Sentence:  The dynamics of river systems in <WSD>megafan</WSD> environments may strongly influence the fragmentation and reconnection of riverine habitats, and therefore by implication, the diversification and distribution of freshwater organisms. 
Meaning of the word marked with <WSD> tags:  A very large mass of clastic sediment deposited by a laterally mobile river system that fans out from the outlet from a large mountainous drainage network.