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Capisocysta lata
Capisocysta lata, Head, 1998b, p.802,806-807 (fig.1, nos.1,3,5; fig.2, nos.1-6; fig.3, nos.1-12; fig.4, nos.1-15)
Holotype: Head, 1998b, fig.1, no.1; fig.2, nos.1-2.
Stratigraphic range: Upper lower Pliocene of eastern England and the Bahamas, through present day.
Type locality: below mud pit in the Clino borehole (24°36'07"N, 79°10'4l"W), about 75 km west of Andros Island, on the west margin of the Great Bahama Bank.
Age: Early Pliocene-Holocene.
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Original description: [Head, 1998b]:
Diagnosis:
Spherical cysts with loose outer diaphanous layer and thicker inner wall whose outer surface is smooth to granulate. Tabulation expressed extensively on hypocyst, with individual loss of plates 2-6"', lp, ps, and 1"". Sulcal plates ls and rs and postcingular plate 1 ''' usually remain attached to epicyst forming a hyposulcal tab. Width of posterior sulcal plate (ps) does not exceed that of left and right sulcal plates combined. Plate 4"' has a monothigmate, rectilinear posterior margin that contacts an undivided antapical plate (1 '" ').
Description:
Cysts are spherical and proximate, and have a thin (less than 0.3 μm) inner wall layer whose outer surface varies from smooth to granulate. Undehisced specimens are nearly always covered with a loose, diaphanous layer which is often absent in dehisced specimens (but remnants are present on the holotype, Fig. 2.1). Occasionally, the diaphanous layer is replaced by small, preservational? pustules scattered over the surface (Fig. 3.3). Undehisced specimens usually contain an accumulation body ("omphalos" of Dorhofer and Davies, 1980) variably positioned within the cyst (Fig. 3.6). Tabulation is expressed only by pre-formed lines of weakness, these being visible as pale, narrow lines on undehisced specimens (Fig. 3.6) and which control the discrete separation of plates in dehisced specimens. These lines are absent from the epicyst, are weakly and incompletely developed on the sulcus, and are fully developed elsewhere on the hypocyst, facilitating complete dissociation into constituent plates as follows: five postcingular (2-6’’’), one posterior sulcal (ps), one posterior intercalary (lp), and one antapical (1’’’’). These plates form a compound hypotractal archeopyle, with no apparent preferential order of plate loss. The right and left sulcal plates (rs and ls) and first postcingular plate (1’’’) nearly always remain attached to the epicyst as a hyposulcal tab. Only rarely does the tab separate from the epicyst (Fig. 3.9), leaving a shallow, arcuate recess in the epicyst margin which perhaps demarcates the anterior margin of the left (and right?) sulcal plate. Plates of the hyposulcal tab are usually completely fused, but an angular notch on the posterior margin of the hyposulcal tab, always to the right of center, delimits the shared contact of left and right sulcal plates and corresponds to a projection on the contacting margin of the posterior sulcal plate (which fully detaches). The left and right sulcal plates are occasionally partly delimited by lines of weakness. Rarely, the first postcingular plate is nearly fully separated (Fig. 2.5, 2.6). It tapers anteriorly to a truncated point but it is uncertain whether this contacts the cingulum. The sulcus is quite strongly inclined to the right on the hypocyst. The posterior sulcal plate (ps), which anteriorly abuts the hyposulcal tab, is the same width as the ls and rs combined. Its posterior margin is geniculate and dithigmate, contacting 1’’’’ on the longer side and 5’’’ on the shorter side: it is the smallest of those plates released routinely during dehiscence. There are six postcingular plates of which 2’’’ and 6’’’ are relatively small, 6’’’ being approximately triangular. Plates 3’’’, 4’’’, and 5’’’ are larger and approximately rectangular. Plate 4’’’ has a monothigmate rectilinear posterior margin and is mid-dorsally positioned. Plates 3’’’ and 5’’’ are similar in size and both are camerate, having characteristic arcuate indentations at their posterioventral comers where they contact plates lp and ps respectively. Plate 5’’’ always has a smaller indentation than 3’’’. The posterior intercalary (lp) is relatively small and comparable in size to 2’’’ and 6’’’. The antapical plate (1’’’’) is quinqueform and large although somewhat smaller than 3’’’ or 5’’’. The cingulum is slightly laevorotatory. It is indicated only by the shared margin of the postcingular series and the epicyst. Slight angularities on the epicyst margin correspond to junctions of the postcingular series. Some plate comers on the hypocyst are extended into minute, acute projections that intercalate with minutely rounded comers on adjacent plates. Although difficult to interpret for all plates, acute projections on the anterior margins of those in the postcingular series consistently point towards the dorsal surface so that the corresponding angles of adjacent plates are always minutely rounded. The anterior margin of the dorsally located 4' '' is minutely rounded at both angles (e.g., Figs. 2.1, 2.2, 3.1, 3.2).
Dimensions:
Holotype: maximum diameter of epicyst, 41 μm. Range based on Bahamas sample CUS-Kll: maximum diameter of undehisced cysts (excluding diaphanous outer layer) 40(43.0)46 μm, n = 12; maximum diameter of epicyst (excluding hyposulcal tab) in dehisced cysts, 41(47.9)56 μm, n = 21.
Thirty-three specimens were measured.
Affinities:
Geonettia clineae, described from the Miocene of Maryland (de Verteuil and Norris, 1996a), differs in having a much larger posterior sulcal plate (labelled 2p in de Verteuil and Norris), plates that dissociate on the epicyst as well as the hypocyst, and a reflected apical pore complex. In G. clineae the wall surface is fibrilar, and a diaphanous outer layer has not been reported. Capisocysta lyellii has a plate pair instead of a single plate at the antapex, and the posterior margin of 4’’’ is geniculate and dithigmate, not rectilinear and monothigmate as in C. lata. See also under Comparison for C. lyellii.
Discussion: The presence and direction of acute projections on the anterior margins of the postcingular series are comparable to those found on C. lyellii and Geonettia. This pattern follows the expected imbrication style for gonyaulacaleans (Fensome et al., 1993, 1996; de Verteuil and Norris, 1996a), with plate 4"' as a keystone, assuming that the corresponding plate overlap on the theca opposes the direction of acute projections on the cyst.
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Occurrence:
In the Clino borehole, Bahamas, present in all six samples from the lower Pliocene interval (494.39-476.40 mbmp) which is assignable to chron C2Ar (3.58-4.18 Ma) and is thus late early Pliocene (Eberli et al., 1997). Also present in all eight samples from the upper Pliocene interval (262.18-220.48 mbmp) of the Clino borehole, comprising 0.4 to 14 percent of the dinoflagellate assemblages. This interval is estimated to be about 2.1-2.3 Ma and occurs within chron C2r2r (late late Pliocene) according to the integrated age model of Eberli et al. (1997). In the Coralline Crag Formation, eastern England, occurs rarely (e.g., Fig. 3.1, 3.2) in all four samples (NQ1-NQ4) of the Ramsholt Member (ca. 3.8-3.6 Ma; late early Pliocene; see Head, 1997). Specimens were not observed in the overlying Sudbourne Member, which is also of Pliocene age. In Phosphorescence Bay, Puerto Rica, recorded rarely (Fig. 4.4-4.15) from a single surface-sediment sample. The cysts were recently living, as shown by the presence, of protoplasts (Fig. 4.5). Living cysts have also been found in Obidos Lagoon (39°25'N, 9°12'W) on the western coast of Portugal (D. Wall, personal commun.).
Autecology:
Capisocysta lata is rare to common in tropical periplatform carbonates in the Pliocene in the Clino borehole, Bahamas. These sediments accumulated on the platform slope but predominantly originate from the platform top where C. lata probably lived. Details of the sedimentology and dinoflagellates for the Clino borehole are given in Westphal et al. (in press). In eastern England, C. lata is consistently present, but not common, in silty, carbonate-rich sands that comprise the Ramsholt Member of the Coralline Crag Formation. This member is considered broadly warm temperate and was deposited at a minimum water depth. of 50 m (see Head, 1997). Capisocysta lata is known as a living cyst in Phosphorescent Bay, Puerto Rico, where rare specimens have been found in sediment at a water depth of 3 m. The climate here is tropical, the sediments are rich in carbonates, and salinities average 36 parts per thousand (Wall et al., 1977). Living cysts reported from Obidos Lagoon, Portugal (D. Wall, pers. commun.) show that the ecological range of this species extends into warm-temperate environments today. Therefore C. lata has a known paleoecological range of tropical through warm temperate. It clearly thrived in carbonate-rich environments, probably on the inner to middle shelf and on the tops of carbonate platforms. Temperature and other requirements of C. lata appear rather similar to those of G. clineae (de Verteuil and Norris, 1996a) and, like G. clineae and its living relative P. zaharyi, C. lata may have formed blooms.
Holotype: Head, 1998b, fig.1, no.1; fig.2, nos.1-2.
Stratigraphic range: Upper lower Pliocene of eastern England and the Bahamas, through present day.
Type locality: below mud pit in the Clino borehole (24°36'07"N, 79°10'4l"W), about 75 km west of Andros Island, on the west margin of the Great Bahama Bank.
Age: Early Pliocene-Holocene.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Head, 1998b]:
Diagnosis:
Spherical cysts with loose outer diaphanous layer and thicker inner wall whose outer surface is smooth to granulate. Tabulation expressed extensively on hypocyst, with individual loss of plates 2-6"', lp, ps, and 1"". Sulcal plates ls and rs and postcingular plate 1 ''' usually remain attached to epicyst forming a hyposulcal tab. Width of posterior sulcal plate (ps) does not exceed that of left and right sulcal plates combined. Plate 4"' has a monothigmate, rectilinear posterior margin that contacts an undivided antapical plate (1 '" ').
Description:
Cysts are spherical and proximate, and have a thin (less than 0.3 μm) inner wall layer whose outer surface varies from smooth to granulate. Undehisced specimens are nearly always covered with a loose, diaphanous layer which is often absent in dehisced specimens (but remnants are present on the holotype, Fig. 2.1). Occasionally, the diaphanous layer is replaced by small, preservational? pustules scattered over the surface (Fig. 3.3). Undehisced specimens usually contain an accumulation body ("omphalos" of Dorhofer and Davies, 1980) variably positioned within the cyst (Fig. 3.6). Tabulation is expressed only by pre-formed lines of weakness, these being visible as pale, narrow lines on undehisced specimens (Fig. 3.6) and which control the discrete separation of plates in dehisced specimens. These lines are absent from the epicyst, are weakly and incompletely developed on the sulcus, and are fully developed elsewhere on the hypocyst, facilitating complete dissociation into constituent plates as follows: five postcingular (2-6’’’), one posterior sulcal (ps), one posterior intercalary (lp), and one antapical (1’’’’). These plates form a compound hypotractal archeopyle, with no apparent preferential order of plate loss. The right and left sulcal plates (rs and ls) and first postcingular plate (1’’’) nearly always remain attached to the epicyst as a hyposulcal tab. Only rarely does the tab separate from the epicyst (Fig. 3.9), leaving a shallow, arcuate recess in the epicyst margin which perhaps demarcates the anterior margin of the left (and right?) sulcal plate. Plates of the hyposulcal tab are usually completely fused, but an angular notch on the posterior margin of the hyposulcal tab, always to the right of center, delimits the shared contact of left and right sulcal plates and corresponds to a projection on the contacting margin of the posterior sulcal plate (which fully detaches). The left and right sulcal plates are occasionally partly delimited by lines of weakness. Rarely, the first postcingular plate is nearly fully separated (Fig. 2.5, 2.6). It tapers anteriorly to a truncated point but it is uncertain whether this contacts the cingulum. The sulcus is quite strongly inclined to the right on the hypocyst. The posterior sulcal plate (ps), which anteriorly abuts the hyposulcal tab, is the same width as the ls and rs combined. Its posterior margin is geniculate and dithigmate, contacting 1’’’’ on the longer side and 5’’’ on the shorter side: it is the smallest of those plates released routinely during dehiscence. There are six postcingular plates of which 2’’’ and 6’’’ are relatively small, 6’’’ being approximately triangular. Plates 3’’’, 4’’’, and 5’’’ are larger and approximately rectangular. Plate 4’’’ has a monothigmate rectilinear posterior margin and is mid-dorsally positioned. Plates 3’’’ and 5’’’ are similar in size and both are camerate, having characteristic arcuate indentations at their posterioventral comers where they contact plates lp and ps respectively. Plate 5’’’ always has a smaller indentation than 3’’’. The posterior intercalary (lp) is relatively small and comparable in size to 2’’’ and 6’’’. The antapical plate (1’’’’) is quinqueform and large although somewhat smaller than 3’’’ or 5’’’. The cingulum is slightly laevorotatory. It is indicated only by the shared margin of the postcingular series and the epicyst. Slight angularities on the epicyst margin correspond to junctions of the postcingular series. Some plate comers on the hypocyst are extended into minute, acute projections that intercalate with minutely rounded comers on adjacent plates. Although difficult to interpret for all plates, acute projections on the anterior margins of those in the postcingular series consistently point towards the dorsal surface so that the corresponding angles of adjacent plates are always minutely rounded. The anterior margin of the dorsally located 4' '' is minutely rounded at both angles (e.g., Figs. 2.1, 2.2, 3.1, 3.2).
Dimensions:
Holotype: maximum diameter of epicyst, 41 μm. Range based on Bahamas sample CUS-Kll: maximum diameter of undehisced cysts (excluding diaphanous outer layer) 40(43.0)46 μm, n = 12; maximum diameter of epicyst (excluding hyposulcal tab) in dehisced cysts, 41(47.9)56 μm, n = 21.
Thirty-three specimens were measured.
Affinities:
Geonettia clineae, described from the Miocene of Maryland (de Verteuil and Norris, 1996a), differs in having a much larger posterior sulcal plate (labelled 2p in de Verteuil and Norris), plates that dissociate on the epicyst as well as the hypocyst, and a reflected apical pore complex. In G. clineae the wall surface is fibrilar, and a diaphanous outer layer has not been reported. Capisocysta lyellii has a plate pair instead of a single plate at the antapex, and the posterior margin of 4’’’ is geniculate and dithigmate, not rectilinear and monothigmate as in C. lata. See also under Comparison for C. lyellii.
Discussion: The presence and direction of acute projections on the anterior margins of the postcingular series are comparable to those found on C. lyellii and Geonettia. This pattern follows the expected imbrication style for gonyaulacaleans (Fensome et al., 1993, 1996; de Verteuil and Norris, 1996a), with plate 4"' as a keystone, assuming that the corresponding plate overlap on the theca opposes the direction of acute projections on the cyst.
---------------------------------------
Occurrence:
In the Clino borehole, Bahamas, present in all six samples from the lower Pliocene interval (494.39-476.40 mbmp) which is assignable to chron C2Ar (3.58-4.18 Ma) and is thus late early Pliocene (Eberli et al., 1997). Also present in all eight samples from the upper Pliocene interval (262.18-220.48 mbmp) of the Clino borehole, comprising 0.4 to 14 percent of the dinoflagellate assemblages. This interval is estimated to be about 2.1-2.3 Ma and occurs within chron C2r2r (late late Pliocene) according to the integrated age model of Eberli et al. (1997). In the Coralline Crag Formation, eastern England, occurs rarely (e.g., Fig. 3.1, 3.2) in all four samples (NQ1-NQ4) of the Ramsholt Member (ca. 3.8-3.6 Ma; late early Pliocene; see Head, 1997). Specimens were not observed in the overlying Sudbourne Member, which is also of Pliocene age. In Phosphorescence Bay, Puerto Rica, recorded rarely (Fig. 4.4-4.15) from a single surface-sediment sample. The cysts were recently living, as shown by the presence, of protoplasts (Fig. 4.5). Living cysts have also been found in Obidos Lagoon (39°25'N, 9°12'W) on the western coast of Portugal (D. Wall, personal commun.).
Autecology:
Capisocysta lata is rare to common in tropical periplatform carbonates in the Pliocene in the Clino borehole, Bahamas. These sediments accumulated on the platform slope but predominantly originate from the platform top where C. lata probably lived. Details of the sedimentology and dinoflagellates for the Clino borehole are given in Westphal et al. (in press). In eastern England, C. lata is consistently present, but not common, in silty, carbonate-rich sands that comprise the Ramsholt Member of the Coralline Crag Formation. This member is considered broadly warm temperate and was deposited at a minimum water depth. of 50 m (see Head, 1997). Capisocysta lata is known as a living cyst in Phosphorescent Bay, Puerto Rico, where rare specimens have been found in sediment at a water depth of 3 m. The climate here is tropical, the sediments are rich in carbonates, and salinities average 36 parts per thousand (Wall et al., 1977). Living cysts reported from Obidos Lagoon, Portugal (D. Wall, pers. commun.) show that the ecological range of this species extends into warm-temperate environments today. Therefore C. lata has a known paleoecological range of tropical through warm temperate. It clearly thrived in carbonate-rich environments, probably on the inner to middle shelf and on the tops of carbonate platforms. Temperature and other requirements of C. lata appear rather similar to those of G. clineae (de Verteuil and Norris, 1996a) and, like G. clineae and its living relative P. zaharyi, C. lata may have formed blooms.