Trilobite Legs (IMAGE) University of Adelaide Caption Fossil of Megistaspis trilobite showing the legs of one side: those on the head (legs 1-3) carrying short strong spines (yellow arrowheads), while those on the thorax (legs 4, 5) are smooth. Credit University of Adelaide Usage Restrictions only with this story License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.