September 28, 2016

When you see models or illustrations of dinosaurs, have you ever wondered how accurate they are? Bones, skin impressions, and tracks can tell scientists and artists a great deal about the shape, size, and movements of these animals, but how do people know what color patterns the beasts adopted? Most of the time, artists make educated guesses based on what is known about each dinosaur and its habitat. But researchers led by Jakob Vinther of the University of Bristol in the United Kingdom recently collaborated with artist Bob Nicholls to create what may be the most accurate representation of a dinosaur to date. What’s more, the finished model provided clues about the animal’s habitat (rather than the other way around).

The recently created Psittacosaurus model shows the dinosaur with countershading camouflage (darker on top, lighter on bottom). Many modern-day animals exhibit countershading. Credit: © Jakob Vinther, Robert Nicholls, Stephan Lautenschlager, Michael Pittman, Thomas G. Kaye, Emily Rayfield, Gerald Mayr, Innes C. Cuthill/Univerity of Bristol

Psittacosaurus was a small plant-eating dinosaur that lived 130 million to 100 million years ago in what is now Asia. Its name, which means parrot lizard, comes from its large, sharp, parrotlike beak. The dinosaur measured up to about 2 feet (60 centimeters) tall at the hips and 6 1/2 feet (2 meters) long.

Vinther’s team examined an exquisitely preserved Psittacosaurus from China that included much of its skin. They found that darker areas of skin were full of melanosomes, tiny structures that produce pigments, but the lighter areas were not. This discovery showed that the color pattern seen in the fossil was real, and not the result of discoloration during fossilization.

With that knowledge, the researchers turned to Bob Nicholls, a Bristol-based paleoartist (an artist who specializes in depicting prehistoric life). He carefully examined the specimen, taking into account every minute pattern on the animal’s skin. He then created two sculptures of the animal, painting one a uniform shade of gray, and decorating the other with the intricate patterns seen in the fossil.

From the sculpture, it became clear that Psittacosaurus exhibited countershading. Countershading is a type of camouflage in which the parts of an animal exposed to sunlight are darker colored and the animal’s underside is lighter colored. In sunlight, the exposed, darker-colored sections appear brighter and the lighter-colored sections are shaded by the rest of the body. This effect flattens the appearance of the animal and makes it more difficult to see. Many kinds of animals, from sharks to antelope, exhibit countershading. In the case of Psittacosaurus, this small herbivore (plant eater) was countershaded to try to escape the sight of large meat-eating dinosaurs—relatives of the infamous Tyrannosaurus rex—that lived in the area at the time.

Vinther and his team then took the two sculptures to ecosystems with different lighting characteristics and observed how well camouflaged the countershaded model was in relation to the gray one. They found that the countershaded sculpture was best camouflaged in areas with moderate tree cover, suggesting that this species of Psittacosaurus lived in woodland environments. This evidence also jibes with other fossils that have been found along with the Psittacosaurus, such as petrified tree trunks and remains of shade-loving plants. This is the first time that a dinosaur’s color pattern was used to infer the type of environment in which it lived.

This study showed that determining the colors and color patterns of dinosaurs isn’t just a goal in and of itself, but it can also help define a dinosaur’s ancient environment. It’s not just good for art; it’s good for science!

September 12, 2016

Bigfoot and Yowie (a large, hairy ape said to live in the wild regions of Australia) might be mere legends, but one giant ape was certainly more than myth. Standing at a whopping 10 feet (3 meters) tall and weighing more than 900 pounds (400 kilograms), Gigantopithecus was about twice the size of a large male gorilla, making it the largest ape that ever lived. Gigantopithecus walked on its hands and fists, like today’s great apes, and roamed the tropical forests of what are now southern China, northern Vietnam, and northern India. Scientists believe that Gigantopithecus was related to ancestors of the modern orangutan.

A Gigantopithecus replica (known as “Mr. G”) was installed at the Museum of Man in San Diego, California, in 2003. Credit: © ZUMA Press/Alamy Images

Gigantopithecus’s fellow jungle creatures had only to worry about being squashed, because the colossal ape was not a meat-eater. Instead, it ate such hardy foods as bamboo and durian (a tropical fruit with a hard, prickly outer skin), using its large jaws and teeth to chew the tough plant matter. It is quite possible that crocodiles and ancient relatives of tigers and hyenas fed on Gigantopithecus young, but adults were so enormous that predators probably left them alone.

Gigantopithecus lived from more than 8 million years ago to about 200,000 years ago. It may have disappeared as the result of a shift in southern Asia’s climate about 1 million years ago, when conditions became colder and drier and the giant ape’s forest home began to shrink. Scientists believe that Homo erectus, an ancient relative of humans, crossed paths with Gigantopithecus and may have hunted it, playing a role in the monstrous beast’s extinction.

August 24, 2016

Monkeys in the Amazon rain forest likely entered their own Stone Age more than 700 years ago, according to scientists investigating a fascinating site at Serra da Capivara National Park in northeastern Brazil. At the site, scientists from the University of Oxford in the United Kingdom and from Brazil’s University of São Paulo observed bearded capuchin monkeys (Sapajus libidinosus) using rocks as hammers to crush hard-shelled nuts atop flat stone anvils. The scientists discovered dozens of discarded stone hammers and anvils once they began shallow excavations at a site regularly visited by the monkeys. The scientists determined that monkeys have been using simple stone tools at that site for more than 700 years. The findings were described in the July 2016 issue of the journal Current Biology.

A capuchin monkey uses stones to crack a cashew nut in Serra da Capivara National Park in northeast Brazil. Credit: © Michael Haslam, Primate Archaeology Project/University of Oxford

Stone Age is a term used to designate the period when prehistoric people used stone, rather than metal, tools. For humans, the Stone Age began about 3.3 million years ago, when small stones were first made into crude chopping tools by prehuman ancestors called Australopithecines. It ended in the Near East about 3000 B.C., when bronze replaced stone as the chief material from which tools were made.

In dry northeastern Brazil, hard-shelled fruits and seeds are more common than the fruit and succulent leaves that capuchins prefer. Centuries ago, a clever capuchin figured out how to pound open a nut using a heavy stone as a hammer on a heavier flat stone anvil, thereby opening up an entirely new and abundant source of food. The scientists observed that the monkeys will carefully select hammer stones and bring them to trees bearing nuts and fruits. The monkeys then stash the stones in hidden spots around the trees for later use. The research site in Brazil is littered with such stones that have accumulated over centuries.

For many years, scientists considered humans to be the only species that made extensive use of tools. In the 1960’s, however, naturalist Jane Goodall discovered that wild chimpanzees in Africa make and use simple tools. Goodall observed them stripping tree twigs and using the twigs as tools for catching termites. She also observed chimpanzees using rocks to break open hard-shelled palm nuts in the forest.

Earlier in 2016, some of the scientists involved in the Brazil research published observations of monkeys called macaques using stones to break open shellfish and nuts in Thailand. Now, with the Brazilian study, there seems little doubt that some species of nonhuman primates have long since entered their own Stone Age. The site in Brazil provides scientists with a unique opportunity to study the ecological, social, and cognitive (mental) factors that likely played a role in the development of technology and culture millions of years ago at the dawn of humankind.

August 17, 2016

Eons ago, a monstrous beast stalked an ancient South American floodplain. One of its enormous footprints in the soft clay was covered with layers of silt and was preserved for some 70 million years. Last month, the track was discovered, revealing that huge predatory dinosaurs lived in South America up until the extinction of the group about 65 million years ago.

The record-setting dinosaur footprint was found at Maragua Crater near Sucre, Bolivia, a site already known for other, smaller dinosaur tracks. Credit: WORLD BOOK map

Dinosaurs are a group of prehistoric reptiles that ruled Earth for about 160 million years. Most of these animals died millions of years ago, but their direct descendants—birds—continue to flourish today. Dinosaurs have fascinated people ever since they were first described in the early 1800′s as having strange appearances and huge sizes. Scientists now know that not all dinosaurs were large. Many, such as the microraptor and compsognathus, were, in fact, quite small.

The South American footprint, however, belonged to something gigantic with really big feet. It was found about 45 miles (60 kilometers) outside of Sucre, the official capital city of Bolivia, by a local tour guide. At some 45 inches (115 centimeters) wide, it is the largest carnivorous (meat-eating) dinosaur footprint ever discovered. The previous record was nothing to sneeze at either: a 40-inch (110-centimeter) wide track from New Mexico, a state in the southwestern United States.

The animal that made the South American print probably belonged to a group of dinosaurs called abelisaurids, large meat-eaters with short skulls and tiny arms that lived in South America, Africa, and India. Based on the enormous size of the footprint, scientists think the dinosaur could have been up to 40 feet (12 meters) long.

The discovery of this footprint helps paleontologists fill in the history of large meat-eating dinosaurs in South America. Giganotosaurus, one of the largest meat-eating dinosaurs known, stalked the continent some 95 million years ago. But Giganotosaurus probably died out after 5 million years or so, and paleontologists had not found fossil evidence of any large carnivores taking its place. The print was dated at 70 million years old, showing that abelisaurids took over after the demise of Giganotosaurus. With any luck, paleontologists will soon find the bones of these giant hunters and better understand the ecology of South America at the end of the age of dinosaurs.

August 15, 2016

If you’re out on a nighttime walkabout in Australia, be careful that you don’t stroll too close to a billabong (water hole), lest you are grabbed by the terrifying Bunyip. According to tradition of the Aboriginal people of Australia, the Bunyip is a malevolent monster that lurks in the water, waiting to pounce upon its next meal. And that meal is sometimes human. It is said that on a quiet night in the Outback, you can hear the haunting cry of the Bunyip. Even today, Aboriginal people may steer clear of billabongs when they hear mysterious calls of the wild.

A terrifying depiction of the legendary Bunyip
Credit: State Library of Victoria

Most everyone in Australia has heard of the Bunyip, and it seems quite a few people know someone who says they saw one. Yet it is often impossible to find a person who has actually caught a glimpse of one. This may be why descriptions of the Bunyip vary widely. In some tales, it is a dog-like or seal-like creature. Bunyips have been described as being big as a horse and as small as a dog. They may have flippers, fangs, tusks, one or two eyes, shaggy fur, scales, or horns. Descriptions of the animal’s behavior also vary widely, from a man-eating monster to a timid plant-eating creature that shies away from humans.

When tales of the Bunyip reached the early European settlers of Australia, they  thought it may be yet another strange new creature (like kangaroos and koalas) that they had never before encountered. Several expeditions set out on vain attempts to capture a Bunyip. One expedition in 1846 was widely reported to have returned with the skull of a Bunyip (the skull was then supposedly lost). Most experts believe the skull was likely that of a horse or cow, perhaps modified to change its appearance. Today, scientists do not believe the Bunyip actually exists. They think that reported sightings are more likely the result of imagination, misidentification of other animals, or deliberate hoaxes.

Yet, legends of the Bunyip may not be all bull’s wool (nonsense). Some investigators consider the Bunyip to be a cryptid. A cryptid is a living thing whose existence has been suggested but not demonstrated (see cryptozoology). A few experts have suggested that the Bunyip could be a Diprotodon (giant wombat), a bear-sized Australian marsupial which is believed to have gone extinct more than 30,000 years ago. The Diprotodon likely spent days wallowing in shallow billabongs. The ancestors of Aboriginal people, who arrived in Australia more than 50,000 years ago, no doubt saw and probably hunted Diprotodon. It may be that stories of the Bunyip recount memories of ancestral encounters with this prehistoric giant in the Dreamtime, an ancient time in the belief of Aboriginal people of Australia when the first beings existed and the land was created.

July 19, 2016

Late last month, paleontologists (scientists who study fossils) announced an amazing discovery. Researchers led by Lida Xing at the China University of Geosciences in Beijing had discovered two bird wings preserved in amber. They published their findings in the journal Nature Communications.

Amber preserved this 100 million-year-old wing tip featuring bones, feathers, and soft tissue.
Credit: © Ryan C. McKellar, Royal Saskatchewan Museum

Amber is a hard, yellowish-brown fossilized resin. It comes chiefly from the resins of pine trees that grew millions of years ago. These resins were gummy materials mixed with oils in the trees. When the oils oxidized (combined with oxygen), hard resins were left. These pine trees were then buried underground or underwater, and the resins slowly changed into lumps of amber. These lumps often contain insects trapped as the resins flowed from the trees. But finding larger animals such as small vertebrates (animals with backbones) is incredibly rare. In the 1993 science fiction film Jurassic Park, dinosaur DNA (deoxyriboneucleic acid) is discovered in the blood of an ancient mosquito fossilized in amber. Movie scientists then used the DNA to recreate dinosaurs—an improbable, yet intriguing, plot line.

The wing fossil subjects of last month’s report were formed about 100 million years ago, in the Cretaceous Period, in what is now Myanmar (also called Burma). Two birds apparently became stuck in the sticky resin of a tree and died. The amber preserved the three-dimensional structure of the birds’ wings, as well as the wings’ feathers, skin, and bones—even the color patterns!

Xing and his team think the wings came from a group of birds called enantiornithines, which means opposite birds in Greek. These birds had claws and teeth, and they went extinct along with the nonflying dinosaurs about 65 million years ago. The fossils showed that the wings were from young birds and that the birds hatched as miniature adults, ready to fly. This is different from modern birds, which must develop for weeks or months before they can leave the nest.

The structure of the wings and the arrangement of feathers are similar to modern bird wings. Birds evolved (developed over time) about 150 million years ago from meat-eating dinosaurs, so they must have quickly developed modern-looking wings, before enantiornithines and the ancestors of modern birds split.

Unlike science fiction, these fossils won’t resurrect the extinct enantiornithines, even if they do contain DNA. The technology to create entire animals from bits of ancient DNA does not yet—and might never—exist. The fossils do, however, offer paleontologists a treasure trove of information that will help us better understand early birds and their world.

July 11, 2016

Glyptodont
Credit: Pavel Riha (licensed under CC BY-SA 3.0)

They say everything is bigger in Texas. But that state’s modern day mascot, the humble armadillo, is no match for its prehistoric cousin—the glyptodont. Although modern armadillos range in length from about 6 inches to 5 feet (15 centimeters to 1.5 meters), some species of glyptodont grew to over 10 feet (3 meters) long, the size of a small car.

This tanklike mammal lived in what is now South America during the Pleistocene Epoch, a time in Earth’s history that lasted from about 2.6 million years ago to 11,500 years ago. During the Pleistocene, many gigantic creatures roamed Earth, including mammoths and giant sloths. The saber-toothed cat and other Pleistocene predators had to be powerful to take down their giant prey. Glyptodont was protected from such monstrous beasts by a thick skullcap on its head and a massive carapace (shell) of bones that covered most of its body. Over 1,000 skin-covered bony plates made up this robust armor, which could weigh over 1,100 pounds (500 kilograms). Glyptodont was the most heavily armored vertebrate (animal with a backbone) that has ever lived.

The tails of some glyptodonts were tipped with a large, spiky club. In addition to warding off predators, these powerful weapons were used in fights with rivals during the mating season. Males clubbed one another’s carapaces, damaging the bony plates.

As invincible as such a beast might seem, Glyptodont disappeared at the end of the last ice age. Some scientists think that hunting by prehistoric people may have contributed to the extinction of these formidable creatures.

May 30, 2016

How many breadcrumbs would it take to feed a 1,000-pound (450-kilogram) duck? Measuring over 10 feet (3 meters) tall, the extinct thunder bird is sometimes called the demon duck of doom. This gigantic, flightless bird lived in what is now Australia, dying out 30,000 to 50,000 years ago.

The thunder bird, or “demon duck of doom” Credit: © Anne Musser, Australian Museum

Despite its demonic nickname, the thunder bird probably did not feast on flesh, but was mainly herbivorous (plant-eating). It used its heavy, strong bill to gobble down fruits, seeds, and other plant matter.

Another name for the thunder bird is mihirung, which comes from the Australian aboriginal term mihirung paringmal, meaning giant emu. The bird’s long neck, tiny wings, and massive, powerful legs led people to think that it was a relative of emus and ostriches. However, scientists now believe that it was more closely related to ducks and geese. The thunder bird did not live in the watery habitats favored by modern ducks and geese, however. Instead, it preferred to roam in grasslands and nest in sand dunes.

All but one species of this monstrous bird had died out by the time human beings reached Australia about 50,000 years ago. Some scientists argue that people may have accelerated the extinction of the thunder birds by hunting them or setting fire to their habitats. Climate change also likely played a role.

April 27, 2016

In this illustration, a group of dinosaurs and flying reptiles flee a vast fire. Such an event, connected to the eruption of a volcano, could have caused the extinction of the dinosaurs at the end of the Cretaceous, some 65 million years ago. Credit: © Mark Garlick, Photo Researchers

Dinosaurs reigned supreme on Earth for tens of millions of years. Other animals, such as mammals, lived in the shadows, eking out an existence among giant plant-eaters and ferocious predators. Dinosaurs were so dominant that, if it hadn’t been for some extremely bad luck 65 million years ago in the form of a giant asteroid, they might still populate Earth today. Right? Maybe, maybe not.

A recent study published in the journal Proceedings of the National Academy of Sciences casts doubt on this picture of dinosaur supremacy. Paleontologists Manabu Sakamoto and Chris Venditti of the University of Reading and Michael Benton of the University of Bristol analyzed parts of the dinosaur family tree over time. They compared speciation (spee see AYE shun) events to extinction events. Speciation is when one species evolves from another—for example, human beings, chimpanzees, and gorillas evolved from a common ancestor that lived between 4 million and 10 million years ago. That split that occurred was a speciation event. Sakamoto, Venditti, and Benton made comparisons of speciation and extinction events within five groups of dinosaurs: meat-eating theropods, long-necked sauropods, horned ceratopsians, duck-billed hadrosaurs, and other plant-eating dinosaurs.

The scientists found that the rate of extinction began to exceed the rate of speciation for theropods, sauropods, and other plant-eating dinosaurs 50 million years before the asteroid hit. This means that dinosaur species in these groups were going extinct faster than new species evolved to take their place as much as 115 million years ago, in the middle of the Cretaceous Period.

Does this mean that dinosaurs were already on their way out, and a huge rock from space only hastened their demise? Absolutely not! While the dinosaurs may have been experiencing a downturn in diversity, this study does not indicate that they were at death’s door. Whether dinosaurs gradually declined before their extinction has been a hotly-debated topic in paleontology for many years. In fact, long before the Chicxulub impact crater (created by an asteroid that struck Earth 65 million years ago) was discovered, most paleontologists thought the dinosaurs had slowly died out and that there was no mass extinction. The question of dinosaur decline is very complicated and touches on such paleontology issues as the completeness of the fossil record. Because of many differences in the layers of Earth, some animals in some periods have nearly complete fossil records, while others from other periods may have few or no fossils. This study will not be the last word on the matter.

The study does, however, highlight a few important things about dinosaur diversity and extinction. First, the extinction of the dinosaurs was a complex event. The environment of the Late Cretaceous was challenging. Enormous volcanoes called the Deccan Traps raged in what is now India. The climate was getting colder. Drifting continents and changing sea levels were fragmenting land habitats, making it more difficult for land-dwelling dinosaurs to move from place to place. These factors may have affected the group’s species diversity.

Second, the study highlights how diverse dinosaurs were. There are about 600 named dinosaur species, and scientists estimate that another 600 or more remain to be discovered. Some of these species may have lived in regions where fossilization rarely occurs (such as mountain environments) and thus will never be found. Some paleontologists involved in assessing dinosaur diversity point out that the astonishing diversification that occurred in the Jurassic Period could never have lasted forever, particularly in the challenging environment of the Late Cretaceous.

Finally, the study holds great relevance for us today. If the results are borne out by future analyses, it would suggest that a modest loss of species diversity may have made the dinosaurs more susceptible to random cataclysmic events such as the Chicxulub asteroid. Today, many species are going extinct, and the planet is warming rapidly. The loss of diversity might make today’s ecosystems more susceptible to collapse from random events such as volcanic eruptions or asteroid impacts. Like the dinosaurs, humans might have built their global dominance on an unstable foundation. Unlike the dinosaurs, however, we have the ability to make changes to strengthen ecosystems and reduce global warming, giving us more of a fighting chance against extinction.

Other World Book articles

• Drilling for Answers (March 9, 2016) – Behind the Headlines article
• Geology (2007) – A Back in Time Article
• Global warming

March 25, 2016

A reconstruction of the Tully Monster as it would have looked 300 million years ago, swimming in Carboniferous waters. Notice the jointed snout, the multiple rows of teeth, and the eye bar on the animal’s back. Credit: © Sean McMahon, Yale University

Over 300 million years ago, a strange creature lived in the rivers of Illinois. This creature was so bizarre that, after its fossil remains were discovered, it left paleontologists baffled for more than 60 years. Now, a group of scientists led by Victoria E. McCoy from Yale University seems to have finally discovered the true nature of the so-called Tully monster. The findings were published in the journal Nature on March 16.

Fossils are the marks or remains of organisms that lived thousands or millions of years ago. Some of the best-known fossils include leaves, shells, or skeletons that were preserved after a plant or animal died. The Mazon Creek region in north-central Illinois is one of the most important fossil sites in the world. It gives paleontologists a window into life over 300 million years ago, long before the dinosaurs ever existed. At this time, called the Carboniferous Period, the Mazon Creek area was a tropical river delta. (Because of the movement of the tectonic plates, Illinois was at that time near the equator and the ocean reached as far as Illinois.) Occasionally, floods would wash land- and river-dwelling organisms from the Mazon Creek area into the ocean and bury them—along with some ocean animals—under a thick layer of sediment. Compounds from the decomposing organisms changed the chemical makeup of the sediment around them. Over time, this sediment hardened to form a protective rock called a concretion around each organism.

In the 1800’s, people were mining for coal in the area and found these concretions. When cracked open, the concretions often revealed animals and plants preserved in exquisite detail. Amateur, as well as professional fossil hunters have scoured the area ever since. One amateur, Francis Tully (1912-1987), discovered a strange creature in 1955. When he turned it over to scientists at Chicago’s Field Museum, they named it Tullymonstrum gregarium—the common Tully monster—in his honor.

To the untrained eye, a Tully monster fossil might just look like a leaf. The animal had a long, oval-shaped body with two triangular tail fins. Its eyes rested on a skinny rod or bar. On top of all that, it had a long, wormlike snout ending in tiny, toothed jaws. From snout to tail, the whole creature grew little more than a foot (30 centimeters) long.

Paleontologists knew the Tully monster was an animal, but its strange body plan had long frustrated attempts to figure out which group of animals it belonged to. Over the years since it was discovered, different scientists have suggested it was related to squid, clams, snails, slugs, and many different kinds of worms. None of these guesses gained much traction.

This new team of scientists, however, noticed something that the others had overlooked. They realized that the thin, light band running along the length of the Tully monster, previously thought to be a digestive tract, was in fact a notochord. A notochord is a rodlike, flexible cord that runs down the back of the body in many early vertebrates. That meant the creature was more closely related to fish than it was to squid and worms. From there, the other pieces fell into place. The shape of the notochord and the structure of the gills and teeth indicated that the Tully monster was related to modern lampreys. Finally, the Tully monster, the state fossil of Illinois, has its place on the Tree of Life.

Other links and articles

• Chordate
• Classification, Scientific
• Mazon Creek Fossils (Illinois State Museum Site)