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09-08-2002, 09:45 PM | #11 | |
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09-09-2002, 06:25 AM | #12 | |
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Try sharks. As already noted, eyes came before bony skulls, so skulls evolved to fit them. A key point to realise is that bone condenses out of cartilage. Sharks and rays (elasmobranchs, IIRC), unlike literally ‘bony fish’ (teleosts), don’t have bony skulls (or bony anything else); their skeletons are made out of cartilage (hence also being called chondrichthys). Cartilage is a connective tissue, and can form rigid structures, hence it can act as a skeleton. There are even simpler fishy things in the group ‘agnatha’ -- jawless fish such as lampreys and hagfish. Try a Google on combinations of those words with ‘evolution’ and you should get enough info to keep you busy... Also, get Benton’s ‘Vertebrate Palaeontology’ from the library, and check out the first couple of chapters. Cheers, Oolon |
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09-09-2002, 08:59 AM | #13 | |
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E.g. Anableps: <a href="http://ebiomedia.com/gall/eyes/4eye.html" target="_blank">From the "Eye to Eye Gallery" page</a> Anableps is often refered to as "the" "four-eyed fish" but it is probably better described as a two-eyed fish specialized to look above and below the water. There is an even more spectacular example of four-eyedness in fish, mentioned by Dawkins (with a diagram) somewhere, but I can't remember the details. Separate lenses and everything though. nic [ September 09, 2002: Message edited by: Nic Tamzek ]</p> |
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