Elysia marginata
Two species of sea slug from the order Sacoglossa, Elysia atroviridis and Elysia marginata, are able to completely regenerate their bodies - including heart, kidney, intestine and reproductive organs.
The head can survive for up to a month, surviving autonomously thanks to its ability to photosynthesize like plants.
https://www.livescience.com/decapitated-sea-slugs-regrow-entire-body.htmlhttps://www.theguardian.com/environment/2021/mar/08/keep-your-head-the-self-decapitating-sea-slugs-that-regrow-their-bodies-hearts-and-all