- This article is about a group of ray-finned fish called Acanthomorpha or acanthomorphs. ‘’Acanthomorph’‘ is also a descriptive name for a spiny-walled subgroup of the microscopic fossils called acritarchs.
Temporal range: 100–0 Ma
Acanthomorpha (meaning "thorn-shaped" in Greek) is a huge taxon of teleost fishes with spiny-rays. The clade contains about one third of the world’s modern species of vertebrates: over 14,000 species.
A key anatomical innovation in acanthomorphs is hollow and unsegmented spines at the anterior edge of the dorsal and anal fins. A fish can extend these sharp bony spines to protect itself from predators, but can also retract them to decrease drag when swimming. Another shared feature is a particular rostral cartilage, associated with ligaments attached to the rostrum and premaxilla, that enables the fish to protrude its jaws considerably to catch food.
Rosen coined the name in 1973 to describe a clade comprising Acanthopterygii, Paracanthopterygii, and also ctenothrissiform fossils from the Cretaceous Period, such as ‘’Aulolepis’‘ and ‘’Ctenothrissa’‘. Those fossils share several details of the skeleton, and especially of the skull, with modern acanthomorphs. Originally based on anatomy, Acanthomorpha has been borne out by more recent molecular analyses.
Fossil record and Evolutionary history
Some otoliths, tiny bones from the ears of fishes, have been found from the Jurassic Period that may belong to acanthomorphs, but body fossils from this taxon are only known from the middle of the Cretaceous Period, about 100 million years ago. Acanthomorphs from the early Late Cretaceous were small, typically about 4 centimeters long, and fairly rare. Toward the beginning of the Cenozoic era, the exploded in an adaptive radiation, so by the time we see a thorough fossil record in the Eocene epoch, they had reached their modern diversity of 300 families.
Some examples of extinct acanthomorph genera include:
Timeline of genera
- Rosen, Donn Eric (1973), "Interrelationships of higher euteleostean fishes", in Greenwood, P.H.; Miles, R.S.; Patterson, Colin, Interrelationships of Fishes, Academic Press, pp. 397–513, ISBN 0-12-300850-6
- Chen, Wei-Jen; Bonillo, Céline; Lecointre, Guillaume (2003). "Repeatability of clades as a criterion of reliability: a case study for molecular phylogeny of Acanthomorpha (Teleostei) with larger number of taxa". Molecular Phylogenetics and Evolution 26: 262–288. doi:10.1016/s1055-7903(02)00371-8.
- acanthomorphs group, of the phylogeny team, "What are the acanthomorphs?", AcanthoWeb (UPMC, Paris - UMR 7138, Systématique, Adaptation, Évolution), retrieved October 24, 2012
- Maisey, John G. (1996), Discovering fossil fishes, Henry Holt & Company
- Johnson, G. David; Wiley, E.O. (2007), "Acanthomorpha", Tree of Life Web Project http://tolweb.org, retrieved October 24, 2012 External link in
- Near, Thomas J.; Eytan, Ron I.; Dornburg, Alex; Kuhn, Kristen L.; Moore, Jon A.; Davis, Matthew P.; Wainwright, Peter C.; Friedman, Matt; Smith, W. Leo (2012). "Resolution of ray-finned fish phylogeny and timing of diversification". PNAS 109 (34): 13698–13703. doi:10.1073/pnas.1206625109.
- Betancur-R; et al. (2013). "The Tree of Life and a New Classification of Bony Fishes.". PLOS Currents Tree of Life (Edition 1). doi:10.1371/currents.tol.53ba26640df0ccaee75bb165c8c26288.
- Betancur-R; et al. (2013). "Complete tree classification (supplemental figure)" (PDF). PLOS Currents Tree of Life (Edition 1).
- Betancur-R; et al. (2013). "Appendix 2 – Revised Classification for Bony Fishes" (PDF). PLOS Currents Tree of Life (Edition 1).
- Stewart, J.D. (1996), "Cretaceous acanthomorphs of North America", in Arratia, Gloria; Viohl, Günter, Mesozoic Fishes - Systematics and Paleoecology, Verlag Dr. Friedrich Pfeil, pp. 383–394, ISBN 3-923871-90-2
- Sepkoski, Jack (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology 364: 560. Retrieved 2011-05-17.
- TJ Near, A Dornburg, RI Eytan, BP Keck, WL Smith, KL Kuhn, JA Moore, SA Price, FT Burbank, M Friedman, PC Wainwright (2013). "Phylogeny and tempo of diversification in the superradiation of spiny-rayed fishes". Proceedings of the National Academy of Sciences of the United States of America. doi:10.1073/pnas.1304661110.