Paleontologists have discovered two new three-dimensionally preserved species of aculiferan mollusks that lived during the Silurian, revealing that the early mollusks were more complex and adaptable than previously known.
3D models of Punk ferox (top) and Emo vorticaudum (bottom) reconstructed as digital virtual fossils. Image credit: Mark Sutton, Imperial College London.
The two new aculiferan species, named Punk ferox and Emo vorticaudum, lived around 430 million years ago.
The specimens were found in the Silurian deposits in the county of Herefordshire, England.
They had distinctive spikes and other features that make them stand out from previously described early mollusks.
“Mollusks are one of the largest and most diverse animal groups on Earth,” said Dr. Mark Sutton, a paleontologist at Imperial College London.
“However, early aculiferan mollusks 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 molluskan evolution containing Punk ferox and Emo vorticaudum was much more evolutionarily rich and diverse than we thought; as much as other mollusk groups.”
Dr. Sutton and colleagues 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.
The 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.
The Emo vorticaudum fossil is preserved in a folded posture, suggesting that it moved like an inchworm, using its spines to grip and push forward.
Meanwhile, how Punk ferox was able to move remains unclear to the scientists, but they found it had a ridge-like foot, unlike any existing mollusk today.
“The names Punk ferox and Emo vorticaudum were actually our initial pet names for these ancient mollusks, inspired by some of their unique features and individuality,” Dr. Sutton said.
“Punk ferox in particular, with its spiky appearance, clearly resembles a rebellious punk rocker — and we thought Emo vorticaudum complemented it well.”
“While Punk ferox resembles worm-like mollusks with long spines, it also has a broad foot and gills like chitons.”
“Emo vorticaudum, similarly worm-like with a long body and spines, also features shells and a compressed body similar to chitons.”
“This mix of features helps us better understand the mollusk evolutionary tree — pointing to a story that involves more complexity and diversity than previously thought.”
The study was published in the journal Nature.
_____
M.D. Sutton et al. New Silurian aculiferan fossils reveal complex early history of Mollusca. Nature, published online January 8, 2025; doi: 10.1038/s41586-024-08312-0
