Halisaurus ("Ocean Lizard") is an extinct genus of marine lizard belonging to the mosasaur family. With a length of 3–4 m (10–13 ft), it was small compared to most other mosasaurs. It was named by Othniel Charles Marsh in 1869, but renamed Baptosaurus by Marsh in 1870, who thought the name was already in use (preoccupied) by a fish named Halosaurus. According to modern rules, a difference of a letter is enough and the substitute name is unneeded.

 Halisaurinae  is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates.

 Bardet et al. (2005, p. 464) diagnosed the Halsaurinae as all mosasaurs more closely related to Halisaurus than Moanasaurus. Unambiguous character states were listed as follows: "premaxilla-maxilla sutural contact vertical anteriorly, oblique at midpoint and horizontal posteriorly; contact plane between the parietal and the supratemporal oblique; preaxial ridge extending on two-thirds of the length of the radius; tibia and fibula long and slender with slightly expanded extremities. Ambiguous characters include "dorsal median ridge borne on the anterior two-thirds of the frontal; frontal with ventral boss; parietal foramen surrounded by a ventral boss; quadrate with large infrastapedial process; coalescent infra- and suprastapedial processes of quadrate; zygosphene-zygantrum complex absent; synapophyses of the cervical vertebrae extending ventrally to the ventral surface of the centrum; fused haemal spines."

 Designation of this subfamily followed many decades of confusion surrounding the type genus, Halisaurus, especially H. sternbergii, a species from the Mooreville Chalk Formation of Alabama and the Niobrara Chalk of Kansas. Originally, the species had been referred to the mosasaurine Clidastes, then to Halisaurus (Russell, 1967; p. 369 ), which was also considered a member of the Mosasaurinae at that time. Later workers  questioned the phylogenetic position and monophyly of Halisaurus, in part because of striking morphological differences between H. sternbergii and the other known species of the taxon. Finally, Bardet et al. (2004) determined that H. sternbergii was not conspecific with the other members of the genus and erected a new genus, Eonatator, as well a new subfamily, consisting of Eonatator and Halisaurus. Halisaurines (as members of this subfamily are collectively and informally known) were small to medium-sized mosasaurs averaging 4,5 - 6+ meters in length. Of all known mosasaurids, they were the least adapted to a marine lifestyle. Halisaurines are known from North America, Europe, South America, and Africa. The earliest known remains of halisaurines occur in rocks of Santonian age and the subfamily persists until the latest Maastrichtian. The etymology of this group derives from the genus Halisaurus (Greek halis = "sea" + Greek sauros = "lizard").

 Мозазавры (Mosasauridae) — вымершее семейство ящериц (Lacertilia). Близкие родственники современных варанов. Мозазавры были приспособлены к обитанию в водной среде: тело имело обтекаемую форму, а конечности были преобразованы в ласты. Существовали в меловом периоде. Останки обнаружены на всех континентах, включая Антарктиду.

 Предположительный предок мозазавров найден в отложениях нижнего мела Японии. В его качестве рассматривают мелкую водную ящерицу каганаиас (Kaganaias), обладавшую телом змеевидной формы и короткими конечностями.

 Длина мозазавров колеблется от 3 м до 17 м. Самые крупные представители мозазавридов — тилозавр (15—25 м), гайнозавр и мозазавр (оба до 17 м).

 Мозазавры заняли многие экологические ниши в морях мелового периода. Главным образом это были ниши хищников крупных и средних размеров. Но некоторые виды, как например глобиденс (Globidens), зубы которого были шаровидной, удобной для раскусывания раковин моллюсков формы, освоили ниши «моллюскоедов».

 Halisaurus arambourgi — вид, живший в конце мелового периода около 70-65 млн лет назад на территории современного Марокко.

 Mosasaurs (from Latin Mosa meaning the 'Meuse river', and Greek σαύρος sauros meaning 'lizard') are large, extinct, marine reptiles. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from semiaquatic squamates known as aigialosaurs, which were more similar in appearance to modern-day monitor lizards, in the Early Cretaceous. During the last 20 million years of the Cretaceous period (Turonian-Maastrichtian), with the extinction of the ichthyosaurs and decline of plesiosaurs, mosasaurs became the dominant marine predators.

 Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, shallow, epicontinental seas prevalent during the Late Cretaceous Period. Mosasaurs were so well adapted to this environment that they gave birth to live young, rather than return to the shore to lay eggs, as sea turtles do.

 The smallest-known mosasaur was Carinodens belgicus, which was about 3.0 metres (9.8 ft) to 3.5 metres (11 ft) long and probably lived in shallow waters near shore, cracking mollusks and sea urchins with its bulbous teeth. Larger mosasaurs were more typical: Hainosaurus holds the record for longest mosasaur, at 17.5 metres (57 ft).

 Mosasaurs had a body shape similar to that of modern-day monitor lizards (varanids), but were more elongated and streamlined for swimming. Their limb bones were reduced in length and their paddles were formed by webbing between their elongated digit-bones. Their tails were broad, and supplied the locomotive power. This method of locomotion may have been similar to that used by the conger eel or sea snakes today. However, more recent evidence suggests many advanced mosasaurs had large crescent-shaped flukes on the ends of their tails similar to those of sharks and ichthyosaurs. Rather than snake-like undulatory movement, their bodies probably remained stiff in these mosasaurs to improve hydrodynamic efficiency through the water, while the end of their tails provided strong propulsion. The animal may have lurked and pounced rapidly and powerfully on passing prey, rather than hunting for it. A juvenile Prognathodon found in Jordan's Harrana Site in 2008 and described in 2013 supports this, as the outline of its tail fluke was also preserved with the skeleton.

 Early reconstructions showed mosasaurs with dorsal crests running the length of their bodies, which were based on misidentified tracheal cartilage. When the error was discovered, depicting mosasaurs with such crests was already a trend.

 Mosasaurs had double-hinged jaws and flexible skulls (much like that of a snake), which enabled them to gulp down their prey almost whole, a snake-like habit which helped identify the unmasticated gut contents fossilized within mosasaur skeletons. 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). Mosasaur bones have also been found with shark teeth embedded in them.

 One of the food items of mosasaurs were ammonites, molluscs with shells similar to that of Nautilus, which were very abundant in the Cretaceous seas. On fossil shells of some ammonites (mainly Pachydiscus and Placenticeras) round holes were found, once interpreted as a result of limpets attaching themselves to the ammonites. The triangular formation of the holes, their size and shape, and their presence on both sides of the shells, corresponding to the upper and lower jaws, is evidence of the bite of medium-sized mosasaurs. It is not clear if this behaviour was common across all size classes of mosasaurs.

 Virtually all forms were active predators of fish and ammonites; a few, such as Globidens, had blunt spherical teeth, specialized to crush mollusk shells. The smaller genera, such as Platecarpus and Dallasaurus, which were about 1–6 m (10–20 ft) long, probably preyed on fish and other small prey. The smaller mosasaurs may have spent some time in fresh water, hunting for food. The larger mosasaurs, such as Tylosaurus, and Mosasaurus, reached sizes of 10–15 m (33–49 ft) long, and were the apex predators of the Late Cretaceous oceans, attacking other marine reptiles, in addition to preying on large fish and ammonites.

 Despite the relatively high number of mosasaur remains collected worldwide, knowledge of the nature of their skin coverings remains in its early stages. An incredibly small amount of mosasaurid specimens collected from around the world retain fossilized scale imprints; this lack of knowledge is possibly due to the delicate nature of the scales, which nearly eliminates possibility of preservation, in addition to the preservation sediments types and the marine conditions under which the preservation occurred. Until the discovery of several mosasaur specimens along with their remarkably well-preserved scale imprints from late Maastrichtian deposits of the Muwaqqar Chalk Marl Formation of Harrana in Jordan, knowledge of the nature 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-1075) from Gove County, Kansas. 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. Much like modern reptiles, regional variations existed in the type and size of the scales that covered the mosasaurs. In Harrana specimens, two types of scales were observed on a single specimen, keeled scales covering the upper regions of the body, as well as smooth scales covering the lower regions. As ambush predators, lurking and quickly capturing prey using stealth tactics, they are suggested to have benefited greatly from the nonreflective, keeled scales.

 More recently, a well-preserved fossil of Platecarpus tympaniticus has been found that preserved not only skin impressions, but also internal organs. Several reddish areas in the fossil may represent the heart, lungs, and  The trachea is also preserved, along with part of what may be the retina in the eye. 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. 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. In mosasaurs, these features may be internal adaptations to fully marine lifestyles.

 In 2011, collagen protein was recovered from a Prognathodon humerus dated to the Cretaceous.

 Color has been unknown in mosasaurs until 2014, when the findings of Johan Lindgren of Lund University et al. revealed the pigment melanin in the fossilized scales of a mosasaur. The studies of the scales revealed that mosasaurs were countershaded; with black backs and white underbellies much like a great white shark or leatherback sea turtle, the latter of which had fossilized ancestors also for which color was determined. The findings were described in the journal Nature.

 The first publicized discovery of a partial fossil mosasaur skull in 1764 by quarry workers in a subterranean gallery of a limestone quarry in Mount Saint Peter, near the Dutch city of Maastricht, preceded any major dinosaur fossil discoveries, but remained little known. However, a second find of a partial skull drew the Age of Enlightenment's attention to the existence of fossilized animals that were different from any known living creatures. When the specimen was discovered between 1770 and 1774, Johann Leonard Hoffmann, a surgeon and fossil collector, corresponded about it with the most influential scientists of his day, making the fossil famous. The original owner, though, was Godding, a canon of Maastricht cathedral.

 When the French revolutionary forces occupied Maastricht in 1794, the carefully hidden fossil was uncovered, after a reward, it is said, of 600 bottles of wine, and transported to Paris. After it had been earlier interpreted as a fish, a crocodile, and a sperm whale, the first to understand its lizard affinities was the Dutch scientist Adriaan Gilles Camper in 1799. In 1808, Georges Cuvier confirmed this conclusion, although le Grand Animal fossile de Maëstricht was not actually named Mosasaurus ('Meuse reptile') until 1822 and not given its full species name, Mosasaurus hoffmannii, until 1829. Several sets of mosasaur remains, that had been discovered earlier at Maastricht but were not identified as mosasaurs until the 19th century, have been on display in the Teylers Museum, Haarlem, procured from 1790.

 The Maastricht limestone beds were rendered so famous by the Mosasaur discovery, they have given their name to the final six-million-year epoch of the Cretaceous, the Maastrichtian.

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Tags: Вымершие рептилии, Мел, варанообразные, диапсиды, лепидозавроморфы, лепидозавры, мозазавриды, мозазавроиды, хализавры, чешуйчатые, ящерицы

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