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Pyxidinopsis reticulata

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

 
dorsal view
Sample: GeoB 12312
Location: Arabian Sea Makran Ridge
Age: modern
Photographs: Karin Zonneveld
cross section
ventral view
dorsal view
Sample: DP30PC 617 cm
Location: Gulf of Taranto
Age: Roman Warm Period
Photographs: Karin Zonneveld
cross section
lateral view 2

Field characteristics

Pyxidinopsis reticulata (McMinn et Sun 1994) Marret et de Vernal 1997

Field characteristics:
Spherical to subspherical cysts. Cell wall is covered by variable low muri which form an irregular nontabular, polygonal reticulum. Fields within the reticulum can be microgranulate to finely corrugate. Tabulation is only indicated by a precingular archeopyle (type P).

Dimensions: Cyst body diameter: 28 to 40 µm.
Motile affinity: Unknown.
Stratigraphic range: Lower Pliocene to Recent.

Comparison with other species:
The discriminating features of this cyst are its precingular archeopyle with the loss of one single plate and its wall structure. If you focus on the wall structure you see a reticulate pattern. The individual reticulations might be filled with additional ridges. The density of this pattern can vary from open reticulation to a very dense pattern. The height of the muri is variable. The rims of the reticulation is higher than that of the filling ridges. The cysts are quite robust and often the archeopyle is beautifully visible.

Geographic distribution

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 reticulata is a cosmopolitan species, which is not observed in the arctic north of the arctic front. Its relative abundances are higherin mesotrophic to eutrophic environments.
Distribution:
Pyxidinopsis reticulata is observed in all studied regions included in this Atlas exception for the Arabian Sea and the Arctic north of the arctic front. Abundances >50% (up to 84%) occur in the North Sea.

Environmental parameters:
SST: -2.0 - 28.8°C (autumn - spring). SSS: 17.2 - 39.4 (summer - autumn), [P]: 0.06 - 1.9 μmol/l, [N]: 0.04 - 26.5 μmol/l, chlorophyll-a: 0.05 - 13.6 ml/l, [O2]: 0.05 - 7.7 ml/l.
Generally SSS: > 30 throughout the year but in some cases SSS can be seasonally reduced. Pyxidinopsis reticulata almost exclusively occurs in mesotrophic and eutrophic environments.

Comparison with other records:
Pyxidinopsis reticulata is not registered from regions not covered by this Atlas. In sediment trap studies of the upwelling region off NW Africa slightly enhanced cyst production could be observed when Sahara dust input is high and when active upwelling occurs in the vicinity of the trap site (Zonneveld et al., 2010). In the arctic a slight positive correlation is present between its relative abundances and sea ice cover duration (de Vernal et al., 1998; Radi and de Vernal, 2008)