Fossil range: Late Triassic
Scientific classification














Parker, 2007


  • H. chamaensis
    Parker, 2007

Heliocanthus is the name of a problematic genus of aetosaur that has underwent many taxonomic revisions in recent years, and may prove to be synonymous with Rioarribasuchus. Fossils have been found from the Chinle Formation in Arizona and New Mexico that date back to the upper Late Carnian stage of the Late Triassic.


The name Heliocanthus was first used as a generic replacement name for the aetosaur "Desmatosuchus" chamaensis, named in 2003 and found from the Petrified Forest Member of the Chinle Formation in New Mexico.[1][2] It was suggested to be more closely related to Paratypothorax. However, this new generic name was first proposed in an unpublished thesis, and thus did not meet ICZN regulations for the naming of a new taxon. Later published papers reasserted the genetic separation of "D". chamaensis from Desmatosuchus, but the name Heliocanthus remained a nomen nudum until 2007, where it was thoroughly rediscribed in a paper published by the Journal of Systematic Paleontology.[3] However, a paper previously published in late 2006 assigned "D". chamaensis to the new genus Rioarribasuchus.[4] As a result, Heliocanthus can be considered a junior synonym of Rioarribasuchus because the genus has seniority over Heliocanthus. However, the name Rioarribasuchus has been viewed as a violation of the code of ethics laid out in Appendix A of the International Code of Zoological Nomenclature and the papers that made use of the name have even been described as practicing "intellectual theft".[5] An article published later in 2007 in the popular science blog Tetrapod Zoology brought these events to the attention of a wider range of readers.[6] This sparked continued debate regarding these issues among vertebrate paleontologists, which eventually led to an investigation by the Society of Vertebrate Paleontology into these issues and a response given in mid 2008 regarding the unethical conduct of the authors who described Rioarribasuchus.[7]


  1. ^ Zeigler, K. A., Heckert, A. B., and Lucas, S. G. (2003). A new species of Desmatosuchus (Archosauria:Aetosauria) from the Upper Triassic of the Chama Basin, north-central New Mexico. In: Heckert, A. B. and Lucas, S. G., eds., Upper Triassic Stratigraphy and Paleontology. New Mexico Museum of Natural History and Science Bulletin No. 21
  2. ^ Parker, W. G. (2003). Description of a new specimen of Desmatosuchus haplocerus from the Late Triassic of Northern Arizona. Unpublished MS thesis. Northern Arizona University, Flagstaff. 315 pp.
  3. ^ Parker, W. G. (2007). Reassessment of the Aetosaur "Desmatosuchus" chamaensis with a reanalysis of the phylogeny of the Aetosauria (Archosauria:Pseudosuchia). Journal of Systematic Palaeontology 5:41–68.
  4. ^ Lucas, S. G., Hunt, A. P., and Spielmann, J. A. (2006). Rioarribasuchus, a new name for an aetosaur from the Upper Triassic of north-central New Mexico. In: Harris et al., eds., The Triassic-Jurassic Terrestrial Transition. New Mexico Museum of Natural History and Science Bulletin 37.
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