Back
Homotryblium vallum
Homotryblium vallum Stover, 1977
Holotype: Stover, 1977, pl.3, figs.45-48
Locus typicus: Corehole 5/5B, Blake Plateau, Western N Atlantic
Stratum typicum: Middle Oligocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Homotryblium vallum Stover, 1977, has 26 processes. Periphragm smooth to faintly ornamented. Processes composed of two or more slender tubes arranged in cylindrical or rectilinear groups. Distal part of processes branched, digitate and normally expanded: rosettes at proximal end of processes are clearly evident to barely discernible. Paratabulation is 4', 6", 6c, 6"’. 1p, 1"”, 2s. Some of paracingular processes are taeniate. Only single tubed process on the cyst is the anterior sulcal. Homotryblium vallum differs from H.floripes in being smaller, having a smooth or nearly smooth periphragm and in having taeniate processes in the paracingular series. It is differentiated from Homotryblium plectilum on the taeniate processes. However, the two occur together and there are transitional forms. H.plectilum occurs mainly in the older part of the section, H.vallum mainly in the younger. Overall size: 70-80 µm, central body 47-53 µm, process length 13-20 µm, width at midlength 5-14 µm.
--------------------------------------------------
Original description: Stover, 1977, p. 80
Cysts are chorate with a subspherical body bearing 26 intratabular processes. Endophragm and periphragm are appressed between processes and the periphragm is smooth to very faintly ornamented. Processes composed typically of two or more slender tubes arranged in cylindrical or rectilinear groups. Distal part of processes branched, digitate and normally expanded; rosettes at proximal end of processes are clearly evident to barely discernible. Paratabulation indicated by intratabular processes and additionally by epicystal opercular pieces; gonyaulacacean, formula: 4',6'', 6c,6''',1p,1'''', 2s. Principal archeopyle suture of the combination type A+3A+6P archeopyle occurs along the apical margin of paracingulum and is straight except in midventral area where it follows the outlineof the parasulcal tab and the depression to the right of it. Paracingulum immediately posterior to archeopyle margin and indicated by a transverse row of six processes of which some are taeniate. Anterior and posterior limits of parasulcus indicatedby the anterior parasulcal process, which is the only single-tubed process on the hypocyst, and posterior parasulcal process, respectively. Posterior intercalary, posterior parasulcal and antapical processes arranged like a triangle with the antapical process at the apex.
Overall size 70 to 80 Ám, body diameter 47 to 53 Ám; processes 13 to 20 Ám long, width at midlength 5 to 14 Ám, exclusive of anterior parasulcal process.
Affinities: Stover, 1977, p. 80
Homotryblium vallum differs from H. floripes (Deflandre and Cookson) Stover, 1975 by being smaller, having a smooth or nearly smooth periphragm rather than a granular periphragm, and by having taeniate processes in the paracingular series. The presence of paracingular taeniate processes alsoerves to distinguis H. vallum from H. plectilum Drugg and Loeblich 1967. However, these two species occur together and transitional forms were observed. As indicated on the stratigraphic chart, H. plectilum occurs mainly in the older part of the section whereas H. vallum occurs mainly in the younger part.
Holotype: Stover, 1977, pl.3, figs.45-48
Locus typicus: Corehole 5/5B, Blake Plateau, Western N Atlantic
Stratum typicum: Middle Oligocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Homotryblium vallum Stover, 1977, has 26 processes. Periphragm smooth to faintly ornamented. Processes composed of two or more slender tubes arranged in cylindrical or rectilinear groups. Distal part of processes branched, digitate and normally expanded: rosettes at proximal end of processes are clearly evident to barely discernible. Paratabulation is 4', 6", 6c, 6"’. 1p, 1"”, 2s. Some of paracingular processes are taeniate. Only single tubed process on the cyst is the anterior sulcal. Homotryblium vallum differs from H.floripes in being smaller, having a smooth or nearly smooth periphragm and in having taeniate processes in the paracingular series. It is differentiated from Homotryblium plectilum on the taeniate processes. However, the two occur together and there are transitional forms. H.plectilum occurs mainly in the older part of the section, H.vallum mainly in the younger. Overall size: 70-80 µm, central body 47-53 µm, process length 13-20 µm, width at midlength 5-14 µm.
--------------------------------------------------
Original description: Stover, 1977, p. 80
Cysts are chorate with a subspherical body bearing 26 intratabular processes. Endophragm and periphragm are appressed between processes and the periphragm is smooth to very faintly ornamented. Processes composed typically of two or more slender tubes arranged in cylindrical or rectilinear groups. Distal part of processes branched, digitate and normally expanded; rosettes at proximal end of processes are clearly evident to barely discernible. Paratabulation indicated by intratabular processes and additionally by epicystal opercular pieces; gonyaulacacean, formula: 4',6'', 6c,6''',1p,1'''', 2s. Principal archeopyle suture of the combination type A+3A+6P archeopyle occurs along the apical margin of paracingulum and is straight except in midventral area where it follows the outlineof the parasulcal tab and the depression to the right of it. Paracingulum immediately posterior to archeopyle margin and indicated by a transverse row of six processes of which some are taeniate. Anterior and posterior limits of parasulcus indicatedby the anterior parasulcal process, which is the only single-tubed process on the hypocyst, and posterior parasulcal process, respectively. Posterior intercalary, posterior parasulcal and antapical processes arranged like a triangle with the antapical process at the apex.
Overall size 70 to 80 Ám, body diameter 47 to 53 Ám; processes 13 to 20 Ám long, width at midlength 5 to 14 Ám, exclusive of anterior parasulcal process.
Affinities: Stover, 1977, p. 80
Homotryblium vallum differs from H. floripes (Deflandre and Cookson) Stover, 1975 by being smaller, having a smooth or nearly smooth periphragm rather than a granular periphragm, and by having taeniate processes in the paracingular series. The presence of paracingular taeniate processes alsoerves to distinguis H. vallum from H. plectilum Drugg and Loeblich 1967. However, these two species occur together and transitional forms were observed. As indicated on the stratigraphic chart, H. plectilum occurs mainly in the older part of the section whereas H. vallum occurs mainly in the younger part.