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Classification: Taxonomy, Relation With Other Groups If you absolutely loathe biological classification and all of it's obscure terminology, you're going to hate the crustaceans. There are so many "split-hairs" amongst it's groups that science types have taken to making new infra-, sectional-, you-name-it categories to sub-divide all the groups. I guess that's what you get with such a collection of diverse organisms and excellent fossil history. Anyway it won't hurt my feelings if you skip on down to the next subject heading. The Phylum Arthropoda (="jointed legs"). With the insects, trilobites, spiders, horseshoe crabs, scorpions, ticks, mites, sea spiders, centipedes, millipedes, (whew!) and a few other various and sundry groups, the subphylum Crustacea helps make up the largest phylum of life (Arthropoda); with some three quarters of a million described species. They all share 1) Metamerism: a division of the body into definite segments. 2) A pair of appendages per segment (at least in the primitive condition). 3) A nervous system with a dorsal, anterior brain, ventral nerve cord and ganglionic swellings in each segment. 4) Similar embryology/development. 5) Chitinous exoskeletons that cover the entire body; growth through periodic molting. 6) A muscular system that moves the animal by pulling on the exoskeleton. Enough of the higher taxonomy of the group! A synopsis of the arthropod classes: Subphylum Trilobita. The fossil trilobites. Subphylum Chelicerata. Chelicerae for mouthparts...
Subphylum Uniramia
Bibliography/Further Reading: Marine Hitchhiker/Critter ID (Maughmer, Toonen, Tompkins) |
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