Nannarrup

Nannarup is a genus of soil centipedes in the family Mecistocephalidae; this genus includes a single species, Nannarrup hoffmani, also known as Hoffman's dwarf centipede. This centipede was discovered in Central Park in New York City and was the first new species to be discovered in that park in more than a century. This species is the smallest species in the family Mecistocephalidae, reaching only 10.3 mm in length, and has only 41 pairs of legs, the minimum number recorded in this family.

Discovery
This genus and its type species N. hoffmani were first described in 2003 by a team of biologists led by Donatella Foddai. This team based the original description of this species on ten specimens, including an adult female holotype collected in April 1998 from leaf litter in the North Woods of Central Park. These specimens also include nine paratypes (eight juveniles and fragments of another specimen) collected in September 1998 from leaf litter in the Ramble in Central Park. The holotype and eight of the paratypes are deposited in the American Museum of Natural History in New York.

These specimens were collected by a team of researchers led by Liz Johnson and Kefyn Catley of the American Museum of Natural History. This team collected samples of leaf litter from Central Park to conduct research on the health of the park's ecosystem for the Central Park Conservancy, hoping to learn how to best preserve this ecosystem. The team searched through twigs, fungi, and decaying leaves mixed with soil to collect specimens for identification by taxonomists. These researchers sent a collection of their myriapod specimens to the American entomologist Richard L. Hoffman, who was then the curator of invertebrates at the Virginia Museum of Natural History, for identification. Hoffman could not identify some of these specimens and passed them on biologists in Italy who specialize in myriapods.

These biologist recognized the newly discovered centipede as representing not only a new species but also a species so distinctive as to merit placement in a new genus. The genus name Nannarrup derives from the Greek word nannos, meaning dwarf (a reference to the small size of the newly discovered centipede), and Arrup, the name of the genus that most closely resembles this new centipede. The name of the species honors Hoffman, who forwarded the specimens on which the original description of this species is based.

Phylogeny
A cladistic analysis of the family Mecistocephalidae using morphological features places the genus Nannarrup in the subfamily Arrupinae, along with the genera Arrup, Agnostrup, and Partygarrupius. Further cladistic analysis of the subfamily Arrupinae based on external morphology places the genus Nannarrup in a clade with Arrup as a closely related sister group. This analysis also places this clade inside another clade with Agnostrup as a sister group in the same branch of a phylogenetic tree.

Geographic origin
Although the species N. hoffmani was discovered in New York City and is known only from this population, biologists believe that humans introduced this species from elsewhere. The type specimens were discovered along with two other species known to be introduced. Furthermore, New York lies far from the distribution range of any other species in the family Mecistocephiladae. There are only three other species from this family found in North America, all of them in California, and only one of these, Arrup pylorus, is in the subfamily Arrupinae. All other species of Arrup, the closest relatives of Nannarrup, are found in Central Asia, east China, and Japan. These distributions suggest East Asia and California as the leading candidates for the geographic origin of Nannarrup. The most likely scenario is that humans transported Nannurrup in potting soil when they imported exotic plants from East Asia for planting in Central Park.

After introduction to New York City, Nannarrup established a breeding population in Central Park, as indicated by specimens that not only include juveniles as well as adults but also were collected in different seasons. Furthermore, the female holotype contained sperm, indicating that the species is reproducing in Central Park. The survival of this introduced species in such a foreign urban environment is especially striking given the population density of New York City and the flow of visitors to Central Park.

Description
The female holotype measures 10.3 mm in length, and all specimens have 41 leg pairs. The body (when preserved in alcohol) is a very pale yellow, but the head and forcipular segment is a pale ochre. This species shares some distinctive features with its close relatives in the genus Arrup. For example, in these species, the setae on the clypeus are arranged in two groups, one on each side of the clypeus. Furthermore, all species in the genus Arrup also have 41 pairs of legs. Other features, however, distinguish Nannarrup from Arrup. For example, the coxosternite of the first maxillae (the sclerite corresponding to the sternite and most basal segment of the first maxillae) is divided in Nannarrup but undivided in Arrup.