Archaeomonas helminthophora Deflandre, 1933

Archaeomonas helminthophora Deflandre, 1933

Fig. 4A, B View Fig .

Material.— At least 10 specimens encountered on both SEM stubs from Borek Nowy Kawalec ( DMF stub 349-2e), Futoma 17 ( DMF stub 349-12a), Oligocene of southeastern Poland .

Description.—Stomatocysts spherical, 6.6–7.1 µm with pores 0.6 µm in diameter. Pores surrounded by low, cylindrical to obconical collars, up to 2.6 µm in diameter ( Fig. 4A View Fig ). Cyst walls adorned with high, narrow ridges of varied length and orientation, both straight and slightly bowed ( Fig. 4B View Fig ) but generally equal to or longer than collar diameter, as shown on the species holotype. As per diagnosis, number of ridges varies greatly. Maximal height of undamaged ridge recovered was 1.6 µm.

Stratigraphic and geographic range.—Upper Cretaceous of the Moreno Formation, California ( USA; Cornell 1972), Rupelian (lower Oligocene) of southeastern Poland (this study), Miocene of Maryland ( USA; Deflandre 1933; Tynan 1960), Tortonian (Miocene) of Hungary ( Hajós 1968; Deflandre and Deflandre-Rigaud 1969), and Miocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978).

Archaeomonas heteroptera Deflandre, 1932c

Fig. 4C–E View Fig .

Material.—Numerous specimens encountered on each SEM stub from Borek Nowy 12 Kawalec, Futoma 5, 17 ( DMF stub 349-12b), Łubno 3 ( DMF stub 342-10a), 4 ( DMF stub 333-10a), Oligocene of southeastern Poland.

Description.—Stomatocysts appear spherical, oblate, or ellipsoidal, depending on cell orientation; 6.0–8.8 µm and 6.2– 9.5 µm in width and length, respectively. Pores 0.6–1.2 µm in diameter, surrounded by cylindrical collar ( Fig. 4C View Fig ) with relatively thick flat rim ( Fig. 4D View Fig ). Collars 1.3–2.7 µm in diameter including rim and up to 0.8 µm high in best preserved specimens. Cyst walls adorned with tall, fin-like longitudinal ridges. Several longest ridges may run nearly entire length of cell ( Fig. 4C View Fig ), while shorter ridges may be inserted between longer ones. Number and length of ridges varies greatly ( Fig. 4E View Fig ). Maximal height of ridge recovered was 1.5 µm. There may be 2–8 such ridges in 10 µm. State of specimen preservation varied, some showing only bases of ridges ( Fig. 4D View Fig ). In extreme cases, although generally spherical, overall cyst outline appeared angular. In such cysts, the pores have acute edges, flush with surrounding flattened cell surface and no collar.

Remarks.—In addition to Deflandre (1932a, c) this variable, yet distinct species has been reported by several researchers, as summarised and illustrated in Deflandre and Deflandre-Rigaud (1969), but also later by Perch-Nielsen (1978), both including SEM images.

Stratigraphic and geographic range.—Upper Cretaceous of the Moreno Formation, California ( USA; Rampi 1940; Cornell 1972), Upper Cretaceous of the South Pacific Ocean ( Hajós and Stradner 1975), Paleocene/Eocene boundary of Fuur Island, North Jutland ( Denmark; Deflandre and Deflandre-Rigaud 1969), Eocene of the Kreyenhagen Formation, California ( USA; Rampi 1969), Upper Eocene of the Subantarctic Southwest Pacific ( Perch-Nielsen 1975), Rupelian (lower Oligocene) of southeastern Poland (this study), Miocene of the Calvert Formation, Maryland ( USA; Tynan 1960), Miocene of Noto Peninsula ( Japan; Bachmann 1964), and Miocene of Limberg ( Austria; Stradner 1971).

Archaeomonas vermiculosa Deflandre, 1932a

Fig. 4F View Fig .

Material.—Several specimens encountered on SEM stub from Futoma 17 ( DMF stub 349-12c), Oligocene of southeastern Poland.

Description.—Cysts spherical, 6.6–9.2 µm in diameter. Walls densely covered with irregularly dispersed vermicular ribs of varied length, straight or slightly curved ( Fig. 4F View Fig ). Maximal height of ridge recovered was 0.6 µm. One cyst presenting pore shows a relatively small, regular opening, 0.6 µm in diameter. Collar subconical, up to 1.1 µm in diameter and approximately 0.5 µm in height.

Remarks.—The subconical collar, smaller and denser ridges distinguish our specimens from those of A. helminthophora ( Deflandre 1933) . Our specimens differ from that shown by Perch-Nielsen (1978) by having a less spinose character of the ribs and are slightly larger than all specimens mentioned above. The ribs on our specimens tend to be longer and more curved towards the posterior end of the cyst, in agreement with the illustration of the holotype.

Stratigraphic and geographic range.—Upper Cretaceous of the Moreno Formation, California ( USA; Rampi 1940; Cornell 1972), Paleocene/Eocene boundary of Fuur Island, North Jutland ( Denmark; Deflandre 1932a), Rupelian (lower Oligocene) of southeastern Poland (this study), Miocene of the Calvert Formation, Maryland ( USA; Tynan 1960), Miocene of Limberg ( Austria; Stradner 1971), and Miocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978).

Archaeomonas stomatocysts with reticule

Archaeomonas areolata Deflandre, 1933

Fig. 4G View Fig .

Material.—Numerous specimens encountered on each SEM stub from Futoma 4 ( DMF stub 349-17b), 5, 17, Oligocene of southeastern Poland.

Description.—Spherical specimens 7.7–9.3 µm in diameter. Pores 0.7–0.8 µm in diameter surrounded by thick, internally round, externally polygonal ring of a collar ( Fig. 4G View Fig ) slightly elevated above cell wall surface and connected to sides of neighbouring polygons, 1.7–2.4 µm in diameter. Cell walls covered by relatively large polygonal (mostly hexagonal) reticulum, 4–7 areolae in 10 µm, sometimes referred to as locunae. Small conulae (up to 0.4 µm high; Fig. 4G View Fig ) may emerge at junctions of some polygons, as in Deflandre’s (1933) holotype.

Remarks.—Following the original description, Tynan (1960) and Stradner (1971) provided images of specimens with a very low, simple cylindrical collar. Later, Perch-Nielsen (1978) showed specimens with a varying degree of wall structure erosion. Our specimens are most similar to her’s ( Perch-Nielsen 1978: pl. 1: 10), with relatively low walls of areolae and simplified collar. Although metrics for the specimens are not given, they generally agree with Deflandre’s and Tynan’s cyst sizes (6–7 µm) when calculated from their images ( Stradner 1971; Perch-Nielsen 1978). Areolae density of all their specimens is approximately 7–9 areolae in 10 µm, thus similar to ours. Specimens attributed to A. areolata , A. cf. areolata , A. cf. areolata var. 1, and A. cf. areolata var. 2 have been found in modern Antarctic waters associated with sea-ice ( Mitchell and Silver 1982; Buck and Garrison 1983; Riaux-Gobin and Stumm 2006). The most notable difference between these, our specimens, and fossil A. areolata sensu lato is the somewhat greater density of areolae ( 10–14 in 10 µm in the case of A. cf. areolata var. 1) and more variable cyst size and shape, in addition to the finer density wall areolae (6.6–10.0 in 10 µm) in the case of A. cf. areolata var. 2. However, taxonomic affinity to the modern specimens attributed to A. areolata requires careful comparison to Deflandre’s (1933) type material.

Stratigraphic and geographic range.—Rupelian (lower Oligocene) of southeastern Poland (this study), Miocene of the Calvert Formation, Maryland ( USA; Tynan 1960), Miocene of Limberg ( Austria; Stradner 1971), Miocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978), Miocene/Pliocene boundary of Hungary ( Deflandre 1933), and Miocene/Pliocene boundary of Atlantic section of Southern Ocean (Kato 2019). Recent reports from the Equatorial Pacific, North Pacific, and South Atlantic ( Mitchell and Silver 1982), the Weddell Sea ( Buck and Garrison 1983; Mitchell and Silver 1986), and Kita-no-seto Strait, Antarctica ( Takahashi et al. 1986).

Archaeomonas cf. areolata var. 1 Riaux-Gobin & Stumm, 2006

Fig. 4H–J View Fig .

Material.—Numerous specimens encountered on each SEM stub from Borek Nowy 5, 12B ( DMF stub 342-15a), Futoma 5, 17A ( DMF stub 349-1), Łubno 4 ( DMF stub 341- 13), Oligocene of southeastern Poland.

Description.—Cells spherical, 6.3–8.1 µm in diameter. External wall surface covered by regular lattice of mostly hexagonal, equally sized areolae, 11–15 in 10 µm ( Fig. 4H View Fig ). In well preserved specimens, blunt, bacculate spines emerge at junctions of wall between neighbouring polygons, up to 0.6 µm high ( Fig. 4I View Fig ). In still better-preserved specimens, small conulae may be visible in areolae centers ( Fig. 4J View Fig ). Pores 0.5–0.8 µm in diameter surrounded by low collar, 1.4–1.5 µm in diameter ( Fig. 4H View Fig ). Rim surrounding pores are circular internally but polygonal externally and connecting to sides of neighbouring polygons.

Remarks.—Among the areolate forms, this stomatocyst is the most common and widely distributed in our samples.

The morphologically most similar stomatocyst known is the modern Antarctic Archaeomonas cf. areolata var. 1 described by Riaux-Gobin and Stumm (2006). Ours and the specimens from Antarctica differ from A. areolata by having finer areolae. Cyst Type 3 and 4 VanLandingham, 1964, from Washington state ( USA) show a larger range of sizes and density of areolation and altogether are similar (but not identical) to forms reported from the humic Lake Gribsø

Nygaard 1956).

Archaeomonas asharya Samanta sp. nov.

Fig. 4K, L View Fig .

PhycoBank ID: http://phycobank.org/105037.

Etymology: Dedicated to my wife and son.

Holotype: DMF SEM stub 349-12, as preparation KRAM A-29, sample Futoma 17, intermediate fraction ( Fig. 4K View Fig , SEM image of stomatocyst in anterio-lateral view).

Type locality: Futoma, Poland.

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

Material.—Several specimens encountered on each SEM stub from Futoma 5, 17 ( DMF stub 349-12 as KRAM A-29), 17A ( DMF stub 333-5), Oligocene of southeastern Poland.

Diagnosis.—Cysts with conical collars and hexagonal lattice on external sides.

Description.—Stomatocysts spherical, 5.8–6.4 µm in diameter. Collars conical, topped with flat rounded rims, up to 0.8 µm high, up to 2.2 µm in basal diameter and 1.2 µm at rims. Pores regular, approximately 0.8 µm in diameter. Cyst walls including collar external sides covered with hexagonal lattice of regularly organised scabra, 29–34 hexagons in 10 µm ( Fig. 4K View Fig ). Lattice often organised into areas with parallel or fasciculate rows of areolae ( Fig. 4L View Fig ).

Remarks.—Our specimens are somewhat similar to freshwater Stomatocyst 178 Zeeb & Smol, 1993, illustrated in Duff et al. (1995) in the type of wall ornamentation, but our hexagons are coarser (29–34 vs. 40+ in 10 µm, as calculated from their images). Also, the pore-collar systems differ between the species. In Stomatocyst 178 the collar is cylindrical to obconical, while our specimens consistently have conical collars.

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

Archaeomonas ovoidea Deflandre, 1933 Figs. 4M View Fig , 5A View Fig .

Material.—Numerous specimens encountered on each SEM stub from Futoma 5, 16 ( DMF stub 349-15), Łubno 4 ( DMF stub 342-13 as B 40 0046308), Oligocene of southeastern Poland.

Description.—Stomatocysts ovate, 13.4–16.3 µm long and 9.8–12.1 µm wide ( Figs. 4M View Fig , 5A View Fig 1 View Fig ) with externally short “neck” grading into obconical collar surrounding pores, 1.8 µm in diameter. Collar rim carries short conulae that are also connected to wall ridges ( Fig. 5A View Fig 2). Collars 2.9–4.3 µm in apical diameter. Wall surface covered by polygonal network of irregular, low ridges carrying minute scabra or conulae mostly at ridge junctions and rims of collars, 2–7 ridges in 10 µm, most commonly only 3 in 10 µm.

Remarks.—This species is infrequently reported. In addition to the holotype, the species and a similar form ( A. cf. ovoidea ) have been found by Perch-Nielsen (1978). Perch- Nielsen’s specimens show more regularity in the network of ridges than described and shown on the holotype.

Stratigraphic and geographic range.—Rupelian (lower Oligocene) of southeastern Poland (this study), Middle Miocene of San Pedro, California ( USA; Deflandre 1933; Deflandre and Deflandre-Rigaud 1969), and Middle to Upper Miocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978).

Archaeomonas stomatocysts with reticule and spines

Archaeomonas aff. chiarugii Rampi, 1940

Fig. 5B View Fig .

Material.—Several specimens encountered on each SEM stub from Borek Nowy 5B ( DMF stub 342-18); Futoma 17, Oligocene of southeastern Poland.

Description.—Stomatocysts spherical, 4.8–7.2 µm in diameter. Collar and cyst external surface covered with a reticle of polygons of variable size, 11–30 ribs in 10 µm ( Fig. 5B View Fig ). Sides of polygons vary in thickness. Small spines and conulae most common on the thickest ridges. Pores 0.5–0.7 µm in diameter, surrounded by slightly conical collar with acute rim. Collars 0.7–1.3 µm in diameter.

Remarks.—Our specimens are somewhat similar to A. chiarugii in their fine reticular sculpturing of the walls. Otherwise, our specimens are smaller, their collars are less offset from the cyst body, and reticulation is less regular.

Archaeomonas hungarica Hajós, 1968

Fig. 5C–E View Fig .

Material.—Numerous specimens encountered on each SEM stub from Borek Nowy 5, 12B ( DMF stub 342-15b), Futoma 5 ( DMF stub 352-2a), 17 ( DMF stub 349-12d), Oligocene of southeastern Poland.

Description.—Cells spherical, 7.2–8.8 µm in diameter.Pores 0.6–0.9 µm in diameter and surrounded by short, slightly conical collar, ~0.6 µm high. Collar rim wide, 1.4–2.0 µm in diameter ( Fig. 5D View Fig ). In best preserved specimens collar bases connect with ribs covering cyst surface ( Fig. 5C, D View Fig ). Ribs form highly irregular network of polygons, 3–14 polygons in 10 µm. Some ribs taper off before reaching wall of closest opposite polygon ( Fig. 5C, E View Fig ). Conulae and spines may be present at junction of largest polygons or in lacunae of large polygons. Some conulae up to 1.6 µm in height.

Remarks.— Deflandre and Deflandre-Rigaud (1969) considered A. hungarica to be a synonym of Archaeomonas speciosa Deflandre, 1932a . Hajós’ differential diagnosis ( Hajós 1968) emphasizes the collar structure which she considered should be characteristically elevated above the cyst surface in A. speciosa . However, such collar elevation is not mentioned in the original description. It is only later shown by Tynan 1960). The original description of A. hungarica also emphasises the wall sculpturing. We concur that it is exceptionally varied and as in Hajós’ (1968) Tortonian material where among “numerous specimens studied there were no two identical ones”. This contrasts to regularly distributed polygons on the holotype and paratypes of A. speciosa ( Deflandre 1932a; Deflandre and Deflandre-Rigaud 1969, respectively).

Stratigraphic and geographic range.—Rupelian (lower Oligocene) of southeastern Poland (this study), and Tortonian (Miocene) of Hungary ( Hajós 1968).

Archaeomonas reticulata Hajós, 1968

Fig. 5F, G View Fig .

Material.—Several specimens encountered on each SEM stub from Borek Nowy 5, 12A ( DMF stub 342-9), Kawalec, Futoma 5 ( DMF stub 352-1c), 17, Łubno 4, Oligocene of southeastern Poland.

Description.—Stomatocysts spherical, 6.0–10.0 µm, pores 0.7–0. 8 µm in diameter. Low and conical collars end in rounded marginal rims. Wall ornamentation consists of net of large, fairly regular polygons, most frequent are tetra- and pentagons, commonly 4–5 in 10 µm, but the entire range is 2–7 in 10 µm. Polygons delineated by ridges. Ridges near collars terminate on collar sides ( Fig. 5F View Fig ). Robust conulae up to 1.0 µm long at junction of several polygons ( Fig. 5G View Fig ). Size of polygons render cyst outline somewhat angular ( Fig. 5F View Fig ).

Remarks.—This species has only been reported from the Torton of Hungary (as far as we can determine) where the specimens were somewhat larger (13–14 µm) than ours. Another species with polygonal cell walls, A. brevispina Rampi, 1948 , is of similar size but its collar is more strongly developed while spines are more delicate.

Stratigraphic and geographic range.—Rupelian (lower Oligocene) of southeastern Poland (this study), and Tortonian Miocene) of Hungary ( Hajós 1968).