The replies to the question about holotypes show that there is a lot of
misunderstanding of the subject. Part of the problem is that the concept of
type specimens has evolved a lot over the years. The concept of a holotype
was invented about 100 years ago, and didn't come into wide use until less
than 50 years ago.
Nowadays, the description of a new species is generally based on all the
specimens available to an author, not just the holotype, in order to show
the range of variation. In the 19th century, authors often wrote as if they
were describing a single ideal specimen, even if they had many specimens
available, and they often did not designate a particular specimen to
represent the species.
The specimens originally used to describe the species are part of the type
series. If only a single specimen was known, it is automatically the
holotype. If the author, in the original publication, designated a single
specimen to represent the species, it is the holotype, and the other
specimens are paratypes. If the author does not designate such a specimen,
then the specimens studied are all syntypes. A later author can designate
one of the syntypes as a lectotype to represent the species. The remaining
syntypes become paralectotypes. Generally a specimen that was illustrated in
the original publication is preferred as the lectotype.
The paratypes and paralectotypes do not have to be from the type locality.
In a case where syntypes come from several localities, the type locality is
automatically restricted to the locality of the lectotype when a lectotype
is designated.
A specimen identified by the author after the date of publication of the
species is not part of the type series. This can be a problem because in old
collections it is often not possible to tell if a specimen was collected or
identified before the description was published.
If all of the type material of a species has been lost, and it is not
possible to tell from the original description and illustrations what
species was meant, a neotype can be designated to represent the species. The
type locality automatically becomes the locality of the neotype.
Why designate a single specimen to represent a species, when most species
are variable? To provide a standard of reference. Sometimes it turns out
that the type material contained more than one species, so the identity of
the holotype or lectotype settles the questions of which species the name
applies to.
Gary
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Gary Rosenberg, Ph.D. [log in to unmask]
Malacology & Invertebrate Paleontology gopher://erato.acnatsci.org
Academy of Natural Sciences http://www.acnatsci.org
1900 Benjamin Franklin Parkway Phone 215-299-1033
Philadelphia, PA 19103-1195 USA Fax 215-299-1170
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