Answer:The discovery of the "distal-less," or Dll, gene in many different phyla.
Explanation: Appendages of animals are any external attachment or extension of one or two body parts of an organism in order for it to be able to effectively perform its responsibilities.
The morphological and functional changes or evolution of appendages is responsible for the adaptive radiation of tetrapods, arthropods and winged insects. Recent studies tends to show that all animal appendages may be homologous through the discovery of the "distal-less," or Dll, gene in many different phyla.
