Researchers studying 450-million-year-old fossils discovered about 50 kilometres northeast of Quebec City have identified a new species of basal medusozoan: Paleocanna tentaculum, a soft-bodied, tube-shaped polyp with a ring of tentacles. Closely related to modern jellyfish, it is a rare discovery. Only a few other species in its subphylum have ever been described in the fossil record.
"Soft-bodied organisms do not preserve as well as hard-bodied organisms, usually making any soft-bodied fossil more valuable to understanding the history of life," said Louis-Philippe Bateman, study co-author and a graduate student in the Department of Biology at McGill University.
The discovery also highlights Quebec's significant fossil record, Bateman said.
"I've often caught myself saying that we have a less glamorous fossil record than places like British Columbia or Alberta," he explained. "Discoveries like this one show that many things have yet to be discovered and described here."
A species-rich locale
The fossils were found in Saint-Joachim, in the Upper Neuville Formation of the Saint Lawrence Lowlands. The area is "among the most species-rich fossil localities on the planet" for fossils from the Ordovician period, said Christopher Cameron, study co-author and Professor of Biology at Université de Montréal.
Fifteen slabs of shaly limestone containing around 135 specimens were examined, 39 of which were measured and photographed. To make the identification, the researchers compared the physical features of the fossils with 69 other fossil and living jellyfish-related species.
Their analysis showed that Paleocanna tentaculum is more closely related to today's jellyfish than to other ancient relatives.
Exceptionally preserved specimens
The researchers said the fossils were probably preserved during a sudden burial event on the seafloor, when fine mud quickly covered the animals and protected their remains from scavengers and disturbance.
"Because several individuals are aligned in the same direction, we think they were buried in place or were not transported far before being buried," said Greta Ramirez-Guerrero, lead author and PhD candidate at Université de Montréal. "This rapid burial, combined with low-oxygen conditions in the surrounding environment, slowed decay and helped preserve the animals before the sediment turned to rock."
The fossil specimens are curated at the Musée de paléontologie et de l'évolution (MPE) in Montreal, where they will be the subject of further research.
Image by Greta Ramirez-Guerrero
"We must pay tribute to John Iellamo, a reputed amateur fossil collector and member of our museum, who found these fossils in 2010 and subsequently donated them to the MPE," said Mario Cournoyer, study co-author and MPE founder. "He was able to recognize the scientific importance of these fossils and made them available for research. Without him, we would not be talking about this new species."
Bateman added that the Saint-Joachim site could yield further discoveries.
"Once you find them, these kinds of sites tend to keep producing spectacular new material and species for many years, so I'm expecting many more new interesting discoveries to come," he said.
About this study
"Thecate stem medusozoan polyp from the Upper Ordovician of Québec," by Greta Ramirez-Guerrero, Huda Alghaled, Louis-Philippe Bateman, Mario Cournoyer and Christopher B. Cameron, was published in the Journal of Paleontology.
The study was funded by the Natural Sciences and Engineering Research Council of Canada and the Fonds de Recherche du Québec.
