Plutoniosaurus was named by Vladimir Efimov in 1997 based on the holotype specimen UPM 2/740, a partial skeleton. In 1999, Maxim Arkhangel'skii synonymized the genus with Platypterygius, as did Michael Maisch and Andreas Matzke in 2000.
Plutoniosaurus was initially described by Vladimir Efimov in 1997, but its status was later revised to be synonymous with Platypterygius by Maxim Arkhangel'skii and others.