IANAPhysicist, but "shape" strikes me as a particularly inapt metaphor for the property of neutrinos under discussion. "Lepton number" or "mass eigenstate" are unfamiliar terms, but at least they don't mislead the reader into imagining that leptons have shapes. Since the offending term occurs only in the headline and at the beginning and end of this article, this is probably the work of a clumsy linkbaiting editor. I hadn't previously noticed that at Nautilus.
Towards the beginning of the article:
No other fundamental particles do this. “Only the neutrinos can change from one type to another,” says André de Gouvêa of Northwestern University in Evanston, Illinois. More than a quirk of nature, this ability to mutate on the fly points to some deep questions in physics, and potentially, some important answers.
Not so much "shape shifting" as "transmogrifying," but it still works. No mention of Changelings either.
