Abstract

A remarkably well preserved assemblage of glomospiroid Involutinidae has been discovered in the Late Triassic of the Wallowa terrane (Oregon, U.S.A.). Contrary to other involutinids, these foraminifers show a ball-like coiling and reduced lateral laminar extensions of the tube wall, rendering their distinction from coeval calcitic homeomorphs difficult.

In this study, we propose new criteria for identifying involutinins and demonstrate that glomospiroid Involutinidae, previously classified with the planispiral subfamily Aulotortinae, constitute a separate group. Accordingly, the new subfamily Parvalamellinae, the new genus Parvalamella, three new species (P. ashbaughi, P. nolfi, and P. sigmoidea), and two new combinations (P. friedli and P. praegaschei) are established. The morphological distinction between the Aulotortinae and the Parvalamellinae not only reveals the important systematic value of the coiling mode and laminar extensions in classification of the Involutinina but also the potential role of luminosity in the development of the suborder.

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