Sentence:  The repeated exposure, over <WSD>decades</WSD>, to most taxa here treated has resulted in repeated modifications of both diagnoses and discussions, as initial ideas of the various taxa underwent—often repeated—conceptual modification. 
Meaning of the word marked with <WSD> tags:  A period of ten years (from 17th c.), particularly such a period beginning with a year ending in 0 and ending with a year ending in 9. (from 19th c.)