A group of turtles is called a "bale".
A group of turtles is also called a "dole".
A group of female turtles or hatchlings is called a "nest".
A group of tortoises is called a "creep".
The largest species of turtle ever was called Archelon.
The largest living species is the Leatherback Sea Turtle, Dermochelys coriacea.
The smallest species is actually avery contested topic. As of right now, it is between the Speckled Padloper, Chersobius signatus, and the Bog Turtle, Glyptemys muhlenbergii.
Less of a fun fact, but, as of now, the rarest animal in the world is the Yangtze Giant Softshelled Turtle, Rafetus swinhoei, which only has 3 known extant specimens.
The Yangtze Giant Softshelled Turtle is also the largest freshwater turtle, followed closely by the Alligator Snapping Turtle, Macrochelys temminckii.
More coming soon...