The first great ex-stink-tion took place during the Cambrian Era. Fossil evidence shows that all life forms in the 'sea' got flattened (note the condition of the fossils) by an as yet unknown, at the time, outside agency. Now...this ex-stink-tion event (the first of its kind?) is thought to have occurred when an undersea well of noxious gas (tentatively identified as a primordial starkerbark) imploded when it reached the surface of a very young and volatile planet Earth. This implosion sent shock waves reverberating throughout the thin crust of the planet re-arranging the landmasses and giving rise to what is now known as plate tectonics.
The force of said implosion forced great masses of land down to the ocean bottom with a great thud! All life forms in the wake of this subsistence were pounded flatter than the proverbial pancake. When they rebounded to form the land of OZ as well as other inconsequential places new life forms developed to take advantage of all that road-kill. Yum! Eventually this newly available foodsource gave rise to bigger more advanced life forms (i.e. dinos) that happilly gobbled them all up. Would that certain CEO's were there at the time to get theirs?
At any rate...the fossil record (stone tablets as vinyl was not yet available (too many dinos still alive)) indicate that a species of Flatulensis Barkerhinosaurisiis evolved to ingest the left over methane producing Cattalosaurous OZ-Maundious thus giving rise to an atmosphere richer in oxygen (just a little bit) but just enough so that it attracted the attention of a denizen of the far (very far) Flatulous Cloud beyond the orbit of the now known tenth planet (dwarf size) Ceres. On approach to the primordial planet Earth this denizen, tentatively? indentified as Barkernemisis, turned its rearend to face the planet and cut loose with the second most powerful starkerbark in all of creation and wiped out the dinos. The sternch was so bad that it plunged the planet into another ice-age that is only now beginning to warm up...sixty five million years later!?!?!
Was starkers there at the time? Did starkers plan the whole thing? Did starkers save up for untold eons just for the express purpose of creating a world (OZ) of his liking? And what of future generations? Will our descendants evolve with built-in gas masks? Will planet Earth shrivel up like an overripe prune? All wrinkly and stuff? I wonder...