Polyxenida
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Polyxenida | |
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File:Polyxenus.lagurus.1.jpg | |
Polyxenus lagurus | |
Scientific classification | |
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Penicillata
Latrielle, 1831
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Order: |
Polyxenida
Verhoeff, 1934
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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.
Contents
Description
Polyxenida differ from other millipedes in having a soft, non-calcified exoskeleton, unique tufts of bristles or setae, fewer legs (no more than 17 pairs), and an absence of copulatory appendages in males. Individuals are small, not exceeding 7 millimeters (0.28 inches).
Defense
Bristly millipedes lack the chemical defenses and hard exoskeleton of other millipedes,[1] and instead employ a unique defence mechanism: the distinctive barbed bristles can easily detach and become entangled in the limbs and mouth-parts of predatory insects, effectively immobilising them.[2]
Reproduction
Male Polyxenidans lack the modified sperm-transferring appendages (gonopods) found in most other millipede groups. As a result, sperm transfer is indirect: males deposit a spermatophore that is subsequently picked up by females.[3]
Many species reproduce asexually by way of parthenogenesis, wherein females lay eggs without mating and males are absent or rare.[4]
Classification
Polyxenida is the only living order of the subclass Penicillata, the basal subclass of millipedes. Penicillata is the sister group of all other living millipedes: the subclasses Pentazonia and Helminthomorpha).[6][7]
In 2003 the Polyxenida contained 159 valid species and/or subspecies,[8] although at least eight new species have been described since 2010.[5][9][10]
- Superfamily Polyxenoidea Lucas, 1840
- Hypogexenidae Schubart, 1947
- Lophoproctidae Silvestri, 1897
- Polyxenidae Lucas, 1840
- Superfamily Synxenoidea Silvestri, 1923
- Synxenidae Silvestri, 1923
Fossil history
The earliest representatives of Polyxenida are found in Lebanese amber from the Early Cretaceous period.[11]
Some authors place the extinct orders Arthropleurida and Eoarthropleurida (each represented by a single genus) within the Penicillata as a sister group to Polyxenida.[12][13]
References
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External links
- Media related to Lua error in package.lua at line 80: module 'strict' not found. at Wikimedia Commons
- Data related to Polyxenida at Wikispecies
- Polyxenida at the Encyclopedia of Life
- Photos of Polyxenida