The fauna that keeps on giving

The Burgess Shale of British Columbia, Canada, is famous for its exceptional preservation of bizarre, soft-bodied invertebrate lifeforms, a window into the Middle Cambrian World of 510 million years ago.

Burgess Shale-like faunas are now known from localities world-wide, but recently paleontologists discovered in Morocco a Burgess fauna from rocks 30 million years younger than the Cambrian faunas.

Burgess shale faunas were thought to have gone extinct after the Middle Cambrian. This new discovery suggests that the disappearance of the older fauna was a due to the absence of suitable conditions for fossilization rather than extinction, and it underlines the importance of understanding the conditions and processes leading to fossilization, and it opens the possibility of finding other Burgess faunas.

From P. Van Roy, P. J. Orr, J. P. Botting, L. A. Muir, Jacob Vinther, B. Lefebvre, K. el Hariri, and D. E. G. Briggs. 2010. Ordovician faunas of Burgess Shale type. Nature 465:215-218. A longer summary of their research is here. Photo of Marella, a Burgess arthropod, from the original article.

Burgess Shale redux

The Middle Cambrian Burgess Shale of British Columbia, Canada, is famous for the preservation of bizarre and distinctive animal fossils, like Anomalocaris, Hallucigenia, and Marella (shown at right).

Since its discovery over 100 years ago, other Burgess Shale faunas have been found in strata of similar age around the world, but the fauna appeared to have died out by the end of the Middle Cambrian.

The recent discovery of a Burgess Shale type fauna in Morocco from rocks millions years younger than the Burgess Shale breathes life into a fauna that was thought to be long extinct--including animals like Marella, above, left.

The apparent extinction of the Burgess Shale animals was probably a result of the rarity of the exceptional circumstances required to preserve soft-bodied organisms. The discovery opens the door to finding other, younger Burgess Shale type faunas around the world.

Source and photo credit: Peter Van Roy, et al., 2010, Ordovician faunas of Burgess Shale type. Nature 465:215-218.