This name is a synonym of Lactuca viminea subsp. ramosissima (All.) Arcang..
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 9F4FB41E-69E8-49ED-883E-976D2D8D5DE5).
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 Lactuca ramosissima in version 1 of The Plant List.