Balanoglossus-evlolutionary link?

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123Herpatology
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Balanoglossus-evlolutionary link?

Post by 123Herpatology » Sun Jul 09, 2006 7:39 am

As most people know, there is a bit of gray area between what animals show an evolutionary link to vertabrates and invertabrates. In my textbook it provides an acorn worm (entreropneusta) which is a hemichordate. Hemichordates apparently are an evolutionary link between vertabrates and invertabrates. this acorn worm balanoglossus has gill slits but no notochord? Does a stomochord prove that its an evolutionary link?
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Post by Darby » Thu Jul 13, 2006 6:57 pm

Keep in mind that "invertebrates" isn't actually a group, and there's already a number of firmly-established links between the Chordates with vertebrae and the ones without. Hemichordates used to sometimes be lumped into the chordate phylum, but have been moved out, partly for the reasons you mention. They share "recent" ancestry with chordates (and therefore vertebrates), but they're a side branch, not an intermediary.

Here's a reference:

http://scienceblogs.com/pharyngula/2006 ... vodevo.php

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