radiolaria - rads_cenozoic - Heterosestrum sexispinatum rotundum

Heterosestrum sexispinatum rotundum

Classification: rads_cenozoic -> Coccodiscidae -> Heterosestrum -> Heterosestrum sexispinatum rotundum
Sister taxa: H. sexispinatum rotundum, H. sp.


Citation: Heterosestrum sexispinatum subsp. rotundum Clark & Campbell (1945)
Rank: species
Basionym: Heterosestrum sexispinatum rotundum
Taxonomic discussion: (Clark and Campbell) 1945, p.21, pl.3, fig. 9

Catalog entries: Heterosestrum sexispinatum rotundum

Original description: Subspecies having a phacoid shell of more or less rounded outline, the opposite broad faces being convex and the margin having 6 similar edges with 6 angles from which arise the stout, 3-bladed prismatic, solid gimletlike radial spines; these similar spines are long (about 0.6 to nearly the full diameter of the shell in length); outer concentric medullary shell subhexagonal (with sharper outline than in the innermost medullary shell); concentric innermost medullary shell more perfectly circular; the outer of these 2 medullary shells large (0.7 diameter of cortical shell), and the inner one smaller (0.39 cortical shell); numerous prismatic radial supporting beams between the outermost shells and additional to the 6 main radial beams formed by the inward extensions of the radial, projecting spines, which last are also continued to the innermost medullary shell; pores of nearly uniform size and similarly circular; framework a relatively delicate polygonal meshwork, from the nodes of which arise, in the phacoid shell, minute free nodal points and from which arise, in the medullary shells, the minor radial beams.




Biogeography and Palaeobiology

Similar species

Geographic distribution


Phylogenetic relations

Biostratigraphic distribution

Geological Range:
Last occurrence (top): within Paleogene Period (23.03-66.04Ma, top in Chattian stage). Data source: Lazarus et al. 2015 - "P age group"
First occurrence (base): within Paleogene Period (23.03-66.04Ma, base in Danian stage). Data source: Lazarus et al. 2015 - "P age group"

Plot of occurrence data:


Clark, B. L. & Campbell, A. S. (1945b). Radiolaria from the Kreyenhangen Formation near Los Banos, California. Geological Society of America, Memoir. 1-66. gs


Heterosestrum sexispinatum rotundum compiled by the radiolaria@mikrotax project team viewed: 3-12-2022

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