But today’s roach might look like the preferable choice next to an ancient arthropod that once scurried across the ocean floor. The trackways were several feet long and captured an animal capable of making rapid turns and sometimes using only a fraction of its legs at a time. At an estimated 3.3 feet (1 m) long, P. gigas is the largest known scorpion. The head alone measures more than 2.7 feet (0.8 m) long and contains an impressive collection of piercing and crushing teeth. Growing up to about 43 feet (13.1 m) long, T. rex ranks among the largest known mosasaurs.