oligomyoid

from The Century Dictionary.

• In ornithology, having few or imperfectly differentiated muscles of the syrinx: applied to a lower series of birds of the order Passeres, such as the Clamatores or Mesomyodi, and synonymous with mesomyodian, but of less exact signification.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Anat.) Having few or imperfect syringeal muscles; -- said of some passerine birds (Oligomyodi).