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Actinomma? magnifenestra Lazarus, 1992

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Single large cortical shell, no medullary shells observed. Cortical shell spherical or slightly irregular in shape. Lattice wall bars moderately thick, somewhat angular in cross section, weakly framed. Pores large, subcircular to strongly polygonal, vary in size but are fairly large relative to shell diameter. Several (10-30) short- to medium-length, tapered, three-bladed spines project from the surface of the shell.

A form similar to, but probably not conspecific to A.? magnifenestra is common in middle and late Miocene sediments (Plate 3, figs. 10-12). This related form has more circular, smaller pores, and reduced or absent external spines. This species is tentatively placed in Actinomma, despite the absence of inner shells, because of the similarity of the cortical shell to other members of Actinomma (e.g., irregular pore shapes, numerous three-bladed spines, etc.). Correct generic assignement will require a revision of current generic definitions in actinommids, which are generally recognized to be highly artificial.
Lazarus 1992











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