Spanish Plant misclassified for 176 years. Surprisingly, there are still plant species waiting to be discovered in the Iberian Peninsula. Some are detected thanks to the latest study methods, and others, such as Linaria becerrae, are described when reinterpreting species which are already known. This new Málaga plant had been classified by mistake for 176 years. Source 4h.
When it comes to classifying species, there are a hell of a lot more of them than there are people doing the classifying
Tack onto that the fact that the visible differences between some species is nil, and it is not all that surprising that some things fall through the cracks.