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 a very 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...