SICB+ A functional matrix approach in comparing secondarily aquatic transitions across clades Formoso, KK; University of Southern California and Natural History Museum of Los Angeles County, Los Angeles, CA email@example.com http://www.formorphology.com
Despite convergence in aquatic locomotory morphology in the derived members of secondarily aquatic clades, distinct functional and morphological differences separate these clades at the onset of their transitions, particularly between mammal and reptile groups. The presence and absence of certain bones, vertebral orientation and movement, and limb posture are differences divided distinctly between mammals and reptiles. For example, marine mammals’ lack of a coracoid and clavicle and having ancestrally upright posture with dorsoventral axial movement, as opposed to the complex pectoral girdles on marine reptiles and an ancestrally sprawling posture coupled with lateral axial movement. Yet, secondarily aquatic groups, both mammal and reptile evolved locomotor morphology suited to the aquatic realm via predominantly axial or paraxial swimming. My functional matrix approach compares four secondarily aquatic clades, (cetaceans, pinnipeds, mosasauroids, and sauropterygians) two mammal clades and two reptile clades, evenly split between upright and sprawling ancestral terrestrial states, by determining sets of functional complexes which pertain to aquatic locomotor morphology of the tail, trunk, forelimbs and hindlimbs across taxa in each clade. The matrix of these functional complexes, which constitute combinations of skeletal morphological traits in fossil and extant taxa, can allow me to directly compare the manner in which marine mammal and reptile groups transitioned to aquatic environments, and determine if evolutionary patterns are present in groups which share ancestral terrestrial functional morphology or derived swimming locomotion.