Close-up of the fossil found at the World Exchange Plaza.
A 450-million-year-old fossil that sheds new light on the early evolution of worm-like animals was found in the last place one might expect – downtown Ottawa.
Called Plumulites canadensis, the fossil was discovered in a pile of rock that was dug up during construction of the World Exchange Plaza during the 1990s and then dumped at the city limits.
“Most fossils in the Ottawa area are found from rock piles dumped by construction companies,” says Jonas Weselake-George, president of the Ottawa Paleontological Society. “The entire area we live in is covered in a layer of clay from the end of the last ice age when Ottawa was under the sea.”
Scientists say the fossil is one of just eight specimens of the extinct species and – since most discoveries are made in remote locations – is notable for having an address: Albert Street, Ottawa, Canada, K1P 1A4.
In 1998, the fossil made its way to the Royal Ontario Museum in Toronto and into the hands of David Rudkin, an assistant curator of paleobiology at the museum.
According to Rudkin, the fossil was originally found by Ottawa resident Nathan Isotalo, who later exchanged it with James Sherwood, a fellow collector.
Rudkin says it was Sherwood who brought the fossil to his attention.
Once at the ROM, the fossil was determined to be a form of Plumulitid machaeridian, a primitive species that lived on the seabed. Rudkin says it was a “more or less complete machaeridian” – and a particularly good find as similar fossils are “almost never intact like this one.”
Though the Plumulitid machaeridian – like many other fossils – was found during construction work, Weselake-George says that construction poses a danger to the preservation of fossils.
“Millions of fossils are destroyed by construction work in Ottawa each year. Most of the fossils are fairly common, but undoubtedly some finds that could be of scientific significance get destroyed,” says Weselake-George.
The Plumulitid machaeridian had broad, flattened scales and it carried a set of mineralized plates on its back.
The armoured plating would have given this early fossil protection on its exposed upper surfaces.
In the 1990s, says Rudkin, it wasn’t clear how to classify the Centretown fossil.
“At that time, the biological affinities of machaeridians were unclear – they were an enigmatic group of extinct organisms without any clearly defined connection to other known animals,” says Rudkin.
But then a new, “exquisitely” preserved Plumulitid machaeridian fossil was found in Morocco. In a paper released in 2008, Yale University professor Jakob Vinther and his colleagues established that the machaeridians were a part of the annelid worm clan. Earthworms, bristleworms and leeches are modern-day members of the annelid worm group.
The discovery of this fossil gives scientists additional insight into how this major group of organisms evolved.
Rudkin collaborated with Vinther to study the fossil in the new context of annelid relationships, bringing Ottawa’s Plumulites canadensis to Yale for examination. The results of their collaboration have since been published.
Though currently still on loan to Yale, Rudkin says that the Plumulites canadensis is now catalogued in the permanent ROM Invertabrate Palaeontology Collection and will remain at the museum.
Rudkin says he has hopes for similar finds in Ottawa in the future.