Thelyphonus sepiaris specimens exhibit a black or blackish-brown deep coloration with reddish brown coloration with reddish brown undersides. It features distinctocular ridges along its carapace margin and exhibits specific anatomical characteristics on its pedipalp, including teeth on the trochanter and femur. Notably, the first abdominal sternum has a pronounced posterior border. T. sepiaris has tibial spines on its second, third, and fourth leg pairs and a telson with 27hairy segments.