Scientists say they are stunned after discovering sea spiders have the ability to grow new reproductive organs and an anus.
Experts already knew that when the arthropods lose legs, they can regrow them.
But in a development that will no doubt inspire the next generation of Spider-Man stories, a study has found the underwater creatures have regenerative powers which extend to their entire bottom halves.
"Nobody had expected this," said the lead researcher behind the breakthrough in understanding, Professor Gerhard Scholtz.
Other arthropods - invertebrates with no internal skeleton or backbone, but which do have an exoskeleton - such as centipedes and crabs, are also capable of regrowing limbs.
Some creatures can go further, with starfish able to regenerate their entire bodies on occasion - and lizards able to produce a new tail.
"If you look at the animal kingdom, the capability of regeneration differs very much in various groups of animals," Professor Scholtz told Sky News.
"Flatworms, for example, can regenerate their whole body from a limited amount of tissue.
"On the other hand, us - mammals - cannot regenerate much - liver, tissue, skin, but apart from that very little.
"For arthropods - crustaceans, insects, myriapods, and types of spider - it was entirely unknown that they could regenerate body parts other than limbs."
The study, which has been published in the Proceedings of the National Academy of Sciences journal, saw the hind limbs and backends of 23 sea spiders amputated.
While four older spiders did not regrow anything, most of the 19 juveniles did.
Sixteen of them regenerated at least one lost body part, 14 recovered their posterior, and 90% survived long-term despite the amputations.
Until now, it was thought that the spiders' hard exoskeleton prevented any regeneration beyond the limbs, added Professor Scholtz. But his research found the creatures were recreating body parts within "several weeks or months".
The regenerations did not always go smoothly - some spiders were a leg or two short.
Hope 'always there' for amputation breakthrough
Professor Scholtz, of Humboldt University of Berlin's Institute for Biology, said the findings should inspire further study into different species.
"One has to look to other arthropods and whether they can do the same," he said.
He is planning further research by reproducing the study with insects, crabs and other crustaceans.
And the breakthrough could be transformative for health care.
Such research could one day advance treatments for human amputees.
"The hope is always there," said Professor Scholtz.
"I don't think the sea spiders will play a crucial role, but who knows? The more you know about regeneration in the animal kingdom, the better you might be able to use it for medical treatment."