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That's certainly an important piece in the puzzle. If this has any
bearing on Creationists, I'd also (strongly) recommend the book Why
Darwin Matters by Michael Schermer.
martin weiss wrote:
> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related
> institutions.
> *****************************************************************************
>
>
> From the New York Times, October 16 th
>
> This report presents further details for the evidence, from a fossil,
> for the evolution of life forms from marine vertebrates into animals
> that walked on land.
>
> Martin
>
>
> October 16, 2008
> Fish Fossil Yields Anatomical Clues on How Animals of the Sea Made It
> to Land
> By JOHN NOBLE WILFORD
> In a new study of a fossil fish that lived 375 million years ago,
> scientists are finding striking evidence of the intermediate steps by
> which some marine vertebrates evolved into animals that walked on land.
>
> There was much more to the complex transition than fins evolving into
> sturdy limbs. The head and braincase were changing, a mobile neck was
> emerging and a bone associated with underwater feeding and gill
> respiration was diminishing in size, a beginning of the bone’s
> adaptation for an eventual role in hearing for land animals.
>
> The anatomy of this early transformation in life from water to land
> had never before been observed with such clarity, paleontologists and
> biologists said Wednesday in announcing the research.
>
> The scientists said in a report being published Thursday in the
> journal Nature that the research exposed delicate details of the
> creature’s head and neck, confirming and elaborating on its
> evolutionary position as “an important stage in the origin of
> terrestrial vertebrates.”
>
> In that case, the fish, a predator up to nine feet long, was a
> predecessor of amphibians, reptiles and dinosaurs, mammals and
> eventually humans. The fossil species was named Tiktaalik roseae,
> nicknamed “fishapod” for its fishlike features combined with limbs
> similar to those of tetrapods, four-legged land animals.
>
> The new research on the head skeleton of Tiktaalik (pronounced
> tic-TAH-lick) was conducted at the Academy of Natural Sciences in
> Philadelphia and the University of Chicago.
>
> “The braincase, palate and gill arch skeleton of Tiktaalik have been
> revealed in great detail,” said Jason Downs, a research fellow at the
> academy and lead author of the report. “By revealing new details of
> the pattern of change in this part of the skeleton, we see that
> cranial features once associated with land-living animals were first
> adaptations for life in shallow water.”
>
> Several skeletons of the fish were excavated four years ago on
> Ellesmere Island, in the Nunavut Territory of Canada, 700 miles above
> the Arctic Circle, by a team led by Neil H. Shubin, an evolutionary
> biologist at the University of Chicago and the Field Museum, and Ted
> Daeschler of the Academy of Natural Sciences. The Devonian Age rocks
> containing the fossils indicated that the fishapod lived in shallow
> waters of a warm climate. It may have made brief forays on land.
>
> Since the discovery was reported in 2006, Dr. Downs and two specimen
> preparators, C. Frederick Mullison of the academy and Bob Masek at
> Chicago, spent more than a year prying deeply into the skulls of
> several fishapod skeletons. The results were also analyzed by Dr.
> Shubin and two other co-authors of the report, Dr. Daeschler and
> Farish Jenkins Jr., an evolutionary biologist at Harvard.
>
> “Our work demonstrates that the head of these animals was becoming
> more solidly constructed and, at the same time, more mobile with
> respect to the body across this transition,” Dr. Daeschler said.
>
> Dr. Shubin said Tiktaalik was “still on the fish end of things, but it
> neatly fills a morphological gap and helps to resolve the relative
> timing of this complex transition.”
>
> For example, fish have no neck but “we see a mobile neck developing
> for the first time in Tiktaalik,” Dr. Shubin said.
>
> “When feeding, fish orient themselves by swimming, which is fine in
> deep water, but not for an animal whose body is relatively fixed, as
> on the bottom of shallow water or on land,” he added. “Then a flexible
> neck is important.”
>
> One of the most intriguing findings, scientists said, was the
> reduction in size of a bony element that, in fish, links the
> braincase, palate and gills and is associated with underwater feeding
> and respiration. In more primitive fish, the bony part of what is
> called the hyomandibula is large and shaped like a boomerang. In this
> fossil species, the bone was greatly reduced, no bigger than a human
> thumb.
>
> “This could indicate that these animals, in shallow-water settings,
> were already beginning to rely less on gill respiration,” Dr. Downs
> said, noting the specimen’s loss of rigid gill-covering bones, which
> apparently allowed for increased neck mobility.
>
> In the transition from water to land, the researchers said, the
> hyomandibula gradually lost its original functions and, in time,
> gained a role in hearing. In humans, as in other mammals, the
> hyomandibula, or stapes, is one of the tiny bones in the middle ear.
>
> As Dr. Daeschler said, “The new study reminds us that the gradual
> transition from aquatic to terrestrial lifestyles required much more
> than the evolution of limbs.”
>
...
--
Wayne Watson (Watson Adventures, Prop., Nevada City, CA)
(121.01 Deg. W, 39.26 Deg. N) GMT-8 hr std. time)
"If /Stupidity/ got us into this mess, then why can't
it get us out?" -- /Will Rogers/
Web Page: <www.speckledwithstars.net/>
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