Back
Homotryblium additense
Homotyrblium additense Dybkjaer, 2004, p.52,55, pl.1, figs.1a-d,2a-b; pl.2, figs.1a-b,2a-b,3a-b,4a-d,5a-b.
Holotype: Dybkjaer, 2004, pl.1, figs.1a-d.
Age: latest Chattian-earliest Aquitanian
Original diagnosis:
Genus Homotryblium Davey and Williams in Davey et al. (1966).
H.? additense Dybkjær, sp. nov. Plate 1 and Plate 2.
Holotype: Addit Mark borehole, sample 155–156 m, slide no. 5, England Finder coordinates P29-2, Plate 1, 1a–d. MGUH no. 26862.
Paratype: Addit Mark borehole, sample 144–145 m, slide no. 6, England Finder coordinates H38. Plate 1, 2a,b. MGUH no. 26863.
Repository: Geological Museum of the University of Copenhagen, Denmark.
Type locality: Addit Mark borehole (UTM coordinates: 6208748 north, 537941 East), Jylland, Denmark (in the samples 156, 148 and 145 m).
Stratigraphic horizon: Vejle Fjord Formation, the Vejle Fjord Clay Member.
Occurrence: At present, H.? additense is only known from the borehole Addit Mark, in Jylland, Denmark, in a very narrow stratigraphic interval (the HST of sequence B) referred to the uppermost Chattian and/or lower Aquitanian (uppermost Oligocene and/or lowermost Miocene) based on dinocyst stratigraphy (Dybkjær, in press).
Etymology: The species name, additense means “coming from Addit” and refers to the village, Addit, in Jylland, Denmark.
Diagnosis:
H.? additense comprise skolochorate cysts with a epicystal archaeopyle. The body is spherical to subspherical. The processes are intratabular; the cingular processes are missing. The processes are polytubular, broadly cylindrical to tubiform and distally closed. The number of processes varies; processes are not always developed on the smaller paraplates.
Description:
Skolochorate cysts with an epicystal archaeopyle. The operculum presumably splits up totally into single plates, as pieces of connected plates have not been found. However, single plates confidently referable to H.? additense were not found either. Accessory archaeopyle sutures at the archaeopyle margin indicate the cingular paraplates. The body is spherical to subspherical, bearing intratabular processes. The hypocyst is represented by a hemispherical body while definite remnants of the epicyst have not been found. The number of processes on the hypocyst varies from 6 to 9. The larger processes are broadly cylindrical and may narrow a little distally (e.g. Plate 1, 1a–d (the holotype), 3‴–5‴, and Plate 2, 3a,b). The smaller processes are slender, cylindrical or slightly tubiform (e.g. Plate 1, 1a–d; the holotype), 2‴ and 6‴). The larger processes are polytubular, formed by fused tubules (two to nine tubules have been seen), the larger the process, the more tubules. Due to the polytubular structure, the processes show a flower-like pattern at the base, where they fuse with the central body. The processes are closed distally. The thin body wall consists of an endophragm and a periphragm, the latter giving rise to the processes. The wall is equal to or less than 1 μm thick. The surface is smooth or faintly micro-granulate. No wall-structure was observed. The tabulation of the epicyst is unknown. The hypocyst tabulation is indicated by the intratabular processes and by the presence of a sulcal tab. The cingular paraplates are not represented by processes, but the cingular plates, 1c–6c have been identified by the suture of the archaeopyle (Plate 1, 1a). The number of processes varies from 6 to 9. Due to their position on the hypocyst in relation to the sulcal tap they are identified as 6 (2‴–6‴, 1⁗), 7 (2‴–6‴, 1⁗, 1p), 8 (2‴–6‴, 1⁗, 1p, ps) to 9 (1‴–6‴, 1⁗, 1p, ps). The post-cingular processes 3‴, 4‴ and 5‴ are the largest, while 1‴, 2‴, 6‴ and the antapical 1⁗, 1p and ps processes are smaller, if present at all. Eight processes are present on the holotype.
Dimensions:
Holotype: Cyst body diameter: 38–52 μm (slightly compressed); length of processes: 3‴–5‴: 22 μm, 2‴ and 6‴: 18 μm; width of processes: 3‴–5‴: 20–23 μm, 2‴ and 6‴: 16–18 μm at base, narrowing to 10 μm at the middle, widening again to 12 μm distally.
Paratype: Cyst body diameter: 43 μm; length of processes: 3‴–5‴: 21 μm, 2‴ and 6‴: 18–20 μm, ps: 18 μm; width of processes: 3‴–5‴: 12–18 μm, 2‴ and 6‴: 10–12 μm, ps: 10 μm.
Size range: Cyst body diameter: 36 (40) 44 μm; length of processes: 3‴–5‴: 11 (17) 22 μm, 2‴ and 6‴: 12 (17) 22 μm, antapical and parasulcal processes: 12 (17) 20 μm; width of processes: 3‴–5‴: 10 (16) 22 μm, 2‴ and 6‴: 6 (10) 14 μm, antapical and parasulcal processes: 3 (10) 13 μm; (12 specimens).
Discussion:
It has been chosen questionably to refer H.? additense to the genus Homotryblium although the cysts referred to H.? additense lack cingular processes and have processes which are closed distally. The presence of cingular, distally open processes was part of the original diagnosis for the genus Homotryblium. However, the cysts of H.? additense otherwise compare closely with the diagnosis of Homotryblium, having an epicystal archaeopyle, intratabular, polytubular processes, and a tabulation that corresponds to that of Homotryblium. The combination of absent cingular processes and the presence of polytubular processes have not been described from any other genus with an epicystal archaeopyle.
Homotryblium? additense has some characteristics similar to the genus Lithosphaeridium. These chorate cysts lack cingular processes, they have three apical processes, while the sulcal processes may be either absent or few. However, Lithosphaeridium has an apical archaeopyle in contrast to the epicystal archaeopyle of H.? additense and the processes are not polytubular.
The informal species Hystrichokolpoma pseudooceanica and H. reducta proposed by Zevenboom and Santarelli in Zevenboom (1995) both have hollow, tubular processes and lack paracingular processes. However, they can be distinguished from the genus Homotryblium by possessing an apical archaeopyle.
The processes of H.? additense resemble the processes of Homotryblium plectilum, Homotryblium floripes and Homotryblium vallum in being polytubular, intratabular and vary in size, according to their location on the cyst. However, the processes of H.? additense differ in being closed distally and in being cylindrical (e.g. Plate 2, 1a,b) or narrow a little distally (e.g. Plate 2, 3a,b). The processes of H. plectilum, H. floripes and H. vallum are buccinate or tubiform or split up into separate tubules or few, fused tubules (e.g. Plate 1, 3a,b and 5a,b). The processes of Homotryblium tenuispinosum are not polytubular, they have a buccinate or tubiform shape and seccate process-tips (e.g. Plate 1, 4a,b).
Homotryblium plectilum Drugg and Loeblich (1967)(Plate 1, 3a,b).
According to Bujak et al. (1980, p. 64), H. floripes (Deflandre and Cookson, 1955)Stover (1975) is a taxonomic senior synonym to Homotryblium plectilum. However, Stover in Lentin and Williams (1985, p. 168) retained H. plectilum: “Stover (personal communication) has studied the holotype of Homotryblium floripes and believes H. plectilum is a distinct and separate species”.
According to Williams et al. (1993, p. 30), “the southern hemisphere form (Homotryblium floripes), in contrast to the typically northern hemisphere Homotryblium plectilum, has a distinctly granular body in which the periphragm is about twice as thick as the endophragm. To the best of our knowledge, H. floripes is a strictly southern hemisphere species.” With this knowledge, it has been chosen to use H. plectilum in the present study.
Homotryblium tenuispinosum Davey and Williams (1966)(Plate 1, 4a,b).
Taxonomic junior synonym: Homotryblium pallidum according to Edwards (1996, p. 989).
Homotryblium vallum Stover (1977)(Plate 1, 5a,b).
Holotype: Dybkjaer, 2004, pl.1, figs.1a-d.
Age: latest Chattian-earliest Aquitanian
Original diagnosis:
Genus Homotryblium Davey and Williams in Davey et al. (1966).
H.? additense Dybkjær, sp. nov. Plate 1 and Plate 2.
Holotype: Addit Mark borehole, sample 155–156 m, slide no. 5, England Finder coordinates P29-2, Plate 1, 1a–d. MGUH no. 26862.
Paratype: Addit Mark borehole, sample 144–145 m, slide no. 6, England Finder coordinates H38. Plate 1, 2a,b. MGUH no. 26863.
Repository: Geological Museum of the University of Copenhagen, Denmark.
Type locality: Addit Mark borehole (UTM coordinates: 6208748 north, 537941 East), Jylland, Denmark (in the samples 156, 148 and 145 m).
Stratigraphic horizon: Vejle Fjord Formation, the Vejle Fjord Clay Member.
Occurrence: At present, H.? additense is only known from the borehole Addit Mark, in Jylland, Denmark, in a very narrow stratigraphic interval (the HST of sequence B) referred to the uppermost Chattian and/or lower Aquitanian (uppermost Oligocene and/or lowermost Miocene) based on dinocyst stratigraphy (Dybkjær, in press).
Etymology: The species name, additense means “coming from Addit” and refers to the village, Addit, in Jylland, Denmark.
Diagnosis:
H.? additense comprise skolochorate cysts with a epicystal archaeopyle. The body is spherical to subspherical. The processes are intratabular; the cingular processes are missing. The processes are polytubular, broadly cylindrical to tubiform and distally closed. The number of processes varies; processes are not always developed on the smaller paraplates.
Description:
Skolochorate cysts with an epicystal archaeopyle. The operculum presumably splits up totally into single plates, as pieces of connected plates have not been found. However, single plates confidently referable to H.? additense were not found either. Accessory archaeopyle sutures at the archaeopyle margin indicate the cingular paraplates. The body is spherical to subspherical, bearing intratabular processes. The hypocyst is represented by a hemispherical body while definite remnants of the epicyst have not been found. The number of processes on the hypocyst varies from 6 to 9. The larger processes are broadly cylindrical and may narrow a little distally (e.g. Plate 1, 1a–d (the holotype), 3‴–5‴, and Plate 2, 3a,b). The smaller processes are slender, cylindrical or slightly tubiform (e.g. Plate 1, 1a–d; the holotype), 2‴ and 6‴). The larger processes are polytubular, formed by fused tubules (two to nine tubules have been seen), the larger the process, the more tubules. Due to the polytubular structure, the processes show a flower-like pattern at the base, where they fuse with the central body. The processes are closed distally. The thin body wall consists of an endophragm and a periphragm, the latter giving rise to the processes. The wall is equal to or less than 1 μm thick. The surface is smooth or faintly micro-granulate. No wall-structure was observed. The tabulation of the epicyst is unknown. The hypocyst tabulation is indicated by the intratabular processes and by the presence of a sulcal tab. The cingular paraplates are not represented by processes, but the cingular plates, 1c–6c have been identified by the suture of the archaeopyle (Plate 1, 1a). The number of processes varies from 6 to 9. Due to their position on the hypocyst in relation to the sulcal tap they are identified as 6 (2‴–6‴, 1⁗), 7 (2‴–6‴, 1⁗, 1p), 8 (2‴–6‴, 1⁗, 1p, ps) to 9 (1‴–6‴, 1⁗, 1p, ps). The post-cingular processes 3‴, 4‴ and 5‴ are the largest, while 1‴, 2‴, 6‴ and the antapical 1⁗, 1p and ps processes are smaller, if present at all. Eight processes are present on the holotype.
Dimensions:
Holotype: Cyst body diameter: 38–52 μm (slightly compressed); length of processes: 3‴–5‴: 22 μm, 2‴ and 6‴: 18 μm; width of processes: 3‴–5‴: 20–23 μm, 2‴ and 6‴: 16–18 μm at base, narrowing to 10 μm at the middle, widening again to 12 μm distally.
Paratype: Cyst body diameter: 43 μm; length of processes: 3‴–5‴: 21 μm, 2‴ and 6‴: 18–20 μm, ps: 18 μm; width of processes: 3‴–5‴: 12–18 μm, 2‴ and 6‴: 10–12 μm, ps: 10 μm.
Size range: Cyst body diameter: 36 (40) 44 μm; length of processes: 3‴–5‴: 11 (17) 22 μm, 2‴ and 6‴: 12 (17) 22 μm, antapical and parasulcal processes: 12 (17) 20 μm; width of processes: 3‴–5‴: 10 (16) 22 μm, 2‴ and 6‴: 6 (10) 14 μm, antapical and parasulcal processes: 3 (10) 13 μm; (12 specimens).
Discussion:
It has been chosen questionably to refer H.? additense to the genus Homotryblium although the cysts referred to H.? additense lack cingular processes and have processes which are closed distally. The presence of cingular, distally open processes was part of the original diagnosis for the genus Homotryblium. However, the cysts of H.? additense otherwise compare closely with the diagnosis of Homotryblium, having an epicystal archaeopyle, intratabular, polytubular processes, and a tabulation that corresponds to that of Homotryblium. The combination of absent cingular processes and the presence of polytubular processes have not been described from any other genus with an epicystal archaeopyle.
Homotryblium? additense has some characteristics similar to the genus Lithosphaeridium. These chorate cysts lack cingular processes, they have three apical processes, while the sulcal processes may be either absent or few. However, Lithosphaeridium has an apical archaeopyle in contrast to the epicystal archaeopyle of H.? additense and the processes are not polytubular.
The informal species Hystrichokolpoma pseudooceanica and H. reducta proposed by Zevenboom and Santarelli in Zevenboom (1995) both have hollow, tubular processes and lack paracingular processes. However, they can be distinguished from the genus Homotryblium by possessing an apical archaeopyle.
The processes of H.? additense resemble the processes of Homotryblium plectilum, Homotryblium floripes and Homotryblium vallum in being polytubular, intratabular and vary in size, according to their location on the cyst. However, the processes of H.? additense differ in being closed distally and in being cylindrical (e.g. Plate 2, 1a,b) or narrow a little distally (e.g. Plate 2, 3a,b). The processes of H. plectilum, H. floripes and H. vallum are buccinate or tubiform or split up into separate tubules or few, fused tubules (e.g. Plate 1, 3a,b and 5a,b). The processes of Homotryblium tenuispinosum are not polytubular, they have a buccinate or tubiform shape and seccate process-tips (e.g. Plate 1, 4a,b).
Homotryblium plectilum Drugg and Loeblich (1967)(Plate 1, 3a,b).
According to Bujak et al. (1980, p. 64), H. floripes (Deflandre and Cookson, 1955)Stover (1975) is a taxonomic senior synonym to Homotryblium plectilum. However, Stover in Lentin and Williams (1985, p. 168) retained H. plectilum: “Stover (personal communication) has studied the holotype of Homotryblium floripes and believes H. plectilum is a distinct and separate species”.
According to Williams et al. (1993, p. 30), “the southern hemisphere form (Homotryblium floripes), in contrast to the typically northern hemisphere Homotryblium plectilum, has a distinctly granular body in which the periphragm is about twice as thick as the endophragm. To the best of our knowledge, H. floripes is a strictly southern hemisphere species.” With this knowledge, it has been chosen to use H. plectilum in the present study.
Homotryblium tenuispinosum Davey and Williams (1966)(Plate 1, 4a,b).
Taxonomic junior synonym: Homotryblium pallidum according to Edwards (1996, p. 989).
Homotryblium vallum Stover (1977)(Plate 1, 5a,b).