New insights for ancient foraminifera through 3D visuals of fusulinids

Abstract

Fusulinids are larger benthic foraminifera of late Paleozoic and index fossils for Permo-Carboniferous strata. The traditional methods to examine their internal structures are through ground thin sections, which however caused lots of ambiguities regarding the morphological diagnostics and taxonomic identification.In recent years, new technique of high resolution X-ray computed tomography sheds light on the microfossil examination and we had fusulinid individuals successfully processed with this innovative approach. Here we present the results of 19 Pseudofusulina specimens, including high resolution images and rendered three-dimensional (3D) visuals of the important internal structures, to unwrap more details of fusulinid morphology. This is the first time the full 3D visuals of fusulinid interiors were constructed and exhibited. Previous understandings on fusulinid basic morphology, such as proloculus, chamber development, are precisely described with 3D illustration; cuniculi and phrenotheca are discovered regularly among the specimens and therefore are not suggested to be diagnostic features of taxonomic splitting; test and proloculus morphology divergences caused by section orientation are captured. With assistance of high resolution CT technique, fusulinid morphology, especially internal structures, is much easier to acquire, understand, and exhibit, despite the critical limitation that only the fusulinid samples buried with terrigenous clasts, such as those from calcareous mudstone or argillaceous limestone, could be successfully scanned.