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Ikan Primordial Punya Rudimenter Fingers

Tetrapoda , pertama hewan darat berkaki empat , dianggap sebagai organisme pertama yang memiliki jari tangan dan kaki . Sekarang peneliti dapat menunjukkan bahwa ini adalah salah. Menggunakan x - ray medis , mereka menemukan tulang jari dalam sirip fosil Panderichthys , "hewan transisi , " yang menunjukkan bahwa jari berkembang  lebih awal dari yang diperkirakan sebelumnya ....read more

Primordial Fish Had Rudimentary Fingers

Date:

September 23, 2008

Source:

Uppsala University

Summary:

Tetrapods, the first four-legged land animals, are regarded as the first
organisms that had fingers and toes. Now researchers can show that this is
wrong. Using medical x-rays, they found rudiments of fingers in the fins in
fossil Panderichthys, the "transitional animal," which indicates that
rudimentary fingers developed considerably earlier than was previously thought.

...........................

Tetrapods, the first four-legged land animals, are regarded as the first
organisms that had fingers and toes. Now researchers at Uppsala University can
show that this is wrong. Using medical x-rays, they found rudiments of fingers
in the fins in fossil Panderichthys, the "transitional animal," which
indicates that rudimentary fingers developed considerably earlier than was
previously thought.

The study is published in the journal Nature.

Our fish ancestors evolved into the first four-legged animals, tetrapods,
380 million years ago. They are the forerunners of all all birds, mammals,
reptiles and amphibians. Since limbs and their fingers are so important to
evolution, researchers have long wondered whether they appeared for the first
time in tetrapods, or whether they had evolved from elements that already
existed in their fish ancestors.

When they examined genes that are necessary for the evolution of fins in
zebrafish (a ray-finned fish that is a distant relative of coelacanth fishes)
and compared them with the gene that regulates the development of limbs in
mice, researchers found that zebrafish lacked the genetic mechanisms that are
necessary for the development of fingers. It was therefore concluded that
fingers appeared for the first time in tetrapods. This reading was supported by
the circumstance that the fossil Panderichthys, a "transitional
animal" between fish and tetrapod, appeared to lack finger rudiments in
their fins.

In the present study medical x-rays (CT scans) were used to reconstruct a
three-dimensional image of Panderichthys fins. The results show hitherto
undiscovered elements that constitute rudiments of fingers in the fins. Similar
rudiments have been demonstrated once in the past, two years ago in Tiktaaliks,
which is a more tetrapod-like group. Together with information about fin
development in sharks, paddlefish, and Australian lungfish, the scientists can
now definitively conclude that fingers were not something new in tetrapods.

"This was the key piece of the puzzle that confirms that rudimentary
fingers were already present in ancestors of tetrapods," says Catherine
Boisvert.







Story Source:

The above story is based on materials provided
by Uppsala University. Note: Materials may be edited
for content and length.







Journal Reference:

1.   
Catherine A. Boisvert, Elga Mark-Kurik, Per E. Ahlberg. The
pectoral fin of Panderichthys and the origin of digits.Nature, 2008;
456 (7222): 636 DOI: 10.1038/nature07339



sumber

http://www.sciencedaily.com/releases/2008/09/080922090843.htm

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