The first recorded monograptid genus, from the Early Llandoverian (Lower Silurian). Successive evolutionary trends within the graptolites resulted in the development of the single-branched monograptids. These had only a limited number of thecal cups (see theca) on one side of the branch although the cups were large and exhibited considerable morphological variation. Compare dendroidea; and graptoloidea.
Subjects: Earth Sciences and Geography.