Original: Other types of rays also referred to as stingrays are the river stingrays (family Potamotrygonidae), the round stingrays (families Urolophidae and Urotrygonidae), the sixgill stingray (family Hexatrygonidae), and the deepwater stingray (family Plesiobatidae). For clarity, the members of the family Dasyatidae are sometimes called whip-tail stingrays.
Simplified: They give birth to baby stingrays.