 The Rhuddanian age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma (million years ago).It succeeds the Himantian Age (the last age of the Ordovician Period) and precedes the Aeronian age.The GSSP for the Silurian is located in a section at Dob's Linn, Scotland, in an artificial excavation created just north of the Linn Branch Stream.