This name is a synonym of Rumex dentatus subsp. callosissimus (C. F. W. Meissn.) Rech. f..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 100374844) with original publication details: Prodr. 14: 57 1856.
This name record (from Tropicos) 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 Rumex callosissimus in version 1 of The Plant List.