The Collaborative International Dictionary of English v.0.48:

Pleuronectoid \Pleu`ro*nec"toid\, a. [NL. Pleuronectes, name of
   a genus (fr. Gr. ? rib + ? a swimmer) + -oid.] (Zool.)
   Pertaining to the Pleuronectid[ae], or Flounder family.
   [1913 Webster]