Triassic Isopoda - three new species from Central Europe shed light on the early diversity of the group

Abstract

Despite its vernacular names (e.g. 'woodlice') Isopoda is a group with mostly aquatic species, with most species living in marine environments. The fossil record for isopods compared to other groups of Eucrustacea is relatively sparse. This applies even more for the Triassic. While in the Jurassic Isopoda is relatively well represented by fossils, only eight species have previously been described from the Triassic. In this study three new species of Isopoda are described from two field sites in Europe: Obtusotelson summesbergeri sp. nov. and Discosalaputium aschauerorum sp. nov. from Polzberg (Gaming, Lower Austria, Austria) and Gelrincola winterswijkensis sp. nov. from Winterswijk (Gelderland, Netherlands). All three new species are interpreted as representatives of Scutocoxifera (ingroup of Isopoda). The species Gelrincola winterswijkensis sp. nov. is further interpreted to be a representative of Cymothoida (ingroup of Scutocoxifera). Most of the oldest fossils of Isopoda belong to Phreatoicidea, which is supposed to be the sistergroup to all remaining Isopoda. Nowadays, Phreatoicidea is a small relic group, its representatives living in freshwater environments. The new species herein presented contribute to our understanding of the diversity of Isopoda in the Triassic and support the assumption that the transition from a dominance of Phreatoicidea towards the dominance of the remaining lineages of Isopoda happened quite early (likely prior to the Triassic).

The Upper Triassic Polzberg palaeobiota from a marine Konservat-Lagerstätte deposited during the Carnian Pluvial Episode in Austria

“…minor 26 , 27 CLXXXVI = 186, p. 682). Constituents are ammonites 2 , 5 , 26 , 27 (n 4522), anaptychi 28 (n 46), coleoids 16 , 17 , 29 (proostraca, phragmocones, hooks, cartilage; n 386), bivalves 2 , 11 , 30 (n > 10.000), gastropods 30 (n 96), arthropods 3 , 18 , 30 (n 207), polychaetes (n 17), echinoderms 30 (n 1), trace fossils 5 (bromalites; n 112), conodontophorids (n 12), fish 5 , 11 , 14 , 31 – 33 (n 1181), chondrichtyes 2 , 5 (n 1); lungfish 12 , 13 , 34 , 35 (skull with attached teeth plates; n 1), coelocanths 13 , 36 , 37 (n 5) and rare plant remains (n 12; Table 1 ). A. minor appears with partly preserved buccal apparatuses of anaptychus-type lower jaws 28 .…”

“…As most of the historical excavation reports and papers were written in German, they failed to reach a broader international scientific community. More recently, new palaeontological data and faunal elements were published from the Polzberg Lagerstätte 3 , 14 – 18 . The biostratigraphic data hint to a Julian 2 Ib ( Austrotrachyceras austriacum Zone, A. minor biohorizon) age of the main fossiliferous part of the Polzberg section.…”

A non-marine horseshoe crab from the Middle Triassic (Anisian) of the Netherlands

“…P. spinosa (Assmann, 1927), which constitute the oldest known lobsters from the Netherlands (Klompmaker & Fraaije, 2011). Furthermore, the isopod Gelrincola winterswijkensis Schädel et al, 2020, and (Schweitzer et al, 2019;Schädel et al, 2020). In addition, Winterswijk is the only Muschelkalk outcrop that has yielded a small assemblage of insect remains, including, amongst others, the elytron of a beetle (Coleoptera), a partial dragonfly wing (Odonata) and a complete forewing of a cockroach (Blattodea) (Van Eldijk et al, 2017).…”

“…Amongst these newly added horizons is an approximately 1.20 m thick layer, known as layer 43, in which the specimen we describe here, RGM.1333509, was discovered by one of the authors (HW). Layer 43 has previously yielded exceptionally well-preserved fossil fishes (Maxwell et al, 2016), insect remains (Van Eldijk et al, 2017) and the only known specimen of the isopod G. winterswijkensis (Schädel et al, 2020). Based on the occurrence of the bivalve Neoschizodus orbicularis (Bronn, 1837), the top section of the profile at Winterswijk, to which layer 43 belongs, has been tentatively dated to the youngest substage of the Anisian (Illyrian) (Hagdorn & Simon, 2010).…”

Comment on the letter of the Society of Vertebrate Paleontology (SVP) dated April 21, 2020 regarding “Fossils from conflict zones and reproducibility of fossil-based scientific data”: the importance of private collections

“…Some recent examples are the skull of Nothosaurus winkelhorsti (named after the amateur collector Herman Winkelhorst; Klein and Albers 2009), Palatodonta bleekeri (named after the amateur collector Remco Bleeker; Neenan et al 2013), Pararcus diepenbroeki (named after the amateur collector Gerben Diepenbroek; Klein and Scheyer 2014), and the cyclid crustacean Halicyne oosterinkorum (named after the late collector Henk Oosterink and his family; Schweitzer et al 2019). Recently, a new marine isopod species was found by Mr. Winkelhorst, donated from his collection to the Naturalis Biodiversity Center, and described as the new taxon Gelrincola winterswijkensis (Schädel et al 2020). It can be stated without exaggeration that most of our knowledge about the Middle Triassic of the western Germanic Basin is based on material collected by amateurs.…”