Order Summary for Petromyzontiformes

  Main Ref
:
  Order
:
Petromyzontiformes lampreys
  Class
:
Cephalaspidomorphi
  Sister Order
:
Chimaeriformes 455 M years
  Ref..
:
  First Fossil Record
:
late Ordovician
  Occurs in
:
Marine
Fresh
Brackish
  Remark
:
No bone; seven pairs of external lateral gill openings; eyes lateral (except in Mordacia; tail isocercal in adults, hypocercal in ammocoete larvae; body naked, eel-like; no paired fins.
  Classetymology
:
Greek, Kephale = head + Greek, aspidos = shield + Greek morphe= shape. Ref. 45335.
  Orderetymology
:
Latin, petra = stone + Greek, myzo = to suckle + Latin, forma = shape (Ref. 45335).
  Families
: