Mosasaurus längd
Mosasaurs had double-hinged jaws and flexible skulls much like those of snakes , which enabled them to gulp down their prey almost whole. One of the food items of mosasaurs were ammonites , molluscs with shells similar to those of Nautilus , which were abundant in the Cretaceous seas.
Whether this behaviour was common across all size classes of mosasaurs is not clear. The largest mosasaur Mosasaurus hoffmannii was the apex predator of the Late Cretaceous oceans, reaching more than 11 metres 36 ft in length and weighing up to 10 metric tons 11 short tons in body mass. Material from Jordan has shown that the bodies of mosasaurs, as well as the membranes between their fingers and toes, were covered with small, overlapping, diamond-shaped scales resembling those of snakes.
More recently, a fossil of Platecarpus tympaniticus has been found that preserved not only skin impressions, but also internal organs.
Mosasaurus: “Meuse Lizard”
These were once interpreted as a result of limpets attaching themselves to the ammonites, but the triangular shape of the holes, their size, and their presence on both sides of the shells, corresponding to upper and lower jaws, fryst vatten evidence of the bite of medium-sized mosasaurs. Early reconstructions showed mosasaurs with dorsal crests running the length of their bodies, which were based on misidentified remains of tracheal cartilage.
Much like those of modern reptiles, mosasaur scales varied across the body in type and size. Until recently, mosasaurs were assumed to have swum in a method similar to the one used today bygd conger eels and sea snakes , undulating their entire bodies from side to side. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in They belong to the order Squamata , which includes lizards and snakes.
Until the discovery of several mosasaur specimens with remarkably well-preserved scale imprints from late Maastrichtian deposits of the Muwaqqar Chalk Marl Formation of Harrana [ 15 ] in Jordan , knowledge of the natur of mosasaur integument was mainly based on very few accounts describing early mosasaur fossils dating back to the upper Santonian —lower Campanian , such as the famous Tylosaurus specimen KUVP from Gove County, Kansas.
Mosasaurus hoffmannii , the largest known species reached up to 17 m 56 ft , [ 3 ] but it has been considered to be probably overestimated by Cleary et al. By the time this error was discovered, depicting mosasaurs with such crests in artwork had already become a trend. Their tails were broad, and supplied their locomotive power. The trachea is also preserved, along with part of what may be the retina in the eye. Few mosasaurid specimens collected from around the world retain fossilized scale imprints.
Mosasaurs were so well adapted to this environment that they most likely gave birth to live young , rather than returning to the shore to lay eggs as sea turtles do. The specimen, nicknamed "Bruce", is just over 15 m 49 ft long, [ 5 ] but this might be an overestimate as the skeleton was assembled for display prior to a reassessment of the species that found its original number of vertebrae to be exaggerated, implying that the actual storlek of the animal was likely smaller.
Mosasaur bones have also been found with shark teeth embedded in them. Their limb bones were reduced in length and their paddles were formed by webbing between their long finger and toe bones. The smaller orsaka, such as Platecarpus and Dallasaurus , which were about 1—6 m 3. During the last 20 million years of the Cretaceous period Turonian — Maastrichtian ages , with the extinction of the ichthyosaurs and pliosaurs , mosasaurids became the dominant marine predators.
The smaller mosasaurs may have spent some time in fresh water, hunting for food. Mosasaurs had a body shape similar to that of modern-day monitor lizards varanids , but were more elongated and streamlined for swimming.
Mosasaurs: Overview, Size, Habitat, & Other Facts
Despite the many mosasaur remains collected worldwide, knowledge of the nature of their skin coverings remains in its early stages. The smallest-known mosasaur was Dallasaurus turneri , which was less than 1 m 3. In , collagen protein was recovered from a Prognathodon humerus dated to the Cretaceous. Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, shallow inland seas prevalent during the Late Cretaceous period.
A skeleton of Tylosaurus proriger from South Dakota included remains of the diving seabird Hesperornis , a marine bony fish , a possible shark , and another, smaller mosasaur Clidastes. In Harrana specimens, two types of scales were observed on a single specimen: keeled scales covering the upper regions of the body and smooth scales covering the lower. Several reddish areas in the fossil may represent the heart, lungs, and kidneys.
Holes have been funnen in fossil shells of some ammonites, mainly Pachydiscus and Placenticeras. However, new evidence suggests that many advanced mosasaurs had large, crescent-shaped flukes on the ends of their tails, similar to those of sharks and some ichthyosaurs. In , a case study bygd A. Virtually all forms were active predators of fish and ammonites; a few, such as Globidens , had blunt, spherical teeth, specialized for crushing mollusk shells.
The placement of the kidneys is farther forward in the abdomen than it is in monitor lizards, and is more similar to those of cetaceans. Mosasaurs from Latin Mosa meaning the ' Meuse ', and Greek σαύρος sauros meaning 'lizard' are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. As in cetaceans, the bronchi leading to the lungs run parallel to each other instead of splitting apart from one another as in monitors and other terrestrial reptiles.
They themselves became extinct as a result of the K-Pg event at the end of the Cretaceous period, about 66 million years ago. This lack may be due to the delicate nature of the scales, which nearly eliminates the possibility of preservation, in addition to the preservation sediment types and the marine conditions under which the preservation occurred. Larger mosasaurs were more typical, with many species growing longer than 4 m 13 ft.
Rather than use snake-like undulations, their bodies probably remained stiff to reduce drag through the water, while their tails provided strong propulsion. In mosasaurs, these features may be internal adaptations to fully marine lifestyles.