Tropical Fossils?
The Burgess Shale fossils are found in the Canadian Rockies at a latitude of 51 North. However, the fossilized animals lived and died in the tropics. This change in latitude over time is the result of the slow action of Plate Tectonics. For the last 508 Million years the North America plate has slowly moved North over time. Consequently, North America has also moved North. You might be wondering how slow are the Plates moving? The speed of the Plates is roughly equivalent to how fast your fingernails grow.
Without question the Burgess Shale is the most famous Cambrian fossil bed because of the exceptional soft-body preservation; but, it is not alone. Due to various reasons, many soft-bodied organisms were preserved during the Cambrian, and in many different localities. Some of these sites are in Greenland, China, Siberia, and Australia. A recent significant find, the Qingjiang biota, was made in 2019 in China. For more information about the Lagerstatte read the article at ScienceMag. In case you are wondering, The Cambrian Period is a geological time interval from 541 – 485 million years ago.
During the Cambrian North America, Greenland, China, Siberia, and Australia were all situated at low latitudes, probably in the tropics. It is possible that all of the Cambrian sites with good soft-body preservation are from tropical latitudes, and are thus, tropical fossils.
In an early post we provided a Paleomap of the Earth in the late Cambrian – from 514 Million years ago. We advise that you look at that map – and read the post – if you are interested in seeing where the continents were at the time.
Cambrian Tropical Ecology
Each new fossil locality has preserved several of its own unique animals, but more importantly, many of the unusual animals of the Burgess Shale are found in the other Cambrian fossil beds – if not the exact same species, than at least a very close relative based on similar looking body shape (or body morphology).
This suggests that the Burgess Shale fossils are not some freak occurrence, but rather represent animals that inhabited widely dispersed regions of Earth’s ancient oceans. They are probably typical of the Cambrian low-latitude fauna – the classic localities in Canada, Greenland, China, Siberia, and Australia all lay in the Cambrian tropics.