@article {420, title = {A new Devonian euthycarcinoid reveals the use of different respiratory strategies during the marine-to-terrestrial transition in the myriapod lineage}, journal = {Royal Society Open Science}, volume = {7}, year = {2020}, month = {21/10/2020}, pages = {1-9}, abstract = {

Myriapods were, together with arachnids, the earliest animals to occupy terrestrial ecosystems, by at least the Silurian. The origin of myriapods and their land colonization have long remained puzzling until euthycarcinoids, an extinct group of aquatic arthropods considered amphibious, were shown to be stem-group myriapods, extending the lineage to the Cambrian and evidencing a marine-to-terrestrial transition. Although possible respiratory structures comparable to the air-breathing tracheal system of myriapods are visible in several euthycarcinoids, little is known about the mechanism by which they respired. Here, we describe a new euthycarcinoid from Upper Devonian alluvio-lagoonal deposits of Belgium. Synchrotron-based elemental X-ray analyses were used to extract all available information from the only known specimen. Sulfur X-ray fluorescence (XRF) mapping and spectroscopy unveil sulfate evaporation stains, spread over the entire slab, suggestive of a very shallow-water to the terrestrial environment prior to burial consistent with an amphibious lifestyle. Trace metal XRF mapping reveals a pair of ventral spherical cavities or chambers on the second post-abdominal segment that do not compare to any known feature in aquatic arthropods, but might well play a part in air-breathing. Our data provide additional support for amphibious lifestyle in euthycarcinoids and show that different respiratory strategies were used during the marine-to-terrestrial transition in the myriapod lineage.

}, keywords = {air-breathing, fossil arthropods, synchrotron radiation, Terrestrialization, X-ray fluorescence imaging, X-ray spectroscopy}, issn = {2054-5703}, doi = {10.1098/rsos.201037}, url = {https://royalsocietypublishing.org/doi/10.1098/rsos.201037}, author = {Gueriau, Pierre and Lamsdell, James C. and Wogelius, Roy A. and Manning, Phillip L. and Egerton, Victoria M. and Bergmann, Uwe and Bertrand, Lo{\"\i}c and Denayer, Julien} } @article {300, title = {Aquatic stem group myriapods close a gap between molecular divergence dates and the terrestrial fossil record}, journal = {Proceedings of the National Academy of Sciences}, volume = {117}, year = {2020}, month = {06/04/2020}, pages = {8966 - 8972}, abstract = {

Identifying marine or freshwater fossils that belong to the stem groups of the major terrestrial arthropod radiations is a longstanding challenge. Molecular dating and fossils of their pancrustacean sister group predict that myriapods originated in the Cambrian, much earlier than their oldest known fossils, but uncertainty about stem group Myriapoda confounds efforts to resolve the timing of the group\’s terrestrialization. Among a small set of candidates for membership in the stem group of Myriapoda, the Cambrian to Triassic euthycarcinoids have repeatedly been singled out. The only known Devonian euthycarcinoid, Heterocrania rhyniensis from the Rhynie and Windyfield cherts hot spring complex in Scotland, reveals details of head structures that constrain the evolutionary position of euthycarcinoids. The head capsule houses an anterior cuticular tentorium, a feature uniquely shared by myriapods and hexapods. Confocal microscopy recovers myriapod-like characters of the preoral chamber, such as a prominent hypopharynx supported by tentorial bars and superlinguae between the mandibles and hypopharynx, reinforcing an alliance between euthycarcinoids and myriapods recovered in recent phylogenetic analysis. The Cambrian occurrence of the earliest euthycarcinoids supplies the oldest compelling evidence for an aquatic stem group for either Myriapoda or Hexapoda, previously a lacuna in the body fossil record of these otherwise terrestrial lineages until the Silurian and Devonian, respectively. The trace fossil record of euthycarcinoids in the Cambrian and Ordovician reveals amphibious locomotion in tidal environments and fills a gap between molecular estimates for myriapod origins in the Cambrian and a post-Ordovician crown group fossil record.

}, keywords = {Arthropoda, euthycarcinoid, molecular dating, Myriapoda, Terrestrialization}, issn = {0027-8424}, doi = {10.1073/pnas.1920733117}, url = {http://www.pnas.org/lookup/doi/10.1073/pnas.1920733117}, author = {Edgecombe, Gregory D. and Strullu-Derrien, Christine and G{\'o}ral, Tomasz and Hetherington, Alexander J. and Thompson, Christine and Koch, Markus} }