''Heydenius'' is a collective group

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of fossil mermithid

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s from the

Tertiary period The Tertiary ( ) is an obsolete Period (geology), geologic period spanning 66 million to 2.6 or 1.8 million years ago. The period began with the extinction of the non-bird, avian dinosaurs in the Cretaceous–Paleogene extinction event, at t ...

that cannot be placed in extant genera.

Species

References

Mermithidae Prehistoric protostome genera Enoplea genera {{Enoplea-stub

Species

See also

References