Hi all -

Some of the giant, but flat, Inoceramids from the Cretaceous apparently grew that large to spread out the surface area of the gills, so they could survive in bottom waters that were low in dissolved oxygen content (dysaerobic).  I frequently came across huge specimens in dark gray to black shales in the Western Interior while looking for ammonites as part of my paleoecological research.

We can add to the list of large bivalves the rudist clams (Hippuritoidea), an extinct Jurassic to Cretaceous group of sometimes bizarre clams that made up some of the major reefs in the Cretaceous Period (remains found in many places in the world).  These clams also may have had the symbiotic relationship with algae, with photosynthesis removing carbon dioxide from the immediate environment to help facilitate growth of large shells (some rudists reached almost 2 meters across).  A good website with info and pictures (including some of the preserved reefs) is www.paleotax.de/rudists/intro.htm<http://www.paleotax.de/rudists/intro.htm>

- Rick
________________________________
From: Conchologists List [[log in to unmask]] On Behalf Of Harry G. Lee [[log in to unmask]]
Sent: Saturday, October 22, 2011 8:16 PM
To: [log in to unmask]
Subject: Re: [CONCH-L] Tridacna big enough to see from space

Dear bivalve boosters,

Don't forget the extinct Inoceramus, which outstrips Tridacna, reaching over six feet in maximum dimension.

Like the Tridacna of today, these Cretaceous monsters probably evolved with endosymbiotic mutualists which provided the nutrition that mere filter-feeding could not provide to an organism of such mass.

Harry

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