Behavioral implications of branching and tube‐lining in Teredolites

Observations on Teredolites (clavate borings in xylic substrates) produced by wood‐boring bivalves in both Recent and fossil marine woodgrounds warrant comment on two hithertofore unrecognized or neglected morphologic features, both of which have behavioral significance; true branching and calcite linings. Branching, often associated with reduced or terminated diametric growth of tunnels, is recognized as a locally common morphologic variation in T. longis‐simus within Cretaceous to Recent woodgrounds. Like other aspects of axial stenomorphism, this branching records the attempt oftere‐dinid bivalves to maintain endoxylic deposit‐feeding activity in increasingly crowded, fractionated substrates. Calcite tunnel linings, which are characteristic of T. longissimus produced by teredinids, occupy an equivocal position relative to body fossils and ichnofossils. Nonetheless, variations in lining morphology (e.g., tube length, presence or absence of anterior and retrusive caps) are more a reflection of varying behavior than of zootaxonomy or ontogeny. Hence, in contrast to the opinion of previous workers, we argue that linings should be regarded in ichnoterminology pertaining to Teredolites.