I thought the definite article was used before the posessive, I.e. o meu elefante in mainland portuguese, at least
You can use it or not.
"Teu elefante" and "O teu elefante" means the same.
I think in Brazilian Portuguese is much less used, as in this case. In EP you would use it.
Thanks. I've seen road signs in Portugal stating (excuse my spelling if it is incorrect) "guias señor as para sua seguranca" when I would have expected pela instead of para
No problem. You mean "guias sonoras para sua segurança". Para = for Por = by
So it's "para" (for your safety).
When talking about "Tu", that's almost true. (But some regions in the country still use it, mostly in the south).
Now, when talking about "Teu/Tua", "Teus/Tuas", they are indeed used.
But there's no rule to decide between "teu" and "seu".
However, "Teu" assures you're talking about the second person, not about one of the other objects in the sentence (if there are other objects).
They are probably both right. Just different ways of saying it according to regional differences. If you wish to know which is closer to a standard BP, if there is even such a thing, you'd have to ask a Brazilian guy.