Djedefptah is not accounted for in many chronologies -- usually, Shepseskaf is listed as the last pharaoh of the fourth dynasty. However, many assume that Djedefptah is listed by Manetho as Tamphthis (which is probably a form of ptah-djedef, and grants him a reign of 9 years.

The Turin canon has an unnamed pharaoh after Shepseskaf who ruled for about two years. Djedefptah could fill this space. Not much else is known about him.

pharaohs

Sneferu
Khufu (Cheops)
Kauab
Djedefre
khafre (Chephren)
Bakare
Menkaure
Shepseskaf
Djedefptah