Case in point, the newly discovered Mosura fentoni. Life reconstruction of Mosura fentoni. CREDIT: Photo by Jean-Bernard Caron © ROMAdditionally, several Mosura fossils show details of internal anatomy seen in later arthropods, including some elements of the nervous system, circulatory system, and digestive tract. Open bloodInstead of having internal arteries and veins to transfer blood the way that most living mammals do, Mosura had an open circulatory system. “The well-preserved lacunae of the circulatory system in Mosura help us to interpret similar, but less clear features that we’ve seen before in other fossils.