The upwards projecting neural spines of spinosaurid vertebrae (backbones) were very tall, more so than in most theropods. In life, these spines would have been covered in skin or fat tissue and formed a sail down the animal's back, a condition that has also been observed in some carcharodontosaurid and ornithopod dinosaurs. The eponymous neural spines of "Spinosaurus" were extremely tall, measuring over in height on some of the dorsal (back) vertebrae. "Suchomimus" had a lower, ridge-like sail across the majority of its back, hip, and tail region. "Baryonyx" showed a reduced sail, with a few of the rearmost vertebral spines being somewhat elongated. "Ichthyovenator" had a sinusoidal (wave-like) sail that was separated in two over the hips, with the upper ends of some neural spines being broad and fan-shaped. A neural spine from the holotype of "Vallibonavenatrix" shows a similar morphology to those of "Ichthyovenator", indicating the presence of a sail in this genus as well. One partial skeleton possibly referable to "Angaturama" also had elongated neural spines on its hip region. The presence of a sail in fragmentary taxa like "Sigilmassasaurus" is unknown. In members of the subfamily Spinosaurinae, like "Ichthyovenator" and "Spinosaurus", the neural spines of the caudal (tail) vertebrae were tall and reclined, accompanied by also elongated chevrons—long, thin bones that form the underside of the tail. This was most pronounced in "Spinosaurus", in which the spines and chevrons formed a large paddle-like structure, deepening the tail significantly along most of its length.