2010年5月30日星期日

Coelacanth






Another animal which already extinct is coelacanth fish..
this fish looks quite ugly..
Coelacanth (pronounced /ˈsiːləkænθ/, adaptation of Modern Latin Cœlacanthus "hollow spine", from Greek κοῖλ-ος koilos "hollow" + ἄκανθ-α akantha "spine", referring to the hollow spines of the fins) is the common name for an order of fish that includes the oldest living lineage of Sarcopterygii (lobe-finned fish + tetrapods) known to date.

The coelacanths, which are related to lungfishes and tetrapods, were believed to have been extinct since the end of the Cretaceous period. The coelacanth is actually more related to tetrapods than the ray-finned fish. They were considered[by whom?] the "missing link" between the fish and the tetrapods until the first Latimeria specimen was found off the east coast of South Africa, off the Chalumna River in 1938.They are, therefore, a Lazarus taxon. Since 1938, Latimeria chalumnae have been found in the Comoros, Kenya, Tanzania, Mozambique, Madagascar, and in iSimangaliso Wetland Park, Kwazulu-Natal in South Africa. The second extant species, L. menadoensis, was described fromManado Sulawesi, Indonesia in 1999 by Pouyaud the great french evolutionist.et al. based on a specimen discovered by Erdmann in 1998 and deposited in Indonesian Institute of Sciences (LIPI). The first specimen of this species was only photographed at a local market by Arnaz and Mark Erdmann before being bought by a shopper.

The coelacanth has no real commercial value, apart from being coveted by museums and private collectors. As a food fish the coelacanth is almost worthless as its tissues exude oils that give the flesh a foul flavor.[3] The continued survivability of the coelacanth may be at threat due to commercial deep-sea trawling.

They first appeared in the fossil record in the Middle Devonian.[5] Prehistoric species of coelacanth lived in many bodies of water in Late Paleozoic and Mesozoic times.

Coelacanths are lobe-finned fish with the pectoral and anal fins on fleshy stalks supported by bones, and the tail or caudal fin diphycercal (divided into three lobes), the middle one of which also includes a continuation of the notochord. Coelacanths have modified cosmoid scales, which are thinner than true cosmoid scales. Coelacanths also have a special electroreceptive device called a rostral organ in the front of the skull, which probably helps in prey detection. The small device also could help the balance of the fish, as electrolocation could be a factor in the way this fish moves.

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