FTP name this period lasting from 505 to 438 million years ago, which followed the Cambrian and preceded the Silurian.
The name of this geologic time period comes from the name of an ancient Celtic tribe which inhabited the Arenig mountains, where Charles Lapworth found many fossils from the time. During this time Laurentia and Baltica moved together and the Iapetus Sea dried up, and it was dominated by such life forms as Graptolites , Ostracoderms,  tabulate corals, and  Nautiloids , while some land plants began to make their appearance. FTP name this period lasting from 505 to 438 million years ago, which followed the Cambrian and preceded the Silurian.
The name of this geologic time period comes from the name of an ancient Celtic tribe which inhabited the Arenig mountains, where Charles Lapworth found many fossils from the time.
Ordovician