Turtles are basically reptiles that belong to the order of Testudine. The turtles draw their line of existence somewhere down to the period of Mesozoic, which is said to be approximately 200 million years ago. It was assumed that they are the only existing branch that belongs to the ancient clade Anapsida, which comprises of groups like procolophonoids, millerettids, protorothyrids and pareiasaurs.
All anapsid skulls are deficient of a sequential aperture, while all other existing amniotes have sequential openings. It is said that most anapsids have wiped out in the late Permian period, apart from procolophonoids and probably the precursors of the testudines. The most primitive known contemporary turtle is proganochelys, though this species by now had many sophisticated turtle character, and thus most likely had many millions of years of previous "turtle" fruition and species in its descent.
All anapsid skulls are deficient of a sequential aperture, while all other existing amniotes have sequential openings. It is said that most anapsids have wiped out in the late Permian period, apart from procolophonoids and probably the precursors of the testudines. The most primitive known contemporary turtle is proganochelys, though this species by now had many sophisticated turtle character, and thus most likely had many millions of years of previous "turtle" fruition and species in its descent.