Re: K/T revisited, was: Re: DINOSAUR digest 3382

[David Marjanovic <david.marjanovic@gmx.at>]

> Peter Ward (and others) believes that ammonites went extinct because they
> bred/fed at shallow depths.  In contrast, he claims that nautaloids
> survived because they bred/fed in deeper water.  I'm don't know what his
> take is on squids and octopus.
>
> The hypothesis is that the deeper depths were "buffered" from the carnage
> that was occurring in the near-surface marine waters.  This idea is
> supported by the observation that Maastrichtian benthic biota tended to
> fare a little better than did their pelagic counterparts.

The explanation I've read is that, unlike nautiloids and coleoids, ammonites 
had planktonic larvae (known in the fossil record as "ammonitellae"), and 
that the plankton was largely wiped out. This would also help to explain the 
complete extinction of the rudists and inoceramids (which, in addition, most 
probably fed on plankton). Didn't the corals (which also have planktonic 
larvae) need the entire Paleocene or so to form the first full-size Cenozoic 
reefs?

Is anything known on the belemnite life cycle...?