Order Summary for Pleuronectiformes

  Main Ref
:
  Order
:
Pleuronectiformes flatfishes
  Class
:
Actinopteri
  Sister Order
:
Tetraodontiformes 15 M years
  Ref.
:
  First Fossil Record
:
late Tertiary
  Occurs in
:
Marine
Fresh
Brackish
  Remark
:
Adults not bilaterally symmetrical, with one eye migrating to the other side of the cranium; dorsal and anal fins with long bases, dorsal fin base overlapping at least the neurocranium except in Psettodes; body highly compressed, somewhat rounded on eyed side and flat on blind side; eyes can protrude above body surface allowing fish to see when buried in the substrate; usually six or seven branchiostegal rays, rarely eight; body cavity small; adults almost always without swim bladder; scales cycloid, ctenoid, or tuberculate. About four species probably occur in freshwater, while another 20 species that are normally marine occasionally enter freshwater.
  Class etymology
:
Greek aktis = ray, thunderbolt, beam + Greek pterygion, diminutive of pteryx = wing, fin. Ref. 45335.
  Order etymology
:
Greek, pleura = similar, ribe, side + Greek, nektos = to swim + Latin, forma = shape. 1849 (Ref. 45335).
  Families
:

Ref.
[ e.g. 9948]                       
Glossary
                    [ e.g. cephalopods]

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