​Type specimens in the Arthur Fungarium

What is a type specimen? 

A Type specimen is a specimen, or set of specimens, on which a botanist or mycologist based their description of a new species.

According to a precise set of rules laid down by the International Code of Nomenclature for algae, fungi and plants (ICN), the scientific name of every taxon is almost always based on one particular specimen, or in some cases specimens. They are usually physical specimens that must be accessioned in a museum or herbarium research collection, but may also include drawings, photographs or slides of the physical specimen. 

Types are of great significance. When identifying material, a researcher attempts to apply a taxon name to a specimen or group of specimens and this will be based on their understanding of the relevant taxa, using (at least) the type description, but preferably based on an examination of all the type material of all of the relevant taxa. If the taxon appears not to have been named, then the scientist or another qualified expert designates a type specimen and publishes a new name and an official description

This process is crucial to the science of biological taxonomy and biology as a whole and these type collections are considered the lynchpin of biological research.

There are actually several kinds of types. Here are the definitions of some common type statuses:

  • Holotype: When a single specimen is clearly designated in the original description, this specimen is known as the holotype of that species.​
  • Isotype: Any duplicate specimen of the holotype. The prefix Iso is also used with other type definitions. 
  • Lectotype: Designated as the type when no holotype was identified by the original author, or when the holotype is lost or destroyed. It is chosen from among the specimens available to the original publishing author.
  • Syntype: Any of two or more specimens listed in the original description of a taxon when a holotype was not designated.
  • Paratype: A specimen not formally designated as a type but cited along with the type collection in the original description of a taxon.
  • Neotype: A specimen chosen by a later researcher to serve in place of a holotype when all specimens available to the original publishing author of a scientific name have been lost or destroyed.
  • Topotype: A specimen of a plant collected from the same locality as the holotype and usually on a different date. A topotype has no formal standing.
  • Cotype: A term formerly used for syntype and sometimes (erroneously) for isotype and paratype. This is an old term that was used loosely and is not used by today's taxonomists.​
The Arthur Fungarium has an estimated 4,000 type specimens, with over 3,500 currently verified and almost 1,500 imaged under JSTOR's Global Plants Initiative. The Type collection in the Arthur covers all 14 rust families and 144 genera (of an estimated 168) with roughly 3,500 species represented. Below are summaries of our type specimens for country of origin, collection periods, Genera and type states (Click graph for larger image)​​. 


To s​ee images of the The Arthur Fungarium's type collection, via JSTOR's Global Plants Intiative, click here (institutional access required).

As mentioned above, an Isotype is a duplicate specimen of the holotype. We have many Isotypes in the Arthur as Cummins, when writing his various rust fungi guides, consulted hundreds of type specimens and was supplied with samples from many of them. Some of these isotypes are mere fragments, millimeters in size, of the original collection but they still hold valuable information. 

Designating a specimen as a holotype, when it is not explicitly stated on the packet, is something that we do with reservation. Occasionally, the actual PUR accession code is cited in the species publication or the packet is clearly marked as being from the collectors herbarium. However, it is more often the case that only the collection information is given in the publication and so the actual status of the specimen is unknown, only that it is some form of type for that species. 

In these instances, the status "type" is given, meaning we can confirm that this is indeed type material but we are unsure whether it is a holotype, isotype or some other form of type. If we only have partial collection information we have used the term "type?" (as suggested by the Global Plants Initiative) indicating that a specimen appears to be type material but we are unsure. 

Puccinia species account for more than half of the known species of the rust fungi, and more than half of the specimens in the Arthur are Puccinia species, our type collection is therefore mainly comprised of Puccinia species. 

The anamorphic (asexual) genera, Uredo and Aecidium account for a large portion of types. Many of these species are yet to placed in their teleomorphic (sexual) genus are represent very important and informative samples of these species should future nomenclatural and taxonomic work be undertaken on these species. ​


The majority of type collection, just over 80%, was collected between 1927 and 1940. This is obviously not surprising as taxonomy became more popular specimen collection and species discovery was more prevalent. This has slowed in recent decades as has the rate of species discovery. 

Additionally, The Herbaria at Purdue have been without a director or uredinologist since the mid 90s. With the appointment of our new director Dr. M. Catherine Aime, we have already seen the acquisition of additional rust collections, from both herself and other institutions. This is surely to continue expanding our type collection and adding more recent species. 

Just as a large portion (>50%) of the overall collection of the Arthur has origins in the USA, a large portion of our type collection is from species collected in the USA. We have over 400 types for which Dr. Joseph. C. Arthur was the author, or co-author, of the species name, over 400 with Dr.George B. Cummins as author and over 200 with Dr. Joe F. Hennen as author.

Brazil and Mexico are also heavily represented. This is because the director of the Arthur during the 80's to 90's (Dr. Joe F. Hennen) specialized in Central and South American Puccinales. With the 2013 return of an un​cataloged loan from Dr. Hennen, of some 20,000 specimens, we are sure to find additional type specimens from this area, as well as additional types in general. We estimate that the Hennen loan may contain 500 - 800 type specimen.