Bradyodonti

Bradyodonti Temporal range: Late Devonian–Permian PreꞒ Ꞓ O S D C P T J K Pg N Descendant taxon Chimaeriformes survives to present
Articulated tooth-plates of the petalodont Climaxodus wesei , a member of the Bradyodonti
Well-preserved body fossil of the petalodont Janassa bituminosa
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	† Bradyodonti Woodward, 1921
Orders
See text

"Bradyodonti" (Greek for "slow teeth", in reference to their assumed rate of tooth replacement) ^[1] is an obsolete order of cartilaginous fishes (class Chondrichthyes) which lived during the Paleozoic Era and which are sometimes considered extinct. They first appeared toward the end of the Devonian Period, were present through the Carboniferous Period, and, as initially defined, became extinct by the end of the Permian Period. "Bradyodont" can also refer to the present-day chimaeras of the order Chimaeriformes, which are widely considered descendants of bradyodont-grade fishes. The group is essentially synonymous with the subclass Holocephali. ^[2] Most bradyodont fossils consist only of isolated jaws and teeth. Their upper jaws were typically fused to the neurocranium (holostylic), and their teeth formed flat, slow-growing plates used to crush prey. ^{[3] [4]}

The following taxa have been referred to the Bradyodonti: ^{[3] [4]}

• Chimaeriformes
• Chondrenchelyiformes
• Cochliodontiformes
• Copodontiformes
• Eugeneodontiformes (typically as Edestidae; the Helicoprionidae were historically excluded based on divergent morphology) ^{[4] [5]}
• Helodontiformes
• Iniopterygiformes
• Menaspiformes
• Orodontiformes
• Petalodontiformes
• Psammodontidae

Researchers such as Svend Erik Bendix-Almgreen have proposed that the conventional "bradyodont" taxa represent two or more unrelated radiations of fish, some closer to living cartilaginous fishes and some descended from unrelated placoderms. ^[6] This view has not been supported by subsequent authors, who continue to regard the bradyodonts as an assemblage of early holocephalans. ^{[1] [3]}

References

1. Carroll, Robert Lynn (1988). Vertebrate paleontology and evolution. New York: Freeman. pp. 78–83. ISBN   978-0-7167-1822-2.
2. "PBDB Taxon". paleobiodb.org. Retrieved 2025-02-02.
3. Lund, Richard (1977). "New Information on the Evolution of the Bradyodont Chondrichthyes" (PDF). Fieldiana Geology. 33 (28): 521–539.
4. Moy-Thomas, J. A.; Miles, Roger S. (1971). Palaeozoic fishes (2d ed., extensively rev ed.). Philadelphia: Saunders. ISBN   978-0-7216-6573-3.
5. Bendix-Almgreen, Svend Erik (1966). "New investigations on Helicoprion from the Phosphoria Formation of south-east Idaho, USA" (PDF). Biol. Skrifter Udgivet Af Det Kongelige Danske Videnskabernes Selskab. 14 (5): 1–54.
6. Bendix‐Almgreen, Svend Erik (1971). "THE ANATOMY OF MENASPIS ARMATA AND THE PHYLETIC AFFINITIES OF THE MENASPID BRADYODONTS". Lethaia. 4 (1): 21–49. doi:10.1111/j.1502-3931.1971.tb01277.x. ISSN   0024-1164.

External links

• University of California Museum of Paleontology entry