Meeting Abstract
The past five years have witnessed a renewed interest in discrete morphological characters as a source of phylogenetic data, after a decade or more of their dismissal in favour of molecules-only approaches. This has stemmed to some degree from phenomic methods (i.e., amassing character sample of sufficient sizes to take advantage of the statistical power that had hitherto been exclusive to molecules), but also from refinements in total evidence dating and morphological clock analyses, both of which require morphological character matrices and temporal data from fossils. The unique contribution of palaeontology is stem groups, revealing the sequence of character acquisition in long-branch terminals (such as the euarthropod stem group) and otherwise unknown morphologies (like armoured lobopodians and radiodontan giant predators in the onychophoran and euarthropod stems, respectively). The origin of mandibles exemplifies an integrative approach: 1) transcriptomics defends a single origin of mandibles in the clade Mandibulata; 2) Cambrian fossils inform on morphological changes in the gnathal appendages in the mandibulate stem group; 3) molecular dating, calibrated by fossils in novel modes of exceptional preservation, draws the mandibulate stem into the early Cambrian; 4) gene expression in extant taxa identifies genes that specify mandibular identity from a trunk limb-like precursor.
