- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
The earliest monograptids are shown to appear at exactly the same time (base of the vesiculosus zone in Scotland) as Dimorphograptus and Rhaphidograptus, and the earliest species of these two genera are those with long uniserial portions, the forms with shorter uniserial portions appearing in the overlying cyphus zone. Akidograptus is entirely restricted to the pre-monograptid beds. One of the earliest monograptids is described as Monograptus cyphus var. praematurus var. nov., which has a distinct and earlier range than M. cyphus s.s. Lapworth.