Article: The mode of life of two Jurassic species of 'Posidonia' (Bivalvia)

On facies grounds Bositra buchi (Romer) was almost certainly not benthonic, but probably nekto-planktonic rather than pseudoplanktonic, since other possible pseudoplankton is rare in its typical facies, there is no sign of attachment at any stage of life, and there are morphological signs of swimming ability (anterior and posterior gapes, thin shell, and probable wide angle of opening in life). Experiment indicates that this mode of life is feasible. The hinge of B. buchi is described for the first time and the species is transferred from Posidonia to Bositra de Gregorio 1886.'Posidonia'' radiata Goldfuss was also almost certainly not benthonic on facies grounds. It was probably not pseudoplanktonic since it never occurs attached to wood like indubitable pseudoplankton in the same beds, and is much more abundant than such forms. Morphological evidence confirms that it was probably nektoplanktonic.The method employed in the feasibility experiments should be widely applicable in studies of the functional morphology of small organisms.