonyaulacysta hyaloderma
Gonyaulacysta hyaloderma Deflandre, 1939b, p.144, pl.6, figs.3–4 ex Sarjeant, 1967b, p.252.
NOW Impagidinium?. Originally Palaeoperidinium (name not validly published), subsequently Gonyaulacysta, thirdly Gonyaulacysta?, fourthly Rhynchodiniopsis?, fifthly (and now) Impagidinium?. Questionable assignment: Stover and Evitt (1978, p.158) as a problematic species.
The name Palaeoperidinium hyalodermum was not validly published in Deflandre (1939b) since the generic name Palaeoperidinium was not validly published until 1967. Williams et al. (1998, p.251) accepted Sarjeant's (1967b) indirect reference to Deflandre (1939b) as indication of a type (I.C.N. Article 40.3).
Holotype: Deflandre. 1939, pl.6, figs.3-4; Jan du Chêne et al., 1986, pl.58, figs.1-5
Age: Kimmeridgian
Emended diagnosis: Gitmez, 1970, p.259
A Gonyaulacysta with thin-walled, spherical to ovoidal shell terminating in a short, blunt horn. Tabulation: 4", 6", 6c, 6""", 1p and 1"""". Plate boundaries demarcated by moderately high, delicate crests with smooth or denticulate edges. Epitract and hypotract are almost equal in size and separated by laevorotatory helicoidal cingulum. Sulcus broadening posteriorly, weakly sigmoidal. Surface of the shell smooth. Precingular archaeopyle forms by loss of plate 3".
Dimensions: Holotype: length 42 µ, breadth 35 µ; length of the apical horn 3 µ. Figured specimen: overall length 44 µ, breadth 40 µ; horn length 4 µ. Dimensions of the specimen from Eocene of Belgium (as quoted by Coninck): length 42 µ, breadth 32 µ; horn length 7 µ. According to these measurements, the dimensions of the specimens from the Kimmeridgian and Eocene are similar.
Description: Gitmez, 1970, p.259
Shell broadly ovoidal, with a short and broad horn at the apex, and the hypotract rounded. The crests separating the four apical plates meet at the apex. Plate 1" occupies the anterior prolongation of the sulcus; it is long and broadening towards the apex. Plate 2" is the largest of the apical plates and forms the apical horn together with plate 1". Six precingular plates are present; they are moderately large. Plate 6" is elongate and narrower than the others. The six postcingular plates are of variable size. Plate 1""" is the smallest, triangular in shape; plate 3""" and 4""" are larger, quadrate and occupy the whole dorsal side of the hypotract; 6""" is square in shape. A posterior intercalary plate (IP) separates plate 1""" from the single, polygonal antapical plate (1""""). The shell wall and crests are delicate.
NOW Impagidinium?. Originally Palaeoperidinium (name not validly published), subsequently Gonyaulacysta, thirdly Gonyaulacysta?, fourthly Rhynchodiniopsis?, fifthly (and now) Impagidinium?. Questionable assignment: Stover and Evitt (1978, p.158) as a problematic species.
The name Palaeoperidinium hyalodermum was not validly published in Deflandre (1939b) since the generic name Palaeoperidinium was not validly published until 1967. Williams et al. (1998, p.251) accepted Sarjeant's (1967b) indirect reference to Deflandre (1939b) as indication of a type (I.C.N. Article 40.3).
Holotype: Deflandre. 1939, pl.6, figs.3-4; Jan du Chêne et al., 1986, pl.58, figs.1-5
Age: Kimmeridgian
Emended diagnosis: Gitmez, 1970, p.259
A Gonyaulacysta with thin-walled, spherical to ovoidal shell terminating in a short, blunt horn. Tabulation: 4", 6", 6c, 6""", 1p and 1"""". Plate boundaries demarcated by moderately high, delicate crests with smooth or denticulate edges. Epitract and hypotract are almost equal in size and separated by laevorotatory helicoidal cingulum. Sulcus broadening posteriorly, weakly sigmoidal. Surface of the shell smooth. Precingular archaeopyle forms by loss of plate 3".
Dimensions: Holotype: length 42 µ, breadth 35 µ; length of the apical horn 3 µ. Figured specimen: overall length 44 µ, breadth 40 µ; horn length 4 µ. Dimensions of the specimen from Eocene of Belgium (as quoted by Coninck): length 42 µ, breadth 32 µ; horn length 7 µ. According to these measurements, the dimensions of the specimens from the Kimmeridgian and Eocene are similar.
Description: Gitmez, 1970, p.259
Shell broadly ovoidal, with a short and broad horn at the apex, and the hypotract rounded. The crests separating the four apical plates meet at the apex. Plate 1" occupies the anterior prolongation of the sulcus; it is long and broadening towards the apex. Plate 2" is the largest of the apical plates and forms the apical horn together with plate 1". Six precingular plates are present; they are moderately large. Plate 6" is elongate and narrower than the others. The six postcingular plates are of variable size. Plate 1""" is the smallest, triangular in shape; plate 3""" and 4""" are larger, quadrate and occupy the whole dorsal side of the hypotract; 6""" is square in shape. A posterior intercalary plate (IP) separates plate 1""" from the single, polygonal antapical plate (1""""). The shell wall and crests are delicate.