The word chelicerate is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 20
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (27 words)
accrete, alethic, archlet, article, calcite, caliche, caltech, catcher, chalice, cheater, chelate, circlet, etheric, ethical, hectare, heretic, leacher, leather, leecher, recache, recatch, recheat, recital, reelect, reteach, teacher, treacle