Chance determined evolutionary descent from pikaia rather than hallucigenia during this period based on the "experimental" interpretation put forward by Stephen Jay Gould to explain the soft fossil lagerstätte in the Burgess Shale, although more recent interpretations of that find classify its fossils as ancestors of living phyla.
Helicoplacoids disappeared during this period, and the organisms that evolved during it completely replaced the iconic quilted Dickinsonia of the Ediacaran biota. The shift from entirely horizontally-oriented burrows to vertical burrows alongside a decline in the global prevalence of stromatolites during this period signify its "substrate revolution," which is thought to be related to the breakup of Pannotia and the immersed cratons it left behind. The Taconic Orogeny (*) began toward the end of this period. Chance determined evolutionary descent from pikaia rather than hallucigenia during this period based on the "experimental" interpretation put forward by Stephen Jay Gould to explain the soft fossil lagerstätte in the Burgess Shale, although more recent interpretations of that find classify its fossils as ancestors of living phyla. For 10 points, name this first period of the Paleozoic era which saw a namesake "explosion."
Helicoplacoids disappeared during this period, and the organisms that evolved during it completely replaced the iconic quilted Dickinsonia of the Ediacaran biota.
Cambrian period