The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
Posted on 02/11/2005 6:49:09 AM PST by PatrickHenry
Triple bone structure arose independently in platypus and humans.
Listen up: mammals seem to have evolved the delicate bone structure of the middle ear at least twice. The surprising discovery comes from a fossil, found off the southern coast of Australia, that belongs to an ancestor of the platypus.
Modern mammals are unique among vertebrates for possessing three tiny bones in the middle ear. The malleus, incus and stapes (commonly known as the hammer, anvil and stirrup) work as part of a chain that transmits sound towards the skull. Birds and reptiles have only one bone to perform this function.
Because the mammalian arrangement is so complex, scientists believed that the set-up had evolved on just a single occasion, in an ancestor that gave rise to placental animals (including humans), marsupials and monotremes (such as the duck-billed platypus).
All this changed when James Hopson, a vertebrate palaeontologist at University of Chicago, Illinois, took a trip to Australia. There he met a team of researchers including Thomas Rich of Museum Victoria in Melbourne.
The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
Rich and his colleagues had recently unearthed a fossil of Teinolophos trusleri, an ancestor of modern monotremes that lived 115 million years ago. "He said he had some new Teinolophos specimens and when he showed them to me I almost fell off my chair," says Hopson, an author of the study, published this week inScience [Rich T. H., et al. Science 307, 910 - 914 (2005)].
Hammer time
Palaeontologists believe that the middle-ear bones of modern mammals once belonged to the jawbone and later separated to adopt their present location. This is supported by the fact that the middle ear's bones associate with the jaw in the early development of modern mammalian embryos.
What makes theTeinolophos specimen surprising is a large groove in its adult jawbone, which indicates that the smaller bones had not yet detached.
Teinolophos lived after monotremes split from the placental and marsupial mammalian groups. Its jawbone structure, along with its place in the evolutionary tree, hints that a common ancestor to all these mammals lacked the special three-bone ear structure.
This means that natural selection must have driven the same rearrangement in independent groups, after the monotreme split. "Some embryologists had the idea that it might be convergent but nobody really believed this," says palaeontologist Thomas Martin of the Senckenberg Research Institute in Frankfurt, Germany. "I was quite shocked when I heard that such a complex morphological transformation happened twice."
The discovery will compel many experts to rethink their appreciation of mammals' common evolutionary heritage. "Until now it was considered to be one of the most important shared derived characteristics of modern mammals," says Martin.
Thus do creationists unknowingly embrace their distant ancestry.
Nice to see that verified as not a freakish opinion.
Looks more like a Pakicetus than a hippo from here.
Yeah, and my dog looks more like a pakicetus than a hippo, but that does not make him a whale.
Remember, this is the reconstructed Paki skull, with the very important teeth and the migrating blowhole. Now teeth aren't so important.
And which god would that be? Ra? Brahma? Izanagi? Hunah Ku? Oh, and since this is a science thread, support your answer with science.
Or it means that they do not feel the need to read their bible in the narrow manner you do. But what use is a brain and science when you have four-thousand year old stories, right?
If you want to show two things as different, you should show two things as different. I think you understand that, but you're willing to pretend not to.
Don't brazen. Grow some integrity. Be a mensch. What you called for, I had. The early anthracotheres are small, generalized artiodactyls like the early cetacian Pakicetus. Apparently, in your ignorance you didn't know that.
You're doing what the gypsy in me foresaw here. It's a silly game. It shows the lurkers that we operate under different self-imposed rules. I'm allowed to be wrong, but I'm not allowed to lie. You're allowed to lie, but you're not allowed to be wrong.
I can't decide if you're Southacking this or Southack should be considered a notorious AndrewC-er. You had the act first but he does it longer. Anyway, you don't fool anybody.
No. But a 20 inch "mouse" is not the kissing cousin of 5 foot "wolf" with a whole set of different teeth.
You can read about the ~500 mm Anthracobunodon Here.
They don't like the hippo connection, but of course, this new casting with added features and thrown out teeth makes it so.(at least to you)
You are a piece of work. Is reality betraying you by making you wrong?
Be a mensch. Grow a pair. Or just grow up.
The concept of the 20-inch mouse is rather interesting, too. Is your dog related to a chihuahua?
What about HRC. Oh, I forgot. She's not a mammal.
Skin color is evidence of evolution. It filters the sunlight to affect vitamin D concentrations, especially important in pregnant women for infant mortality.
Going from highest sunlight environment to lowest, Africa to Scandanavia you go from darkest skin to lightest in a gradient.
Allele frequency change in populations over time=EVOLUTION.
That "gradient" was caused by interbreeding, Arabs are darker due to importation of slaves and southern europeans are tanned due to medieval Muslim invasions.
That's a prediction of evolution. Seemingly unlike things WILL converge as you go farther back in time. ID/creationism says, "I can explain it if they do, but I announce victory if they don't!"
The evolution prediction (and the ID "I can explain it..." non-prediction) is once again as always fulfilled. One might expect that to matter after 146 years of this, but it never does.
You-Can't-Make-Me-See-ism pounds the table on the missing links. Any missing links anywhere. Or just tips over the table and walks away.
Your typical attempt at civil discourse. Yes the smaller thing is the ichthyolestes, it also doesn't have the teeth of the Anthracobunodon and is also a scale larger than the anthracobunodon.
My dog is a chihuahua and it has dog's teeth not whale's teeth.
I reckon you could scientifically predict the outcome of the latest Superbowl game, too. Congratulations.
And Pakicetus has fossil whale teeth, not modern whale teeth.
Pakiceid teeth look a lot like those of fossil whales, but are unlike those of modern whales.
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