Radiometric dates constrain the Wenlockian between 432.9 and 426.7 million years ago.
[6] The name was first used in the term "Wenlock and Dudley rocks" by Roderick Murchison in 1834 to refer to the limestones and underlying shales that underlay what he termed the "Ludlow rocks".
[7] He later modified this term to simply the "Wenlock rocks" in his book, The Silurian System in 1839.
[8] The Wenlock's beginning is defined by the lower boundary (or GSSP) of the Sheinwoodian.
[9] The Wenlock is divided into the older Sheinwoodian and the younger Homerian stage.