Fig. 2

The relative shapes of ammonoid shell models tested by Chamberlain (1976) are shown in Westermann Morphospace (circles). Reported measured coefficients of drag are represented in each diagram with contoured isolines. a Coefficients of drag reported for models in “rest” position, with unique aperture angles designated for each shell (see Chamberlain 1976; Table 1). b Coefficients of drag reported for models each positioned at 30°. Filled circles in both a and b mark the shell models with the lowest reported drag