This name is a synonym of Tortula subulata f. angustifolia (Warnst.) L.I. Savicz.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 35106798) with original publication details: Hedwigia 52: 77 1912.
This name was in version 1 of The Plant List, record tro-35106798.