radiolaria - rads_cat - Dictyospyris discus

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Dictyospyris discus

Citation: Dictyospyris discus Sanfilippo & Riedel 1973

Lattice shell strongly compressed in the apical-basal direction or obliquely in relation to the apical-dorsal bar, and circular to reniform in outline.
QTSagittal ring distinct, D-shaped, in reniform specimens joined directly to the shell at apex, base, and posteriorly: the staight anterior bar of the sagittal ring extends freely across the shell cavity. and the indentation of the shell outline corresponds to the posterior part of the ring. In circular specimens, the sagittal ring is of about the same dimensions as in reniform ones. and therefore the posterior part of the sagittal ring (as well as the anterior part) extends freely across the shell cavity. In a small area at the base of the shell (which may he near the center of a flat face of the disc, or near its margin) are three or four collar pores-a pair of cardinal pores and one or two jugular pores posterior to them. The orientation of the sagittal ring in relation to the geometry of the disc varies; in some specimens the apical-dorsal bar is parallel to the axis of the disc and near that axis, while in others it can be at least 45 from this position so that its apical end is near the center of one face of the disc and its dorsal end near the margin of the opposite face.QTApart from the collar pores in some specimens, and a slightly enlarged vertical pore toward which the vertical spine is directed. the pores of the shell are small and circular. The shell wall is thick and smooth, and the pores therefore tubular. The apical spine is only very rarely expressed externally. Some specimens have thorns irregularly distributed around the margin of the discoidal shell, some have no such thorns, and occasional late reniform specimens have one cylin-dro-conical spine on the convexly curved margin and two on the indented margin giving a false impression of an apical horn and feet but having no connection with the sagittal ring (Plate 32. Figure 7).

Based on 30 specimens from 94-32, CC and 96-3, CC). Maximum diameter of lattice shell 85-125 µ, its height (thickness of the disc, measured on only 11 specimens) 40-75 µ.

The specific name is the Latin discus. and is used as a noun in apposition.

Distinguishing features: This species differs from D. gigas in being more strongly compressed. and in its collar pores being less distinct. It differs from D. sphaera in being compressed and in lacking the profusion of branches from the sagittal ring to the inner surface of the l

In the upper part of its range, D. discus is accompanied by another species (Plate 32, Figures 8,9; evidently closely related and perhaps even an evolutionary offshoot) in which the collar pores are at the margin of the disc, and the apical-dorsal bar is parallel to the plane of the disc and extended beyond it as a free apical spine. Three strong, usually lanceolate, feet are present-two primary laterals and a dorsal. The vertical pore is situated near the jugular pore(s). The sagittal ring is joined to the discoidal lattice shell posteriorly, is free within the cavity apically, and is connected to the lattice shell by a few bars near the departure of the apical spine from the ring. The proposed close relationship between this form and D. discus may seem unlikely in view of the different relationship between the sagittal ring and the geometry of the disc, but it is supported by the fact that in D. discus the apical-dorsal bar of the sagittal ring ts often oriented obliquely to the axis of the discoidal shell, and there is no other obvious ancestor of this unnamed species. It is important to distin-guish this form from superficially similar specimens of D. discus having three cylindro-conical marginal spines which bear no fixed relationship to the sagittal ring and its apophyses.[comment from RadWorld database]

References:

Sanfilippo, A. & Riedel, W. R. (1973). Cenozoic Radiolaria (exclusive of theoperids, artostrobiids and amphipyndacids) from the Gulf of Mexico, Deep Sea Drilling Project Leg 10. Initial Reports of the Deep Sea Drilling Project. 10: 475-608. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Dictyospyris discus Sanfilippo & Riedel 1973

Dictyospyris discus

References:

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