Paradoxosomatidae

Daday, 1889

flat-backed millipedes

Genus Guides

Paradoxosomatidae is the largest of flat-backed millipedes, containing nearly 200 and approximately 975 as of 2013. It is the sole family in the suborder Paradoxosomatidea. Members are distinguished by grooves on most body segments and a dumb-bell shaped aperture in males. The family includes notable groups such as the dragon millipedes of Southeast Asia and the widely introduced greenhouse millipede Oxidus gracilis.

Oxidus gracilis by (c)
Zoltán Korsós, some rights reserved (CC BY). Used under a CC-BY license.

Akamptogonus novarae by (c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda. Used under a CC-BY license.

Pronunciation

How to pronounce Paradoxosomatidae: //ˌpæɹəˌdɒksɔˈsɒmətɪdiː//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Paradoxosomatids can be distinguished from other polydesmidan millipedes by the combination of: present between paranota on most segments; second segment paranota positioned lower than collum and third segment paranota; and males with dumb-bell shaped aperture. The is further characterized by male projections on the fifth sternite in most . Dragon millipedes in the Desmoxytes are recognized by their spiky, spine-like projections and often bright aposematic coloration.

Images

Appearance

Paradoxosomatids are flat-backed millipedes with a distinct groove or furrow () between the keels (paranota) on most body segments. The keels of the second body segment are positioned lower on the body than those of the first segment (collum) and third segment. possess 19 or 20 body segments in addition to the . Ozopores (defensive gland openings) are located on the lateral margins of keels, typically on segments 5, 7, 9, 10, 12, 13, and 15 through the last segment. Males have a dumb-bell or hourglass-shaped aperture on the underside of the body, and most have one or two projections on the sternite of the fifth body segment.

Habitat

Paradoxosomatids occupy diverse terrestrial including forest litter, soil, and caves. The greenhouse millipede Oxidus gracilis is strongly associated with human-modified environments such as greenhouses and agricultural settings. Cave-dwelling , particularly in the Desmoxytes, exhibit extreme adaptations including elongated legs and , and loss of pigmentation. Some species show highly localized distributions, with certain cave-dwelling known from single cave systems.

Distribution

Occurs on all continents except Antarctica. Native distributions span Europe, Asia, Africa, Australia, and South America. North American records north of Mexico are exclusively introduced . Notable introduced include Oxidus gracilis (native to Japan, now in greenhouses), Asiomorpha coarctata (native to Southeast Asia, introduced to tropics), and Chondromorpha xanthotricha (native to Sri Lanka or southern India, introduced to tropics).

Diet

feeding on decaying plant matter and leaf litter. Some may also consume fungi.

Life Cycle

Development involves gradual growth through moulting. have 19 or 20 body segments plus the . Specific details vary among ; cave-dwelling species typically have low numbers and restricted distributions.

Behavior

Some exhibit swarming . Dragon millipedes in the Desmoxytes produce toxic hydrogen cyanide as a chemical defense. Cave-dwelling species show reduced densities compared to other cave groups. The greenhouse millipede Oxidus gracilis is strongly associated with human-disturbed .

Ecological Role

Paradoxosomatids function as decomposers in soil , contributing to nutrient cycling through consumption of decaying plant material. As ancient soil , they play a role in soil and ecosystem functioning.

Human Relevance

The greenhouse millipede Oxidus gracilis is a widespread introduced associated with agricultural and greenhouse environments, sometimes considered a nuisance pest. Dragon millipedes, particularly the 'shocking pink dragon ' Desmoxytes purpurosea, have attracted public and scientific attention for their distinctive appearance. Some species serve as models for evolutionary and biogeographic studies due to their restricted distributions and cave adaptations.

Similar Taxa

Other Polydesmida familiesParadoxosomatidae is distinguished by the combination of , dumb-bell shaped aperture, and specific paranotal positioning; other lack this particular suite of characters.
Julidae (order Julida)Julid millipedes are cylindrical rather than flat-backed, lack paranota entirely, and do not possess the grooves characteristic of Paradoxosomatidae.

More Details

Taxonomic structure

The is divided into three and 22 tribes. The subfamily Paradoxosomatinae contains over 760 in 17 tribes, representing the majority of diversity. Subfamily Alogolykinae contains approximately 60 species in two tribes distributed in central, south, and southeast Asia. Subfamily Australiosomatinae contains approximately 140 species in three tribes from Southeast Asia and Oceania.

Conservation significance

Cave-dwelling paradoxosomatids, particularly dragon millipedes in the Desmoxytes, often exhibit extreme rarity and narrow , with some known from single caves or cave systems. These characteristics make them valuable for evolutionary studies but also vulnerable to disturbance.

Research history

The has been subject to extensive taxonomic revision, with numerous new described from China, Vietnam, Laos, and other regions in recent years. Molecular phylogenetic studies have revealed instances of introgressive hybridization in Australian representatives of the family.