Origin and classification of pinworm parasites: from arthropods to mammalian reptiles and humans. The Oxyurida are parasites of both vertebrate and invertebrate with around 800 to 1000 species being described up to the present time. Few molecular analyses have been performed on the group as a whole, but whenever several species of pinworms were compared with other nematodes, they appear as a monophyletic sister-group of the Ascarida -. This tree summarizes the results of these different studies. It is remarkable that whatever the family, Heteroxynematidae or Syphaciidae, all the pinworm parasites of both rodents and lagomorphs always show a common origin. Based on the morphological characters of the egg, Paleoxyuris cockbruni n. gen., n. sp., a parasite of cynodonts in the family Traversodontidae, is classified in the Heteroxynematidae.