How to … Understand the types of types
A type specimen is the specimen to which a name is permanently attached. Choosing a good type specimen is important to ensure that future workers can properly understand and assess named taxa.
Types come in several flavours. When you name a new species, you really only need to understand holotypes, isotypes, and perhaps paratypes. However, to understand the full complexity of historical typification there are more types of types to understand.
A holotype (Art. 9.1) 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 (Art. 9.5) is any duplicate of the holotype and is always a specimen. If the holotype is an illustration there cannot be any isotypes.
A syntype (Art. 9.6) 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. An isosyntype (Art. 9.4 footnote) is a duplicate of a syntype.
A paratype (Art. 9.7) 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. Note that there is no such term “isoparatype” for a duplicate of a paratype.
A lectotype (Art. 9.3) 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 lectotype is in effect equivalent to a holotype. A lectoptype must be designated from among the original material (see Art. 9.4 and 9.12). An isolectotype (Art. 9.4 footnote) is a duplicate of a lectotype.
A neotype (Art. 9.8) is a specimen or illustration selected to serve as nomenclatural type if no original material exists, or as long as it is missing. An isoneotype (Art. 9.4 footnote) is a duplicate of a neotype.
An epitype (Art. 9.9) is a specimen or illustration selected to serve as an interpretative type when the holotype, lectotype, or previously designated neotype, or all original material associated with a validly published name, is demonstrably ambiguous and cannot be critically identified for purposes of the precise application of the name to a taxon. An isosepitype (Art. 9.4 footnote) is a duplicate of an epitype.
For more information, see Chapter 7 How to designate a type in The Code Decoded.
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