Involutina, Terquem, 1862

Rigaud, Sylvain, Blau, Joachim, Martini, Rossana & Rettori, Roberto, 2015, Taxonomy, phylogeny, and functional morphology of the foraminiferal genus Involutina, Acta Palaeontologica Polonica 60 (1), pp. 235-244 : 237

Involutina model

The current models of test construction of Involutina ( Koehn-Zaninetti 1969; Piller 1978; Blau 1987b) do not integrate the whole complexity of the form. They are based on specimens in which the aragonite needles, laminar deposits (L1 lamellae), and lateral laminar extensions of the tube wall (L2 lamellae) are only partially preserved. In our material, only relics of the aragonite needles and the laminar deposits are preserved but in some specimens, the outline of the laminar extensions is entirely emphasized by the ferromanganese impregnation. Based on a detailed examination of Involutina liassica , we herein propose a new model for the Involutina structure ( Fig. 3 ). This structural model derives from the study of several randomly oriented sections and does not correspond to a single specimen. Its difference from previous models is largely founded on the arrangement of the laminar extensions that are interfingered in the umbilical region (as in the “ Aulotortus model”). Our model clearly contrasts with Piller’s model (1978) in which only one lamella is formed per whorl and contests the latest Involutinina phylogenetic tree proposed by di Bari and Laghi (1994).

Figures

Fig. 3. Structural model of Involutina (in axial section). The presence of a semitube, as defined by Piller (1978), is only barely discernible in few of our specimens.