This Ice Cream Cone Shaped Creature Finally Has a Home on the Tree of Life

Soft tissues. Image: Royal Ontario Museum

A 20-year-old University of Toronto undergraduate student didn’t expect to get the chance to solve a paleontological mystery this early in his career, yet his name is on a new paper describing where an ancient cone-shaped, not-quite-but-sorta-mollusc-like creature fits into the phylogenetic tree of life—the classification system that connects every plant and animal that has existed on Earth.

If you live in an area that was once underwater, it’s not hard to find the fossils of hyoliths. These long-extinct invertebrates sported a distinct conical shell, giving them the appearance of an inverted ice cream cone. They were some of the first creatures known to form mineralized external skeletons, too.

Joseph Moysiuk showing matching halves a fossil slab while in Kootenay National Park on a Royal Ontario Museum field expedition in 2014. Image: Joseph Moysiuk

They were very common during the Cambrian period, about 540 million years ago, when they first appear on the fossil record. Long thought to be related to squids and snails, it was hard for paleontologists to figure out where these small sea-creatures fit on the tree of life, exactly, because there’s nothing like hyoliths alive today. That correct classification is what paleontology student Joe Moysiuk has published in Nature, along with his co-authors.

“Hyoliths went extinct millions of years before the first dinosaurs appeared. It can be tough to get one’s head around the age of these fossils,” Moysiuk told Motherboard over email.

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The break came when they analysed a specimen from the Burgess Shale in the Rocky Mountains of British Columbia. The fieldwork team, led by study co-author Jean-Bernard Caron, senior curator of invertebrate palaeontology at the Royal Ontario Museum, was able to investigate fossils with soft-tissue still visible. After looking at over 1500 samples, the answer came from the way that the creatures fed themselves. The hyolith “feeding structure,” Moysiuk explained, displays a “row of flexible tentacles extending away from the mouth,” which it probably used to sweep food into its mouth.

This illustration shows the hyolith Haplophrentis extending the tentacles of its feeding organ (lophophore) from between its shells. The paired spines, or ‘helens’, are rotated downwards to prop the animal up off the ocean floor. Image: Danielle Dufault

Those features identified hyoliths as a kind of brachiopod, or shellfish with symmetrical shells. Brachiopods have valves above and below their shells to open and close for feeding or protection. This makes them similar to, but still distinct from, molluscs. Molluscs have valves on the left and right of their bodies.

“Only one group of living animals has a comparable feeding structure (called a lophophore) enclosed by a pair of shells,” said Moysiuk.

The program that catapulted Moysiuk into his own research paper is known as the Research Opportunity Program at the University of Toronto. Started in 2000, it was a way for second-year undergraduate students to make connections with the research community at the school. It lets students get a feel for what it’s like to work with faculty members and get their hands dirty in research projects.

“While not all of them get the opportunity to publish in a prestigious journal like Nature, many students in the program say the experience is transformative for them,” said Pamela Klassen, vice-dean of undergraduate education in the Faculty of Arts & Science.

With our newfound understanding of where these invertebrates sit phylogenetically, we can put to rest a mystery that has stumped researchers, and connect hyoliths to some of the most plentiful creatures that inhabited ancient oceans. Though brachiopods are way less abundant today, they were key filter-feeders and reef builders in the Paleozoic Era.

“Our findings allow us to finally place a sizeable branch in the tree of life and add to our understanding of the earliest evolution of brachiopods, which went on to become a diverse group of animals,” said Moysiuk.

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