Introducing: Punk & Emo

Researchers have unearthed two fossils, named Punk and Emo, and with them, shifted scientific notions about the complexity and adaptability of ancient molluscs.

Molluscs are a numerous and incredibly diverse group of animals – from the tiny slug in your garden to the giant squid in the deep ocean. But understanding the evolutionary history of these marvelous animals has remained a challenge for scientists. Molluscs’ often fleshy bodies rarely fossilise, making the ancient record for many of these creatures incredibly scarce. That’s why the discovery of Punk and Emo is so important.

Punk ferox and Emo vorticaudum were found in a fossil deposit of organisms from the open ocean, dating from around 430 million years ago. And unlike many of their ancient mollusc cousins, their soft-tissues were preserved. Both these rebellious fossils are aculiferans – a group of molluscs that include chitons, animals with eight articulating shell plates along their backs, and aplacophorans, which are worm-like molluscs that don’t have a shell at all.

An international research team, including Senckenberg malacologist and SOSA co-chair, Prof. Dr. Julia Sigwart, studied Punk and Emo, looking for insights on how this group evolved. The study, led by Dr Mark Sutton from the Department of Earth Science and Engineering at Imperial College London Frankfurt, analyzed the fossils using state-of-the-art imaging techniques and created digital 3D models of the animals. These reveal that early molluscs had a much greater variety of characteristics, such as appearance and locomotion strategies, than previously assumed. Dr Sutton said:

“Molluscs are one of the largest and most diverse animal groups on Earth. However, early Aculiferan molluscs are much less well-known than some of their relatives. We have limited information about this group, and for a very long time, we assumed they were rather basic, simple and primitive.

“Retrieving fossils that are so exceptionally well preserved and reveal details of the soft tissues is extremely rare. We have been able to create ‘virtual fossils’ – 3D digital models – providing us with a gold mine of information and helping us understand that the branch of molluscan evolution containing Emo and Punk was much more evolutionarily rich and diverse than we thought; as much as other mollusc groups.”

The team used two different methods to get a clear picture of the fossils both inside and out. First, they used X-ray scanning to get a detailed look at the internal structures without causing any external damage. They then carefully ground the fossils down in very thin layers, taking photos at each step to create a 3D image of the external features.

 Researchers found both fossils had smooth undersides, suggesting that they lived on the sea floor, and they both possessed some unique features and unconventional movement strategies.

“‘Emo’ was fossilized in a folded posture – apparently it moved like a caterpillar by holding on with its spines and pushing itself forward,” explains Prof. Dr. Julia Sigwart, Head of the Malacology Section at the Senckenberg Research Institute and Nature Museum Frankfurt. “We don’t know how ‘Punk’ moved around. But we have discovered that it had a ridge-like foot that is not found in modern molluscs.”

As for their names, this too comes from the animal’s unique characteristics. “The names Punk and Emo were actually our initial pet names for these ancient molluscs, inspired by some of their unique features and individuality. Punk in particular, with its spiky appearance, clearly resembles a rebellious punk rocker. Then someone else said ‘that one is a punk, but this one is more emo’ and that sealed the names,” said Dr Sutton.

While Punk resembles worm-like molluscs with long spines, it also has a broad foot and gills like chitons. Emo, similarly worm-like with a long body and spines, also features shells and a compressed body similar to chitons.

 This mix of features helps researchers better understand the mollusc evolutionary tree – pointing to a story that involves more complexity and diversity than previously thought. Check out the Nature article here: https://www.nature.com/articles/s41586-024-08312-0