• morphological
  • However, in the late 20th century some ornithologists argued that they are more closely related to storks on the basis of karyotype, morphological, and behavioral data. (wikipedia.org)
  • Fregatidae (frigatebirds), Sulidae (gannets and boobies), Phalacrocoracidae (cormorants and shags), Anhingidae (darters) and the Phaethontidae (tropicbirds) were traditionally placed in the Pelecaniformes, but molecular and morphological studies indicate they are not such close relatives. (wikipedia.org)