Stiphrosphaeridium sobralii Rodr.-Amenábar, Alessandra Santos et Guerstein

Plant Fossil Names Registry Number: PFN003305

Act LSID: urn:lsid:plantfossilnames.org:act:3305

Authors: C. Rodríguez-Amenábar, A. Santos & R. Guerstein

Rank: species

Reference: Rodríguez-Amenábar, C., Santos, A. & Guerstein, R. (2024): A new Campanian dinoflagellate cyst from Antarctica: a biostratigraphic and paleoecological key species. – Publicación Electrónica de la Asociación Paleontológica Argentina 24(1): 199–216., link

Page of description: 207

Illustrations or figures: figs 3–7

Types

Original diagnosis/description

Processes deeply fibrous at their bases, expanding at the distal end like a trumpet, with open extremities and smooth distal margin, without fenestrated or reticulate distal terminations.

Description: Chorate cyst, having a spherical to subspherical body shape. The cyst wall (1.5–2 µm) comprises an endophragm and periphragm, which are closely appressed, except where the periphragm forms the processes. The periphragm, smooth to finely granulate, develops intratabular processes, one per paraplate. The processes arise from several proximal stems, which coalesce distally to form a single process, all of a similar length, giving the process a fibrous appearance. Tubiform processes broaden distally in a trumpet form. Processes widely expanded and open distally, with a smooth continuous edge. Processes usually show folds near the extremity and are flat-looking. The gonyaulacoid paratabulation (4´, 6´´, 0c, 6´´´, 1p, 1´´´´, 1ps, plus 0–4s) is reflected by the distribution of intratabular processes; paracingular and parasulcal processes are absent. The archaeopyle is apical, type (tĀ), with a zig-zag margin. The operculum is free (Figs. 3–7).

Etymology

In honour of José María Sobral, a patriotic naval officer and the first Argentine geologist who carried out research work in Antarctica during the forced overwintering at Cerro Nevado (=Snow Hill) Island in 1902. He was a member of the Swedish Antarctic Expedition (1901–1903) headed by Otto Nordenskjöld. Argentina's scientific research on the Antarctic continent began with Sobral.

Stratigraphy

Cretaceous, Upper Cretaceous, Campanian
The middle Campanian (members I, II, III of the Rabot Formation) and upper Campanian (Hamilton Point Member of the Snow Hill Island Formation). In upper Pliocene diamictites of the Hobbs Glacier Formation or Gage Formation, Stiphrosphaeridium sobralii is interpreted as reworked taxa.

Locality

Antarctica
Rabot Point and Ekelöf Point, Southeast James Ross Island.