Abstract

The retiolite graptolites can be divided into at least two major groups, each derived independently from diplograptid ancestors. The lacinia of some Ordovician forms, and the ancora and ancora sleeve (‘reticulum’) of Silurian retiolites, are both novel structures. Some other retiolite taxa lacking these structures are best grouped within diplograptid families. The nomenclature of retiolite structures is discussed.

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