a. 有鳍状肢的

[ noun ]
aquatic carnivorous mammal having a streamlined body specialized for swimming with limbs modified as flippers
<noun.animal>

Pinniped \Pin"ni*ped\, n. [L. pinna feather, fin + pes, pedis, a
foot: cf. F. pinnip[`e]de.] (Zo["o]l.)
(a) One of the Pinnipedia; a seal.
(b) One of the Pinnipedes.