Abstract
The most widely cited explanation for the functional enigma of sutural complexity in ammonoids, the Buckland hypothesis, has related septal folding and fluting to buttressing, providing increased shell strength against implosion, along with increased efficiency and decreased weight in shell and septum construction. In Paleozoic ammonoids, sutures ranged from simple to extremely complex. Comparison of shell and septum thickness (in polished sections) with sutural complexity in 49 Paleozoic ammonoid genera (Middle Devonian–Upper Permian) indicates that no significant reduction in either septum thickness or shell thickness accompanied a one-hundred-fold increase in sutural complexity. These preliminary results fail to support the Buckland hypothesis, suggest there may have been alternative incentives for increasing sutural complexity, and add support to views that septal fluting may have been related to buoyancy control.

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