Complex sentence: The Sasanian Dynasty (or the Imperial House of Sasan) ruled the Sasanian Empire from 224 to 651, beginning with Ardashir I, that named the dynasty as "Sasanian" (also known as Sassanid) in honour of his grandfather, Sasan.
Split into simpler sentences: The Sasanian Dynasty (or the Imperial House of Sasan) ruled the Sasanian Empire from 224 to 651. It began with Ardashir I, who named the dynasty as "Sasanian" (also known as Sassanid) in honour of his grandfather, Sasan.