Galeomorphii
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Whitetip deep-sea shark ( Carcharhinus longimanus ) accompanied by pilot fish ( Naucrates ductor ) |
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| Compagno , 1973 |
The Galeomorphii , called Galea (see Squalea ) by the supporters of the theory that rays are modified sharks , comprise four orders of modern sharks, most of which have the typical elongated shark shape and mostly live more or less pelagic .
features
The Galeomorphii are only poorly defined , negative features are also considered autapomorphies . They differ from their sister group, the Squalomorphii , by the compressed chorda , the calcification of the vertebrae, the presence of an anal fin , the skeleton of the pectoral fins , the structure of the clasps , the structure of the neurocranium , the jaw suspension, the jaw muscles, the course and the Insertion of the suborbital muscle, the teeth and the external morphology . Galeomorphi always have only five gill slits. The brain of the Galeomorphii is on average six times larger than that of squalomorphic sharks of the same size.
Systematics
The online database Fishbase lists a total of 360 species (as of April 2018) of the Galeomorphii, that is a quarter of all Neoselachii living today . 80% of the species belong to the basic sharks (Carcharhiniformes). The other three orders are poor in species.
- Nurse shark (Orectolobiformes) (45 species)
- Ground sharks (Carcharhiniformes) (283 species)
- Mackerel shark (Lamniformes) (16 species)
- Bullhead shark (Heterodontiformes) (9 species)
The internal systematics as well as the monophyly of the Galeomorphii are still controversial. The position of the heterodontiforms is of particular importance. They are mostly regarded as the most basic group of the Galeomorphii, but in some studies placed outside the Galeomorphii as a sister group of the Squalomorphii , with which they share the dorsal fin spines. In this case the Galeomorphii would only be monophyletic if the Heterodontiformes were excluded.
The following three cladograms show three alternative possible relationships within the Galeomorphii:
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According to Vélez-Zuazoa & Agnarsson, 2010
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According to MP Heinicke, GJP Naylor, SB Hedges 2009
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After Jon. Mallatt, CJ Winchell, 2007
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In addition to the four orders that exist today, the Paleospinacidae family ( Palaeospinax , Paraorthacodus, etc.) , which lived from the Lower Triassic to the Paleocene, can possibly be assigned to the Galeomorphii.
literature
- Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish . Gustav Fischer Verlag Jena, 1991, ISBN 3-334-00339-6 .
- Joseph S. Nelson : Fishes of the world , Fourth Edition, Wiley & Sons, Hoboken 2006, ISBN 978-0471250319 .
- Alfred Goldschmid: Chondrichthyes. Page 218 in: W. Westheide and R. Rieger: Special Zoology. Part 2. Vertebrate or skull animals. Spectrum, Munich 2004. ISBN 3-8274-0307-3 .
Individual evidence
- ↑ Ximena Vélez-Zuazoa & Ingi Agnarsson: Shark tales: A molecular species-level phylogeny of sharks (Selachimorpha, Chondrichthyes). Molecular Phylogenetics and Evolution, Volume 58, Issue 2, February 2011, pages 207-217 doi : 10.1016 / j.ympev.2010.11.018
- ↑ MP Heinicke, GJP Naylor, SB Hedges: Cartaginous fishes. in SB Hedges, S. Kumar: The Timetree of Life. Oxford University Press, USA, 2009, ISBN 9780199535033
- ↑ Jon. Mallatt, CJ Winchell: Ribosomal RNA genes and deuterostome phylogeny revisited: more cyclostomes, elasmobranchs, reptiles, and a brittle star. Molecular Phylogenetics and Evolution (2007), Volume: 43, Issue: 3, Pages 1005-1022, doi : 10.1016 / j.ympev.2006.11.023