Björn Bergenholtz
(former alias "Calalp")

Fred, first, a tiny remark, I think the reference ought to be:[...]
Genus Querandiornis Rusconi, 1958
Querandiornis romani Rusconi, 1958
Carlos Rusconi, 1958
Ave Fósil del Plioceno de Buenos Aires
Revista del Museo del Historia Natural de Mendoza 11: 157-160
I don't have the paper and can't find it on line, so help is needed
[...]
• Rusconi, C. 1958. Ave fósil del Plioceno de Buenos Aires. Revista del Museo de Historia Natural de Mendoza, 11 (No. 1–4): pp.157–160.
However, the only digitized version of it, that I can find, is this one (though only in Google Snippet view/s), where we find "Querandiornis Romani n. g. n. sp."), on p.157. Also see here (for the Title itself, on the very same page).
That it ought to be the correct issue/title is also verified here.
But, ... to my surprise I've also found this taxon quoted as being published (possibly again/twice, or as a separate piece?), as of/in:
• "Rusconi, C., 1958. Ave fosil del Plioceno de Buenos Aires. Revista Museo Historia Natural 21: pp.1–3."
Which one was the very first one ... I simply don't know.
More info on the Author (Auctor) himself = here (incl. one of the Plates from the OD). All in Spanish.
Hopefully of some help/use?
Björn