Upper Ordovician Thylacocephala (Euarthropoda, Eucrustacea) from Bohemia indicate early ecological differentiation

Abstract

Thylacocephala is a clade of marine bivalved euarthropods generally considered to belong to Eucrustacea, although their affinities within this group remain unsettled. Detailed thylacocephalan anatomy and tagmosis is poorly known, and the majority of taxa have been described based only on the valves of the carapace. While some thylacocephalans are considered to have been fully nektic, others probably had a nekto-benthic mode of life. The group makes its last appearance in the Upper Cretaceous of Lebanon, while the previously oldest definite record is from the Silurian of Wisconsin, USA. This paper describes two new thylacocephalans, Pseudoprotozoea irenae gen. et sp. nov. and Bohemiacaris libori gen. et sp. nov. from the Sandbian (Upper Ordovician

REMAINS OF THE ALIMENTARY TRACT IN THE LATE ORDOVICIAN TRILOBITE <em>DALMANITINA</em> (PRAGUE BASIN, BARRANDIAN AREA, CZECH REPUBLIC)

“…The geological setting of the Letná Formation and the preservation of skeletal fossils and faunal and ichnofossil assemblages in the formation have been summarised by Fatka et al (2013 and Drage et al (2018). In the north-western limb of the Prague Basin, remains of non-mineralised and lightly mineralised fossils have been collected at several outcrops of the Letná Formation (Van Roy et al 2021, 2022. Many of these species had been described by Barrande in the nineteenth century, particularly the bivalved arthropods Nothozoe pollens Barrande, 1872, Zonozoe drabowiensis Barrande, 1872, Drabovaspis complexa (Barrande, 1872, the more or less problematic Triopus draboviensis Barrande, 1872 and Caryon bohemicum Barrande, 1872.…”

“…The cheloniellid arthropod Duslia insignis Jahn, 1893 and the marrellomorph Furca bohemica Fritsch, 1908 were described only slightly later. After a long gap, two other taxa, "Nothozoe" barrandei Chlupáč, 1970 and Zonoscutum solum Chlupáč, 1999, were established. Nearly all these taxa have been subsequently re-examined and re-interpreted (see Chlupáč 1988Chlupáč , 1999aRak et al 2009Rak et al , 2013Ortega-Hernández et al 2010;Van Roy et al 2021, 2022. Two new genera of thylacocephalans were described by Van Roy et al (2022).…”

The significance of Anomalocaris and other Radiodonta for understanding paleoecology and evolution during the Cambrian explosion

“…Moreover, two other species (two genera) could questionably belong to Hurdiidae. It is also the family that has the longest history, with fossils found from the Cambrian Stage 3 to the Lower Ordovician, and possibly the Devonian (Van Roy and Tetlie, 2006;Kühl et al, 2009;Van Roy et al, 2015;Wu et al, 2022). They have been found in 19 localities (20 if the Wheeler Formation is divided in two as suggested in Wu et al, 2022), with 16 of those being from the Cambrian, corresponding to five palaeogeographical domains and two localities from one domain during the Ordovician (Wu et al, 2022).…”

New Middle and Late Ordovician cornute stylophorans (Echinodermata) from Morocco and other peri-Gondwanan areas

“…Dalmanitids (Dalmanitina socialis) and trinucleids (Deanaspis goldfussi) dominate among trilobites (with many other genera present and locally common; see Fatka et al 2013). Notably diverse are non-trilobite arthropods (Chlupáč 1965(Chlupáč , 1999aRak et al 2009Rak et al , 2013Ortega-Hernandez et al 2010;Van Roy et al 2021). Bivalves belong to the Modiolopsis community (see Kříž & Steinová 2009;Polechová 2019).…”