This name is a synonym of Carduus nyassanus (S.Moore) R.E.Fr..
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record C826DE47-E163-4B41-8A5E-6A01283927A4).
This name record (from TICA) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Carduus nyassanus in version 1 of The Plant List.