Spinosaurus californicus is among the largest of all known carnivorous dinosaurs, nearly as large as or, in some cases, even larger than Tyrannosaurus, Giganotosaurus and Carcharodontosaurus. Spinosaurus californicus can reach lengths of 15–16 metres (49–52 feet) and can weigh around 6.4–7.5 tonnes (7.1–8.3 short tons), due to the body design and size, it can stand and walk on all fours most of the time, being unable to run, but can stand on its back legs, either horizontally or vertically depending on which bipedal standing position the animal prefers. The skull of Spinosaurus californicus is long and narrow, similar to that of a native modern crocodilian. Spinosaurus is known feed on fish, but it hunts both terrestrial and aquatic prey (not just fish), dead or alive, despite being slow on land, it can easily feed on slow-moving land animals; it lives both on land and in water as a native modern crocodilian does. The distinctive spines of Spinosaurus, which are long extensions of the vertebrae, growing to at least 1.65 meters (5.4 ft) long and have skin connecting them, forming a sail-like structure. The sail-like structure on Spinosaurus californicus has multiple functions, including thermoregulation and display.