Pentazonia is a taxonomic infraclass of

millipede 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 re ...

s containing the pill-millipedes (Oniscomorpha) which can roll into a ball and the order

Glomeridesmida Glomeridesmida is an order of millipedes in the infraclass Pentazonia containing 2 families and at least 31 species. Glomeridesmida is the only living order of the superorder Limacomorpha. Glomeridesmidans are small (less than ) and somewhat f ...

which cannot. Defining traits ( apomorphies) include divided

sternites The sternum (pl. "sterna") is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the ...

, a labrum with single median tooth, and an enlarged

pygidium The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is com ...

on the hind-most body segment. Pentazonia is in the dominant millipede subclass

Chilognatha Chilognatha is a subclass of the class Diplopoda, which includes the vast majority of extant millipedes, about 12,000 species. Taxonomy The classification of Chilognatha presented below is based on Shear, 2011, and Shear & Edgecombe, 2010 (e ...

which have a calcified exoskeleton and modified sperm-transferring legs in males. In contrast to the Helminthomorpha – the other Chilognathan infraclass, the sperm-transferring legs are located on posterior body segments and known as ''telopods''. Pentazonians are relatively short-bodied, with between 13 and 21 body segments. The Pentazonia contains one extinct order, Amynilyspedida, often referred to the Oniscomorpha.

References

Millipede taxonomy {{myriapoda-stub