Complex sentence: Kinosterninae is a subfamily of the Kinosternidae family of aquatic turtles which contains the genera "Kinosternon" and "Sternotherus", which are native to much of the United States and northern Mexico.
Split into simpler sentences: Kinosterninae is a subfamily of the family Kinosternidae, a family of aquatic turtles. Kinosterninae contains the genera "Kinosternon" and "Sternotherus", which are native to much of the United States and northern Mexico.