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Liaoconodon hui  (Source: Jin Meng)
A new fossil, Liaoconodon hui, was found in China and has all three middle ear bones

Researchers have discovered a complete mammalian fossil that includes a transitional middle ear, which consists of three bones that paleontologists have been searching for over 150 years.  

Jin Meng, study leader and curator in the Division of Paleontology at the American Museum of Natural History, along with Wang Yuanqing and Li Chuankui, both from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences in Beijing, have found the first complete mammalian fossil that includes the transitional middle ear.

Mammals are defined as a class of air-breathing vertebrate animals that share characteristics like hair and mammary glands in mothers with young. They also share three middle ear bones called the malleus, incus and ectotympanic. Two of these bones are found in the joint of the lower jaw in reptiles, and researchers believe that an evolutionary shift from lizards to mammals separated the quadrate and articular plus prearticular bones from the posterior lower jaw, and they became associated with hearing as the malleus and the incus.

Previous fossils show early mammals with reptilian jaw joints and reductions in these bones for both chewing and hearing while other early mammalian fossils have ossified cartilage still connected to the groove on their lower jaws. But none of these fossils had the middle ear bones, and more evidence was needed to confirm this early transition and the mysteries of the mammalian middle ear. 

"People have been looking for this specimen for over 150 years since noticing a puzzling groove on the lower jaw of some early mammals," said Meng. "Now we have cartilage with ear bones attached, the first clear paleontological evidence showing relationships between the lower jaw and middle ear." 

The new fossil, which is called Liaoconodon hui, is a medium-sized mammal measuring 35.7 cm long. It dates from the Mesozoic (about 125 to 122 million years) and was named after the fossil beds in Liaoning, China, which is where it was discovered. It was also named after Yaoming Hu, who was a graduate of the American Museum of Natural History's doctoral program and passed away recently.  

Liaoconodon hui is complete, and shows researchers that the incus and malleus are detached from the lower jaw in order to create part of the middle ear. According to the study, the incus and the malleus "remain linked to the jaw by the ossified Meckel's cartilage that rests in the groove on the lower jaw," and the eardrum was stabilized with this cartilage as support. 

"Before we did not know the detailed morphology of how the bones of the middle ear detached, or the purpose of the ossified cartilage," said Meng. "Liaoconodon hui changes previous interpretations because we now know the detailed morphology of the transitional mammals and can propose that the ossified cartilage is a stabilizer."

This study also found that the middle ear "probably" evolved twice in monotremes, marsupials and placentals. This was determined by features associated with the groove on the lower jaw and other bones, including the presence of ossified Meckel's cartilage.  

This study was published in Nature.



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By PReiger99 on 4/18/2011 2:18:05 PM , Rating: 2
quote:
thus the theist has greater freedom within the doctrine of theistic evolution to suppose what may have happened rather than forcing his interpretation of the evidence to coincide with his worldview

I never read something more absurd than that. Theists force their interpretation of the evidences to coincide with their worldview. They begin with "gods must exist because I believe they do and as such they must guide evolution (because at this point denying evolution is simply too ridiculous)". Theists aren't interested in what may have happened, otherwise they would try to find evidence to support the existence of their gods. But you said it yourself, no evidence will ever "make the evolutionary argument from the fossil record more compelling" to you.

quote:
A common objection that is raised is "Occam's Razor", which is misused to say that more complex solutions to a problem must be discarded in favor of simpler ones.

Occam's Razor states that the simplest explanation that account for all the data is usually the best, not just the simplest explanation. Since there is not the slightest evidence that support the existence of deities, and that deities are infinitely more complex than the phenomenon you are trying to explain. Such hypothesis can be logically discarded.

quote:
My point with this post is simply to show that even if we find many, many 'transitional forms' that appear to support the gradual development of a feature that was once thought to be "irreducibly complex", that does little to make the evolutionary argument from the fossil record more compelling, and does nothing at all to undermine the position of intelligent design.

It won't convince people like you because your position is illogical. Basically, I could say that transitional forms are merely the will of invisible pink unicorns and my argument would worth as much as those of intelligent design proponents (which isn't much). When (un)intelligent designers manage to bring evidence to support their absurd hypothesis, then there will be a debate. Until that time, there is no debate whatsoever if one side demands extraordinary proofs from the other while bringing none of their own (while at the same time, demanding that their position be considered as logical as the scientific one for no other particular reason that they "believe" it to be true).


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