FACT: Living arthropods are divided into four subgroups. 1. Chelicerates (Subphylum Chelicerata) are a group of arthropods that include spiders, mites, horseshoe crabs, and scorpions. The first evolved about 445 million years ago during the Late Ordovician Period. Chelicerate bodies are divided into two regions, the cephalothorax and the opisthosoma. 2. Crustaceans (Subphylum Crustacea) include about 50,000 species of lobsters, crabs, shrimp, barnacles, brine shrimp and others. Most crustaceans live in marine or freshwater environments but there are also some terrestrial species. 3. Hexapods (Subphylum Hexapoda) are a group of arthropods that includes the insects. The body of a hexapod is divided into three sections, a head, thorax, and abdomen. 4. Myriapods (Subphylum Myriapoda) include about 13,000 species of millipedes and centipedes. Myriapods are terrestrial arthropods that are most abundant in forest habitats. They are notable for their long bodies and for having many pairs of legs.
Posted on: Sun, 08 Sep 2013 15:30:01 +0000
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