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Lacrymodinium warrenii
Lacrymodinium warrenii Albert et al., 1986
Holotype: Albert et al., 1986, pl.1, figs.1-2,4; Fensome et al., 1995, figs.1-3 - p.1907.
Locus typicus: S. Folk Elder Ceek, Paskenta, California, USA
Stratum typicum: Late Oxfordian or Kimmeridgian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Lacrymodinium warrenii Albert et al., 1986, has a variably pyriform outline prolonged into an apical horn. The antapex is rounded. Tabulation is as given for the genus. It has a type I archeopyle which is unusual in being five sided.. Size: length 38-97 µm, width 22-54 µm.
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Original description: Albert et al., 1986, p. 307
Proximate dinoflagellate cyst; outline variably pyriform, prolonged apically into a stout horn; antapex broadly rounded, devoid of horns. Equatorial section in apical view subcircular, revealing no appreciable dorsoventral compression, and a narrow, moderately deep depression on left side of sulcal area. Distinct, wide paracingulum divides cyst about equally; ends offset approximately one full paracingular width. Aligned parallel to the polar axis, parasulcus does not extend an appreciable distance anteriorly from paracingulum, but broadens posteriorly, terminating at antapex.
Under the light microscope, the wall seems to consist of a single layer, except for a barely detectable, apparent separation of layers in the apical horn, visible on occasional specimens. Although we have not been able to see these two layers convincingly in specimens of L. warrenii using scanning electron microscopy, specimens of Lacrymodinium sp. clearly show a bi-layered cyst wall (pl. 2, fig. 11). These two clues suggest to us that L. warrenii probably has a similar bilayered wall. Minute (up to 3 Ám long), flexuous, hairlike processes are sparsely scattered or in somewhat penitabular arrangement on the intratabular areas of most specimens, but are absent from the surfaces of others. Denticulate, hirsute-spinose, or serrate septa (1-5 Ám high) cap low, parasutural ridges; septa and their projections commonly collapsed or folded over onto cyst wall.
Gonyaulacoid paratabulation fully or nearly fully expressed; parasutures typically most clearly defined in vicinity of paracingulum. Triple junction of A, B, and C dorsally eccentric to apical horn, which is situated along A-B parasuture; P structure, although sometimes indistinct, expressed as a plug or process of variable size and shape on tip of apical horn. Middorsal precingular (4h) separated from pentagonal intercalary (4v) by rectilinear parasuture. On ventral surface, small Iu is exsert (A contacts 2), often appearing to be anteriormost part of parasulcus. Paracingulum consists of seven paraplates (au, b, c, d, ei, eu, fi). Postcingular paraplate V has tripartite contact with paracingulum. Paraplates within parasulcus clearly visible; parasuture between fu and li not indicated. Paraplate Z divided longitudinally into Zi and Zu, extending posteriorly to antapex. Zi could easily be construed as either seventh postcingular or posterior intercalary. Antapical paraplate arrangement partiform. Antapical extremity lies at triple junction of X, Y, and Zu.
Type I archeopyle on epicyst formed by loss of large, asymmetrical, pentagonal, middorsal, anterior intercalary paraplate 4v; operculum free. Asymmetry results from a shorter parasutural boundary between 4v and 5 than between 4v and 3.
Dimensions (50 specimens): Length 38-97 Ám (mean 79 Ám); width 22-54 Ám (mean 2 Ám).
The fine elements of the surface ornament are difficult to resolve with the light microscope, even in excellently preserved specimens. Minor corrosion of the surface probably could alter their appearance appreciably, or destroy them, as may be the case for those specimens without intratabular processes. Under the light microscope, a number of specimens appear to have additional parasutures that seemingly subdivide some of the paraplates. We consider these features "artificial" because they are not constant in position and because scanning electron microscopy strongly suggests that they are the result of chance alignments of the delicate intratabular processes and parasutural septa that have collapsed against the periphragm.
Affinities:
Albert et al., 1986, p. 308, 310: Only three previously described species are likely to be confused with L. warrenii: Paragonyaulacysta borealis, P. capillosa, and Pluriarvalium osmingtonense. As noted in our generic discussion of Lacrymodinium, the degree of actual similarity is not altogether clear. Although the paratabulation of L. warrenii is in many ways similar to that of P. borealis and P. capillosa, several significant differences seem to occur in areas that were the least clearly defined on Brideaux and Fisher's specimens (Brideaux and Fisher 1976, pp. 20, 21). For example, L. warrenii has three apical, one intercalary, and seven cingular paraplates, whereas P. borealis and P. capillosa are described as having four(?) apical, two intercalary, and six cingular paraplates. Additionally, the Type 2I archeopyle with single operculum that they describe for each species is an unprecedented combination, but it is indistinct in the published photographs. Both of their species also have bi-layered walls, which they describe as endophragm and periphragm: P. capillosa with surface ornamentation similar to that of some specimens of L. warrenii, and P. borealis devoid of surface projections (similar to other specimens of L. warrenii). Paragonyaulacysta capillosa also differs from L. warrenii by being considerably larger, by having a longer apical horn, and by its prominent antapical bulge ("tripartite outline" of Brideaux and fisher).
Although, in many ways, the paratabulation described for Pluriarvalium osmingtonense (Wiggins 1975, text-fig. 7) differs from that of L. warrenii, it also has certain unusual similarities. For example, each has an elongate ventral paraplate (our Zi, Wiggins's 7''') in continuity with the right end of the paracingulum, an unusually large first postcingular(our lu, Wiggins's 1'''), a tripartite contact between V and the paracingulum, and a closely corresponding sequence of features along the dorsal midline. The many small paraplates of Wiggins's diagram and his acknowledged difficulty in determining the details of paratabulation may be due in part to the confusing visual effect, under transmitted light, of fine surface processes and septa collapsed against the periphragm, which we noted in studying Lacrymodinium with the scanning electron microscope. In neither of the published descriptions of P. osmingtonense (Sarjeant 1962; Wiggins 1975) has the wall structure been described in sufficient detail for comparison with Lacrymodinium.
Holotype: Albert et al., 1986, pl.1, figs.1-2,4; Fensome et al., 1995, figs.1-3 - p.1907.
Locus typicus: S. Folk Elder Ceek, Paskenta, California, USA
Stratum typicum: Late Oxfordian or Kimmeridgian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Lacrymodinium warrenii Albert et al., 1986, has a variably pyriform outline prolonged into an apical horn. The antapex is rounded. Tabulation is as given for the genus. It has a type I archeopyle which is unusual in being five sided.. Size: length 38-97 µm, width 22-54 µm.
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Original description: Albert et al., 1986, p. 307
Proximate dinoflagellate cyst; outline variably pyriform, prolonged apically into a stout horn; antapex broadly rounded, devoid of horns. Equatorial section in apical view subcircular, revealing no appreciable dorsoventral compression, and a narrow, moderately deep depression on left side of sulcal area. Distinct, wide paracingulum divides cyst about equally; ends offset approximately one full paracingular width. Aligned parallel to the polar axis, parasulcus does not extend an appreciable distance anteriorly from paracingulum, but broadens posteriorly, terminating at antapex.
Under the light microscope, the wall seems to consist of a single layer, except for a barely detectable, apparent separation of layers in the apical horn, visible on occasional specimens. Although we have not been able to see these two layers convincingly in specimens of L. warrenii using scanning electron microscopy, specimens of Lacrymodinium sp. clearly show a bi-layered cyst wall (pl. 2, fig. 11). These two clues suggest to us that L. warrenii probably has a similar bilayered wall. Minute (up to 3 Ám long), flexuous, hairlike processes are sparsely scattered or in somewhat penitabular arrangement on the intratabular areas of most specimens, but are absent from the surfaces of others. Denticulate, hirsute-spinose, or serrate septa (1-5 Ám high) cap low, parasutural ridges; septa and their projections commonly collapsed or folded over onto cyst wall.
Gonyaulacoid paratabulation fully or nearly fully expressed; parasutures typically most clearly defined in vicinity of paracingulum. Triple junction of A, B, and C dorsally eccentric to apical horn, which is situated along A-B parasuture; P structure, although sometimes indistinct, expressed as a plug or process of variable size and shape on tip of apical horn. Middorsal precingular (4h) separated from pentagonal intercalary (4v) by rectilinear parasuture. On ventral surface, small Iu is exsert (A contacts 2), often appearing to be anteriormost part of parasulcus. Paracingulum consists of seven paraplates (au, b, c, d, ei, eu, fi). Postcingular paraplate V has tripartite contact with paracingulum. Paraplates within parasulcus clearly visible; parasuture between fu and li not indicated. Paraplate Z divided longitudinally into Zi and Zu, extending posteriorly to antapex. Zi could easily be construed as either seventh postcingular or posterior intercalary. Antapical paraplate arrangement partiform. Antapical extremity lies at triple junction of X, Y, and Zu.
Type I archeopyle on epicyst formed by loss of large, asymmetrical, pentagonal, middorsal, anterior intercalary paraplate 4v; operculum free. Asymmetry results from a shorter parasutural boundary between 4v and 5 than between 4v and 3.
Dimensions (50 specimens): Length 38-97 Ám (mean 79 Ám); width 22-54 Ám (mean 2 Ám).
The fine elements of the surface ornament are difficult to resolve with the light microscope, even in excellently preserved specimens. Minor corrosion of the surface probably could alter their appearance appreciably, or destroy them, as may be the case for those specimens without intratabular processes. Under the light microscope, a number of specimens appear to have additional parasutures that seemingly subdivide some of the paraplates. We consider these features "artificial" because they are not constant in position and because scanning electron microscopy strongly suggests that they are the result of chance alignments of the delicate intratabular processes and parasutural septa that have collapsed against the periphragm.
Affinities:
Albert et al., 1986, p. 308, 310: Only three previously described species are likely to be confused with L. warrenii: Paragonyaulacysta borealis, P. capillosa, and Pluriarvalium osmingtonense. As noted in our generic discussion of Lacrymodinium, the degree of actual similarity is not altogether clear. Although the paratabulation of L. warrenii is in many ways similar to that of P. borealis and P. capillosa, several significant differences seem to occur in areas that were the least clearly defined on Brideaux and Fisher's specimens (Brideaux and Fisher 1976, pp. 20, 21). For example, L. warrenii has three apical, one intercalary, and seven cingular paraplates, whereas P. borealis and P. capillosa are described as having four(?) apical, two intercalary, and six cingular paraplates. Additionally, the Type 2I archeopyle with single operculum that they describe for each species is an unprecedented combination, but it is indistinct in the published photographs. Both of their species also have bi-layered walls, which they describe as endophragm and periphragm: P. capillosa with surface ornamentation similar to that of some specimens of L. warrenii, and P. borealis devoid of surface projections (similar to other specimens of L. warrenii). Paragonyaulacysta capillosa also differs from L. warrenii by being considerably larger, by having a longer apical horn, and by its prominent antapical bulge ("tripartite outline" of Brideaux and fisher).
Although, in many ways, the paratabulation described for Pluriarvalium osmingtonense (Wiggins 1975, text-fig. 7) differs from that of L. warrenii, it also has certain unusual similarities. For example, each has an elongate ventral paraplate (our Zi, Wiggins's 7''') in continuity with the right end of the paracingulum, an unusually large first postcingular(our lu, Wiggins's 1'''), a tripartite contact between V and the paracingulum, and a closely corresponding sequence of features along the dorsal midline. The many small paraplates of Wiggins's diagram and his acknowledged difficulty in determining the details of paratabulation may be due in part to the confusing visual effect, under transmitted light, of fine surface processes and septa collapsed against the periphragm, which we noted in studying Lacrymodinium with the scanning electron microscope. In neither of the published descriptions of P. osmingtonense (Sarjeant 1962; Wiggins 1975) has the wall structure been described in sufficient detail for comparison with Lacrymodinium.