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Pyxidinopsis psilata

Zonneveld, K.A.F. and Pospelova V. (2015). A determination key for modern dinoflagellate cysts. Palynology 39 (3), 387- 407.

 
dorsal view
Core: GeoB 7609-1, 26 cm
Location: Black Sea
photographs: Karin Zonneveld
cross section
ventral view

Field characteristics

Pyxidinopsis psilata Wall and Dale 1973

Field characteristics:
Spherical, oval, rhombic or cruciform cyst with a psilate, minutely punctate or finely scabrate wall surface. Tabulation is only indicated by a precingular archeopyle (paraPlate 2”).

Dimensions: spherical cyst: diameter: 37 to 52 µm; cruciform cyst: length 46 to 65 µm, width: 37 to 50 µm.
Motile affinity: Unknown.
Stratigraphic range: ?Holocene to Recent.

Comparison with other species:
This species might be characteristic for regions with fresh water input. In brackish environments its form becomes cruciform. However, all transitions between its rhomboid shape and its cruciform shape can occur. Its cell wall is much thinner than that of B. tepikiense and T. pellitum. It has no reticulation such as P. reticulatum. It has a characteristic precingular archeopyle with the loss of one single plate.
Geographic distribution based on :
Zonneveld et al., 2013. Atlas of modern dinoflagellate cyst distribution based on 2405 datapoints. Review of Palaeobotany and Palynology, v. 191, 1-197
Pyxidinopsis psilata can be considered as an euryhaline, temperal/sub-tropical to tropical species.
Distribution:
Pyxidinopsis psilata has a scattered distribution as it is observed in subtropical sediments off central western North America and along the western and eastern margins of the South Atlantic Ocean around 30°S, in the Black Sea and in the Marmara Sea. Although most recordings are from coastal sites, it is not restricted to coastal areas. Highest abundances (up to 11.7%) occur in shallow tropical sites of the Gulf of Mexico.

Environmental parameter range:
SST: 7.1 - 29.0°C (winter - summer), SSS: 12.7 - 37.8 (summer - winter), [P]: 0.1 - 0.8 μmol/l, [N]: 0.05 - 4.6 μmol/l, chlorophyll-a: 0.2 - 5.2 ml/l, bottom water [O2]: 0.8 - 6.6 ml/l.
Pyxidinopsis psilata has a euryhaline distribution with high relative abundances either with reduced salinities throughout the year or with high salinities.

Comparison with other records:
Apart from the records in the dataset of this Atlas, Pyxidinopsis psilata has been observed in coastal sites from the German Bight in the North Sea (Nehring, 1994) and in the Baltic Sea (Sangiorgi pers. comm. 2012).