Dictyocoryne ontongensis Riedel and Sanfilippo

Dictyocoryne ontongensis Riedel and Sanfilippo, 1971, p.1588, pl.1E, figs.1, 2, pl.4, figs.9-11

DESCRIPTION

Central disc small, with usually 5 concentric rings. Three arms arranged usually in a Y-shape, with one angle smaller than the others, but in some early specimens at equal angles. Arms rarely with slight transverse zonation, parallel-sided or slightly expanding distally; one or more of them forked distally at a very obtuse angle, each branch being approximately the same width as the distal part of the arm or wider, and with a bluntly rounded termination. Rarely, the terminations of the arms are doubly bifurcated. Some specimens have a patagium that occupies practically all of the space outlined by the arms and their bifurcations (Riedel and Sanfilippo, 1971).

DIMENSIONS

Based on 30 specimens. Maximum radius 116-215 m (Riedel and Sanfilippo, 1971).

DISTINGUISHING CHARACTERS

This species is the only one known to have three spongy arms in which one or more of the arms bifurcates distally.

VARIABILITY

Angle between arms varies from being equal (in early specimens) to having one angle smaller than the other two. Length of arms may also vary.

DISTRIBUTION

This low-latitude species has its morphotypic first appearance within the Dorcadospyris alata Zone. Its morphotypic last appearance lies within the Didymocyrtis antepenultima Zone.

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