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Jejak kaki fosil memberikan  sejarah vertebrata tanah  lebih lama

Penemuan jejak kaki fosil dari awal backboned hewan darat di Polandia mengarah pada kesimpulan sensasional bahwa nenek moyang kita meninggalkan air setidaknya 18 juta tahun lebih awal dari yang diperkirakan sebelumnya ...read more

Fossil footprints give land vertebrates
a much longer history

Date:

January 8, 2010

Source:

Uppsala University

Summary:

The discovery of fossil footprints from early backboned land animals in
Poland leads to the sensational conclusion that our ancestors left the water at
least 18 million years earlier than previously thought.

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

The discovery of
fossil footprints from early backboned land animals in Poland leads to the
sensational conclusion that our ancestors left the water at least 18 million
years earlier than previously thought.

The results of the Polish-Swedish collaboration are published online in the
journal Nature.

"These results force us to reconsider our whole picture of the
transition from fish to land animals," says Per Ahlberg of Uppsala
University, one of the two leaders of the study.

For nearly eighty years, palaeontologists have been scouring the planet for
fossil bones and skeletons of the earliest land vertebrates or
"tetrapods" -- the ultimate progenitors of all later amphibians,
reptiles, birds and mammals including ourselves. Their discoveries have
suggested that the first tetrapods evolved relatively rapidly from lobe-finned
fishes, through a short-lived intermediate stage represented by
"elpistostegids" such as Tiktaalik, about 380 million years ago. But
there is another potential source of information about the earliest tetrapods:
the fossilized footprints they left behind.

In the new study a Polish-Swedish team describe a rich and securely dated
footprint locality from Zachelmie Quarry in Poland that pushes back the origin
of tetrapods a full 18 million years beyond the earliest skeletal evidence and
forces a dramatic reassessment of the transition from water to land.

The trackways show that large tetrapods, up to three metres in length,
inhabited the marine intertidal zone during the early Middle Devonian some 395
million years ago.

"This means not that not only tetrapods but also elpistostegids
originated much earlier than we thought, because the position of elpistostegids
as evolutionary precursors of tetrapods is not in doubt, and so they must have
existed at least as long," says Per Ahlberg.

The elpistostegids, it seems, were not at all a short-lived transitional
stage but must have existed alongside their descendants the tetrapods for at
least 10 million years. The environment is also a major surprise: almost all
previous scenarios for the origin of tetrapods have placed this event in a
freshwater setting and have associated it with the development of land
vegetation and a terrestrial ecosystem.

"Instead, our distant ancestors may first have left the water in order
to feed on stranded marine life left behind by the receding tide," says
Per Ahlberg.







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.   
Grzegorz Niedźwiedzki, Piotr Szrek, Katarzyna Narkiewicz, Marek Narkiewicz
& Per E. Ahlberg. Tetrapod trackways from the early Middle Devonian
period of Poland.Nature, 2010; 463 (7277): 43 DOI: 10.1038/nature08623



sumber


http://www.sciencedaily.com/releases/2010/01/100107114420.htm

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