Archaeomonas litheusphaerellamima Samanta, 2025

Archaeomonas litheusphaerellamima Samanta sp. nov.

Fig. 7H–J View Fig .

PhycoBank ID: http://phycobank.org/105040.

Etymology: From Latin mimus (actor, resembling others); due to superficial similarity to species from the genus Litheusphaerella .

Holotype: DMF SEM stub 333-10, as preparation KRAM A-34, sample Łubno 4 ( Fig. 7H View Fig , SEM image of stomatocyst in anterior-lateral view).

Type locality: Futoma, Poland.

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

Material.—Numerous specimens found on each SEM stub from Borek Nowy 5, Futoma 5 (DMF stub 352-2b), Łubno 4 (DMF stub 333-10 as KRAM A-34), Oligocene of southeastern Poland. Additionally several specimens on Canadian preparation (DMF stub 333-13) from Shell Oneida O-25 well (CGS D-3), Scotian Shelf, Canadian waters, lower Miocene.

Diagnosis.—Secondary collar adorned with bacculate and bifurcate spines, remaining cyst surface covered with solid, stout pointed spines in regular, hexagonal grid. Planar interannulus present.

Description.—Stomatocysts spherical, 7.3–9.1 µm in diameter, densely covered by regularly distributed solid, stout pointed spines ( Fig. 7H, I View Fig ). Undamaged spines 0.6–0.8 µm long, positioned nearly equidistantly, 9–20 in 10 µm in hexagonal grid. Regular pores 0.5–0.6 µm in diameter surrounded by complex collar system. Primary collar cylindrical, surrounded by flat planar interannulus, followed by ring of 9–18 columnar spines ( Fig. 7J View Fig ). Free ends of collar spines flat or bifurcated.

Remarks.—This distinct stomatocyst is superficially similar to Litheusphaerella spectabilis Deflandre, 1932c , in carrying regularly and equidistantly distributed spines. However, the spines in our species are stout, short, and pointed. Moreover, spines in our species lack a hollow center and the T-shaped apices which are characteristic of L. spectabilis . This can be seen on images shown by Perch-Nielsen (1978) and our own specimens presented below in the last section of the results. The collar-pore apparatus in our specimens is also different from that shown for L. spectabilis on SEM images of cells recovered from the type locality ( Deflandre and Deflandre-Rigaud 1969). Diagnostic characters described for the new species are stable. In addition to the Polish Rupelian diatomites, we found this species in the interval between 1575–1610 feet ( 480–491 m) below the seafloor in the Shell Oneida 0-25 well (GSC locality D-3; at 43° 14’ 57.36” N, 61° 33’ 36.49” W) taken near the Scotian Shelf edge, Atlantic coast of Canada (IK unpublished data; Fig. 7I View Fig ). These strata correspond to the Lower Miocene series ( Barss et al. 1979).

Stratigraphic and geographic range.—Rupelian (lower Oligocene) of southeastern Poland (this study), and Lower Miocene, Scotian Shelf (Atlantic coast of Canada; IK unpublished data).