Temporal range: Late Silurian–Recent
Lithobius forficatus, a centipede Scientific classification Kingdom: Animalia Phylum: Arthropoda Subphylum: Myriapoda
Myriapoda is a subphylum of arthropods containing millipedes, centipedes, and others. The group contains 13,000 species, all of which are terrestrial. Although their name suggests they have myriad (10,000) legs, myriapods range from having over 750 legs (Illacme plenipes) to having fewer than ten legs.
The fossil record of myriapods reaches back into the late Silurian, although molecular evidence suggests a diversification in the Cambrian Period, and Cambrian fossils exist which resemble myriapods.
The scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists.
Myriapods have a single pair of antennae and, in most cases, simple eyes. The mouthparts lie on the underside of the head, with an "epistome" and labrum forming the upper lip, and a pair of maxillae forming the lower lip. A pair of mandibles lie inside the mouth. Myriapods breathe through spiracles that connect to a tracheal system similar to that of insects. There is a long tubular heart that extends through much of the body, but usually few, if any, blood vessels.
Malpighian tubules excrete nitrogenous waste into the digestive system, which typically consists of a simple tube. Although the ventral nerve cord has a ganglion in each segment, the brain is relatively poorly developed.
During mating, male myriapods produce a packet of sperm, or spermatophore, which they must transfer to the female externally; this process is often complex and highly developed. The female lays eggs which hatch as much shortened versions of the adults, with only a few segments and as few as three pairs of legs. The young add additional segments and limbs as they repeatedly moult to reach the adult form.
Myriapods are most abundant in moist forests, where they fulfill an important role in breaking down decaying plant material, although a few live in grasslands, semi-arid habitats or even deserts. The majority are detritivorous, with the exception of centipedes, which are chiefly nocturnal predators. Pauropodans and symphylans are small, sometimes microscopic animals that resemble centipedes superficially and live in soils. Millipedes differ from the other groups in having their body segments fused into pairs, giving the appearance that each segment bears two pairs of legs, while the other three groups have a single pair of legs on each body segment.
Although not generally considered dangerous to humans, many myriapods produce noxious secretions (often containing benzoquinones) which can cause temporary blistering and discolouration of the skin.
There has been much debate as to which arthropod group is most closely related to the Myriapoda. Under the Mandibulata hypothesis, Myriapoda is the sister taxon to Pancrustacea, a group comprising the Crustacea and Hexapoda. Under the Atelocerata hypothesis, Hexapoda is the closest, whereas under the Paradoxopoda hypothesis, Chelicerata is the closest. This last hypothesis, although supported by few, if any, morphological characters, is supported by a number of molecular studies.
There are four classes of extant myriapods, Chilopoda (centipedes), Diplopoda, Pauropoda and Symphyla, containing a total of around 12,000 species. While each of these groups of myriapods is believed to be monophyletic, relationships among them are less certain.
Centipedes make up the order Chilopoda. They are fast, predatory and venomous, hunting mostly at night. There are around 3,300 species, ranging from the diminutive Nannarup hoffmani (less than half an inch in length, c. 12 mm) to the giant Scolopendra gigantea, which may exceed 30 centimetres (12 in).
Most millipedes are slower than centipedes, and feed on leaf litter and detritus. They are distinguished by the fusion of each pair of body segments into a single unit, giving the appearance of having two pairs of legs per segment. Around 8,000 species have been described, which may represent less than a tenth of the true global millipede diversity. One species, Illacme plenipes has the greatest number of legs of any animal, with 750. The name "millipede" is a compound word formed from the Latin roots milli ("thousand") and ped ("foot"), although millipedes typically have between 36 and 400 legs. Pill millipedes are much shorter, and are capable of rolling up into a ball, like pillbugs.
About 200 species of symphylans are known worldwide. They resemble centipedes but are smaller and translucent. Many spend their lives as soil infauna, but some live arboreally. Juveniles have six pairs of legs, but, over a lifetime of several years, add an additional pair at each moult so that the adult instar has twelve pairs of legs.
Pauropoda is another small group of small myriapods. They are typically 0.5–2.0 mm long and live in the soil on all continents except Antarctica. Over 700 species have been described. They are believed to be the sister group to millipedes, and have the dorsal tergites fused across pairs of segments, similar to the more complete fusion of segments seen in millipedes.
Arthropleuridea were ancient myriapods that are now extinct. The most famous members are from the genus Arthropleura, which was a giant, probably herbivorous, animal that could be up to 3 metres (9.8 ft) long. Arthropleuridea may be a division of the millipedes.
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Extant arthropod classes by subphylum Chelicerata Myriapoda Hexapoda Crustacea
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Myriapoda — Myr i*ap o*da, n. pl. [NL., fr. Gr. ? numberless + poda.] (Zo[ o]l.) A class, or subclass, of arthropods, related to the hexapod insects, from which they differ in having the body made up of numerous similar segments, nearly all of which bear… … The Collaborative International Dictionary of English
Myriapoda — [zu griechisch poús, podós »Fuß«], wissenschaftlicher Name der Tausendfüßer … Universal-Lexikon
Myriapoda — Myriapoda, Tausendfüßer, die zum Unterstamm der ⇒ Antennata gehörenden Klassen der ⇒ Chilopoda und ⇒ Progoneata. Der Rumpf der M. enthält meist eine große Anzahl extremitätentragender Segmente … Deutsch wörterbuch der biologie
Myriapoda — Myriapoda Un quilópodo … Wikipedia Español
Myriapoda — In diesem Artikel oder Abschnitt fehlen folgende wichtige Informationen: Wieviele Beine haben Tausendfüßer im Durchschnitt, was ist die geringste und was die höchste Zahl? Bitte nur Angaben durch seriöse Quellen gedeckt, also mit… … Deutsch Wikipedia
Myriapoda — Myriapodes Trigoniulus … Wikipédia en Français
Myriapoda — noun arthropods having the body composed of numerous double somites each with two pairs of legs: millipedes • Syn: ↑Diplopoda, ↑class Diplopoda, ↑class Myriapoda • Hypernyms: ↑class • Member Holonyms: ↑Arthropoda, ↑ … Useful english dictionary
Myriapoda — … Википедия
Myriapoda — Myr·i·ap·o·da .mir ē ap ə də n pl syn of MYRIOPODA * * * Myr·i·ap·o·da (mir″e apґə də) [myria + Gr. pous foot] a superclass of arthropods, including the classes Chilopoda (centipedes) and Diplopoda (millipedes) … Medical dictionary
myriapoda — n. family of arthropods that include the centipede and millipedes … English contemporary dictionary