Palpigradi are commonly known as microwhip scorpions and have a weakly sclerotized exoskeleton compared to other arachnids.
Palpigrades, commonly known as microwhip scorpions, are arachnids belonging to the order Palpigradi. Their exoskeleton is very weakly sclerotized compared to other arachnids, which is the reason why fossils are so rare, and go no further back than 99 million years ago in Burmese Amber. 
