Female Mosasaur

Some prey species of mosasaurs are known from specific impressions left on them, rather than from the stomach contents of their predators. For example, unusual holes have been found on ammonite shells (primarily Pachydiscus and Placenticeras). These were once identified as parasite damage, but it was later determined that the triangular shape of the holes on some of them, their size, and the presence of them on both sides correspond to the upper and lower jaws of a medium-sized or small mosasaur, most likely Platecarpus. It is unknown whether larger mosasaurs ate ammonites, although the lack of evidence, even in sites where large numbers of ammonite and large mosasaur fossils are known, suggests that cephalopods were likely not an energetically valuable food source for larger mosasaurs.[61] The carapace of the giant sea turtle Allopleuron hofmanni bears tooth marks from a large mosasaur of the genus Mosasaurus or Prognathodon.[62] Mosasaur tooth marks have also been found on the bones of some large long-necked plesiosaurs, and the fin of a juvenile short-necked plesiosaur is known to have been literally sliced ​​open by the teeth of a small Prognathodon.[63] A mosasaur has been found in a grip on the plesiosaur Mauisaurus haasti in New Zealand.[64] The mantle of a giant cephalopod has been described as bearing tooth cuts from an unidentified mosasaur.[60] Hadrosaur bones from Alaska bear evidence of being eaten by a Tylosaurus, most likely the result of scavenging an animal washed up at sea. Shark tooth marks (mostly from Squalicorax) are often found on mosasaur bones, demonstrating the sharks' consumption of the dead bodies of giant marine lizards.[68] However, two discoveries of Cretoxyrhina tooth marks on the bones of early mosasaurs (representatives of the genera Clidastes, Tylosaurus, or Platecarpus), mainly from the Campanian of Kansas, are known, which bear signs of healing, and thus suggest

The stomach contents of some mosasaurs are known: one specimen of Tylosaurus proriger contained in its stomach area the fossilized remains of the flightless seabird Hesperornis, large bony fishes, the smaller mosasaur Platecarpus tympaniticus, and a shark. The stomachs of other tylosaurs (T. proriger and T. nepaeolicus) were found to contain the fossilized remains of a huge shark, the hybodont Ptychodus mortoni, a Clidastes sp., another Platecarpus planifrons, a large Xiphactinus audax, and a short-necked plesiosaur of the genus Dolichorhynchops[56]. The stomach of a small genus of mosasaur (Mosasaurus missouriensis, about 6.5 m long) was found to contain the fossil remains of a meter-long bony fish, bitten in several places,[57] while the stomach of another mosasaur of this genus contained the fossil remains of an unidentified mosasaur of the subfamily Plioplatecarpinae and a poorly preserved non-mosasaur. Fossil remains of Plioplatecarpus sp., an unidentified mosasaur, and sea turtle bones were found in the stomach area of ​​Gainosaurus.[56] The latter were likely swallowed whole by Gainosaurus or eaten from its shell, as its flexible jaws and blade-like teeth are well suited for cutting skin and meat, but not for biting through hard armor. The stomach contents of a small Prognathodon (Prognathodon overtoni, about 5.9 m long) included very large bony fish, over 25% of the total body length of the mosasaur, a turtle with a shell about 60 cm long, and possibly a cephalopod.[58] In the stomach area of ​​Prognathodon kianda, at the same time, fossil remains of three other mosasaurs were found, including a young individual of its species.[59] Small mosasaurs with very mobile skulls, Platecarps, contained in the stomach area only bony fish up to 1.2 m long (although the structure of their teeth suggests the possibility of sometimes feeding on other, larger animals). In the stomach area, a raft

Mosasaurs occupied many ecological niches in the Cretaceous seas, primarily those of active large- and medium-sized predators. Giant mosasaurs, adapted to killing large prey, occupied the top of the food chain in the Late Cretaceous seas.

Due to their rapid metabolism, mosasaurs required relatively larger amounts of food than modern reptiles. Early mosasaurs had bifurcated lower jaws and multiple mobile joints in the skull, vaguely reminiscent of snakes in this regard. This cranial kineticism allowed them to swallow relatively large prey items whole, and the teeth on the pterygoids, like those of some moray eels, helped mosasaurs push large chunks of food down the throat. However, the cranial kineticism of some later forms was greatly reduced, and many of their teeth acquired a cutting morphotype, allowing advanced mosasaurs to easily cut chunks of meat from very large prey and also withstand the stresses caused by its resistance. However, some mosasaurs, such as Globidens, developed rather unusual feeding adaptations. The teeth of this mosasaur were spherical, suitable for biting into mollusk shells, similar to the teeth of Triassic placodonts[55]. The stomach contents of some mosasaurs are known: one specimen of Tylosaurus proriger contained in the stomach area the fossil remains of the flightless seabird Hesperornis, large bony fish, the smaller mosasaur Platecarpus tympaniticus, and a shark. In the stomachs of other tylosaurs (T. proriger and T. nepaeolicus) were found the fossil remains of a huge shark - the hybodont Ptychodus mortoni, a clidastes (Clidastes sp.), another platecarpus (Platecarpus planifrons), a large xiphactinus (Xiphactinus audax) and a short-necked plesiosaur of the genus Dolichorhynchops[56]. In the stomach of a small genus of mosasaur (Mosasaurus missouriensis, about 6.5 m long) were found the fossil remains of a meter-long bony fish, bitten in several places[57], while the yellow

The placement of the kidneys further forward in the abdominal region is more reminiscent of cetaceans than monitor lizards. Like cetaceans, the bronchi leading to the lungs in mosasaurs ran parallel to each other, rather than overlapping as in monitor lizards and other terrestrial and semi-aquatic lizards. These anatomical features are most likely a consequence of complete adaptation to a marine lifestyle.[36]

Mosasaurs had a body shape similar to that of modern monitor lizards, but more elongated and streamlined. The heads of many mosasaurs were typically larger relative to their bodies than those of monitor lizards. The limb bones were reduced, and their long fingers formed flippers that helped the animals turn while moving. Their tails were widened and flattened. Until recently, it was believed that mosasaurs used a relatively primitive swimming method, typical of ambush hunters such as moray eels, crocodiles, and sea snakes: they pushed off the water by wriggling their entire bodies. However, modern research has shown that advanced mosasaurs had hypocercal caudal fins, reminiscent of those of metriorhynchids, ichthyosaurs, and some sharks. Instead of actively moving, the front of the mosasaur's body remained relatively motionless to reduce drag, and all propulsion was done by the tail. Thus, these animals were not specialized ambush hunters and could have actively pursued their prey through the water column. The skeletal structure of advanced mosasaurs demonstrates a good adaptation for active swimming, while primitive mosasaurs, such as Dallasaurus, have a skeletal structure reminiscent of terrestrial or semiaquatic lizards. Mosasaurs had thecodont teeth, like crocodiles. Despite the numerous fossil remains of various mosasaurs from around the world, little is known about their skin. A few specimens, however, preserve fossilized scale impressions. Until the discovery of well-preserved impressions from the late Maastrichtian of Jordan[44], mosasaur skin was described mainly on the basis of fossil remains of fairly primitive mosasaurs from the Santonian-lower Campanian, such as the famous Tylosaurus specimen KUVP-1075 from Kansas.[45] The material from Jordan shows that the bodies of mosasaurs, as well as the webbing between the toes on the forelimbs and hindlimbs, were covered with small

Mosasaurs were a large group of Late Cretaceous marine reptiles, primarily large- to medium-sized predators. Most known species inhabited the warm, shallow seas common during the Late Cretaceous. Due to their specialization, mosasaurs were very different from modern lizards: their internal organ structure more closely resembled that of cetaceans, they were viviparous, had high metabolic rates, and were warm-blooded. Mosasaurs likely descended from an extinct family of aquatic lizards, the Aigialosauridae.[4] During the last 20 million years of the Cretaceous (Turonian–Maastrichtian), mosasaurs outcompeted all their competitors, such as large lamniform sharks and the last pliosaurs, and became the dominant marine predators of their time. They disappeared along with the dinosaurs and pterosaurs in the end-Cretaceous mass extinction event 66 million years ago.