Kowala Lagerstätte: Late Devonian arthropods and non-biomineralized algae from Poland

Abstract

A rich and diverse assemblage of arthropods and non-biomineralized macroalgae occurs in the Upper Devonian marine deposits of the Holy Cross Mountains, central Poland. The phrase Kowala Lagerstätte is herein proposed for the fossil-bearing deposits confined to the lower Famennian marly shale and limestone succession of the famous Kowala Quarry. The arthropod fauna is represented by phosphatic exoskeletal remains that still preserve the fine micro-ornamentation of the cuticle. The fauna includes crustaceans and crustacean-like taxa such as thylacocephalans, phyllocarids and angustidontids (in order of abundance). The non-biomineralized algae, represented by at least three morphotypes, occur as carbonaceous compressions of their thalli while still preserving fine details including bundles of thin tubular projections. Although their general appearance is reminiscent of some Early Palaeozoic non-calcified Dasycladales algae, their true taxonomic position is still uncertain. Lithology, as well as faunal and phytoplankton content point to a pelagic sedimentary environment. Impoverished benthic fauna, sediment lamination and geochemical signatures indicate at least periodic bottom-water dysoxic to anoxic conditions. Thus, the preservation of arthropod cuticle and non-calcified algae was primarily governed by oxygen-deficient bottom waters that prevented bioturbation and scavenging during their burial.