CATALOG OF ORIGINAL DESCRIPTIONS: Larcidium etroplus Clark & Campbell 1942

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 -> L -> Larcidium -> Larcidium etroplus
Other pages this level: L. axacanthum, L. dissacanthum, L. dodecanthum, L. etroplus, L. hexacanthum, L. octacanthum, L. polyacanthum

Larcidium etroplus

Citation: Larcidium etroplus Clark & Campbell 1942
Rank: species
Type locality: LL513
Type age (chronostrat): Late Eocene, Cenozoic
Type specimens: pl.5, fig.13
Type repository: University of California, Museum of Paleontology, San Francisco
Repository city: San Francisco
Described on page(s) : p.51

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Current identification:


Original Description
Shell with three distinct axes, strongly lentelliptical, laterally and transversely compressed, one end much more broadly elliptical than the opposite end, the whole shell with mostly regularly subcircular pores, a few being droplet-shaped, about twelve in number across the vertical axis, and ten across the transverse axis, the surface smooth, the pores without rims, but there are eight conical, four-angled spines, these spines not so long as the diameter of the outer medullary shell, two of them at about 45° from each other at the broad end, four more or less submedian, and equidistant, and two spines at about 85° from each other near the narrow end of the shell, wall thin; secondary medullary shell eccentric near the narrow elliptical end of the cortical one, its diameter approximately 0.27 diameter of the cortical shell, nearly globular (unusual in the genus), with about fifteen or more very small subcircular to subhexagonal pores across a diameter, bars less than a fourth of the diameter of a pore in width, supporting beams prismatic, around 2.0µm, in thickness, two lateral pairs and two polar pairs, the former shorter than the other's because of the position of this shell within the cortical one; primary medullary shell half the diameter of the secondary one, with eight large, hexagonal pores forming a hemisphere, bars very thin and dense, supporting beams twelve or more, in pairs, more or less equidistant.

Size: Sagittal axis, 111.2µm; transverse axis, 93.6µm; length of spines, 25.4µm; diameter of outer medullary shell, 38.6 by 40.8µm; of inner medullary shell, 21.0µm; of pores of cortical shell, 8.8µm.

Extra details from original publication
Distinguishing features: Larcidium etroplus n. sp. resembles, perhaps, L. polycanthum Haeckel (1887). It has, however, a smaller outer medullary shell, fewer beams, and a well-developed primary medullary shell. It is also a smaller species.

References:

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


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Larcidium etroplus compiled by the radiolaria@mikrotax project team viewed: 9-3-2021

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