Palynological specimens are curated at the Atlantic Geoscience Centre, Bedford Institute of Oceanography; curation numbers and England finder references are given in Plate captions. The classification of dinoflagellates follows Fensome et al. (1993). All formal names follow the nomenclatural index of Lentin and Williams (1993), where synonyms are given.
Division PYRRHOPHYTA Pascher 1914
Class DINOPHYCEAE Fritsch 1929
Genus ACHOMOSPHAERA Evitt, 1963
Achomosphaera andalousiensis Jan du
Chêne, 1977
emend. Jan du Chêne and Londeix, 1988
(Plate 3, Fig.7)
Remarks: Most specimens of this species in Holes 898A and 900A have two or more complex, reticulated process tips, typical of the upper Miocene holotype of Jan du Chêne (1977). Some middle Miocene specimens, however, are not clearly distinguishable from A. callosa Matsuoka, 1983 and A. ramosasimilis (Yun, 1981) Londeix et al., 1992, which are reported from upper and lower Pliocene sediments of the Mediterranean (Benzakour, 1992). It is notable that A. andalousiensis shows cyclical high abundances in Pleistocene sediments at the study sites, in the northwest Atlantic (ODP Site 647 and survey site 89007-11), and in the subtropical Gulf of California (Byrne et al., 1990); these abundance peaks are strongly correlated with early interglacials, suggesting that this species prefers warm, relatively low salinity (melt-water/fluvial) conditions.
Achomosphaera ramulifera (Deflandre)
Evitt, 1963
(Plate 3, Fig. 8)
A well-known species, usually with a LAD in the late Pliocene, but rarely present or redeposited in lower Pleistocene deposits at many North Atlantic sites (e.g., Mudie, 1987; 1989; de Vernal and Mudie, 1989).
Genus AMICULOSPHAERA Harland 1979
Amiculosphaera umbracula Harland, 1979
(Plate 3, Fig. 18)
This distinctive species is found in Pliocene-Pleistocene sediments in Holes 898A and 900A. This species has been reported from upper Miocene through early Pleistocene sediments at northeast Atlantic Sites 400, 607, 611, and 642 (Harland, 1979; Mudie 1987, 1989), but it is not known from the northwest Atlantic Ocean or Mediterranean Sea.
Genus APTEODINIUM Eisenack, 1958
Apteodinium australiense (Deflandre and Cookson, 1955) Williams, 1978
(Plate 1, Fig. 5)
Specimens assigned to this species are large proximochorate cysts (diameter >60 µm) with a well-developed apical horn, a well-defined wide paracingulum, and a non-cavernous finely spongy-granulate wall. In the North Atlantic, A. australiense has a mid-middle Miocene LAD (Williams et al., 1993); it has not been reported for the Mediterranean.
Apteodinium? sp. A Powell 1986b
(Plate 1, Fig. 1)
Specimens from both Holes 898A and 900A resemble the species from lower Miocene sediments of the Italian Lemme Section, as illustrated by Powell (pl. 6, fig. 3; 1986b). Apteodinium? sp. A is a pear-shaped to ovoidal auto-cyst, with a low apical horn and an irregularly alveolate cyst wall, the surface of which is sparsely papillate. The paracingulum is indicated by low obtuse ridges; the archeopyle is precingular. This species is distinguished from A. spiridoides and from the late middle Miocene species Apteodinium sp. 1 of Head et al., 1989c by its smaller size (diameter ~50 µm), by the well-defined paracingulum and the finer alveolate ornament and presence of papillae.
Apteodinium spiridoides Benedek, 1972
(Plate 1, Fig. 6)
Specimens are large (diameter ~80 µm) and cavernous, without visible paratabulation or apical horn. The outer cyst wall is ornamented by large irregular alveoli and scattered verrucae. This species has a HO (highest occurrence) at or below the early/middle Miocene boundary at most North Atlantic sites although there are also a few reports for the early middle Miocene (Head et al., 1989c), and Haq et al. (1988) correlated the highest occurrence of this species to the early middle Miocene biozones NN5 and N10. A. spiridoides differs from the related species Apteodinium tectatum in its thick fibrous (can-cellous) outer wall structure (see Head and Wrenn, 1992).
Genus BATIACASPHAERA Drugg, 1970
Batiacasphaera sphaerica Stover 1977
(Plate 1, Fig. 7)
Specimens assigned to this species were consistently rounded and relatively thick-walled, with uniformly papillate surfaces, and are distinct from smaller crumpled cysts that may belong to the B. micropapillata Stover, 1977 "complex" described by Head et al., 1989c. B. sphaerica has an early to late Miocene range in the North Atlantic (Head et al., 1989c).
Genus BITECTATODINIUM Wilson, 1973
Bitectatodinium tepikiense Wilson, 1973
(Plate 4, Fig. 10; Plate 5, Figs. 5,
6)
This cyst is abundant in modern sediments where it is well preserved and clearly shows the distinctive camerate archeopyle associated with the loss of two dorsal precingular paraplates at excystment, and the sub-erect branching lamellate nature of the periphragm ornament which arises from raised bases, as described by Head (1994a). On the Iberia Abyssal Plain, B. tepikiense is only abundant in late Pliocene and younger sediments. Rare specimens in Miocene sediments are larger, with thicker walls and denser, less regularly oriented lamellae.
Genus BRIGANTEDINIUM Reid, 1974
Brigantedinium spp.
(Plate 4, Fig. 6)
Round or oblong cysts with a dark brown wall color, pentagonal archeopyle and absence of surface ornament, are assigned as Brigantedinium species. Many cysts could be ascribed to either B. simplex (Wall, 1965) Reid, 1977 (see Pl. 4, Fig. 6) or to B. cariacoense (Wall, 1967) Reid, 1977, but other forms could not be identified at the species level due to damaged/hidden archeopyle areas.
Genus CALIGODINIUM Drugg, 1970
Caligodinium pychnum Biffi and Manum, 1988
(Plate 1, Fig. 9)
Specimens from the Iberia Abyssal Plain are large (75 × 30 µm), with a coarsely reticulate epiphragm and cone-shaped verrucae, closed at the tips, and closely resemble early Miocene cysts from the northwest Atlantic (Williams and Bujak, 1977). Specimens from the Mediterranean late Oligocene to early Miocene (Brinkhuis et al., 1992) are broader and less elongate in shape, with a finer reticulate ornament. C. pychnum has a HO in early Miocene sediments of the North Atlantic (Williams et al., 1993) and the Mediterranean region (Brinkhuis et al., 1992).
Genus CANNOSPHAEROPSIS O. Wetzel, 1933, emend. Williams and
Downie, 1966
Cannosphaeropsis cf. C. utinensis O. Wetzel, 1933 sensu Brown and
Downie, 1986
(Plate 2, Fig. 10)
In Holes 898A and 900A, early Miocene specimens resembling C. utinensis have long processes with periphragm trabeculae in the paracingular region and a finely punctate endophragm. Similar specimens have been found in lower Eocene through upper Miocene sediments of the North Atlantic region, and according to Head and Wrenn (1992), this cyst form is now recognized as a species distinct from C. utinensis O. Wetzel, 1933 sensu Brown and Downie, 1986. It is being studied by L. de Verteuil who refers to the species as Cannosphaeropsis "passio" (G.L. Williams, pers. comm., 1995).
Genus CHIROPTERIDIUM Gocht, 1960
Chiropteridium mespilanum (Maier, 1959) Lentin and Williams 1973
(Plate 2, Fig. 13)
Poorly preserved specimens of this species are not easily distinguished from the Oligocene-early Miocene species C. partispinosum. Specimens from the Iberia Abyssal Plain, however, are relatively small and resemble illustrations of C. mespilanum from Miocene sections in Italy (Powell, 1986a,b).
Genus CORRUDINIUM Stover and Evitt, 1978
Corrudinium harlandii Matsuoka, 1983
(Plate 4, Fig. 20)
This species is rare in upper Miocene sediments of Hole 900A.
Genus CYCLOPSIELLA
Cyclopsiella granosa (Matsuoka 1983) Head et al., 1992
(Plate 1, Fig. 11)
Specimens with granulate ornamentation are occasionally present in lower Miocene sediments in Holes 898A and 900A, and are assigned to C. granosa. This species has an early middle Eocene to middle Miocene range in the North Atlantic and has been reported from the Pleistocene in Australia (Head and Wrenn, 1992). It appears to be characteristic of warm-water regions (see Head and Wrenn, 1992).
Genus DAPSILIDINIUM Bujak et al., 1980
Dapsilidinium pastielsii (Davey and Williams, 1966) Bujak et al., 1980
(Plate 1, Fig. 2)
This species is common in the lower Miocene sediments from the Iberia Abyssal Plain, together with D. pseudocolligerum, from which it usually differs by its more rigid, conical spines, with small flared tips and broad bases. However, there may be intergrades between these two taxa.
Dapsilidinium pseudocolligerum (Stover, 1977) Bujak et al.,1980
(Plate 1, Fig. 12)
This species is common in lower Miocene sediments from the Iberia Abyssal Plain and typically has long, relatively weak, simple or bifurcate processes (up to 1/3 body width). The process tips are often bent or recurved, and always have flared distally open tips. However, there may be intergrades with D. pastielsii.
Dapsilidinium sp. of Wrenn and
Kokinos, 1986
(Plate 1, Fig. 10)
Middle late Miocene and early Pliocene specimens resembling D. pseudocolligerum but with smaller, with short, variable processes may be the species illustrated by Wrenn and Kokinos from the Gulf of Mexico (pl. 10, figs. 8-10; 1986).
Genus DISTATODINIUM Eaton, 1976
Distatodinium paradoxum (Brosius, 1963) Eaton, 1967
(Plate 2, Fig. 4)
This species is rare in lower Miocene samples from the Iberia Abyssal Plain; this is consistent with its reported LAD in the earliest Miocene of the North Atlantic (Williams et al., 1993).
Genus FILISPHAERA Bujak, 1984 emend. Head in Head, 1994b
Filisphaera filifera Bujak, 1984, emend. Head in Head, 1994b
(Plate 2, Figs. 14, 15; Plate 4, Fig.
9)
Brownish cysts with a microreticulate periphragm of narrow septa and precingular archeopyle were assigned to this species, which also includes rare Pliocene forms with pilose ornament of radiating fibres (F. filifera ssp. pilosa). F. filifera has a late Miocene to earliest Pleistocene distribution in the North Atlantic (Head, 1994) but this cool-water species (Versteegh and Zonneveld, 1994) is rare and poorly preserved in middle Miocene and late Pliocene sediments at Site 898 and may be reworked. F. filifera ssp. pilosa has a Pliocene range in the Bering Sea (Head, 1994b) and North Atlantic Site 611 (Mudie, 1987).
Genus GALEACYSTA Corradini and
Biffi, 1988
Galeacysta etrusca Corradini and Biffi, 1988
(Plate 2, Fig. 12)
Specimens assigned to this species are rare and poorly preserved, suggesting possible reworking; however, this cyst may be a marker of transport in Mediterranean overflow water.
Genus HABIBACYSTA Head et al., 1989b
Habibacysta cf. H. tectata Head et al., 1989b
(Plate 4, Fig. 5; Plate 5, Fig. 8,
10)
Cysts resembling H. tectata are rare in Hole 898A, and few of them have a clearly visible archeopyle. Some forms, however, were found with an attached opercular paraplate, which distinguishes them from the Labrador Sea topotypes (Head et al., 1989b) and Norwegian Sea specimens (Mudie, 1989). The Iberia Abyssal Plain cyst form may be more similar to the Gulf of Mexico cyst Tectatodinium sp. A of Wrenn and Kokinos (1986; pl. 5, fig. 3) which has an attached operculum. This cyst form and Tectatodinium sp. II of de Vernal and Mudie, 1989 from Hole 898A (see Pl. 4, Fig. 14) need SEM study to define the exact nature of the ectophragm structure.
Genus HOMOTRYBLIUM Davey and Williams, 1966
Homotryblium floripes (Deflandre and Cookson, 1955) Stover, 1975
(Plate 2, Fig. 8)
These cysts showed a large variability in process development, particularly with respect to the length and width of the large hollow processes. Some intergradation with the contemporary populations of H. oceanicum and H. vallum and/or H, tenuispinosum may account for this variation. H. floripes has an Oligocene to late early Miocene range in the North Atlantic (Williams et al., 1993).
Homotryblium oceanicum Eaton, 1976
(Plate 2, Fig. 3)
Only a few strongly oxidized specimens of this species were found in lower Miocene sediments. This species is restricted to the Eocene at most North Atlantic sites (Williams and Bujak, 1985) and is probably reworked on the Iberia Abyssal Plain.
Homotryblium tenuispinosum Davey and Williams, 1966
(Plate 1, Fig. 3)
Specimens assigned to this category differ from H. floripes in having longer, thinner processes. This species is rare and may be reworked from Paleogene sediments.
Homotryblium vallum Stover, 1977
(Plate 2, Fig. 7)
This species occurs in lower Miocene sediments in Holes 898A and 900A, which is consistent with its late Oligocene to late early Miocene range in the North Atlantic (Williams et al., 1993).
Genus HYSTRICHOKOLPOMA Klumpp, 1953, emend. Williams and Downie, 1966
Hystrichokolpoma cinctum Klumpp, 1953
(Plate 3, Fig. 16)
This species is rare in lower Miocene sediments in Holes 898A and 900A; it has a middle early Miocene LAD in the North Atlantic according to Williams et al. (1993).
Hystrichokolpoma rigaudiae Deflandre and Cookson, 1955
(Plate 2, Fig. 6)
This species has a Paleogene through lower Pliocene range in the North Atlantic (Williams et al., 1993) and is present in Italian Pliocene sections (Habib, 1971; Powell, 1986c).
Genus HYSTRICHOSPHAEROPSIS Deflandre, 1935
Hystrichosphaeropsis obscura Habib, 1972
(Plate 3, Fig. 13)
Few, poorly preserved specimens of this species were found in lower Miocene sediments in Hole 900A. Smaller, well-preserved specimens occur in the middle Miocene and upper Pliocene at both sites.
Genus IMPAGIDINIUM Stover and
Evitt, 1978
Impagidinium aculeatum (Wall) Lentin and Williams, 1981
(Plate 4, Fig. 12)
There is a notable decrease in the size of this well-known species from its first occurrence in the middle Miocene to Pleistocene sediments in both Holes 898A and 900A. Miocene specimens have an typical size of ~50 × 45 µm compared to ~35 × 30 µm in Pliocene-Pleistocene sediments.
Impagidinium aliferum Mudie, 1987
(Plate 4, Fig. 11)
This species is probably often overlooked and counted as I. aculeatum although its larger body size (55 × 30-35 µm) and expanded (4—8 µm) parasutural crests are consistently distinctive. This species has a Pliocene range at the Iberia Abyssal Plain sites and at DSDP Site 607 west of the Azores. At DSDP Site 611 south of Iceland, its range extends to the upper Miocene (Mudie, 1987).
Impagidinium aspinatum (Cookson and Eisenack, 1974)
Damassa, 1979
(Plate 5, Fig. 1)
Specimens ascribed to this species occur in the lower Miocene of Hole 898A and resemble Impagidinium sp. cf. I. aspinatum of Powell (1986b) as illustrated for lower Miocene sediments at the Italian Lemme section. Both Lemme and Iberia Abyssal Plain specimens are dark in color, suggesting possible reworking of the Paleogene species I. aspinatum.
Impagidinium bacatum Londeix et al., 1992
(Plate 4, Fig. 4; Plate 5, Fig.
9)
This species is rare in upper Pliocene sediments in Hole 900A; this is consistent with its acme in the Mediterranean in the upper Pliocene (Benzakour, 1992; Londeix et al., 1992). Under light microscopy, it is difficult to distinguish I. bacatum from the Mesozoic I. pentahedrias, and the Paleogene species I. aspinatum, and some specimens assigned to I. bacatum may be reworked Cretaceous cysts.
Impagidinium patulum (Wall,
1967) Stover and
Evitt, 1978
(Plate 4, Fig. 21)
This well-known species has its FAD in the early Miocene in Hole 898A, but its acme occurs in middle Pleistocene sediments in Hole 898A, and in upper Miocene to lower Pliocene sediments in Hole 900A, where it may form almost monospecific assemblages. Very little variation in size or morphology has been observed in the Iberia Abyssal Plain, central North Atlantic and Mediterranean samples (Mudie, 1987; Aksu et al., 1995), in contrast to the size variation in Miocene sediments reported by Edwards (1984) and by Head et al. (1989b).
Impagidinium sphaericum (Wall, 1967) Stover and Evitt, 1978
(Plate 4, Fig. 25)
This species appears much later (Pliocene) in the eastern North Atlantic than I. patulum with which it is sometimes confused. The two taxa are easily distinguished by the smaller size and more rounded body of I. sphaericum, and its very low or missing parasutural crests.
Impagidinium sp. A of Mudie, 1987
(Plate 4, Figs 22a and 22b)
These small Impagidinium cyst forms appear to be the same as those described and illustrated from samples studied in the subtropical and subarctic N. Atlantic (Mudie, 1987) and the arctic Labrador and Norwegian Seas (Mudie, 1987; 1989), where they are abundant in the lower Pliocene sediments. In the Iberia Abyssal Plain cores, however, they have their acme in the late Pliocene.
Impagidinium sp. F Wrenn and
Kokinos, 1986
(Plate 4, Fig. 18)
This species is not always easily distinguishable from, and may include, specimens of I. japonicum Matsuoka, 1983 (Plate 4, Fig. 13).
Genus INVERTOCYSTA Edwards, 1984
Invertocysta lacrymosa Edwards, 1984
(Plate 3, Fig. 15)
Specimens of I. lacrymosa from Miocene sediments were often poorly preserved, in contrast to common occurrences of well-preserved cysts in upper Pliocene sediments at both sites. Rare specimens of I. tabulata (Plate 2, Fig. 2) were also seen in Miocene and Pliocene sediments.
Genus LABYRINTHODINIUM
Labyrinthodinium truncatum Piasecki, 1980
(Plate 4, Fig. 29)
Specimens of this middle Miocene marker are rare in the Iberia Abyssal Plain sediments and well preserved cysts were found only in Hole 900A. This species has a late early Miocene to early late Miocene range in the North Atlantic (Head et al., 1989b), but it has not previously been reported for the Mediterranean region and it was not reported by Harland (1979) for DSDP Site 400 off the Bay of Biscay.
Genus LEJEUNECYSTA Artzner and Dorhofer, 1978 emend. Lentin and Williams, 1976
Lejeunecysta communis Biffi and Grignani, 1983
(Plate 4, Fig. 17)
Poorly preserved (oxidized) specimens are rare in upper Pliocene-Pleistocene samples in Hole 898A, but not in Hole 900A, although the species is common in Pliocene sediments of the Mediterranean (Biffi and Grignani, 1983) and the outer shelf off Newfoundland (Mudie, pers. observation). Some of these specimens may be conspecific with L. marieae Harland in Harland et al. (1991) which is common in upper Pliocene deltaic and paralic sites, as at the St. Erth beds (Head, 1993).
Genus LINGULODINIUM Wall, 1967 emend. Dodge 1989
Lingulodinium machaerophorum (Deflandre and Cookson, 1955) Wall, 1967
(Plate 3, Fig. 1)
This is the most common species throughout both sites on the Iberia Abyssal Plain, yet it shows relatively little morphological change from Miocene to Pleistocene, and all excysted specimens showed almost complete loss of all epicystal paraplates, with only the sulcal paraplate remaining attached. In general, Miocene specimens have relatively short blade-shaped processes, or rarely, very short, club-shaped processes. In contrast, most Pliocene-Pleistocene specimens had long, flexuous blade-shaped processes. These morphological variations may be related to different paleoenvironmental conditions as noted in Head (1993).
Genus MELITASPHAERIDIUM Harland and Hill, 1979
Melitasphaeridium choanophorum (Deflandre and Cookson, 1955) Harland and Hill, 1979
(Plate 4, Fig. 28)
In Hole 898A, well-preserved specimens of this cyst form are rare in the Pliocene to early Pleistocene interval, but fragments of process tips resembling those of the species may indicate reworking. This species is found in upper Miocene sediments in Hole 900A.
Genus MULTISPINULA Bradford, 1975
Multispinula? minuta Harland and Reid in Harland et al., 1980
This species is questionably included in the genus Algidasphaeridium by Lentin and Williams (1993) who list it as Algidasphaeridium? minutum (Harland and Reid in Harland et al., 1980) Matsuoka and Bujak, 1988, a species described as having a chasmic archeopyle. Paratype specimens from the Beaufort Sea were studied by Mudie (1992) and these clearly have an intercalary rather than chasmic archeopyle, so we retain the generic name Multispinula at this time.
Multispinula quanta Bradford, 1975
This species is present at both sites, but it is most common in lower Pleistocene sediments from Hole 898A.
?Multispinula sp.
(Plate 4, Fig. 8)
Specimens are small brown cysts (body diameter 30-35 µm) with short, solid spines ~1/4 of the body length and expanded process tips. A pentagonal archeopyle outline was seen in some specimens.
Multispinula sp. of Wrenn and Kokinos, 1986
(Plate 3, Fig. 2)
These cysts are similar to M. quanta, but much larger (75 µm maximum body diameter) and with wider (>2µm) spine-bearing paracingular margins.
Genus NEMATOSPHAEROPSIS Deflandre and
Cookson, 1955
emend. Williams and Downie, 1966
Nematosphaeropsis labyrinthus (Ostenfeld, 1903) Reid, 1974
(Plate 4, Fig. 15)
Specimens with the typical features of this species (as shown in Plate 4) appear only in the Pliocene-Pleistocene sediments on the Iberia Abyssal Plain. Similar cysts in older sediments are smaller and crumpled, so they could not be assigned with certainty to either Nemotosphaeropsis or Cannosphaeropsis.
Nematosphaeropsis major Head et al., 1989a
(Plate 3, Fig. 19)
Well-preserved specimens of this species are rare in lower Miocene sediments in Hole 898A and in middle Miocene sediments in Hole 900A.
Nematosphaeropsis oblonga Mudie, 1987
(Plate 4, Figs. 23, 24)
Specimens of this middle Miocene-late Pliocene species are very similar to those found at DSDP Sites 607 and 611 in the central North Atlantic (Mudie, 1987). This species is also found in Pliocene sediments of Site 647, Labrador Sea (de Vernal and Mudie, 1989), and it may overlap with some morphotypes of Nematosphaeropsis sp. 1 of Head et al., 1989b from the upper Miocene of the Labrador Sea, which also has rod-like trabeculae and an elongate body with finely granular surface ornament. Nematosphaeropsis oblonga consistently differs in morphology from N. lemniscata, even within the same populations as seen at Sites 611 and 607 in the N. Atlantic, and it is clearly a separate species despite the opinion of Wrenn (1988), as discussed in Head and Wrenn (1992).
Genus OPERCULODINIUM Wall, 1967
Operculodinium centrocarpum (Deflandre and Cookson) Wall, 1967
(Plate 3, Fig. 17)
The literature contains a high diversity of morphotypes that have been assigned to this species. Miocene specimens resemble the Australian holotype which are larger and more robust than modern specimens; this morphotype is rare in Holes 898A and 900A. Pliocene and Pleistocene specimens at the two sites closely resemble the species in modern and Pliocene-Pleistocene sediments of the Atlantic, Arctic, and Mediterranean regions, and have relatively long processes (~half body diameter), of uniform length and with bifurcate tips.
Operculodinium crassum Harland, 1979
(Plate 3, Fig. 10)
Recently Harland (in Head and Wrenn, 1992) opined that O. crassum and O. israelianum are synonymous, with O. crassum the junior homonym. Study of the abundant specimens in the Iberia Abyssal Plain cores, however, and knowledge of the range of morphology in Pleistocene Mediterranean sediments (Aksu et al., 1995) leads to the conviction that there are two species. 0. crassum has a thick wall (2-4 µm) and sturdy spines at least one-third of the body diameter, while O. israelianum (Plate 3, Fig. 9) has a thinner wall and shorter spines, ~one-tenth of the body diameter. The two taxa are almost co-dominant in lower Pliocene sediments, but O. crassum is dominant or exclusively present in older sediments, and O. israelianum dominates in the Pleistocene sediments.
Operculodinium? eirikianum Head et al., 1992
(Plate 3, Fig. 12)
Specimens of this species are easily distinguished from poorly preserved specimens of O. longispinum primarily by the microreticulate wall ornament and shorter (<10 µm) processes. Characteristic features of Iberia Abyssal Plain specimens of 0.? eirikianum are the recurved processes which are variable in length, with several different tip shapes, ranging from bifurcate to acute or acuminate, and the strongly microreticulate wall ornament.
Operculodinium israelianum (Rossignol) Wall, 1967
(Plate 3, Fig. 9)
See notes for O. crassum.
Operculodinium janduchenei Head et al., 1992
(Plate 4, Fig. 1; Plate 5, Fig.
7)
The processes in this species are very variable in length and morphology (Head et al., 1989a). In this study, only specimens with sturdy conical spines and apparently closed tips were assigned to this species.
Genus PALAEOCYSTIDINIUM Palaeocystidinium golzowense Alberti, 1961
(Plate 1, Fig. 4)
This species is rare in the lower Miocene sediments from the Iberia Abyssal Plain. This distribution contrasts with the common occurrence of this species in middle through upper Miocene sediments in the northern North Atlantic (Head et al., 1989b: Mudie, 1989).
Genus PENTADINIUM Gerlach, 1961 emend. Benedek et al., 1982
Pentadinium laticinctum Gerlach, 1961 emend. Benedek et al., 1982
(Plate 2, Fig. 5)
Genus POLYSPHAERIDIUM Davey and Williams, 1966; emend. Bujak et al., 1980
Polysphaeridium congregatum (Stover, 1977) Bujak et al. 1980
(Plate 3, Fig. 6)
This species, which is rare in lower Miocene sediments in Holes 898A and 900A, has an Oligocene to early Miocene range in most of the North Atlantic (G.L. Williams, pers. comm, 1995), but it is not present in Baffin Bay (Head et al., 1989c), Labrador Sea (Head et al., 1989b), or the Norwegian Sea (Manum et al., 1989).
Polysphaeridium zoharyi (Rossignol, 1962) Bujak et al., 1980
This species is common throughout the Iberia Abyssal Plain sections, but shows greater morphological variation in lower Miocene sediments were P. zoharyi subsp. ktana (Rossignol) Lentin and Williams 1981 is present.
Genus PYXIDIELLA Cookson and
Eisenack, 1958
Pyxidiella? simplex Harland, 1979
(Plate 4, Figs. 2, 16; Plate 5, Fig.
3)
This species includes a wide range of small oblong cysts with granulose to verrucose ornament and an apparently intercalary archeopyle. Two cyst forms are present in middle Miocene sediments in Hole 900A. Most specimens have a slightly elongate apical boss and predominantly conate ornamentation (Plate 4, Fig. 2; Plate 5, Fig. 3) and they appear similar to the late Miocene species described by Harland (1979). Other specimens have a more rounded shape (Plate 4, Fig. 16), predominantly granulate ornament, and the archeopyle is large, with a pentagonal outline; this morphotype more closely resembles the cyst form from middle to upper Miocene sediments at DSDP Site 555, Rockall Plateau (Edwards, 1984), which was referred to as Tectatodinium simplex (Harland) Edwards 1984.
Genus RETICULATOSPHAERA Matsuoka, 1983 emend. Bujak and Matsuoka, 1986
Reticulatosphaera actinocoronata (Benedek, 1972) Bujak and Matsuoka, 1986
This species is occasionally present in middle Miocene through upper Pliocene samples at both Sites 898 and 900. This species has a late Eocene to early Pliocene range in the North Atlantic (Head et al., 1989b).
Genus SELENOPEMPHIX Benedek, 1972 emend. Head, 1993
Selenopemphix nephroides Benedek, 1972 emend. Bujak, 1980
(Plate 3, Figs 3, 5; Plate 4, Fig.
3)
Pliocene and early Pleistocene specimens attributed to this species are often crumpled and cannot equivocally be assigned to this species (Plate 4, Fig. 3). Some well-preserved specimens (Plate 3, Fig. 3) show an archeopyle slightly offset to the right side of the cyst, and smooth paracingular margins. Similar variation of archeopyle symmetry was found in specimens of S. nephroides in upper Pliocene samples from southwest England (Head, 1993). Other specimens in Hole 898A have an almost symmetrical archeopyle (Plate 3, Fig. 5) and serrate wing ornament similar to that found in the late Miocene to lower Pliocene species Selenopemphix brevispinosa Head et al., 1989c. S. nephroides is common through the late Pliocene and early Pleistocene of the northeast Atlantic, although it disappears in the early Pleistocene in the northwest Atlantic (de Vernal and Mudie, 1989).
Genus SPINIFERITES Mantell, 1850 emend.
Sarjeant, 1970
Spiniferites mirabilis (Rossignol) Sarjeant, 1970
(Plate 4, Fig. 27; Plate 5, Fig.
4)
This species appears to occur throughout the section at both sites; however, there is a change in the morphology of the compound antapical process and in the length of the gonal processes. Miocene specimens tend to have relatively short spines, with one posterior spine only partly fused to the compound process, in contrast to Pliocene-Pleistocene specimens that have fully fused antapical processes and longer, more branched gonal processes.
Spiniferites ramosus (Ehrenberg) Loeblich and Loeblich, 1966
This taxon includes specimens assigned by other workers to Spiniferites bulloideus (Deflandre and Cookson) Sarjeant, 1970, since there appears to be complete gradation between both forms in the samples studied.
Spiniferites splendidus Harland, 1979
(Plate 4, Fig. 26)
Spiniferites spp.
This category includes unknown taxa similar to S. ramosus/S. mirabilis and broken/obscured/poorly preserved cysts obviously attributable to this genus, but which could not be identified to species level were counted as Spiniferites sp. The group may include some species of the genus Achomosphaera Evitt, 1963.
Genus STELLADINIUM Bradford, 1975
Stelladinium stellatum (Wall and Dale, 1968) Reid, 1977
(Plate 4, Fig. 19)
Specimens of this species are rare and usually poorly preserved in the Pliocene-Pleistocene sediments in Hole 898A and are absent from Hole 900A.
Genus SUMATRADINIUM Lentin and Williams, 1976
Sumatradinium druggii Lentin et al., 1994
(Plate 3, Fig. 11)
Specimens assigned to this Sumatradinium species showed a very wide range of process length and tip branches; more than one species may be present in the middle Miocene to lower Pliocene sediments at both Iberia Abyssal Plain sites, although the Pliocene specimens may be reworked.
Sumatradinium hispidum Lentin et al., 1994
(Plate 3, Fig. 4)
This species was found only in late Pliocene sediments in Hole 898A. It is distinguished, with difficulty, from short-spined forms of Multispinula? minuta by its larger size (>60 µm) and granuloreticulate wall ornament. According to Head (1994b), the genus Sumatradinium has its LAD in the late Miocene; hence the Pliocene specimens may be reworked.
Genus TECTATODINIUM Wall, 1967
Tectatodinium pellitum Wall, 1967
This species is rare in early Miocene through Pleistocene sediments on the Iberia Abyssal Plain. Early Miocene specimens in Sample 149-898A-28X-2, 58-60 cm are large (~70 µm, slightly compressed) with walls ~5 µm thick, falling in the uppermost range of specimens studied by Head (1994a). Pliocene-Pleistocene specimens have a diameter ~60 µm and wall thickness of 3 µm.
Tectatodinium sp. II of de Vernal and
Mudie, 1989
(Plate 4, Fig. 14)
See comments for Habibacysta.
Genus THALASSIPHORA Eisenack and
Gocht, 1960
Thalassiphora delicata Williams and Downie, 1966
(Plate 2, Fig. 11)
Specimens of this species usually appeared thin-walled and oxidized: it is not clear if they are redeposited but their occurrence at both Iberia Abyssal Plain sites suggest that they are autochthonous.
Thalassiphora pelagica Eisenack and Gocht, 1960
(Plate 5, Fig. 2)
Specimens resembling this cyst form were rare and poorly preserved in lower Miocene sediments from both Iberia Abyssal Plain sites.
Thalassiphora cf. T. pansa of
Mudie, 1989
(Plate 2, Fig. 1)
This cyst form showed a wide range in development of the protruding periphragm structures that characterize T. pansa; some specimens more closely resembled the middle Miocene Dinocyst sp. 7 of Manum et al., 1989.
Genus TUBERCULODINIUM Wall, 1967
Tuberculodinium vancampoae (Rossignol, 1962) Wall, 1967
(Plate 1, Fig. 8)
Specimens of this species are often smaller in Miocene sediments than in upper Pliocene sediments where larger specimens similar to modern cyst forms were common in Hole 898A.