a. 平胸类的

n. 平胸鸟

[ noun ]
flightless birds having flat breastbones lacking a keel for attachment of flight muscles: ostriches; cassowaries; emus; moas; rheas; kiwis; elephant birds
<noun.animal>

Ratite \Rat"ite\ (r[a^]t"[imac]t), a. (Zo["o]l.)
Of or pertaining to the Ratit[ae]. -- n. One of the
Ratit[ae].