Latin scientific names of living species is a marker of scientific litterature, including popularization texts. They are even markers of sub-disciplines of science. And they work as markers even if the reader does not fully understand them. We have large archives of an ancient French science popularization magazine (LA NATURE, 1873-1960) in which we want to help a modern reader to navigate. One way of helping the reader is to map the archives on scientific disciplines. Thus the need to identify markers. Latin names of species look Latin, but this is not enough for distinguishing them in a French text. They are rare words, but it is not enough again. They are both Latin and rare, and this is enough. The two criteria are relatively inexpensive and easy to play with. Altogether, they form a nice alternative to more expensive, and less predictable methods, like methods based on neuronal AI.