Tabulation patterns in some fossil representatives of the dinoflagellate family Cladopyxiaceae Stein 1883

ABSTRACT

Several fossil dinoflagellates assignable to Microdinium, Histiocysta and Cladopyxidium are small, yet distinctive subspheroidal to ellipsoidal forms that share several discriminative morphological features. The epicyst is smaller than the hypocyst, and the cingulum, which is only slightly offset ventrally, is exceptionally wide. The specimens all have apical archeopyles and possess sutural features indicating a gonyaulacalean tabulation of 4′, 3–5a, 7″, 6c, 6‴, 1p, 1″″, and 5–6s. However, the proportions and shapes of some plates and their relative positions differ significantly from plate relationships on other gonyaulacalean genera having similar tabulation formulas. The differences pertain mainly to the hypocyst, but on some forms modification of certain plates on the epicyst is also involved. Point-by-point comparison of comparable features emphasises the morphological similarities within this group, accentuates dissimilarities between them, and highlights the major differences between them and other fossil cysts having a similar tabulation formula. Extant cysts with a comparable tabulation are unknown.

KEYWORDS:

• Dinoflagellate
• tabulation patterns
• morphology

Acknowledgements

Discussions and time at the microscope with Bill Evitt and Lew Stover during the course of many years contributed significantly to the interpretations in this paper. Robin Helby photographed the specimens of Microdinium ornatum, and provided the photomicrographs included on Plate 1.

Plate 1. Microdinium ornatum Cookson & Eisenack. Photomicrographs of Cookson & Eisenack's published specimens (re-photographed and provided by Robin Helby; scale bar (figure 12) for all figures = 25 µm. 1–5. Focus series through holotype (see Cookson & Eisenack 1960, pl. 2, figs 3, 4) in ventral view. Figures 1 and 2, ventral focus; figure 3, optical section; figures 4 and 5, dorsal focus. (?)Upper Albian to Cenomanian, Perth Basin, Western Australia. 6–9. Focus series through a specimen in ventral view (previously illustrated in Cookson & Eisenack 1971, pl. 7, fig. 7). High (figure 6) and slightly lower (figure 7) focus levels of ventral surface; optical section (figure 8) and dorsal focus (figure 9). Cretaceous (undiff.), Eucla Basin, Western Australia. 10–12. Three focus levels of a specimen in dorsal view (previously illustrated in Cookson & Eisenack 1971, pl. 7, figs. 8, 9). Figure 10, ventral focus; figure 11, ventral focus at slightly higher level than figure 10; figure 12, dorsal focus. Cretaceous (undiff.), Eucla Basin, Western Australia.

Plate 2. Scanning electron photomicrographs of three undescribed species of Cladopyxidium. All specimens are Maastrichtian in age, and are from the Netherlands. Scale bars: figures 1–7, 9 = 10 µm; figure 8 = 5 µm. 1–6. Cladopyxidium sp. A. 1, ventral orientation showing mid-ventral plates and large posterior sulcal. Albert Canal. 2, right lateral orientation; note anterior intercalaries above precingular plates. Albert Canal. 3, right lateral orientation showing large anterior intercalaries. ENCI Quarry. 4, oblique apical-left lateral orientation showing large second precingular plate and subcircular archeopyle; ENCI Quarry. 5, apical orientation (ventral surface towards top of photomicrograph) showing four anterior intercalaries, elongate 1′ and 4′, and operculum consisting of 2′ and 3′ (and possibly a preapical plate). Albert Canal. 6, longitudinal section through specimen showing single wall layer penetrated by rather large pores (figures 1–5 show pores on outer surface). Albert Canal. 6. 7, 8. Cladopyxidium sp. B. 7, oblique apical orientation of specimen with operculum in place; figure 8, detail of operculum with specimen rotated counterclockwise so that ventral surface is at 12 o'clock. Although details of the tabulation are obscured by complications in the outer wall, numerous similarities in the pattern to that of Cladopyxidium sp. A are obvious. For example, compare anterior intercalary plates and details of the operculum to figure 5. Albert Canal. 9, Cladopyxidium velatum Below 1987. Extreme example of complications in outer wall development in a specimen in ventral orientation. Compare with figure 1: note similarities in posterior sulcal, midventral, and first and fourth apical plates. ENCI Quarry.

Plate 3. Light photomicrographs of Cladopyxidium sp. A, taken under Nomarski interference contrast. All specimens are Maastrichtian in age, and are from the Netherlands. Scale bar (see figure 1) = 10 µm for all figures. 1–3. Focus series through specimen in apical view (sulcus towards top). Figure 1, apical focus showing subcircular archeopyle (operculum missing) and anterior intercalary plates; figure 2, optical section; figure 3, antapical focus. Note relative sizes of 1″″ and 1p; suture separating them runs from base of ps to base of 3′′′. Curfs Quarry. 4–6. Focus series through specimen in dorsal view. Figure 4, dorsal focus; figure 5, optical section; figure 6, ventral focus. Curfs Quarry. 7, 8. Ventral focus (figure 7) and optical section (figure 8) of specimen in ventral view. Figure 7, note 1′ and 4′; figure 8, note pores penetrating entire thickness of autophragm. Albert Canal. 9. Specimen in ventral view, ventral focus, showing midventral tabulation. ENCI Quarry.

Plate 4. 1–7. Scanning electron photomicrographs of Histiocysta sp. A, from the Lower Eocene (Ypresian) Nanjemoy Formation, Popes Creek, Maryland. Scale bars: figures 1–6 = 10 µm; figure 7 = 5 µm. Figure 1, Left latero-ventral view; figure 2, oblique left lateral view of hypocyst showing relationships of 1‴, 2‴, 3‴, 1p and ps plates; figure 3, oblique dorsal view of hypocyst, centred on third postcingular plate; figure 4, oblique right lateral view of hypocyst; figure 5, apical view showing apical archeopyle and operculum remaining attached along isthmus formed by first and fourth apicals (note anterior intercalaries on operculum); figure 6, apical view with operculum in place; figure 7, close-up of wall showing thicker, smooth autophragm, and ectophragm supported by rod-like elements. 8, 9. Scanning electron photomicrographs of Cladopyxidium sp. B, ENCI Quarry, Maastrichtian, the Netherlands. Scale bar: figure 8 = 5 µm; figure 9 = 10 µm. Specimen in oblique apical view; figure 8 is a detail of the opercular region of figure 9. Note similarities to specimens illustrated in Plate 2, figures 5, 7, 8. Although the specimen appears to have two wall layers (aka the ‘double’ ring around the operculum), only an autophragm is believed to be present.

Plate 5. Light photomicrographs of Histiocysta sp. A, from the Lower Eocene (Ypresian) Nanjemoy Formation, Popes Creek, Maryland (bright field). 1–3. Focus series of specimen in dorsal view; scale bar = 20 µm. Figure 1, dorsal focus; figure 2, optical section; figure 3, ventral focus (see Plate 9, figure 2 for a detail of the mid-ventral region of this specimen). 4–6. Several focus levels of a specimen in antapical view; scale bar = 20 µm. Figure 4, antapical focus showing relative sizes and positions of 1″″ and 1p; figure 5, optical section; figure 6, apical focus with operculum in place. 7. Detail of apical tabulation of specimen in figure 6; scale bar = 10 µm. Sulcal region is located towards bottom of photomicrograph. 8, 9. Cladopyxidium velatum Below 1987 from the Albert Canal, the Netherlands, Maastrichtian (Nomarski interference contrast). High focus (figure 8) and optical section (figure 9) of a specimen in an unknown orientation, possibly dorsal; scale bar = 20 µm. Compare with scanning electron photomicrograph of the same species in Plate 2, figure 9.

Plate 6. Light photomicrographs of two undescribed species of Histiocysta, taken using Nomarski interference contrast. 1, 2. Histiocysta sp. B; scale bar = 20 µm. Two focus levels of specimen in right lateral view. Compare with scanning electron photomicrographs of the same species in Plate 7, figures 1–5. Figure 1, right lateral focus (note accessory ridges within plates); figure 2, optical section. Navesink Formation, Maastrichtian, Atlantic Highlands, New Jersey. 3–7. Histiocysta sp. C; focus series through specimen in apical view; scale bars: figures 3, 4, 6, 7 = 25 µm, figure 5 = 20 µm. Figure 3, apical focus; figure 4, somewhat lower focus level of apical surface; figure 5, detail of figure 4; figure 6, optical section; figure 7, antapical focus. Note accessory ridges, somewhat more complex than those on specimen in figures. 1, 2. Rupel Clay, Rupelian (Early Oligocene), Boom, Belgium. 8, 9. Histiocysta sp. C; scale bar = 25 µm. Ventral (figure 8) and dorsal (figure 9) focus levels of specimen in ventral view. Rupel Clay, Rupelian (Early Oligocene), Boom, Belgium.

Plate 7. 1–9. Scanning electron photomicrographs of two undescribed species of Histiocysta, from the Maastrichtian Navesink Formation, Atlantic Highlands, New Jersey. Scale bars: figures 1–4, 6–9 = 10 µm; figure 5 = 5 µm. 1–5. Histiocysta sp. B. Figure 1, ventral epicystal tabulation; figure 2, detail of apical region of specimen in figure 1; figure 3, dorsal surface; figure 4, oblique ventral surface of another specimen; figure 5, detail of midventral region of specimen in figure 4. 6–9. Histiocysta sp. C. Figure 6, ventral surface; figure 7, oblique view of ventral hypocyst showing relationships of ps, 1‴, 6‴, 1p, and 1″″; figure 8, left lateral surface; figure 9, apical surface of specimen with operculum missing (note two wall layers, autophragm and ectophragm, and intermediate supporting structures).

Plate 8. 1, 2. Apical tabulation in Histiocysta sp. B from the Navesink Formation, Maastrichtian, Atlantic Highlands, New Jersey. Note elongate first and fourth apicals, and small preapical between second and third apicals; four anterior intercalaries are present. Figure 1, detail of apical plates; scale bar = 5 µm; scanning electron photomicrograph provided by F.E. May. Figure 2, scanning electron photomicrograph of another specimen in apical orientation; scale bar = 10 µm. In figure 2, small seventh precingular plate can be seen at posterior margin of 4′ and to the lower right of 6″.

Plate 9. Comparison of midventral tabulation in some fossil representatives of the Order Gonyaulacales. Figures 1 and 2 are members of the ‘microdinoid’ group discussed in this paper, and are members of the Family Cladopyxiaceae (Suborder Cladopyxiineae) which have the partiform hypocystal configuration. Figures 3, 4 and 6 are members of the Family Gonyaulacaceae (Suborder Gonyaulacineae) which have the sexiform configuration. Figure 5 is a member of the Family Goniodomaceae (Suborder Goniodomineae) which has the quinqueform configuration. The microdinioid pattern is nearly identical topologically to the sexiform and quinqueform patterns, except for the relative position of the upper margin of the posterior sulcal plate with respect to the plates bordering the left side of the sulcus. In the partiform microdinioids, the contact of ps with two sulcals (probably ls and rs) abuts the first postcingular plate (the latitudinal position of this line of contact is indicated by an arrow in each photomicrograph), and ps thus contacts 1‴. In contrast, for most other gonyaulacaleans for which sulcal tabulation is well developed, this line of contact abuts the posterior intercalary plate, preventing contact between ps and 1‴. Note also that in the sexiform and partiform configurations, the antapical plate (1″″) contacts six plates including 6‴ (best seen in figures 4 and 6), while in the quinqueform configuration (figure 5) the antapical contacts only five plates, with no contact with 6‴. 1. Histiocysta sp. B from the Maastrichtian Navesink Formation, Atlantic Highlands, New Jersey; ventral orientation (scanning electron photomicrograph provided by F.E. May); scale bar = 5 µm. 2. Histiocysta sp. A from the Ypresian (Early Eocene) Nanjemoy Formation, Popes Creek, Maryland; dorsal view of ventral surface; Nomarski interference contrast (same specimen as in Plate 5, figures 1–3; scale bar = 10 µm. 3, 4. Leptodinium mirabile Klement 1960 emend. Sarjeant 1984; scanning electron photomicrographs of two specimens from Amber Bay, Alaska, Late Jurassic. Scale bars: figure 3 = 50 µm; figure 4 = 25 µm. 5. Biconidinium longissimum Islam 1983 from the Ypresian (Early Eocene) Nanjemoy Formation, Popes Creek, Maryland; ventral orientation highlighting hypocystal tabulation. Scanning electron photomicrograph; scale bar = 10 µm. 6. Cribroperidinium sp. from the Maastrichtian of the Netherlands, Albert Canal; ventral orientation. Scanning electron photomicrograph; scale bar = 25 µm.

Disclosure statement

No potential conflict of interest was reported by the author.

PLATES

Illustrated specimens were collected from several localities. Type material of Microdinium ornatum previously illustrated by Cookson & Eisenack (1960, 1971) and shown in Plate 1 herein are stored in the Museum of Natural History, Victoria, Australia (Plate 1, figures 1–5) and in the Palynological Collection of the Geological Survey of Western Australia (Plate 1, figures 6–12). Figured specimens of Histiocysta and Cladopyxidium were collected from six localities: (1) along the Albert Canal, and (2) in the Curfs Quarry and (3) ENCI Quarry, the Netherlands; (4) in a quarry near Boom, Belgium; (5) in outcrops along the Potomac River at Popes Creek, Maryland (described in Goodman 1979); and (6) in outcrops at Atlantic Highlands, New Jersey (described in May 1980).

Additional information

Notes on contributors

David K. Goodman

DAVID GOODMAN is president of the Irf Group, Inc., an international stratigraphic consultancy based in Anchorage, Alaska, that he established in 1999 (Gordon Wood was a senior scientist in the group from its start). Dave earned his BS and MS degrees in geology from Virginia Polytechnic Institute and State University, and his PhD from Stanford University working under Bill Evitt. His primary research interests are Upper Cretaceous and Paleogene dinoflagellates and their application to sequence biostratigraphy. He was a stratigrapher at Exxon Production Research Company in Houston from 1978 to 1983, and at several Arco affiliates in Dallas, Midland (Texas) and Anchorage from 1983 until he retired from Arco in 1999. Dave was a long-time Managing Editor for The Palynological Society, and editor of the journal Palynology from 1987 to 2000. He lives in Alaska and fishes throughout North America. On a clear day from his office (750 ft elevation) he can see 140 miles north to Denali (20,310 ft), and 130 miles southwest to the Iliamna Volcano (10,016 ft)…when not asleep at the scope, tying steelhead flies, or playing with sharp knives.