The armor of armored fish started out as part of the nervous system

Cells from the developing spinal cord make the sturgeon's bony, armored plates.

https://arstechnica.com/science/2023/07/the-armor-of-armored-fish-started-out-as-part-of-the-nervous-system/?utm_brand=arstechnica&utm_social-type=owned&utm_source=mastodon&utm_medium=social