Forum:Can anyone please answer this.. (Special Summons Confusions)

I would like to ask.. If i have a "Fossil Dyna Pachycephalo" face up on field, and one tuner on the field, for example "Scrap Beast" Can i Synchro Summon, for example "Stardust Dragon" (8 stars) by using "Fossil Dyna Pachycephalo" (4 stars) and "Scrap Beast" (4 stars)??? Some of my friends said can while others say cannot. Could anyone tell me the real answer for this.. Some of my friends say can because by using "Fossil Dyna Pachycephalo" as synchro material, it's no longer on field so the effects is no longer activated.. But some of my friends say cannot because "Fossil Dyna Pachycephalo" is on the field at the first place.. In my opinion, i think both explaination got points, but which one is the correct one??

PLEASE HELP ME!! Ebby