Different authors emphasize different key information as the base for the classification of all the living and extinct turtle families and came up with different systems.

Turtles - testudines - are mainly divided into three suborders:

1. Amphichelydia (entirely extinct)
2. Cryptodira (the dominant turtles in the world today)
3. Pleurodira

Given below is the classification system as proposed by Mlynarski, 1969 :

Order: Testudines
Suborder : Amphichelydia
Suborder : Cryptodira

Superfamily: Chelydroidea

• Families : Dermatemyidae, Sinemydidae, Chelydridae
  Kinosternidae ( Kinosterninae, Staurotypinae )

Superfamily: Testudinoidea

• Families : Emydidae ( Batagurinae, Emydinae ),
  Platysternidae, Ptychogastridae, Testudinidae

Superfamily: Chelonioidea

• Families : Toxochelyidae ( Toxochelyinae, Lophochelyinae, Ostopyginae ),
  Protostegidae ( Chelospharginae, Protosteginae ),
  Desmatochelyidae, Cheloniidae

Superfamily: Dermochelyoidea

• Families : Dermochelyidae

Superfamily: Trionychoidea

• Families : Carettochelyidae ( Anosterinae, Carettochelyinae ),
  Trionychidae ( Cyclanorbinae, Trionychinae )

• Families : Pelomedusidae, Eusarkiidae, Chelidae

The common names of the main turtle groups are:

Any turtle can be identified by following the keys to turtle families and genera, which can be found in Dr. P.C.H.Pritchards " Encyclopedia of turtles " ( page 9 ).