Hostname: page-component-7b7567c8c-wxvwp Total loading time: 0 Render date: 2026-11-15T16:06:09.257Z Has data issue: false hasContentIssue false

Shape, Drag, and Power in Ammonoid Swimming

Published online by Cambridge University Press:  08 April 2016

David K. Jacobs*
Affiliation:
Museum of Paleontology, University of California, Berkeley, California 94720.

Abstract

This study assesses swimming potential in a variety of ammonoid shell shapes on the basis of coefficients of drag (Cd) and the power needed to maintain a constant velocity. Reynolds numbers (Re) relevant to swimming ammonoids, and lower than those previously studied, were examined. Power consumption was scaled to a range of sizes and swimming velocities. Estimates of power available derived from studies of oxygen consumption in modern cephalopods and fish were used to calculate maximum sustainable swimming velocities (MSV).

Laterally compressed, small thickness ratio (t. r.) ammonoids, previously assumed to be the most efficient swimmers, do not experience the lowest drag or power consumption at all sizes and velocities. At low values of size and velocity associated with Reynolds numbers below 104, less compressed forms have smaller drag coefficients and reduced power requirements. At hatching a roughly spherical shell shape would have minimized drag in ammonoids; with increasing size, hydrodynamic optima shift toward compressed morphologies.

The high energetic cost of ammonoid locomotion may have limited dispersal and excluded ammonoids from high current velocity environments.

Information

Type
Research Article
Copyright
Copyright © The Paleontological Society 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Article purchase

Temporarily unavailable