Introduction to Evolutionary Teratology, with an Application to the Forelimbs of Tyrannosauridae and Carnotaurinae (Dinosauria: Theropoda)

摘要

Conceptualisation of evolution requires new inclusions, as evidenced by contributions brought by evolutionary developmental biology—the evo-devo connection. Integration of teratology in an evolutionary framework fits in this continuity. It highlights the production of developmental anomalies (more or less drastic) over evolutionary times, which become integral parts of groups and taxa. Originating in Étienne Geoffroy Saint-Hilaire’s work, the contemporary independent formulation of evolutionary teratology allows a better understanding of some anatomical structures. The limbs of tetrapods are a promising field of study as some changes in their shapes, proportions and compositions are close to malformations observed in teratology. The forelimbs condition of Tyrannosauridae and Carnotaurinae is a good example. They are theropod dinosaurs characterised by different anterior micromelias, codified following an anatomical nomenclature. An association with the knowledge from developmental biology helps to discern possible productive mechanisms of such micromelias, including the influence of developmental rates, Hox genes, growth factors and developmental pathways conserved in evolution. What is more, the case of Tyrannosauridae and Carnotaurinae imposes to use the ‘adaptive’ reasoning in a more balanced framework. Indeed, the viability and evolutionary success of an organism is the result of the equilibrium of aptitudes between its various anatomical parts interacting with the circumstances.