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Scorpions have scuttled around on Earth for around 435 million years with a flexible, segmented body part, also called a metasoma.

They scanned the scorpion’s metasoma using a form of CT imaging and compiled the scans to reconstruct the tail in three dimensions.

IXstg to XIIstg, the four pulmonary somites. met, The pentagonal metasternite of the prosoma behind all the coxae. x, The sternum of the pectiniferous somite. y, The broad first somite of the metasoma.

XIV to XVIII, The confluent or unexpressed six somites of the metasoma.

Arachnids, in which the somites corresponding to mesosoma and metasoma have entirely aborted.