No biographical details are currently known.
Antonio looks to have been another actor who came to the profession quite late in life, his hair already greying in his earliest roles. He looks to have had around 18 credited roles spread over a 10-year period, though in many of these his roles are so small that it's a miracle he was credited at all (and in 2 of which he couldn't be found).
He seems like someone who it will be very likely that there will be undocumented roles to be found - as always time will tell. I think he bears some resemblance to Italian generico Severino D'Ottavi.
- Madrugada .... Doctor (credited)
1959 - El Lazarillo de Tormes .... Priest (credited as "Manuel Braña")
- La vida alrededor .... Judge (credited)
1960 - Ama Rosa .... (credited, but not found)
- La paz empieza nunca .... Man at the breakfast table (credited)
- Sólo para hombres .... Member of parliament (credited)
1961 - Los pedigüeños .... Bar customer discussing plans (uncredited)
- Mi noche de bodas .... Doctor (credited)
- Siempre es domingo .... Secretary of Carlota's father (credited)
1962 - El grano de mostaza .... Employee delivering message (credited)
- El hijo del capitán Blood .... Man at the dock (credited)
- Escuela de seductoras .... (credited, but not found)
1963 - Juego de hombres .... role unknown (poster credit as "Antonio Brañas")
- Los guerrilleros .... Man of some importance (credited)
- Millonario por un día .... Decorator (credited)
1964 - Como dos gotas de agua .... Paco (credited)
- La historia de Bienvenido .... Anita's grandfather (credited)
1965 - Muere una mujer .... Porter (credited)
1967 - El próximo otoño .... Priest (credited)
- Luna en la serranía (1961 short film) IMDb