Abstract

Molluscan ornament in modern oceans increases with decreasing latitude, in response to greater risk from tropical durophages (shell-crushing predators). The latitudinal gradient is presumed to be associated with the appearance of modern durophages during the Cretaceous, but this is untested. A radiation of durophages during the Devonian may have resulted in sufficient predation pressure to influence prey distribution similarly, although Devonian predators and prey are distantly related to their recent equivalents. This study examines latitudinal variation in ornament in Devonian strophomenide brachiopods to determine if a latitudinal gradient existed. A latitudinal gradient is documented for the Devonian; ornament decreases with increasing latitude. The correlation between proportion of spinose genera and region is −0.947 (p < 0.001). Similar to modern molluscs, spinose strophomenide genera constitute 26%–41% of tropical genera. The data corroborate the hypothesis that predation influenced the evolution and distribution of prey as early as the Devonian Period.

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