Its late stages saw the Lau event and the closing of the Iapetus Ocean, which produced the Caledonian Orogeny.  
Its top is set by the first golden spike, placed in a cliff at Klonk in the Czech Republic.  Its late stages saw the Lau event and the closing of the Iapetus Ocean, which produced the Caledonian Orogeny.  Its divisions are primarily marked by the appearance of graptolite species, and the first coral reefs, freshwater fish and jawed fish appeared during it.  A feud over strata classification between Adam Sedgwick and its discoverer, Roderick Murchison, led to insertion of a new period between this one and Sedgwick's Cambrian system.  For 10 points, name this third period of the Paleozoic, which precedes the Devonian and succeeds the Ordovician.
Its top is set by the first golden spike, placed in a cliff at Klonk in the Czech Republic.  
{Silurian} period