The word dimetrodons 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: 17
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (65 words)
dermoid, desmoid, desnood, disroot, distend, dominos, doormen, editors, emotion, endmost, erosion, indoors, indorse, ionomer, isodont, mentors, meronts, middens, minders, mindset, minters, misdoer, misdone, moderns, moisten, moister, monitor, monoids, monster, moodier, mordent, mortise, motions, motored, nimrods, nodders, noisome, norites, orients, osteoid, reminds, remints, rodents, roisted, roosted, rosined, snooded, snooted, snorted, soddier, sootier, sortied, steroid, stonier, storied, stormed, tierods, tinders, toddies, toonies, toroids, torsion, tridems, triones, trodden