I'm told sometimes with thin women perhaps the number of bony parts protruding could indicate twins. what bony parts are referred to as indication?

Diagnosis of twins: Ideally every pregnant woman should have at least one ultrasound, the standard way to diagnose twins. Feeling someone's belly for twins is hogwash. "Increased maternal age" as a genetic risk factor technically begins at 40, but would increase the need for U/S to detect problems early. This may allow for treatment even before birth. See: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC27416/

Not true.: There is no such thing. In fact it is very difficult to find out about twins without a proper examination by a professional. Even then it might take an ultrasound for correct diagnosis.