In case you are a bit fuzzy on high school biology, the phylum Arthropoda (joint-footed) shares several notable features: exoskeletons of chitin, segmented bodies, and jointed limbs. The arthropod phylum is further divided into five subphyla—although arthropod relationships are currently undergoing revision based on molecular analyses. One subphylum, Trilobita, is extinct. Chelicerata includes the arachnids, horseshoe crabs, and sea spiders; Hexapoda includes the insects and several other six-footed groups; and Crustacea includes roly-polys in addition to crabs, barnacles, brine shrimp, and a few other groups. Finally, there are the Myriapoda (many-footed), which includes the centipedes, millipedes, and symphylans.
In addition to having similar body segments and a single pair of antennae, Myriapods are distinguished by having, as you might expect, myriad legs. They lack the protective calcium-enhanced exoskeleton of the largely aquatic crustaceans, or the waxy cuticle of insects, and require a moist environment to survive. While the Diplopoda (pair-footed) and Chilopoda (lip-footed—more on that in a moment) look superficially similar, they are very different groups; Symphyla (wh...
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