Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a result of two single segments fused together. Most millipedes have very elongated cylindrical or flattened bodies with more than 20 segments, while pill millipedes are shorter and can roll into a tight ball. Although the name "millipede" derives from Latin for "thousand feet", no species was known to have 1,000 or more until the discovery in 2020 of Eumillipes persephone, which can have over 1,300 legs. There are approximately 12,000 named species classified into 16 orders and around 140 families, making Diplopoda the largest class of myriapods, an arthropod group which also includes centipedes and other multi-legged creatures.
Pill millipedes are any members of two living orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the millipedes' resemblance to certain woodlice (Oniscidea), also called pillbugs or "roly-polies". However, millipedes and woodlice are not closely related ; rather, this is a case of convergent evolution.
Polyxenida is an order of millipedes readily distinguished by a unique body plan consisting of a soft, non-calcified body ornamented with tufts of bristles – traits that have inspired the common names "bristly millipedes" or "pincushion millipedes". There are at least 86 species in four families worldwide, and are the only living members of the subclass Penicillata.
Polyxenidae is a family of millipedes in the order Polyxenida containing approximately 47 species in 19 genera. Adults in all species in this family have 13 pairs of legs.
Harold Frederick Loomis was an American botanist and myriapodologist known for his contributions to agronomy, plant pathology, and millipede taxonomy. He worked for the U.S. Department of Agriculture for over four decades, studying diseases of crop plants, and was a colleague of Orator F. Cook. He also made major contributions to the natural history of Central America and the West Indies, naming over 500 species of millipedes in total. He co-described with Cook the leggiest animal on earth: Illacme plenipes, with over 700 legs.
Siphonorhinidae is a family of millipede in the order Siphonophorida. There are at least 4 genera and about 12 described species in Siphonorhinidae.
Siphonophoridae is a family of millipedes in the order Siphonophorida. There are about 12 genera and more than 110 described species in Siphonophoridae.
Andrognathidae is a family of millipede in the order Platydesmida. There are about 17 genera and more than 30 described species in Andrognathidae.
Platydesmidae is a family of millipede in the order Platydesmida. There are at least 2 genera and more than 30 described species in Platydesmidae.
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.
Conotylidae is a family of millipedes in the order Chordeumatida. Adult millipedes in this family have 30 segments. There are about 19 genera and at least 60 described species in Conotylidae.
Craspedosomatidae is a family of millipedes in the order Chordeumatida. Most adult millipedes in this family have 30 segments, but some have only 28. There are at least 30 genera and 210 described species in Craspedosomatidae.
Rhiscosomides is a genus of millipedes in the order Chordeumatida with seven described species, and is the only genus in the family Rhiscosomididae. Adult millipedes in this family have 30 segments.
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.
Trichopetalidae is a family of millipedes in the order Chordeumatida. Adult millipedes in this family have 28 or 30 segments. There are about 5 genera and at least 30 described species in Trichopetalidae.
Pachydesmini is a tribe of flat-backed millipedes in the family Xystodesmidae. There are at least 3 genera and more than 20 described species in Pachydesmini.
Chonaphini is a tribe of flat-backed millipedes in the family Xystodesmidae. There are about 6 genera and 19 described species in Chonaphini.
Xystocheirini is a tribe of flat-backed millipedes in the family Xystodesmidae. There are about 5 genera and more than 40 described species in Xystocheirini.
Rhachodesmidae is a family of flat-backed millipedes in the order Polydesmida. There are more than 20 genera and at least 80 described species in Rhachodesmidae.
