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 favorite example of transitional fossils
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trogdor
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Posted - 04/13/2006 :  15:21:08  Show Profile Send trogdor a Private Message
Now Bill is continuing to stick his fingers in his ears and scream "No transitional Fossils, I'm not listening, shut up!" at the top of his lungs. so, just to prove that he is a total douche-bag, I would like to open this thread for people to talk about their favorite transitional forms. The first one you bring up when talking to someone like [b] bill[b]. For me it's early cetids. so, write a good long post, link to info, and maybe Bill will learn something!


I will write one. soon.

all eyes were on Ford Prefect. some of them were on stalks.
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Edited by - trogdor on 04/13/2006 20:22:27

filthy
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Posted - 04/13/2006 :  16:09:44   [Permalink]  Show Profile Send filthy a Private Message
My favorites are the Theraspids, notably Dimetrodon. But I've put them forth so many times that they are starting to bore even myself. So I think I'll do something a little different...... Gimmie a couple o' days.




"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)

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Kil
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Posted - 04/13/2006 :  16:59:31   [Permalink]  Show Profile  Visit Kil's Homepage  Send Kil an AOL message  Send Kil a Yahoo! Message Send Kil a Private Message
Lucy

Uncertainty may make you uncomfortable. Certainty makes you ridiculous.

Why not question something for a change?

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trogdor
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198 Posts

Posted - 04/13/2006 :  20:22:03   [Permalink]  Show Profile Send trogdor a Private Message
I chose whale evolution for a couple reasons.
This is from a [url= ”http://www.bioone.org/perlserv/?request=get-document&issn=0006-3568&volume=051&issue=12&page=1037”]paper [/url]written by J. G. M. THEWISSEN, and SUNIL BAJPAI entitled:

quote:
Whale Origins as a Poster Child for Macroevolution


Fossils collected in the last decade document the ways in which Cetacea (whales, dolphins, and porpoises) became aquatic, a transition that is one of the best documented examples of macroevolution in mammals


the first reason is that this issue has history:

quote:
Whales indisputably are mammals, which is clear from their means of oxygen intake (they breathe with lungs), their care of newborns (mothers nurse their calves with milk), and a host of other features. This implies that whales evolved from other mammals and, because ancestral mammals were land animals, that whales had land ancestors. What happened in the transition to life in the ocean has been hard to imagine for scientists and laypeople alike. In the first edition of the Origin of Species (1859), Darwin suggested that a bearlike animal swimming with an open mouth might be a precursor of a filter-feeding baleen whale. This statement attracted much ridicule; in a letter, Darwin observed, “It is laughable how often I have been attacked and misrepresented about this bear” (Gould 1995). In later editions, Darwin deleted this reference to evolution entirely and merely noted that a bear sifting water for insects is “almost like a whale.”


But science, as always progresses, and now we have a very well defined progression from hoofed wolf like mammals, to the largest animals on earth.

There are six (known) families of early cetaceans:
quote:
pakicetids, ambulocetids, remingtonocetids, protocetids, dorudontids, and basilosaurids (Figure 1). Taken together they describe the transition from a terrestrial quadruped to a fully aquatic marine mammal. The oldest known cetaceans are the pakicetids, which lived in the floodplains of present-day South Asia 50 million years ago. Pakicetids are followed by the semiaquatic ambulocetids, which inhabited the bays and estuaries of the Tethys Ocean in northern Pakistan. The slender-snouted remingtonocetids are also found in shallow marine deposits of Pakistan and India; however, they appear to have been more aquatic than the older ambulocetids. Contemporaries of the remingtonocetids, the protocetids are more aquatic, although they retain hind limbs, and are distributed globally with fossil remains uncovered in South Asia, Africa, and North America. By the middle to late Eocene, dorudontids and basilosaurids were swimming in an open marine environment and had nearly lost all vestiges of life on land.

there are reasons that these fossils were so well perserved. first of all, the animals were living near or in the water. this is a big plus, especialy in this case because the animals were near many rivers or deltas, making a lot of sediment. Also that area is now bare rock. this means that exposed fossils can be easily found and excavated.




Certain pieces of anatomy have to change drastically to go from land to water. An example of this is the hip:


quote:
The pelvis (or hip girdle) is dramatically different in modern whales and land mammals (Figure 11). The pelvis in land mammals consists of sacrum and left and right innominate bones. The sacrum is a series of vertebrae (five in humans) that are fused to each other and connect to the innominates at the first (most anterior) of these vertebrae. The innominate is an elongated bone that bears the socket (acetabulum) for the femur, forming the hip joint, and has two branches posteriorly (ischium and pubis) that surround a foramen, or opening, and an anterior branch (ilium) that contacts the innominate from the other side. Sacrum and left and right innominates form a strong and rigid bony girdle that anchors the hind limbs and supports much of the body in locomotion. In modern whales, in contrast, the sacrum cannot be recognized, as there are no fused vertebrae and no vertebra has a joint for the innominate. In fact, the innominate in modern cetaceans is a tiny bar of bone lacking an acetabulum and distinct ischium, pubis, and ilium. The innominate is embedded in the ventral body wall where a few tiny muscles that are not involved in locomotion attach to it.

In Ambulocetus and Kutchicetus, the pelvis is much like that of a land mammal: The sacrum comprises four fused vertebrae, and these articulate with the innominate bones (Figure 11). Each innominate consists of ilium, ischium, and pubis and bears an acetabulum for the femur, as it does in land mammals. The femurs are long when compared with other whales, but shorter than most land mammals. Ambulocetus had large hind limbs and enormous feet. Feet are not known in remingtonocetids, but the sacral vertebrae of Rodhocetus are less strongly fused, and the femurs are shorter than in Ambulocetus. However, Rodhocetus innominates retain the deep acetabulum and the articulation with the sacrum. Georgiacetus is even more like modern whales, lacking a fused series of sacral vertebrae as well as a contact between sacral vertebrae and innominates. Unlike modern whales, the sacral vertebrae of Georgiacetus differ from caudal and lumbar vertebrae, and each innominate is large and consists of ilium, ischium, and pubis. The femur of Georgiacetus is not known. In basilosaurids and dorudontids, the innominates are small bones, with ilia that are not distinct. However, they retain an acetabulum and foramen. The innominates are not connected to the vertebral column, but these whales retain femurs that are longer than in modern cetaceans. The entire hind limb (Figure 6) is smaller than in other Eocene cetaceans and barely protrude from the body wall.

Together these pelvises form an excellent transitional series, in which ambulocetids and remingtonocetids retain all elements of land mammals, and protocetids lose the fused sacrum (Rodhocetus) and the iliosacral joints (Georgiacetus) and have short femurs (in known forms). Basilosaurids and dorudontids have greatly reduced hind limbs and reduced ilia, while still retaining the acetabulum and the foramen of the innominates. Only vestiges of these structures are present in modern whales.


I will expand this and put in more pictures later.


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pleco
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Posted - 04/13/2006 :  20:29:23   [Permalink]  Show Profile  Visit pleco's Homepage Send pleco a Private Message
My fav is homo sapiens, because we don't know where it is going... :-)

by Filthy
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Randy
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Posted - 04/13/2006 :  20:57:13   [Permalink]  Show Profile Send Randy a Private Message
quote:
Originally posted by pleco

My fav is homo sapiens, because we don't know where it is going... :-)



Hopefully without any nuclear mutations in the near future.

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beskeptigal
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Posted - 04/13/2006 :  21:11:43   [Permalink]  Show Profile Send beskeptigal a Private Message
I don't suppose bacteria passing genetic information around like a frat party spilling beer counts as a transitional fossil. Can I put it in as transitional genetic material?
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filthy
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Posted - 04/14/2006 :  03:39:36   [Permalink]  Show Profile Send filthy a Private Message
quote:
Originally posted by beskeptigal

I don't suppose bacteria passing genetic information around like a frat party spilling beer counts as a transitional fossil. Can I put it in as transitional genetic material?

Go with the fossils; there's lots of them, ancestrial to us all.

Just started to dig on mine.... It's worse than I thought it'd be.




"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)

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marfknox
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Posted - 04/14/2006 :  09:15:21   [Permalink]  Show Profile  Visit marfknox's Homepage  Send marfknox an AOL message Send marfknox a Private Message
http://en.wikipedia.org/wiki/Homo_habilis Homo habilis, for a couple reasons.

First, this was the first hominid to create and use tools as a regular part of its lifestyle. (Opposed to some primates and probably earlier hominids who occasionally make and use simplistic tools.) And I consider tool-making and using one of the biggest, if not the biggest hallmark of humanity. (As I type on my computer's keyboard.)

Second, Habilis is not as well known as what became before and after it: the Austropithecines (like Lucy) and Homo Erectus/Ergaser. This is largely because there are more Austropithecine and way more Eraster and Erectus fossils than Homo habilis fossils. To me, this makes the species much more intriguing because there is so much more to discover about it. There have been arguments whether to rename it Australopithecus habilis because the cranium fossils are so very much in the middle in brain side and shape between A. and H. (By the was, A. Africanus http://www.mnh.si.edu/anthro/humanorigins/ha/afri.html is a close second for my favorite because it, like Habilis, poses many more questions than answers about early human evolution, and thus, new discoveries about this species are all that much more exciting!)

And why have fewer fossils of Habilis been found? One possible reason is that there have been far more archeological excavations in Europe than Africa. In the past that has been due to racism and the blind belief that humans could not have evolved in Africa. But today it is largely because of political turmoil and poverty in those countries and the costs and risks for foreign archeologists going over there to dig.

But another possibility is that Habilis simpily wasn't around all that long due to punctuated equilibria, postulated by Niles Eldredge and Stephen Jay Gould. http://www.talkorigins.org/faqs/punc-eq.html

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Edited by - marfknox on 04/14/2006 09:16:07
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trogdor
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198 Posts

Posted - 04/14/2006 :  10:11:38   [Permalink]  Show Profile Send trogdor a Private Message


quote:
Ambulocetid cetaceans are slightly younger and more derived than pakicetid cetaceans. They were also much larger, similar in size to large sea lions. A nearly complete skeleton for Ambulocetus (Figure 3) shows that the animal had a large head, long muscular body, and a long tail. Its limbs were short but the feet long. In overall body shape, Ambulocetus looked somewhat like a crocodile, although its hind limbs and feet were considerably longer. It may have lived as an ambush predator of fish in shallow water. Ambulocetids lived in coastal environments such as bays and estuaries approximately 49 million years ago (mya) and are known only from India and Pakistan.


these are two cladograms of the whale evolutionary tree. the first is not that great, but has nice pics and shows what animals are closely related to whales. the secound gives a nice visual of the lineage of whales, but has no real pictures of the animals. it is also in Danish.







all eyes were on Ford Prefect. some of them were on stalks.
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Bill scott
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Posted - 04/14/2006 :  10:57:37   [Permalink]  Show Profile Send Bill scott a Private Message
http://en.wikipedia.org/wiki/Archaeoraptor


Just one of my many favorites...




The fossil was unveiled in a press conference on October 15 , 1999, and the November 1999 National Geographic Magazine contained an article by Christopher P. Sloan (National Geographic's art editor). Sloan described it as a missing link that would connect dinosaurs and birds.

(bill) Hmm. I thought they had already connected dinos and birds?




The original fossil was put on display at the National Geographic Society in Washington, DC , pending return to China. In the article Sloan used the name Archaeoraptor liaoningensis but with a disclaimer (so that it would not count as a nomenclatural act for the purposes of scientific classification) in anticipation of being able to publish a peer-reviewed description simultaneously in Nature. However, Nature and Science both rejected the paper, and National Geographic went ahead and published without peer review.

(bill) Why would Sloan be so hot to trot to get this fossil published and be willing to put his rep, and that of NG, on the line if birds had already been linked to dinos empirically? This would have been old news by now. But yet Sloan was chopping at the bit to get his "missing link" between birds and dinos published, almost as if he thought he had a big scoop that was previously unknown and undiscovered. It makes no sense for Slaon, and NG, to publish this against peer review and put their professional careers on the line in order to try and pass off a dino to bird missing link, if this connection had already been empirically made and was old news at this point in time.



Archaeoraptor was a fossil believed to be a theropod dinosaur closely related to the ancestors of birds, but which proved to be a forgery.

(bill) Since Slaon was trying to pass off the fossil as, "a missing link that would connect dinosaurs and birds" and then it was proved to be a forgery we can assume then that the search for a missing link that does connect birds to dinos continues on...





(bill) Here is what Storris L. Olson had to say on the whole fiasco:

After the November National Geographic came out, Storrs L. Olson, curator of birds in the National Museum of Natural History of the Smithsonian Institution, published an open letter on November 1, 1999, pointing out that "the specimen in question is known to have been illegally exported"; protesting the "prevailing dogma that birds evolved from dinosaurs"

"Lets get one thing clear, Bill. Science does make some assumptions." -perrodetokio-

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Paulos23
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Posted - 04/14/2006 :  11:04:16   [Permalink]  Show Profile  Visit Paulos23's Homepage Send Paulos23 a Private Message
If I remeber correctly, they sent the two fossils back to China where they found that both where completely new species that where not known before. It may not have been a missing link, but they do fill a gap in our knowlage.

You can go wrong by being too skeptical as readily as by being too trusting. -- Robert A. Heinlein

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pleco
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Posted - 04/14/2006 :  11:06:21   [Permalink]  Show Profile  Visit pleco's Homepage Send pleco a Private Message
I wonder if we'll ever see a link where these quotes are being pulled from....any bets?

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Bill scott
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Posted - 04/14/2006 :  11:12:28   [Permalink]  Show Profile Send Bill scott a Private Message
quote:
Originally posted by pleco

I wonder if we'll ever see a link where these quotes are being pulled from....any bets?



I did list the link, first thing...


http://en.wikipedia.org/wiki/Archaeoraptor

"Lets get one thing clear, Bill. Science does make some assumptions." -perrodetokio-

"In the end as skeptics we must realize that there is no real knowledge, there is only what is most reasonable to believe." -Coelacanth-

The fact that humans do science is what causes errors in science. -Dave W.-

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pleco
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Posted - 04/14/2006 :  11:14:53   [Permalink]  Show Profile  Visit pleco's Homepage Send pleco a Private Message
quote:
Originally posted by Bill scott

quote:
Originally posted by pleco

I wonder if we'll ever see a link where these quotes are being pulled from....any bets?



I did list the link, first thing...


http://en.wikipedia.org/wiki/Archaeoraptor



I apologize, I didn't see it. I retract my statement, just like National Geographic did about that whole affair, but for some reason it keeps being brought up.

At least they have the capability of admitting mistakes and rectifying them.

by Filthy
The neo-con methane machine will soon be running at full fart.
Edited by - pleco on 04/14/2006 11:17:44
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Paulos23
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Posted - 04/14/2006 :  11:16:15   [Permalink]  Show Profile  Visit Paulos23's Homepage Send Paulos23 a Private Message
Yes, I was correct. Here are the links:

http://www.talkorigins.org/indexcc/CC/CC352.html
and
http://www.nature.com/nature/journal/v420/n6913/abs/420285a.html;jsessionid=68F59B34353739C5A655E4E2B5A863A1

And, the claim was made in a non-peer reviewed magazine, not by published scientests. Just an example of someone pulling a fast one to make a buck and someone not looking closely enough. It happens. However, science was able to pull something valuable from this mess.

You can go wrong by being too skeptical as readily as by being too trusting. -- Robert A. Heinlein

Facts do not cease to exist because they are ignored. -- Aldous Huxley
Edited by - Paulos23 on 04/14/2006 11:18:11
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