The Burgess Shale is one of the most famous fossil localities in the world. Located in Yoho National Park in the Rocky Mountains of British Columbia, this geologic formation dates back to the Cambrian, approximately 505 million years ago. The Burgess Shale was made famous by its exceptional preservation of soft body parts, which are not always well preserved. The Cambrian is the first geologic period that has significant numbers of clear animal fossils in it, and is often referred to as the Cambrian Explosion. Because of this, the Burgess Shale is particularly important in terms of early evolution of many animal groups.
The Burgess Shale was first discovered in 1909, and has been well studied ever since. It is included in the Canadian Rocky Mountain Parks UNESCO World Heritage site, named in 1984. Because of the significance of this fossil site, it is very difficult to collect from or visit this location, with visitors only allowed on guided tours. It was deposited in an ocean setting, so all fossils are marine. There have been some well known fossils discovered here, like Marella (an early arthropod), Anomalocaris (an early arthropod relative), Hallucigenia (a bizarre spiny creature) and Pikaia (a possible early chordate, a group that includes vertebrates).
|Example of sizes of different organisms in the Burgess Shale. Image by Matt Martyniuk|
There are several excellent fossil sites in Alberta which we have discussed previously on this blog. For more information on those, check out our Palaeontology in Alberta post!
The Gunflint Chert in Ontario (and also in Minnesota) is an iron formation that was deposited about 1.9 BILLION years ago. In these rocks are tiny microfossils from stromatolites. These rocks were first studied in the 1950s and 60s and small spheres, rods, and filaments were determined to be single-celled organisms. This find kicked off the search for Precambrian microfossils.
The Joggins Fossil Cliffs of Nova Scotia are a famous Carboniferous fossil site from about 310 million years ago. The Carboniferous is often referred to as the 'Coal Age' due to the large number of fossilised trees that have been turned into coal. In particular, Joggins has a large number of complete and even upright trees that have been preserved, especially from the lycopodiphyte Sigillaria. In 1852, a great discovery was made when geologists found tetrapod fossils within an upright tree stem. The internal part of the tree had been eroded away, while the external bark was still in place, leaving a large hole for small animal bones to fall into and become fossilised. Further investigation revealed the earliest sauropsid (the group of amniotes that include reptiles, birds, dinosaurs and more) fossil ever found, Hylonomus. Other important fossils from Joggins Fossil Cliffs include Protoclepsydrops, an early synapsid that is older than Hylonomus, and small tetrapod trackways.
|Artists impression of Hylonomus by Nobumichi Tamura|
Mistaken Point is found on a peninsula on the island of Newfoundland, and contains more Precambrian fossils, including some of the most diverse and well-preserved fossils from this time. It contains what is most likely the oldest multi-cellular fossils from North America, the oldest deep water fossils and the oldest Ediacaran fossils in the world. They date back 575-560 million years.
Although there aren't any truly fossiliferous sites in Nunavut, at least not like the ones we have mentioned previously, it is home to one of the most famous and important fossils ever discovered. In 2004, a group of palaeontologists discovered a partial skull sticking out of a cliff on Ellesmere Island. When they analysed it, they discovered it was an early tetrapod. This fossil, called Tiktaalik from the Devonian (375 million years ago), is an example of what we call a transition fossil. It shows the transition that palaeontologists refer to as "from fish to limbs". It's also what palaeontologists sometimes call a 'fish-er-pod', as in it has a combination of fish (e.g. gills and fins) and tetrapod (e.g. mobile neck and lungs) characteristics, as well as transitional features (e.g. half-fish, half-tetrapod limb bones and joints). Although there is only one of these fossils known, it has been extremely important in understanding the evolution of early tetrapods.
|Artist's impression of Tiktaalik by Nobumichi Tamura|