Mammoth Uncensored Word List:
21 words ending with t, 19 letters long

anticonservationist antifluoridationist chemicophysiologist chemostratigraphist cyclostratigraphist electrometallurgist electrophysiologist lithostratigraphist micropaleontologist neuropharmacologist palaeoclimatologist paleoanthropologist paleotempestologist phytopaleontologist radioallergosorbent representationalist syncytiotrophoblast transformationalist ultrafundamentalist ultrasegregationist ultratraditionalist