Plural of cephalothorax; the fused head and thorax (upper body) region of arthropods like crustaceans and arachnids.
From Greek kephalē (head) + thorax (chest/trunk). The plural form 'cephalothoraces' is the standard Latin/Greek plural, though 'cephalothoraxes' is sometimes used in English.
Spiders and crabs look so different from us because their heads aren't separate—their heads and bodies are fused into one combined unit called the cephalothorax, which is one of nature's most successful body-plan designs.
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