Archaeomonas cf. reticulata Hajós, 1968

Archaeomonas cf. reticulata Hajós, 1968

Fig. 5H View Fig .

Material.—Numerous specimens found on each SEM stub from Futoma 5 (DMF stub 352-1d), 17, Oligocene of southeastern Poland.

Description.—Stomatocysts spherical, 7.0–8.3 µm in diameter. Pores 0.6–0.9 µm in diameter. Short conical collars end in sharp marginal rims surrounding concave pore ( Fig. 5H View Fig ). Wall ornamentation consists of net of variable polygons, most frequent are tetra- and pentagons, commonly 6–7 in 10 µm, but entire range is 6–15 in 10 µm. Some polygon ridges terminate on collar sides. Conulae up to 1.0 µm long at junction of ridges.

Remarks.—Several specimens found demonstrate general similarity to A. reticulata discussed above but carry a finer net of polygons. No intermediate specimens were found. The Late Miocene to Pliocene Stomatocyst 26 Kato, 2019, has similar reticulation, but their pores and collars are unknown due to cyst orientation.

Archaeomonas cf. speciosa Deflandre, 1932a

Fig. 5I View Fig .

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

Description.—One stomatocyst found is 8.6–8.8 µm in diameter ( Fig. 5I View Fig ). Cyst wall ornamented with low reticulum and regular, polygonal lacunae, 2.5–3.0 lacunae in 10 µm. Most polygons 5- to 8-sided. Reticulum sides smooth, wide, and up to 0.6 µm high. Small nodules present in junctions of polygon sides. Pore and collar not observed.

Remarks.—The size and regular ornamentation or our cyst is most similar to the holotype of A. speciosa shown by Deflandre (1932a: fig. 7) which was enlarged in Deflandre and Deflandre-Rigaud (1969). A specimen named “? Litheusphaerella frenguellii Defl. ” in Hajós (1968) may belong to A. speciosa as well, as suggested by Deflandre and Deflandre-Rigaud (1969). Stomatocyst 242 Duff & Smol, 1995, reported in Duff et al. (1995) from the freshwater environment is also similar but are about half the size of A. speciosa and carry rounded rather than polygonal lacunae. Because the orientation of our specimen does not reveal the pore-collar structure, we consider this identification to be tentative. A. speciosa is known from Maryland and California ( USA).

Archaeomonas stomatocysts with spines/nodules

Archaeomonas americana Rampi, 1969

Fig. 5J View Fig .

Material.—Numerous specimens encountered on SEM stub Futoma 5 ( DMF stub 352-1f), Oligocene of southeastern Poland.

Description.—Cysts spherical, 6.0–7.8 µm in diameter. Pores 0.8–0.9 µm in diameter, surrounded by conical collar 1.6–2.3 µm in basal diameter ( Fig. 5J View Fig 1 View Fig ). Collar topped by flattened rim surrounding a concave pore ( Fig. 5J View Fig 2). Cyst wall surface features sparse, short and stout conulae, generally 3–4 in 10 µm.

Remarks.—Our specimens are either slightly smaller or at the lower end of the stomatocyst size range for the species. The somewhat similar A. cylindropora Deflandre, 1932a , and A. manginii Deflandre, 1932a , differ from our specimens in their collars being cylindrical, both externally and internally and either sparser or denser spines.

Stratigraphic and geographic name.—Eocene of the Subantarctic Southwest Pacific ( Perch-Nielsen 1975), Eocene of the Kreyenhagen Formation, California ( USA; Rampi 1969), and Rupelian (lower Oligocene) of southeastern Poland (this study).

Archaeomonas anterioconica Kaczmarska sp. nov. Fig. 6A–C View Fig .

PhycoBank ID: http://phycobank.org/105038.

Etymology: Refers to conical shape of the anterior pole of the cell.

Holotype: DMF SEM stub 333-10, as preparation KRAM A-32, sample Łubno 4 ( Fig. 6A View Fig , SEM image of stomatocyst in lateral view).

Type locality: Łubno, Poland.

Type horizon: Futoma Diatomite Member, Rupelian, lower Oligocene.

Material.—Numerous specimens encountered on each SEM stub from Borek Nowy 5A ( DMF stub 333-4), 12, Kawalec, Brzezówka 32, Hermanowa 27 ( DMF stub 342-14), Łubno 4 ( DMF stub 333-10 as KRAM A-32), Oligocene of southeastern Poland.

Diagnosis.—Cysts subspherical with conical and spineless anterior pole.

Description.—Stomatocysts subspherical to ovate with conical anterior pole, 3.0–8.6 µm in diameter. Pores 0.4–0.7 µm in diameter surrounded by conical collar of varying height, 1.1–2.1 µm in diameter and up to 1.1 µm high ( Fig. 6A, B View Fig ). Collar topped by smooth, flat rim ( Fig. 6C View Fig ). Spines irregularly dispersed over most of the cyst surface (0.6–2.3 µm apart), up to 2 µm long near apical pole ( Fig. 6A View Fig ), and about a third of the length at posterior pole, in best preserved specimens ( Fig. 6B View Fig ). A spineless area surrounds collar. Ring of spines pointing towards collar borders area devoid of spines and separate it from spinose part of wall.

Remarks.—This is quite a distinct cyst, yet we could not find such specimens in any available report. Although the general distribution of broken spines is reminiscent of A. manginii , it differs from it by having a conical anterior pole and spineless area surrounding the collar. Stomatocyst 215 ( Duff et al. 1995) is one of the few forms with a similar spineless circum-collar area and they overlap in size with our specimens, but Stomatocyst 215 is spherical, and its collar-pore system is different. Stomatocysts that are morphologically most similar in terms of outline and collar structure are the right-hand SEM images of two cysts shown in Deflandre and Deflandre-Rigaud (1969), named A. orbicularis Deflandre, 1933 . They however differ in the structure of spines (ours are not elongated at the base), and do not conform to the drawing of the holotype in Deflandre (1933), which lacks the spineless anterior seen on their SEM images.

Stratigraphic and geographic range.—Rupelian (lower Oligocene) of southeastern Poland (this study).