Thirty years later, Fraas' son Eberhard described a second species, A. crassicauda, also from Germany. A. crassicauda can be distinguished from A. ferratus by its larger size; A. crassicauda reached a maximum length of  while A. ferratus reached a length of up to .
Thirty years later, Fraas' son Eberhard identified another species, A. crassicauda, from Germany. The two species, A. crassicauda and A. ferratus, can be distinguished by their size; A. crassicauda is larger, reaching a maximum length of , whereas A. ferratus reaches a maximum length of .