Tag: Dinosaurs

Dinosaur Embryos

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Eggs Took 3 to 6 Months to Hatch

Research on the teeth of fossilized dinosaur embryos indicates that the eggs of non-avian dinosaurs took a long time to hatch–between about three and six months. The study, led by scientists at Florida State University, the American Museum of Natural History, and the University of Calgary, was published today in the Proceedings of the National Academy of Sciences and finds that contrary to previous assumptions, dinosaur incubation is more similar to that of typical reptiles than of birds. The work suggests that prolonged incubation may have affected dinosaurs’ ability to compete with more rapidly generating populations of birds, reptiles, and mammals following the mass extinction event that occurred 65 million years ago.

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Credit: © AMNH/M. Ellison
This is a photo of a hatchling Protoceratops andrewsi fossil from the Gobi Desert Ukhaa Tolgod, Mongolia.
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“We know very little about dinosaur embryology, yet it relates to so many aspects of development, life history, and evolution,” said study co-author Mark Norell, Macaulay Curator of Paleontology at the American Museum of Natural History. “But with the help of advanced tools like CT scanners and high-resolution microscopy, we’re making discoveries that we couldn’t have imagined 20 years ago. This work is a great example of how new technology and new ideas can be brought to old problems.”

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Because birds are living dinosaurs, scientists have long assumed that the duration of dinosaur incubation was similar to birds, whose eggs hatch within 11 to 85 days. The research team tested this theory by looking at the fossilized teeth of two extremely well-preserved ornithischian dinosaur embryos on each end of the size spectrum: Protoceratops–a pig-sized dinosaur found by Norell and colleagues in the Mongolian Gobi Desert, whose eggs were quite small at 194 grams, or a little less than half of a pound–and Hypacrosaurus, a very large duck-billed dinosaur found in Alberta, Canada, with eggs weighing more than 4 kilograms, or nearly 9 pounds. First, the researchers scanned the embryonic jaws of the two dinosaurs with computed tomography (CT) at the Museum’s Microscopy and Imaging Facility to visualize the forming dentitions. Then they used an advanced microscope to look for and analyze the pattern of “von Ebner” lines–growth lines that are present in the teeth of all animals, humans included. This study marks the first time that these growth lines have been identified in dinosaur embryos.

“These are the lines that are laid down when any animal’s teeth develops,” said lead author and Florida State University professor Gregory Erickson. “They’re kind of like tree rings, but they’re put down daily. And so we could literally count them to see how long each dinosaur had been developing.”

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Using this method, the scientists determined that the Protoceratops embryos were about three months old when they died and the Hypacrosaurus embryos were about six months old. This places non-avian dinosaur incubation more in line with that of their reptilian cousins, whose eggs typically take twice as long as bird eggs to hatch–weeks to many months. The work implies that birds likely evolved more rapid incubation rates after they branched off from the rest of the dinosaurs. The authors note that the results might be quite different if they were able to analyze a more “bird-like” dinosaur, like Velociraptor. But unfortunately, very few fossilized dinosaur embryos have been discovered.

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“A lot is known about growth in dinosaurs in their juvenile to adult years,” said co-author Darla Zelenitsky, from the University of Calgary. “Time within the egg is a crucial part of development with major biological ramifications, but is poorly understood because dinosaur embryos are rare.”

The study also has implications for dinosaur extinction. Prolonged incubation exposed non-avian dinosaur eggs and attending parents to predators, starvation, and environmental disruptions such as flooding. In addition, slower embryonic development might have put them at a disadvantage compared to other animals that survived the Cretaceous-Paleogene extinction event.

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Florida State University graduate student David Kay also is an author on this paper.

This work was funded, in part, by the U.S. National Science Foundation, grant # EAR 0959029, the Macaulay Family, and the Natural Sciences and Engineering Research Council of Canada, grant # 327513-09.

AMERICAN MUSEUM OF NATURAL HISTORY (AMNH.ORG)

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The American Museum of Natural History, founded in 1869, is one of the world’s preeminent scientific, educational, and cultural institutions. The Museum encompasses 45 permanent exhibition halls, including the Rose Center for Earth and Space and the Hayden Planetarium, as well as galleries for temporary exhibitions. It is home to the Theodore Roosevelt Memorial, New York State’s official memorial to its 33rd governor and the nation’s 26th president, and a tribute to Roosevelt’s enduring legacy of conservation. The Museum’s five active research divisions and three cross-disciplinary centers support approximately 200 scientists, whose work draws on a world-class permanent collection of more than 33 million specimens and artifacts, as well as specialized collections for frozen tissue and genomic and astrophysical data, and one of the largest natural history libraries in the world. Through its Richard Gilder Graduate School, it is the only American museum authorized to grant the Ph.D. degree and the Master of Arts in Teaching degree. Annual attendance has grown to approximately 5 million, and the Museum’s exhibitions and Space Shows can be seen in venues on five continents. The Museum’s website and collection of apps for mobile devices extend its collections, exhibitions, and educational programs to millions more beyond its walls. Visit amnh.org for more information.

Tyrannosaurus rex

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Researchers learn more about teen-age T.Rex

Photo by Mike on Pexels.com
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Without a doubt, Tyrannosaurus rex is the most famous dinosaur in the world. The 40-foot-long predator with bone crushing teeth inside a five-foot long head are the stuff of legend. Now, a look within the bones of two mid-sized, immature T. rex allow scientists to learn about the tyrant king’s terrible teens as well.

In the early 2000s, the fossil skeletons of two comparatively small T. rex were collected from Carter County, Montana, by Burpee Museum of Natural History in Rockford, Illinois. Nicknamed “Jane” and “Petey,” the tyrannosaurs would have been slightly taller than a draft horse and twice as long.

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The team led by Holly Woodward, Ph.D., from Oklahoma State University Center for Health Sciences studied Jane and Petey to better understand T. rex life history.

The study “Growing up Tyrannosaurus rex: histology refutes pygmy ‘Nanotyrannus’ and supports ontogenetic niche partitioning in juvenile Tyrannosaurus” appears in the peer-reviewed journal Science Advances.

Co-authors include Jack Horner, presidential fellow at Chapman University; Nathan Myhrvold, founder and CEO of Intellectual Ventures; Katie Tremaine, graduate student at Montana State University; Scott Williams, paleontology lab and field specialist at Museum of the Rockies; and Lindsay Zanno, division head of paleontology at the North Carolina Museum of Natural Sciences. Supplemental histological work was conducted at the Diane Gabriel Histology Labs at Museum of the Rockies/Montana State University.

“Historically, many museums would collect the biggest, most impressive fossils of a dinosaur species for display and ignore the others,” said Woodward. “The problem is that those smaller fossils may be from younger animals. So, for a long while we’ve had large gaps in our understanding of how dinosaurs grew up, and T. rex is no exception.”

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The smaller size of Jane and Petey is what make them so incredibly important. Not only can scientists now study how the bones and proportions changed as T. rex matured, but they can also utilize paleohistology– the study of fossil bone microstructure– to learn about juvenile growth rates and ages. Woodward and her team removed thin slices from the leg bones of Jane and Petey and examined them at high magnification.

“To me, it’s always amazing to find that if you have something like a huge fossilized dinosaur bone, it’s fossilized on the microscopic level as well,” Woodward said. “And by comparing these fossilized microstructures to similar features found in modern bone, we know they provide clues to metabolism, growth rate, and age.”

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The team determined that the small T. rex were growing as fast as modern-day warm-blooded animals such as mammals and birds. Woodward and her colleagues also found that by counting the annual rings within the bone, much like counting tree rings, Jane and Petey were teenaged T.rex when they died; 13 and 15 years old, respectively.

There had been speculation that the two small skeletons weren’t T. rex at all, but a smaller pygmy relative Nanotyrannus. Study of the bones using histology led the researchers to the conclusion that the skeletons were juvenile T. rex and not a new pygmy species.

Instead, Woodward points out, because it took T. rex up to twenty years to reach adult size, the tyrant king probably underwent drastic changes as it matured. Juveniles such as Jane and Petey were fast, fleet footed, and had knife-like teeth for cutting, whereas adults were lumbering bone crushers. Not only that, but Woodward’s team discovered that growing T. rex could do a neat trick: if its food source was scarce during a particular year, it just didn’t grow as much. And if food was plentiful, it grew a lot.

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“The spacing between annual growth rings record how much an individual grows from one year to the next. The spacing between the rings within Jane, Petey, and even older individuals is inconsistent – some years the spacing is close together, and other years it’s spread apart,” said Woodward.

The research by Woodward and her team writes a new chapter in the early years of the world’s most famous dinosaur, providing evidence that it assumed the crown of tyrant king long before it reached adult size.

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About Oklahoma State University Center for Health Sciences

Oklahoma State University Center for Health Sciences educates osteopathic physicians, scientists, allied health professionals and health care administrators for Oklahoma with an emphasis on serving rural and underserved Oklahoma. OSU-CHS offers graduate and professional degrees with over 1,000 students enrolled in academic programs in the College of Osteopathic Medicine, the School of Allied Health, the School of Health Care Administration, the School of Biomedical Sciences, and the School of Forensic Sciences. OSU Medicine operates a network of clinics in the Tulsa area offering a multitude of specialty services including addiction medicine, cardiology, family medicine, internal medicine, pediatrics, psychiatry and women’s health. Learn more at https://health.okstate.edu.

‘Ghost’ footprints from Pleistocene era

Photo by Jon Del Rivero

ITHACA, N.Y. –

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Invisible footprints hiding since the end of the last ice age – and what lies beneath them – have been discovered by Cornell University researchers using a special type of radar in a novel way.

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The fossilized footprints reveal a wealth of information about how humans and animals moved and interacted with each other 12,000 years ago.

“We never thought to look under footprints,” said Thomas Urban, research scientist at Cornell and lead author on the study. “But it turns out that the sediment itself has a memory that records the effects of the animal’s weight and momentum in a beautiful way. It gives us a way to understand the biomechanics of extinct fauna that we never had before.”

The researchers examined the footprints of humans, mammoths and giant sloths in the White Sands National Monument in New Mexico. Using ground-penetrating radar (GPR), they were able to resolve 96% of the human tracks in the area under investigation, as well as all of the larger vertebrate tracks.

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“But there are bigger implications than just this case study,” Urban said. “The technique could possibly be applied to many other fossilized footprint sites around the world, potentially including those of dinosaurs. We have already successfully tested the method more broadly at multiple locations within White Sands.”

While these “ghost” footprints can become invisible for a short time after rain and when conditions are just right, “now, using geophysics methods, they can be recorded, traced and investigated in 3D to reveal Pleistocene animal and human interactions, history and mechanics in genuinely exciting new ways,” said co-author Sturt Manning, archaeology professor.

GPR is a nondestructive method that allows researchers to access hidden information without the need for excavation. The sensor – a kind of antenna – is dragged over the surface, sending a radio wave into the ground. The signal that bounces back gives a picture of what’s under the surface.

In addition to this biomechanical treasure trove of data, the GPR technique gives researchers a way to learn about what early humans did when they were not at a campsite or kill site, the two types of archaeological sites best known for this time period.

The study, “3-D Radar Imaging Unlocks the Untapped Behavioral and Biomechanical Archive of Pleistocene Ghost Track,” published in Scientific Reports.

For more information, see this Cornell Chronicle story.

Cornell University has dedicated television and audio studios available for media interviews supporting full HD, ISDN and web-based platforms.