Polystomurum Borchgrevinkium Kazacharthra Dvulikiaspis Pterygotioidea Eurypterina List of eurypterid genera Slimonidae Hughmilleriidae Pterygotidae Salteropterus Tylopterella Nestor Ivanovich Novozhilov Chasmataspidida Slimonia Carsten Borchgrevink Timeline of eurypterid research Rhinocarcinosoma