Definition of synapomorphy in US English:



  • 1A characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants.

    • ‘The only known synapomorphy of this group is the presence of a sesamoid bone in the heel region.’
    • ‘These four genera form a monophyletic group defined by one synapomorphy (loss of one anterior left marginal).’
    • ‘But this is not very convincing, as it reveals only one valid synapomorphy.’
    • ‘This observation hints at one putative morphological synapomorphy of a Petopentia / Periploca clade.’
    • ‘Those specimens include conclusive evidence of the strongest possible bird-theropod synapomorphy - completely modern feathers and the oldest, most birdlike dromaeosaurs.’
    1. 1.1 Possession by two or more organisms of a characteristic inherited exclusively from their common ancestor.
      • ‘Based on cell lineages, the blastomere-by-blastomere derivation of most major larval organs, there is good reason to infer synapomorphy across the larvae of most lophotrochozoan phyla, if not the lophophorates.’
      • ‘It is through cladistic analysis that we are able to tell homoplasy from synapomorphy.’
      • ‘The diagnosis of Glades through synapomorphy becomes the starting point for the investigation of functional, temporal, adaptive and biogeographic questions.’
      • ‘This conflict can be resolved as either parallelism, reversal, or synapomorphy.’
      • ‘Thus, when a SINE sequence is found at an orthologous locus in two or more lineages, it can be regarded as evidence for synapomorphy.’


1960s: from syn- ‘together’ + apo- ‘away from’ + Greek morphē ‘form’.