Test structure in some pioneer multichambered Paleozoic foraminifera

Abstract

Foraminiferal wall microstructures, consistent with the molecular-based high-rank classification, are critical to understanding foraminiferal evolution and advanced taxonomic relationships. Although test structures are well documented for recent, Cenozoic, and some Mesozoic foraminifera, the diagnostic characteristics of Paleozoic taxa are largely unexplored. The majority of calcareous Paleozoic foraminifera have been assigned to the Fusulinata based on questionable homogeneously “microgranular” test wall microstructures, which have never been sufficiently documented for most taxa. We investigated the test structures of exceptionally well-preserved Devonian (Eifelian) Semitextularia thomasi, representing the first calcareous true multichambered (serial) foraminifera, and compared this species with a large fusiform Permian representative of “true” fusulinids (Neoschwagerinidae). The tests of Semitextularia thomasi display lamellar structures that are not observed in any other fossil or recent foraminiferal group. The Paleozoic foraminifera, traditionally referred to one taxon (the class Fusulinata), possess at least three contrasting test wall microstructures, representing separate high-rank taxonomic groups. Fusulinata is most likely a highly polyphyletic group that is in need of taxonomic revision. The term Fusulinata, defined as including all Paleozoic calcareous forms except Miliolida and Lagenata, is not phylogenetically meaningful and should no longer be used or should be restricted to true complex fusulinids with microgranular test structures, which appeared in the Carboniferous.

The pre-Taghanic (Givetian, Middle Devonian) ecosystems of Miłoszów (Holy Cross Mts, Poland)

“…The mid-Devonian is regarded as one of the most important phases of the evolutionary history of foraminifers. It comprises the origin of true calcareous plurilocular forms and was probably linked with the evolutionary development of the main Recent foraminiferal clades (Pawlowski et al, 2003(Pawlowski et al, , 2013Dubicka and Gorzelak, 2017), as well as of some extinct groups of Foraminifera (Dubicka et al, 2021a).…”

An image dataset of fusulinid foraminifera generated with the aid of deep learning

“…Throughout their history, they exhibit high diversity and serve as an important component of the marine ecosystem (Gupta, 1999; Vachard et al, 2010). Fusulinids, herein refer to Order Fusulinida (Wedekind, 1937) under Class Fusulinata (Dubicka et al, 2021; Vachard et al, 2010) are Palaeozoic larger benthic foraminifera that developed calcareous, planispiral, mostly spindle‐shaped tests with dozens to over 100 segmented chambers (Figure 1a). They appeared in the shallow sea of the Carboniferous and then thrived until the Late Permian (Pawlowski et al, 2003; Vachard et al, 2010).…”