Clypeaster subdepressus, more commonly known as the sea biscuit or sand dollar, is a common coastal Echinoid, or sea urchin. Echinoderms like these are deuterostomes like us, meaning we are more closely related to them than the seemingly more similar arthropods, annelid worms and molluscs, who at least have a complete nervous system and unfailingly both a mouth and and anus.

This charming video portrays the beautiful development cycle of a sea biscuit from fertilisation to final metamorphosis....