Why Did This Shark Have a Spiky Back?

Picked one by one from a mixed channel. Transcript check: both title readers certain; 5 of 5 sampled certain picks confirmed by transcript, none failed. Channel rule: Include only paleontology and natural-history explainers that walk through a specific described species, published paper or biological phenomenon, are titled descriptively without shouty caps or withheld-information hooks, and exclude anything that is cryptid/cryptozoology, a clip, a trailer, a raw footage reel or a series episode with a hype title.

A 19-minute video from EDGE Science: “Why Did This Shark Have a Spiky Back?”.

Video by EDGE Science, played through YouTube's embedded player.