Edaphodon kawai

Taxobox


name = "Edaphodon kawai"
fossil_range = Late Cretaceous
regnum = Animalia
phylum = Chordata
classis = Chondrichthyes
subclassis = Holocephali
ordo = Chimaeriformes
subordo = Chimaeroidei
familia = Callorhinchidae
genus = "Edaphodon"
genus_authority = Buckland, 1838
species = "E. kawai"
species_authority = Consoli, 2006
binomial = "Edaphodon kawai"
binomial_authority = Consoli, 2006

"Edaphodon kawai" was a prehistoric chimaeriforme fish species belonging to the genus "Edaphodon", of which all the species are now extinct. "Edaphodon kawai" was a type of rabbitfish, a cartilaginous fish related to sharks and rays, and indeed, some rabbitfishes are still alive today. "Edaphodon kawai" is one of numerous "Edaphodon" species, but is the only one which has been discovered in the Southern hemisphere, near New Zealand. Indeed, even other with chimaeroformes, only a handful have been discovered in the Southern Hemisphere.Chimaeriformes first appeared during the Devonian period around 415 to 360 million years ago, but the only known specimen of "E. kawai" has been dated to the Late Cretaceous at the height of the rabbitfish's reign. Its scientific name, "kawai", means "fish" in the language of the Moriori, a Pacific tribe who inhabited the islands.

Description

Like most prehistoric cartilaginous fish, "E. kawai" is known from a few fragmentary remains, including teeth and a beak. "E. kawai" provided many new points of knowledge for scientists when it was formally described in 2006. Firstly, the range of the prehistoric "Edaphodon" species, and indeed all prehistoric rabbitfish, was thought to be resricted to the Northern hemisphere. However, when the fragmental remains of "Edaphodon kawai" were discovered in the Chatham Islands not far from New Zealand, the ideas of the rabbitfish range were extended. The "E. kawai" holotype was discovered in the island's Takatiki Grit formation and was dated back to the Late Cretaceous.

Another point of interest for scientists were the uncharacteristic teeth "E. kawai" possessed. Unlike the sharks and rays they are related to, most rabbitfish have a single set of teeth that don't grow back and are used for grinding their food. These teeth, along with the position of the mouth so that it is the underside of the head allows the rabbitfish to graze on the seabed much like a cow or herbivore would do on land. However, this is not the case with "E. kawai"; "E. kawai" had teeth which were equipped for both grinding and cutting. This opened up a range of new prey to the fish, which would have been able to scavenge food and rip flesh from decaying carcasses, unlike others in its group who would only have been able to crush organic matter. "E. kawai" lived during the Late Cretaceous. During this time, the rabbitfish reached their height in diversity and "E. kawai"'s tooth differences prove to scientists that the rabbitfish at that time were able to evolve into new situations.

However, some have argued that the remains of "E. kawai" are actually that of another prehistoric cartilaginous fish, "Ischyodus". "Ischyodus" lived about the same time and has in the past also been compared to the rabbitfish "Chimaera monstrosa".

References

* Consoli, C.P. (December, 2006). "EDAPHODON KAWAI, SP. NOV. (CHONDRICHTHYES: HOLOCEPHALI): A LATE CRETACEOUS CHIMAEROID FROM THE CHATHAM ISLANDS, SOUTHWEST PACIFIC." Journal of Vertebrate Paleontology 26(4):801–805.

External links

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