Impossible to ID based on a picture Guillermo. Proxima-group I assume...
And are you sure about your estimate of the size? Cause that would limit the choices a lot... to zero.
Thanks Andre,
The trouth is that I do not remember very good. It was not larger than 15 mm, but it could be smaller than 13. Probably around 10. I would have to measure a similar flower next time I go to the field.