The problem of lost or destroyed or unrecognisable types is unfortunately a common one. A neotype designation is not always needed however because the identity of the species can often be recognised from:
- the original description;
- generally accepted interpretations that can be followed;
- examination of topotypic material, i.e. that collected at the type locality;
- or the problem can be set aside until more information becomes available which allows it to be resolved, e.g. if the original type is rediscovered.
The taxonomy of some animal groups which are soft bodied and hard to preserve can work reasonably well on this basis although many types are missing.
Sometimes however, the above approaches can be unsatisfactory and a neotype is needed. A neotype can be designated when no name bearing type (holotype, lectotype, syntype or previous neotype) for a species name is believed to be extant, i.e. it has been lost or destroyed, and where it is considered a name bearing type is needed to define the species (Article 75). Certain information must be published for the designation to be valid (Article 75.3):
- that there is an exceptional need;
- the taxon must be differentiated;
- details allowing recognition of the specimen;
- the reasons why it is thought the name bearing types are destroyed;
- evidence that the neotype is consistent with what is known of the former name bearing types;
- evidence that the neotype came from as close as practicable to the original type locality;
- and a statement that the neotype is or has become the property of an institution which can preserve it and make it available for study.
If the original name-bearing type is found then the neotype is set aside, unless this will cause instability, in which case the Commission can be asked to rule that the neotype is kept (Article 75.8).
Where an extant name-bearing type is unidentifiable, e.g. if very damaged, or a sex or life stage without diagnostic characters, then the Commission can be asked to set aside the extant name bearing type and a neotype can be designated (Article 75.5).