The 13th Dynasty was a direct continuation of the preceding 12th Dynasty, with its first ruler believed to be a son of Amenemhat IV. Kim Ryholt proposes that the demarcation between the two dynasties reflects the rise of the independent 14th Dynasty in the eastern Delta, an event which, he proposes, occurred during Sobekneferu's reign. As direct heirs to the kings of the 12th Dynasty, pharaohs of the 13th Dynasty reigned from Memphis over Middle and Upper Egypt, all the way to the second cataract to the south. The power of the 13th Dynasty waned progressively over its 150 years of existence and it finally came to an end with the conquest of Memphis by the Hyksos rulers of the 15th Dynasty, c. 1650 BC.