Comparison of even-toed ungulate and cetaceans genetic material has shown that the closest living relatives of whales and hippopotamuses is the paraphyletic group Artiodactyla. Dan Graur and Desmond Higgins were among the first to come to this conclusion, and included a paper published in 1994.
Definition of roundâtrip. : a trip to a place and back usually over the same route.
1 Circumference: the length of one circuit along the circle, or the distance around the circle.  Diameter: a line segment whose endpoints lie on the circle and which passes through the centre; or the length of such a line segment, which is the largest distance between any two points on the circle.