Back
Invertocysta lacrymosa
Invertocysta lacrymosa Edwards, 1984
Holotype: Edwards, 1984, pl.3, fig.4a-b
Paratype: Edwards, 1984
Locus typicus: DSDP Site 555, Rockall Plateau, E North Atlantic
Stratum typicum: Middle-Late Miocene
Original description: Edwards 1984, p. 586
Diagnosis: Cyst cavate. Ovoidal endocyst connected at apical boss to lip of bowl-shaped pericyst. Periphragm and endophragm appressed midventrally. Periphragm turned inward on dorsal side around opening representing 3"". Wall surface smooth to shagreenate with poorly to moderate development parasutural ridges. Paratabulation gonyaulacacean, exact formula undetermined. Archeopyle
precingular, type P, 3"" only. Dimensions of holotype, pericyst length 79 µm, pericyst width 85 µm, endocyst length 52 µm, endocyst width 44 µm.
Description: Cyst cavate. Endocyst ovoidal to ellipsoidal with apical boss connecting endocyst to inner lip of pericyst. Pericyst bowl-shaped with inward-turning lip at opening of bowl on dorsal side. Periphragm and endophragm appressed midventrally. Opening on dorsal side variable in size, shape, and position ranging from a small opening on the dorsal epicyst to en opening of approximately the same size and shape as the endocyst to an opening that is considerably larger and broader than the endocyst. Wall surfaces smooth to shagreenate with faint to moderately well-developed parasutural ridges. Paracingulum displaced antapically on dorsal side, outline of paracingulum is the shape of a hemicircle with the flat side centered across the ventral side. Paratabulation gonyaulacacean, excact formula undetermined but presumably similar to that of I.tabulata, paraplates analogous to 3""",4""",5""" and 1"""" on I.tabulata are clearly visable on some specimens of I. lacrymosa. Archeopyle precingular type P, 3"" only on endocyst, large opening corresponding to 3"" on pericyst.
Afinities:
Edwards 1984, p. 586
Invertocysta lacrymosa differs from I. tabulata in posessing a bowl- shaped, as opposed to disk-shaped, pericyst, in having less definition in paratabulation and in having a less "droopy" paracingulum. It differs from Thalassiphora delicata Williams and Downie 1966, emend. Eaton 1976, in that the wall layers of I. lacrymosa are appressed midventrally and the large dorsal opening represents 3"". In T delicata, the wall layers are appressed middorsally and the large ventral opening represents 1"". I. lacrymosa is distinguished from Amiculosphaera umbracula Harland 1979, by the appression of periphragm and endophragm in the hypocyst of the latter.
Discussion: This form shows a wide range of variation in size, shape, degree of definition of paratabulation, and size, shape, and position of dorsal opening. As a rough trend, the middle Miocene specimens have smaller openings than late Miocene specimens. The specimens illustrated here are typical of the Rockall material. The specimens illustrated by Habib (1971) and Harland (1979) are end members in the limits of variation.
Holotype: Edwards, 1984, pl.3, fig.4a-b
Paratype: Edwards, 1984
Locus typicus: DSDP Site 555, Rockall Plateau, E North Atlantic
Stratum typicum: Middle-Late Miocene
Original description: Edwards 1984, p. 586
Diagnosis: Cyst cavate. Ovoidal endocyst connected at apical boss to lip of bowl-shaped pericyst. Periphragm and endophragm appressed midventrally. Periphragm turned inward on dorsal side around opening representing 3"". Wall surface smooth to shagreenate with poorly to moderate development parasutural ridges. Paratabulation gonyaulacacean, exact formula undetermined. Archeopyle
precingular, type P, 3"" only. Dimensions of holotype, pericyst length 79 µm, pericyst width 85 µm, endocyst length 52 µm, endocyst width 44 µm.
Description: Cyst cavate. Endocyst ovoidal to ellipsoidal with apical boss connecting endocyst to inner lip of pericyst. Pericyst bowl-shaped with inward-turning lip at opening of bowl on dorsal side. Periphragm and endophragm appressed midventrally. Opening on dorsal side variable in size, shape, and position ranging from a small opening on the dorsal epicyst to en opening of approximately the same size and shape as the endocyst to an opening that is considerably larger and broader than the endocyst. Wall surfaces smooth to shagreenate with faint to moderately well-developed parasutural ridges. Paracingulum displaced antapically on dorsal side, outline of paracingulum is the shape of a hemicircle with the flat side centered across the ventral side. Paratabulation gonyaulacacean, excact formula undetermined but presumably similar to that of I.tabulata, paraplates analogous to 3""",4""",5""" and 1"""" on I.tabulata are clearly visable on some specimens of I. lacrymosa. Archeopyle precingular type P, 3"" only on endocyst, large opening corresponding to 3"" on pericyst.
Afinities:
Edwards 1984, p. 586
Invertocysta lacrymosa differs from I. tabulata in posessing a bowl- shaped, as opposed to disk-shaped, pericyst, in having less definition in paratabulation and in having a less "droopy" paracingulum. It differs from Thalassiphora delicata Williams and Downie 1966, emend. Eaton 1976, in that the wall layers of I. lacrymosa are appressed midventrally and the large dorsal opening represents 3"". In T delicata, the wall layers are appressed middorsally and the large ventral opening represents 1"". I. lacrymosa is distinguished from Amiculosphaera umbracula Harland 1979, by the appression of periphragm and endophragm in the hypocyst of the latter.
Discussion: This form shows a wide range of variation in size, shape, degree of definition of paratabulation, and size, shape, and position of dorsal opening. As a rough trend, the middle Miocene specimens have smaller openings than late Miocene specimens. The specimens illustrated here are typical of the Rockall material. The specimens illustrated by Habib (1971) and Harland (1979) are end members in the limits of variation.