Le projet Waxweiler, les Ptéraspidomorphes hétérostracés éodévoniens et le mythe des ‘Big Five’

Abstract

Waxweiler is a small city in Eifel, West Germany. Several quarries for extracting black shale are open there. They regularly yield a fossil assemblage of Early Devonian age. This includes, in particular, a new small pteraspid heterostracan, i.e., a ‘primitive’ jawless, armoured fish without paired fins, known as the ‘Waxweiler-Form’. It is represented by many complete or near-complete individuals which are used for re-interpreting a series of palaeontology topics. The latter include morphology and anatomy, systematics (taxonomy, phylogeny, nomenclature, classification), evolutionary biology (evolutionary trends, ecology, ethology), palaeoenvironements and especially those of the Old Red Sandstone that is a post- and late-Caledonian or Ellesmerian as well as pre-Variscan molassic megafacies. Other elements of the assemblage are other fishes, molluscs, ostracodes, eurypterids, lingulids, plants, trace fossils. Another important locality is Odenspiel in Bergisches Land. It delivers another new pteraspid which is most probably of the same clade as the ‘Waxweiler-Form’. It does show convergence with the psammosteid Drepanaspis which is usually another component of Early Devonian fossil assemblages of the Ardenne-Rhenish Slate Massif. Both discoveries will lead to new geobiological interpretations of the end-Proterozoic (Ediacaran) to Mid-Palaeozoic Biodiversification events, including crises and radiations.