Dinosaur of the Week III: Mosasaurus

Mosasaurus (/ˌmoʊzəˈsɔrəs/; "lizard of the Meuse River")

Is a genus of mosasaur, carnivorous, aquatic lizards, somewhat resembling flippered crocodiles, with elongated heavy jaws. The genus existed during the Maastrichtian age of the Cretaceous period (Mesozoicera), around 70–65 million years ago in the area of modern Western Europe and North America. The name means "Meuse lizard", as the first specimen was found near the Meuse River (Latin Mosa + Greek sauros lizard).

Description

Mosasaurus was among the last mosasaur genera, and among the largest. The skull was more robustly built than in other mosasaurs, as the mandibles articulated very tightly with the skull. It had a deep, barrel-shaped body, and with its fairly large eyes, poor binocular vision, and poorly developed olfactory bulbs, experts believe that Mosasaurus lived near the ocean surface, where it preyed on fish, turtles, ammonites, and possibly smaller mosasaurs. The animal remained near the surface and although it was able to dive, it evidentially did not venture into deeper waters.As with most mosasaurs, their legs and feet are modified into hydrofoil-like flippers, with the forelimbs larger than the hindlimbs. Mosasaurusreached lengths of about 18 meters, somewhat longer than its American relatives Tylosaurus andHainosaurus. However, Mosasaurus was more robust than the somewhat smaller sizedtylosaurine mosasaurs.

The skull of Mosasaurus tapered off into a short, conical process, and the jaws were armed with massive, sharp, conical teeth. Their paddle-like limbs had five digits in front and four in back. The trunk terminated in a strong tail which, together with serpentine undulation of the whole body, contributed far more to the animal's locomotion than did the limbs.

History of discovery

First discoveries

At some time between 1770 and 1774 ("1770" according to Faujas de Saint-Fond, "about the year 1770" according to Camper and "en 1780" according to Cuvier in 1808^[7]) a second partial skull was discovered and procured. It was found in the ground owned by canon Theodorus Joannes Godding, and the latter one displayed it in his country house on the slope of the hill. A local retired German/Dutch army physician, Johann Leonard Hoffmann (1710-1782), also collected some fragments and corresponded about the skull with the Dutch Professor Petrus Camper. Hoffmann presumed the animal was a crocodile. In 1786 however, Camper disagreed and concluded the remains were those of "an unknown toothed whale".^[8]Mosasaurus was the first genus of mosasaur (and in fact, the first genus of any prehistoric reptile) to be named. The first remains known to science were a fragmentary skull from a chalk quarry in the St Pietersberg, a hill near Maastricht,Netherlands, found in 1764 and collected by lieutenant Jean Baptiste Drouin in 1766. It was procured for the Teylers Museum at Haarlem in 1784 by Martinus van Marum, the first director of the museum, who published its description only in 1790. He considered it to be a species of "big breathing fish" (Pisces cetacei, in other words: a whale). It is still part of the collection as TM 7424.

Maastricht, an important fortress city, was captured by the French revolutionary armies by the end of 1794. Accompanying the French troops, although arriving in Maastricht two months after the city had been taken, was geologist Barthélemy Faujas de Saint-Fond on a mission to secure the piece, together with représentant du peuple (political commissar) Augustin-Lucie de Frécine (1751–1804), who during the campaign tried to transport anything of artistic or scientific value he could lay his hands on to France. Finding that it had been removed from the cottage and hidden within the fortress, Frécine offered "six hundred bottles of excellent wine" to those being the first to locate the skull and bring it to him in one piece. Soon a dozen grenadiers claimed their reward, carrying the piece with them.December 1794 it was moved to Paris as war booty, by decree declared a national heritage and added to the collection of the newMuséum national d'Histoire naturelle.

Identification as an extinct reptile

In 1798 Faujas de Saint-Fond published his Histoire naturelle de la montagne de Saint-Pierre de Maestricht [Tome 1], which also contained an account of the circumstances of the find. According to him, Dr. Hoffmann paid the quarrymen to inform him of any fossil finds. When the skull was found in 1770 Hoffmann would have been warned by the quarrymen and he is said to have lead the excavation from then on. Afterwards, Godding would have claimed his rights as landowner and forced Hoffmann to relinquish his ownership through a lawsuit, won by influencing the court. De Saint-Fond, after all, in 1795, saved the specimen for science, promising a considerable indemnity to Godding to compensate for his loss. However, as Dutch historian Peggy Rompen has illustrated, very little of this famous story can be substantiated by other sources. Godding was the original owner, Hoffmann clearly never possessed the fossil, there was no lawsuit, Faujas de Saint-Fond probably never paid anything, and the entire account seems to have been fabricated by him to justify the dispossession by military force.

In 1808 Cuvier confirmed Camper's result. The fossil had already become part of Cuvier's first speculations on the possibility of animal species going extinct. The idea of extinction paved the way for his theory of catastrophism or "consecutive creations", one of the predecessors of the evolution theory. Prior to this, almost all fossil reptile specimens, when recognized as having come from one-living animals, were interpreted as forms similar to those of the modern day: crocodiles, fish, whales, or large land mammals. Cuvier's idea that the Maastricht specimen was a gigantic version of a modern animal unlike any species alive today seemed strange, even to him. He justified this by trusting his techniques in the then-developing field of comparative anatomy, which he had already used to identify giant, extinct members of other modern groups known only from fossils, including giant tapir andground sloth specimens. De Saint-Fond still assumed the specimen represented a crocodile. In 1798 the son of Petrus Camper, Adriaan Gilles Camper, again studied the fossil indirectly by reconsidering the description by his father. He was the first to reach the conclusion that the remains were those of a giant monitor, which result in 1799 he corresponded to Georges Cuvier.

In 1854 German biologist Hermann Schlegel was the first to conjecture Mosasaurus had flippers instead of normal feet.A scientific name had not yet been given to the new species, the specimen usually being referred to as the Grand Animal fossile des Carrières de Maëstricht or "Great Fossil Animal of the Maastricht quarries". In 1822 William Daniel Conybeare named it Mosasaurus after the Latin name (Mosa) of the Maas (Meuse) River passing along Mount Saint Peter, the second skull being the holotype, MNHNP AC9648. The specific name (epithet) hoffmannii was added by Gideon Mantell in 1829, honouring Hoffmann, on the presumption he was the discoverer of the type specimen. The emendated form hoffmanni often used today, is contrary to the rules of the ICZN that state "the original spelling of a name is to be preserved."

In 1998, another, even bigger and more intact fossil skull was found in the Maastricht limestone quarries. Shortly after, it was nicknamed "Bèr", and put on display in the Maastricht Natural History Museum. This specimen was then identified as a Prognathodon, and received the species name Prognathodon saturator.

On September 19, 2012, it was announced that nine days earlier, again a skeleton of what appears to be a Mosasaur was found in the limestone quarry just outside Maastricht, the same quarry that yielded the type specimen of Mosasaurus hoffmannii. Carlo Brauer, an excavator operator at the ENCI quarry, discovered the teeth of the fossil in the shovel of his digger on Monday morning, September 10. In the days following the discovery, museum staff retrieved several large sections of the skull and part of the body and tail of the approximately 13-metre long skeleton. Based on stratigraphy, the age of the specimen was estimated at 67.83 million years, making it about one-and-a-half million years older than "Bèr". From what has been uncovered, this appears to be the oldest known specimen ofMosasaurus hoffmannii or a closely related species. The specimen is nicknamed Carlo, after the ENCI worker who discovered it.

Classification and species

Other named, but invalid or dubious species include:The family Mosasauridae is split into several subfamilies, with Mosasaurus being placed within Mosasaurinae. This subfamily, in turn, is further split into smaller tribes, withMosasaurus being grouped with Clidastes, Moanasaurus, and Liodon in the tribeMosasaurini.

Since the genus was first named in the early 19th century, numerous species have been assigned to Mosasaurus. However, only four are currently recognized as valid by most researchers: M. hoffmannii Mantell 1829 (the type species), M. lemonnieri Dollo 1889, M. missouriensis (Harlan 1834), and M. beaugei Armbourg 1952.

• M. copeanus Marsh 1869
• M. crassidens Marsh 1870
• M. dekayi Bronn 1838
• M. giganteus (Somering 1916)
• M. gracilis Owen 1851
• M. hardenponti
• M. hobetsuensis Suzuki 1985
• M. iguanavus (Cope 1868)
• M. johnsoni (Mehl 1930)
• M. lonzeensis Dollo 1904
• M. lundgreni (Schroder 1885)
• M. meirsii Marsh 1869
• M. mokoroa Welles & Gregg 1971
• M. neovidii von Meyer 1845
• M. poultneyi Martin 1953
• M. prismaticus Sakuai Chitoku & Shibuya 1999
• M. scanicus Schroder 1885

References

http://en.wikipedia.org/wiki/Mosasaurus

Dinosaur of the Week II: Quetzalcoatlus

Quetzalcoatlus /kɛtsəlkoʊˈætləs/ 

was a pterodactyloid pterosaur known from theLate Cretaceous of North America (Maastrichtian stage) and one of the largest known flying animals of all time. It was a member of the Azhdarchidae, a family of advanced toothless pterosaurs with unusually long, stiffened necks. Its name comes from theMesoamerican feathered serpent god Quetzalcoatl.

Description

Skull material (from the unnamed smaller species) shows that Quetzalcoatlus had a very sharp and pointed beak, contrary to some earlier reconstructions that showed a blunter snout, based on the inadvertent inclusion of jaw material from another pterosaur species, possibly a tapejarid or a form related to Tupuxuara. A skull crest was present but its exact form and size are still unknown.

Size comparison of Q. northropi (green), the unnamed smaller species (blue), and a human

Size

When it was first discovered, scientists estimated that the largest Quetzalcoatlusfossils came from an individual with a wingspan as large as 15.9 meters (52.2 feet), choosing the middle of three extrapolations from the proportions of other pterosaurs that gave an estimate of 11, 15.5 and 21 meters respectively (36 feet, 50.85 feet, 68.9 feet). In 1981, further study lowered these estimates to 11–12 meters (36–39 feet). More recent estimates based on greater knowledge of azhdarchid proportions place its wingspan at 10–11 meters (33–36 ft).

Mass estimates for giant azhdarchids are extremely problematic because no existing species share a similar size or body plan, and in consequence published results vary widely.^[4] While some studies have historically found extremely low weight estimates forQuetzalcoatlus, as low as 70 kilograms (150 lb) for a 10-meter (33 ft) individual, a majority of estimates published since the 2000s have been higher, around 200–250 kilograms (440–550 lb).

Paleobiology

Quetzalcoatlus was abundant in Texas during the Lancian in a fauna dominated by Alamosaurus.The Alamosaurus-Quetzalcoatlusassociation probably represents semi-arid inland plains.Quetzalcoatlus had precursors in North America and its apparent rise to widespreadness may represent the expansion of its preferred habitat rather than an immigration event, as some experts have suggested.

Feeding

There have been a number of different ideas proposed about the lifestyle of Quetzalcoatlus. Because the area of the fossil site was four hundred kilometers removed from the coastline and there were no indications of large rivers or deep lakes nearby at the end of the Cretaceous, Lawson in 1975 rejected a fish-eating lifestyle, instead suggesting thatQuetzalcoatlus scavenged like the Marabou Stork, but then on the carcasses of titanosaursauropods such as Alamosaurus. Lawson had found the remains of the giant pterosaur while searching for the bones of this dinosaur, which formed an important part of its ecosystem.

In 1996, Thomas Lehman and Langston rejected the scavenging hypothesis, pointing out that the lower jaw bent so strongly downwards that even when it closed completely a gap of over five centimeters remained between it and the upper jaw, very different from the hooked beaks of specialized scavenging birds. They suggested that with its long neck vertebrae and long toothless jaws Quetzalcoatlus fed like modern-day skimmers, catching fish during flight while cleaving the waves with its beak.While this skim-feeding view became widely accepted, it was not subjected to scientific research until 2007 when a study showed that for such large pterosaurs it was not a viable method because the energy costs would be too high due to excessive drag. In 2008 pterosaur workers Mark Paul Witton and Darren Naish published an examination of possible feeding habits and ecology of azhdarchids. Witton and Naish noted that most azhdarchid remains are found in inland deposits far from seas or other large bodies of water required for skimming. Additionally, the beak, jaw, and neck anatomy are unlike those of any known skimming animal. Rather, they concluded that azhdarchids were more likely terrestrial stalkers, similar to modern storks, and probably hunted small vertebrates on land or in small streams. Though Quetzalcoatlus, like other pterosaurs, was a quadruped when on the ground, Quetzalcoatlus and other azhdarchids have fore and hind limb proportions more similar to modern running ungulate mammals than to their smaller cousins, implying that they were uniquely suited to a terrestrial lifestyle.

Flight

The nature of flight in Quetzalcoatlus and other giant azhdarchids was poorly understood until serious biomechanical studies were conducted in the 21st century. One early (1984) experiment by Paul MacCready used practical aerodynamics to test the flight ofQuetzalcoatlus. MacCready constructed a model flying machine or ornithopter with a simple computer functioning as an autopilot. The model successfully flew with a combination of soaring and wing flapping; however, the model was half scale based on a then-current weight estimate of around 80 kg, far lower than more modern estimates of over 200 kg.The method of flight in these pterosaurs depends largely on weight, which has been controversial, and widely differing masses have been favored by different scientists. Some researchers have suggested that these animals employed slow, soaring flight, while others have concluded that their flight was fast and dynamic. In 2010, Donald Henderson argued that the mass of Q. northropi had been underestimated, even the highest estimates, and that it was too massive to have achieved powered flight. Henderson argued that it may have been flightless.

However, most other flight capability estimates have disagreed with Henderson's research, suggesting instead an animal superbly adapted to long-range, extended flight. In 2010, Mike Habib, a professor of biomechanics at Chatham University, and Mark Witton, a British paleontologist, undertook a further investigation into the claims of flightlessness in large pterosaurs.After factoring wingspan, body weight, and aerodynamics, a sophisticated computer program led the two researchers to conclude that Q. northropi was capable of flight "up to 80 miles an hour for 7 to 10 days at altitudes of 15,000 feet". Mike Habib further suggested a maximum flight range of 8,000 to 12,000 miles for Q. northropi. Henderson's work was further criticized by Habib, who pointed out that although Henderson used excellent mass estimations, they were based on outdated pterosaur models, and that anatomical study of Q. northropi and other large pterosaur forelimbs show a higher degree of robustness than would be expected if they were purely quadrupedal. Habib believes that large pterosaurs most likely utilized a short burst of powered flight in order to then transition to thermal soaring.

Cultural significance

Imagine that dinosaur with us today!

Quetzalcoatlus has been featured in documentaries, both in cinemas and on television, since the 1980s. The Smithsonian project to build a working model of Q. northropi was the subject of the 1986 IMAX documentary On the Wing, shown at the National Air and space museum in Washington, D.C.. It has also been featured in television programs such as the BBC's Walking with Dinosaurs in 1999 and Dangerous, Ltd.'s Clash of the Dinosaurs in 2009. The later program featured traits invented by the producers to heighten entertainment value, including a depiction of Quetzalcoatlus with the ability to use ultraviolet vision to locate dinosaur urine when hunting in the air.It was also depicted in the 2011 documentary March of the Dinosaurs, where it was erroneously depicted as a clawless, bipedal scavenger, and in the 2009 series Animal Armageddon, where it was correctly portrayed with pycnofibres. In the "Return to Jurassic Park" bonus feature of the 2011 Blu-ray release of the Jurassic Park film series, John R. Horner describes Quetzalcoatlus as the pterosaur that most accurately represented and matched the size of the pterosaurs that are featured in the films.

In June 2010, several life-sized models of Q. northropi were put on display on London's South Bank as the centerpiece exhibit for theRoyal Society’s 350th anniversary exhibition. The models, which included both flying and standing individuals with wingspans of 30 feet (9.1 m), were intended to help build interest in science among the public. The models were created by scientists from the University of Portsmouth, including David Martill, Bob Loveridge and Mark Witton, and engineers Bob and Jack Rushton from Griffon Hoverwork. The display presented to the public the most accurate pterosaur models constructed at the time, taking into account anatomical and footprint evidence based on skeletal and trace fossils from related pterosaurs.

In 1985, the U.S. Defense Advanced Research Projects Agency (DARPA) and AeroVironment used Quetzalcoatlus northropi as the basis for an experimental ornithopter UAV. They produced a half-scale model weighing 40 pounds (18 kg), with a wingspan of 18 feet (5.5 m). Coincidentally, Douglas A. Lawson, who discovered Q. northropi in Texas in 1971, named it for John "Jack" Northrop, a famous developer of tailless flying wing aircraft in the 1940s. The replica of Q. northropi incorporates a "flight control system/autopilot which processes pilot commands and sensor inputs, implements several feedback loops, and delivers command signals to its various servo-actuators." It is on exhibit at the National Air and Space Museum.

References

http://en.wikipedia.org/wiki/Quetzalcoatlus
http://carnivoraforum.com/topic/9331095/1/

Dinosaur of the Week: Spinosaurus

Spinosaurus (meaning "spine lizard"):

Is a genus of theropod dinosaur which lived in what is now North Africa, from the lower Albian to lower Cenomanian stages of the Cretaceous period, about 112 to 97 million years ago. This genus was first known from Egyptian remains discovered in 1912 and described by German paleontologist Ernst Stromer in 1915. The original remains were destroyed in World War II, but additional material has come to light in recent years. It is unclear whether one or two species are represented in the fossils reported in the scientific literature. The best known species is S. aegyptiacus from Egypt, although a potential second species S. maroccanus has been recovered from Morocco.

Spinosaurus may be the largest of all known carnivorous dinosaurs, even larger than Tyrannosaurus and Giganotosaurus. Estimates published in 2005 and 2007 suggest that it was 12.6 to 18 metres (41 to 59 ft) in length and 7 to 20.9 tonnes (7.7 to 23.0 short tons) in weight. The skull of Spinosaurus was long and narrow like that of a modern crocodilian. Spinosaurus is known to have eaten fish; evidence suggests that it lived both on land and in water like a modern crocodilian. The distinctive spines of Spinosaurus, which were long extensions of the vertebrae, grew to at least 1.65 meters (5.4 ft) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that the spines were covered in fat and formed a hump. Multiple functions have been put forward for this structure, including thermoregulation and display.

Size comparison of selected giant theropod dinosaurs, Spinosaurus (S. aegyptiacus) in red.

Description

Spinosaurus is known for its neural spines, its large size, and its elongated skull.

Paleobiology

Function of neural spines

The function of the dinosaur's sail or hump is uncertain; scientists have proposed severalhypotheses including heat regulation and display. In addition, such a prominent feature on its back could also make it appear even larger than it was, intimidating other animals.

The structure may have been used for thermoregulation. If the structure contained abundant blood vessels, the animal could have used the sail's large surface area to absorb heat. This would imply that the animal was only partly warm-blooded at best and lived in climates where nighttime temperatures were cool or low and the sky usually not cloudy. It is thought that Spinosaurus and Ouranosaurus both lived in or at the margins of an earlier version of theSahara Desert, which could explain this. It is also possible that the structure was used to radiate excess heat from the body, rather than to collect it. Large animals, due to the relatively small ratio of surface area of their body compared to the overall volume (Haldane's principle), face far greater problems of dissipating excess heat at higher temperatures than gaining it at lower. Sails of large dinosaurs added considerably to the skin area of their bodies, with minimum increase of volume. Furthermore, if the sail was turned away from the sun, or positioned at a 90 degree angle towards a cooling wind, the animal would quite effectively cool itself in the warm climate of Cretaceous Africa. However, Bailey (1997) was of the opinion that a sail could have absorbed more heat than it radiated. Bailey proposed instead that Spinosaurus and other dinosaurs with long neural spines had fatty humps on their backs for energy storage, insulation, and shielding from heat.

Elaborate body structures of many modern-day animals usually serve to attract members of the opposite sex during mating. It is quite possible that the sails or humps of these dinosaurs were used for courtship, in a way similar to a peacock's tail. Stromer speculated that males and females may have differed in the size of the neural spine.

Finally, it is quite possible that the sail or hump combined these functions, acting normally as a heat regulator, becoming a courting aid during the mating season, being used to cool itself and, on occasions, turning into an intimidating device when an animal was feeling threatened.

Posture

Although traditionally depicted as a biped, it has been suggested since the mid-1970s thatSpinosaurus was at least an occasional quadruped. This has been bolstered by the discovery of Baryonyx, a relative with robust arms. Because of the mass of the hypothesized fatty dorsal humps of Spinosaurus, Bailey (1997) was open to the possibility of a quadrupedal posture, leading to new restorations of it as such. The hypothesis thatSpinosaurus had a typical quadrupedal gait has fallen out of favor, though spinosaurids may have crouched in a quadrupedal posture. Theropods, including spinosaurids, could not pronate their hands (rotate the forearm so the palm faced the ground), but a resting position on the side of the hand was possible, as shown by fossil prints from an Early Jurassic theropod.

Feeding

Spinosaurus is thought to have survived primarily on fish and scientists believe its eating habits resembled that of modern-day crocodiles. There is evidence that it lived on both land and sea.

The only direct substantiation that Spinosaurus ate fish was a juvenile discovered with fish scales and bones in its stomach. There is also evidence that it preyed on other small herbivore dinosaurs and scavenged.

Spinosaurus lived in Egypt and Morocco. There is speculation that the Sahara is rich withSpinosaurus fossils, but the harsh environment makes them difficult to unearth.

In popular culture

Spinosaurus appeared in the 2001 film Jurassic Park III, it replaced ''Tyrannosaurus'' as the main antagonist.The film's consulting paleontologist John R. Horner was quoted as saying: "If we base the ferocious factor on the length of the animal, there was nothing that ever lived on this planet that could match this creature [Spinosaurus]. Also my hypothesis is that T-rex was actually a scavenger rather than a killer. Spinosaurus was really the predatory animal." In the film, Spinosaurus was portrayed as larger and more powerful thanTyrannosaurus: in a scene depicting a battle between the two resurrected predators, Spinosaurus emerges victorious by snapping the tyrannosaur's neck.

Spinosaurus has long been depicted in popular books about dinosaurs, although only recently has there been enough information about spinosaurids for an accurate depiction. After an influential 1955 skeletal reconstruction by Lapparent and Lavocat based on a 1936 diagram by Stromer, it has been treated as a generalized upright theropod, with a skull similar to that of other large theropods and a sail on its back, even having four-fingered hands.

In addition to films, action figures, video games, and books, Spinosaurus has been depicted on postage stamps such as ones fromAngola, The Gambia, and Tanzania.

The creature has also appeared in documentaries such as Bizarre Dinosaurs, Monsters Resurrected and Planet Dinosaur.

References

http://en.wikipedia.org/wiki/Spinosaurus

http://www.livescience.com/24120-spinosaurus.html