Based on scientific evidence and study, Spinosaurus is thought to have been the largest carnivorous dinosaur, exceeding in size even that of the more well-known Tyrannosaurus rex and Giganotosaurus. It is estimated to have reached sizes anywhere between forty-one to fifty-nine feet long. However, it is not as heavily-built as Tyrannosaurus rex or Giganotosaurus.
Spinosaurus has a long snout filled with conical teeth, and six-foot-high spines along its back that are covered and connected by skin to form a sail-like structure. It has very long, five-foot forearms, and while it spends much of its time on its two legs, it has been shown to occasionally crouch down onto all fours.
Spinosaurus is territorial, and is apparently not a very intelligent creature and/or has poor vision; as one Spinosaurus was mesmerised by the sight of an Anomaly and was later disoriented by the light effects of a music arena. Spinosaurus is also a highly resilient creature, as when one was brought down by EMD shots, it recovered within seconds.
In Primevalforest in the Cretaceous, a Spinosaurus found Connor fishing in its territory and reacted aggressively, chasing after him. Connor unintentionally led the Spinosaurus back to his and Abby Maitland's camp, where the Spinosaurus briefly attacked them in their den. Eventually it lost interest and left.
Later, when Connor and Abby moved two miles away to another location, the Spinosaurus returned and blocked the two's path to an Anomaly. When the Spinosaurus was mesmerised by the sight of the Anomaly, Abby lured a male Raptor to the Spinosaurus. The two predators fought aggressively, and the Spinosaurus was ultimately able to overpower and kill the Raptor by crushing it in its jaws. While the Spinosaurus was distracted, Connor and Abby escaped through the Anomaly, which was then locked.When Connor accidentally unlocked the Anomaly, the Spinosaurus came through into the Present. Confused and intimidated by the modern, urban environment, the creature went on a rampage through the streets of London; followed by Hilary Becker, Matt Anderson, Connor and Abby. Matt and Becker eventually blocked the Spinosaurus' path with a dumpster truck and Becker's car, until the creature became agitated and smashed into the dumpster truck. When Connor and Abby then arrived in a stolen car, and the Spinosaurus chased the car into a nearby arena.
After the team trapped the Spinosaurus in the arena, Connor went up to it to try and open a new Anomaly back to its era with the Anomaly Opening Device to send it through. The Spinosaurus almost devoured Connor until Abby activated the arena's light effects and music, which distracted and disoriented the Spinosaurus while Matt rescued Connor by pulling him up to the ceiling. Becker and his men brought the Spinosaurus down with EMDs, but the creature quickly recovered and tried to attack Matt and Connor (who were slightly too high up for it to reach).
When Connor accidentally dropped the Anomaly Opening Device down the Spinosaurus' throat, an Anomaly opened up from within the Spinosaurus and engulfed it, sending it through to an unknown time period.
- The Spinosaurus in Primeval was presented almost being completely accurately based on what is already known about the animal, from its size to its diet; it is implied to have been a fish-eater.
- The brief fight sequence between the Spinosaurus and the Raptor is an obvious homage to a mirrored scenario depicted in Jurassic Park, between the Tyrannosaurus Rex and a Velociraptor. If one listens carefully to when the Raptor is caught in the Spinosaurus’ jaws, the sound bytes of the Velociraptor squeals from the Jurassic Park series can be heard as the Raptor screams.
- Though the Spinosaurus is longer than the Giganotosaurus featured in Series 3, it is much more lightly built. That, added to its thin body frame, makes the Spinosaurus appear much smaller than it really is.
- Officially, the Spinosaurus is the first onscreen creature to have been shot by the EMD, which is shown to be an extremely effective weapon as it knocks the large Spinosaurus down momentarily.
- The Primeval Spinosaurus bears a similar shape and colour scheme to that of the Spinosaurus featured in episode 1 of the BBC documentary Planet Dinosaur, which aired later that same year.
- Another, much smaller, version of the Spinosaurus' spine is visible on the creature's tail, which a real life Spinosaurus would have lacked.