Define the yak turtle e symmetrically

Turtles are reptiles of the order Testudines. They are characterized by a special bony or cartilaginous shell developed from their ribs that acts as a shield. "Turtle" may refer to the order as a whole (American English) or to fresh-water and sea-dwelling Testudines (British English).Testudines includes both extant (living) and extinct species. Its earliest known members date from the Middle Jurassic.[1] Turtles are one of the oldest reptile groups, more ancient than snakes or crocodilians. Of the 360 known extant species,some are highly endangered