|Cosmati floor, Westminster Abbey church, during a recent cleaning.|
It wasn't known as "Cosmatesque" at the time; that is what we call it now, because the style was made popular by the Cosmati family of Rome. The Cosmati (members of whom were active for generations, from at least 1190 until at least 1303) used opus sectile [Latin: "cut work"] in stone to design intricate inlays. We know some dates for members of the family because they occasionally signed their work.
|Cosmati floor from Rome.|
A TV program made about the Cosmati floor during and after its recent restoration can be found on YouTube.