>The evolution of larval planktotrophy in the Mollusca is a very interesting
>issue, as it is in the Animals in general.
>Within the Mollusca larval planktotrophy has evolved in the Bivalvia AFTER
>the protobranchs, that is the bivalves originated as lecithotrophs and only
>secondarily planktotrophy appeared.
>The sole other class where larval planktotrophy is known is Gastropoda. All
>other classes seem to have only lecithotrophic development, indicating that
>this is the primitive state in the Mollusca.

Nautilidae have direct development, and so did ammoinoids. As do at
least some octopods and decapods.
--
Andrew Grebneff
Dunedin, New Zealand
64 (3) 473-8863
<[log in to unmask]>
Fossil preparator
Seashell, Macintosh & VW/Toyota van nut
I want your sinistral gastropods!
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Q: Because it reverses the logical flow of conversation.
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