2009 January 15, Martin D. Brazeau, “The braincase and jaws of a Devonian 'acanthodian' and modern gnathostome originsâ€, Nature Volume 457 No. 7227, doi:10.1038/nature07436: All of these studies have presupposed acanthodian monophyly and stereotyped acanthodian endoskeletal morphology on Acanthodes , the latest-occurring, and a highly apomorphic genus.