Myliobatiformes is one of the four orders

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of batoids

Batoidea

Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...

, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes

Rajiformes

Rajiformes is one of the four orders of batoids, flattened cartilaginous fishes related to sharks.Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion...

, but more recent phylogenetic studies have shown that the myliobatiforms are a monophyletic group, and that its more derived

Derived

In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...

 members evolved their highly flattened shapes independently of the skate

Skate

Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....

s.

Classification

Nelson's 2006 Fishes of the World arranges the Myliobatiformes as follows:

• Suborder Platyrhinoidei
  • Family Platyrhinidae
    Platyrhinidae
    Platyrhinidae is a family of rays in the order Myliobatiformes, commonly known as thornbacks due to their dorsal rows of large thorns. They resemble guitarfishes in shape, but are in fact more closely related to stingrays.-Genera and species:...
    
     (thornbacks)
• Suborder Zanobatoidei
  • Family Zanobatidae (panrays)
• Suborder Myliobatoidei
  • Superfamily Hexatrygonoidea
    • Family Hexatrygonidae (sixgill stingrays)
  • Superfamily Urolophoidea
    • Family Plesiobatidae (deepwater stingrays)
    • Family Urolophidae (round stingrays)
  • Superfamily Urotrygonoidea
    • Family Urotrygonidae
      Urotrygonidae
      Urotrygonidae is a family of rays in the order Myliobatiformes, commonly referred to as the American round stingrays or round rays. They are native to the tropical and warm temperate marine waters of the Americas. The two genera in this family were formerly placed within the family Urolophidae,...
      
       (American round stingrays)
  • Superfamily Dasyatoidea
    • Family Dasyatidae (whiptail stingrays)
    • Family Potamotrygonidae
      Potamotrygonidae
      River stingrays are Neotropical freshwater fishes of the Potamotrygonidae family .They are native to northern, central and eastern South America, living in rivers that drain into the Caribbean, and into the Atlantic as far south as the Río de la Plata in Argentina...
      
       (river stingrays)
    • Family Gymnuridae (butterfly rays)
    • Family Myliobatidae (eagle rays, manta rays)