What is "opilionea"

Phalangoidea \Phal`an*goi"de*a\, n. pl. [NL., from Phalangium the daddy longlegs (see Phalangious) + Gr. e'i^dos form.] (Zo["o]l.) A division of Arachnoidea, including the daddy longlegs or harvestman ( Phalangium) and many similar kinds. They have long, slender, many-jointed legs; usually a rounded, segmented abdomen; and chelate jaws. They breathe by trache[ae]. Called also {Phalangides}, {Phalangidea}, {Phalangiida}, and {Opilionea}.