The finding of an incorrect non-Antarctic locality assigned to a specimen of Trematomus loennbergii at the Natural History Museum, London, led to the discovery of two (of three) syntype specimens, previously considered missing, of this species. The third syntype, a larger specimen in better condition, is designated as the lectotype of T. loennbergii; the two newly discovered specimens, re-identified as Trematomus pennellii, become paralectotypes.