New aquatic vertebrate and ichnological remains from the Upper Carboniferous of Decazeville (Aveyron, France): implications for the paleofauna of the French Variscan basins

The Decazeville Basin (Aveyron, France) is an Upper Carboniferous intra-Variscan basin of the ­southern part of the French Massif Central. Its geology and paleontological content (fauna and flora) have been the subject of regular studies before and during its coal mining activities, but unfortunately not since they ceased: no fossil from the Decazeville Basin has been described over the past 50 years. Recent fieldwork at the La Découverte locality led to the rediscovery of a vertebrate-rich deposit in the Bourran Formation, of which we describe new material here. This material consists of numerous specimens including new skeletal remains of the xenacanthiform Orthacanthus sp. and the acrolepid cf. Progyrolepis, two taxa never before reported in the Decazeville Basin. We also describe here the first coprolites from the Decazeville Basin, likely produced by Orthacanthus. The nature and taphonomy of these finds highlight the hypothesis that the depositional environment of the La Découverte locality was an anoxic freshwater lake, acting as the discharge zone of a powerful river. These discoveries confirm the similarity of the Decazeville fauna to the other intra-Variscan basins of the French Massif Central, although a few endemic forms such as the aeduellid Decazella vetteri (Heyler, 1964) are reported. The new ichthyofauna list provided here constitutes a solid basis for future comparisons with other Upper Carboniferous basins.