The Mintakans may have been a subspecies of Vulcans. Onscreen they were referred to as "proto-Vulcan", but I don't know how that was intended.
I think proto-Vulcan meant they were following a parallel evolutionary path to Vulcans, not really subspecies.
Would Romulans be considered a subspecies of Vulcans? Or vice-versa? Remans a subspecies of Romulans?