The eponym anastomosis of Riolan suggests that Jean Riolan (1580-1657), a famous 17th century French anatomist, was the first to describe this mesenteric arterial connection between the superior and inferior mesenteric arteries. Riolan was a strong defender of traditional Galenic doctrine in medicine and proved a vigorous opponent of the new concept of the circulation of blood as exposed by William Harvey (1578-1657). As confirmed by examining his anatomy book published in 1649, it is unlikely that Riolan would have conceived an arterial collateral pathway in the mesocolon. He probably had observed vascular arcades running along the inner border of the colon. It was not until 1743 that Albrecht von Haller (1708-1777) gave a detailed description of the anatomy of the mesenteric arteries, referring to the arterial collateral connection between the superior and inferior mesenteric arteries as the Arcus Riolani in honor of an old master of anatomy.
van Gulik TM, Schoots I. Anastomosis of Riolan RevisitedThe Meandering Mesenteric Artery. Arch Surg. 2005;140(12):1225-1229. doi:10.1001/archsurg.140.12.1225