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🤯 Did You Know (click to read)
Shark teeth fossilize more readily than cartilage skeletons, providing much of the evidence for ancient shark lineages.
Fossil evidence places hexanchiform sharks in the Early Jurassic period, over 180 million years ago. Teeth and skeletal fragments show that their distinctive multi-gill anatomy has persisted with relatively minor modification.
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💥 Impact (click to read)
While many marine lineages vanished during ancient extinction events, hexanchiform sharks endured, likely aided by deep-water refuges less affected by surface climate swings.
The persistence of this body plan across geological eras highlights the deep sea as an evolutionary archive. Sixgills are not evolutionary experiments—they are survivors of planetary reset events.
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