CATALOG OF ORIGINAL DESCRIPTIONS: Trigonactura angusta Riedel 1959

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.

Higher levels: rads_cat -> T -> Trigonactura -> Trigonactura angusta
Other pages this level: T. angusta, T. lanceolata, T. rhopalastrella, T. triacantha, T. trigonobrachia, T. trigonodiscus, T. trixiphos

Trigonactura angusta

Citation: Trigonactura angusta Riedel 1959
Rank: species
Type specimens: pl.1, fig.6
Type repository: Holotype, U.S.N.M. no.563356, U.S. National Museum, Washington, D.C.
Described on page(s) : p.292
Family (traditional): Coccodiscidae
Family (modern): Coccodiscidae

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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. gs


Trigonactura angusta compiled by the radiolaria@mikrotax project team viewed: 18-4-2021

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