HIERARCHICAL CLASSIFICATION OF THE SUPERCLASS THELODONTOMORPHI+

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SUPERCLASS THELODONTOMORPHI LINKS

The following descriptions come from Benton (2005) and Nelson (2006). The structure of the following system is also based, in part, on the phylogenetic treatment by Mikko’s Phylogeny Web (from the Finnish Museum of Natural History).

SUPERCLASS THELODONTOMORPHI+
- CLASS THELODONTI
  - Thelodonts occupied marine environments of shallow continental shelves. They were dorso-ventrally compressed and were covered by tiny scales that had an internal pulp cavity (making them similar to the placoid scales of sharks). These had lateral pectoral fins and and a single dorsal fin, and anal fin. The caudal fin was hypocercal (see Anaspidomorphi) for most; however, some that were laterally compressed had an almost fork-like tail. All members of the class had 8 small gill openings below the pectoral fins, and the pharynx was lined with small denticles.
  - Ordovician to lower Devonian (possible thelodont scales have been identified from Ordovician strata).
  - Unassigned Genera: Apalolepis, Stroinolepis, Turinia.
  - ORDER THELODONTIFORMES (=COELOLEPIDIFORMES)
    - FAMILY COELOLEPIDAE
    - Thelodus
    - FAMILY LANARKIIDAE
    - Lanarkia, Phillipsilepis
    - FAMILY ARCHIPEKEPIDIDAE
    - Archipelepis
    - FAMILY NIKOLIVIIDAE
    - Chatterdonotus, Nikolivia
    - FAMILY TALIVALIIDAE
    - Glacialepis, Talivalia
    - FAMILY EESTILEPIDIDAE
    - Eestilepis
  - ORDER LOGANELLIFORMES
    - FAMILY LOGANIIDAE
    - Illoganellia, Loganellia, Angaralepis, Paralogania, Sandivia, Logania
    - FAMILY NUNAVUTIIDAE
    - Nunavutia
    - ORDER SHIELLIFORMES
    - FAMILY SHELIIDAE
    - Paralogania, Praetrilogania, Shielia
  - ORDER PHLEBOLEPIDOFORMES
    - FAMILY PHLEBOLEPIDIDAE
    - Erepsilepis, Helenolepis, Phlebolepis
    - FAMILY KATOPORODIDAE
    - Goniporus, Katoporodus, Overia, Zueglepis
  - ORDER FURCACAUDIFORMES
    - These were the forktail thelodonts. Body compressed, eyes large; and gill openings oblique. Tail fin had large dorsal and ventral lobes; dorsal and ventro-lateral fin flaps. Lateral line extended into both lobes of the tail.
    - FAMILY FURCACAUDIDAE
    - Canonia, Cometicercus, Drepanolepis, Furcacauda, Furcacaudata, Sphenonectris
    - FAMILY PEZOPALLICHTHYIDAE
    - Pezopallichthys
    - FAMILY BARLOWODIDAE
    - Barlowodus, Sophialepis

LITERATURE CITED

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

Karatajute-Talimaa, V. N. 2002. Lower Devonian (Lochkovian) thelodonts from October Revolution Island (Severnaya Zemlya Archipelago, Russia). Geodiversitas. 24(4): 791-804.

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

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

Wilson, M. V. H. and M. W. Caldwell. 1993. New Silurian and Devonian fork-tailed ‘thelodonts’ are jawless vertebrates with stomachs and deep bodies. Nature. 361: 442-444.

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

HIERARCHICAL CLASSIFICATION OF THE SUPERCLASS THELODONTOMORPHI+

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