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Cannosphaeropsis passio
Cannosphaeropsis passio, de Verteuil and Norris, 1996
Holotype: de Verteuil and Norris, 1996, Plate 7, figs. 1-3, 5, 6, 8
Locus typicus: Richmond City Jail Section, , Henrico County, Virginia
Occurrence: Upper middle Miocene (DN7) in the Salisbury Embayment, restricted in the Calvert Cliffs to beds of the Boston Cliffs and Conoy members of the Choptank Formation (Part 1, this volume).
Stratum typicum: Middle Miocene
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Original description: [de Verteuil and Norris, 1996, p. 132]:
Diagnosis:
Intermediate to large species of Cannosphaeropsis with spherical, smooth endoblast and trabeculate ectoblast, connected by cingular trabeculate appendages only; endoblast with low apical boss; ectoblast delimits tabulation and has gonal trifurcations rotationally offset with respect to triple junction boundaries; cyst further characterized by pervasively alveolate endoblast and trabeculae.
Description:
The spherical endoblast has an apically positioned hemispherical boss, ca. 3 µm across and 2 µm high, and is otherwise featureless except for the simple precingular archeopyle. The wall is 0.5 to 1.0 µm thick and comprises homogeneous pedium ca.0.25 µm thick, an alveolate stratum ca. 0.5 µm thick and homogeneous tegillum ca. 0.25 µm thick. The alveoles in the wall are evenly distributed, <0.2 to ca. 0.4 µm in diameter and separated by fine muri ca. 0.2 µm wide; in TLM the wall may appear micropunctate but in optical section (pl. 7, fig. 6) and under SEM (pl. 17, figs. 1, 3) the tegillum surface is seen to be laevigate. Solid, alveolate appendages, ca. 1.0 µm in diameter, cylindrical and flexuous, are present at or near the proximal and distal ends of the cingulum and at some cingular field contacts as expressed on the ectoblast; sometimes two or more trabeculate appendages, extending to the endoblast, are associated with one cingular triple junction of the ectoblast. These appendages provide the only contact between the endoblast and the trabeculate ectoblast; they appear to be consistently absent from the 3c/4c field boundary.
The ectoblast is only slightly longer than it is wide and is formed from similarly alveolate trabeculae, ca. 1.0 µm in diameter, that delimit the tabulation; single trabeculae each indicate a field boundary and typically meet at triple junctions. Each gonal field position on the ectoblast has associated with it a trifurcation rotationally offset approximately 60¦ from itself. Often the trifurcation is centered at the triple junction but sometimes two arms, still at 120¦ to each other, are located slightly off and directed away from it, while the third arm bisects the involved angle of the field opposite (pl. 7, fig. 1; pl. 8, fig. 4). A shallow pit ca. 1.0 µm across and 0.5 µm deep is usually present at the centre of trifurcations. The length of furcations is approximately proportional to the sizes of the fields involved in the contact and varies from ca. 1.5 µm spines near the apical pore field to 12.0 µm furcations with bifid terminations at adcingular series junctions. Orthogonally directed intergonal bifurcations are not present on the trabeculae.
Observation of the tabulation is usually difficult because the ectoblast is collapsed on most specimens. Based on analysis of the holotype and a small number of other specimens, the tabulation is gonyaulacalean S-type sexiform (text-fig. 33) but the sulcal area appears relatively straight and 6" is sometimes more rectangular than right-angled triangular. The apical series is distinctive, with four sensu lato apical fields plus P and Q (pl. 8, fig.1). The first and fourth apicals (1' and !4') are stenoplanate and essentially symmetrical about mid-ventral 1'1!4', which is the longest side of both fields (pl. 8, fig. 1). Camerate 2' and !3' are also bilaterally symmetrical about their common boundary, mid-dorsally located 2'/!3', and are larger than 1' and !4' (pl. 8, fig.1). The P and Q fields lie at the intersection of the four apical fields sensu lato. Dorsally directed, isosceles triangular P contacts 1', 2' and Q; longer, calene Q contacts all four apicals as well as P (pl. 8, fig. 1; Q/B arrangement of Helenes 1986). To accommodate this apical geometry, the anterior sulcal field is essentially isoplanate with an unusually wide as/l' boundary; neither the 6"/1' nor the as/!4' field boundary is appreciably developed and the four fields meet at a single orthogonal junction (pl. 8, fig. 1). The sixth precingular field is planate to trapezoidal with side 3 only slightly longer than side 1 (text-fig. 33). The sulcal fields occupy a long, wide and straight mid-ventral region, extending most of the length of the ectoblast. From bottom to top, posterior sulcal, right and left sulcals, a central un-named field and an anterior sulcal field are present (pl. 8, fig. 4). The posterior sulcal field is large, symmetric-isocamerate, with rectilinear posterior margin (side 1) and geniculate anterior margin (sides 3 and 4), and with l^2 and 1^5 ca. 95¦; rs and ls are latifastigate or laticamerate, and smaller than ps. The mid-sulcal area may be divided in some specimens but is otherwise approximately planate. The endoarcheopyle is simple precingular formed by loss of deltacamerate 3"; archeopyle angles are sharp (not rounded) and 1^5 is ca. 150¦. The 2'/!3' and 3c/4c field boundaries are aligned mid-dorsally and bisect 3" and 4"' (neutral torsion).
Dimensions:
Maximum endoblast diameter 35(43.8)52 µm; holotype 47 µm. Maximum ectoblast diameter, based on measurements of collapsed specimens, ranges from ca. 75 to 125 µm; holotype length ca. 120 µm, holotype width at cingulum ca. 100 µm. Twenty-one specimens measured.
Affinities:
The new species is most similar to Cannosphaeropsis utinensis 1932; both species are about the same size and have smooth endoblast and solid trabeculate ectoblasts with gonal trifurcations. Comparison of our material with published descriptions and illustrations of Cannosphaeropsis utinensis indicate several important differences: 1. The wall and trabeculae of Cannosphaeropsis utinensis are not alveolate; this is a consistent and diagnostic character of Cannosphaeropsis passio. 2. In Cannosphaeropsis utinensis the trabeculate network is connected to the endoblast by a robust process complex at the top of the sulcus (near as/l') and sometimes also by posterior gonal processes at 4"'; in Cannosphaeropsis passio the only connections between endoblast and ectoblast are equatorial and these are always thin.3. Extra-corial appendages supporting trifurcations are not present in Cannosphaeropsis passio, or else are very low, and intergonal bifurcations do not occur; both these features are characteristic of Cannosphaeropsis utinensis.
Cannosphaeropsis passio is less similar to all other species with circumcavate trabeculate ectoblasts because of the distinctive form of the gonal trifurcations and its thin, solid, alveolate trabeculae.
Remarks:
The specimen illustrated by Brown and Downie (1985) as Cannosphaeropsis utinensis, from upper Miocene (NNI I) of DSDP Hole 548A on the Goban Spur, appears to be con-specific with Cannosphaeropsis passio. However, a single unillustrated record from the lower Eocene of the same site is considered provisional pending further information. Ioakim (1979) illustrated a specimen of Cannosphaeropsis passio, as Cannosphaeropsis utinensis, from a lower Miocene cuttings sample from the North Sea. Her range chart shows records of Cannosphaeropsis utinensis in transitional upper Oligocene -lower Miocene and lower Eocene cuttings samples from the North Sea and from one lower Eocene core sample. The Oligocene-lower Miocene records are likely based on caved specimens of Canno.sphaeropsis passio but the lower Eocene records may not be con-specific. The lower and middle Miocene records of Cannosphaeropsis utinensis from ODP Site 643 in the Norwegian Sea (Manum et al. 1989) are difficult to evaluate without more information; the illustrated specimens are not readily identifiable as either Canno.sphaeropsis utinensis or Cannosphaeropsis passio and may belong to an undescribed species de Verteuil has recorded from the lower Miocene offshore New Jersey (Hole 904A, Core 30; Zone DN2, unpub.). Engel (1992) recorded and illustrated Cannosphaeropsis passio, as Cannosphaeropsis utinensis sp. I, from a single middle Miocene core catcher sample from DSDP Hole 400A in the Bay of Biscay. Engel (1992) recorded Canno.sphaeropsis utinensis without illustration from possibly lower upper Miocene core (N16?) from DSDP Site 408 southwest of Iceland; this record is probably based on specimens of Cannosphaeropsis passio. In our experience Cannosphaeropsis passio has a very narrow stratigraphic range in the western north Atlantic, within the upper part of the middle Miocene, and is an important index fossil for the middle/upper Miocene glacial lowstand.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Cannosphaeropsis passio de Verteuil and Norris, 1996. According to de Verteuil and Norris (1996), this species has a spherical, smooth endoblast and trabeculate ectoblast, connected by cingular trabeculate appendages only; endoblast with low apical boss; ectoblast delimits tabulation and has gonal trifurcations rotationally offset with respect to triple junctions. The cyst is further characterised by pervasively alveolate endoblast and trabeculae. Appendages appear to be absent from 3c/4c boundary The species differs from Cannosphaeropsis utinensis in: having an alveolate wall, the presence of cingular processes rather than a robust complex at the top of the sulcus and also sometimes also by posterior gonal processes at 4"’, no extra-corial appendages supporting trifurcations, and no intergonal bifurcations.
Size: maximum endoblast diameter 35-52 µm, maximum ectoblast diameter 75-125 µm.
Holotype: de Verteuil and Norris, 1996, Plate 7, figs. 1-3, 5, 6, 8
Locus typicus: Richmond City Jail Section, , Henrico County, Virginia
Occurrence: Upper middle Miocene (DN7) in the Salisbury Embayment, restricted in the Calvert Cliffs to beds of the Boston Cliffs and Conoy members of the Choptank Formation (Part 1, this volume).
Stratum typicum: Middle Miocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [de Verteuil and Norris, 1996, p. 132]:
Diagnosis:
Intermediate to large species of Cannosphaeropsis with spherical, smooth endoblast and trabeculate ectoblast, connected by cingular trabeculate appendages only; endoblast with low apical boss; ectoblast delimits tabulation and has gonal trifurcations rotationally offset with respect to triple junction boundaries; cyst further characterized by pervasively alveolate endoblast and trabeculae.
Description:
The spherical endoblast has an apically positioned hemispherical boss, ca. 3 µm across and 2 µm high, and is otherwise featureless except for the simple precingular archeopyle. The wall is 0.5 to 1.0 µm thick and comprises homogeneous pedium ca.0.25 µm thick, an alveolate stratum ca. 0.5 µm thick and homogeneous tegillum ca. 0.25 µm thick. The alveoles in the wall are evenly distributed, <0.2 to ca. 0.4 µm in diameter and separated by fine muri ca. 0.2 µm wide; in TLM the wall may appear micropunctate but in optical section (pl. 7, fig. 6) and under SEM (pl. 17, figs. 1, 3) the tegillum surface is seen to be laevigate. Solid, alveolate appendages, ca. 1.0 µm in diameter, cylindrical and flexuous, are present at or near the proximal and distal ends of the cingulum and at some cingular field contacts as expressed on the ectoblast; sometimes two or more trabeculate appendages, extending to the endoblast, are associated with one cingular triple junction of the ectoblast. These appendages provide the only contact between the endoblast and the trabeculate ectoblast; they appear to be consistently absent from the 3c/4c field boundary.
The ectoblast is only slightly longer than it is wide and is formed from similarly alveolate trabeculae, ca. 1.0 µm in diameter, that delimit the tabulation; single trabeculae each indicate a field boundary and typically meet at triple junctions. Each gonal field position on the ectoblast has associated with it a trifurcation rotationally offset approximately 60¦ from itself. Often the trifurcation is centered at the triple junction but sometimes two arms, still at 120¦ to each other, are located slightly off and directed away from it, while the third arm bisects the involved angle of the field opposite (pl. 7, fig. 1; pl. 8, fig. 4). A shallow pit ca. 1.0 µm across and 0.5 µm deep is usually present at the centre of trifurcations. The length of furcations is approximately proportional to the sizes of the fields involved in the contact and varies from ca. 1.5 µm spines near the apical pore field to 12.0 µm furcations with bifid terminations at adcingular series junctions. Orthogonally directed intergonal bifurcations are not present on the trabeculae.
Observation of the tabulation is usually difficult because the ectoblast is collapsed on most specimens. Based on analysis of the holotype and a small number of other specimens, the tabulation is gonyaulacalean S-type sexiform (text-fig. 33) but the sulcal area appears relatively straight and 6" is sometimes more rectangular than right-angled triangular. The apical series is distinctive, with four sensu lato apical fields plus P and Q (pl. 8, fig.1). The first and fourth apicals (1' and !4') are stenoplanate and essentially symmetrical about mid-ventral 1'1!4', which is the longest side of both fields (pl. 8, fig. 1). Camerate 2' and !3' are also bilaterally symmetrical about their common boundary, mid-dorsally located 2'/!3', and are larger than 1' and !4' (pl. 8, fig.1). The P and Q fields lie at the intersection of the four apical fields sensu lato. Dorsally directed, isosceles triangular P contacts 1', 2' and Q; longer, calene Q contacts all four apicals as well as P (pl. 8, fig. 1; Q/B arrangement of Helenes 1986). To accommodate this apical geometry, the anterior sulcal field is essentially isoplanate with an unusually wide as/l' boundary; neither the 6"/1' nor the as/!4' field boundary is appreciably developed and the four fields meet at a single orthogonal junction (pl. 8, fig. 1). The sixth precingular field is planate to trapezoidal with side 3 only slightly longer than side 1 (text-fig. 33). The sulcal fields occupy a long, wide and straight mid-ventral region, extending most of the length of the ectoblast. From bottom to top, posterior sulcal, right and left sulcals, a central un-named field and an anterior sulcal field are present (pl. 8, fig. 4). The posterior sulcal field is large, symmetric-isocamerate, with rectilinear posterior margin (side 1) and geniculate anterior margin (sides 3 and 4), and with l^2 and 1^5 ca. 95¦; rs and ls are latifastigate or laticamerate, and smaller than ps. The mid-sulcal area may be divided in some specimens but is otherwise approximately planate. The endoarcheopyle is simple precingular formed by loss of deltacamerate 3"; archeopyle angles are sharp (not rounded) and 1^5 is ca. 150¦. The 2'/!3' and 3c/4c field boundaries are aligned mid-dorsally and bisect 3" and 4"' (neutral torsion).
Dimensions:
Maximum endoblast diameter 35(43.8)52 µm; holotype 47 µm. Maximum ectoblast diameter, based on measurements of collapsed specimens, ranges from ca. 75 to 125 µm; holotype length ca. 120 µm, holotype width at cingulum ca. 100 µm. Twenty-one specimens measured.
Affinities:
The new species is most similar to Cannosphaeropsis utinensis 1932; both species are about the same size and have smooth endoblast and solid trabeculate ectoblasts with gonal trifurcations. Comparison of our material with published descriptions and illustrations of Cannosphaeropsis utinensis indicate several important differences: 1. The wall and trabeculae of Cannosphaeropsis utinensis are not alveolate; this is a consistent and diagnostic character of Cannosphaeropsis passio. 2. In Cannosphaeropsis utinensis the trabeculate network is connected to the endoblast by a robust process complex at the top of the sulcus (near as/l') and sometimes also by posterior gonal processes at 4"'; in Cannosphaeropsis passio the only connections between endoblast and ectoblast are equatorial and these are always thin.3. Extra-corial appendages supporting trifurcations are not present in Cannosphaeropsis passio, or else are very low, and intergonal bifurcations do not occur; both these features are characteristic of Cannosphaeropsis utinensis.
Cannosphaeropsis passio is less similar to all other species with circumcavate trabeculate ectoblasts because of the distinctive form of the gonal trifurcations and its thin, solid, alveolate trabeculae.
Remarks:
The specimen illustrated by Brown and Downie (1985) as Cannosphaeropsis utinensis, from upper Miocene (NNI I) of DSDP Hole 548A on the Goban Spur, appears to be con-specific with Cannosphaeropsis passio. However, a single unillustrated record from the lower Eocene of the same site is considered provisional pending further information. Ioakim (1979) illustrated a specimen of Cannosphaeropsis passio, as Cannosphaeropsis utinensis, from a lower Miocene cuttings sample from the North Sea. Her range chart shows records of Cannosphaeropsis utinensis in transitional upper Oligocene -lower Miocene and lower Eocene cuttings samples from the North Sea and from one lower Eocene core sample. The Oligocene-lower Miocene records are likely based on caved specimens of Canno.sphaeropsis passio but the lower Eocene records may not be con-specific. The lower and middle Miocene records of Cannosphaeropsis utinensis from ODP Site 643 in the Norwegian Sea (Manum et al. 1989) are difficult to evaluate without more information; the illustrated specimens are not readily identifiable as either Canno.sphaeropsis utinensis or Cannosphaeropsis passio and may belong to an undescribed species de Verteuil has recorded from the lower Miocene offshore New Jersey (Hole 904A, Core 30; Zone DN2, unpub.). Engel (1992) recorded and illustrated Cannosphaeropsis passio, as Cannosphaeropsis utinensis sp. I, from a single middle Miocene core catcher sample from DSDP Hole 400A in the Bay of Biscay. Engel (1992) recorded Canno.sphaeropsis utinensis without illustration from possibly lower upper Miocene core (N16?) from DSDP Site 408 southwest of Iceland; this record is probably based on specimens of Cannosphaeropsis passio. In our experience Cannosphaeropsis passio has a very narrow stratigraphic range in the western north Atlantic, within the upper part of the middle Miocene, and is an important index fossil for the middle/upper Miocene glacial lowstand.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Cannosphaeropsis passio de Verteuil and Norris, 1996. According to de Verteuil and Norris (1996), this species has a spherical, smooth endoblast and trabeculate ectoblast, connected by cingular trabeculate appendages only; endoblast with low apical boss; ectoblast delimits tabulation and has gonal trifurcations rotationally offset with respect to triple junctions. The cyst is further characterised by pervasively alveolate endoblast and trabeculae. Appendages appear to be absent from 3c/4c boundary The species differs from Cannosphaeropsis utinensis in: having an alveolate wall, the presence of cingular processes rather than a robust complex at the top of the sulcus and also sometimes also by posterior gonal processes at 4"’, no extra-corial appendages supporting trifurcations, and no intergonal bifurcations.
Size: maximum endoblast diameter 35-52 µm, maximum ectoblast diameter 75-125 µm.