Polydesmida

Not to be confused with Platydesmida or Polyzoniida.

Polydesmida
File:Apheloriavirginiensis.jpg
Apheloria virginiensis
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Myriapoda
Class:	Diplopoda
Superorder:	Merocheta Cook, 1895
Order:	Polydesmida Leach, 1815
Suborders
Dalodesmidea Leptodesmidea Brölemann, 1916 Paradoxosomatidea Daday, 1889 Polydesmidea Leach, 1815
Synonyms
Proterospermatophora Verhoeff, 1900

Polydesmida (from the Greek poly "many" and desmos "bond") is the largest order of millipedes, containing approximately 3,500 species, including all the millipedes reported to produce hydrogen cyanide (HCN).

Description

Members of the order Polydesmida are also known as "flat-backed millipedes", because on most species, each body segment has wide lateral keels known as paranota. These keels are produced by the posterior half (metazonite) of each body ring behind the collum. Polydesmids have no eyes, and vary in length from 3 to 130 mm (0.12 to 5.12 in). Including the telson, adults have 19 or 20 rings, while juveniles may have from 7 to 19 rings. Mature males have a single pair of gonopods consisting of the modified forward leg pair of the 7th segment. Many of the larger species show bright coloration patterns which warn predators of their toxic secretions.

Ecology

Polydesmids are very common in leaf litter, where they burrow by levering with the anterior end of the body.

Classification

The c. 3500 species of Polydesmida are variously classified into four suborders (names ending in "-idea"), and 28 families, the largest (numerically) including Paradoxosomatidae, Xystodesmidae, and Chelodesmidae.

Dalodesmidea Hoffman, 1980. 2 families

• Dalodesmidae Cook, 1896
• Vaalogonopodidae Verhoeff, 1940

Leptodesmidea Brölemann, 1916. 13 families

• Chelodesmoidea Cook, 1895
  • Chelodesmidae Cook, 1895
• Platyrhacoidea Pocock, 1895
  • Aphelidesmidae Brölemann, 1916
  • Platyrhacidae Pocock, 1895
• Rhachodesmoidea Carl, 1903
  • Rhachodesmidae Carl, 1903
  • Tridontomidae Loomis & Hoffman, 1962
• Sphaeriodesmoidea Humbert & de Saussure, 1869
  • Campodesmidae Cook, 1896
  • Holistophallidae Silvestri, 1909
  • Sphaeriodesmidae Humbert & de Saussure, 1869
• Xystodesmoidea Cook, 1895
  • Eurymerodesmidae Causey, 1951
  • Euryuridae Pocock, 1909
  • Gomphodesmidae Cook, 1896
  • Oxydesmidae Cook, 1895
  • Xystodesmidae Cook, 1895

Paradoxosomatidea Daday, 1889. 1 family

• Paradoxosomatidae Daday, 1889

Polydesmidea Pocock, 1887. 12 families

• Oniscodesmoidea Simonsen, 1990
  • Dorsoporidae Loomis, 1958
  • Oniscodesmidae DeSaussure, 1860
• Pyrgodesmoidea Silvestri, 1896
  • Ammodesmidae Cook, 1896
  • Cyrtodesmidae Cook, 1896
  • Pyrgodesmidae Silvestri, 1896
• Haplodesmoidea Cook, 1895
  • Haplodesmidae Cook, 1895
• Opisotretoidea Hoffman, 1980
  • Opisotretidae Hoffman, 1980
• Polydesmoidea Leach, 1815
  • Cryptodesmidae Karsch, 1880
  • Polydesmidae Leach, 1815
• Trichopolydesmoidea Verhoeff, 1910
  • Fuhrmannodesmidae Brölemann, 1916
  • Macrosternodesmidae Brölemann, 1916
  • Nearctodesmidae Chamberlin & Hoffman, 1958
  • Trichopolydesmidae Verhoeff, 1910

Representative diversity of Polydesmida

Asiomorpha coarctata (Paradoxosomatidae), an Asian species widely introduced by humans Asiomorpha coarctata (Paradoxosomatidae), an Asian species widely introduced by humans  Tasmaniosoma armatum (Dalodesmidae) from Tasmania Tasmaniosoma armatum (Dalodesmidae) from Tasmania  Eutrichodesmus aster (Haplodesmidae) from Vietnam, with unusual mid-dorsal crests Eutrichodesmus aster (Haplodesmidae) from Vietnam, with unusual mid-dorsal crests  A species of Xystodesmidae from the United States showing aposematic coloration A species of Xystodesmidae from the United States showing aposematic coloration  An paradoxosomatid from China, with reduced paranota An paradoxosomatid from China, with reduced paranota  Polydesmus collaris (Polydesmidae) from Europe Polydesmus collaris (Polydesmidae) from Europe

External links

• Data related to Polydesmida at Wikispecies
• Media related to at Wikimedia Commons
• Polydesmida at the Encyclopedia of Life
• External Anatomy of Polydesmida
• North American Polydesmida - BugGuide