Organisms with external phosphatic shells diversified and became abundant at the beginning of the Early Paleozoic but gradually declined and were rare by its end. The decreasing availability of ...phosphorus in oceans is thought to be responsible for this evolutionary trend. Responses of organisms to changes in the phosphorus cycle can be traced to the late Neoproterozoic, and likely had a significant role in the Cambrian explosion, the Great Ordovician Biodiversification Event (GOBE), and the Devonian nekton revolution. Effective use of phosphorus by vertebrates during the Devonian nekton revolution caused the phosphorus pool to shift from benthic external shells to the skeletons of pelagic vertebrates, and moved the marine faunas toward the dominance patterns and ecological structure of the Modern Evolutionary Fauna.
Phosphorus had a key role in the Early Paleozoic radiation events.The decline of organisms with external phosphatic shells was caused by an increasing inaccessibility of phosphorus during the Early Paleozoic.The dominant phosphorus pool shifted from benthic groups to pelagic vertebrates during the Devonian.Recycling of phosphorus in the marine environment substantially moved phosphorous into the water column.The Devonian phosphorus pool pattern is one of the key factors controlling marine diversity and ecological patterns up to the present time.
Byronids are problematic fossils of possible cnidarian affinity, only rarely reported from the Devonian, but never previously studied in the Barrandian area, Czech Republic. Two new species ...Prestephanoscyphus branzovensis sp. nov. and Prestephanoscyphus robustus sp. nov. are erected from the Lochkovian and the Eifelian, respectively. Four poorly known species referred to Byronia are described in open nomenclature from the Emsian and Eifelian. The new genus Parabyronia gen. nov. with the type species Parabyronia elegans sp. nov. is closely related to other sphenothallids but is distinguished by transverse ridges on its theca and short spines at the apertural end of the theca. Definite identification of phosphatic rings as the attachment structure of byronids was proved by new material of the Lochkovian age. A dwarf conularia Pidiconularia gen. nov. with the type species Pidiconularia tubulata sp. nov. is remarkable by its minute size and very fine ornament; its conulariid affinity is proved by subrectangular cross-section and four internal carinae. Microstructure of theca of Prestephanoscyphus is characterised by alternation of compact laminae of aligned columnar microcrystallites and chambered laminae with isometric microcrystallites of apatite. Accretionary growth of byronid theca and structure of the holdfast with basal opening for the adhesive pedal disc support their cnidarian affinity although they likely display the bilateral instead of tetramerous symmetry. The protective function of bilaterally symmetrical whorls of internal apophyses in Prestephanoscyphus is suggested and their role in strengthening of thecal wall or supporting function of gastric septa are disputed. The byronids are regarded as epibionts rather than attached to the rocks. They are representatives of benthic groups with phosphatic shells that declined with decreasing availability of phosphorus in seas and oceans.
Baragwanathia brevifolioides is established as a nomen novum for B. brevifolia P.Kraft et Kvaček, 2017, recently described from the Silurian of the Prague Basin, Czech Republic and revealed as a ...later homonym of B. brevifolia Hundt, 1952.
Epizoic invertebrates attached to shells are a rare component of the fauna of the Šárka Formation (Middle Ordovician; early to middle Darriwilian) of the Prague Basin (Barrandian area) in the Czech ...Republic. Epibionts are known exclusively from siliceous nodules and consist of echinoderms (edrioasteroids and possible crinoid holdfasts), monoplacophorans, and bryozoans, all attached to a very small number of host taxa. Among them, hyoliths are the strongly preferred substrate (60% of observed host shells), with edrioasteroids, possible crinoid holdfasts and the monoplacophoran Pygmaeoconus attaching exclusively to these organisms. Epizoan holdfasts were also found on a unique ramose problematic fossil considered to be the first octocoral specimen from the Šárka Formation. Most of the host are interpreted have been colonized during life, only a few shells were used for attachment post mortem. All epibionts are attached to the outer surface of the shell, with the exception of the monoplacophoran Barrandicella, which is attached to the internal surface of empty conulariid thecae. Some of the epibionts shed additional light on the mode of life of their hosts, including the bivalve Redonia, which is shown to be semi-infaunal rather than infaunal. More generally, epibionts in the Šárka Formation attest to a very low level of occupancy of this significant niche during the early stages of the Great Ordovician Biodiversification Event.
•Epibionts of the Bohemian Darriwilian are very poorly diversified.•Hyolith conch are the most often host shells.•Epibionts belong only to chinoderms, monolacophorans and bryozoans.•First discovered octocoral in the Bohemian Darriwilian bears epibionts.•Epibionts support reconstructions of host taxa modes of life.
Dendroids have palaeoecological potential but are underrated in general. The present study is focused on the interval from the Floian to the earliest Sandbian (Klabava, Šárka and Dobrotivá ...formations) in the Ordovician of the Prague Basin (Czech Republic). It is based especially on the new datasets of all dendroid graptolites from the Šárka and Dobrotivá formations at our disposal combined with the data of the overall biodiversity in the studied interval. The analysis of diversity illustrates that there is a remarkable contrast in the studied period: dendroids declined when other groups flourished and the diversity in the Prague Basin reached the first of the two Ordovician maxima coeval with the GOBE. The patterns of those shifts seem to be primarily influenced by local environmental changes, i.e. ecologically controlled in the Prague Basin. The decline of dendroid graptolites was apparently caused by the disappearance of habitats, represented by proper substrate in the oxygenated environment, due to a gradual but continuing sea level rise. Our case study resulted in the distribution model providing a general example of local factors masking those global and exemplifying a significance of differentiation between global and local causes of the GOBE.
•Dendroid graptolites declined during the GOBE in the Prague Basin.•Decline of dendroids was ecologically controlled.•The main factor of the decline was disappearing proper substrate.•Bohemian Ordovician dendroids provide examples of local factors masking those global.•Palaeoecologic potential of dendroid graptolites is long-term underestimated.
Ordovician of the Bohemian Massif
Special publication - Geological Society of London/Geological Society, London, special publications,
06/2023
Journal Article
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