Meeting Abstract
Breaking intrinsic developmental constraints can allow for the origin of morphological novelties that overcome functional constraints. Kinethmoid-mediated premaxillary protrusion within cypriniform fishes is one such novelty that breaks some of the morphological constraints seen in acanthomorph-type premaxillary protrusion. Within acanthomorphs significant protrusion requires integrated evolution of the neurocranium to facilitate sliding of a greatly elongated ascending process of the premaxilla, a constraint that is broken by the addition of a kinethmoid to the upper jaw linkage in cypriniforms. This additional linkage allows for increased kinematic flexibility allowing species to more easily feed throughout the water column. Such trophic flexibility also characterizes cyprinodontiform premaxillary protrusion, where the evolution of a novel ligament has allowed for correlated movement of the premaxilla and dentary with no concomitant integration with the neurocranium. Importantly, the impact that different morphological novelties can have on the evolutionary, functional, and ecological history of a specific lineage varies. In the case of kinethmoid-mediated premaxillary protrusion this novelty is associated with ecological diversification; the novelty opens a great number of trophic niches via increased performance. This cypriniform ecological and trophic diversification is also correlated with increased species diversification. Breaking structural constraints may have allowed for increased trophic diversification within these two discrete lineages.
