Is there an international taxonomy of academic titles/ranks?
In general, the answer is negative.

Not only there are different systems in different countries (and same-spelled degrees may have different requirements), but even if a degree seems to be the same, it is not necessary  considered equivalent.

Often universities and institutes have some freedom in the interpretation of degrees earned in other countries. Common sense can be a good guide but in case of doubt you need to check if university (or institute) X accepts a foreign academic title Y instead of their Z. 

For example, when I obtained degrees licencjat (3 years undergraduate, 180ECTS) and magister (5 years undergraduate, 300ECTS) from a Polish university, they refused to translate it into anything else (stating explicitly that it is not equivalent to anything else). However, some other Polish universities do translate it into Bachelor of Science and Master of Science, respectively. Nevertheless, my new institute didn't have problem to find them qualifying me for their PhD program.