Ordovician Graptolite
Didymograptus denticulatus
Ordovician
Fillmore Formation
Pyramid Ridge Quarry
Milalrd County
Utah
USA
 
Graptolites are colonial animals widely recognized as hemichordates. These fossils are from the Middle Cambrian through the Lower Carboniferous (Mississippian).The name graptolite comes from the Greek graptos meaning "written", and lithos meaning "rock", as many graptolite fossils resemble hieroglyphs written on the rock.