Polydesmida is the largest order of millipedes, containing approximately 3,500 species, including all the millipedes reported to produce hydrogen cyanide (HCN). Polydesmids grow and develop through a series of moults, adding segments until they reach a fixed number in the adult stage, which is usually the same for a given sex in a given species, at which point the moulting and the addition of segments and legs stop. This mode of development, known as teloanamorphosis, distinguishes this order from most other orders of millipedes, which usually continue to moult as adults, developing through either euanamorphosis or hemianamorphosis.
Xystodesmidae is a family of millipedes. Its members often have very small distributional areas, with many species only known from a single locality. They are found across the northern hemisphere, with peak diversity in the Appalachian Mountains, where one-third of the 300 or so species occur. They are particularly abundant in deciduous broadleaf forests in the Mediterranean Basin, Africa, Asia, Central and North America, and Russia. Information on basic taxonomy is scant for this family; for example, it is estimated that the genus Nannaria contains over 200 species, but only 25 were described as of 2006. By 2022, 78 species in Nannaria have been described.
Pseudopolydesmus is a genus of flat-backed millipedes in the family Polydesmidae.
Pleuroloma flavipes, commonly known as the wandering cherry millipede, is a species of flat-backed millipede in the family Xystodesmidae. It has the widest distribution of any species of xystodesmid millipede and is found in eastern North America from southeastern North Dakota, eastward to Connecticut, and southward to North Carolina, northern Louisiana, and southern Texas. Pleuroloma flavipes millipedes are occasionally observed in large aggregations of individuals where they appear to move en masse in a certain direction, hence the common name "wandering cherry millipede". In a report from 1950, an aggregation of about 6,000 individuals were encountered on a single bridge at McCormick's Creek State Park, Indiana. The species is extremely variable in coloration, and converges in appearance with several species of Apheloria and Brachoria as a result of mimicry.
Caseyidae is a family of millipedes in the order Chordeumatida. Adult millipedes in this family have 30 segments. There are about 7 genera and at least 40 described species in Caseyidae.
Striariidae is a family of millipedes in the order Chordeumatida. Adult millipedes in this family have 30 segments. There are at least 3 genera and about 13 described species in Striariidae.
Euryurus is a genus of flat-backed millipedes in the family Euryuridae. There are about 14 described species in Euryurus.
Pachydesmus is a genus of flat-backed millipedes in the family Xystodesmidae. There are about 12 described species in Pachydesmus.
Semionellus is a genus of flat-backed millipedes in the family Xystodesmidae. There are at least three described species in Semionellus.
Chonaphini is a tribe of flat-backed millipedes in the family Xystodesmidae. There are about 6 genera and 19 described species in Chonaphini.
Thrinaxoria is a genus of flat-backed millipedes in the family Xystodesmidae. There are at least three described species in Thrinaxoria.
Boraria is a genus of flat-backed millipedes in the family Xystodesmidae. There are about seven described species in Boraria.
Sigmoria is a genus of flat-backed millipedes in the family Xystodesmidae. There are more than 40 described species in Sigmoria.
Aniulus is a genus of millipedes in the family Parajulidae. There are more than 20 described species in Aniulus.
Cambala is a genus of millipedes in the family Cambalidae. There are about 18 described species in Cambala.
Abacion is a genus of crested millipedes in the family Abacionidae. There are about 10 described species in Abacion.
Auturus is a genus of flat-backed millipedes in the family Euryuridae. There are about 11 described species in Auturus.
Rudiloria is a genus of millipedes in the family Xystodesmidae, found in eastern North America.
Nannaria swiftae, also known as the Swift twisted-claw millipede or Taylor Swift's millipede, is a species of millipede in the family Xystodesmidae. It is found only in the Appalachian mountains of the U.S. state of Tennessee. It was discovered and described in 2022 by entomologists Derek Hennen, Jackson Means and Paul Marek, who expanded the genus Nannaria to 78 species. They named the species in honor of American singer-songwriter Taylor Swift.
