This Fossil Friday features the enigmatic Permian fossil Helicoprion bessonovi, which certainly ranks among the strangest creatures ever to haunt the prehistoric seas. It is an extinct genus of giant cartilaginous fish whose fossils have baffled scientists for over a century. Known primarily from a single bizarre type of structure — the “tooth whorl” — this creature’s evolutionary relationships, biology, and even basic anatomy have been hotly debated. The saga of Helicoprion is a case study in scientific persistence, misinterpretation, reinterpretation, wild speculation, and surprising discoveries. It also highlights the limits of our understanding of biological innovation, as the origins of its spiral jaw remain deeply enigmatic.

The Tooth Whorl: An Enigma from the Start

The story begins in 1899, when Russian geologist Alexander Karpinsky described a fossilized spiral from the Permian period of Kazakhstan. He named the creature Helicoprion (“spiral saw”) and, like many of his contemporaries, assumed it was some sort of ammonite — a type of coiled-shelled mollusk. This interpretation was understandable; after all, no one had ever seen anything like it. The tooth whorl was not attached to any recognizable skeleton, and its bizarre geometry defied easy explanation.

As more and better-preserved whorls were recovered from the Lower and Middle Permian (ca. 290–270 million years ago) around the globe, paleontologists realized the structure was dental, not molluscan. This feeding apparatus can be 20 inch long and contain up to 180 teeth. Early 20th-century reconstructions placed the tooth whorl outside the mouth, like a buzz saw on the snout or even the dorsal fin. Some speculated that this structure served as a kind of mimicry to attract ammonites as prey. These interpretations now seem laughable, but at the time, they reflected the very real difficulty of reconstructing an animal from such an unusual fossil. And who knows how laughable our up-to-date reconstructions would seem if we had a time machine and could compare them to the actual living animals.

The Long Road to Understanding

By the mid-20th century, scientists had recognized that Helicoprion was a cartilaginous fish, a relative of sharks and rays. However, its body remained mysterious because cartilaginous skeletons rarely fossilize. Only the tooth whorl — a spiral of continually replaced teeth embedded in cartilage — was consistently preserved. Without a clear context for the whorl, paleontologists were left to speculate wildly about its placement and function.

One influential reconstruction from the 1960s placed the whorl at the tip of the lower jaw, suggesting Helicoprion used it to slice through prey like a circular saw. This interpretation persisted for decades, but as more sophisticated imaging techniques became available, a new picture began to emerge.

About ten years ago, CT scans of a particularly well-preserved fossil revealed that the tooth whorl was located entirely within the lower jaw, anchored at its base (Tapanila et al. 2013, Tapanila & Pruitt 2013), somewhat similar to a previous suggestion by Lebedev (2009). This configuration suggested a completely different feeding mechanism. Rather than acting as an external buzz saw, the teeth spiraled inward and functioned like a conveyor belt (Ramsay et al. 2014). As the jaw closed, prey would be pulled deeper into the spiral, sliced by the sharp teeth, while the upper jaw surprisingly turned out to have been toothless. The rest of Helicoprion’s body may have resembled a streamlined shark, though no soft tissue impressions have been found to confirm this common reconstruction. Based on the size of the jaw apparatus scientists estimated that Helicoprion likely reached 16-26 ft in length, thus similar to the largest living sharks (Lebedev 2009).

Phylogenetic Puzzles: A Chimaera in More Ways Than One

Phylogenetically, Helicoprion and its related genera of the extinct Eugeneodontida are now placed within the Holocephali, a group of cartilaginous fish that includes modern chimaera or ratfish (Tapanila et al. 2013). This recent new systematic placement was quite unexpected, as most researchers had long assumed it was a strange kind of shark. The holocephalans are a highly specialized lineage, and Helicoprion represents an extreme early offshoot within this group. The tooth whorl’s placement, replacement mechanism, and integration into the jaw are unlike anything seen in modern holocephalans or their shark relatives. So much for an alleged correlation of similarity and evolutionary relationship.

An Evolutionary Conundrum

The greatest mystery of Helicoprion is how its tooth whorl evolved. Modern cartilaginous fish replace their teeth continuously, but the arrangement of these teeth in a spiral, with older teeth retained indefinitely, is unique to Helicoprion and its close relatives. This raises numerous questions: What intermediate forms led to the development of the spiral? How did this structure become integrated into the lower jaw? What selective pressures could have driven such a bizarre adaptation?

Apart from a few genera with shorter whorls, no fossil evidence has yet been found to show transitional stages in the evolution of the whorl, leaving its origins a profound puzzle. The functional geometry is equally perplexing: the whorl was effective for slicing soft prey like cephalopods, but how such a specialized system evolved from the simpler jaws of ancestral cartilaginous fish remains speculative at best. Some scientists suggest it may have started as an overgrowth of teeth in a more typical jaw, gradually becoming coiled through developmental processes, but this hypothesis lacks any direct empirical support.

There is no doubt that Helicoprion’s spiral jaw is a masterpiece of adaptation, but also a profound enigma. Scientists have solved many aspects of its biology, but the origins of its unique dental structure remain elusive. For now, Helicoprion serves as a reminder that the fossil record holds secrets that challenge common theories of biological origins. Could intelligent design better explain this weird feeding apparatus? Of course, but this is not allowed in mainstream science to even be considered as a possible option. “Streng verboten” as we say in German.

References

• Karpinsky АP 1899. [On the edestid remains and the new genus Helicoprion]. Notes of the Imperial Academy of Sciences (Physics and Mathematics section) 8(7), 1–67, pls I–IV. [In Russian]
• Lebedev OA 2009. A new specimen of Helicoprion Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function. Acta Zoologica 90(Suppl. 1), 171–182. DOI: https://doi.org/10.1111/j.1463-6395.2008.00353.x
• Ramsay JB, Wilga CD, Tapanila L, Pruitt J, Pradel A, Schlader R & Didier DA 2014. Eating with a saw for a jaw: Functional morphology of the jaws and tooth-whorl in Helicoprion davisii: Jaw and Tooth Function in Helicoprion. Journal of Morphology 276(1), 47–64. DOI: https://doi.org/10.1002/jmor.20319
• Tapanila L & Pruitt J 2013. Unravelling species concepts for the Helicoprion tooth whorl. Journal of Paleontology 87(6), 965–983. DOI: https://doi.org/10.1666/12-156
• Tapanila L, Pruitt J, Pradel A, Wilga CD, Ramsay JB, Schlader R & Didier DA 2013. Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion. Biology Letters 9(2), 1–4. DOI: https://doi.org/10.1098/rsbl.2013.0057