Illustration by Tyrannus Paleo of JPLegacy

Isla Sorna

Physical CharacteristicsEdit

Length: 45 feet (male), 30 feet (female)
Height: 4 feet
Weight: 8 tons for males, 7 tons for females


Adult (both sexes): Darkly colored, ranging from dark greens to jet black; to black with a blueish tinge, all with pale under-belly.
Juvenile (both sexes): Black with yellow or green speckles and stripes.


Mainly fish, but it will attack almost anything unfortunate enough to cross its path, including large and small ornithopods and theropods, smaller-sized sauropods, native Costa Rican bird and mammal species and other Deinosuchus. It will also scavenge carrion, sometimes stealing food from other predators including Tyrannosaurus; and can eat up to half its body weight at a single feeding. Small animals are swallowed whole, while bigger prey is torn into bite-sized chunks.

Preferred HabitatEdit

Deep water with animal drinking beaches nearby, such as the River and Deep Channel. Deinosuchus will occasionally swim out to sea and is able to reach the neighboring islands of Muerta, Matanceros, Pena and Tacaño.

Social StructureEdit

The largest adults of either sex tend to be solitary and territorial, reacting aggressively towards others of a similar size. Sub-adult and smaller individuals have a higher tolerance of each other and even have a hierarchy of sorts, with the most dominant individuals eating first from a kill and having access to the most desirable basking areas. Groups of sub-adults will also co-operate together in order to capture prey. It is not uncommon for large groups of Deinosuchus to participate in a feeding frenzy, tolerating one another only when food is readily available. Several individuals may also bask along the same stretch of shoreline, being respectful of space.


Gigantic alligator. Broad snout with a slightly bulbous tip, more pronounced in males. Teeth are thick and robust; those close to the rear of the jaws are short, rounded, and blunt; adapted for grabbing and crushing rather than piercing. When the jaws are closed, only the fourth tooth of the lower jaw is visible. The nictitating membranes cover its eyes when its head is underwater. In addition, glands on the nictitating membrane secrete a salty lubricant that keeps the eye clean. The tongue cannot move freely but is held in place by a folded membrane. Males tend to be larger than females.

Breeding SeasonEdit

Wet season when water levels are at their highest, which increases chances of survival for their offspring.


The master of Isla Sorna's waterways is a gigantic species of prehistoric alligator; one of the largest crocodilians the world has ever seen. A force to be reckoned with by all of Sorna's inhabitants, Deinosuchus boasts armor plating surpassed only by Ankylosaurus; and a bite force equal to or even surpassing that of Tyrannosaurus. Deinosuchus has a secondary bony palate, which permits it to breathe through its nostrils while the rest of the head is submerged underwater. A stalk and ambush predator, Deinosuchus is a practitioner of patience and can wait for hours on end while submerged, waiting to sense the vibrations of an unsuspecting victim approaching the bank to drink. Deinosuchus most often hunts at night, using its acute hearing and sight.

Once the target is in range, Deinosuchus will lunge and grab the unfortunate victim before it can escape, dragging it into the water. The massive alligator will then proceed to either hold its victim underwater until it eventually drowns, or thrash and roll about in order to shred and tear chunks of flesh from the bitten area and cause the victim to bleed profusely. A special valve at the back of the throat allows the mouth to be opened to catch and hold prey underwater without water entering the throat. Sometimes, when food is plentiful, Deinosuchus will make a kill and then store it underwater. This causes a controlled rot that softens up the food, so it is easier to tear off chunks of flesh to swallow whole.

Sub-adult and smaller adults use their bodies and tails to herd groups of fish toward a bank, and eat them with quick sideways jerks of their heads. They also cooperate, blocking migrating fish by forming a semicircle across the river. Groups of Deinosuchus may travel hundreds of meters from a waterway to feast on a carcass. When groups are sharing a kill, they use each other for leverage, biting down hard and then twisting their bodies to tear off large pieces of meat in a "death roll". They may also get the necessary leverage by lodging their prey under branches or stones, before rolling and ripping. When not hungry, Deinosuchus will often haul its massive body onto the shore to bask in good weather, opening its jaws to allow egrets and Compsognathus to pick out pieces of rancid meat, leeches and other parasites from between its teeth.

Breeding BehaviorsEdit

During the mating season males will bellow to declare territory; and attract females by slapping their snouts in the water, blowing water out of their nostrils, and making a variety of other noises including infrasound's, which causes the water above their backs to vibrate. The larger males of a population tend to be more successful. Once a female has been attracted, the pair warble and rub the undersides of their jaws together. After mating, the female will crawl up on the bank and builds a compost mound nest of rotting leaves, twigs and branches encased in mud, in a sheltered spot in or near the water. Both parents will guard the nest until the eggs hatch, aggressively charging at any creature that comes too close. The hatching young produce a distinctive squeak. Once the female hears the hatchlings calling for her, she will dig them out to free them before carrying them in her jaws to a small nursery pond. The parents will then remain for a short while, before abandoning their offspring and resuming their solitary lives. The young are capable of fending for themselves, feeding on mostly fish, frogs and invertebrates, gradually moving onto larger prey. Being so small, they are often considered prey themselves, to not only theropod dinosaurs such as Spinosaurus but also bigger Deinosuchus. Therefore the juveniles are very elusive, keeping away from deeper water which may harbor the bigger carnivores and being capable of very rapid movement in order to escape their enemies. Often the juveniles of multiple females gather together to form moderate-sized creches, which increases their chances of survival.

During aquatic locomotion, Deinosuchus' muscular tail undulates from side to side to drive the animal through the water while the limbs are held close to the body to reduce drag. When the animal needs to stop, steer, or maneuver in a different direction, the limbs are splayed out. Deinosuchus generally cruises slowly on the surface or underwater with gentle sinuous movements of the tail, but when pursued or when chasing prey it can move rapidly. Despite its bulk, Deinosuchus is surprisingly agile on land, capable of short bursts of speed. This often takes many animals by surprise when a seemingly lethargic Deinosuchus charges them suddenly and unexpectedly.


Page Illustration by Tyrannus Paleo Text from the LtL Isla Sorna Field Guide