Scorpions are a collective term for species in the order Scorpaenoidei of the phylum Arthropoda in the animal kingdom Spiders also belong to the arachnoid class. Their typical features include a slender body, claws, a curved segmented tail (posterior abdomen) with venomous spines. The earliest scorpions on land appeared about 430 million years ago in the Silurian period(Silurian)Any scorpion is poisonous, with varying degrees of toxicity. Small scorpions with smaller claws are more toxic than large scorpions with larger claws .