New Species of the Mysterious Stenothecoids Found in Canada’s Burgess Shale

Ancient fossils dating back more than a half a billion years were discovered in Canada’s Burgess Shale. They were analyzed by a scientist who came up with a fascinating way to study the fossils in even further detail which provided more valuable information regarding the evolution of life on our planet.

Dr. Paul Johnston, who is an associate professor in Earth and Environmental Sciences at Calgary's Mount Royal University, stated that marine invertebrates known as stenothecoids were discovered on Mount Stephen in British Columbia’s Yoho National Park. He then came up with an incredible manner to extract the 505-million-year-old fossils from the rock by using acid to dissolve the limestone that they were embedded in.

In an interview with CTV News, Johnston described the process in further detail, “Most of the Burgess Shale is shale, but there are some layers of limestone and I could see that the shells had been replaced by silica and that gave me the idea to put the limestone in acid because I know that the silica shells are resistant to acid,” adding, “I could get them out as three-dimensional shells from this 505-million-year-old limestone.”

Once they were extracted, it was determined that they were in fact an entirely new species of stenothecoids as Johnston explained, “The shell is kind of asymmetrical – it kind of has a 'sway' to it.” “It's absolutely unique in the animal kingdom, so paleontologists were at a loss to figure out where on the evolutionary tree of life these creatures belong.” “Paleontologists thought they might be related to the phylum Brachiopoda, which are fairly rare in modern seas unless you live in New Zealand or Antarctica where they are still fairly common.”

He went on to say that the features of the newly extracted fossils were quite different than other brachiopods and that they revealed interesting information regarding their evolution during the Cambrian Period. He ended up working with Dr. Michael Streng from Sweden's Uppsala University and they came up with the theory that stenothecoids were an early form of Cambrian creatures that eventually evolved into modern brachiopods.

“Different evolutionary groups, like the brachiopoda, show a similar pattern where you get this big variety early in their evolution, a bunch of those go extinct and we end with a few basic lineages that survive,” Johnston noted.

As for now, the fossils will remain at the Royal Tyrrell Museum in Drumheller, Alberta, as well as the Royal Ontario Museum in Toronto. A picture of the fossils and a news report about the discovery can be viewed here.

Their study was published in the journal Acta Palaeontologica Polonica where it can be read in full.