

Fun facts about horseshoe crabs:
- Not crabs, in fact not even close. Chelicerates like the arachnids.
- Have photoreceptors in their “tail” (telson).
Edit: For some taxonomic context, king crabs are closer than shrimp are closer than woodlouse are closer than barnacles are closer than bees are closer than myriapods (centipedes and millipedes) are closer than horseshoe crabs to being crabs.

















According to Wiktionary, the etymology of “shark” beyond Middle English is unknown – and even there, we only see it once in 1442.
Edit: the Online Etymology Dictionary has more.