Q & A

Top 10 Largest Dinosaurs (to date)

Saturday, December 24, 2016


Newly discovered dinosaur fossils, plus a new assessment of dino size, have led to a revised list of the top 10 largest dinosaurs to date.

The top 10 largest terrestrial animals on Earth were all dinosaurs, and a new analysis of dinosaur fossils reveals the biggest of the big.

The new study, published in the journal Scientific Reports, determined that the most gargantuan dinosaurs were all herbivores.

Sauropod dinosaurs — long-necked plant eaters — include the largest land animals that have ever existed,” lead author Kenneth Lacovara of Drexel University told Discovery News.

“Multiple studies have shown that the body weight of a four-legged animal corresponds closely with measurements taken from its humerus (upper arm bone) and femur (thigh bone),” Lacovara said.


Diplodocus longus by Dmitry Bogdanov

Calculations based on such fossil measurements put Diplodocus longus in the No. 10 spot. The estimated mass (a measure of how much matter is in an individual or object) of this dinosaur is 16.3 tons.


Dmitry Bogdanov, Wikimedia Commons

Weighing in at No. 9 is Giraffatitan brancai. Its mass was calculated to be 37.5 tons.

Girth is only one component of size, but the longest dinosaurs tended also to be the heftiest. Lacovara said many such dinosaurs spent their days pursuing “a life-long obsession with eating.” Dinosaurs like Giraffatitan would devote hour after hour to consuming tree and fern leaves, not moving much from their feasting spots.


Skeleton of Futalognkosaurus – Wikimedia Commons

No. 8 on the list is Futalognkosaurus dukei, which had an estimated mass of 42 tons. That’s equivalent to 84,000 pounds.


Elaltitan lilloi by Dmitry Bogdanov

Next in the lineup is Elaltitan lilloi. According to the new study, its mass was 47.2 tons. This dinosaur lived in what is now southern Argentina.


Turiasaurus – Wikimedia Commons

Turiasaurus riodevensis is one of the largest dinosaurs ever to be found in Europe. The dinosaur, which had a mass of 56.1 tons, was excavated in what are now eastern Spain and Portugal.


Brachiosaurus by Dmitry Bogdanov

Weighing in at 62 tons is Brachiosaurus altithorax, which was hailed as “the largest-known dinosaur” by discoverer Elmer Riggs in 1903. While it’s No. 5 on the list now, at 62 tons, this dinosaur still made the top 10.


Sauroposeidon by Manuel Gil Jaramillo

Sauroposeidon proteles was not included in the Scientific Reports study. This species, and the entire genus, are only known from several incomplete specimens. So it’s more challenging to accurately estimate its weight and height. Some paleontologists theorize that it weighed anywhere from 55-66 tons. It could, therefore, move even higher on this list should more fossils be found.


Dmitry Bogdanov, Wikimedia Commons

Lacovara and a team of his colleagues discovered Paralititan stromeri in 2001. “We only recovered the humerus of Paralititan, and therefore cannot be sure about its limb proportions,” Lacovara told Discovery News.

Based on the fossil that was excavated, however, it was an enormous dinosaur. The humerus, measuring about 5 1/2 feet, is lengthier than that of any other known Cretaceous sauropod. Paralititan is another contender for possible top spot placement on this list if additional fossils are found and support the speculation about its size.


Mark A. Klinger, Carnegie Museum of Natural History

Dreadnoughtus schrani has the largest reliably calculable weight of any known land animal,” Lacovara said. Announcement of its discovery was made just this week, reminding that on any day, new fossil finds could change this list.

The mass of Dreadnoughtus was 65.4 tons. This dinosaur had no known enemies during its lifetime.


Argentinosaurus huinculensis, reconstructed skeleton at Naturmuseum Senckenberg

Most paleontologists, including Lacovara, believe that Argentinosaurus huinculensis was the world’s largest-ever land animal. “I think it is very likely that Argentinosaurus is the most massive dinosaur yet known,” Lacovara said. “However, I don’t think we can make a reliable estimation of its mass.”

He explained that the femur sometimes associated with this species has never formally been referred to in a peer-reviewed journal. Rough estimates by others estimate that Argentinosaurus could have been 115 feet in length with a weight of anywhere from 88–110 tons.

Source: www.seeker.com / www.wikipedia.com


Thursday, December 22, 2016

Family tree of the Hadrosauroidea. Representative genera of each tribe are shown to scale

Hadrosaurids, or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is also known as the duck-billed dinosaurs, for the flat, duck-bill appearance of the bones in their snouts. The family, which includes ornithopods such as Edmontosaurus and Parasaurolophus, was a common herbivore in the Upper Cretaceous Period of what is now Asia, Europe, Antarctica, South America, and North America. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout. Like the rest of the ornithischians, these animals had a predentary bone and a pubic bone which was positioned backwards in the pelvis. Hadrosaurids are divided into two principal subfamilies: the lambeosaurines (Lambeosaurinae), which had hollow cranial crests or tubes, and the saurolophines, identified as hadrosaurines in most pre-2010 works (Saurolophinae or Hadrosaurinae), which lacked hollow cranial crests (solid crests were present in some forms). Saurolophines tended to be bulkier than lambeosaurines. Lambeosaurines are divided into aralosaurines, lambeosaurines, parasaurolophines, and tsintaosaurines, while saurolophines include saurolophus, brachylophosaurines, and kritosaurines.

North American Hadrosaurs by PaleoGuy

Hadrosaurs had a stiff tail that was probably used for balance. They had hoof-like nails on their feet, and bumpy skin. They ran on two legs, holding their tail and head in a horizontal position. They may have walked on all four legs while grazing. Hadrosaurs probably lived near bodies of water, migrating to high ground to lay eggs. It used to be thought that they had webbed hands, but this was an artifact of the fossilization process.

The two major divisions of hadrosaurids are differentiated by their cranial ornamentation. While members of the Lambeosaurinae subfamily have hollow crests that differ depending on species, members of the Saurolophinae (Hadrosaurinae) subfamily have solid crests or none at all. Lambeosaurine crests had air chambers that may have produced a distinct sound and meant that their crests could have been used for both an audio and visual display.

Edmontosaurus skull, Oxford University Museum of Natural History. Photo by Ballista

Hadrosaurs are closely related to the Iguanodontids, and are probably their descendants. Hadrosaurs were Ornithischians (the order of bird-hipped dinosaurs) and Ornithopods (“bird-footed” herbivores with hoof-like feet). Hadrosaurs are divided into two groups, the Hadrodsaurinae (non-crested hadrosaurs) and the Lambeosaurinae (hadrosaurs that had skull crests that connected with their nasal passages).

Hadrosaurs lived during the late Cretaceous period. Their fossils have been found in North America, Europe, and Asia.

Although it has been long believed that hadrosaurs originated in Asia, the new find, Protohadros byrdi, seems to shift the birthplace of hadrosaurs to North America. Protohadros byrdi dates from 95.5 million years ago, was recently found in Texas, USA.

The following taxonomy includes dinosaurs currently referred to the Hadrosauridae and its subfamilies. Hadrosaurids that were accepted as valid, but not placed in a cladogram at the time of Prieto-Márquez’s 2010 study, are included at the highest level to which they were placed (either then, or in their description if they postdate the papers used here).

  • Family Hadrosauridae

    • Subfamily Hadrosaurinae

    • Subfamily Saurolophinae

    • Subfamily Lambeosaurinae

    • Dubious hadrosaurids

      • Arstanosaurus

      • Cionodon

      • Diclonius

      • Dysganus

      • Mandschurosaurus

      • Microhadrosaurus

      • Orthomerus

      • Pteropelyx

      • Thespesius

      • Trachodon

Source: www.wikipedia.org

Why Were There So Many Dinosaur Species?

Monday, December 19, 2016

Dinosaurs by Durbet on DeviantArt

A new species of dinosaur is described, on average, every ten days. As many as 31 species have already been reported this year and we can expect a few more before 2016 is over. Of course, figuring out what counts as a distinct species is a tricky problem. Paleontologists are argumentative by nature, so getting any two of them to agree on a definitive list of species is probably impossible. But by anyone’s count, there were a lot of them – 700 or 800 that we know of, probably thousands in total. So how did the dinosaurs become so diverse?

So many fossils. Shutterstock

First we need an idea of just how many dinosaur species there were. One study tried to estimate the total diversity of dinosaurs by using the species-area effect – the idea being that if we know how many species one small part of the Earth can support, we can extrapolate how many must have existed worldwide. These calculations suggest that at the end of the Mesozoic, 66m years ago, the standing diversity of dinosaurs – all the species alive at one point in time – was between 600 and 1,000 species.

This seems to be a reasonable estimate, in that if you counted up all of the living land mammals weighing more than 1kg (the size of the smallest dinosaurs) and then added the extinct species from the past 50,000 years, such as wooly mammoths, ground sloths, and giant kangaroos (correcting for losses to diversity caused by humans) you would end up with a similar figure.

However, this is just the number of species around at one point in time, and the dinosaurs were around for a very, very long time. Over the course of the Mesozoic, dinosaurs constantly evolved and went extinct. Doing some quick and rough estimates, and assuming 1,000 species of dinosaurs lived at any one time, and then that the species turned over every million years – that’s 160 times over the 160m-year reign of the dinosaurs – we end up with 160,000 species. Which is a lot of dinosaurs.

This is, of course, a very rough estimate. It depends on a lot of assumptions, such as how many different species the planet can support, and how quickly they evolve and go extinct. If we assume a lower standing diversity of 500 species and slower turnover, with species lasting 2m years, for example, we end up with around 50,000 species. On the other hand, perhaps standing diversity of 2,000 species is reasonable for the warm, lush, Mesozoic, and perhaps they only lasted just half a million years. That gives us over 500,000 species. So it seems reasonable to guess that there were between 50,000 and 500,000 species of dinosaurs – without including Mesozoic birds, which might double the diversity.

Why so many species, then? It comes down to three things. Dinosaurs were good at specialization, localisation, and speciation.


Dinosaurs were specialists, and by specializing to exploit different niches, different species could coexist without competing. In western North America, the giant predator T. rex coexisted with little meat-eating dromaeosaurs. Enormous, long-necked sauropods browsed alongside horned ceratopsians, which grazed on ferns and flowers. There were smaller plant-eaters – pachycephalosaurs and ornithomimids – as well as heron-like fish eaters, and even anteater-like insectivores.

And within these niches, there was further specialization. T. rex was large and had massive jaws but fairly stocky limbs, and was well-suited to preying on the slow-moving but heavily armed TriceratopsT. rex‘s cousin, Nanotyrannus, was smaller but had the lanky legs of a marathon runner, and probably chased down faster prey. This specialization meant that – based on my recent studies of the fauna – as many as 25 dinosaurs could live side-by-side in one habitat.


Localisation refers to how different places had different dinosaur species. Mongolia had one set of animals – tyrannosaurs, duckbills, and ostrich dinosaurs – inhabiting a lush delta that flowed through the middle of a desert. Just a few miles away, little horned dinosaurs and parrot-headed oviraptors inhabited the dune fields. Dinosaurs also show differences across continents, with different species inhabiting different parts of North America, for example. Between continents, the differences are even more extreme. During the Late Cretaceous, North America and Asia were dominated by tyrannosaurs, duckbilled dinosaurs, and horned dinosaurs. But Africa and South America, cut off by oceans for tens of millions of years, had an entirely different set of species. Instead of tyrannosaurs, the horned abelisaurs were top predators. Instead of duckbills, the long-necked titanosaurs were the dominant plant eaters.


Dinosaurs evolved new species with remarkable speed. Radioactive dating has made it possible to date the rocks containing dinosaur fossils, and from that, to estimate how long dinosaur species lasted. The rocks forming the Hell Creek Formation in Montana, for example, were deposited over a period of around 2m years. At the bottom of these strata, we have one species- Triceratops horridus, and at the top, we have a second Triceratops prorsus evolving from the first.

This implies that a species lasts a million years or less – a short time, at least in geological terms. Studies of other formations, and other horned dinosaurs, tend to suggest that other species were similarly short-lived. In the badlands of Dinosaur Park in Canada, we can find fossils that show three different sets of dinosaur – the first replaced by the second, the second by the third – evolving in 2m years. Dinosaurs evolved rapidly, driven by shifts in the planet’s seas, climates, and continents, and also the evolution of other dinosaurs. And if they didn’t, they went extinct.

We’ll never know exactly how many dinosaurs existed. It’s so rare for an animal to fossilize and be preserved that many tens of thousands of species, maybe hundreds of thousands, are probably lost to us forever. And yet the remarkable thing is that the pace of dinosaur discovery has actually increased over the years. Most of the species that have ever lived are lost, but we have thousands left to find.

Source: www.theconversation.com

How Do Scientists Determine The Age Of Dinosaur Bones?

Thursday, December 8, 2016

Fossilised bones of a dinosaur in Argentina

When paleontologist Mary Schweitzer found soft tissue in a Tyrannosaurus rex fossil, her discovery raised an obvious question — how the tissue could have survived so long? The bone was 68 million years old, and conventional wisdom about fossilization is that all soft tissue, from blood to brains, decomposes. Only hard parts, like bones and teeth, can become fossils. But for some people, the discovery raised a different question. How do scientists know the bones are really 68 million years old?

Today’s knowledge of fossil ages comes primarily from radiometric dating, also known as radioactive dating. Radiometric dating relies on the properties of isotopes. These are chemical elements, like carbon or uranium, that are identical except for one key feature — the number of neutrons in their nucleus.

The 67-million-year-old Tyrannosaurus rex skeleton known as Sue stands on display at Union Station on June 7, 2000, in Washington, D.C. MARK WILSON/NEWSMAKERS/GETTY IMAGES

Usually, atoms have an equal number of protons and neutrons. If there are too many or too few neutrons, the atom is unstable, and it sheds particles until its nucleus reaches a stable state. Think of the nucleus as a pyramid of building blocks. If you try to add extra blocks to the sides pyramid, they may stay put for a while, but they’ll eventually fall away. The same is true if you take a block away from one of the pyramid’s sides, making the rest unstable. Eventually, some of the blocks can fall away, leaving a smaller, more stable structure.

The result is like a radioactive clock that ticks away as unstable isotopes decay into stable ones. You can’t predict when a specific unstable atom, or parent, will decay into a stable atom, or daughter. But you can predict how long it will take a large group of atoms to decay. The element’s half-life is the amount of time it takes for half the parent atoms in a sample to become daughters.

To read the time on this radioactive clock, scientists use a device called a mass spectrometer to measure the number of parent and daughter atoms. The ratio of parents to daughters can tell the researcher how old the specimen is. The more parent isotopes there are — and the fewer daughter isotopes — the younger the sample. The half-life of the isotope being measured determines how useful it is at dating very old samples. Once all the parents have become daughters, there’s no more basis for comparison between the two isotopes. Scientists can’t tell whether the clock ran down a few days or millions of years ago. This means that isotopes with a short half-life won’t work to date dinosaur bones.

The short half-life is only part of the problem when dating dinosaur bones — researchers also have to find enough of the parent and daughter atoms to measure. Read on to see what it takes to date a fossil and what volcanic ash has to do with it.

An eagle flies over the Grand Canyon in Arizona, April 5, 2007. You can see the layers of sedimentary rock GABRIEL BOUYS/AFP/GETTY IMAGES

The most widely known form of radiometric dating is carbon-14 dating. This is what archaeologists use to determine the age of human-made artifacts. But carbon-14 dating won’t work on dinosaur bones. The half-life of carbon-14 is only 5,730 years, so carbon-14 dating is only effective on samples that are less than 50,000 years old. Dinosaur bones, on the other hand, are millions of years old — some fossils are billions of years old. To determine the ages of these specimens, scientists need an isotope with a very long half-life. Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.

Unfortunately, these elements don’t exist in dinosaur fossils themselves. Each of them typically exists in igneous rock, or rock made from cooled magma. Fossils, however, form in sedimentary rock — sediment quickly covers a dinosaur’s body, and the sediment and the bones gradually turn into rock. But this sediment doesn’t typically include the necessary isotopes in measurable amounts. Fossils can’t form in the igneous rock that usually does contain the isotopes. The extreme temperatures of the magma would just destroy the bones.

So to determine the age of sedimentary rock layers, researchers first have to find neighboring layers of Earth that include igneous rock, such as volcanic ash. These layers are like bookends — they give a beginning and an end to the period of time when the sedimentary rock formed. By using radiometric dating to determine the age of igneous brackets, researchers can accurately determine the age of the sedimentary layers between them.

Using the basic ideas of bracketing and radiometric dating, researchers have determined the age of rock layers all over the world. This information has also helped determine the age of the Earth itself. While the oldest known rocks on Earth are about 3.5 billion years old, researchers have found zircon crystals that are 4.3 billion years old [source: USGS]. Based on the analysis of these samples, scientists estimate that the Earth itself is about 4.5 billion years old. In addition, the oldest known moon rocks are 4.5 billion years old. Since the moon and the Earth probably formed at the same time, this supports the current idea of the Earth’s age.

Other Dating Methods

Radiometric dating isn’t the only method of determining the age of rocks. Other techniques include analyzing amino acids and measuring changes in an object’s magnetic field. Scientists have also made improvements to the standard radiometric measurements. For example, by using a laser, researchers can measure parent and daughter atoms in extremely small amounts of matter, making it possible to determine the age of very small samples.

Source: NewScientist.com

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

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


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.


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.


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.


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.


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


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

What If a Giant Asteroid Had Not Wiped Out the Dinosaurs?

Wednesday, December 7, 2016

This impact was actually the least of the dinosaurs’ worries. Illustration by Franco Tempesta, National Geographic

During the new DC Comics Universe series “Flashpoint,” in which a time-traveling supervillain alters the past to warp the present, Life’s Little Mysteries presents a 10-part series that examines what would happen if a major event in the history of the universe had gone just slightly different.

Part 2: What if … a giant asteroid had not killed off the dinosaurs?

Other factors were involved in dinosaurs’ extinction, but the resounding death knell was the impact of a 6-mile-wide asteroid in present-day Mexico’s Yucatan Peninsula 65 million years ago, creating what is known as the 110-mile-wide, 6-mile-deep Chicxulub crater. The event unleashed mega-tsunamis, planetwide wildfires and kicked up enough dust and debris to block the sun and cause a period of global cooling, which killed off many plants.

The asteroid hit what is now Mexico (Credit: Joe Tucciarone/Science Photo Library)

Life would be: Still dinosauric in all likelihood, assuming no other catastrophic, extinction-level events transpired. After all, dinos had a good long run of dominance on land for 160 million years prior, and if that continued, primates like us would not be around, said Damian Nance, a professor of geosciences at Ohio University. Mammals did co-evolve alongside dinosaurs, but they occupied fringe ecological niches and grew no larger than rodents in most cases.

Only with dinosaur plant-devourers gone would there be enough food for mammals to seize the day and eventually give rise to us (knocking out the predators that would eat mammals helped, too). Researchers have speculated that intelligent “dinosauroids” might have evolved in humanity’s place, based on the relatively large brain size of late-emerging trodontid species, which were bird-like predators.

Of course, some of those dinosaurs that have survived into modern day — becoming birds — are quite smart, but not smart enough to have ended up on the other side of the insult “bird-brained.”

Source: BBC Nature

What If the Supercontinent Pangea Had Never Broken Up?

Wednesday, December 7, 2016

What If the Supercontinent Pangaea Had Never Broken Up?

During the new DC Comics Universe series “Flashpoint,” in which a time-traveling supervillain alters the past to warp the present, Life’s Little Mysteries presents a 10-part series that examines what would happen if a major event in the history of the universe had gone just slightly different.

The breakup of the Pangaea supercontinent. Credit: U.S. Geological Survey

Part 3: What if … the supercontinent Pangaea never broke up?

From about 300 million to 200 million years ago, all seven modern continents were mashed together as one landmass, dubbed Pangaea. The continents have since “drifted” apart because of the movements of the Earth’s crust, known as plate tectonics. Some continents have maintained their puzzle piece-like shapes: Look at how eastern South America tucks into western Africa.

Life would be: Far less diverse. A prime driver of speciation the development of new species from existing ones is geographical isolation, which leads to the evolution of new traits by subjecting creatures to different selective pressures. Consider, for example, the large island of Madagascar, which broke off from Gondwana, Pangaea’s southern half, 160 million years ago. About nine out of 10 of the plant and mammal species that have evolved on the island are not found anywhere else on the planet, according to Conservation International.

A locked-in Pangaea further constrains life’s possibilities because much of its interior would be arid and hot, said Damian Nance, a professor of geosciences at Ohio University. “Because of Pangaea’s size, moisture-bearing clouds would lose most of their moisture before getting very far inland,” Nance told Life’s Little Mysteries.

Excess mass on a spinning globe shifts away from the poles, so the supercontinent would also become centered on the equator, the warmest part of the planet. Reptiles could deal with such a climate better than most, which is partly why dinosaurs, which emerged during the time the planet’s surface was one giant chunk, thrived before mammals.

What is Gondwana?

Wednesday, December 7, 2016

The Gondwana supercontinent after amalgamation of West and East Gondwana

Gondwana was an ancient supercontinent that broke up about 180 million years ago. The continent eventually split into landmasses we recognize today: Africa, South America, Australia, Antarctica, the Indian subcontinent and the Arabian Peninsula.

The familiar continents of today are really only a temporary arrangement in a long history of continental movement. Landmasses on Earth are in a constant state of slow motion, and have, at multiple times, come together as one. These all-in-one supercontinents include Columbia (also known as Nuna), Rodinia, Pannotia and Pangaea (or Pangea).

Gondwana was half of the Pangaea supercontinent, along with a northern supercontinent known as Laurasia.

The breakup of the Pangaea supercontinent. Credit: U.S. Geological Survey

The creation of Gondwana

Gondwana’s final formation occurred about 500 million years ago, during the late Ediacaran Period. By this time, multicellular organisms had evolved, but they were primitive: The few fossils left from this period reveal segmented worms, frond-like organisms and round creatures shaped like modern jellyfish.

In this world, Gondwana conducted its slow grind to supercontinent status. Bits and pieces of the future supercontinent collided over millennia, bringing together what are now Africa, India, Madagascar, Australia and Antarctica.

This early version of Gondwana joined with the other landmasses on Earth to form the single supercontinent Pangaea by about 300 million years ago. About 280 million to 230 million years ago, Pangaea started to split. Magma from below the Earth’s crust began pushing upward, creating a fissure between what would become Africa, South America and North America.

As part of this process, Pangaea cracked into a northernmost and southernmost supercontinent. The northern landmass, Laurasia, would drift north and gradually split into Europe, Asia and North America.

The southern landmass, still carrying all those bits and pieces of the future southern hemisphere, headed southward after the split. This supercontinent was Gondwana.

Gondwana’s breakup

During Gondwana’s stint as the southerly supercontinent, the planet was much warmer than it was today — there was no Antarctic ice sheet, and dinosaurs still roamed the Earth. By this time, it was the Jurassic Period, and much of Gondwana was covered with lush rainforest.

The great supercontinent was still under strain, however. Between about 170 million and 180 million years ago, Gondwana began its own split, with Africa and South America breaking apart from the other half of Gondwana. About 140 million years ago, South America and Africa split, opening up the South Atlantic Ocean between them. Meanwhile, on the eastern half of the once-supercontinent, Madagascar made a break from India and both moved away from Australia and Antarctica.

Australia and Antarctica clung together longer; in fact, Antarctica and Australia didn’t make their final split until about 45 million years ago. At that point, Antarctica started to freeze over as Earth’s climate cooled, while Australia drifted northward. (Today, the Australian continent still moves north at a rate of about 1.2 inches (3 centimeters) a year.)

Gondwana theory

The exact mechanisms behind Gondwana’s split are still unknown. Some theorists believe that “hot spots,” where magma is very close to the surface, bubbled up and rifted the supercontinent apart. In 2008, however, University of London researchers suggested that Gondwana instead split into two tectonic plates, which then broke apart.

The existence of Gondwana was first hypothesized in the mid-1800s by Eduard Suess, a Viennese geologist who dubbed the theoretical continent “Gondwanaland.” Suess was tipped off by similar fern fossils found in South America, India and Africa (the same fossils would later be found in Antarctica). At the time, plate tectonics weren’t understood, so Suess didn’t realize that all of these continents had once been in different locations. Instead, he developed a theory of sea level rise and regression over time that would have linked together the southern hemisphere continents with land bridges.

Suess got the name Gondwanaland from the Gondwana region of central India, where geological formations match those of similar ages in the southern hemisphere.

Source: www.NatGeo.com