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Kilwacysta semiseptata
Kilwacysta semiseptata Schrank, 2005, p.62,64, pl.6, figs.2–6.
Holotype: Schrank, 2005, pl.6, figs.2,4.
Age: Tithonian.
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Original description (Schrank, 2005):
Kilwacysta semiseptata sp. nov. Plate 6, figs. 2-6
Holotype. Gold-coated specimen in glycerin jelly slide no. AYZ7, England Finder M39NE, TUB catalogue number Pnl08, Plate 6, figs. 2,4.
Type locality. Tingutinguti section near Tendaguru, southeast Tanzania.
Type stratum. Trigonia smeei Bed at sample level Tin911. Repository. Technische Universitat Berlin (TUB), Germany.
Derivation of name. Semi- (Latin for half), septata (Latin for having a septum).
Diagnosis. Skolochorate dinoflagellate cysts, central body ellipsoidal. Phragma laevigate, archeopyle apical. Major process complexes of the pre- and postcingular series arising from oval ridges that become shallower or are reduced towards the precingular area. There are six major precingular and probably six postcingular process complexes; the equatorial region is largely devoid of processes. The antapical process is prominent in lateral or dorsoventral view; it is different from the other processes in having a tubiform base. Processes are highly variable within one specimen ranging from slender types with bifurcate or digitate extremities to broad, membraneous types that may be deeply furcate and/or irregularly branched at various levels. Process endings are commonly expanded and divided into several small spines.
Description. Cysts are variable,thin-walled,easily folded or damaged and are preserved in different orientations. Maximum diameter of central body is about 50% of total diameter. Deeply incised accessory archeopyle sutures (length up to 13 µm) separating the six precingular plates may be present. Septate, arcuate ridges (maximum diameter about 13 µm) at the base of a major process complex may be perforate and linked with the phragma by a few small rootletlike threads (diameter about 1 µm or less), which are visible under the SEM. Processes include the following types: (1) solid, slender, simple (e.g. 1.5 x 3.1 µm) most of its length terminating into a digitate tip; (2) solid, slender, simple, bifurcating at about half and three quarters length; (3) broad, flat, membraneous process stem (width about 5 to 8 µm). Branching of secondary slender spines may occur at any level, the main stem terminates into an expanded digitate structure consisting of typically 3 to 5 or more individual spines, sometimes with a denticulate comb-shaped ending in the middle. Lateral spines may be denticulate and tend to be bent outward, sometimes in an anchor-like fashion. Distal trabeculae within a process complex are rare.
Dimensions. Holotype: central body 56 x 43 µm, maximum diameter 112 µm. Maximum diameter of central body 39 (48) 56 µm, total diameter 75 (90) 112 µm, 15 specimens measured in different orientations.
Discussion. Oligosphaeridium diliculum Davey 1982 from the Ryazanian of Denmark and England is simlar to Kilwacysta semiseptata because of its complex process endings, but K. semiseptata can be distinguished by its broad membraneous processes arising from arcuate ridges, as opposed to the tubiform processes of the former.
Present record. Trigonia smeei Bed (Tin9g to Tin912).
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Holotype: Schrank, 2005, pl.6, figs.2,4.
Age: Tithonian.
------------------------------
Original description (Schrank, 2005):
Kilwacysta semiseptata sp. nov. Plate 6, figs. 2-6
Holotype. Gold-coated specimen in glycerin jelly slide no. AYZ7, England Finder M39NE, TUB catalogue number Pnl08, Plate 6, figs. 2,4.
Type locality. Tingutinguti section near Tendaguru, southeast Tanzania.
Type stratum. Trigonia smeei Bed at sample level Tin911. Repository. Technische Universitat Berlin (TUB), Germany.
Derivation of name. Semi- (Latin for half), septata (Latin for having a septum).
Diagnosis. Skolochorate dinoflagellate cysts, central body ellipsoidal. Phragma laevigate, archeopyle apical. Major process complexes of the pre- and postcingular series arising from oval ridges that become shallower or are reduced towards the precingular area. There are six major precingular and probably six postcingular process complexes; the equatorial region is largely devoid of processes. The antapical process is prominent in lateral or dorsoventral view; it is different from the other processes in having a tubiform base. Processes are highly variable within one specimen ranging from slender types with bifurcate or digitate extremities to broad, membraneous types that may be deeply furcate and/or irregularly branched at various levels. Process endings are commonly expanded and divided into several small spines.
Description. Cysts are variable,thin-walled,easily folded or damaged and are preserved in different orientations. Maximum diameter of central body is about 50% of total diameter. Deeply incised accessory archeopyle sutures (length up to 13 µm) separating the six precingular plates may be present. Septate, arcuate ridges (maximum diameter about 13 µm) at the base of a major process complex may be perforate and linked with the phragma by a few small rootletlike threads (diameter about 1 µm or less), which are visible under the SEM. Processes include the following types: (1) solid, slender, simple (e.g. 1.5 x 3.1 µm) most of its length terminating into a digitate tip; (2) solid, slender, simple, bifurcating at about half and three quarters length; (3) broad, flat, membraneous process stem (width about 5 to 8 µm). Branching of secondary slender spines may occur at any level, the main stem terminates into an expanded digitate structure consisting of typically 3 to 5 or more individual spines, sometimes with a denticulate comb-shaped ending in the middle. Lateral spines may be denticulate and tend to be bent outward, sometimes in an anchor-like fashion. Distal trabeculae within a process complex are rare.
Dimensions. Holotype: central body 56 x 43 µm, maximum diameter 112 µm. Maximum diameter of central body 39 (48) 56 µm, total diameter 75 (90) 112 µm, 15 specimens measured in different orientations.
Discussion. Oligosphaeridium diliculum Davey 1982 from the Ryazanian of Denmark and England is simlar to Kilwacysta semiseptata because of its complex process endings, but K. semiseptata can be distinguished by its broad membraneous processes arising from arcuate ridges, as opposed to the tubiform processes of the former.
Present record. Trigonia smeei Bed (Tin9g to Tin912).
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