This name is a synonym of Alternanthera elongata (Willd.) Schinz.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 1100300) with original publication details: Prodr. 13(2): 372 1849.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:61471-1.
This name was in version 1 of The Plant List, record tro-1100300.