Catalog entries: Heliodiscus hexasteriscus
Original description: Shell like a sunburst with six rays of moderate length, equal in size except as broken, about half the diameter of the cortical shell in length, strongly four-angled in the lower three-fourths and rounded distally; tips bluntly pointed, the bases flaring to the disc; hyaline, and with short, backwardly directed processes or hooklets in the proximal part, these evidently the places of attachment of contractile protoplasmic myonemes; cortical shell lenticular, biconvex, with small, regular, equal circular pores, the pores with thin, raised rims or collars and with very minute, rarely bifurcate, mostly simple, sepaloid spinules, about twenty pores or more in a radius, and from five to nine around the edge on an interradius; cavity of the pores cylindrical, asymmetrically pointed toward the center of the disc, wall thick; medullary shell obscured by the extreme density of the cortical wall.
Diameter of cortical shell, 160µm; of pores, 8.8µm; length of spines, 78.2µm; width of wall, 12.2µm; of spine above the flaring base, 18.8µm. Distinguishing characters (rw): A second specimen (Pl. 3, fig. 14) has a somewhat larger cortical shell (180µm) and its medullary shell is clear-cut (43µm). The spines are all broken and not subequidistant as int he more complete specimen. The spines, also, are thinner and less flaring at the base.
Heliodiscus heliasteriscus n. sp. differs from H. pentasteriscus n. sp. in its small disc (160 as against 200µm) and, also, has six instead of five spines, these last not strictly equidistant and forming a line of symmetry as in the five-rayed species.
Remarks on original description: [The authors here list Heliodiscus hexasteriscus under the subgeneric name Heliodiscetta and include the subgeneric name in the species name.
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:
Heliodiscus hexasteriscus compiled by the radiolaria@mikrotax project team viewed: 14-5-2021
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