Archaeomonas kreyenhagenensis Rampi, 1969

Archaeomonas kreyenhagenensis Rampi, 1969

Fig. 8I, J View Fig .

Material.—Numerous specimens encountered on each SEM stub from Borek Nowy 5, Futoma 5 (DMF stubs 352-1k, 352-1l), Łubno 4, Oligocene of southeastern Poland.

Description.—Stomatocysts slightly ovate in lateral view ( Fig. 8J View Fig ) and spherical in anterior or posterior orientation, 6.0–8.6 µm in diameter. Anterior ends slightly and gradually attenuated, but no distinct collar is apparent. Visible part of pores obconical ( Fig. 8I View Fig ), 0.7–0.8 µm in basal diameter, widening towards cyst external surface to 1.5–2.2 µm in diameter. Cysts walls smooth.

Remark s.—Overall outline of the cysts, specifically wide and gently attenuating anterior poles, meets the species delineation. The bi-conical structure of the pores visible in LM cannot be readily observed using SEM. However, the obconical area above the narrowest part of the pore, the perforation of the cyst wall, was repeatedly observed. Californian stomatocysts ( Rampi 1969) were also slightly larger than our cysts: 9.5 µm vs. 6–8.5 µm in diameter, respectively.

Stratigraphic and geographic range.—Upper Cretaceous of the Subantarctic Southwest Pacific ( Perch-Nielsen 1975), Eocene of the Kreyenhagen Formation, California ( USA; Rampi 1969), Upper Eocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978), and Rupelian (lower Oligocene) of southeastern Poland (this study).

Archaeomonas cf. mamillosa Tynan, 1960

Fig. 9A View Fig .

Material.—Several specimens encountered on each SEM stub from Futoma 5 ( DMF stub 352- 1m), Łubno 2, Oligocene of southeastern Poland.

Description.—Stomatocysts spherical, 4.5–5.6 µm in diameter with smooth surface ( Fig. 9A View Fig ). Regular pores 0.4– 0.6 µm in diameter, surrounded by low collar in form of rounded marginal rim, 1.0–1.3 µm in diameter.

Remarks.—In most of the characters except cell size, our specimens are similar to A. mamillosa . However, those cysts are nearly twice as large as our specimens. The extant freshwater Stomatocyst 51 (Duff & Smol in Duff et al., 1995), are similar in size but have larger pores.

Archaeomonas semplicia Rampi, 1969

Fig. 9B View Fig .

Material.—Several specimens found on each SEM stub from Borek Nowy Kawalec ( DMF stub 349- 2g), Futoma 5, Oligocene of southeastern Poland.

Description.—Stomatocysts slightly oblate or spherical, depending on cyst orientation, 3.6–7.1 µm wide and 4.1– 7.5 µm long ( Fig. 9B View Fig ). Cyst wall surface smooth. Distinct collar clearly offset from wall surface. Collar conical, up to 0.7 µm high (may depend on preservation) and 1.3–2.7 µm in basal diameter, depending on cyst size.

Remarks.—The size range of our specimens is smaller than the 7–8 µm diameter given by earlier work ( Rampi 1969). As well, the collar of our stomatocysts appears proportionally wider with respect to the cyst diameter than those illustrated by Rampi (1969) and Deflandre and Deflandre-Rigaud 1969). Similar species with smooth wall surfaces are A. colligera Hajós, 1968 , and to a lesser extent A. pseudocompressa Hajós, 1968 . Archaeomonas colligera is similar to our specimens in collar morphology but those cysts are ellipsoidal and larger while A. pseudocompressa is also larger with cylindrical, not conical collars.

Stratigraphic and geographic range.—Upper Cretaceous of the Moreno Formation, California ( USA; Rampi 1940), Upper Cretaceous of the Subantarctic Southwest Pacific ( Perch-Nielsen 1975), Eocene of the Kreyenhagen Formation, California ( USA; Rampi 1969), Upper Eocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978), and Rupelian (lower Oligocene) of southeastern Poland (this study).

Archaeomonas sphaerica Deflandre, 1932a

Fig. 9C View Fig .

Material.—Numerous specimens found on each SEM stub from Futoma 4 ( DMF stub 349-17h), 5, 14, 16, Hermanowa 27, Łubno 3, Oligocene of southeastern Poland.

Description.—Stomatocysts spherical with smooth external walls ( Fig. 9C View Fig ). Two size-classes of specimens: 5.6–6.5 µm and 10–11.5 µm in diameter. Collar absent. Regular pores 0.8–1.3 µm and 1.1–1.7 µm in diameter in smaller and larger cysts, respectively. Pores in both size-classes of cyst descend sharply, directly, and nearly unchanged in diameter through cyst wall into its interior.

Remarks.—Specimens attributed to this species by Deflandre and Deflandre-Rigaud (1969) encompass a somewhat greater range of sizes (11–12 µm in diameter) than in the original description. The images obtained using SEM clearly illustrate the lack of a collar and the regular form of the pores. Although some of our specimens exceed the cell size range of the original delineation for A. sphaerica , their pore morphology is consistently similar, thus we attribute all our specimens to this species. In contrast, among the smooth-surface spherical stomatocysts with no collar and regular pores found in the freshwater environment, Duff et al. (1995) differentiate three separate stomatocysts types: Stomatocysts 1, 9, 15 Duff et al., 1995. Diameters of these cysts range from ≤ 5.9 µm, 6.0–8.9 µm, and ≥ 9.0 µm in diameter, respectively. Strictly adhering to those size criteria, our specimens span all three stomatocyst types. See also our closing remarks at the end of smooth-walled stomatocysts section.

Stratigraphic and geographic range.—Paleocene/Eocene boundary of Fuur Island, North Jutland ( Denmark; Deflandre 1932a), Rupelian (lower Oligocene) of southeastern Poland (this study), Tortonian (Miocene) of Hungary ( Hajós 1968), and Miocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978).

Archaeomonas aff. sphaerica Deflandre, 1932a

Fig. 9D View Fig .

Material.—Numerous specimens found on each SEM stub from Futoma 4, 5, 17, Łubno 4 ( DMF stub 333-18c), Oligocene of southeastern Poland.

Description.—Stomatocysts with outline varying from slightly to more distinctly oblate, although difference between cyst width and length varies only between 0.4–1.6 µm; from 5.2–10.9 µm in short to 6.2–12.6 µm in long axis ( Fig. 9D View Fig ). Regular pores 0.6–0.9 µm in inner and 0.9–1.5 µm in outer diameter in best preserved and oriented specimens. Remarks.—We are not aware of a marine archaeomonad species with the characteristics of our specimens, particularly given the variation in the cyst outline, with individuals grading from slightly to clearly oblate. The common character of our specimens is a regular pore, similar to those in our specimens of A. sphaerica . Among the freshwater stomatocyst types with similar overall morphology of the cystbody, all have more elaborate pore structures and collars. See also our closing remarks at the end of smooth-walled stomatocysts section.

Archaeomonas tubulata Deflandre, 1938 Fig. 9E View Fig .

Material.— Only one specimen from Futoma 5 ( DMF stub 352-1n), Oligocene of southeastern Poland .

Description.—One slightly oval stomatocyst found, 8.3 µm wide and 9.4 µm long. Cyst wall surface smooth. Distinct collar clearly offset from wall surface. Collar tubular, up to 2.0 µm in height, may be longer as it appears broken Fig. 9E View Fig 1 View Fig ). Collar relatively wide, cylindrical, 3.1–3.4 µm in basal diameter. Pore 1.3 µm in diameter surrounded by narrow flat planar annulus ( Fig. 9E View Fig 2).

Remarks.—Our specimen is larger than in the original description (5.9 µm in diameter calculated from an image shown by Deflandre 1938), but A. tubulata is the only species known to us that possesses such a long, straight tubular collar. Perch-Nielsen (1978) illustrates a specimen with a relatively long collar but attributes it to A. semplicia .

Stratigraphic and geographic range.—Rupelian (lower Oligocene) of southeastern Poland (this study), and Miocene of the Marmorito diatomites ( Italy; Deflandre 1938; Deflandre and Deflandre-Rigaud 1969).

Other genera