THE ANIMAL FILES

Greenland shark

Somniosus microcephalus

A centuries-old shark’s age is an estimate built from eye tissue, not a counted birthday.

Greenland sharks inhabit cold waters and combine scavenging with predation. Different upper and lower teeth help hold and cut food. Radiocarbon work on eye lenses provides evidence of exceptional longevity, with wide uncertainty around individual ages.[1]

Follow the evidence ↓
Greenland shark
Image: Gervais et Boulart · Commons · Public domain
Waters
Cold northern seas[1]
Teeth
Upper teeth anchor; lower teeth cut[1]
Age evidence
Radiocarbon analysis of eye-lens material[1]

Two jaws, different edges

Thin pointed upper teeth anchor into food, while broader interlocking lower teeth cut. Rolling during feeding can help remove pieces from large carcasses. The dentition therefore suits processing as well as grabbing, without requiring every meal to consist of a large animal killed by the shark itself.[1]

Slow movement and uncertain hunts

Fish and seal remains occur in stomach records. Given slow swimming, researchers have proposed taking sleeping or vulnerable marine mammals, alongside scavenging. Those proposals should not be written as observed routines for every seal meal. Smell and the lateral line provide information in dim waters.[1]

Dating a long life

Radiocarbon measurements of eye-lens material yield age estimates spanning centuries for large individuals. The uncertainty is substantial, so one headline age is not an exact birth year. Slow growth and delayed maturation make age estimation ecologically important, while the molecular reasons for longevity remain an active research topic.[1]

A COMMON MIX-UP

Can an estimated age be treated as an exact birth date?

No. Radiocarbon-based estimates have uncertainty that must be retained.[1]

TRY A LITTLE REASONING

Why do seal remains alone not show how a shark caught the seal?

Reveal the explanation

Stomach contents identify food, but do not distinguish active capture from scavenging or reconstruct the encounter.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Somniosus microcephalus (adapted and translated; exact revision)
  2. NCBI Taxonomy — Somniosus microcephalus (identity and game lineage)

Last fact check:

One discovery leads to another

Spiny dogfishA shark’s spines are not its teeth.Squalus acanthias ↗Frilled sharkAn eel-like outline belongs to a shark.Chlamydoselachus anguineus ↗Blue sharkBlue above, pale below: an ocean swimmer has more than one colour.Prionace glauca ↗