The correct original spelling of the specific name of Guerrerostrongylus zeta (Travassos, 1937) (Nematoda, Heligmonellidae), parasitic in South American rodents.

In 1937, Travassos described a new species of nematode in the genus Longistriata Schulz, 1926. He referred to it seven times as L. zetta in the main text, but also five times as L. zeta in the figure legends. This nominal species is currently assigned to the genus Guerrerostrongylus Sutton and Durette-Desset, 1991. The complete bibliography referring to this species from 1937 to date comprises only 22 works. Although the spelling 'zetta' has prevailed since 2011, the correct original spelling of its specific name remains unsettled. Acting as First Revisers under Articles 24.2.3 and 32.2.1 of the International Code of Zoological Nomenclature, we hereby choose 'zeta' as the correct original spelling of the specific name of this nematode, thus rendering 'zetta' an unavailable incorrect spelling. In making this choice, we have taken into account Travassos' obvious intention to name the species after the sixth letter of the Greek alphabet and the longer use of the spelling 'zeta' in the relevant literature, especially in those works in which 'zeta' (never 'zetta') was first combined with other generic names. We believe that standardizing the use of the spelling 'zeta' as the correct original spelling is the best way to stabilize this name.