Rav Yehuda Gaon was head of the yeshiva in Pumbedita [(and Shada"k page 36b and 58b says head of the yeshiva in Mata Mechasia as in year 4496)] around year 4480 and ruled for about 18 years until year 4498 [(Tzemach David). He composed the book Basar Al Gechalim (see above year 4527)].