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Labyrinthodinium truncatum
Labyrinthodinium truncatum Piasecki, 1980, p.67,70, pl.2, figs.9-11; pl.3, fig.2; pl.6, figs.3-4. Emendation: de Verteuil and Norris, 1996a, p.150.
Holotype: Piasecki, 1980, pl.2, figs.9-11; Fensome et al., 1995, figs.1-3 - p.1855; Fauconnier and Masure, 2004, pl.51, figs.5-6.
Paratypes: Piasecki, 1980
Locus typicus: Gram Bore (DGU file 141 423), Gram, Denmark
Stratum typicum: Middle Miocene
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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.
Labyrinthodinium truncatum Piasecki, 1980. According to de Verteuil and Norris (1996, p. 150), this species is small, proximate to proximochorate and spherical, with apical archeopyle. The autoblast comprises homogeneous pedium ca 0.2 µm thick and spongy luxuriae ca. 0.25 to 4.0 µm thick. Processes variably developed from laevigate to scabrate tegillum with scattered microgranules, from low, blade-like septa <1.0 µm high, through numerous, nontabular, hollow virgae ca. 2.5 µm long and 1.0 µm wide to fewer, larger, intratabular, membranous hollow processes, up to 10 µm long and supported by solid ridges along their length. On some specimens, the tegillum forms discontinuous septa that partially join processes proximally, forming an open, incomplete reticulum over the spongy luxuriae. Size: diameter 23-40 µm, process length 4-10 µm, wall thickness 1-3 µm.
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Original description: Piasecki, 1980, p. 67.
Diagnosis: Small chorate cysts with spherical main body, composed of two wall layers. Endophragma is hyalin and structureless, periphragma is smooth to spongeous at the surface of the main body, and smooth with scattered microgranulaes when forming crests and processes. Periphragma form an open reticulum of crests from which membraneous processes arise. All the processes are equal length and slightly expanded distally into small platforms. The archaeopyle is large and polygonal of type (tA).
Description (annotated): Endophragma is constant thickness, while periphragma may be thin an smooth or thick and spongeous. The wall thickness range from 1-3 Á, mainly because of the variation of periphragma. The two wall layers are not clearly separable when periphragma is thin and smooth. The crests on the surface of the cysts may either form a dense reticulum with a large number of processes or a rude pattern with open meshes and few processes. The reticulum may reflect a undeterminable paratabulation, because some of the crests appear to form a superior pattern from which the processes arise. Further, the archaeopyle suture does not cross the crests, which are conformable with archaeopyle margin and partly with the accessory archaeopyle sutures. The processes are formed of several adjoining crests or membranes, and are all of the same length on one cyst.
They are expanded distally building up a small platform. No structures reflecting paratabulation, paracingulum or parasulcus have been observed, except for the archaeopyle sutures. The archaeopyle is apical: type (tA). It is large and polygonal, and small accessory sutures are present along the margin.
Dimensions: Holotype: diameter 25 Ám, length of processes 5 Ám, wall thickness 1 Ám. Range: diameter 23(29)40 Ám, proces length 4(6)10 Ám, wall thickness 1-3 Ám.
Affinities:
Piasecki, 1980: These cysts do not belong to Cordosphaeridium (Eisenack) Davey, because they do not have intratabular fibrous processes and a precingular archaeopyle.
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Emended diagnosis: de Verteuil and Norris, 1996, p. 150
Cysts small, proximate or proximochorate and spherical, with apical archeopyle Type (tA). Autoblast comprises homogeneous pedium ca. 0.2Ám thick and spongy luxuriae ca. 0.25 to 4.0Ám thick. Appendages variably developed from laevigate to scabrate tegillum with scattered micro-
granules, from low blade-like septa < 1.0Ám high, through numerous nontabular hollow virgae ca. 2.5Ám long and 1.0Ám wide, to fewer, larger, intratabular, membranous hollow processes, up to 10Ám long, and supported by solid ridges along their length. On some specimens the tegillum forms discontinuous septa that partially join processes proximally, forming an open, incomplete reticulum over the spongy luxuriae.
Dimensions: Maximum diameter, excluding appendages, 17(27.8)36Ám; wall thickness 0.25 to 2.0Ám; appendages 1.0 to 10.0Ám. Forty-five specimens measured.
Discussion: de Verteuil and Norris, 1996, p. 150
The species is here emended primarily to include specimens having appendages less than 4Ám and that are here assigned to Labyrinthodinium truncatum subsp. modicum subsp. nov. The precise nature of the distinctive wall structure of this species is difficult to describe regardless of the terminology used, and SEM and TLM photomicrographs should be referred to in comparisons with other taxa. We recognize two infra-specific taxa within Labyrinthodinium truncatum because specimens with short and numerous appendages tend to occur most often in the lower part of the species' stratigraphic range and stratigraphically preceed the morphotype having fewer, larger processes with well developed platforms.
Comparison:de Verteuil and Norris, 1996, p. 150
As a species, Labyrinthodinium truncatum is difficult to confuse with any other Neogene dinoflagellate taxon. It is perhaps most similar to Cordosphaeridium minimum sensu Benedek and Sarjeant 1981, which is also small and has an apical archeopyle and tubiform processes. However, the latter species lacks the spongy luxuriae and septate reticulum characteristic of Labyrinthodinium truncatum.
Remarks: de Verteuil and Norris, 1996, p. 150
Specimens of Labyrinthodinium truncatum subsp. truncatum from the type material in the Danish Miocene range beyond the upper size limit of Salisbury Embayment specimens measured by us. The emended diagnosis thus includes those specimens. While most specimens of Labyrinthodinium truncatum subsp. truncatum have an overall greater diameter than specimens of Labyrinthodinium truncatum subsp. modicum, the range of variability and mean autoblast diameter for both subspecies is about the same. However, among specimens of Labyrinthodinium truncatum subsp. truncatum, as defined by appendage length, specimens with autoblast diameters near the top of the autoblast diameter size range, tend to have thicker spongy luxuriae and longer processes than those at the lower end of the range.
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Holotype: Piasecki, 1980, pl.2, figs.9-11; Fensome et al., 1995, figs.1-3 - p.1855; Fauconnier and Masure, 2004, pl.51, figs.5-6.
Paratypes: Piasecki, 1980
Locus typicus: Gram Bore (DGU file 141 423), Gram, Denmark
Stratum typicum: Middle Miocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Labyrinthodinium truncatum Piasecki, 1980. According to de Verteuil and Norris (1996, p. 150), this species is small, proximate to proximochorate and spherical, with apical archeopyle. The autoblast comprises homogeneous pedium ca 0.2 µm thick and spongy luxuriae ca. 0.25 to 4.0 µm thick. Processes variably developed from laevigate to scabrate tegillum with scattered microgranules, from low, blade-like septa <1.0 µm high, through numerous, nontabular, hollow virgae ca. 2.5 µm long and 1.0 µm wide to fewer, larger, intratabular, membranous hollow processes, up to 10 µm long and supported by solid ridges along their length. On some specimens, the tegillum forms discontinuous septa that partially join processes proximally, forming an open, incomplete reticulum over the spongy luxuriae. Size: diameter 23-40 µm, process length 4-10 µm, wall thickness 1-3 µm.
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Original description: Piasecki, 1980, p. 67.
Diagnosis: Small chorate cysts with spherical main body, composed of two wall layers. Endophragma is hyalin and structureless, periphragma is smooth to spongeous at the surface of the main body, and smooth with scattered microgranulaes when forming crests and processes. Periphragma form an open reticulum of crests from which membraneous processes arise. All the processes are equal length and slightly expanded distally into small platforms. The archaeopyle is large and polygonal of type (tA).
Description (annotated): Endophragma is constant thickness, while periphragma may be thin an smooth or thick and spongeous. The wall thickness range from 1-3 Á, mainly because of the variation of periphragma. The two wall layers are not clearly separable when periphragma is thin and smooth. The crests on the surface of the cysts may either form a dense reticulum with a large number of processes or a rude pattern with open meshes and few processes. The reticulum may reflect a undeterminable paratabulation, because some of the crests appear to form a superior pattern from which the processes arise. Further, the archaeopyle suture does not cross the crests, which are conformable with archaeopyle margin and partly with the accessory archaeopyle sutures. The processes are formed of several adjoining crests or membranes, and are all of the same length on one cyst.
They are expanded distally building up a small platform. No structures reflecting paratabulation, paracingulum or parasulcus have been observed, except for the archaeopyle sutures. The archaeopyle is apical: type (tA). It is large and polygonal, and small accessory sutures are present along the margin.
Dimensions: Holotype: diameter 25 Ám, length of processes 5 Ám, wall thickness 1 Ám. Range: diameter 23(29)40 Ám, proces length 4(6)10 Ám, wall thickness 1-3 Ám.
Affinities:
Piasecki, 1980: These cysts do not belong to Cordosphaeridium (Eisenack) Davey, because they do not have intratabular fibrous processes and a precingular archaeopyle.
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Emended diagnosis: de Verteuil and Norris, 1996, p. 150
Cysts small, proximate or proximochorate and spherical, with apical archeopyle Type (tA). Autoblast comprises homogeneous pedium ca. 0.2Ám thick and spongy luxuriae ca. 0.25 to 4.0Ám thick. Appendages variably developed from laevigate to scabrate tegillum with scattered micro-
granules, from low blade-like septa < 1.0Ám high, through numerous nontabular hollow virgae ca. 2.5Ám long and 1.0Ám wide, to fewer, larger, intratabular, membranous hollow processes, up to 10Ám long, and supported by solid ridges along their length. On some specimens the tegillum forms discontinuous septa that partially join processes proximally, forming an open, incomplete reticulum over the spongy luxuriae.
Dimensions: Maximum diameter, excluding appendages, 17(27.8)36Ám; wall thickness 0.25 to 2.0Ám; appendages 1.0 to 10.0Ám. Forty-five specimens measured.
Discussion: de Verteuil and Norris, 1996, p. 150
The species is here emended primarily to include specimens having appendages less than 4Ám and that are here assigned to Labyrinthodinium truncatum subsp. modicum subsp. nov. The precise nature of the distinctive wall structure of this species is difficult to describe regardless of the terminology used, and SEM and TLM photomicrographs should be referred to in comparisons with other taxa. We recognize two infra-specific taxa within Labyrinthodinium truncatum because specimens with short and numerous appendages tend to occur most often in the lower part of the species' stratigraphic range and stratigraphically preceed the morphotype having fewer, larger processes with well developed platforms.
Comparison:de Verteuil and Norris, 1996, p. 150
As a species, Labyrinthodinium truncatum is difficult to confuse with any other Neogene dinoflagellate taxon. It is perhaps most similar to Cordosphaeridium minimum sensu Benedek and Sarjeant 1981, which is also small and has an apical archeopyle and tubiform processes. However, the latter species lacks the spongy luxuriae and septate reticulum characteristic of Labyrinthodinium truncatum.
Remarks: de Verteuil and Norris, 1996, p. 150
Specimens of Labyrinthodinium truncatum subsp. truncatum from the type material in the Danish Miocene range beyond the upper size limit of Salisbury Embayment specimens measured by us. The emended diagnosis thus includes those specimens. While most specimens of Labyrinthodinium truncatum subsp. truncatum have an overall greater diameter than specimens of Labyrinthodinium truncatum subsp. modicum, the range of variability and mean autoblast diameter for both subspecies is about the same. However, among specimens of Labyrinthodinium truncatum subsp. truncatum, as defined by appendage length, specimens with autoblast diameters near the top of the autoblast diameter size range, tend to have thicker spongy luxuriae and longer processes than those at the lower end of the range.
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