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Eocladopyxis peniculata
Eocladopyxis peniculata Morgenroth, 1966; Emendation: McLean, 1976, p.348, as a revised description.
Holotype: Morgenroth 1966a, Pl. 2, fig. 2,3
Locus typicus: Katharinenhof Fehmarn.
Stratum typicum: Lower Eocene (?2).
Age: Early Eocene
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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.
Eocladopyxis peniculata Morgenroth, 1966a, emend. McLean, 1976. According to McLean (1976, p.348), Eocladopyxis peniculata has numerous solid, acuminate processes. Tabulation is 4', 0a, 6", 6c, 6"’, 1p, 1"”. Archeopyle epitractal type 4A + 6P. Cyst divided along principal archeopyle suture between precingular and cingular plates into epitractal and hypotractal hemispheres. Anterior sulcal projects above 1c to form a prominent mid-ventral projection on hypocyst. Surface granulate to spinose. Sometimes appears microreticulate. About 9 processes per plate. Size: Morgenroth’s material main body diameter 37-40 µm, processes 8 µm. Main body diameter 52-75 µm, processes 10-15 µm.
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Original diagnosis: The same as for the genus Eocladopyxis.
Original description: Morgenroth 1966a, p. 7: Eocladopyxis peniculatum
The spherical strongly granular theca consists of plates which tend to be separated by small sutures. On each plate arise many solid pointed processes (the sutures are completely devoid of processes). The apical pole is easily recognizable through 3 plates - the small rounded 1' plate is enclosed by the two elongate pentagonal plates, 2' and 3'. Bordering on the girdle are ?5 postequatorial plates and the antapex is composed of one pentagonal plate. The relatively broad longitudinal furrow terminates in an end plate on the antapical plate.
Remarks: On one specimen the trapezoidal plate 3'' is absent, so that this could have been the position of the pylome.
Measurements: Theca: 38 microns (37/40 microns), process length: 8 microns (6 measurements). Number of specimens examined : 6.
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Revised description: McLean 1976, p. 348-349
Cyst spheroidal with numerous randomly arranged, intratabularly distributed solid, sharp-tipped spines. Cyst bi-layered; outer layer occurs in shapes of plate-equivalents superimposed on inner layer indicating tabulation of: 4', 0a, 6", 6c, 6"', 1p, l"". Archeopyle epitractal (Type 4a + 6P); cyst divides along principal archeopyle suture between precingular and cingular plate-equivalents into epitractal (compound operculum) and hypotractal hemispheres; epitractal hemisphere separates along secondary archeopyle sutures into its individual plate-equivalents; hypotractal hemisphere displays tabulation but remains intact. Cingulum levorotatory, ends displaced vertically and transversely up to one and one-half cingulum widths. Sulcus broad posteriorly, narrows anteriorly; is divided into generalized anterior and posterior areas separated by a W-shaped suture which reflects posterior margins of the right and left sulcal plate-equivalents (text-figure l; plate l, figure l0) . Anterior sulcal plate-equivalent extends above level of the lc plate-equivalent as a prominent mid-ventral projection on hypotract. Cyst inner wall layer 0.5-0.75Á thick, transparent, and visible only at high magnification by oil immersion, or phase contrast, along edges of separated plate-equivalents. Outer wall layer ca. l .5Á thick, occurring in shapes of plate-equivalents superimposed on transparent inner layer; externally granular-spinose; grana ca. 0.5Á in height and diameter and may coalesce, imparting a microreticulate appearance to cyst exterior; spines are intratabularly distributed and occur several per plate-equivalent (mean = 9); spines are solid and sharp-tipped, and arise from a raised rootlike base; are nearly constant m size on a specimen.
Dimensions. Observed range of 150 specimens from the Virginia coastal plain: main body diameter 52-75Á (mean 63Á); spines l0-l5Á long (mean 12.5Á) with a mean midpoint diameter of 1Á and basal diameter of 3-5Á. The main body diameter of Morgenroth's specimens is 37-40Á and spine lengths are 8Á.
Discussion and comparison with similar species: McLean 1976, p. 348-349
I tried to obtain the holotype of Eocladopyxis peniculalum to compare with specimens from the Maryland and Virclinia coastal plain, but was unable to do so. Both Morgenroth and the Geologisch- Palaontologisches Institute und Museum, der Universitat Kiel (writtencommunication) claimed they did not have Morgenroth's slides and preparations. Professor W. R. Evitt, of Stanford University did, however, obtain some of Morgenroth's slides and confirmed that the specimens from Maryland and Virginia are Eocladopyxis peniculatum.
Eocladopyxis peniculatum resembles the modern bioluminescent thecate dinoflagellate Pyrodinium bahamense Plate, 1906, in that: (1) its plate-equivalents compare in shape almost precisely with those of the theca of P. bahamense: (2) each species displays a relatively large apical closing pore platelet; (3) each displays an asymmetry of the hypotheca (hypotract) whereby the large posterior sulcal platelet extends posteriorly to contact an enlarged fifth postcingular plate, and (4) each displays a distinctive pentagonal antapical plate.
The juvenile theca of Pyrodinium bahamense (Wall and Dale, 1969, p. 1 44) displays a minute 1 '' ' plate-equivalent. That of Eocladopyxls peniculatum is weakly developed (plate 1, figure 11) and would have been overlooked, had there been no modern species. Eocladopyxis peniculatum resembles the resting spore (= cyst) of Pyrodinium bahamense but differs by having: (1) hypotractal tabulation which is lacking in the cyst of P. bahamense; (2) simple, solid, sharp-tipped spines, whereas those of P. bahamense are tubular with closed, slightly enlarged capitate, sometimes asymmetrically lobed tips; and (3) a Type 4a + 6P archeopyle in which the epitract dissociates completely into its individual plate-equivalents, whereas that of the modern sPecies has a Tvoe 2A + 6P archeoovle.
The fossil previously known as Hemicystodinium zoharyi (Rossignol,1962) Wall,1967, has been shown by Wall and Dale (1969) to represent the resting spore (= cyst) of Pyrodinium bahamense. Thus, the published geologic record of P. bahamense has been traced back to the Pleistocene. Wall and Dale (1969) recovered P. bahamense cysts from samples believed to be of Middle Miocene age. and reported that specimens have been found in the Eocene London Clay.
In spite of similarities in Eocladopyxis peniculatum and Pyrodinium bahamense, I choose not to assign the fossil to the modern genus. Until details of pyrodinioid dinoflagellate evolution are better known, I believe fossil and modern species should be retained in separate genera.
Eocladopyxis peniculatum differs from species of Homotryblium Davey and Williams, 1969, by having: (1) solid. sharp-tipped, intratabularly distributed spines as opposed to intratabular, plate-centered, cyiindrical to tubiform open-ended processes; and (2) a Type 4a + 6P archeopyle as opposed to a Type 2A + 6P.
Holotype: Morgenroth 1966a, Pl. 2, fig. 2,3
Locus typicus: Katharinenhof Fehmarn.
Stratum typicum: Lower Eocene (?2).
Age: Early Eocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Eocladopyxis peniculata Morgenroth, 1966a, emend. McLean, 1976. According to McLean (1976, p.348), Eocladopyxis peniculata has numerous solid, acuminate processes. Tabulation is 4', 0a, 6", 6c, 6"’, 1p, 1"”. Archeopyle epitractal type 4A + 6P. Cyst divided along principal archeopyle suture between precingular and cingular plates into epitractal and hypotractal hemispheres. Anterior sulcal projects above 1c to form a prominent mid-ventral projection on hypocyst. Surface granulate to spinose. Sometimes appears microreticulate. About 9 processes per plate. Size: Morgenroth’s material main body diameter 37-40 µm, processes 8 µm. Main body diameter 52-75 µm, processes 10-15 µm.
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Original diagnosis: The same as for the genus Eocladopyxis.
Original description: Morgenroth 1966a, p. 7: Eocladopyxis peniculatum
The spherical strongly granular theca consists of plates which tend to be separated by small sutures. On each plate arise many solid pointed processes (the sutures are completely devoid of processes). The apical pole is easily recognizable through 3 plates - the small rounded 1' plate is enclosed by the two elongate pentagonal plates, 2' and 3'. Bordering on the girdle are ?5 postequatorial plates and the antapex is composed of one pentagonal plate. The relatively broad longitudinal furrow terminates in an end plate on the antapical plate.
Remarks: On one specimen the trapezoidal plate 3'' is absent, so that this could have been the position of the pylome.
Measurements: Theca: 38 microns (37/40 microns), process length: 8 microns (6 measurements). Number of specimens examined : 6.
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Revised description: McLean 1976, p. 348-349
Cyst spheroidal with numerous randomly arranged, intratabularly distributed solid, sharp-tipped spines. Cyst bi-layered; outer layer occurs in shapes of plate-equivalents superimposed on inner layer indicating tabulation of: 4', 0a, 6", 6c, 6"', 1p, l"". Archeopyle epitractal (Type 4a + 6P); cyst divides along principal archeopyle suture between precingular and cingular plate-equivalents into epitractal (compound operculum) and hypotractal hemispheres; epitractal hemisphere separates along secondary archeopyle sutures into its individual plate-equivalents; hypotractal hemisphere displays tabulation but remains intact. Cingulum levorotatory, ends displaced vertically and transversely up to one and one-half cingulum widths. Sulcus broad posteriorly, narrows anteriorly; is divided into generalized anterior and posterior areas separated by a W-shaped suture which reflects posterior margins of the right and left sulcal plate-equivalents (text-figure l; plate l, figure l0) . Anterior sulcal plate-equivalent extends above level of the lc plate-equivalent as a prominent mid-ventral projection on hypotract. Cyst inner wall layer 0.5-0.75Á thick, transparent, and visible only at high magnification by oil immersion, or phase contrast, along edges of separated plate-equivalents. Outer wall layer ca. l .5Á thick, occurring in shapes of plate-equivalents superimposed on transparent inner layer; externally granular-spinose; grana ca. 0.5Á in height and diameter and may coalesce, imparting a microreticulate appearance to cyst exterior; spines are intratabularly distributed and occur several per plate-equivalent (mean = 9); spines are solid and sharp-tipped, and arise from a raised rootlike base; are nearly constant m size on a specimen.
Dimensions. Observed range of 150 specimens from the Virginia coastal plain: main body diameter 52-75Á (mean 63Á); spines l0-l5Á long (mean 12.5Á) with a mean midpoint diameter of 1Á and basal diameter of 3-5Á. The main body diameter of Morgenroth's specimens is 37-40Á and spine lengths are 8Á.
Discussion and comparison with similar species: McLean 1976, p. 348-349
I tried to obtain the holotype of Eocladopyxis peniculalum to compare with specimens from the Maryland and Virclinia coastal plain, but was unable to do so. Both Morgenroth and the Geologisch- Palaontologisches Institute und Museum, der Universitat Kiel (writtencommunication) claimed they did not have Morgenroth's slides and preparations. Professor W. R. Evitt, of Stanford University did, however, obtain some of Morgenroth's slides and confirmed that the specimens from Maryland and Virginia are Eocladopyxis peniculatum.
Eocladopyxis peniculatum resembles the modern bioluminescent thecate dinoflagellate Pyrodinium bahamense Plate, 1906, in that: (1) its plate-equivalents compare in shape almost precisely with those of the theca of P. bahamense: (2) each species displays a relatively large apical closing pore platelet; (3) each displays an asymmetry of the hypotheca (hypotract) whereby the large posterior sulcal platelet extends posteriorly to contact an enlarged fifth postcingular plate, and (4) each displays a distinctive pentagonal antapical plate.
The juvenile theca of Pyrodinium bahamense (Wall and Dale, 1969, p. 1 44) displays a minute 1 '' ' plate-equivalent. That of Eocladopyxls peniculatum is weakly developed (plate 1, figure 11) and would have been overlooked, had there been no modern species. Eocladopyxis peniculatum resembles the resting spore (= cyst) of Pyrodinium bahamense but differs by having: (1) hypotractal tabulation which is lacking in the cyst of P. bahamense; (2) simple, solid, sharp-tipped spines, whereas those of P. bahamense are tubular with closed, slightly enlarged capitate, sometimes asymmetrically lobed tips; and (3) a Type 4a + 6P archeopyle in which the epitract dissociates completely into its individual plate-equivalents, whereas that of the modern sPecies has a Tvoe 2A + 6P archeoovle.
The fossil previously known as Hemicystodinium zoharyi (Rossignol,1962) Wall,1967, has been shown by Wall and Dale (1969) to represent the resting spore (= cyst) of Pyrodinium bahamense. Thus, the published geologic record of P. bahamense has been traced back to the Pleistocene. Wall and Dale (1969) recovered P. bahamense cysts from samples believed to be of Middle Miocene age. and reported that specimens have been found in the Eocene London Clay.
In spite of similarities in Eocladopyxis peniculatum and Pyrodinium bahamense, I choose not to assign the fossil to the modern genus. Until details of pyrodinioid dinoflagellate evolution are better known, I believe fossil and modern species should be retained in separate genera.
Eocladopyxis peniculatum differs from species of Homotryblium Davey and Williams, 1969, by having: (1) solid. sharp-tipped, intratabularly distributed spines as opposed to intratabular, plate-centered, cyiindrical to tubiform open-ended processes; and (2) a Type 4a + 6P archeopyle as opposed to a Type 2A + 6P.