Tuesday, January 24, 2006

Ears for Breathing?

` Panderichthys was a fish - related to the first land vertebrates - about 370 million years ago. The bits of rock that remain are of utmost interest to scientists, who have discovered that it had ear-like structures.
` In News@Nature, Helen Pearson writes:

...The bony structures in ancient fish, which at some point turned into ears, for example, appear to have had mainly a structural function, bracing the cheek and holding up the jaw....

...Martin Brazeau and Per Ahlberg of Uppsala University in Sweden decided to take a close look at the ear-like features of an ancient, metre-long monster from the Latvian Natural History Museum in Riga....
` They found that Panderichthys had ear-like structures similar to both that of fish and the early landlubbers - a combination of both.
Ancient fish have a narrow channel from the roof of the skull into the mouth, known as a spiracle, which is bounded by a long bone known as the hyomandibula that braces the cheek. In tetrapods, the equivalent bone is stubbier, a step towards the stirrup-like stapes bone that helps to transmit sound waves into our skulls.

The team found that Panderichthys has a wide, straight spiracle rather than a narrow one, and a shortened hyomandibula. They report their findings in Nature1.
` Sharks and rays have similar structures which help the fish breathe while lying on the sea floor without accidentally gulping down the sea floor.
` Quite useful things, rather like nostrils in a way....
` As it has already been speculated that ear canals evolved from breathing tubes, the enlarged spiracles of Panderichthys seem to confirm this idea.

` Well, I really must go, it is a gorgeous day! Pictures later!

5 comments:

Galtron said...

Does this have anything to do with that valve-thingy you can open and close in your ear?

S E E Quine said...

` No idea, actually. And to tell you the truth, I don't have my notes on fish nostril evolution (they're on my still-down hard drive), so I couldn't even guess.

monado said...

Neato! I read the summary in Nature. Yet another major transitional fossil. And now that you've written about this, I can just link to it!

S E E Quine said...

` Oh, now I feel all warm and fuzzy!

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