In Botany, a type specimen – a typus – is the specimen to which a name is permanently attached. This permanent link between the specimen and the name makes able to perform accurate taxonomic revisions because it is always possible to consult the original vegetal material. Exceptionally, instead of a plant fragment, an illustration can be used.
Types are the most valuable materials in herbaria. They can be of various kinds, depending on the way in which they are cited in the taxonomic works associated with them (protologues and subsequent revisions) and on the circumstances in which they were collected and stored. The most common classes are:
- A holotype is the one specimen or illustration either (a) indicated by the author(s) as the nomenclatural type or (b) used by the author(s) when no type was indicated. As long as it exists, it fixes the application of the name concerned.
- An isotype is any duplicate of the holotype and is always a specimen. If the holotype is an illustration there cannot be any isotypes.
- A syntype is any specimen cited in the protologue when there is no holotype, or any one of two or more specimens simultaneously designated in the protologue as types. Illustrations, even if cited, cannot be syntypes.
- A paratype is any specimen cited in the protologue that is neither the holotype nor an isotype, nor one of the syntypes if in the protologue two or more specimens were simultaneously designated as types.
- A lectotype is a specimen or illustration designated subsequent to publication of the protologue (usually by a subsequent worker) if the name was published without a holotype, or if the holotype is lost or destroyed, or if a type is found to belong to more than one taxon. A lectoptype must be designated from among the original material.
- A neotype is a specimen or illustration selected to serve as nomenclatural type if no original material exists, or as long as it is missing.
More details can be consulted on the website of International Association for Plant Taxonomy (IAPT), specially in the part dedicated to explaining the International Code of Nomenclature for Algae, Fungi and Plants.
In 2021 we published an article about EMMA Herbarium with an annex in which we recorded the possible types that it houses. As we investigate each one of them, we will publish posts explaining what we discover.
