Back
Lithodinia sagena
Lithodinia sagena Duxbury, 1980, p.127, pl.3, figs.6,9,12–13. Emendation: Harding, 1990b, p.35, as Meiourogonyaulax sagena.
NOW Ellipsoidictyum. Originally Lithodinia, subsequently Meiourogonyaulax, thirdly (and now) Ellipsoidictyum. This species was retained in Ellipsoidictyum Klement, 1960, by Williams et al., 1993, who incorrectly cited it as a new combination.
Holotype: Duxbury, 1980, pl.3, figs. 6,9,12
Locus typicus: Speeton, England
Stratum typicum: Barremian
Original diagnosis: Duxbury, 1980, p. 127
A thin-walled species of Lithodinia which has a spheroidal endocyst bearing a low surface reticulum. The reticulum may be fine or coarse, entire or degenerate. A delicate pericyst completely envelopes the thicker endocyst and the body layers are attached along the distal margin of the reticulum. The pericyst has regularly denticulate crests which mark out a typically gonyaulacacean paratabulation pattern. The archeopyle is apical, tetratabular and the operculum is sometimes attached in the parasulcal region.
Observed Dimensions: Holotype--44 x 52 µm. Overall--55 (48) 44 x 61 (49) 44 µm.
Affinities:
Duxbury, 1980, p. 127: This species most closely resembles Cassiculosphaeridia reticulata Davey, 1969 in size, shape and in possessing a low reticulum. The presence of denticulate parasutural crests marking out a gonyaulacacean paratabulation, however, dictates its inclusion in Lithodinia. Both the endocyst reticulum and the parasutural crests are quite variable. The reticulum may be fine, regular and entire but equally may be coarse, irregular and degenerate. The parasutural crests may vary in height and the denticles may be slender, long and closely spaced or may be broad-based, short and widely separated.
The parasutural crestal pattern appears to bear no relationship to the underlying endocyst reticulum. Consequently, long, straight parasutural crests, particularly on the dorsal surface and bordering the paracingulum, are often seen to cut directly across the reticular ramifications beneath.
NOW Ellipsoidictyum. Originally Lithodinia, subsequently Meiourogonyaulax, thirdly (and now) Ellipsoidictyum. This species was retained in Ellipsoidictyum Klement, 1960, by Williams et al., 1993, who incorrectly cited it as a new combination.
Holotype: Duxbury, 1980, pl.3, figs. 6,9,12
Locus typicus: Speeton, England
Stratum typicum: Barremian
Original diagnosis: Duxbury, 1980, p. 127
A thin-walled species of Lithodinia which has a spheroidal endocyst bearing a low surface reticulum. The reticulum may be fine or coarse, entire or degenerate. A delicate pericyst completely envelopes the thicker endocyst and the body layers are attached along the distal margin of the reticulum. The pericyst has regularly denticulate crests which mark out a typically gonyaulacacean paratabulation pattern. The archeopyle is apical, tetratabular and the operculum is sometimes attached in the parasulcal region.
Observed Dimensions: Holotype--44 x 52 µm. Overall--55 (48) 44 x 61 (49) 44 µm.
Affinities:
Duxbury, 1980, p. 127: This species most closely resembles Cassiculosphaeridia reticulata Davey, 1969 in size, shape and in possessing a low reticulum. The presence of denticulate parasutural crests marking out a gonyaulacacean paratabulation, however, dictates its inclusion in Lithodinia. Both the endocyst reticulum and the parasutural crests are quite variable. The reticulum may be fine, regular and entire but equally may be coarse, irregular and degenerate. The parasutural crests may vary in height and the denticles may be slender, long and closely spaced or may be broad-based, short and widely separated.
The parasutural crestal pattern appears to bear no relationship to the underlying endocyst reticulum. Consequently, long, straight parasutural crests, particularly on the dorsal surface and bordering the paracingulum, are often seen to cut directly across the reticular ramifications beneath.