Catalog entries: Porodiscus circularis
Original description: Shell circular, cakelike in shape with a flat edge; all rings (four or five) circular, concentric, annular, regularly increasing in breadth from the center to the periphery, connected by numerous thin, commonly alternating radial beam, some of which are piercing and some not; pores rather small, of several sizes, regularly subcircular, three or four on the breadth of a ring; margin of disk slightly spiny, with small, irregular spines of different lengths.
Diameter of disc, 230-290µm; of pores, 4.4-6.6µm; breadth of rings, 23.2-40.8µm. Distinguishing characters (rw): Several .specimens of this species have been photographed and they give some idea of the range of shape and general characters of shells assigned to the species. The small, or irregular shells are not included in the measurements.
Porodiscus circularis n. sp. is near P. concentricus, from the Tertiary, Haeckel (1887), but the rings are regularly unequal in breadth, and there are more pores in each ring. There are fewer pores on a ring than in P. microporus Haeckel (1887), and the rings increase regularly in size. There are more radial beams than in P. ellipticus Haeckel (1887), another fossil form, and this species differs from P. heterocyclus Haeckel (1887), yet another Tertiary fossil, in having more pores on a ring and the pores not so regularly increased in size.
Last occurrence (top): within Neogene Period (2.59-23.03Ma, top in Piacenzian stage). Data source: Lazarus et al. 2015 - "N age group"
First occurrence (base): within Neogene Period (2.59-23.03Ma, base in Aquitanian stage). Data source: Lazarus et al. 2015 - "N age group"
Plot of occurrence data:
Circodiscus circularis compiled by the radiolaria@mikrotax project team viewed: 26-3-2023
Short stables page link: https://mikrotax.org/radiolaria/index.php?id=203525 Go to Archive.is to create a permanent copy of this page - citation notes