Sentence:  As stated earlier in the paper , Onsets and Completions - particularly the former - provide a different tool or indicator of expectancy in osseous <WSD>development</WSD> , each within a limited age period . 
Meaning of the word marked with <WSD> tags:  (biology) the process of an individual organism growing organically; a purely biological unfolding of events involved in an organism changing gradually from a simple to a more complex level