Back
Habibacysta tectata
Habibacysta tectata Head et al., 1989b, p.458, pl.4, figs.1–6,9–10.
Head (1996a, p.551) considered Filisphaera? minuta to be a possible taxonomic junior synonym of this species.
Holotype: Head et al., 1989b, pl.4, figs.1–2,5–6; Head, 1994a, pl.5, figs.1–6.
Locus typicus: ODP leg 105, site 646
Stratum typicum: Late Miocene-Early Pliocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Habibacysta tectata Head et al., 1989b. According to Head (1994a), has rods or granules that may be separate or adjacently fused. Ectophragm supported by the rods/granules is smooth and extremely thin and may be irregularly perforate or forms a delicate irregular reticulation, although it appears to be complete in some specimens. Size: diameter 29-45 µm. Ludham material: Size: cyst diameter 37-57 µm, wall thickness 0.8-1.4 µm.
--------------------------------------------------
Original diagnosis: Head et al., 1989, p.458
Cysts spherical, holocavate. Endophragm, thin and solid, bearing rods or granules (periphragm) that may be separate or adjacently fused. Ectophragm supported by the rods/granules is smooth and extremely thin and is commonly irregularly perforate or forms a delicate irregular reticulation, although it appears to be entire in some specimens. Archeopyle precingular formed by loss of paraplate 3". Operculum free. There is no other expression of paratabulation.
Dimensions. Holotype: cyst diameter, 33 Ám. Range in cyst diameter, 29(36)45 Ám. Total wall thickness, around 1 to 2 Ám. Fifteen specimens were measured.
Original description: Head et al., 1989, p.458
The ectophragm, especially in specimens where it is discontinuous, may only be detected under oil immersion by careful observation of optical sections of the cyst wall. Such observation suggests that the ectophragm may be entire in some specimens. Fine details of the ectophragm surface can only be observed with SEM.Plate 4, Figure 4 shows a discontinuous network of narrow irregular platforms (see also Wrenn and Kokinos 1986, Pl. 18, Fig. 6)." (Head et al. 1989b, p. 458).
--------------------------------------------------------------------------------------------------------------------------------------------------
Description: Head 1994, p. 300, 302
The following description is based on re-examination of the holotype by light microscopy. The cyst is uncompressed but slightly crumpled and spherical with an archeopyle (operculum missing) formed by loss of paraplate 3". The archeopyle margin is smooth and the angles appear rounded. There are no other indications of paratabulation. The pedium is thin (ca. 0.2Ám thick) and solid. The luxuria is both columellate and tegillate. Columellae are solid rods perpendicular to and arising from the pedium; most have circular cross sections ca. 0.3Ám in diameter. The distance between adjacent columellae varies from ca. 0.5Ám to ca. 1.5Ám, although occasional columellae are apparently fused. The tectum is discontinuous and extremely thin (thinner than pedium), hence visible only in optical section such as at periphery of the cyst. Total wall thickness ca. 1.1 Ám. These new details on the morphology of the holotype agree with the description and diagnosis of this species given in Head et al. (1989b, p. 458, see above). Specimens from Ludham Borehole and Chillesford Church pit closely resemble the type material. Cysts are spherical with characteristic tegillate wall. The pedium is very thin (0.3Ám or less), bearing slender, solid, perpendicular columellae of about 0.3Ám or less in diameter. Adjacent columellae are separated by about 0.5 to 1.5Ám, although their distribution is typically rather irregular with occasional fusion between adjacent columellae. The tegillum is visible under the light microscope only in optical section: the columellae, however, impart a distinctive pattern of small scattered dots in plan view. The archeopyle is formed by loss of the third precingular paraplate; the operculum is free. There are no accessory archeopyle sutures and the archeopyle has a relatively smooth outline with rounded angles. There are no other indications of paratabulation.
Dimensions: Holotype (uncompressed): Cyst length 33Ám, width 36Ám. Range in cyst diameter based on type material (from Head et al. 1989b), 29(36)45Ám. Ludham Borehole (sample IB 45-2): Cyst diameter maximum/ minimum averaged) 37(45.0)57Ám, wall thickness 0.9-1.7Ám. Thirty (compressed) specimens were measured. Chillesford Church (sample ChCh 5): Cyst diameter (maximum) 29(34.3)42Ám, wall thickness 0.8-1.4Ám. Twenty-one (uncompressed) specimens were measured.
Discussion: Head 1994, p. 302
SEM analysis of the Chillesford Church specimens reveals a perforated tegillum (see also Head et al. 1989b, pl. 4, fig. 4; and Wrenn and Kokinos 1986, pl. 18, fig. 6). The Ludham Borehole specimens were not examined under SEM but observations under the light microscope indicate no substantial differences with the Chillesford Church specimens. The larger average dimensions of the Ludham Borehole specimens may be an artifact resulting from their compressed preservation and possible swelling in the glycerine jelly mounting medium.
Comparison: Head 1994, p. 302, 304
Tectatodinium pellitum differs from Habibacysta tectata in having a spongy luxuria, compared with the columellate and tegillate luxuria in Habibacysta tectata. Furthermore, the archeopyle in Habibacysta tectata has rounded angles and a smooth margin, whereas in Tectatodinium pellitum it typically has well defined angles and irregular margin. Specimens identified as Tectatodinium pellitum by Mudie (1989, pl. 5, figs. 1, 5; and in Mudie et al. 1990, pl. 2, fig. 8) apparently represent a species of Habibacysta but details of the wall cannot be determined from the illustrations. Specimens identified as Tectatodinium pellitum by Harland (1988b, pl. 82; 1992, pl. 5.1, fig. 7) and Harland et al. (1991, fig. 4c) do not have the irregular archeopyle outline characteristic of Tectatodinium pellitum and are probably instead attributable to Habibacysta but details of the wall cannot be determined from the illustrations.
Tectatodinium sp. 1 of de Vernal and Mudie (1989a, pl. 1, figs. 9-11) is undoubtedly a species of Habibacysta but the wall is thicker than usual for H. tectata. De Vernal and Mudie's species is thus tentatively ascribed to Habibacysta tectata. Dinocyst sp.1 of Mudie (1989, pl. 5, figs. 4 and 8) resembles H. tectata but the presence of a lP archeopyle cannot be confirmed.
Bitectatodinium tepikiense differs from Habibacysta tectata in having a 2P archeopyle with well-defined angles, but when the archeopyle is not visible these two species are distinguishable by careful study of their wall structure--a sometimes necessary exercise because the species can occur in the same samples. In Bitectatodinium tepikiense the luxuria consists of a complex arrangement of lamellae that are perpendicular or subperpendicular to the pedium (see transmission electron micrographs in Jux 1976, pls. 2 and 3; SEM illustrations in Jux 1976, pl. 1, figs. 3a and 3b, Turon 1984, pl. 5, figs. 2, 3, and in Head and Wrenn 1992a, pl. 7 figs. 5-10 and see discussion therein). The bases of these lamellae are often thickened and subcircular in plan view, appearing under the light microscope as rounded granules or rods (see the description and illustrations of Caledonidium vermiculatum, a taxonomic junior synonym of B. tepikiense, in Reid 1974; and illustrations of the holotype of Bitectatodinium tepikiense in Wilson 1973). These thickened bases differ from the columellae in Habibacysta tectata by having larger diameters (about 0.5,um), a more dense distribution, and a greater tendency to be fused with adjacent bases. Careful analysis of the wall in optical section shows that a tegillum is not present in Bitectatodinium tepikiense unlike Habibacysta tectata.
Filisphaera filifera Bujak 1984 emend. Head 1994 differs from Habibacysta tectata in having a luxuria composed of radiating septa that form a distally open microreticulum (text-figure 3). Unlike Habibacysta tectata, the luxuria in Filisphaera filifera does not terminate distally as a tegillum.
cf. Habibacysta? sp. of Zevenboom in Head (1993 (ed.), p. 210, pl. 6, figs. 10-13), described from the middle Miocene of The Netherlands, differs from Habibacysta tectata in having a camerate 2P archeopyle with well defined angles, and a continuous tegillum (Head 1994).
Habibacysta tectata has a smooth surface in contrast to the low surface bumps that characterize Habibacysta? sp. (herein).
Occurrence in eastern England: Upper Pliocene Ludhamian (ca. 2.4 Ma) through Baventian (ca. 1.8 Ma) stages and possible lowermost Pleistocene of the Royal Society Borehole at Ludham, Norfolk, occurring in at least seven of the eight samples studied by Wall and Dale (1968a). Upper Pliocene Bramertonian Stage (ca. 2. 0 Ma) of the Chillesford Sand Member of the Norwich Crag Formation at Chillesford Church Pit, Chillesford, Suffolk.
Previous records: Head 1994, p. 304
Middle (lower middle?) Miocene through upper Pliocene or lower Pleistocene of ODP Site 645 in Baffin Bay (Head et al. 1989c; Anstey 1992) and possible record for the upper Pliocene and lower Pleistocene of ODP Hole 645B in Baffin Bay (as Tectatodinium sp. I in de Vernal and Mudie 1989a). Possible record for the middle Miocene through lower upper Pleistocene of the Norwegian Sea (as Tectatodinium pellitum and Dinocyst sp. I in Mudie 1989). Middle or upper Miocene through upper Pliocene of the Gulf of Mexico (as Tectatodinium sp. B in Wrenn and Kokinos 1986). Upper Miocene of the Bering Sea (as Filisphaera filifera in Matsuoka and Bujak 1988, pl. 3, fig. 3; see comments in Head 1994). Upper Miocene (Amaurolithus primus nannofossil Subzone CN9b of Okada and Bukry 1980) of DSDP Site 502 in the Caribbean Sea (J. Wrenn, pers. commun. in Head et al. 1989a). Lower and upper Pliocene of DSDP Hole 603C off Cape Hatteras in the western North Atlantic (Kolev et al. 1992). Lower and upper Pliocene of Hole 646B and lower Pleistocene? of ODP Hole 647A both in the Labrador Sea (as Tectatodinium sp. 1 in de Vernal and Mudie 1989b). Uppermost Pliocene of the Chillesford Church Pit in eastern England (this study), and uppermost Pliocene of the Ludham Borehole in eastern England (this study, and as Tectatodinium pellitum in Wall and Dale 1968a, pl. I, fig. 9 only).
Stratigraphic range: Middle (lower middle?) Miocene of Baffin Bay (Head et al. 1989c) through lower Pleistocene of Baffin Bay (de Vernal and Mudie 1989a) and possibly as high as lower upper Pleistocene of the Norwe~ian Sea (Mudie 1989).
Paleoecology: Head 1994, p. 304
The presence of this species throughout the Ludham Borehole succession, which was deposited in water depths of 40m or less to 8m or less (Funnell 1961; Norton 1967), indicates adaptation to inner neritic environments. Downslope transport and redeposition possibly help explain its presence in outer neritic and oceanic assemblages in the Neogene of the North Atlantic region, but these records might imply a broad ecological range across the shelf and slope. Geographic and stratigraphic distributions listed above indicate cool-water tolerance, as suggested by Head et al. (1989c). This species evidently endured a broad range of water temperatures from cool temperate to subtropical or tropical, but high numbers are mostly associated with cooler conditions within this range.
Biological affinity: Head 1994, p. 304, 306
The genus Habibacysta is assigned to the family Gonyaulacaceae owing to the presence of a precingular archeopyle, presumably Type P3", that implies gonyaulacoid paratabulation, but absence of other paratabular features prevents assignment to subfamily. The archeopyle in Habibacysta tectata has a smooth margin and rounded angles. In this respect, Habibacysta tectata is similar to Operculodinium centrocarpum sensu Wall and Dale 1968b which is the cyst produced by Protoceratium reticulatum (al. Gonyaulax grindleyi) although Operculodinium centrocarpum has processes. Judging from other examples in the cyst record (Evitt 1985), the rounded archeopyle in these species probably indicates an archeopyle suture that has not followed plate boundaries closely--indeed both cyst species appear to show very little expression of thecal tabulation. Specimens of O. centrocarpum sensu Wall and Dale 1968b recovered from the mid Pliocene Coralline Crag possess a tegillate/ columellate wall structure resembling that of Habibacysta tectata. A specimen is illustrated Plate ll,figs. 14, 15) for comparison.
Head (1996a, p.551) considered Filisphaera? minuta to be a possible taxonomic junior synonym of this species.
Holotype: Head et al., 1989b, pl.4, figs.1–2,5–6; Head, 1994a, pl.5, figs.1–6.
Locus typicus: ODP leg 105, site 646
Stratum typicum: Late Miocene-Early Pliocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Habibacysta tectata Head et al., 1989b. According to Head (1994a), has rods or granules that may be separate or adjacently fused. Ectophragm supported by the rods/granules is smooth and extremely thin and may be irregularly perforate or forms a delicate irregular reticulation, although it appears to be complete in some specimens. Size: diameter 29-45 µm. Ludham material: Size: cyst diameter 37-57 µm, wall thickness 0.8-1.4 µm.
--------------------------------------------------
Original diagnosis: Head et al., 1989, p.458
Cysts spherical, holocavate. Endophragm, thin and solid, bearing rods or granules (periphragm) that may be separate or adjacently fused. Ectophragm supported by the rods/granules is smooth and extremely thin and is commonly irregularly perforate or forms a delicate irregular reticulation, although it appears to be entire in some specimens. Archeopyle precingular formed by loss of paraplate 3". Operculum free. There is no other expression of paratabulation.
Dimensions. Holotype: cyst diameter, 33 Ám. Range in cyst diameter, 29(36)45 Ám. Total wall thickness, around 1 to 2 Ám. Fifteen specimens were measured.
Original description: Head et al., 1989, p.458
The ectophragm, especially in specimens where it is discontinuous, may only be detected under oil immersion by careful observation of optical sections of the cyst wall. Such observation suggests that the ectophragm may be entire in some specimens. Fine details of the ectophragm surface can only be observed with SEM.Plate 4, Figure 4 shows a discontinuous network of narrow irregular platforms (see also Wrenn and Kokinos 1986, Pl. 18, Fig. 6)." (Head et al. 1989b, p. 458).
--------------------------------------------------------------------------------------------------------------------------------------------------
Description: Head 1994, p. 300, 302
The following description is based on re-examination of the holotype by light microscopy. The cyst is uncompressed but slightly crumpled and spherical with an archeopyle (operculum missing) formed by loss of paraplate 3". The archeopyle margin is smooth and the angles appear rounded. There are no other indications of paratabulation. The pedium is thin (ca. 0.2Ám thick) and solid. The luxuria is both columellate and tegillate. Columellae are solid rods perpendicular to and arising from the pedium; most have circular cross sections ca. 0.3Ám in diameter. The distance between adjacent columellae varies from ca. 0.5Ám to ca. 1.5Ám, although occasional columellae are apparently fused. The tectum is discontinuous and extremely thin (thinner than pedium), hence visible only in optical section such as at periphery of the cyst. Total wall thickness ca. 1.1 Ám. These new details on the morphology of the holotype agree with the description and diagnosis of this species given in Head et al. (1989b, p. 458, see above). Specimens from Ludham Borehole and Chillesford Church pit closely resemble the type material. Cysts are spherical with characteristic tegillate wall. The pedium is very thin (0.3Ám or less), bearing slender, solid, perpendicular columellae of about 0.3Ám or less in diameter. Adjacent columellae are separated by about 0.5 to 1.5Ám, although their distribution is typically rather irregular with occasional fusion between adjacent columellae. The tegillum is visible under the light microscope only in optical section: the columellae, however, impart a distinctive pattern of small scattered dots in plan view. The archeopyle is formed by loss of the third precingular paraplate; the operculum is free. There are no accessory archeopyle sutures and the archeopyle has a relatively smooth outline with rounded angles. There are no other indications of paratabulation.
Dimensions: Holotype (uncompressed): Cyst length 33Ám, width 36Ám. Range in cyst diameter based on type material (from Head et al. 1989b), 29(36)45Ám. Ludham Borehole (sample IB 45-2): Cyst diameter maximum/ minimum averaged) 37(45.0)57Ám, wall thickness 0.9-1.7Ám. Thirty (compressed) specimens were measured. Chillesford Church (sample ChCh 5): Cyst diameter (maximum) 29(34.3)42Ám, wall thickness 0.8-1.4Ám. Twenty-one (uncompressed) specimens were measured.
Discussion: Head 1994, p. 302
SEM analysis of the Chillesford Church specimens reveals a perforated tegillum (see also Head et al. 1989b, pl. 4, fig. 4; and Wrenn and Kokinos 1986, pl. 18, fig. 6). The Ludham Borehole specimens were not examined under SEM but observations under the light microscope indicate no substantial differences with the Chillesford Church specimens. The larger average dimensions of the Ludham Borehole specimens may be an artifact resulting from their compressed preservation and possible swelling in the glycerine jelly mounting medium.
Comparison: Head 1994, p. 302, 304
Tectatodinium pellitum differs from Habibacysta tectata in having a spongy luxuria, compared with the columellate and tegillate luxuria in Habibacysta tectata. Furthermore, the archeopyle in Habibacysta tectata has rounded angles and a smooth margin, whereas in Tectatodinium pellitum it typically has well defined angles and irregular margin. Specimens identified as Tectatodinium pellitum by Mudie (1989, pl. 5, figs. 1, 5; and in Mudie et al. 1990, pl. 2, fig. 8) apparently represent a species of Habibacysta but details of the wall cannot be determined from the illustrations. Specimens identified as Tectatodinium pellitum by Harland (1988b, pl. 82; 1992, pl. 5.1, fig. 7) and Harland et al. (1991, fig. 4c) do not have the irregular archeopyle outline characteristic of Tectatodinium pellitum and are probably instead attributable to Habibacysta but details of the wall cannot be determined from the illustrations.
Tectatodinium sp. 1 of de Vernal and Mudie (1989a, pl. 1, figs. 9-11) is undoubtedly a species of Habibacysta but the wall is thicker than usual for H. tectata. De Vernal and Mudie's species is thus tentatively ascribed to Habibacysta tectata. Dinocyst sp.1 of Mudie (1989, pl. 5, figs. 4 and 8) resembles H. tectata but the presence of a lP archeopyle cannot be confirmed.
Bitectatodinium tepikiense differs from Habibacysta tectata in having a 2P archeopyle with well-defined angles, but when the archeopyle is not visible these two species are distinguishable by careful study of their wall structure--a sometimes necessary exercise because the species can occur in the same samples. In Bitectatodinium tepikiense the luxuria consists of a complex arrangement of lamellae that are perpendicular or subperpendicular to the pedium (see transmission electron micrographs in Jux 1976, pls. 2 and 3; SEM illustrations in Jux 1976, pl. 1, figs. 3a and 3b, Turon 1984, pl. 5, figs. 2, 3, and in Head and Wrenn 1992a, pl. 7 figs. 5-10 and see discussion therein). The bases of these lamellae are often thickened and subcircular in plan view, appearing under the light microscope as rounded granules or rods (see the description and illustrations of Caledonidium vermiculatum, a taxonomic junior synonym of B. tepikiense, in Reid 1974; and illustrations of the holotype of Bitectatodinium tepikiense in Wilson 1973). These thickened bases differ from the columellae in Habibacysta tectata by having larger diameters (about 0.5,um), a more dense distribution, and a greater tendency to be fused with adjacent bases. Careful analysis of the wall in optical section shows that a tegillum is not present in Bitectatodinium tepikiense unlike Habibacysta tectata.
Filisphaera filifera Bujak 1984 emend. Head 1994 differs from Habibacysta tectata in having a luxuria composed of radiating septa that form a distally open microreticulum (text-figure 3). Unlike Habibacysta tectata, the luxuria in Filisphaera filifera does not terminate distally as a tegillum.
cf. Habibacysta? sp. of Zevenboom in Head (1993 (ed.), p. 210, pl. 6, figs. 10-13), described from the middle Miocene of The Netherlands, differs from Habibacysta tectata in having a camerate 2P archeopyle with well defined angles, and a continuous tegillum (Head 1994).
Habibacysta tectata has a smooth surface in contrast to the low surface bumps that characterize Habibacysta? sp. (herein).
Occurrence in eastern England: Upper Pliocene Ludhamian (ca. 2.4 Ma) through Baventian (ca. 1.8 Ma) stages and possible lowermost Pleistocene of the Royal Society Borehole at Ludham, Norfolk, occurring in at least seven of the eight samples studied by Wall and Dale (1968a). Upper Pliocene Bramertonian Stage (ca. 2. 0 Ma) of the Chillesford Sand Member of the Norwich Crag Formation at Chillesford Church Pit, Chillesford, Suffolk.
Previous records: Head 1994, p. 304
Middle (lower middle?) Miocene through upper Pliocene or lower Pleistocene of ODP Site 645 in Baffin Bay (Head et al. 1989c; Anstey 1992) and possible record for the upper Pliocene and lower Pleistocene of ODP Hole 645B in Baffin Bay (as Tectatodinium sp. I in de Vernal and Mudie 1989a). Possible record for the middle Miocene through lower upper Pleistocene of the Norwegian Sea (as Tectatodinium pellitum and Dinocyst sp. I in Mudie 1989). Middle or upper Miocene through upper Pliocene of the Gulf of Mexico (as Tectatodinium sp. B in Wrenn and Kokinos 1986). Upper Miocene of the Bering Sea (as Filisphaera filifera in Matsuoka and Bujak 1988, pl. 3, fig. 3; see comments in Head 1994). Upper Miocene (Amaurolithus primus nannofossil Subzone CN9b of Okada and Bukry 1980) of DSDP Site 502 in the Caribbean Sea (J. Wrenn, pers. commun. in Head et al. 1989a). Lower and upper Pliocene of DSDP Hole 603C off Cape Hatteras in the western North Atlantic (Kolev et al. 1992). Lower and upper Pliocene of Hole 646B and lower Pleistocene? of ODP Hole 647A both in the Labrador Sea (as Tectatodinium sp. 1 in de Vernal and Mudie 1989b). Uppermost Pliocene of the Chillesford Church Pit in eastern England (this study), and uppermost Pliocene of the Ludham Borehole in eastern England (this study, and as Tectatodinium pellitum in Wall and Dale 1968a, pl. I, fig. 9 only).
Stratigraphic range: Middle (lower middle?) Miocene of Baffin Bay (Head et al. 1989c) through lower Pleistocene of Baffin Bay (de Vernal and Mudie 1989a) and possibly as high as lower upper Pleistocene of the Norwe~ian Sea (Mudie 1989).
Paleoecology: Head 1994, p. 304
The presence of this species throughout the Ludham Borehole succession, which was deposited in water depths of 40m or less to 8m or less (Funnell 1961; Norton 1967), indicates adaptation to inner neritic environments. Downslope transport and redeposition possibly help explain its presence in outer neritic and oceanic assemblages in the Neogene of the North Atlantic region, but these records might imply a broad ecological range across the shelf and slope. Geographic and stratigraphic distributions listed above indicate cool-water tolerance, as suggested by Head et al. (1989c). This species evidently endured a broad range of water temperatures from cool temperate to subtropical or tropical, but high numbers are mostly associated with cooler conditions within this range.
Biological affinity: Head 1994, p. 304, 306
The genus Habibacysta is assigned to the family Gonyaulacaceae owing to the presence of a precingular archeopyle, presumably Type P3", that implies gonyaulacoid paratabulation, but absence of other paratabular features prevents assignment to subfamily. The archeopyle in Habibacysta tectata has a smooth margin and rounded angles. In this respect, Habibacysta tectata is similar to Operculodinium centrocarpum sensu Wall and Dale 1968b which is the cyst produced by Protoceratium reticulatum (al. Gonyaulax grindleyi) although Operculodinium centrocarpum has processes. Judging from other examples in the cyst record (Evitt 1985), the rounded archeopyle in these species probably indicates an archeopyle suture that has not followed plate boundaries closely--indeed both cyst species appear to show very little expression of thecal tabulation. Specimens of O. centrocarpum sensu Wall and Dale 1968b recovered from the mid Pliocene Coralline Crag possess a tegillate/ columellate wall structure resembling that of Habibacysta tectata. A specimen is illustrated Plate ll,figs. 14, 15) for comparison.