Haemal Arch of Edmontosaurus annectens
The haemal arch, or chevron, as it is commonly known, is one of a series of similar bones that lay below and articulated with the lower surface of the caudal (tail) vertebrae. They are also present in modern reptiles, such as the iguana. The blood supply to the tail ran through the arches created by articulation of the chevron with the vertebrae. These bones also served as anchors for the substantial musculature of the tail. Some have speculated hadrosaurs were aquatic, or semi-aquatic, in which case, the tail may have provided locomotion in the water
