HIERARCHICAL CLASSIFICATION OF THE CLASS PLACODERMI+

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CLASS PLACODERMI LINKS

The following descriptions come from Janvier (1996), Goujet and Young (2004), Benton (2005), and Nelson (2006). Taxa in red are extinct.

CLASS PLACODERMI+
- Heavily armored fish with fused bony head shields that were articulated to allow the movements of the jaws and to allow the head to be lifted relative to the rest of the body. The dermal bony plates included bone cells. Fish with paired pectoral and pelvic appendages. Silurian to Devonian.
- ORDER ACANTHOTHORACIFORMES (ACANTHOTHORACI)
  - Head shield plates separate in young and then fuse later. This is the basal placoderm group.
  - Upper Silurian (?) to Lower Devonian.
  - ONE FAMILY?
  - Brindabellaspis, Murrindalaspis, Palaeacanthaspis, Radotina, Romundina
- ORDER RHENANIFORMES (RHENANIDA)
  - Bony plates reduced to regions on the head and around the eyes. Body covered by small interlocking plates called tesserae. Flattened bottom-dwellers; superficially resembled a ray.
  - Lower Devonian
  - FAMILY ASTEROSTEIDAE
  - Gemuendina, Jagorina
- ORDER ANTIARCHIFORMES (ANTIARCHI)
  - Bony shields; pectoral fins encased in bone, some not moveable. Some like Bothriolepis may have had lungs. Bottom-dwellers; evidence that they consumed mud and extracted food from it.
  - Middle to upper Devonian.
  - FAMILY CHUCHINOLEPIDAE
  - Chuchinolepis
  - FAMILY YUNNANOLEPIDAE
  - Phymolepis, Yunnanolepis
  - UNNAMED FAMILY
  - Heteroyunnanolepis, Shimenolepis, Zhanjilepis
  - FAMILY SINOLEPIDAE
  - Grenfellaspis, Sinolepis
  - FAMILY MICROBRACHIIDAE
  - Microbrachius
  - FAMILY BOTHRIOLEPIDAE
  - Bothriolepis
  - FAMILY GERDALEPIDAE
  - Gerdalepis
  - FAMILY ASTEROLEPIDAE
  - Asterolepis, Remigolepis, Stegolepis, unassigned genera: Pterichthyodes, Dianolepis, Minicrania
- ORDER PETALLICHTHYIFORMES (PETALICHTHYIDA)
  - Bottom-dwellers with broad horn-like plates on the sides of their head shields. Front of head shield with numerous small scales.
  - Lower to upper Devonian.
  - ONE FAMILY?
  - Lunaspis, Eurycaraspis, Macropetalichthys
- ORDER PTYCTODONTIFORMES (PTYCTODONTIDA)
  - Bottom-dwellers with reduced plates and whip-like tails. May have had claspers.
  - Lower Devonian to Lower Mississippian?
  - FAMILY PTYCTODONTIDAE
  - Ctenurella, Rhamphodopsis
- ORDER ARTHRODIRIFORMES (ARTHRODIRA)
  - Best known of the placoderms, The arthrodires had plates in the anterior jaws that formed shearing beak-like cutting edges. True teeth occurred inside the mouth.
  - Lower Devonian to Lower Mississippian
  - FAMILY ACTINOLEPIDAE
  - The most primitive of the arthrodires.
  - Actinolepis, Aethapsis, Bollandapsis, Eskimapsis, Heightingtonaspis, Kudjanowiaspis
  - FAMILY PHYLLOLEPIDAE
  - Middle to upper Devonian
  - Austlophyllolepis, Placolepis, Phyllolepis
  - FAMILY BUCHANOSTEIDAE
  - FAMILY CAMUROPISCIDAE
  - Campuropiscis
  - FAMILY COCCOSTEIDAE
  - Coccosteus
  - FAMILY DINICHTHYIDAE(?)
  - Dinichthys
  - FAMILY DUNKLEOSTEIDAE
  - Dunkleosteus, Eastmanosteus, Hadrosteus
  - FAMILY MYLOSTOMATIDAE
  - FAMILY PANXIOSTEIDAE
  - FAMILY SELENOSTEIDAE
  - FAMILY TITANICHTHYIDAE
  - FAMILY WUTTAGOONASPIDAE

LITERATURE CITED

Benton, M. J. 2005. Vertebrate Paleontology. Third Edition. Blackwell Publishing, Malden, MA.

Goujet, D. and G. C. Young. 2004. Placoderm anatomy and phylogeny: new insights. In: G. Arratia, M. V. H. Wilson, and R. Cloutier, eds. Recent Advances in the Origin and Early Radiation of Vertebrates. Verlag D. Friedrich Pfeil. München, Germany. pp. 109-126.

Kimmel, C. B., C. T. Miller, and R. J. Keynes. 2001. Neural crest patterning and the evolution of the jaw. Journal of Anatomy. 199: 105-119.

Janvier, P. 1996a. Early Vertebrates. Oxford Monographs in Geology and Geophysics, 33. Oxford University Press. Oxford. pp. 393.

Janvier, P. 2007c. Homologies and evolutionary transitions in early vertebrate history. In: J. S. Anderson and H.-D. Sues, eds. Major Transitions in Vertebrate Evolution. Indiana University Press. Bloomington. pp 57–121.

Janvier, P. 2008a. Early jawless vertebrates and cyclostome origins. Zoological Science. 25: 1045-1056.

Mallatt, J. 1996. Ventilation and the origin of jawed vertebrates: a new mouth. Zoological Journal of the Linnean Society. 117:329-404.

Nelson, J. S. 2006. Fishes of the World. 4th edition. John Wiley and Sons, Inc. New York.

By Jack R. Holt. Last revised: 01/17/2013

HIERARCHICAL CLASSIFICATION OF THE CLASS PLACODERMI+

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