Re: Prehistoric Plankton Predators (PPP for short)

["Dino Rampage" <dino_rampage@hotmail.com>]

Thanks for all the help. Guess Leedsichthys slipped my mind. So it seems 
that lamniform & orectolobiform sharks evolved planktivorous forms in the 
Late Cretaceous.

By the way, I don't think that krill were necessary in order to sustain 
giant filter-feeding planktonivores; I was trying to visualise a creature 
much like our modern day whale shark, a giant inhabitant of warm tropical 
waters, not the mysticete whales living in frigid polar seas. I think that 
back then, there was still plenty of plankton floating about in the seas; 
copepods & ostracods, the nauplii & larvae of various crustaceans & fish; if 
ammonite young were planktonic, that would be an additional boost. Let's not 
forget that today, many fish spawn en masse, or that giant clams & hard 
corals synchronise their spawnings to create a rich planktonic 'soup' surely 
a bonanza to any animal with the adaptations to filter out the good stuff.

I agree that it is likely that some prehistoric marine reptiles were 
facultatively planktonivorous. The leopard & crabeater seals, which feed on 
krill but do not filter it out (in the strictest sense) came to mind. Also, 
I watched this documentary where a blue shark was swimming through a swarm 
of krill, taking large bites out of the red cloud. Maybe cryptoclidids & 
other plesiosaurs, with their interlocking teeth, did take advantage of 
planktonic blooms.

But I'm just wondering whether predation may have had any effect on giant 
plankton feeders; Are there any records of giants like whale sharks, basking 
sharks & manta rays being attacked by say, great white sharks or orcas? Just 
imagine... a Leedsichthys cruises along when a Liopleurodon rises out of the 
deep & before the fish can react, the reptile bites it into half, turning 
the sea red & attracting pterosaurs & sharks for miles around. What I would 
give to see that...







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