Analogies between the recent bivalve Tridacna and the fossil brachiopods lyttoniacea and richthofeniacea
Abstract The modern bivalve Tridacna has enormous size and very rapid growth; it has an unusual feeding mechanism and an unusual diet. It is confined to well-lit warm waters, i.e., shallow clear tropical seas. All these features are associated directly or indirectly with the presence of symbiotic Zooxanthellae within exposed tissues. The Upper Paleozoic brachiopods Lyttoniacea and Richthofeniacea probably had large areas of mantle tissue exposed to the external environment. They were fairly large, and can be interpreted as having had fairly rapid growth, abnormal feeding mechanisms and abnormal diets. They appear to be confined to environments which can be interpreted as shallow-water carbonate substrates. It is suggested that they also had symbiotic Zooxanthellae. The suggestion is testable because it imposes narrow limits on the environments in which these brachiopods should be found.