Re-assessment of Arthropleura from the Moscovian of Northern France: new anatomical information and adaptations to terrestrial environments

The fossil record of Arthropleura, distributed in the Nord-Pas-de-Calais coalfield (France) and some Belgian localities, is reassessed and compared to new material discovered in new localities of the Bruay Formation. Based on tergite ornamentation, the Bruay specimens are attributed to Arthropleura mammata. Two specimens are preserved with their head, allowing the description of the head anatomy of this species for the first time. We estimated the size of the most complete remains from the newly investigated localities, with a maximum length probably reaching 50 centimetres. The geographical extension of A. mammata can be extended to the Nord-Pas-de-Calais and to the Saarland coal basins. Some specimens from the Bruay Formation consist of K-plates, typical ventral plates of arthropleurids displaying well-preserved pierced tubercules. These pierced tubercules are also found in K-plates of Arthropleura cristata, found in the Mazon Creek Lagerst¨atte, and could represent spiracles similar to the ones found in millipedes. This suggests that Arthropleura possessed a tracheal system for respiration and, combined with other anatomical factors, would confirm it as a terrestrial arthropod.