Sentence:  The paradox with these words arises because, with the exception of this class, all the descendants of aer and er words became /ihr/ and ar class words became /ehr/. The notion of a <WSD>superjump</WSD> is not very useful here. 
Meaning of the word marked with <WSD> tags:  (linguistics) A hypothetical phonological change in which a phoneme shifts to another realization, skipping over an intermediate phonetic value that is left unchanged.