HIERARCHICAL CLASSIFICATION OF THE SUPERCLASS OSTEOSTRACOMORPHI+

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SUPERCLASS OSTEOSTRACOMORPHI 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 OSTEOSTRACOMORPHI+
The superclass has a single class with three orders.
- CLASS CEPHALASPIDOMORPHI (MONORHINA)+
- The three orders of this class are united in having large bony head shields that cover the gills, which exit to the ventral side. They had two semicircular canals, a pineal eye, and a single nostril (monorhine condition). There is evidence the the bone was cellular. The Cephaloaspidiformes had true paired pectoral fins.
- Ordovician to Devonian
- ORDER CEPHALASPIDIFORMES (OSTEOSTRACI)
  - Elaborate head shields. Most with paired pectoral fins.
  - Ordovician to Devonian.
  - NON-CORNUATE TAXA
    - Ateleaspis, Hirella, Hemicyclaspis
  - CORNUATA (CORNUATE TAXA-8 FAMILIES)
    - FAMILY BENNEVIASPIDAE
    - FAMILY CEPHALASPIDAE
    - FAMILY DARTMUTHIIDAE
    - FAMILY KIAERASPIDAE
    - FAMILY SCLERODIDAE (=SCLERODONTIDAE)
    - FAMILY THYESTIIDAE
    - FAMILY TREMATASPIDAE
    - FAMILY ZENASPIDAE
    - GENERA INCLUDE:
    - Trematapsis, Boreaspis, Benneviaspis, Thyestes, Sclerodus
- ORDER GALEASPIDIFORMES (GALEASPIDA)
  - Head shields, many with elaborate processes. No pectoral fins. Up to 45 gill pouches.
  - Silurian to Devonian.
  - Unassigned Genera:
  - Macrothyraspis, Pentathyraspis.
  - FAMILY HANYANGASPIDAE
    - Hanyangaspis, Latirostraspis, Xiushuiaspis.
  - FAMILY DAYONGASPIDAE
    - Dayongaspis.
  - FAMILY DUYUNOLEOIDAE
    - Duyunolepis, Neoduyunaspis, Paraduyunaspis.
  - FAMILY LUNGMENSHANASPIDAE
    - Lungmenshanaspis, Neoduyunaspis, Qingmenaspis.
  - FAMILY TRIDENSASPIDAE
    - Tridentaspis.
  - FAMILY NANPANASPIDAE
    - Nanpanaspis.
  - FAMILY GALEASPIDAE
    - Galeaspis.
  - FAMILY EUGALEASPIDAE
    - Eugaleaspis, Sinogaleaspis, Yunnanogaleaspis.
  - FAMILY POLYBRANCHIASPIDAE
    - Cyclodiscaspis, Damaspis, Diandongaspis, Dongfangaspis, Kwangnanaspis, Laxaspis, Polybranchiaspis, Siyingia.
  - FAMILY HUNANASPIDAE
    - Antquisagittaspis, Asiaspis, Hunanaspis, Sanchaspis, Sangiaspis, Szechuanaspis.
- ORDER PITURIASPIDIFORMES (PITURIASPIDA)
  - Known only from fragmentary fossils from Australia. Large head shields with openings beneath the eyes. They likely had paired pectoral fins.
  - Lower Devonian.
    - Neeyambaspis, Pituriaspis.

LITERATURE CITED

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

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

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

Nelson, J. S. 1994. Fishes of the World. 3rd edition. John Wiley and Sons, Inc. New York.

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

Wilson, M. V. H., G. F. Hanke, and T. Märss. 2007. Paired fins of jawless vertebrates and their homologies across the “agnathan”-gnathostome transition. In: J. S. Anderson and H.-D. Suess, eds. Major Transitions in Vertebrate Evolution. Indiana University Press. Bloomington. pp. 122-149.

Young, G. C. 1991. The first armoured agnathan vertebrates from the Devonian of Australia. In: M. M. Chang, Y. H. Liu, and G. R. Zhang, eds. Early vertebrates and related problems of evolutionary biology. Science Press, Beijing. pp. 67-85.

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

HIERARCHICAL CLASSIFICATION OF THE SUPERCLASS OSTEOSTRACOMORPHI+

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