font settings

Font Size: Large | Normal | Small
Font Face: Verdana | Geneva | Georgia

Arthropoda

(Phylum)

Overview

[ Back to top ]

The phylum of segmented animals with heads, jointed legs and a thick chitinous cuticle forming an exoskeleton. Arthropods include crustaceans, insects and arachnids.

Arthropods have hard exoskeletons, segmented bodies, and jointed appendages used for moving and feeding. Arthropods constitute over 90% of the animal kingdom. They are distinguished from other animals by an exoskeleton (a skeleton on the outside of the body), body divided into distinct parts, jointed legs and appendages, and bilateral symmetry (both sides of the body are the same).[1]

Photos

[ Back to top ]

Taxonomy

[ Back to top ]

The Phylum Arthropoda is a member of the Superphylum Panarthropoda. Here is the complete "parentage" of Arthropoda:

The Phylum Arthropoda is further organized into finer groupings including:

Classes

[ Back to top ]

Acarida

[more]

Arachnida

Arachnids are a class (Arachnida) of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function, while in other species, different appendages may grow large enough so as to appear like an extra pair of legs. The term is derived from the Greek words (ar?chne), meaning "spider". [more]

Arthropoda

An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda (from Greek ?rthron, "joint", and p?d?? pod?s "foot", which together mean "jointed feet"), and include the insects, arachnids, crustaceans, and others. Arthropods are characterized by their jointed limbs and cuticles, which are mainly made of a-chitin; the cuticles of crustaceans are also biomineralized with calcium carbonate. The rigid cuticle inhibits growth, so arthropods replace it periodically by molting. The arthropod body plan consists of repeated segments, each with a pair of appendages. It is so versatile that they have been compared to Swiss Army knives, and it has enabled them to become the most species-rich members of all ecological guilds in most environments. They have over a million described species, making up more than 80% of all described living animal species, and are one of only two animal groups that are very successful in dry environments ? the other being the amniotes. They range in size from microscopic plankton up to forms a few meters long. [more]

Branchiopoda

Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Cladocera, Notostraca and the Devonian Lepidocaris. They are mostly small, freshwater animals that feed on plankton and detritus, with the exception of the Cladocera, many of which are marine. [more]

Cephalocarida

Cephalocarida is a class inside the subphylum Crustacea that comprises only twelve shrimp-like benthic species. They were discovered in 1955 by , and are commonly referred to as horseshoe shrimps. They have been grouped together with the Remipedia in the Xenocarida. Although a second family, Lightiellidae, is sometimes used, all cephalocaridans are generally considered to belong in just one family: Hutchinsoniellidae. Even though there is no fossil record of cephalocaridans, most specialists believe them to be primitive among crustaceans. [more]

Chilopoda

Centipedes (from Latin prefix , "hundred", and pes, pedis, "foot") are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of legs, e.g. 15 or 17 pairs of legs (30 or 34 legs) but never 16 pairs (32 legs). A key trait uniting this group is a pair of venom claws or forcipules formed from a modified first appendage. Centipedes are a predominantly carnivorous taxon.:168 [more]

Collembola

Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Though the three orders are sometimes grouped together in a class called Entognatha because they have internal mouthparts, they do not appear to be more closely related to one another than they all are to insects, which have external mouthparts. [more]

Copepoda

Copepods (; meaning "oar-feet") are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic (drifting in sea waters), some are benthic (living on the ocean floor), and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as bioindicators. [more]

Crustacea

Crustaceans (Crustacea) form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to the Japanese spider crab with a leg span of up to 12.5 ft (3.8 m) and a mass of 44 lb (20 kg). Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by the nauplius form of the larvae. [more]

Diplopoda

Millipedes are arthropods that have two pairs of legs per segment (except for the first segment behind the head which does not have any appendages at all, and the next few which only have one pair of legs). Each segment that has two pairs of legs is a result of two single segments fused together as one. Most millipedes have very elongated cylindrical bodies, although some are flattened dorso-ventrally, while pill millipedes are shorter and can roll into a ball, like a pillbug. [more]

Entognatha

[more]

Eurypterida

[more]

Insecta

Insects (from Latin , a calque of Greek ??t???? [?ntomon], "cut into sections") are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body (head, thorax, and abdomen), three pairs of jointed legs, compound eyes, and two antennae. They are among the most diverse groups of animals on the planet, including more than a million described species and representing more than half of all known living organisms. The number of extant species is estimated at between six and ten million, and potentially represent over 90% of the differing metazoan life forms on Earth. Insects may be found in nearly all environments, although only a small number of species occur in the oceans, a habitat dominated by another arthropod group, the crustaceans. [more]

Malacostraca

Malacostraca is the largest of the six classes of crustaceans, containing over 25,000 extant species, divided among 16 orders. Its members display a greater diversity of body forms than any other class of animals, and include crabs, lobsters, shrimp, krill, woodlice, scuds (Amphipoda), mantis shrimp and many other less familiar animals. They are abundant in all marine environments and have also colonised freshwater and terrestrial habitats. They are united by a common , comprising 20 body segments (rarely 21), divided into a head, thorax and abdomen. [more]

Marrellomorpha

Maxillipoda

[more]

Maxillopoda

Maxillopoda is a diverse class of crustaceans including barnacles, copepods and a number of related animals. It does not appear to be a monophyletic group, and no single character unites all the members. [more]

Merostomata

Merostomata is the name given to a grouping of the extinct Eurypterida (sea scorpions) and the Xiphosura (horseshoe crabs). The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups. [more]

Ostracoda

Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species (13,000 of which are extant taxa) have been identified, grouped into several orders. [more]

Pauropoda

Pauropods are small, pale, centipede-like arthropods. They form the order Pauropodina, belonging to the monotypic class Pauropoda. About 500 species in four families are found worldwide, living in soil and leaf mould. They look rather like centipedes, but are probably the sister group to millipedes. The name is derived from the Greek roots pauro "small" and podo "foot". [more]

Ph-Arthropoda

[more]

Pycnogonida

Sea spiders, also called Pantopoda or pycnogonids, are marine arthropods of class Pycnogonida. They are cosmopolitan, found especially in the Mediterranean and Caribbean Seas, as well as the Arctic and Antarctic Oceans. There are over 1300 known species, ranging in size from 1 to 10 millimetres (0.039 to 0.39 in) to over 90 cm (35 in) in some deep water species. Most are toward the smaller end of this range in relatively shallow depths, however, they can grow to be quite large in Antarctic waters. [more]

Remipedia

Remipedia is a class of blind crustaceans found in coastal aquifers which contain saline groundwater, with populations identified in almost every ocean basin so far explored, including in Australia, the Caribbean Sea, the Atlantic Ocean. The first described remipede was the fossil Tesnusocaris goldichi (Lower Pennsylvanian), but, since 1979, at least seventeen living species have been identified with global distribution throughout the neo-tropical zone. [more]

Scorpionida

[more]

Symphyla

Symphylans, also known as garden centipedes or glasshouse symphylans, are soil-dwelling arthropods of the class Symphyla in the subphylum Myriapoda. Symphylans resemble centipedes, but are smaller and translucent. They can move rapidly through the pores between soil particles, and are typically found from the surface down to a depth of about 50 cm. They consume decaying vegetation, but can do considerable harm in an agricultural setting by consuming seeds, roots, and root hairs in cultivated soil. [more]

Trilobita

Trilobites (, /'tr?l?ba?t/; meaning "three lobes") are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period (526 million years ago), and they flourished throughout the lower Paleozoic era before beginning a drawn-out decline to extinction when, during the Devonian, almost all trilobite orders, with the sole exception of Proetida, died out. Trilobites finally disappeared in the mass extinction at the end of the Permian about 250 million years ago. The trilobites were among the most successful of all early animals, roaming the oceans for over 270 million years. [more]

Xiphosura

[more]

At least 10 species and subspecies belong to the Class Xiphosura.

More info about the Class Xiphosura may be found here.

Footnotes

[ Back to top ]
  1. http://bugguide.net/index.php?q=search&keys=Pseudocorticus&search=Search

Sources

[ Back to top ]
Last Revised: October 03, 2013
2013/10/03 15:38:50