This name is a synonym of Baccharis breviseta DC..
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 5395EC9C-8C2F-40B7-9A12-75995D469B8A).
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 Baccharidastrum argutum in version 1 of The Plant List.