Taxonomic discussion: Clark and Campbell 1942 p.46 pl.1 figs.12,14; Blome 1992 (ODP 122 SR) p.643 pl.2 fig.10 (synonymy)
Catalog entries: Amphymenium splendiarmatum
Original description: Shell elongate, distaff-shaped, about 3 and half times longer than the greatest breadth in length, contracting more or less regularly from the midregion to the blunted ends which are armed with a short, spinelike, hyaline spike and with seven smaller, accessory spines which encircle the terminal spike; arms obscurely jointed, transverse septa hardly evident, each arm having a strong radial beam which gives off segmental branches, and these branches are the only evidence of joints; patagium incomplete, convex-cylindrical, enclosing the midregion of the shell and at only a little distance from it, connected with it by means of thin beams; central spiral disc with five, uniform whorls; surface spongy, about eight pores across the arm transversely; pores round, uniform, enclosed in a hexagonal framework, the bars being less than a fourth of the diameter of the pores; in a dry preparation the shell appears very different from one prepared on a glass slide and balsam.
Length of shell, 260-300µm; radius of arm, 160µm; width of arm, 39.0µm; greatest breadth, 64-80µm; diameter of pores, 6.6µm. In a number of specimens one arm is shorter than the other, 120 as against 160µm in length; otherwise the arms are alike. Distinguishing characters (rw): Amphymenium splendiarmatum n. sp. is unlike either of the two species described in the same subgenus, A. amphistylium Haeckel (1887), and A. fusiforme Haeckel (1887), both recent Atlantic forms. From the former it differs principally in lacking segmental arms and from the latter, additionally, in the restriction of the patagium to the central region of the shell.
Remarks on original description: [The authors here list the species under the subgeneric name Ommathymenium 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:
Blome, C. D. (1992). Radiolarians from Leg 122, Exmouth and Wombat Plateaus, Indian Ocean C.D. Blome. Proceedings of the Ocean Drilling Program, Scientific Results. 122: 633-652. gs Clark, B. L. & Campbell, A. S. (1942). Eocene radiolarian faunas from the Mt. Diablo area, California. Geological Society of America, Special Papers. 39: 1-112. gs
Blome, C. D. (1992). Radiolarians from Leg 122, Exmouth and Wombat Plateaus, Indian Ocean C.D. Blome. Proceedings of the Ocean Drilling Program, Scientific Results. 122: 633-652. gs
Clark, B. L. & Campbell, A. S. (1942). Eocene radiolarian faunas from the Mt. Diablo area, California. Geological Society of America, Special Papers. 39: 1-112. gs
Amphymenium splendiarmatum compiled by the radiolaria@mikrotax project team viewed: 20-9-2021
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