Category: animals

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.

Paleontologists discover complete Saurornitholestes langstoni specimen

Illustration by Jan Sovak

Discovery provides valuable insight into evolution of theropod dinosaurs around the world

A small, feathered theropod dinosaur, Saurornitholestes langstoni was long thought to be so closely related to Velociraptor mongoliensis that some researchers called it Velociraptor langstoni — until now.

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The discovery of a nearly complete dromaeosaurid Saurornitholestes langstoni specimen is providing critical information for the evolution of theropod dinosaurs, according to new research by a University of Alberta paleontologist.

The 76-million-year-old species was long thought to be so closely related to Velociraptor from Mongolia that some researchers even called it Velociraptor langstoni–until now.

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The landmark discovery was made by world-renowned paleontologists Philip Currie and Clive Coy from the University of Alberta and David Evans, James and Louise Temerty Endowed Chair of Vertebrate Palaeontology at the Royal Ontario Museum. The research illustrates how Saurornitholestes differs from Velociraptor. Importantly, the research also identifies a unique tooth evolved for preening feathers and provides new evidence that the dromaeosaurid lineage from North America that includes Saurornitholestes is distinct from an Asian lineage that includes the famous Velociraptor.

“Palaeontology in general is a gigantic puzzle where most of the pieces are missing. The discovery and description of this specimen represents the recovery of many pieces of the puzzle,” said Currie, professor in the Department of Biological Sciences and Canada Research Chair in Dinosaur Paleobiology. “This ranks in the top discoveries of my career. It is pretty amazing.”

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Another piece of the puzzle

Saurornitholestes is a small, feathered carnivorous dinosaur within the dromaeosaurid family (also known as “raptors”) that was previously known from fragmentary remains. Discovered by Coy in Dinosaur Provincial Park in 2014, the new skeleton is remarkably complete and exquisitely preserved, with all the bones (except for the tail) preserved in life position. The new research, which focuses on the skull, shows that the North American form has a shorter and deeper skull than the Velociraptor. At the front of the skull’s mouth, the researchers also discovered a flat tooth with long ridges, which was likely used for preening feathers. The same tooth has since been identified in Velociraptor and other dromaeosaurids.

“Because of their small size and delicate bones, small meat-eating dinosaur skeletons are exceptionally rare in the fossil record. The new skeleton is by far the most complete and best-preserved raptor skeleton ever found in North America. It’s a scientific goldmine,” said Evans.

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The study also establishes a distinction between dromaeosaurids in North America and Asia. “The new anatomical information we have clearly shows that the North American dromaeosaurids are a separate lineage from the Asian dromaeosaurids, although they do have a common ancestor,” said Currie. “This changes our understanding of intercontinental movements of these animals and ultimately will help us understand their evolution.”

Future research will investigate the remainder of the skeleton as well as additional analyses on the relationships between dromaeosaurids.

The paper, “Cranial Anatomy of New Specimens of Saurornitholestes langstoni (Dinosauria, Theropoda, Dromaeosauridae) from the Dinosaur Park Formation (Campanian) of Alberta,” was published in The Anatomical Record (doi: 10.1002/ar.24241).

Dinosaur-Era Shark Fossil Discovered in Kansas

Credit: (Image provided by Kenshu Shimada/DePaul University and Sternberg Museum of Natural History)

The shark is estimated to be nearly 17 feet or over 5 meters long

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CHICAGO — A 91-million-year-old fossil shark newly named Cretodus houghtonorum discovered in Kansas joins a list of large dinosaur-era animals. Preserved in sediments deposited in an ancient ocean called the Western Interior Seaway that covered the middle of North America during the Late Cretaceous period (144 million to 66 million years ago), Cretodus houghtonorum was an impressive shark estimated to be nearly 17 feet or slightly more than 5 meters long based on a new study appearing in the Journal of Vertebrate Paleontology.

The fossil shark was discovered and excavated in 2010 at a ranch near Tipton, Kansas, in Mitchell County by researchers Kenshu Shimada and Michael Everhart and two central Kansas residents, Fred Smith and Gail Pearson. Shimada is a professor of paleobiology at DePaul University in Chicago. He and Everhart are both adjunct research associates at the Sternberg Museum of Natural History, Fort Hays State University in Hays, Kansas. The species name houghtonorum is in honor of Keith and Deborah Houghton, the landowners who donated the specimen to the museum for science.

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Although a largely disarticulated and incomplete skeleton, it represents the best Cretodus specimen discovered in North America, according to Shimada. The discovery consists of 134 teeth, 61 vertebrae, 23 placoid scales and fragments of calcified cartilage, which when analyzed by scientists provided a vast amount of biological information about the extinct shark. Besides its estimated large body size, anatomical data suggested that it was a rather sluggish shark, belonged to a shark group called Lamniformes that includes modern-day great white and sand tiger sharks as distant cousins, and had a rather distinct tooth pattern for a lamniform shark, the researchers said.

“Much of what we know about extinct sharks is based on isolated teeth, but an associated specimen representing a single shark individual like the one we describe provides a wealth of anatomical information that in turn offers better insights into its ecology,” said Shimada, the lead author on the study.

“As important ecological components in marine ecosystems, understanding about sharks in the past and present is critical to evaluate the roles they have played in their environments and biodiversity through time, and more importantly how they may affect the future marine ecosystem if they become extinct,” he said.

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During the excavation, Shimada and Everhart believed they had a specimen of Cretodus crassidens, a species originally described from England and subsequently reported commonly from North America. However, not even a single tooth matched the tooth shape of the original Cretodus crassidens specimen or any other known species of Cretodus, Shimada said.

“That’s when we realized that almost all the teeth from North America previously reported as Cretodus crassidens belong to a different species new to science,” he noted.

The growth model of the shark calibrated from observed vertebral growth rings indicates that the shark could have theoretically reached up to about 22 feet (about 6.8 meters).

“What is more exciting is its inferred large size at birth, almost 4 feet or 1.2 meters in length, suggesting that the cannibalistic behavior for nurturing embryos commonly observed within the uteri of modern female lamniforms must have already evolved by the late Cretaceous period,” Shimada added.

Furthermore, the Cretodus houghtonorum fossil intriguingly co-occurred with isolated teeth of another shark, Squalicorax, as well as with fragments of two fin spines of a yet another shark, a hybodont shark, the researchers said.

“Circumstantially, we think the shark possibly fed on the much smaller hybodont and was in turn scavenged by Squalicorax after its death,” said Everhart.

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Discoveries like this would not be possible without the cooperation and generosity of local landowners, and the local knowledge and enthusiasm of amateur fossil collectors, according to the authors.

“We believe that continued cooperation between paleontologists and those who are most familiar with the land is essential to improving our understanding of the geologic history of Kansas and Earth as a whole,” said Everhart.

The new study, “A new large Late Cretaceous lamniform shark from North America with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus,” will appear in the forthcoming issue of the Journal of Vertebrate Paleontology and is online at https://doi.org/10.1080/02724634.2019.1673399.

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Sources:
Kenshu Shimada
kshimada@depaul.edu
773-325-3697

Michael J. Everhart
mike@oceansofkansas.com
316-788-1354

Media Contact:
Russell Dorn
rdorn@depaul.edu
312-362-7128

Animals can lie to themselves too

Like Humans, Crayfish Talk a Tough Game

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Self-deception like this seems very human. Now, thanks to a recent study led by an Arizona State University biologist, for the first time we know that it happens in the animal kingdom, too.

Crayfish are some of the most aggressive creatures on earth. They fight with big claws capable of doing real damage. But sometimes there’s not much muscle under the bravado.

“What males are doing is making as little crappy muscle as possible, which is energetically saving,” said Michael Angilletta, a biology professor in the School of Life Sciences.

It’s like buying designer knockoffs. You save a lot of money, and most people can’t tell the difference. In the case of crayfish, you make a big claw without much muscle, and you put crappy muscle on it to boot. Everyone sees you wave your big claw and they presume that you’re a powerful crayfish.

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“Since they signal to each other before fighting, this is a way they can convince someone to back down without fighting,” Angilletta said. “Importantly, this only works if there’s enough crayfish out there that have big claws that are actually strong. If you accidentally fight one of those and call a bluff, you’re going to lose a claw.”

In the crayfish world, losing a claw is a disaster: It takes up to two years for a claw to regenerate. In the meantime, no one is mating with anyone who has a puny claw. 

Angilletta and his co-authors have been studying self-deception in crayfish for about 10 years. In 2006 they accidentally discovered that many crayfish with big claws were quite weak. There was about a tenfold variation.

“You would go, ‘Oh, this (pinch) is going to hurt,’ but it doesn’t hurt at all,” Angilletta said. “The question is are they not trying, or are they really not strong? And it’s repeatable from day after day with the same individuals.”

They combined mathematical modeling with an experiment to show that crayfish meet the criteria for self-deception. This approach opens up the possibility of studying self-deception in nonhuman animals, without being able to talk to them. They used 97 adult males, staging fights between 20 select crayfish and 77 opponents.

“How do we know what a crayfish would do if it knows whether it’s weak or it’s strong?” Angilletta asked. “If it knows that (it has a weak claw), it should actually be less aggressive.”

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It might escalate up to the point of a fight, and then run away. The probability that a crayfish engaged in a fight depended on two factors: the relative size of its claws and the expected difference in force. How do they know how strong (or not) they are? Crayfish use claws to deter predators, defend territory and capture prey. They have a pretty good idea of how strong their own claws are. They’re also skilled at assessing their size versus an opponent’s. They can even recognize previous opponents.

So natural selection has given them an ability to detect size and identity. Given that they have those abilities, it naturally follows that they have an ability to gauge strength when knowing it will improve decisions.

“In our population of crayfish, deceptive signalers largely ignored their own strength when escalating or evading aggression,” Angilletta said. “If this benefit of heightened aggression outweighs any long-term cost, natural selection should favor individuals who escalate aggression through self-deception.”

In other words, they buy into their own bluff. Angilletta teaches a biology course on human behavior called “Why people steal, cheat, and lie,” which explores the ecological and evolutionary causes of selfishness and cooperation in human societies.

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“What’s new about this study is that if you’re ever in a situation where I’m lying to you, there’s also a possibility I’m selling my lie exceptionally well because I’ve convinced myself that it’s true,” he said. “That’s because of self-deception. It’s very common in psychology but it’s not really that much in biology because we’re usually thinking about nonhuman animals and we don’t know what they’re thinking. We have a hard time understanding what they know and don’t know.”

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The paper was published last summer in Behavioral Ecology.

Video Credits:  Ken Fagan, ASU

Photo Credit: Charlie Leight, ASU

About ASU

Arizona State University has developed a new model for the American Research University, creating an institution that is committed to access, excellence and impact. ASU measures itself by those it includes, not by those it excludes. As the prototype for a New American University, ASU pursues research that contributes to the public good, and ASU assumes major responsibility for the economic, social and cultural vitality of the communities that surround it.