Evolutionary, paleoecological and taphonomic aspects of new agglutinated foraminifer Devonodendron scopulum from the Frasnian of Holy Cross Mts, Poland

Abstract

Regularly bifurcated tubiform (tree-like) microfossils, although illustrated three decades ago from the Frasnian of the Holy Cross Mts (southern Poland), have not been studied in detail until now. In this paper, the distinctive microproblematic is interpreted as a calcite-cemented agglutinated foraminifer belonging to Devonodendron scopulum sp. et gen. nov., appearing in a major radiation after the Givetian Revolution. Based on the study of isolated three-dimensional specimens, this Devonian species is the best documented of the early branching foraminifera. It resembles living arborescent representatives of the family Schizamminidae (such as Schizammina arborescens and S. andamana), but also the family Dendrophryidae (Psammatodendron arborescens), which has already been reported in the fossil record (Cretaceous; questionable Silurian). However, in light of genetic studies of modern monothalamids, phylogenetic inferences based on such simple morphology are risky. The tree-like branching system of this species suggests erect attached and filter feeding life habit. Devonodendron scopulum shows a pronounced microhabitat selectivity, being dominantly restricted to mid-slope metazoan-microbial mud-mounds. The buildups provided microniches for flourishing a very abundant and diverse calcareous microbiota, including taxa with known (Nanicella) and presumed (Eifeliflabellum) foraminiferal affinities. The environment was characterized by a specific diagenetic setting for the fossilization of micritic-organic tubular tests due to rapid microbially mediated lithification and overwhelming recrystallization processes. As a result, microfossils are largely preserved as stacked homogeneous rhomboidal calcite plates. Many specimens in some sites are actually just coalesced sparry calcite ‘pseudomorphs’ mimicking the original test morphology.