Trigonactura_ angusta Riedel 1959.jpg
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Trigonactura_ angusta Riedel 1959.jpg<% linkedspecs %>
Current identification/main database link: Lithocyclia angusta (Riedel 1959)
Original Description
Phacoid cortical shell approximately three times as broad as the medullary shell (when the latter is distinct), with eight to eleven subcircular to circular pores on its radius. Cortical shell in some specimens filled with spongy meshwork. Three arms not strictly chambered, but rather subcylindrical spongy columns, broader at the base and tapered distally. In rare specimens a spongy patagium, its outline parallel to that of the cortical shell, connects the bases of the arms.
(based on twenty specimens): Diameter of cortical shell 108-145µm, of medullary shell (shadowy outline seen through cortical shell) 35-50µm. Length of arms 85-158µm; median breadth 18-28µm. Distinguishing characters (rw): This species is distinguished from all others of the genus by its relatively narrow, subcylindrical arms.
Etymology: Latin angustus -a -um = narrow, limited, poor
Editors' Notes
The placement of this species in the genus Trigonactura is indicated as doubtful because a patagium is present in some specimens, and the medullary shell is not constant in structure; it is rarely if ever a well defined "shell." The arms differ in form from those of any other described members of this genus or closely related genera, probably because they represent a degeneration of the usual larger arms.
Riedel, W. R. (1959). Oligocene and Lower Miocene Radiolaria in tropical Pacific sediments. Micropaleontology. 5(3): 285-302. gsReferences:
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Trigonactura angusta compiled by the radiolaria@mikrotax project team viewed: 18-4-2021
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