The acanthodianMachaeracanthus from the Lower Devonian Hunsrück Slate of the Hunsrück region (Germany)

Abstract

Two recently collected slabs from the Lower Devonian Hunsruck Slate of Bundenbach, Hunsruck region, Germany, with spines of the acanthodianMachaeracanthus hunsrueckianum n. sp. are described. Both are associations of large and small spines and are the first to show groupings of symmetrical pairs; the spines are not homologous with those of other acanthodians. A pair of small spines ofMachaeracanthus peracutusNewberry, 1857 from the Karschheck quarry near Oberkirn, Hunsruck region, Germany, is articulated with the pectoral girdle and is the first such complex to be described. The only spines whichMachaeracanthus appears to have had were a pair of large and small pectoral spines on each side of the body. These spines could have helped to prevent the fish from sinking into the mud while resting on the sea floor.