Originally Posted by Gabe15

In taxonomy, whichever named is published first for a given species is supposed to have priority over any following publications. M. dasycarpa was published and described before M. velutina, which ended up being the same plant. Basically, through some errors and oversights many decades ago, the name M. velutina stuck while M. dasycarpa was ignored. According to international rules of botanical nomenclature, M. dasycarpa should be the proper name for the species.