This vintage, distressed design highlights Arthropleura, the colossal millipede-like arthropod that thrived in the Carboniferous Period, when atmospheric oxygen levels soared to around 35%. Rendered in detailed white linework against a deep black backdrop, the shirt blends natural history accuracy with bold paleo-humor for an eye-catching retro aesthetic. Made from 100% ring-spun cotton (high-quality cotton) with a soft, sensory-friendly feel. Every order funds kelp restoration on the Pacific Northwest coast.