Scolicia, ichnotaxonomic practices, and the limits of behavioural convergence

Abstract

Many studies convincingly documented the diagnostic morphology of Scolicia, establishing afunctional link with the burrowing activities of heart urchins, common components of themarine mobile faunas that emerged during the Mesozoic Marine Revolution. However, thisichnotaxon has been repeatedly mentioned in both continental successions and Paleozoicmarine strata, even though its diagnostic characteristics were absent. This approach mayreflect the implicit belief that behavioural convergence is rampant in the ichnologic recordand can be uncritically adopted in almost all cases. We underscore the importance of adefinition of Scolicia that is based on diagnostic morphologic features and supported by asolid analysis from the perspective of function and mode of construction. This view of Scoliciahighlights its value in paleoenvironmental reconstructions and its significance to unravelmacroevolutionary trends. Attribution to an ichnotaxon should involve understanding ofmorphologic features in terms of its mode of production rather than the mere observationof superficial similarities.