Abstract
ABSTRACTIn the southern high latitudes, dinoflagellate cysts are an important microfossil group for both biostratigraphic and palaeoenvironmental interpretations purposes. In light of this, the peridinioid dinoflagellate cyst Nucicla umbiliphora gen. et sp. nov. from the Antarctic margin is formally described. Nucicla is dorsoventrally compressed, has a rounded pentagonal outline in dorso-ventral view, an epicyst that is only half as high as the hypocyst, an unusual archaeopyle formed by the loss of the three anterior intercalary plates, and a posterior sulcal plate that is positioned at the antapex. The species N. umbiliphora is characterised by a scabrate cyst wall and possesses undulated and/or crenulated folds/ridges. It has been so far exclusively found in Quaternary sediments obtained from the East Antarctic continental shelf and the Ross Sea. Although the dinoflagellate producing this cyst is as yet unknown, its brown color and the lack of autofluorescence suggest that the motile cell is likely a heterotrophic Protoperidinium species. As such, N. umbiliphora might benefit from the phytoplankton blooms occurring close to the Antarctic margin after seasonal sea-ice retreat.
Highlights
The Oligocene to Quaternary sediments of the Southern Ocean and Antarctic margin had long been thought to contain no dinoflagellate cysts (McMinn 1995), several endemic and bipolar species have been discovered during the last two decades
The cysts of N. umbiliphora did not autofluoresce under fluorescence microscopy (Plate 1, figure 12)
For core ANTA02-AV43 all samples were taken above the interval 1.48–1.51 m below sea floor, which has an age of 9.7 § 5.3 ka based on 40Ar/39Ar dating (Del Carlo et al 2015)
Summary
The Oligocene to Quaternary sediments of the Southern Ocean and Antarctic margin had long been thought to contain no dinoflagellate cysts (McMinn 1995), several endemic and bipolar species have been discovered during the last two decades. They are important for both biostratigraphical purposes and reconstructing high-latitude climatic evolution (Bijl et al 2018; Marret & De Vernal 1997; Montresor et al 1999; Esper & Zonneveld 2002; Prebble et al 2013; Clowes et al 2016). This species has already been reported without formal description from four localities around Antarctica (Figure 1). These dinoflagellate cysts are included in N. umbiliphora. We add occurrences of this species in nine other East Antarctic marine sediment cores and surface sediments (Figure 1; Table 1)
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