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How Much Money Do Paleontologists Make?

Wednesday, December 7, 2016

Young paleontologist

Paleontologists study fossils found in geological formations to determine the ages of plants, micro-organisms, animals and ancient civilizations. Dating of fossils is derived from the ages of rock layers above and below the fossils in a process called radiometric dating, according to the University of California Berkeley. While many paleontologists work in museums and college research labs, some help recover fossils in the coal and oil industries. Paleontologists earn salaries averaging over $100,000 annually.

Salary and Qualifications

The U.S. Bureau of Labor Statistics categorizes paleontologists as geoscientists, which also includes geologists, geochemists and seismologists. They earned average annual salaries of $106,780 as of May 2012, according to the BLS. The top 25 percent made over $130,330 annually. Most paleontologists have master’s or Ph.D. degrees in paleontology. Doctorate degrees are usually necessary for high-level research and professors’ jobs at colleges and universities. To succeed in their field, paleontologists must be knowledgeable about many different sciences, including biology, chemistry, geology and physics. Other essential requirements include math, critical-thinking, problem-solving, interpersonal, speaking, writing and computer skills.

Salary by State

A paleontologist’s salary can vary considerably by state. They earned the highest annual salaries of $153,120 in Oklahoma in 2012, according to the BLS. They also earned relatively high salaries in Texas and Washington, D.C., at $146,800 and $128,040 per year, respectively. Paleontologists who worked in Alaska earned $111,670 annually, while those in Colorado earned salaries closer to the national average at $106,030. Those in California and Pennsylvania earned lower salaries of $95,670 and $67,300, respectively.

Salary by Industry

Besides experience and geographic area, the industry in which paleontologists work also dictates their earnings. They earned the highest salaries of $155,830 per year in the petroleum and coal products manufacturing industry, according to the BLS, and the second and third highest salaries in oil and gas extraction and mining support activities — $149,750 and $140,520. Those who worked for federal and state government agencies made $96,820 and $64,970 per year, respectively. Moreover, paleontologist who teach at universities earn $40,000 to $60,000 for nine months of work, according to The Paleontological Society.

Job Outlook

The BLS indicates that jobs for geoscientists, including paleontologists, will increase 21 percent in the next decade, which is faster than the 14 percent growth rate for all jobs. Many job opportunities for paleontologists will be spurred by the demand for responsible land and resource management. A large number of geoscientists and paleontologists are also expected to retire within the next 10 years, which should produce jobs for new entrants in the field.

Source: www.NateGeo.com

Triceratops

Wednesday, December 7, 2016

Triceratops in the forest by Swordlord3d

Triceratops is a genus of herbivorous ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the late Cretaceous period, about 68 million years ago (mya) in what is now North America. It is one of the last known non-avian dinosaur genera, and became extinct in the Cretaceous–Paleogene extinction event 66 million years ago. The term Triceratops, which literally means “three-horned face”, is derived from the Greek τρί- (tri-) meaning “three”, κέρας (kéras) meaning “horn”, and ὤψ (ops) meaning “face”.

Size of T. prorsus (orange) and T. horridus (green) compared to a human. Author: Matthew Martyniuk

Triceratops is one of the best known of all dinosaurs and was the largest of the ceratopsians. Its massive head bore a short frill of solid bone along with the three large horns for which it is named-one above each eye and a smaller one on the snout. Traces of blood vessels found in the frill and horn have suggested to some paleontologists that the frill may have served as a means of regulating the animal’s body temperature. As with other ceratopsians, the frill would have been covered with skin and may also have been used during courtship display.

The first named specimen now attributed to Triceratops is a pair of brow horns attached to a skull roof, found near Denver, Colorado in the spring of 1887. This specimen was sent to Othniel Charles Marsh, who believed that the formation from which it came dated from the Pliocene, and that the bones belonged to a particularly large and unusual bison, which he named Bison alticornis. He realized that there were horned dinosaurs by the next year, which saw his publication of the genus Ceratops from fragmentary remains, but he still believed B. alticornis to be a Pliocene mammal. It took a third and much more complete skull to change his mind. The specimen, collected in 1888 by John Bell Hatcher from the Lance Formation of Wyoming, was initially described as another species of Ceratops. After reflection, Marsh changed his mind and gave it the generic name Triceratops, accepting his Bison alticornis as another species of Ceratops (it would later be added to Triceratops). The sturdy nature of the animal’s skull has ensured that many examples have been preserved as fossils, allowing variations between species and individuals to be studied. Triceratops remains have subsequently been found in the American states of Montana and South Dakota (in addition to Colorado and Wyoming), and in the provinces of Saskatchewan and Alberta, Canada.

An earlier specimen, also recovered from the Lance Formation, was named Agathaumas sylvestris by Edward Drinker Cope in 1872. Originally identified as a hadrosaur, this specimen consists only of post-cranial remains and is only provisionally considered an example of Triceratops.

T.rex vs Triceratops by Swordlord3d

Triceratops is the best known genus of the Ceratopsidae, a family of large North American horned dinosaurs. The exact location of Triceratops among the ceratopsians has been debated over the years. Confusion stemmed mainly from the combination of short, solid frills (similar to that of Centrosaurinae), and the long brow horns (more akin to Ceratopsinae, also known as Chasmosaurinae). In the first overview of horned dinosaurs, R. S. Lull hypothesized two lineages, one of Monoclonius and Centrosaurus leading to Triceratops, the other with Ceratops and Torosaurus, making Triceratops a centrosaurine as the group is understood today. Later revisions supported this view, formally describing the first, short-frilled group as Centrosaurinae (including Triceratops), and the second, long-frilled group as Chasmosaurinae.

Skull growth series: A display of Triceratops horridus skulls, from baby to adult, at the Museum of the Rockies in Bozeman, Montana. Dinosaurs are classified into four growth stages: baby, juvenile, subadult, and adult. The skull to the far right is a baby, collected in Garfield County, Montana. (This is a cast.) The second and third skulls from the right are juveniles, one larger than the other. (The one second from the right was found in Garfield County, Montana. The one third from the right was found in McCone County, Montana.) Note the triangular frill nodules (not yet fused with the frill), the backward-curving horns, the longer snouts, and the lack of holes in the frill. The fourth from the right is a subadult (teenager). Although the horns still curve backward, the frill nodules are fusing with the frill and the snout is showing large “excavation” (areas of no bone). The final skull on the far left is an adult. All of these skulls were collected in Montana. Author: Tim Evanson

In 1949, C. M. Sternberg was the first to question this and favoured instead that Triceratops was more closely related to Arrhinoceratops and Chasmosaurus based on skull and horn features, making Triceratops a ceratopsine (chasmosaurine of his usage) genus. He was largely ignored, with John Ostrom, and later David Norman both placing Triceratops within Centrosaurinae.

Subsequent discoveries and analyses upheld Sternberg’s view on the position of Triceratops, with Lehman defining both subfamilies in 1990 and diagnosing Triceratops as ceratopsine (chasmosaurine of his usage) on the basis of several morphological features. In fact, it fits well into the ceratopsine subfamily, apart from its one feature of a shortened frill. Further research by Peter Dodson, including a 1990 cladistic analysis and a 1993 study using RFTRA (resistant-fit theta-rho analysis), a morphometric technique which systematically measures similarities in skull shape, reinforces Triceratops’ placement in the ceratopsine subfamily.

Reconstruction of a Triceratops skeleton in the Senckenberg Museum in Frankfurt am Main, assembled from fragments of different skeletons

Valid species

  • T. horridus (Marsh, 1889) (originally Ceratops) (type species)

  • T. prorsus (Marsh, 1890)

Synonyms and doubtful species

The following species are considered nomina dubia (“dubious names”), and are based on remains that are too poor or incomplete to be distinguished from pre-existing Triceratops species.

  • T. albertensis (C. M. Sternberg, 1949)

  • T. alticornis (Marsh, 1887 [originally Bison])

  • T. brevicornus (Hatcher, 1905) (=T. prorsus)

  • T. calicornis (Marsh, 1898) (=T. horridus)

  • T. elatus (Marsh, 1891) (=T. horridus)

  • T. eurycephalus (Schlaikjer, 1935)

  • T. flabellatus (Marsh, 1889) (=T. horridus)

  • T. galeus (Marsh, 1889)

  • T. hatcheri (Lull, 1907) (contentious; see Nedoceratops below)

  • T. ingens (Lull, 1915)

  • T. maximus (Brown, 1933)

  • T. mortuarius (Cope, 1874) (nomen dubium; originally Polyonax mortuarius)

  • T. obtusus (Marsh, 1898) (=T. horridus)

  • T. serratus (Marsh, 1890) (=T. horridus)

  • T. sulcatus (Marsh, 1890)

  • T. sylvestris (Cope, 1872) (nomen dubium; originally Agathaumas sylvestris)

The skull (AMNH 5116) of this T. horridus composite specimen was formerly assigned to T. elatus. Author: Michael Gray

Triceratops were herbivorous, and because of their low head, their primary food was probably low growth, although they may have been able to knock down taller plants with their horns, beak, and bulk. The jaws were tipped with a deep, narrow beak, believed to have been better at grasping and plucking than biting.

Triceratops teeth were arranged in groups called batteries, of 36 to 40 tooth columns, in each side of each jaw with 3 to 5 stacked teeth per column, depending on the size of the animal. This gives a range of 432 to 800 teeth, of which only a fraction were in use at any given time (tooth replacement was continuous and occurred throughout the life of the animal). They functioned by shearing in a vertical to near-vertical orientation. The great size and numerous teeth of Triceratops suggests that they ate large volumes of fibrous plant material, with some suggesting palms and cycads, and others suggesting ferns, which then grew in prairies.

Riojasaurus

Wednesday, December 7, 2016

Riojasaurus

Riojasaurus (meaning “Rioja lizard”) was a herbivorous sauropodomorph dinosaur named after La Rioja Province in Argentina where it was found by José Bonaparte. It lived during the Late Triassic and grew to about 10 metres (33 ft) long. Riojasaurus is the only known riojasaurid to live in South America.

Riojasaurus incertus by Teratophoneus

Riojasaurus had a heavy body, bulky legs, and a long neck and tail. Its leg bones were dense and massive for an early sauropodomorph. By contrast, its vertebrae were lightened by hollow cavities, and unlike most early sauropodomorphs, Riojasaurus had four sacral vertebrae instead of three. It has been thought it probably moved slowly on all fours and was unable to rear up on its back legs. The nearly equal length of the fore and hindlimbs has also been interpreted as suggestive of an obligatorily quadrupedal gait. However, in 2016, Scott Hartman found the hand anatomy, relatively straight back and largely immobile shoulder girdle of Riojasaurus supported it being a biped.

Riojasaurus skull cast, Copenhagen. Author: FunkMonk

No skull was found with the first skeleton of Riojasaurus, although a well-preserved skull attributed to Riojasaurus was found later. The teeth of Riojasaurus were leaf shaped and serrated. The upper jaw contained 5 teeth at the front, with 24 more behind them in a row that ended under the eyes.

Comparisons between the scleral rings of Riojasaurus and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day at short intervals.

Qantassaurus

Wednesday, December 7, 2016

Qantassaurus and Timimus flee by 2195razielim

Qantassaurus is a genus of two-legged, plant-eating ornithischian dinosaur that lived in Australia about 115 million years ago, when the continent was still partly south of the Antarctic Circle. It was described by Patricia Vickers-Rich and her husband Tom Rich in 1999 after a find near Inverloch, and named after Qantas, the Australian airline.

Qantassaurus was discovered on 27 February 1996, during the third annual field season of the Dinosaur Dreaming project, a dig jointly run by Monash University and the National Museum of Victoria. The dig occurs on the beach of the Bunurong Marine Park at the intertidal site known as Flat Rocks, near Inverloch, in southeastern Victoria, Australia. The rock outcrops at this site are part of the Wonthaggi Formation of the Strzelecki Group, which during the Aptian stage were deposited in floodplains with braided river channels.

Mounted skeleton of Quantassaurus intrepidus at the Australian Museum, Sydney. Author: Matt Martyniuk (Dinoguy2)

Qantassaurus was probably about 1.8 meters (6 feet) long, and about one meter (3 feet) high. If it resembled its relatives, it had short thighs and long shins, and probably was a fast runner. Its feet had claws for traction, and a long tail probably helped with turning, stiffened by ossified tendons. One characteristic of the “Polar Victorian” euornithopods are distinctive spurs, or trochanters, on the upper surface of the thigh bone (or femur), where muscle was attached.

Qantassaurus is only known from jaw fragments. These are foreshortened compared to related species so its face was probably short and stubby. It had ten teeth in each lower jaw. It probably had a beak, and possessed leaf-shaped teeth back in its cheek, which were shed as they wore down, and replaced by new teeth growing up from the jaw. The teeth had eight distinctive vertical ridges on the outer side with a single larger primary ridge in the centre.

Qantassaurus lived 115 million years ago in Australia, during the late Aptian/early Albian age of the early Cretaceous period. At the time, Australia was part of the supercontinent of Gondwana, and partly within the Antarctic Circle, although the significance of polar conditions during the warm Cretaceous were greatly different from conditions in this region today. The average temperature of the region is contentious, with estimates ranging from -6 to well over 5 °C (21 to 37 °F). Conditions were likely to be at their coldest during the polar nights, which lasted up to three months.

Qantassaurus is a basal euornithopod or ornithopod that was originally assigned to the Hypsilophodontidae. Today this is understood to be an unnatural (paraphyletic) group.

In this regard, it is one of four species once considered hypsilophodontids from southeast Australia, along with Leaellynasaura amicagraphicaAtlascopcosaurus loadsi, and Fulgurotherium australe. The four taxa are mostly known from isolated bones and teeth; however the thigh bones of F. australe are very diverse and may belong to three genera.

Psittacosaurus

Wednesday, December 7, 2016

Psittacosaurus, a ceratopsian from the early Cretaceous

Psittacosaurus (“parrot lizard”) is a genus of extinct ceratopsian dinosaur from the Early Cretaceous of what is now Asia, existing between 126 and 101 million years ago. It is notable for being the most species-rich dinosaur genus. Up to 11 species are known, from across Mongolia, Siberia, China, and possibly Thailand. The species of Psittacosaurus were obligate bipeds at adulthood, with a high skull and a robust beak. One individual was found preserved with long filaments on the tail, similar to those of Tianyulong, and scales across the rest of the animal. Psittacosaurus probably had complex behaviours, based on the proportions and relative size of the brain. It may have been active for short periods of time during the day and night, and had well-developed senses of smell and vision.

 

Size comparison of P. mongoliensis to a human. Each grid segment represents one square metre. Author: Dinoguy2

Psittacosaurus was discovered in Outer Mongolia in 1922, in the early stages of the famous expeditions undertaken by the American Museum of Natural History between 1922 and 1925. Henry Osborn named it for the beak-like appearance of its face. It is known from a number of well-preserved skeletons, which represent about eight different species from Mongolia, southern Siberia, and northern China, as well as from some lower jaw fragments that were discovered in northern Thailand.

Psittacosaurus was one of the earliest ceratopsians, but closer to Triceratops than Yinlong. Once in its own family, Psittacosauridae, with other genera like Hongshanosaurus, it is now considered to be senior synonym of the latter and an early offshoot of the branch that led to more derived forms. The genera closely related to Psittacosaurus are all from Asia, with the exception of Aquilops, from North America. The first species was either P. lujiatunensis or closely related, and it may have given rise to later forms of Psittacosaurus.

A Psittacosaurus skeleton cast in the permanent collection of The Children’s Museum of Indianapolis.

Psittacosaurus is one of the most completely known dinosaur genera. Fossils of hundreds of individuals have been collected so far, including many complete skeletons. Most age classes are represented, from hatchling through to adult, which has allowed several detailed studies of Psittacosaurus growth rates and reproductive biology. The abundance of this dinosaur in the fossil record has led to the labelling of Lower Cretaceous sediments of east Asia the Psittacosaurus biochron.

Psittacosaurus is known from hundreds of individual specimens, of which over 75 have been assigned to the type species, P. mongoliensis. All Psittacosaurus fossils discovered so far have been found in Early Cretaceous sediments in Asia, from southern Siberia to northern China, and possibly as far south as Thailand. The most common age of geologic formations bearing Psittacosaurus fossils is from the late Barremian through Albian stages of the Early Cretaceous, or approximately 126 to 101 mya (million years ago). Many terrestrial sedimentary formations of this age in Mongolia and northern China have produced fossils of Psittacosaurus, leading to the definition of this time period in the region as the Psittacosaurus biochron.

Plateosaurus

Wednesday, December 7, 2016

Plateosaurus skeleton

Plateosaurus (probably meaning “broad lizard”, often mistranslated as “flat lizard”) is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 214 to 204 million years ago, in what is now Central and Northern Europe. Plateosaurus is a basal (early) sauropodomorph dinosaur, a so-called “prosauropod”. As of 2011, two species are recognized: the type species P. engelhardti from the late Norian and Rhaetian, and the slightly earlier P. gracilis from the lower Norian. However, others have been assigned in the past, and there is no broad consensus on the species taxonomy of plateosaurid dinosaurs. Similarly, there are a plethora of synonyms (invalid duplicate names) at the genus level.

P. engelhardti skull cast, Royal Ontario Museum

Discovered in 1834 by Johann Friedrich Engelhardt and described three years later by Hermann von Meyer, Plateosaurus was the fifth named dinosaur genus that is still considered valid. Although it had been described before Richard Owen formally named Dinosauria in 1842, it was not one of the three genera used by Owen to define the group, because at the time, it was poorly known and difficult to identify as a dinosaur. It is now among the dinosaurs best known to science: over 100 skeletons have been found, some of them nearly complete. The abundance of its fossils in Swabia, Germany, has led to the nickname Schwäbischer Lindwurm (Swabian lindworm).

Plateosaurus had stout limbs that supported the considerable weight of the animal as it walked on all four legs. As with other prosauropods, Plateosaurus’s hind legs were stronger than the front ones and were able to take the weight of the creature when it reared up, either to reach higher branches for food, or possibly to defend itself against attack-a particularly large claw on each thumb would have been an effective weapon in such a circumstance. Its long tail would have acted as a counterbalance to the long, thick neck.

Plateosaurus was a bipedal herbivore with a small skull on a long, flexible neck, sharp but plump plant-crushing teeth, powerful hind limbs, short but muscular arms and grasping hands with large claws on three fingers, possibly used for defence and feeding. Unusually for a dinosaur, Plateosaurus showed strong developmental plasticity: instead of having a fairly uniform adult size, fully grown individuals were between 4.8 and 10 metres (16 and 33 ft) long and weighed between 600 and 4,000 kilograms (1,300 and 8,800 lb). Commonly, the animals lived for at least 12 to 20 years, but the maximum life span is not known.

Plateosaurus trossingensis – Wikimedia

Despite the great quantity and excellent quality of the fossil material, Plateosaurus was for a long time one of the most misunderstood dinosaurs. Some researchers proposed theories that were later shown to conflict with geological and palaeontological evidence, but have become the paradigm of public opinion. Since 1980 the taxonomy (relationships), taphonomy (how the animals became embedded and fossilized), biomechanics (how their skeletons worked), and palaeobiology (life circumstances) of Plateosaurus have been re-studied in detail, altering the interpretation of the animal’s biology, posture and behaviour.

Protoceratops

Wednesday, December 7, 2016

Protoceratops skeleton

Protoceratops (meaning “First Horned Face”) is a genus of sheep-sized (1.8 m long) herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period (Campanian stage) of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs. Unlike later ceratopsians, however, it was a much smaller creature that lacked well-developed horns and retained some primitive traits not seen in later genera.

Size of P. andrewsi compared to a human

Protoceratops had a large neck frill which was likely used as a display site to impress other members of the species. Other hypotheses about its function include protection of the neck and anchoring of jaw muscles, but the fragility of the frill and the poor leverage offered by possible attachment sites here makes these ideas implausible. Described by Walter W. Granger and W.K. Gregory in 1923, Protoceratops was initially believed to be an ancestor of the North American ceratopsians. Researchers currently distinguish two species of Protoceratops (P. andrewsi and P. hellenikorhinus), based in part by their respective sizes.

P. andrewsi growth series. Author: HARRY NGUYEN

Protoceratops was a very common animal in the late Cretaceous lowland habitats of Mongolia. Fossilized remains of this dinosaur were among the most abundant fossils found on the American Museum of Natural History expeditions to Mongolia that Roy Chapman Andrews led between 1922 and 1925. The abundance of these fossils has led scientists to believe that Protoceratops was a highly social animal that lived in herds.

The American expeditions also discoveered eggs and nests belonging to Protoceratops. These were the first dinosaur nests ever found, and the discovery was widely publicized. Another famous find was that of a Protoceratops skeleton interlocked with that of a Velociraptor. Whether or not this find represents an actual act of predation, Velociraptor, along with the larger theropods such as Tarbosaurus, would almost certainly have been among the main predators on a small plant-eater such as Protoceratops.

Two skeletons and a reconstructed nest, AMNH

Protoceratops was a quadrupedal dinosaur that was partially characterized by its distinctive neck frill at the back of its skull. The frill itself contained two large parietal fenestrae (holes in the frill), while its cheeks had large jugal bones. The exact size and shape of the neck frill varied by individual; some specimens had short, compact frills, while others had frills nearly half the length of the skull. The frill consists mostly of the parietal bone and partially of the squamosal. Some researchers, including Peter Dodson attribute the different sizes and shapes of these bones to sexual dimorphism, as well as the age of the specimen, at the time of death.

Protoceratops by Vlad Konstantinov

Protoceratops was the first named protoceratopsian and hence gives its name to the family Protoceratopsidae, a group of herbivorous dinosaurs more derived than psittacosaurids, but less derived than ceratopsids. The group is characterized by their similarities to the Ceratopsidae but with more cursorial limb proportions, generally smaller frills, and lack of large horns.

In 1998, Paul Sereno defined Protoceratopsidae as the branch-based clade including “all coronosaurs closer to Protoceratopsthan to Triceratops.” Some studies placed BagaceratopsBreviceratopsGraciliceratopsLamaceratopsMagnirostrisPlatyceratops, and Serendipaceratops within Protoceratopsidae, but in 2006, Makovicky and Norell published a new phylogeny which removed several genera from Protoceratopsidae; several other phylogenies also exist. Bainoceratops may be synonymous with Protoceratops.

Source: www.wikipedia.org

Why Were Dinosaurs so Big?

Wednesday, December 7, 2016

The Facts and Theories Behind Dinosaur Gigantism

One of the things that makes dinosaurs so appealing is their sheer size: plant eaters like Diplodocus and Brachiosaurus weighed in the neighborhood of 25 to 50 tons, and a well-toned Tyrannosaurus rex tipped the scales as much as 10 tons. From the fossil evidence, it’s clear that–species by species, individual by individual–dinosaurs were more massive than any other group of animals that ever lived (with the logical exception of certain genera of prehistoric sharks, prehistoric whales and marine reptiles like ichthyosaurs and pliosaurs, the extreme bulk of which were supported by the natural buoyancy of water).

However, what’s fun for dinosaur enthusiasts is often what causes paleontologists and evolutionary biologists to tear their hair out. The giant size of dinosaurs demands an explanation, and one that’s compatible with other dinosaur theories–for example, it’s impossible to discuss dinosaur gigantism without paying close attention to the whole cold-blooded/warm-blooded metabolism debate.

So what’s the current state of thinking about plus-sized dinosaurs? Here are a few more-or-less interrelated theories.

Sauropod features vs other-groups

THEORY #1: DINOSAUR SIZE WAS FUELED BY VEGETATION

During the Mesozoic Era–which stretched from the beginning of the Triassic period, 250 million years ago, to the extinction of the dinosaurs at the end of the Cretaceous period, 65 million years ago–atmospheric levels of carbon dioxide were much higher than they are today. If you’ve been following the global warming debate, you’ll know that increased carbon dioxide is directly correlated with increased temperature–meaning the global climate was much warmer millions of years ago than it is today.

This combination of high levels of carbon dioxide (which plants recycle as food via the process of photosynthesis) and high temperatures (an average of 90 or 100 degrees Fahrenheit, even near the poles) meant that the prehistoric world was matted with all kinds of vegetation–plants, trees, mosses, etc.

Like kids at an all-day dessert buffet, sauropods may have evolved to giant sizes simply because there was a surplus of nourishment at hand. This would also explain why certain tyrannosaurs and large theropods were so big; a 50-pound carnivore wouldn’t have stood much of a chance against a 50-ton plant eater.

THEORY #2: HUGENESS IN DINOSAURS WAS A FORM OF SELF-DEFENSE

If Theory #1 strikes you as a bit simplistic, your instincts are correct: the mere availability of huge amounts of vegetation doesn’t necessarily entail the evolution of giant animals that can swallow it down to the last shoot. (After all, the earth was shoulder-deep in microorganisms for hundreds of millions of years before the appearance of multicellular life, and we don’t have any evidence of one-ton bacteria.) Evolution tends to work along multiple paths, and the fact is that the drawbacks of dinosaur gigantism (such as the slow speed of individuals and the need for limited population size) could easily have outweighed its benefits in terms of food-gathering.

That said, some paleontologists do believe that gigantism conferred an evolutionary advantage on the dinosaurs that possessed it: for example, a jumbo-sized hadrosaur like Shantungosaurus would have been virtually immune to predation when fully grown, even if the tyrannosaurs of its ecosystem hunted in packs.

(This theory also lends some indirect credence to the idea that Tyrannosaurus rex scavenged its food–say, by happening across the carcass of an Ankylosaurus that died of disease or old age–rather than actively hunting it down.) But once again, we have to be careful: of course giant dinosaurs benefited from their size, because otherwise they wouldn’t have been gigantic in the first place, a classic example of an evolutionary tautology.

THEORY #3: DINOSAUR GIGANTISM WAS A BYPRODUCT OF COLD-BLOODEDNESS

This is where things get a bit sticky. Many paleontologists who study giant plant-eating dinosaurs like hadrosaurs and sauropods believe that these behemoths were cold-blooded, for two compelling reasons: first, based on our current physiological models, a warm-blooded Mamenchisaurus would have cooked itself from the inside out, like a potato, and promptly expired; and second, no land-dwelling, warm-blooded mammals living today even approach the size of the largest herbivorous dinosaurs (elephants weigh a few tons, max, and the largest terrestrial mammal in the history of life on earth, Indricotherium, only topped out at about 20 tons).

Here’s where the advantages of gigantism come in. If a sauropod evolved to large-enough sizes, scientists believe, it would have achieved “homeothermy”–that is, the ability to maintain its interior temperature despite the prevailing environmental conditions. This is because a house-sized, homeothermic Argentinosaurus would warm up slowly (in the sun, during the day) and cool down equally slowly (at night), giving it a fairly constant average body temperature–whereas a smaller reptile would be at the mercy of ambient temperatures on an hour-by-hour basis.

The problem is, these speculations about cold-blooded herbivorous dinosaurs run counter to the current vogue for warm-blooded carnivorous dinosaurs. Although it’s not impossible that a warm-blooded Tyrannosaurus rex could have coexisted alongside a cold-blooded Titanosaurus, evolutionary biologists would be much happier if all dinosaurs, which after all evolved from the same common ancestors, possessed uniform metabolisms–even if these were “intermediate” metabolisms that don’t correspond to anything seen in modern animals.

DINOSAUR SIZE: WHAT’S THE VERDICT?

If the above theories leave you as confused as you were before reading this article, you’re not alone. The fact is that evolution toyed with the existence of giant-sized terrestrial animals, over a time span of 100 million years, exactly once, during the Mesozoic Era. Before and after the dinosaurs, most terrestrial creatures were reasonably sized, with the odd exceptions (like the above-mentioned Indricotherium) that proved the rule. Most likely, some combination of theories #1, #2 and #3, along with a possible fourth theory that we have yet to formulate, explains the huge size of dinosaurs; in exactly what proportion, and in what order, will have to await future research.

Source: www.thoughtco.com, www.huffingtonpost.com

Were Dinosaurs Warm-Blooded or Cold-Blooded?

Wednesday, December 7, 2016

Growth rates across an evolutionary tree. Dinosaurs growth rates fall in between warm blooded mammals and birds ('endotherms') in red, and cold-blooded fish and reptiles ('ectotherms') in blue. They are closest to living mesotherms. Credit: John Grady.

QUICK ANSWER

Because dinosaurs are classified as reptiles, one might assume that they are cold blooded, but some scientists suggest that dinosaurs may have been somewhere between cold and warm blooded. Though most animals fall into either category, there have been some intermediary species known to science, with dinosaurs potentially being one of this number.

Dinosaurs as mesotherms by John Grady

FULL ANSWER

The lack of certainty and the assertion that dinosaurs may have been neither warm nor cold blooded stems from the fact that birds, which may be the dinosaurs’ closest living relatives, are warm blooded, unlike modern reptiles, which are cold blooded. There is also evidence to suggest that dinosaurs had faster metabolisms than cold-blooded animals typically have.

Dinosaurs were neither warm nor cold blooded

Depending on the source of an organism’s body warmth, it may be classified as either an ectotherm or an endotherm. An ectotherm is an animal that warms itself primarily by obtaining heat from the environment, perhaps by sunning itself. Ectothermic animals include most fish, amphibians, and reptiles as well as most invertebrates. An endotherm is an animal that produces most of its own heat and maintains a constant body temperature even when environmental temperatures fluctuate. All birds and mammals are endotherms.

Paleontologists have struggled for years to determine whether dinosaurs were cold-blooded like today’s reptiles or warm-blooded like most modern mammals and birds.

It turns out the answer is neither. Scientists have found evidence for “mesothermy” in dinosaurs. The “mesothermy” found in dinosaurs likely allowed them to move quickly, given that they would not need to constantly eat in order to maintain their body temperature (as do endotherms). As well, the dinosaur’s mesothermic metabolic rate would have decreased the vulnerability of these species to extreme fluctuations in external temperature, allowing them to exert some control of body temperature via internal mechanisms.

Source: www.SciNews.com

Mesozoic Era: Age of the Dinosaurs

Wednesday, December 7, 2016

The Mesozoic Era: When Dinosaurs Ruled the Earth

During the Mesozoic, or “Middle Life” Era, life diversified rapidly and giant reptiles, dinosaurs and other monstrous beasts roamed the Earth. The period, which spans from about 252 million years ago to about 66 million years ago, was also known as the age of reptiles or the age of dinosaurs.

Life Through Time: Mesozoic era

Boundaries

English geologist John Phillips, the first person to create the global geologic timescale, first coined the term Mesozoic in the 1800s. Phillips found ways to correlate sediments found around the world to specific time periods, said Paul Olsen, a geoscientist at the Lamont-Doherty Earth Observatory at Columbia University in New York.

The Permian-Triassic boundary, at the start of the Mesozoic, is defined relative to a particular section of sediment in Meishan, China, where a type of extinct, eel-like creature known as a conodont first appeared, according to the International Commission on Stratigraphy.

The end boundary for the Mesozoic Era, the Cretaceous-Paleogene boundary, is defined by a 20-inch (50 centimeters) thick sliver of rock in El Kef, Tunisia, which contains well-preserved fossils and traces of iridium and other elements from the asteroid impact that wiped out the dinosaurs. The Mesozoic Era is divided up into the Triassic, Jurassic, and Cretaceous periods.

New research suggests that reptiles that lived during the Dinosaur age were hard-hit. Here, the carnivorous lizard Palaeosaniwa chases a pair of young Edmontosaurus while the snake Cerberophis and the lizard Obamadon look on. Credit: Carl Buell

Life and climate

The Mesozoic Era began roughly around the time of the end-Permian extinction, which wiped out 96 percent of marine life and 70 percent of all terrestrial species on the planet. Life slowly rebounded, eventually giving way to a flourishing diversity of animals, from massive lizards to monstrous dinosaurs.

The Triassic Period, from 252 million to 200 million years ago, saw the rise of reptiles and the first dinosaurs, the Jurassic Period, from about 200 million to 145 million years ago, ushered in birds and mammals, and the Cretaceous Period, from 145 million to 66 million years ago is known for some of its iconic dinosaurs, such as Triceratops and Pteranodon.

Coniferous plants, or those that have cone-bearing seeds, already existed at the beginning of the era, but they became much more abundant during the Mesozoic. Flowering plants emerged during the late Cretaceous Period. The lush plant life during the Mesozoic Era provided plenty of food, allowing the biggest of the dinosaurs, such as the Argentinosaurus, to grow up to 80 tons, according to a 2005 study in the journal Revista del Museo Argentino de Ciencias Naturales.

Earth during the Mesozoic Era was much warmer than today, and the planet had no polar ice caps. During the Triassic Period, Pangaea still formed one massive supercontinent. Without much coastline to moderate the continent’s interior temperature, Pangaea experienced major temperature swings and was covered in large swaths of desert. Yet the region still had a belt of tropical rainforest in regions around the equator, said Brendan Murphy, an earth scientist at St. Francis Xavier University in Antigonish, Canada.

Extinctions

The Mesozoic Era was bookended by two great extinctions, with another smaller extinction occurring at the end of the Triassic Period, Olsen said.

Around 252 million years ago, the end-Permian extinction wiped out most life on Earth over about 60,000 years, according to a February 2014 study in the journal Proceedings of the National Academy of Sciences (PNAS). At the end of the Triassic Period, roughly 201 million years ago, most amphibious creatures and crocodile-like creatures that lived in the tropics were wiped out. About 65 million years ago, a giant asteroid blasted into Earth and formed a giant crater at Chicxulub in the Yucatan Peninsula.

Because the fossil record is incomplete, it’s difficult to say exactly what caused the extinctions, or even how rapidly they occurred. After all, certain species or traces of catastrophic events could be missing in the fossil record simply because the sediments may have disappeared over tens of millions of years, Olsen said.

“Nature is very efficient at getting rid of its corpses,” Olsen told Live Science.

However, there are a few prime suspects in each of the extinctions.

At the end of the Permian, the Siberian Traps underwent massive volcanic eruptions, which most geologists believe caused the world’s biggest extinction. Exactly how, however, is up for debate.

The volcanic eruptions caused a spike in carbon dioxide in the atmosphere, though the 2014 PNAS study suggests that the spike was brief. The eruptions may have increased sea surface temperatures and led to ocean acidification that choked out sea life. And another study published in March 2014 in PNAS proposed that the eruptions released huge troves of the element nickel, which fueled a feeding frenzy by nickel-munching microbes known as Methanosarcina. Those microbes may have belched out huge amounts of methane, superheating the planet.

Most scientists agree that an asteroid impact wiped out the dinosaurs at the end of the Cretaceous Period. The impact would have kicked up so much dust that it blocked the sun, halted photosynthesis, and led to such a huge disruption in the food chain that everything that wasn’t a scavenger or very small died.

But the Deccan Traps, in what is now India, were spewing massive amounts of lava both before and after the asteroid impact, and a few scientists believe these flows either directly caused or accelerated the dinosaurs’ demise.

Volcanism may also be to blame for the end-Triassic extinction. Though volcanism in general leads to global warming, after an initial volcanic eruption, huge amounts of sulfur spew into the air and cause a brief period of global cooling. Such cooling-heating cycles may have occurred hundreds of times over 500,000 years. Similar cold snaps have been tied to huge crop failures in historical times, such as in Iceland in the 1700s, Olsen said.

As a result, animals used to constant, balmy temperatures in the tropics were wiped out, while animals that were insulated with proto-feathers, such as pterosaurs, or that lived at higher latitudes and were already adapted to big temperature variations, did just fine, Olsen said.

“When you have these volcanic winters, where temperatures may have dropped even below freezing in the tropics, it was devastating,” Olsen said.

Source: www.livescience.com/38596-mesozoic-era.html

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