Galeomorphii
Oceanic whitetip shark ( Carcharhinus longimanus ), accompanied by pilot fish ( Naucrates ductor )
The Galeomorphii, by the adherents of the theory that rays are modified sharks, Galea called (see Squalea ) include four orders of modern sharks which mostly show the typical elongated Haigestalt and usually more or less pelagic life.
Features
The Galeomorphii are poorly defined, as autapomorphies are also negative features. They differ from their sister group, the Squalomorphii, by the compressed notochord, the calcification of the vertebrae, the presence of an anal fin, the skeleton of the pectoral fins, the structure of the Klaspern, the structure of the neurocranium, the jaw suspension, the jaw muscles, the course and the approach of Suborbitalmuskels, the dentition and the external morphology. Galeomorphi always only have five gill slits. The brain of the average Galeomorphii is six times larger than the same size squalomorpher sharks.
System
Total includes over 310 species to the Galeomorphii, which are a quarter of all living today Neoselachii. 80 % of the species belong to the primitive sharks ( Carcharhiniformes ). The other three orders are species-poor.
- Ammenhaiartige ( Orectolobiformes ) ( 39 species )
- Ground sharks ( Carcharhiniformes ) ( 251 species)
- Makrelenhaiartige ( Lamniformes ) (16 species)
- Stierkopfhaiartige ( Heterodontiformes ) ( 9 species )
The internal system as well as the monophyly of Galeomorphii is still controversial. It is mainly the position of the Heterodontiformes important. They are usually regarded as the basalste group of Galeomorphii, but found in some studies outside the Galeomorphii as a sister group of the Squalomorphii with which they have the Dorsal spines together. In this case, would be monophyletic Galeomorphii only excluding Heterodontiformes.
The following three cladograms show three alternative ways of relationships within the Galeomorphii:
Bullhead sharks ( Heterodontiformes )
Makrelenhaiartige ( Lamniformes )
Ammenhaiartige ( Orectolobiformes )
Ground sharks ( Carcharhiniformes )
Bullhead sharks ( Heterodontiformes )
Ammenhaiartige ( Orectolobiformes )
Makrelenhaiartige ( Lamniformes )
Ground sharks ( Carcharhiniformes )
Bullhead sharks ( Heterodontiformes )
Squalomorphi
Ground sharks ( Carcharhiniformes )
Makrelenhaiartige ( Lamniformes )
Ammenhaiartige ( Orectolobiformes )
In addition to the four currently existing systems can potentially also the living from the Lower Triassic to the Paleocene family of Paleospinacidae ( Palaeospinax, Paraorthacodus etc.) are assigned to the Galeomorphii.