Phylum Arthropida Class Chelicerata Subclass Arachnida Number of families 648
Highly recognizable and populous eight-k invertebrates with two body parts (a prosoma and an abdomen), pedipalps, book lungs or tracheae, sometimes poisonous fangs, and generally the ability to produce silk; they are terrestrial chelicerates (invertebrates with pincer-shaped mouthparts)
Photo: A smooth-headed scorpion (Opisthopthal-mus) in defensive posture. (Photo by Ann & Steve Toon Wildlife Photography. Reproduced by per-
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