When scientists discover new prehistoric species, the fossils alone fail to conjure the creature in the flesh. It’s impossible to summon the entirety ancient shark from a single tooth, or some weird old rodent from a fragment of a jaw. This is where paleoart comes in, with illustrations that help you imagine how such an animal might have looked in its heyday. But very few of these visualizations dare to take one step further and help you imagine what it would be like to be caught, swallowed, and digested by that animal—until now.
Imagine you are a small living creature or a scrap of a dead one, drifting in the shallows over an innocuous patch of sand. But what is that? Suddenly that dimple in the sand has unfurled into a daunting pillar of a worm. But it this is not just any worm; it is Kraytdraco spectatus, an ancient penis worm that lurked in the sludge of the shallow seas swathing the Grand Canyon during the Cambrian. And K. specatus is about to eat you.
If you are confused about what exactly you just watched, and this penis worm’s whole deal, don’t worry. We’ll get to that. Besides, the worm was around six to eight inches long, so it really would not have been able to swallow much of you.
K. specatus is the star of a new paper recently published in Science Advances describing a handful of Cambrian fossils from the Grand Canyon. The other species described are a crustacean akin to a brine shrimp and a sluglike mollusk. But these creatures, fascinating as they surely are, did not receive a 3D rendering of what it would be like to be swallowed by them, and therefore are not the subject of this particular story.
This penis worm’s greatest champion is Giovanni Mussini, a paleontologist and doctoral student at Cambridge University. Mussini studies the creatures of the Cambrian, an era when complex life exploded in the world’s oceans about 540 million years ago. In this explosion, a mostly microbial world gave way to a diverse set of larger animals, some of whose anatomy and body plans persist to this day. “It’s a hinge of history between what comes before and what comes after,” Mussini said.
The Grand Canyon is more famous for its sweeping vistas than for its soft-bodied fossils, in part because paleontologists had yet to unearth any exceptionally preserved Cambrian creatures from the canyon. But Mussini had become interested in the Grand Canyon’s abundance of fine-grained shale, which dated to the Cambrian. In the early 2000s, a scientist managed to extract microbial fossils from Cambrian shale in the Grand Canyon. “They went a bit under the radar, because there was nothing fancy or revolutionary about them,” Mussini said, adding that the fossils comprised fragments of cuticles or algae. “But at the same time, they were really tantalizing, because they showed there was some potential for organic preservation.”
Mussini suspected that if researchers were to sample more widely and process the rocks more gently, they might recover the remains of larger, softer-bodied animals. Mussini visited the Grand Canyon on a collecting trip in September 2023, where he collected dozens of samples from the shale. The fossils he sought were too small to see with the naked eye, so he just collected fist-sized rocks that looked promising, meaning fine-grained and easily split. “Out of those 30-plus samples, I got two productive ones,” he said. “It’s a numbers game.”
Back in Cambridge, Mussini dunked the rocks in beakers of hydrofluoric acid, which mostly dissolved them. Then he sifted the residue to capture any fragments of fossils that may have lurked inside. This process was extremely time-consuming, as Mussini had to examine every single piece of residue under a microscope to ascertain what was a fossil. “They’re roughly the size of a period at the end of a sentence,” Mussini said.
He had already found some parts of a mollusk when he started finding lots of teeth. Each tooth was tiny and strange, with feathery, almost fractal projections on either side of the cusp. “Those struck me as very unusual from the start,” Mussini said. As the teeth mounted in number, he suspected they hailed from a filter feeder, as no predator would be impaling its prey with such frilly teeth. When Mussini began finding a second kind of a spiky, more heavy-duty tooth, he assumed he’d found the remains of two very different penis worms living in the same spot at the same time.
The plot twist arrived in the form of an articulated fossil, in which both types of teeth were arranged, as they appeared in real life, in the worm’s pharynx, a kind of ejectable throat. The two teeth types belonged to just one worm: K. specatus. Mussini realized the worm “probably had a pretty unique feeding style as a consequence,” and one that would be hard to understand from description alone. Luckily, he knew just the person to text.
By the time Rhydian Evans was 13, he’d already become fascinated by early paleontology. After reading a book by the Cambridge paleontologist Simon Conway Morris, Evans emailed Morris “a bunch of questions about stuff that I didn’t really understand,” he said. Eventually Evans met Morris in person and began doing his own research on the Cambrian. This research has yet to be published, in part because Evans just graduated high school this year.
Early on in Evans’s Cambrian obsession, he found the Royal Ontario Museum’s 3D models and videos of life from the Burgess Shale, which brought the prehistoric ocean to life, from submarine-shaped arthropods to other, more obscene penis worms. Evans was mesmerized, and taught himself how to use the open-source 3D software Blender to make his own models, which is how he connected with Mussini and offered to make paleoart for the researcher, if he should ever have a need.
Around a year ago, Mussini came calling. “He texted me about this crazy specimen that he’d found, of these thousands of teeth and just this extraordinary mechanism,” Evans said. “As a high school student, I was just happy to be invited,” he added. When Evans saw the articulated fossil specimens, however, he was confused. He knew it was a worm, and the specimen was indeed worm-shaped. But the teeth were pointing in the wrong direction, seemingly angled outward. That’s when Mussini explained that the penis worm had fossilized inside out, with its toothy ejectable pharynx retracted into its body. “I don’t think I fully understood what was going on until a decent way into making the thing,” Evans said.
Evans started by animating a single tooth, working with Mussini to nail down the shape. Then he made five more to match all of K. spectatus‘s strange fangs, each with their own unique beauty. “I thought at this point I was nearly done, and I was very, very wrong,” Evans said.
Although Evans’s original plan was to make a still image of the penis worm, he and Mussini had also toyed with the idea of an animation. But when Evans began to animate the model, his 2,000 carefully constructed teeth bit him in the back. “My laptop just crashed as soon as I did anything. As soon as I opened the file,” Evans said. He didn’t have a PC, so he had to go to a friend’s house to use his gaming computer. Over the course of months, he animated each of the approximately 120 rows of teeth, one by one, revealing how the penis worm inverted its pharynx back into its body. Mussini analogizes the behavior to pushing a fully extended finger of a glove back into the glove. “The finger turns into a deep pit, essentially,” he said.
It took six months for Evans to render the entire animation, showing the penis worm ejecting and retracting its pharynx so that it once again appeared to be a mouth in the sand. The animation is a slow-motion version of how the feeding would have happened in real life, likely in a matter of seconds. Then Mussini had an idea. “Giovanni was like, what if we went inside?” Evans said.
In other words, what would it be like to be swallowed by the penis worm? The resulting animation is downright psychedelic, taking the viewer through a tunnel of increasingly byzantine teeth that is either horrifying or soothing, depending on your vibe. “We thought that was very funny,” Evans said. “Like the only time in human history that has or ever will be made.”
The project was an enormous lift for Evans, who was finishing his senior year. “I’d wake up pretty early, finish my homework, and then I’d work on this every evening until quite late,” he said. He told almost no one about his secret and time-consuming hobby. After the paper was published, however, several of his friends have watched the animation. “I’m glad that it helps people and that people can engage with what is a very cool paper through this,” Evans said. “I’m very happy. It’s nice.”
But as any good paleoartist knows, the animation is a best guess of how a living K. spectatus appeared in real life. It orients the penis worm like a skyscraper to show off the anatomy, but the creature likely hunted laterally, lunging toward scraps in the muck, Mussini said. Perhaps future fossils could help fill in the gaps between reconstruction and reality, but for now, Evans is at peace with the unknown. And what is known about K. spectatus is truly strange. “There’s nothing else like it,” Evans said.