The Burgess Shale A Window on the Cambrian Explosion

Konservat Lägerstatte Konservat – preservation Lägerstatte – “treasure house” Konservat Lägerstatte – a location or stratigraphic unit with unique and remarkable preservation of fossils Fossils may be uncommonly abundant or rare Fossils are typically articulated Soft tissues may also be preserved

Burgess Shale Middle Cambrian Shale – deep, dysoxic Yoho National Park Canadian Rocky Mountains The world’s most important Lägerstatte?

The Cambrian Explosion Widespread appearance of abundant fossils Evolution – Explosive Adaptive Radiation A Cambrian “arms race”? or Creation of Habitat – Passive Margins of Rifted Rodinia OR… Taphonomic Event - Made possible by development of shells Diverse taxa develop ability to make shells at once Chemical threshold in oceans? Atmosphere? OR… ALL OF THE ABOVE????

The Burgess Lägerstatte Excellent preservation Preservation favored by Fine grained sediment Anoxic to dysoxic environment Obrution Events – rapid burial of live organisms Unique Organisms – some have no modern descendents Ancestors of many extant taxa “Wonderful Life” – variations and contingency

Anomalocaris

Marella (“lace crab”) and Wiwaxia (an armored “tribble”?)

Opabinia, Yohoia, Sidneyia

Halucigenia First Reconstruction Recent Reconstruction

Canadia (a worm) and Pikaia (first notochord) Canadia Pikaia

Chenjiang Biota – Maotianshan Shale Early Cambrian of China Preservation of soft- bodied biota Similar to Burgess Shale But 15 MY older!