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.
...as well as a behemoth!
Job 40
15 "Look at the behemoth, [a]
which I made along with you
and which feeds on grass like an ox.
16 What strength he has in his loins,
what power in the muscles of his belly!
17 His tail [b] sways like a cedar;
the sinews of his thighs are close-knit.
18 His bones are tubes of bronze,
his limbs like rods of iron.
19 He ranks first among the works of God,
yet his Maker can approach him with his sword.
How to serve man..............
You are just playing to the pious people with precious platitudes,aren't you!?
They were? It seems to me that you're supposed to be proving that, rather than asserting it, especially for this fellow's mode of transport...
Guess I saw pretty clearly back in post 9, hmmm?
There are still fish. There are still monkeys. There are still creationists.
It was an honest question. Lots of creationists insist that those who accept both evolution and God don't know the Bible.
Spontaneity isn't your strong point. Say something coherent sometime and I'll try to get back to you.
Gosh only knows what the heck I meant!
Naw He just didn't know what to do with the leftover parts!
If we had absolutely all the evidence, a perfectly preserved body in formaldehyde for every organism that ever lived--never mind where this repository is supposed to be stored--we would according to evolution have a record of smooth transitions which outlines a tree of common descent. The traditional problem from Darwin's day forth is that geology doesn't give us such a perfect record and, as Darwin himself noted, it never will.The biomass you take out of circulation (essentially all of it that ever lived) in preserving such a record would change the history of life on Earth forever and at once. Just for one thing, nothing is allowed to eat anything else. Carnivores and scavengers could never have evolved. Animals of any sort could only get so far, would probably have died out early in the history of life. Plants would have to do without something of which they make great use now: nutrients from decomposed organisms.
In trying to keep such a record, you would have a Heisenbergian measurement-changes-what-it-measures problem in its most extreme form. Better to just sample lightly, take some DNA, and snap some pictures.
I'm going to burn for this one, fer sure.
No, that is not my job especially since many on your side won't allow the tools to perform that job(it is still being done by others). What I can do is show that tossing asphalt in the air into an east wind at Dallas and expecting a resulting thoroughfare to Detroit is not how you build roads.
But if it will make you happy.
My ears are splitting and I am rocked! Guess I'll have to call off work.
Get a gall bladder, it will certainly help improve your outlook on life.
Just because you wear a bandanna on your head, advertise using the title "Madame", and speak with a gypsy accent does not make you a prophet. Defining any response contrary to your viewpoint as "lawyering" prior to receiving any response does, as ole Abe purportedly stated, fool some of the people some of the time. I suggest you find them and make a killing selling them the Brooklyn bridge.
No. It is for you to show how randomly tossing asphalt into the air results in highways.(first get the asphalt)
The calumny of convergent evolution will be proffered on this thread. In comparative physiology this term was thrown about with impunity without any evidence that it could pass the reasonable test or logical test. I will watch this thread unfold with a wry smile.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.