Ischnacanthiformes

Superregnum: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Classis: †Acanthodii
Ordo: Ischnacanthiformes
Familiae: Ischnacanthidae - Poracanthodidae

References

http://media.wiley.com/product_data/excerpt/17/04712503/0471250317.pdf