radiolaria - rads_cat - Cannartus laticonus radiolaria - rads_cat - Cannartus laticonus

CATALOG OF ORIGINAL DESCRIPTIONS: Cannartus laticonus 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 -> C -> Cannartus -> Cannartus laticonus
Other pages this level: C. biscottus, C. bitubulus, C. haeckelianus, C. laticonus, C. petterssoni, C. sp. C of Sakai (1980), C. sp. E of Sakai (1980), C. violina

Cannartus laticonus

Citation: Cannartus laticonus Riedel 1959
taxonomic rank: species
Described on page(s) : p.291
Type specimens: pl.1, fig.5
Type repository: Holotype USNM No. 563355 [Globigerinatella insueta zone of the Cipero formation, Golconda Railway Station, Trinidad] , U.S. National Museum, Washington, D.C.
Family (traditional): Coccodiscidae

Current identification/main database link: Didymocyrtis laticonus (Riedel) Sanfilippo and Riedel 1980


Original Description

Cortical twin-shell rather thick-walled, with pores subcircular or circular, ten to thirteen on the half-equator. On the broader parts of the shell, on either side of the equatorial constriction, are pronounced obtuse moundlike protuberances, at which the shell wall is thickened; there is a tendency in some specimens for these protuberances to be so arranged that two girdles of them encircle each half of the twin-shell. At each pole of the shell arises a broadly subconical, densely spongy column, which is almost as broad at its base as the polar surface of the twin-shell. Medullary shells two (or perhaps only one in some specimens), of which the inner is spherical and the outer spherical or lenticularly compressed. This species is distinguished from all others of the genus by the broadly subconical polar columns.




Size:
Based on 20 specimens. Length of polar columns 45-70 µ; median breadth 28-40 µ. Length of cortical shell 93-125 µ; maximum breadth 68-113 µ. Breadth of outer medullary shell 30-35 µ.

Extra details from original publication
Distinguishing characters: The equatorially constricted cortical shell has a tuberculate surface, and bears wide, spongy polar columns. There are no pronounced caps, but a parallel-sided clear zone, no wider than the height of the tubercules, separates the cortical shell from the columns. (Cannartus laticonus in Riedel and Sanfilippo, 1978a)

Westberg and Riedel (1978) used this name only for specimens "in which the height of the clear zone below the spongy column is less than 0.2 the length of the cortical shell."

D. laticonus is distinguished from its ancestor, D. mammifera, by having "clear zones" parallel to the cortical shell. In addition, the spongy columns tend to be wider than those of D. mammifera. It differs from its descendant D. antepenultima in that the proportion of the length of the clear zone (cap) to the length of the cortical shell is less than 0.20. (Sanfilippo et al., 1985)

Phylogeny: D. laticonus evolved from D. mammifera and developed into D. antepenultima.

Editors' Notes
This species is one of a remarkable series of forms which evidently arose in the Upper Oligocene and underwent rapid evolutionary changes during the Miocene. They apparently represent the phyletic connection between the genus Pipettella, in which an ellipsoidal cortical shell without equatorial constriction bears subcylindrical spongy polar columns, and the panartids, in which the equatorially constricted cortical shell bears latticed polar caps. It has previously been shown (Riedel, 1957) that a common late Tertiary panartid, Panarium penultimum, has distinct polar caps surmounted by spongy polar columns, and the author has pointed out that this species probably developed from a form having less conspicuous polar caps and wider terminal spongy columns.

References:

Riedel, W. R. & Sanfilippo, A. (1970). Radiolaria, Leg. 4 DSDP. Initial Reports of the Deep Sea Drilling Project. 4: 503-575. gs

Riedel, W. R. (1959a). Oligocene and Lower Miocene Radiolaria in tropical Pacific sediments. Micropaleontology. 5(3): 285-302. gs


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Cannartus laticonus compiled by the radiolaria@mikrotax project team viewed: 13-6-2024

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