D. pentaradiatus group

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Mon, 14/01/2008 - 12:37 — Jeremy Young

Citation:

Discoaster pentaradiatus group

This is an informal grouping for symmetric 5-rayed discoasters. These species probably do not form a clade but are a characteristic component of Late Miocene and Pliocene assemblages, including several important marker species.

Taxa included

	D. bergenii - D. berggrenii - D. quinqueramus lineage (NN11) - ray tips non-bifurcate; concavo-convex; large proximal boss
	D. pentaradiatus (NN10B-NN17) - ray tips bifurcate; concavo-convex; each ray behaves optically as separate crystal
	D. prepentaradiatus (NN9-10A) - ray tips bifurcate; complanate; whole disc behaves optically as single crystal
	D. hamatus (NN9) - ray tips asymetric & downward deflected
	D. bellus (NN8-11) - ray tips simple; more or less planar