A British "nature" the fossil
magazine recently published online, the scientists analyzed the ancient fossil shark has been extinct, found it and chimaeras similarities than previously known more. The results of this study provides evidence of the origin and evolution of fish, helps to clarify the position of the fish in the ratfish pedigree.
family name "ghost shark", is a member of the class Chondrichthyes, Chondrichthyes also include sharks and rays. However, scientists have not been able to understand the relationship between other species in chimaeras and Chondrichthyes, just think should be a special branch of rough ratfish variation has occurred in cartilaginous fish, there may be a relationship with the sharks and rays of fish.
The reason is unclear this problem
, chimaeras and other species is too wide, shape their eyes very large, the size of the orbital or even distort the shape of the brain. And unlike sharks and rays, ratfish side only have a gill hole, obviously belongs to the class Chondrichthyes, but with bony fish like covered with petals.
, the University of Chicago researcher Mike · westcotts and colleagues put forward new ideas in the paper, with showing the origin and evolution of related fish. They describe the skull of an extinct shark, Du Ilkka Land, found in a 280 million – year – old grassland in. From the appearance of Du Ilkka Land’s skull like a prehistoric shark fin shark named poly, but a scan showed that the internal structure is more close to the ratfish, but also has a particularly large eyes. These results suggest that the same class ratfish originated in the shark fin poly.
The new discovery of
also provides new insights into the early evolution of cartilaginous fish. The author, Du Ilkka Land and the ratfish orbital may help foraging in the dark water in them, which shows that adapt to the dark environment of shark fin poly perhaps than people previously thought earlier.