Dinosaur age fossil snake discovery

This video says about itself:

Lizards, Snakes and Legs (Evolution)

27 September 2008

David Attenborough explaining how lizards lost their legs.

From daily The Independent in Britain:

Ancient snake skull found in Argentina could reveal why the reptiles have no legs

The research challenges the theory that snakes originally became limbless as they began to live in the sea

John von Radowitz

27 November 2015

A fossilised snake skull found in Argentina may have solved the mystery of how the animals lost their legs.

Rather than shed them to become better swimmers as they began to inhabit aquatic environments, the skull, from 90 million years ago, suggests legs became an evolutionary disadvantage as the ancestors of modern snakes wriggled into increasingly narrow burrows in pursuit of prey.

The research challenges the theory that snakes originally became limbless as they began to live in the sea. The secret of the lost limbs was revealed by an examination of the inner ear of Dinilysia patagonica, a two-metre long relative of the modern snake.

Using Computed Tomography (CT), scientists found a distinctive structure in its bony canals and cavities that was also turned out to be present in modern burrowing snakes and lizards.

But the structure, which may assist with the detection of prey and predators, was missing from snakes that live in water or above ground. Lead scientist Dr Hongyu Yi, from the University of Edinburgh’s School of GeoSciences, said: “How snakes lost their legs has been a mystery to scientists but it seems this happened when their ancestors became adept at burrowing.

“The inner ears of fossils can reveal a remarkable amount of information and are very useful when the exterior of fossils are too damaged or too fragile to examine.”

The findings, published in the journal Science Advances, confirm Dinilysia patagonica as the largest burrowing snake ever known.

Co-author Dr Mark Norell, from the American Museum of Natural History, said: “This discovery would not have been possible a decade ago. CT scanning has revolutionised how we can study ancient animals.

“We hope similar studies can shed light on the evolution of more species, including lizards, crocodiles and turtles.”

A CT scan is an advanced form of X-ray that generates detailed 3D images of organs and skeletal structures.

See also here.

Missing link dinosaur nests-bird nests discovery

This video from Canada says about itself:

First feathered dinosaur from North America introduced by Darla Zelenitsky

26 October 2012

Canadian researchers discover fossils of first feathered dinosaurs from North America.

From Science magazine:

Missing link between dinosaur nests and bird nests

By Sid Perkins

25 November 2015 2:00 pm

The links between dinosaurs and birds keep getting stronger: skeletal structures, feathers—and now nests. Whereas some dinosaurs buried their eggs crocodile-style, a new analysis suggests that other dinosaurs built open nests on the ground, foreshadowing the nests of birds.

Interpreting the fossil record is always tough, but analyzing trace fossils such as nests is especially daunting. Those structures, and the materials used to make them, usually aren’t preserved, says Darla Zelenitsky, a paleobiologist at the University of Calgary in Canada. When paleontologists do find a nestlike structure that includes material such as sticks or other vegetation, the question arises: Was this stuff part of the original nest, or just carried there with the sediment that buried the nest and helped preserve it?

To gain insight into dinosaur nesting habits, Zelenitsky and her colleagues studied the most durable parts of nests—the eggs themselves. (Being largely made of the mineral calcium carbonate, they’ve got a head start on fossilization and are sometimes incredibly well preserved.) In particular, the team looked at the size and arrangement of small pores in the ancient shells, because those details are telling in modern creatures.

In crocodiles’ buried nests, the heat needed to incubate the eggs comes from decomposition of overlying organic matter or the sunlight absorbed by the soil. Plus, in buried nests airflow is somewhat limited, thus requiring eggs to be relatively porous to help increase the flow of oxygen into and carbon dioxide out of the eggs. But birds that brood in open nests can get by laying eggs with fewer or smaller pores.

So the team compared the porosity of eggshells from 29 species of dinosaurs (including large, long-necked herbivores called sauropods; bipedal meat-eaters called theropods; and duck-billed dinosaurs) with that of shells from 127 living species of birds and crocodiles.

Most of the dinosaur eggs were highly porous, suggesting that they buried their eggs to incubate them, the researchers report online today in PLOS ONE. But some of the dinosaur species in one group—a subset of well-evolved theropods considered to be the closest relatives of modern-day birds—laid low-porosity eggs, which suggests they incubated their eggs in open nests.

“This is a well done paper; the results make a lot of sense,” says Luis Chiappe, a vertebrate paleontologist at the Natural History Museum of Los Angeles County in California. The findings, he says, line up other studies suggesting that some birdlike dinosaurs were warm-blooded, which would have enabled them to incubate eggs in an open nest rather than depend on rotting vegetation or sunlight. Chiappe adds that the trend toward open nests could have allowed some dinosaurs to take another step toward birdlike nesting by moving their nests into the trees.

But considering only two types of nests—open versus buried—may be too simplistic, suggests Anthony Martin, a paleontologist at Emory University in Atlanta. Some dinosaurs—like a few of today’s birds—may have nested in burrows, which could have offered the stable temperature and protection from predators of a buried nest but resulted in low-porosity shells. Also, covered nests come in different types: Loose vegetation piled atop a buried nest can have a lot of airflow through it, allowing eggs to have relatively small pores, whereas eggs buried in soil or similar materials might not breathe as well and thus require larger pores, he notes. Nevertheless, Martin adds, the team’s study “is a good first start toward answering the question about what early dinosaur nests looked like.”

See also here.

The findings were published online on Nov. 25 2015 in the journal PLOS ONE.

Corn snakes, why some are white

This video from the USA says about itself:

15 August 2014

The corn snake (Pantherophis gutattus gutattus) is a medium sized non-venomous colubrid that lives in the southeastern United States. Their bright colors, docile temperament, and minimum care requirements make them great for pets but it’s important to note that those you find in the wild are facing a decline in numbers and should be left alone if at all possible.

From Reptiles magazine:

Corn Snake Genome Sequenced, Albinism Mutation Detailed

November 25, 2015

By John Virata

Scientists with the University of Geneva (UNIGE), Switzerland have sequenced the corn snake Pantherophis guttatus (Elaphe guttata) genome for the first time, and discovered the mutation in the snake that causes albinism in the species, according to a paper published in Scientific Reports.

“Our aim was to produce ourselves a substantial portion of the missing data by sequencing all genes from several reptilian species. To reach this goal, we used tissues, such as the brain and the kidney, expressing the largest number of genes,” said Athanasia Tzika, researcher in the Department of Genetics and Evolution at UNIGE. “The objective was to obtain a genuine reptilian genomic model that people could rely on,” said Athanasia Tzika. “Here, we covered about 85% of the snake total genome size. There is much additional work ahead.”

The data compiled by Tzika will be freely available to researchers around the world who are working on developmental and evolutionary studies of reptiles.

UNIGE researcher Suzanne Saenko, working with Swedish scientists identified the mutation responsible for amenalism. The researchers bred a wild corn snake with a captive bred amenalistic corn snake and DNA sequenced all offspring from the cross and identified the malfunctioning gene. The gene OCA2 codes for a receptor located in the membranes of melanosomes, where melanin is found, according to the study. The receptor controls the acidity that enables the synthesis of melanin.

The researchers say that they will look into how some corn snakes are born with modified colors and patterns like longitudinal lines rather than transversal saddles that are typical of the species.

Dinosaur-age haramiyids, mammals or reptiles?

This video from the USA says about itself:

High-tech analysis of proto-mammal fossil clarifies the mammalian family tree

16 November 2015

3D Reconstruction of the jaw of Haramiyavia, one of the earliest known proto-mammals, clarifies the debate over when mammals evolved. The study, published in the Proceedings of the National Academy of Sciences on Nov 16, 2015, confirms previous suggestions that mammal diversification occurred in the Jurassic around 175 million years ago—more than 30 million years after Haramiyavia and other forerunners to mammals diversified in the Triassic.

From the New York Times in the USA:

Jawbone in Rock May Clear Up a Mammal Family Mystery


NOV. 16, 2015

With technologies like CT scans and 3-D printing, a team of scientists reported on Monday that it had solved a mystery about the family tree of mammals that started with a single tooth a century and a half ago.

The tooth, found in Germany in 1847, was tiny and distinctive in shape — not quite reptile, not quite mammal. More fossils of that kind were found around Europe, but always just single teeth. Scientists named this group of animals haramiyids — Arabic for “trickster.”

The teeth were embedded in rocks as old as 210 million years, an era in which ancestors of the first mammals were evolving.

“These were some of the most enigmatic fossils for years,” said Neil H. Shubin, a professor of organismal biology and anatomy at the University of Chicago. “People didn’t know what they were at all.”

In the late 1980s, Dr. Shubin, then a graduate student, was part of a team led by Farish Jenkins, a Harvard paleontologist, that searched for fossils in East Greenland. “You’re looking for tiny teeth in this vast Arctic landscape,” Dr. Shubin said. “The words ‘needle in a haystack’ seem very appropriate.”

The researchers found one particularly intriguing specimen, which they named Haramiyavia. “Avia” is Latin for “grandmother” — this was the grandmother of the trickster.

After a couple of years of meticulously clearing away much of the limestone surrounding the fossil, they reported on part of the Haramiyavia jawbone, revealing that the animal was indeed a proto-mammal.

What was unclear was whether Haramiyavia was a direct part of the family tree of mammals — that would push the emergence of mammals back to more than 200 million years ago — or an evolutionary branch that split off before common ancestors of mammals emerged, the view of paleontologists who believe that the first mammals evolved 170 million to 160 million years ago.

About two years ago, Dr. Shubin decided to re-examine the slab of Greenland limestone that enveloped the Haramiyavia fossil. “We knew that there were more bones in the rock,” he said.

Clearing away more limestone would jeopardize the fragile fossil. Instead, Dr. Shubin and his colleagues placed it in CT scanners and saw a mostly complete jawbone and many of the teeth.

“This kind of work used to be unimaginable,” said Zhe-Xi Luo, another University of Chicago paleontologist who joined Dr. Shubin on the new analysis.

Their conclusion: Haramiyavia, and thus all haramiyids, were not mammals, but belonged to a more ancestral side branch.

The crucial evidence they cite, reported Monday in the Proceedings of the National Academy of Sciences, is a trough in the lower jaw of Haramiyavia. In mammals, the trough is absent, because two bones connected to the trough migrated to the middle ear to form part of the three-bone hearing mechanism. (Birds and reptiles have only one bone in their middle ears.)

“This thing had a very primitive ear,” Dr. Shubin said. “That is the piece that is sort of the smoking gun.”

From the scans of the jaw and the teeth, the researchers created three-dimensional enlargements of the fossils, studying them like puzzle pieces to see how they fit together. Haramiyavia, a few inches long and rodentlike in appearance, ate plants by grinding leaves between broad teeth.

One argument that haramiyids were mammals was the similarity of the teeth to those of later animals known as multituberculates that were unquestionably mammals. But Dr. Shubin said the explanation instead was that the similar tooth characteristics evolved independently.

Timothy Rowe, a professor of geology at the University of Texas at Austin who was not involved in the new research, praised the work. “They really stepped out and squeezed every last bit of information that they could from these fossils,” he said. “What a relief after all these years to see a very compelling case made for exactly where haramiyids fit on the family tree.”

Dr. Rowe said there was no longer evidence that the earliest divergence of mammals occurred during the Triassic Period more than 200 million years ago. “The oldest date that’s based on real evidence is 30 or 40 million years younger than that,” he said. “It helps more accurately calibrate the mammalian tree of life.”

Not everyone agrees. “It’s a very great work, but I don’t think I’m totally convinced that is the case,” said Jin Meng, the curator of fossil mammals at the American Museum of Natural History in New York.

Dr. Meng is a member of a team that in the last couple of years has described more recent species of haramiyids that lived in China about 160 million years ago. The well-preserved Chinese fossils, nearly complete, possessed the characteristics of true mammals, Dr. Meng and his colleagues said.

The mammalian characteristics include the absence of a jawbone trough, Dr. Meng said in an interview. “If we accept the conclusion of this study, many of those mammalian structures must have evolved independently,” he said. “I still think the other hypotheses remain alive.”

New hadrosaur dinosaur discovery

This 13 November 2015 video is called New Duck-Billed Dinosaur found, Probrachylophosaurus – Should it be used in Jurassic World 2?

From Gizmodo.com in the USA:

This New Hadrosaur Species Is A Classic Missing Link

Kiona Smith-Strickland

11/15/15 7:06pm

A new dinosaur species sheds some light on how duck-billed dinosaurs got their crests. Paleontologists say Probrachylophosaurus bergei is a missing link between two other species, and it fills in vital pieces of the story of how crests evolved.

Probrachylophosaurus bergei is a hadrosaur, one of the large crested herbivores that roamed the Earth – mostly on their hind legs – during the late Cretaceous period. Hadrosaurs are best known for their duck-like bills and their frilled, crested skulls, and now scientists know a little more about how those distinctive crests evolved.

The fossils’ age put Probrachylophosaurus right in the middle of two hadrosaur species: the older Acristavus, which had no crest on its skull, and the more recent Brachylophosaurus, which had a large, well-developed crest. “So we would predict that its crest would be intermediate between these species. And it is,” said Elizabeth Freedman Fowler, the Montana State University paleontologist who unearthed the first Probrachylophosaurus fossils in 2007 and has studied them ever since.

81 million years ago, a hadrosaur called Acristavus roamed the Late Cretaceous coastal plain that is now Montana. Unlike its descendants, Acristavus had a flat skull with no sign of a crest – but by 79 million years ago, its descendants had evolved small, triangular crests that stuck up from their skulls just slightly, right above their eyes. Otherwise, their skulls weren’t very different from their ancestor, Acristavus. This small-crested species is now called Probrachylophosaurus.

By 77.5 million years ago, those small triangular crests had evolved further, into large, flat, paddle-shaped crests covering the back portion of the top of their skulls. Paleontologists now call these hadrosaurs Brachylophosaurus, and aside from the crests, their skulls are very similar to Acristavus and Probrachylophosaurus.

It’s a classic example of a “missing link” in a field where things seldom fall into place so neatly. “It is a perfect example of evolution within a single lineage of dinosaurs over millions of years,” said Freedman Fowler. She published her findings in the journal PLOS One.