(Gymnura micrura)

Class: Chondrichthyes
Order: Myliobatiformes
Family: Gymnuridae


Distribution and Habitat

  • They are found in the western and eastern parts of the Atlantic Ocean (Maryland to Brazil) and the Gulf of Mexico.
  • They are most commonly found in neritic waters, but are also known to enter brackish estuaries and hypersalinelagoons.

They have a range that extends from the continental shelf to 40 meters deep in tropical and warm waters.

About the fish

  • It is a species of  Batoid cartilaginous fish.
  • Gymnura is derived from Greek roots and translates into ‘naked tail’.
  • Its has overall diamond shape with flat body and pectoral fins that are wider than their length.
  • The edges of the disc are concave.
  • The ventral side is lightly colored while the dorsal side is variable in color.
  • They tend to use countershading to blend in with the bottom of their environments in order to hide from predators and to catch prey.
  • Its tail is short and has 3 to 4 dark lines that are referred to as crossbars.
  • The caudal fin is never present and a variable number of tubercles can be found on larger specimens.
  • Females are bigger than their male counterparts
  • Maximum length (120 cm)     Female 50 cm      Male 42 cm
  • They prefer habitats that have either sandy or muddy bottoms.
  • They use internal fertilization which is the process of the male inserting his claspers into the female’s cloaca to fertilize the eggs.
  • Exhibit ovo-viviparity, the offspring develop inside the mother and the young are histotrophs.
  • They prey mainly on bony fishes, crustaceans, bivalve mussels and polychaetes.
  • They use a structure called the lateral line canal; it is located on the dorsal side from the head to the pectoral fins,  that assists the rays in detecting changes in water movement.
  • The upper jaw consists of 6 to 120 teeth and the lower jaw has 52 to 106 teeth; each jaw contains 6 to 8 simultaneously functioning rows.
  • Swimming habits use small amplitude undulations of their fins when they are swimming along the bottom, but switch to an oscillatory approach when they are swimming freely in the water.
  •  They are currently classified as data deficient by the IUCN.