quote:So, where do dry-land rocks come from? Well, some were formed on land, and some in fresh water, and some in shallow sea water. But very few were formed in deep sea water. Plate tectonics makes it clear why this should be. The deep ocean floor is constantly being destroyed, sucked down into the earth at subduction zones. It is unlikely for a piece of deep ocean floor to wind up as a dry-land rock.
For more information on their diversity and specific characteristics see:
(palaeos is (or was) a massive linked website on fossils and their divisions\cladograms, but is undergoing a major overhaul and so many links no longer work properly. You can search the site for specifics.)
But I came up blank on habitat of the fossils ... but with their diversity I would not be surprised that they used to inhabit a number of ecologically diverse depth environments.