Latin verbal system: how perfect and aorist joined in the new perfect?

[Rick Mc Callister]

Didn't diphthongation in Spanish only affect "open /O/", not "closed /o/"
and wasn't /o/ from /au/ a "closed /o/"?

btw: Portuguese has auru- > ouro, causa- > cousa > coisa, etc.

[snip]

>in certain situations in both Spanish
>and Italian, stressed /o/ was diphthongized {fuego, fuoco, uomo &c} but
>that didn't happen when the /o/ resulted from CL /au/ {oro, not *uoro}.