Imagine a two-meter sea serpent armed with 300 needle-like teeth, enduring a three-and-a-half-year pregnancy in the freezing black depths of the ocean. It sounds mythological, but it has been haunting our oceans since before the dinosaurs went extinct.

This episode dives into the frilled shark (Chlamydoselachus anguineus), a creature so remote that humanity didn't even classify it until the late 1800s. We unpack its bizarre anatomy, its extreme adaptations to the abyss, and the painful irony that an animal which survived the asteroid impact is now threatened by accidental human bycatch.

• Why the "living fossil" label is misleading: fossil teeth found with pinecones in New Zealand reveal its ancestors lived in shallow coastal waters crushing mollusks
• How its rear-clustered fins, eel-like body, and amphistylic jaw let it swa ...