Archaeomonas japonica Deflandre, 1933
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publication ID |
https://doi.org/10.4202/app.01218.2024 |
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persistent identifier |
https://treatment.plazi.org/id/390C4800-5511-BF17-FF7C-B1AEAAE3FB7A |
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treatment provided by |
Felipe |
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scientific name |
Archaeomonas japonica Deflandre, 1933 |
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Archaeomonas japonica Deflandre, 1933
Fig. 6D View Fig .
Material.—Numerous specimens encountered on each SEM stub from Borek Nowy 12, Futoma 14, Łubno 4 (DMF stub 333-10b), Oligocene of southeastern Poland.
Description.—Stomatocysts spherical, 8.0–10.4 µm in diameter. Pores surrounded by cylindrical collar furnished with an uneven rim, collar 1.0 µm high and approximately 2.1 µm in basal diameter ( Fig. 6D View Fig ). Collar height approximately equal to length of robust conulae. Conulae stout, dispersed fairly regularly, up to 1.8 µm long, separated from each other by up to 2 µm. Usually 4–5 bases of conulae visible across cyst equator in lateral view.
Remarks.—Our specimens are somewhat larger in diameter than those described by Deflandre (1933; 5.8–6 µm). The species has also been reported by Rampi (1969) and Perch-Nielsen 1975, 1978), but neither provide metrics. Therefore, our comparisons are based on measurements estimated from their images. Those cyst sizes align our specimens better with A. oamaruensis Deflandre, 1933 , and A. cf. japonica in Perch-Nielsen (1975) than with A. japonica . However, the relative proportion of spines and collar height in our specimens meet the criteria for A. japonica , while less so for A. oamaruensis ( Deflandre 1933; Perch-Nielsen 1978), which, in addition, should have a spiny collar. A. oamaruensis is reported from New Zealand and the Vøring Plateau of the Norwegian Sea, thus both species were present in Southern and Northern Hemisphere locations of an age similar to our specimens.
Stratigraphic and geographic range.—Eocene of the Kreyenhagen Formation, California ( USA; Rampi 1969), Upper Eocene of the Vøring Plateau of the Norwegian Sea ( Perch-Nielsen 1978), Rupelian (lower Oligocene) of southeastern Poland (this study), upper Oligocene to Miocene of the Subantarctic Southwest Pacific ( Perch-Nielsen 1975), and Miocene near Akashiri, Hokkaido ( Japan; Deflandre 1933).
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