Redescription and palaeobiology ofPalaeoscorpius devonicusLehmann, 1944 from the Lower Devonian Hunsrück Slate of Germany

Abstract

: Palaeoscorpius devonicus Lehmann, 1944 is known from only a single specimen, found in the Eschenbach Pit near Bundenbach in the Lower Devonian Hunsrück Slate of Germany. It is a key fossil, having been interpreted both as the most basal member of the Scorpiones and as one of the order’s most likely candidates for an aquatic mode of life. Prepared both ventrally and dorsally, some aspects of its morphology remain problematic. Here, with the aid of new techniques, including computed tomography, we present a re‐investigation of this scorpion’s anatomy and a new reconstruction, with a particular focus on the species’ original habitat. On the basis of the environmental interpretation of the Hunsrück Slate and the completeness of the specimen, previous authors concluded that P. devonicus was marine, but none offered convincing morphological evidence. Recent studies of the deposit’s environment suggest that the Hunsrück Sea was part of an intrashelf basin, relatively close to the coastline, and fossils of land plants show that terrestrial wash‐in occasionally occurred. Our revised interpretation of the fossil’s morphology demonstrates that the scorpion was most probably terrestrial. Internal mesosomal organs are interpreted as book lungs, but other terrestrial adaptations are lacking. The absence of both coxapophyses and gnathobases makes determining the scorpion’s feeding mechanism difficult. Interpreting the scorpion’s character states within a phylogenetic framework, especially the possible presence of book lungs, implies either that the plesiomorphic position of P. devonicus is no longer supported or that the development of book lungs had already taken place early in the scorpion lineage.

X-ray micro-computed tomography (micro-CT) of pyrite-permineralized fruits and seeds from the London Clay Formation (Ypresian) conserved in silicone oil: a critical evaluation

“…These include: structures interpreted as colonial organisms from the Paleoproterozoic (El Albani et al 2014); a pseudoscorpion encased in amber containing highly X-ray attenuating crystals inferred to be pyrite (Henderickx et al 2013); and fossils from an exceptionally preserved biota from the Devonian Hunsrück slates in Germany (e.g., Kühl et al 2012). Most Hunsrück fossils contain iron pyrites and these were some of the first fossils to be studied with X-rays by Stürmer from 1968 onwards (Bartels et al 1998).…”

Scorpion Fragments from the Silurian of Powys, Wales

“…New imagery was obtained using radiography, X-ray micro-tomography, and CT scanning techniques. Layered internal mesosomal organs were located and interpreted as probable book lungs (Kühl et al 2012). Kühl et al (2012) note that much of the argument for Pa laeoscor pius Lehmann, 1944 being marine was based on the belief that the Hunsrück Slate was of deep marine origin.…”

“…Layered internal mesosomal organs were located and interpreted as probable book lungs (Kühl et al 2012). Kühl et al (2012) note that much of the argument for Pa laeoscor pius Lehmann, 1944 being marine was based on the belief that the Hunsrück Slate was of deep marine origin. Conversely, recent studies of the palaeoenvironment suggest that the 'Hunsrück Sea' was part of an intrashelf basin close to the shore, into which terrestrial plants were periodically washed.…”

“…Scorpions are extremely conservative organisms that occur in the fossil record from the early Silurian period (Størmer 1977;Dunlop & Selden 2013) and are believed to have been an entirely terrestrial clade (e.g. Scholtz & Kamenz 2006;Dunlop et al 2008;Kühl et al 2012), with the exception of Devonian Waeringoscorpio Størmer, 1970 which may have been secondarily aquatic (Kühl et al 2012).…”

“…Palaeoscorpius devonicus Lehmann, 1944 from the Lower Devonian Hunsrück Slate Lagerstätte in Germany has also been re-investigated (Kühl et al 2012). This key fossil was formerly interpreted as the most basal member of the Scorpiones and as one of the order's most likely candidates for an aquatic mode of life (Jeram 1998).…”