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Cousteaudinium aubryae
Cousteaudinium aubryae de Verteuil and Norris, 1996a, p.111-112,114, pl.1, figs.1-9; pl.2, figs.1-12; pl.18, figs.2-3.
Holotype: de Verteuil and Norris, 1996a, pl.1, figs.1-3,6,9.
Locus typicus: Popes Creek Section, Potomac River, Popes Creek, Charles County, Maryland.
Stratum typicum: Lower Miocene Fairhaven Member of the Calvert Formation
Erikania cf. dynamica Morgenroth 1966, Benedek 1972:37, pl. 8, fig.10.
Thalassiphora?sp. 1 Powell 1988, pl.4,figs.15,16,19,20.-Head et al. 1989c: 496, pl. 6, figs. 7-10
Dinocyst sp. 6 Manum et al. 1989, pl. 8, figs. 8, 9
Thalassiphora gonoperforata nom. nud. Rusbult ans Strauss 1992:158, pl. 8, figs. 9-10.- Lund et al. 1993:29, pl. 1, fig. 13
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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.
Cousteaudinium aubryae de Verteuil and Norris, 1996. According to de Verteuil and Norris (1996), this is an intermediate to large cribroperidinioidean cyst, circumcavate and variably chorate, rarely skolochorate without limbate cavation. Tabulation delimited by broad based, box-like intratabular processes, one per field, excepting the cingular series and some ventral hyposomal fields, which lack processes. Endoblast smooth, periblast shagreenate to microstriate and variably perforate; both thin. Processes distally denticulate. Archeopyle rounded, apical. Size: maximum endoblast diameter 40-62 µm, length 40-58 µm, width 38-60 µm. Maximum periblast diameter 79-110 µm, length of processes 1-35 µm.
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Original diagnosis: deVerteuil and Norris, 1996, p. 111: Cousteaudinium aubryae
Intermediate to large cribroperidinioidean cysts, circumcavate and variably chorate; rarely skolochorate without limbate cavation. Tabulation delimited by broad based, box-like intratabular processes, one per field, excepting the cingular series and some ventral hyposomal fields, which lack processes. Endoblast smooth, periblast shagreenate to microstriate and variably perforate; both thin. Processes distally denticulate; archeopyle rounded apical, Type (4A).
Original description: deVerteuil and Norris, 1996, p. 111: Cousteaudinium aubryae
Cysts comprising endoblast and periblast that are typically in contact only at the margins of the apical archeopyle. Endoblast subspherical to spherical formed from homogeneous, laevigate pedium only, ca. 0.25 to 0.75Ám thick; periblast subspherical and variably chorate, sagging between processes, formed from continuous tegillum, shagreenate to microstriate, usually perforate, and ca. 0.25Ám thick or less. Pericoel generally continuous below the archeopyle but in a few specimens the tegillum is closely appressed at the limbi. The tegillum forms hollow, tubular, open or distally perforate, intratabular processes, that in width and shape approximate the geometry of the tabulation elements, and whose length is inversely proportional to the degree of separation of the blasts. Maximum blast separation or process length is fairly constant among specimens, being ca. 60% of endoblast length at the antapex and 40% to 50% of this dimension elsewhere. Processes are distally slightly flared and irregularly denticulate. In specimens exhibiting maximum separation of the blasts, this denticulation, associated with clusters of perforations in the tegillum, may be the only indication of tabulation other than the archeopyle. The density of tegillum perforations is highly variable, from rare to pervasive, and the elliptical to circular claustra are from 0.5Ám to 6.0Ám in maximum diameter. Claustra may be crudely ordered with their long axes directed radially towards processes.
The tabulation as indicated by the processes is gonyaulacalean, sexiform L-type, 4', 6", xc, xs, p, 5-6"', 1"", with dextral torsion of the hypotabulation; the fourth and fifth postcingular processes on the dorsal surface are symmetrically located about the sulcal plane. The first postcingular process is vestigial or absent and the second is small (pl. 2, fig. 6); the posterior sulcal process is absent or included in the large antapical process that extends considerably up the ventral hyposome, while the posterior intercalary appendage may be small but present (pl. 1, fig. 3), weakly expressed (pl. 2, fig. 6), or absent. The anterior sulcal process is proximally rounded-stenoplanate, but then separates into two conical tapered shafts; the sulcal area defined between 6", 1', 6"' and 2"' is straight. There are no cingular processes. The archeopyle margin is rounded with a low, geniculate ventral protuberance formed by the anterior sulcal field and indicating a narrow contact between it and the fourth apical sensu lato (as/!4'), instead of the 6"/1 ' contact characteristic of most L-type tabulations. The sixth precingular process is relatively small for the series and is proximally rounded-steno~lanate. Anoth~r lower, geniculate protuberance on the archeopyle margin is sometimes present between the second and third apical fields sensu lato, and is produced by the anterior margin of the camerate third precingular field (pl. 1, fig. 7).
Dimensions: Although in most specimens the endoblast is more .subspherical than spherical, many occur obliquely compressed and are difficult to measure. In those cases we measured only the maximum endoblast diameter. Similarly, since process length varies inversely with the degree of cavation, in many specimens the maximum periblast diameter is a more useful parameter than process length. Twenty-two specimens were measured in total.
Maximum endoblast diameter 40(49.6)62Ám; endoblast length based on nine specimens 40(47.5)58Ám, holotype 49Ám; endoblast width based on ten specimens 38(47.9)60Ám, holotype 38Ám; maximum periblast diameter based on eight specimens 79(92.4)110Ám; length of processes 1-35Ám, holotype 6-32Ám.
Discussion: Cousteaudinium aubryae is morphologically variable with regard to the degree of separation between the endoblast and periblast, which ranges from fully inflated with no process shafts to closely appressed at the limbi. The majority of specimens we observed (several hundreds of them), are circumcavate. In most of these the degree of blast separation is between about 30% to 80% of the potential maximum. Specimens with the telligum closely appressed at the limbi are rare (pl. 2, figs. 4-6). The second most variable character in the material we studied is the density of claustra in the periblast, which varies from almost none to pervasive (pl. 2, figs. 2, 7). While most specimens show a noticable degree of perforation, few are heavily perforated. Most specimens have few sizable claustra away from the process extremities; heavily perforated specimens are typically highly inflated.
Further, specimens with tegillum and pedium closely appressed occur more commonly in, and may be restricted to, the lower part of the stratigraphic range of Cousteaudinium aubryae. In one sample at the very base of its range (Sample TML1705-4; Popes Creek Sand Member of the Calvert Formation; see Part I, this volume), early morphotypes of Cousteaudinium aubryae occur together with specimens of Hystrichokolpoma rigaudiae. The former all have closely appressed tegillum and pedium at the limbi, low or isolated cingular processes and a non-perforate periblast.
Other characters are notably stable within the morphology of Cousteaudinium aubryae. Chief among these is the absence of cingular processes which were not seen on any specimen despite careful searching. Sometimes a right accessory sulcal process or proximal cingular process may be present, but no others. Other stable characters include the rounded apical archeopyle and geniculate anterior margin of the anterior sulcal field, and the microstructure of the pedium and the tegillum.
Comparison: Cousteaudinium aubryae is most similar to Hystrichokolpoma rigaudiae. The tabulation and microstructure of the pedium and tegillum in the two species is almost exactly the same (pl. 18, figs. 1-3). Aside from the absence of cingular processes on Cousteaudinium aubryae, posterior sulcal processes have also not been observed. The latter are generally present on Hystrichokolpoma rigaudiae. In addition, the tegillum of Cousteaudinium aubryae, even in specimens where it is closely appressed at the limbi, always lacks the penitabular ridges that proximally surround the processes of Hystrichokolpoma rigaudiae (pl. 18, fig. 1). Nevertheless, the close similarity in tabulation and process structure is remarkable, particularly the sixth precingular and anterior sulcal fields, and testifies to a close evolutionary relationship of the two species. All other cavate Neogene taxa, including species of Amiculosphaera, Invertocysta, Saturnodinium and Thalassiphora, are quite distinct from Cousteaudinium aubryae, most obviously in having a precingular archeopyle. Saturnodinium pansum, which has a reported precingular archeopyle, is superf1cially similar to inflated specimens of C. aubryae but is much smaller and has marginal denticulations only in a single plane. In the Pentadinium laticinctum complex, processes are gonal rather than intratabular.
Occurrence: Lower through lower middle Miocene (DN2 - DN4) in the Salisbury Embayment. Specimens in the Calvert Formation are rare in the Popes Creek Sand Member south of Popes Creek (DN2) but quite common in the overlying Fairhaven Member in the same section (DN3). Cousteaudinium aubryae is persistently present in the Fairhaven Member and lower Plum Point Marls Member (DN3) in the Calvert Cliffs. It becomes increasingly rare in the overlying sequence of the Plum Point Marls Member (DN4), referred to Shattuck-beds 10 and l l (Part I, this volume).
Remarks: Reported occurrences of Cousteaudinium aubryae are reviewed by de Verteuil and Norris (Part I, this volume). In the Salisbury Embayment the lowest occurrence of Cousteaudinium aubryae is in the lower Miocene Popes Creek Sand Member (Zone DN2), and its highest occurrence is in the lower middle Miocene of the Plum Point Marls Member (Zone DN4), of the Calvert Formation. Specimens from the lower Miocene of the Labrador Sea illustrated by Manum et al. (1989), as Dinocyst sp. 4 and Dinocyst sp. 5, may be conspecific with Cousteaudinium aubryae although this cannot be demonstrated from the available information.
Holotype: de Verteuil and Norris, 1996a, pl.1, figs.1-3,6,9.
Locus typicus: Popes Creek Section, Potomac River, Popes Creek, Charles County, Maryland.
Stratum typicum: Lower Miocene Fairhaven Member of the Calvert Formation
Erikania cf. dynamica Morgenroth 1966, Benedek 1972:37, pl. 8, fig.10.
Thalassiphora?sp. 1 Powell 1988, pl.4,figs.15,16,19,20.-Head et al. 1989c: 496, pl. 6, figs. 7-10
Dinocyst sp. 6 Manum et al. 1989, pl. 8, figs. 8, 9
Thalassiphora gonoperforata nom. nud. Rusbult ans Strauss 1992:158, pl. 8, figs. 9-10.- Lund et al. 1993:29, pl. 1, fig. 13
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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.
Cousteaudinium aubryae de Verteuil and Norris, 1996. According to de Verteuil and Norris (1996), this is an intermediate to large cribroperidinioidean cyst, circumcavate and variably chorate, rarely skolochorate without limbate cavation. Tabulation delimited by broad based, box-like intratabular processes, one per field, excepting the cingular series and some ventral hyposomal fields, which lack processes. Endoblast smooth, periblast shagreenate to microstriate and variably perforate; both thin. Processes distally denticulate. Archeopyle rounded, apical. Size: maximum endoblast diameter 40-62 µm, length 40-58 µm, width 38-60 µm. Maximum periblast diameter 79-110 µm, length of processes 1-35 µm.
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Original diagnosis: deVerteuil and Norris, 1996, p. 111: Cousteaudinium aubryae
Intermediate to large cribroperidinioidean cysts, circumcavate and variably chorate; rarely skolochorate without limbate cavation. Tabulation delimited by broad based, box-like intratabular processes, one per field, excepting the cingular series and some ventral hyposomal fields, which lack processes. Endoblast smooth, periblast shagreenate to microstriate and variably perforate; both thin. Processes distally denticulate; archeopyle rounded apical, Type (4A).
Original description: deVerteuil and Norris, 1996, p. 111: Cousteaudinium aubryae
Cysts comprising endoblast and periblast that are typically in contact only at the margins of the apical archeopyle. Endoblast subspherical to spherical formed from homogeneous, laevigate pedium only, ca. 0.25 to 0.75Ám thick; periblast subspherical and variably chorate, sagging between processes, formed from continuous tegillum, shagreenate to microstriate, usually perforate, and ca. 0.25Ám thick or less. Pericoel generally continuous below the archeopyle but in a few specimens the tegillum is closely appressed at the limbi. The tegillum forms hollow, tubular, open or distally perforate, intratabular processes, that in width and shape approximate the geometry of the tabulation elements, and whose length is inversely proportional to the degree of separation of the blasts. Maximum blast separation or process length is fairly constant among specimens, being ca. 60% of endoblast length at the antapex and 40% to 50% of this dimension elsewhere. Processes are distally slightly flared and irregularly denticulate. In specimens exhibiting maximum separation of the blasts, this denticulation, associated with clusters of perforations in the tegillum, may be the only indication of tabulation other than the archeopyle. The density of tegillum perforations is highly variable, from rare to pervasive, and the elliptical to circular claustra are from 0.5Ám to 6.0Ám in maximum diameter. Claustra may be crudely ordered with their long axes directed radially towards processes.
The tabulation as indicated by the processes is gonyaulacalean, sexiform L-type, 4', 6", xc, xs, p, 5-6"', 1"", with dextral torsion of the hypotabulation; the fourth and fifth postcingular processes on the dorsal surface are symmetrically located about the sulcal plane. The first postcingular process is vestigial or absent and the second is small (pl. 2, fig. 6); the posterior sulcal process is absent or included in the large antapical process that extends considerably up the ventral hyposome, while the posterior intercalary appendage may be small but present (pl. 1, fig. 3), weakly expressed (pl. 2, fig. 6), or absent. The anterior sulcal process is proximally rounded-stenoplanate, but then separates into two conical tapered shafts; the sulcal area defined between 6", 1', 6"' and 2"' is straight. There are no cingular processes. The archeopyle margin is rounded with a low, geniculate ventral protuberance formed by the anterior sulcal field and indicating a narrow contact between it and the fourth apical sensu lato (as/!4'), instead of the 6"/1 ' contact characteristic of most L-type tabulations. The sixth precingular process is relatively small for the series and is proximally rounded-steno~lanate. Anoth~r lower, geniculate protuberance on the archeopyle margin is sometimes present between the second and third apical fields sensu lato, and is produced by the anterior margin of the camerate third precingular field (pl. 1, fig. 7).
Dimensions: Although in most specimens the endoblast is more .subspherical than spherical, many occur obliquely compressed and are difficult to measure. In those cases we measured only the maximum endoblast diameter. Similarly, since process length varies inversely with the degree of cavation, in many specimens the maximum periblast diameter is a more useful parameter than process length. Twenty-two specimens were measured in total.
Maximum endoblast diameter 40(49.6)62Ám; endoblast length based on nine specimens 40(47.5)58Ám, holotype 49Ám; endoblast width based on ten specimens 38(47.9)60Ám, holotype 38Ám; maximum periblast diameter based on eight specimens 79(92.4)110Ám; length of processes 1-35Ám, holotype 6-32Ám.
Discussion: Cousteaudinium aubryae is morphologically variable with regard to the degree of separation between the endoblast and periblast, which ranges from fully inflated with no process shafts to closely appressed at the limbi. The majority of specimens we observed (several hundreds of them), are circumcavate. In most of these the degree of blast separation is between about 30% to 80% of the potential maximum. Specimens with the telligum closely appressed at the limbi are rare (pl. 2, figs. 4-6). The second most variable character in the material we studied is the density of claustra in the periblast, which varies from almost none to pervasive (pl. 2, figs. 2, 7). While most specimens show a noticable degree of perforation, few are heavily perforated. Most specimens have few sizable claustra away from the process extremities; heavily perforated specimens are typically highly inflated.
Further, specimens with tegillum and pedium closely appressed occur more commonly in, and may be restricted to, the lower part of the stratigraphic range of Cousteaudinium aubryae. In one sample at the very base of its range (Sample TML1705-4; Popes Creek Sand Member of the Calvert Formation; see Part I, this volume), early morphotypes of Cousteaudinium aubryae occur together with specimens of Hystrichokolpoma rigaudiae. The former all have closely appressed tegillum and pedium at the limbi, low or isolated cingular processes and a non-perforate periblast.
Other characters are notably stable within the morphology of Cousteaudinium aubryae. Chief among these is the absence of cingular processes which were not seen on any specimen despite careful searching. Sometimes a right accessory sulcal process or proximal cingular process may be present, but no others. Other stable characters include the rounded apical archeopyle and geniculate anterior margin of the anterior sulcal field, and the microstructure of the pedium and the tegillum.
Comparison: Cousteaudinium aubryae is most similar to Hystrichokolpoma rigaudiae. The tabulation and microstructure of the pedium and tegillum in the two species is almost exactly the same (pl. 18, figs. 1-3). Aside from the absence of cingular processes on Cousteaudinium aubryae, posterior sulcal processes have also not been observed. The latter are generally present on Hystrichokolpoma rigaudiae. In addition, the tegillum of Cousteaudinium aubryae, even in specimens where it is closely appressed at the limbi, always lacks the penitabular ridges that proximally surround the processes of Hystrichokolpoma rigaudiae (pl. 18, fig. 1). Nevertheless, the close similarity in tabulation and process structure is remarkable, particularly the sixth precingular and anterior sulcal fields, and testifies to a close evolutionary relationship of the two species. All other cavate Neogene taxa, including species of Amiculosphaera, Invertocysta, Saturnodinium and Thalassiphora, are quite distinct from Cousteaudinium aubryae, most obviously in having a precingular archeopyle. Saturnodinium pansum, which has a reported precingular archeopyle, is superf1cially similar to inflated specimens of C. aubryae but is much smaller and has marginal denticulations only in a single plane. In the Pentadinium laticinctum complex, processes are gonal rather than intratabular.
Occurrence: Lower through lower middle Miocene (DN2 - DN4) in the Salisbury Embayment. Specimens in the Calvert Formation are rare in the Popes Creek Sand Member south of Popes Creek (DN2) but quite common in the overlying Fairhaven Member in the same section (DN3). Cousteaudinium aubryae is persistently present in the Fairhaven Member and lower Plum Point Marls Member (DN3) in the Calvert Cliffs. It becomes increasingly rare in the overlying sequence of the Plum Point Marls Member (DN4), referred to Shattuck-beds 10 and l l (Part I, this volume).
Remarks: Reported occurrences of Cousteaudinium aubryae are reviewed by de Verteuil and Norris (Part I, this volume). In the Salisbury Embayment the lowest occurrence of Cousteaudinium aubryae is in the lower Miocene Popes Creek Sand Member (Zone DN2), and its highest occurrence is in the lower middle Miocene of the Plum Point Marls Member (Zone DN4), of the Calvert Formation. Specimens from the lower Miocene of the Labrador Sea illustrated by Manum et al. (1989), as Dinocyst sp. 4 and Dinocyst sp. 5, may be conspecific with Cousteaudinium aubryae although this cannot be demonstrated from the available information.