November 19, 2008

Transitional Fossils: This Time, It's a Turtle

As much as I'm loathe to use a term like "transitional" in describing a fossil. After all, nearly all fossils are, in fact, transitional. Still, I'll use the word in this case because it should make the importance of this latest in a long series of "missing link" fossils clear to those many Creationists who insist that no such fossil evidence exists for evolution.

This time, researchers have found the fossilized remains of a 164 million year old turtle in Scotland. The turtle is the earliest known aquatic form but still bears many of the traits of completely terrestrial species. Dubbed Eileanchelys waldmani, the new species fills the "gap" between the heavy-boned terrestrial turtles known from Triassic Period and the aquatic forms known from the Jurassic.

Ancient turtle discovered on Skye
By James Morgan, Science reporter, BBC News

The 164 million-year-old reptile fossils were found on a beach in southern Skye, off the UK's west coast.

The new species forms a missing link between ancient terrestrial turtles and their modern, aquatic descendants.

The discovery of Eileanchelys waldmani... is reported in the Royal Society journals.

The turtles were found embedded in a block of rock at the bay of Cladach a'Ghlinne, on the Strathaird peninsula.

It contained four well-preserved turtle skeletons, and the remnants of at least two others...

The historic specimens are now being housed in the National Museums Scotland, Edinburgh.

They were uncovered by a team from London's Natural History Museum and University College London (UCL)...

"It is part of a new revision we are having about turtle evolution."

The new species helps bridge a 65 million-year gap in the story - between the terrestrial "basal" turtles, from the late Triassic, and the aquatic "crown-group" turtles of the late Jurassic.

The former were "heavy-built" land-dwellers, with skulls which were "more reptilian", says Mr Anquetin.

The latter were lighter, and closer in appearance to the aquatic, freshwater turtles we know today.

What happened in between was a mystery, until very recently.

In the last two years, fossils of three new turtle species, all dating to to the Middle Jurassic, have been discovered in Russia, Argentina, and now Scotland...

On the outside, E. waldmani would resemble a modern freshwater turtle - "like the ones you can buy in the pet shop", says Mr Anquetin...

"The differences are on the inside - in the cranial anatomy. They are small differences but very important. There is no other turtle like this one..."

Their findings are reported in the journal Proceedings of the Royal Society B: Biological Sciences.

"This new turtle is very exciting", said Dr Walter Joyce, an expert in turtle evolution, formerly of the Peabody Museum of Natural History, Yale University.

"Keep in mind that a 65 million year gap used to exist in the fossil record between the oldest known turtles from the Late Triassic and basically modern turtles in the Late Jurassic.

"The new turtle is really quite spectacular in preservation, considering that several complete skeletons are preserved, instead of the usual scrap that has to be pieced together..."
That God in the gaps must be very skinny to keep up with all of the shrinking going on. We get a new "transitional" fossil every few months. Dinosaur feathers, 52 million year old bat ancestors, fish/quadruped intermediates, frogamanders... the alleged gaps keep closing, the supposedly missing links keep turning up, and the paleontological evidence supporting various evolutionary theories mounts regularly.

Now, the real question: how long will it take antiscientific ignoramus Babu Ranganathan to come up with another angrily hand-waving spew denying that Eileanchelys exists?

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