Chordata · chordates

Sei whale

Balaenoptera borealis

Balaenopteridae · rorqualsIUCN: Endangered
Sei whale
Photo: Christin Khan, NOAA / NEFSC · Public domain · Wikimedia Commons · resized

A fast, elusive rorqual that skims copepods near the surface.

Fun factSei whales sometimes appear in Northeast waters when copepods bloom.

Waters
Worldwide, Northeast US
Depth zone
Open-ocean surface waters
Diet
Copepods & krill
Size
Up to 20 m

Classification

Chordata › Mammalia › Artiodactyla › Balaenopteridae

  1. Kingdom Animalia animals
    • Many-celled organisms that eat other living things for energy (heterotrophs)
    • Cells have no cell walls
    • Most can move at some stage of life
  2. Clade Bilateria bilateral animals
    • Body has a left and right side that mirror each other (bilateral symmetry)
    • Head end with concentrated nerves; three tissue layers
    • Includes about 99% of all living animal species
  3. Clade Deuterostomia deuterostomes
    • In the embryo, the first opening becomes the anus and the mouth forms second
    • Includes echinoderms and chordates
  4. Phylum Chordata chordates
    • At some stage of life: a stiffening rod along the back (notochord)
    • A hollow nerve cord along the back (dorsal)
    • Slits in the throat (pharyngeal slits) and a tail past the anus
  5. Subphylum Vertebrata vertebrates
    • A skull (cranium) protecting a brain
    • Backbone or similar support around the nerve cord
    • Includes fishes, amphibians, reptiles, birds, and mammals
  6. Infraphylum Gnathostomata jawed vertebrates
    • Jawed vertebrates: jaws formed from gill arches
    • Paired fins or limbs
    • Includes all fishes except hagfish and lampreys, plus all tetrapods
  7. Superclass Osteichthyes bony vertebrates
    • Bony vertebrates: skeleton made largely of bone
    • Most have a lung or swim bladder
    • Includes ray-finned and lobe-finned fishes and all tetrapods
  8. Clade Sarcopterygii lobe-finned vertebrates
    • Lobe-finned: fleshy fins with bones like those of limbs
    • Includes coelacanths, lungfishes, and all tetrapods
  9. Clade Tetrapoda four-limbed vertebrates
    • Four limbs with fingers and toes (or descended from animals that had them)
    • Breathe air with lungs
  10. Class Mammalia mammals
    • Mammals: hair at some stage of life
    • Females nurse their young with milk (mammary glands)
    • Three small bones in the middle ear
  11. Superorder Laurasiatheria whales, carnivorans & kin
    • Large group of placental mammals including whales, carnivores, bats, and hoofed animals
  12. Order Artiodactyla even-toed hoofed mammals (whales included)
    • Even-toed hoofed mammals (cows, deer, hippos) and their relatives the whales
    • Whales evolved from land ancestors close to hippos
  13. Infraorder Cetacea whales, dolphins & porpoises
    • Whales, dolphins, and porpoises: fully aquatic, with flippers and a horizontal tail fluke
    • Breathe through a blowhole on top of the head
    • Thick blubber instead of fur
  14. Parvorder Mysticeti baleen whales
    • Baleen whales: no teeth as adults
    • Filter food through plates of baleen (keratin)
    • Two blowholes
  15. Family Balaenopteridae rorquals
    • Rorquals: long throat pleats that expand to gulp water and prey
    • Includes blue, fin, and humpback whales
  16. Genus Balaenoptera
    • Species in the same genus are very close relatives and often look alike.
  17. Species Balaenoptera borealis Sei whale

Closest relatives in the guide