Exploring Prehistoric Life
America has cultivated a reputation as being a place that offers new beginnings, especially when times get tough elsewhere—but now paleontologists think that tradition may actually date back 140 million years, to the days when dinosaurs roamed the Earth. That’s because they realized two dinosaurs dug out of the rocks of Utah bear a strange resemblance to a family that had only been spotted in Europe and Africa previously.
That makes them think the immigrants made use of a temporary land bridge to colonize new territory, in the process evading (or at least delaying) the extinction that wiped out their Old World relatives. The team of paleontologists announced their find in a paper recently published in the journal Scientific Reports. In the paper, they describe the movements of a group of dinosaurs called turiasaurs, which were vegetarians and had long, giraffe-like necks.
In particular, the paleontologists identify a new species of turiasaur, based on specimens found a bit northeast of Arches National Park. Their picture of the new species, now named Mierasaurus bobyoungi, is based in particular on three legs of a still growing dinosaur that had fallen into a pit of mud.
“This poor animal had been stuck in the mud,” James Kirkland, a paleontologist with the Utah Geological Survey and co-author on the new paper, told Utah Public Radio. “You hate to imagine how long it took to actually die, unless it was lucky and some meat-eating dinosaur came and put it out of its misery.”
But what was a very bad day for the young dinosaur about 135 million years ago became a very good day for the paleontologists in 2010, when they first spotted its remains sticking out from the rock. Puzzled by the find, Kirkland brought in experts on European dinosaurs, who tied the Utah specimen to animals that had died out in Spain about 145 million years ago.
The paleontologists think a few European individuals from the new species and other turiasaurs migrated over to America via a land bridge. That migration let turiasaurs carve out a new life for themselves in Utah, which has now become a dinosaur discovery hotspot.
That picture could still change as paleontologists continue to uncover new specimens. One possible alternative explanation is that there are other, older turiasaur remains in the U.S. still waiting to be discovered, which could rewrite the dinosaurs’ history. Chances are, there’s more immigration paperwork trapped in North America’s rock.
At one point, this whole lousy planet was covered in dinosaurs of all sizes and descriptions. These days, if we want to see evidence of dinosaurs, we can go for a walk with a pair of binoculars aimed at the trees, or just spend some time scoping out a bird feeder.
And although it’s widely accepted that today’s birds are avian dinosaur descendants, part of the allure of the dinos of yore is their size and variety … and the fact that they’re not around anymore. That may be true, but there are nooks and crannies all over the globe where you can find evidence of the once-kings, straight out of Deep Time. Fossilized dinosaur tracks and footprints abound.
Dinosaur Ridge, Morrison, Colorado
Around 150 million years ago, during the late Jurassic, what’s now central Colorado was a beach. These days you can see the tracks and skeletal remains of hundreds of ornithopod and theropod dinosaurs — including the long-necked Apatosaurus, armored Stegosaurus, and carnivorous Allosaurus — that used the beach as a freeway.
Dampier Peninsula, Australia
The largest dinosaur print we know about can be found at a site called Walmadany, off Australia’s western coast. Twenty-one species cavorted here during the Cretaceous period, including the owner of a 5.5-foot-long (1.7-meter-long) sauropod track that belonged to an animal so immense a giraffe’s face could probably only reach its withers.
Parque Cretácico, Cal Orck’o, Bolivia
Once, nearly 70 million years ago, a baby Tyrannosaurus rex and a herd of long-necked sauropods ranging from 26-65 feet (8-20 meters) long made their way across a vast, muddy flat. Now this mudflat is a 300-foot (90-meter) vertical wall inside a rock quarry, covered with more than 5,000 tracks representing eight species and more than 450 individual dinosaurs. It’s the largest collection of dinosaur tracks in the world; you can find it in Bolivia’s Parque Cretácico.
Denali National Park, Alaska
The theropod tracks found in Denali National Park aren’t particularly interesting in and of themselves, but thousands of herbivorous hadrosaur tracks in the park provided scientists with evidence that dinosaurs might have lived year-round in polar latitudes.
Staffin Beach, Island of Skye, Scotland
We don’t generally think of dinosaurs being great parents, but it’s possible Scotland’s own “Dinosaur Island”has evidence of just that. The small prints left by ornithopods around 170 million years ago seem to tell the story of a parent being followed by several juveniles down the shoreline of a lake.
Check out the following images for a few more places around the globe you can visit to see dinosaur footprints.
An international team of researchers led by the Swedish Museum of Natural History has discovered that fossilized remains of woolly mammoths (Mammuthus primigenius) more often came from males than females (69% versus 31%). The scientists speculate that this skewed ratio exists in the fossil record because inexperienced male mammoths more often traveled alone and got themselves killed by falling into natural traps that made their preservation more likely.
“Most bones, tusks, and teeth from mammoths and other Ice Age animals haven’t survived,” said senior author Dr. Love Dalen, from the Swedish Museum of Natural History.
“It is highly likely that the remains that are found in Siberia these days have been preserved because they have been buried, and thus protected from weathering.”
“Our findings imply that male mammoths more often died in a way that meant their remains were buried, perhaps by falling through lake ice in winter or getting stuck in bogs.”
For the study, Dr. Dalen and colleagues generated genomic data from 98 bone, tooth, and tusk samples collected at various locations throughout Siberia.
They then used these data to determine the sex of the mammoth specimens.
“We were very surprised because there was no reason to expect a sex bias in the fossil record,” said first author Dr. Patrícia Pečnerová, also from the Swedish Museum of Natural History.
“Since the ratio of females to males was likely balanced at birth, we had to consider explanations that involved better preservation of male remains.”
The findings suggest that woolly mammoths lived similarly to modern elephants, with herds of females and young elephants led by an experienced adult female.
In contrast, the authors suspect that male mammoths, like elephants, more often lived in bachelor groups or alone and engaged in more risk-taking behavior.
“Without the benefit of living in a herd led by an experienced female, male mammoths may have had a higher risk of dying in natural traps such as bogs, crevices, and lakes,” Dr. Dalen said.
The findings are published in the journal Current Biology.
Patrícia Pečnerová et al. Genome-Based Sexing Provides Clues about Behavior and Social Structure in the Woolly Mammoth. Current Biology, published online November 2, 2017; doi: 10.1016/j.cub.2017.09.064
Fossil remains of two rat-like creatures understood to be the oldest known ancestors of humans have been discovered in Dorset.
The small furry animals scurried in the shadow of the dinosaurs 145 million years ago.
Scientists believe they can draw a direct evolutionary line from the ancient mammals to people living today.
Two teeth belonging to two different species were sifted out of samples of Cretaceous period rock collected from exposed cliffs near Swanage.
Dr Steve Sweetman, from the University of Portsmouth, said his “jaw dropped” when one of the university’s undergraduate students asked him to look at the specimens.
He said: “The teeth are of a type so highly evolved that I realised straight away I was looking at remains of Early Cretaceous mammals that more closely resembled those that lived during the latest Cretaceous, some 60 million years later in geological history.
“In the world of palaeontology there has been a lot of debate around a specimen found in China, which is approximately 160 million years old. This was originally said to be of the same type as ours but recent studies have ruled this out. That being the case, our 145 million-year-old teeth are undoubtedly the earliest yet known from the line of mammals that lead to our own species.”
The area where student Grant Smith found the teeth is known as the Jurassic Coast because it has produced so many dinosaur fossils.
Both the ancient mammals were probably nocturnal, Dr Sweetman and co-authors reported in the journal Acta Palaeontologica Polonica.
One was likely to have been a burrower that ate insects and the other larger creature may have consumed plants as well, the researchers believe.
Dr Sweetman added: “The teeth are of a highly advanced type that can pierce, cut and crush food. They are also very worn which suggests the animals to which they belonged lived to a good age for their species – no mean feat when you’re sharing your habitat with predatory dinosaurs.”
The animals are believed to be direct ancestors of most mammals living today including creatures as diverse as the blue whale and pigmy shrew, as well as humans.
One of the species has been named Durlstotherium newmani, after Charlie Newman, landlord of the Square and Compass pub in the village of Worth Matravers close to where the fossils were discovered. The other has been named Durlstodon Ensomi.
The dinosaur “collective” fragmented, leaving dinosaurs to evolve in isolated groups and develop traits distinctly different from their sundered cousins on other landmasses.
During the 19th century, naturalist Charles Darwin began speculating about the relationship between living and fossil species while developing his theory of natural selection and “descent with modification,” to explain why some species became extinct while others evolved.
But no one paid much attention to geology’s role in biological evolution until 1910, when geophysicist Alfred Wegener, curious about why identical plant and animal fossils were being found on separate continents, realized that the outline of the east coast of South America fit against the lower west coast of Africa like pieces in a massive jigsaw puzzle.
It was as if the two continents had once been joined — an insight later confirmed by modern geology.
Africa, the first landmass to separate from Gondwana, supported Cretaceous Period dinosaurs like Suchomimus, a three-ton, bipedal predator with a skull resembling a contemporary crocodile’s. It was also home to Nigersaurus, whose wide, flat, vacuum-cleaner-nozzle-shaped mouth was packed with 50 teeth each in its upper and lower jaws, making it perfect for gobbling low-growing plants. Each tooth position held nine replacement teeth, meaning that Nigersaurus replaced 80 to 100 teeth each month — without missing a single meal.
Meanwhile, in South America, Giganotosaurus roamed the badlands of what is now Argentina’s Patagonia region. Perhaps the largest land carnivore that ever lived, this 43-foot-long, 13,200-pound behemoth comes alive at the Denver Museum of Nature & Science special exhibition “Ultimate Dinosaurs,” where visitors can manipulate special screens to see what a creature’s skin and facial coloration might have looked like in “real life.”
More than 70 million years ago, the world’s fourth-largest island separated from Gondwana.
It has remained a loner ever since.
Situated off Africa’s southeastern coast, Madagascar’s continued geographical isolation means that today, about 80 percent of its wildlife — which includes zoologically primitive primates and hedgehog-like insectivores — is found nowhere else in the world.
That same isolation also greatly affected the evolution of Madagascar’s Cretaceous Period dinosaurs, bizarre creatures that included Masiakasaurus knopfleri, a predatory theropod or meat-eater that stood just 30 inches high, sported strange-looking, forward-pointing teeth at the front of its mouth, and was discovered by a team led by David W. Krause, senior curator of vertebrate paleontology at the Denver Museum of Nature & Science.
Equally unusual was Majungasaurus crenatissimus, a 4,400-pound, cannibalistic predator with a taste for sauropod flesh and “arms” — forelegs too small to have been useful for feeding or hunting.
Perhaps such limbs were a feather-covered factor in attracting a mate, says Joe Sertich, curator of dinosaurs at DMNS. He discovered the fossilized Majungasaurus skull and neck bones housed at the museum as part of its Madagascar Paleontology Project and displayed in the special exhibition “Ultimate Dinosaurs.”
Other oddities include rahonavis, the smallest Cretaceous Period dinosaur found thus far on Madagascar. Although this theropod probably had feathers and might have been capable of flight, rahonavis wasn’t a direct relative of birds, the living descendants of the dinosaurs. It might, instead, have been a genuine link between small theropod dinosaurs and “true” birds.
And then there’s Simosuchus, a stubby, blunt-snouted, and rather cute (to me, at least) creature that turned out not to be a dinosaur at all, but a land-dwelling, plant-eating crocodilian completely unlike any modern crocodile.