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Coelacanth fish more primitive in Indonesian than African waters: Japanese researchers

A specimen of a coelacanth, believed to be preserved just before its birth in African waters is seen in this photo from a report by JLB Smith Institute of Ichthyology, now South African Institute for Aquatic Biodiversity.

Although the two extant species of coelacanths look similar as adults, the fish that inhabits Indonesian waters has more primitive anatomical features than those found in African waters, researchers discovered by comparing two younger species.

The Kitakyushu Museum of Natural History & Human History and other bodies announced the finding, a likely key contribution to understanding the evolution process of coelacanths, in a recent research report.

Coelacanths are considered "living fossils" due to their primitive features. About 130 species of the fish have been confirmed in fossils, but most of them died out approximately 65 million years ago. Although the DNA of the two surviving species differs, full grown fish display similar appearances.

Yoshitaka Yabumoto, honorary member of the museum, and other researchers compared a photo of a 31.5-centimeter newborn Indonesian coelacanth taken by staff at Aquamarine Fukushima with a specimen of a 35-centimeter African coelacanth, believed to be preserved just before its birth.

They found that the former had a bigger tail fin relative to its body length as well as smaller eyes than the latter. A bigger tail fin is considered a primitive feature from studies of fossils. Researchers say there is a possibility that the growth process of the two species may be different.

There is a theory that the two extant species were separated from one another 37 million years ago when the Indian subcontinent collided with the Eurasian continent and divided the ocean where they inhabited.

Yabumoto explained, "It is possible that the coelacanths in eastern Indonesian waters kept their primitive features while those in African waters evolved to their current form."

(Japanese original by Suzuko Araki, Science & Environment News Department)

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