Category Archives: Dinosaurs
Co-authored by Dr Gareth Dyke, Senior Lecturer in Vertebrate Palaeontology at the University of Southampton, the paper describes a new feathered dinosaur about 30 cm in length which pre-dates bird-like dinosaurs that birds were long thought to have evolved from.
Over many years, it has become accepted among palaeontologists that birds evolved from a group of dinosaurs called theropods from the Early Cretaceous period of Earth’s history, around 120-130 million years ago. Recent discoveries of feathered dinosaurs from the older Middle-Late Jurassic period have reinforced this theory.
The new ‘bird-dinosaur’ Eosinopteryx described in Nature Communications this week provides additional evidence to this effect.
“This discovery sheds further doubt on the theory that the famous fossil Archaeopteryx — or “first bird” as it is sometimes referred to — was pivotal in the evolution of modern birds,” says Dr Dyke, who is based at the National Oceanography Centre, Southampton.
“Our findings suggest that the origin of flight was much more complex than previously thought.”
The fossilised remains found in north-eastern China indicate that, while feathered, this was a flightless dinosaur, because of its small wingspan and a bone structure that would have restricted its ability to flap its wings.
The dinosaur also had toes suited to walking along the ground and fewer feathers on its tail and lower legs, which would have made it easier to run.
Dr Gareth Dyke is also Programme Leader for a new one-year MRes in Vertebrate Palaeontology, which offers potential students the chance to study the evolution and anatomy of vertebrates, in order to inform and increase our understanding of the workings of modern day creatures.
Dr Dyke’s co-authors are Pascal Godefroit of the Royal Belgian Institute of Natural Sciences, Helena Demuynck of Earth System Science Vrije Universiteit Brussel, Dongyu Hu of Paleontological Institute Shenyang Normal University China and Key Laboratory of Vegetation Ecology Northeast Normal University China, François Escuillié of Eldonia France and Philippe Claeys of Jilin University Geological Museum China.
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By Thomas Hayden
People have told Jack Horner he’s crazy before, but he has always turned out to be right. In 1982, on the strength of seven years of undergraduate study, a stint in the Marines, and a gig as a paleontology researcher at Princeton, Horner got a job at Montana State University’s Museum of the Rockies in Bozeman. He was hired as a curator but soon told his bosses that he wanted to teach paleontology. “They said it wasn’t going to happen,” Horner recalls. Four years and a MacArthur genius grant later, “they told me to do whatever I wanted to.” Horner, 65, continues to work at the museum, now filled with his discoveries. He still doesn’t have a college degree.
When he was a kid in the 1950s, dinosaurs were thought to have been mostly cold, solitary, reptilian beasts—true monsters. Horner didn’t agree with this picture. He saw in their hundreds-of-millions-of-years-old skeletons hints of sociability, of animals that lived in herds, unlike modern reptiles. Then, in the 1970s, Horner and his friend Bob Makela excavated one of the most spectacular dinosaur finds ever—a massive communal nesting site of duck-billed dinosaurs in northwest Montana complete with fossilized adults, juveniles, and eggs. There they found proof of crazy idea number one: The parents at the site cared for their young. Judging by their skeletons, the baby duckbills would have been too feeble to forage on their own.
Horner went on to find evidence suggesting that, once hatched, the animals were fast-growing (crazy idea number two) and possibly warm-blooded (that would be three), and he continues to be at the forefront of the search for ancient bits of organic matter surviving intact in fossils (number four). Add in his work as a technical consultant on the Jurassic Park movies and Horner has probably done more to shape the way we currently think about dinosaurs than any other living paleontologist.
All of which means that people are more cautious about calling him crazy these days, even when he tells them what he plans to do next: Jack Horner wants to make a dinosaur. Not from scratch—don’t be ridiculous. He says he’s going to do it by reverse-evolving a chicken. “It’s crazy,” Horner says. “But it’s also possible.”
Over the past several decades, paleontologists—including Horner—have found ample evidence to prove that modern birds are the descendants of dinosaurs, everything from the way they lay eggs in nests to the details of their bone anatomy. In fact, there are so many similarities that most scientists now agree that birds actually are dinosaurs, most closely related to two-legged meat-eating theropods like Tyrannosaurus rex and velociraptor.
But “closely related” means something different to evolutionary biologists than it does to, say, the people who write incest laws. It’s all relative: Human beings are almost indistinguishable, genetically speaking, from chimpanzees, but at that scale we’re also pretty hard to tell apart from, say, bats.
Hints of long-extinct creatures, echoes of evolution past, occasionally emerge in real life—they’re called atavisms, rare cases of individuals born with characteristic features of their evolutionary antecedents. Whales are sometimes born with appendages reminiscent of hind limbs. Human babies sometimes enter the world with fur, extra nipples, or, very rarely, a true tail. Horner’s plan, in essence, is to start off by creating experimental atavisms in the lab. Activate enough ancestral characteristics in a single chicken, he reasons, and you’ll end up with something close enough to the ancestor to be a “saurus.” At least, that’s what he pitched at this year’s TED conference, the annual technology, entertainment, and design gathering held in Long Beach, California. “When I was growing up in Montana, I had two dreams,” he told the crowd. “I wanted to be a paleontologist, a dinosaur paleontologist—and I wanted to have a pet dinosaur.”
Story Continues -> How to Hatch a Dinosaur
WASHINGTON — Tyrannosaurus rex was certainly the king of dinosaurs, but may also have been dinosaur a la king.
A team of researchers reports Friday that huge tooth marks on T. rex bones indicate the ancient giants may have cannibalized one another.
“They””re the kind of marks that any big carnivore could have made, but T. rex was the only big carnivore in western North America 65 million years ago,” Nicholas R. Longrich of Yale University said in a statement.
Longrich and colleagues report their findings in Friday””s edition of the journal PLoS ONE.
They found 17 fossils with deep V-shaped gouges of a type identified as being made by T. rex. Of those, four were remains of T. rex themselves.
It seems likely the marks were made during scavenging from a dead dinosaur, the researchers said.
“It does seem improbable that Tyrannosaurus routinely hunted full-grown members of its own species,” the researchers wrote.
However, they added, it is possible that combat led to casualties, with the dead becoming convenient sources of food for the victors. “Still, compelling evidence for predation in Tyrannosaurus remains elusive.”
Longrich and colleagues note that “cannibalism is common in nature, particularly among large carnivores” such as bears, hyenas, large cats, Komodo dragons and alligators.
Co-authors are John Horner of Montana State University, Gregory Erickson of Florida State University and Philip Currie of the University of Alberta.
By examining the type of rock in which dinosaur fossils were embedded, an often unappreciated part of the remains, scientists have determined that different species of North American dinosaurs from the Late Cretaceous period 65 million years ago occupied different environments separated by just a few miles.
Hadrosaurs or duck-billed dinosaurs, along with the small ornithopod Thescelosaurus, preferred to live along the edge of rivers, according to the research. Ceratopsians, on the other hand, which include the well-known Triceratops, preferred to be several miles inland.
The findings, which appear in the online edition of the Proceedings of the Royal Society B, give scientists a more complete picture of the distribution of different species and help explain how several large herbivores managed to coexist.
Tyler Lyson of Yale University and the Marmarth Research Foundation, along with Yale researcher Nicholas Longrich, analyzed more than 300 fossils representing more than half a dozen dinosaur species from Western Canada, Montana, Wyoming and surrounding areas.
After several years of fieldwork, Lyson began to notice a pattern to the geographical distribution of different species. He and Longrich also searched through museum collections of fossils, some of which contained information about the type of rock in which the fossils were found, and some of which still had pieces of rock attached to them that were large enough for the researchers to recognize as either sandstone or mudstone.
“We”re using what paleontologists usually throw away when excavating the fossils as clues to where these different species spent most of their time,” Lyson said.
As the sole large carnivore in the region, Tyrannosaurs rex appears to have roamed both habitats, most likely feeding on large herbivores. However, the team discovered that hadrosaurs and Thescelosaurus fossils were more often found in sandstone, which occurs along riverbanks, whereas ceratopsians were likely to be embedded in mudstone from the floodplains.
“We didn”t really think about distribution between different species before now,” Longrich said. “But depending on what type of rock you look at, you get a very different picture of the community that lived there.”
The study also shows that the dinosaurs had specialized eating habits (something about which very little is known), and likely fed on different types of plants found in each environment, Longrich said.
“This opens up the possibility of finding new species if we search different types of rock,” Longrich said. “It also emphasizes the importance of recording data about the rock in which fossils are preserved, which can give us important clues as to the paleoecology of these animals.”
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Yale University.
- T. R. Lyson, N. R. Longrich. Spatial niche partitioning in dinosaurs from the latest cretaceous (Maastrichtian) of North America. Proceedings of the Royal Society B: Biological Sciences, 2010; DOI: 10.1098/rspb.2010.1444
Oldest Evidence of Dinosaurs in Footprints: Dinosaur Lineage Emerged Soon After Massive Permian Extinction
Top: This is a reconstruction of cat-sized stem dinosaur Prorotodactylus isp. found in Stryczowice, Poland that was a quadruped with a dinosaur-like gait and orientation of the toes. Bottom: The 250 million year old footprints of Prorotodactylus isp. from the Early Olenekian of Stryczowice, Poland show reduced digits I and V and parallel three middle digits, traits of the dinosaur-lineage. The gait, though, was quadrapedal. These are the oldest known fossils of the dinosaur lineage. (Credit: Grzegorz Niedźwiedzki)
The oldest evidence of the dinosaur lineage — fossilized tracks — is described in Proceedings of the Royal Society B. Just one or two million years after the massive Permian-Triassic extinction, an animal smaller than a house cat walked across fine mud in what is now Poland.
This fossilized trackway places the very closest relatives of dinosaurs on Earth about 250 million years ago — 5 to 9 million years earlier than previously described fossilized skeletal material has indicated. The paper also described the 246-million-year-old Sphingopus footprints, the oldest evidence of a bipedal and large-bodied dinosaur.
“We see the closest dinosaur cousins immediately after the worst mass extinction,” says Stephen Brusatte, a graduate student affiliated with the Division of Paleontology at the American Museum of Natural History. “The biggest crisis in the history of life also created one of the greatest opportunities in the history of life by emptying the landscape and making it possible for dinosaurs to evolve.”
The new paper analyzes three sets of footprints from three different sites in the Holy Cross Mountains of central Poland. The sites, all quarries within a 25-mile radius of each other, are windows into three ecosystems because they represent different times periods. The Stryczowice trackway is the oldest at 250 million years. The Baranów trackway is the most recent at 246 million years of age while the Wióry trackway is sandwiched in time between the others.
Because footprints are only an imprint of a small part of the skeleton, identification of trackmakers is often tricky. Luckily, dinosaurs have a very distinctive gait, especially when compared to their diapsid relatives (the evolutionary group that includes birds, reptiles, and extinct lineages) like crocodiles and lizards. While lizards and crocodiles have a splayed walking style, dinosaurs place their two feet closer together. The footprints at all three Polish sites show this feature as well as indisputable dinosaur-like features, including three prominent central toes and reduced outer two toes, a parallel alignment of these three digits (a bunched foot), and a straight back edge of footprints, additional evidence of a dinosaur-like simple hinged ankle.
Because all of these features are seen in footprints at the oldest site, Brusatte and colleagues conclude that the Stryczowice prints — which are only a few centimeters in length — are the oldest evidence of the dinosaur lineage. These dinosaurs, though, are considered “stem dinosaurs,” or the immediate relatives of dinosaurs not part of the slightly more derived clade that technically defines dinosaurs. Also, this animal did walk on all four limbs, an abnormal posture for early dinosaurs and their close relatives, although it appears that its forelimbs were already being reduced to more dinosaur-like proportions since the footprints overstep handprints.
The Baranów and Wióry trackways show changes early in the evolutionary history of dinosaurs. Wióry at 248-249 million years ago shows slight diversification in the types of tracks, but all tracks remain quadrupedal. Footprints from Baranów at 246 million years ago, however, may be the earliest evidence of moderately large-bodied and bipedal true dinosaurs. These tracks, which are called Sphingopus, are 15 centimeters long.
“Poland is a new frontier for understanding the earliest evolution of dinosaurs,” says Grzegorz Niedźwiedzki of the University of Warsaw and the Polish Academy of Sciences, who led the project and has been excavating footprints from the three sites for nearly a decade. “It used to be that most of the important fossils were from Argentina or the southwestern U.S., but in Poland we have several sites that yield footprints and bones from the oldest dinosaurs and their closest cousins, stretching throughout the entire Triassic Period.”
Finally, although the dinosaur group emerged soon after the Permian extinction, dinosaur-like tracks are rare in the footprint assemblages, representing only 2-3 percent of the prints discovered as opposed to 40-50 percent for crocodile-like archosaurs. Dinosaurs became more abundant tens of millions of years later.
“For the first 20-50 million years of dinosaur history, dinosaurs and their closest relatives were living in the shadow of their much more diverse, successful, and abundant crocodile-like cousins,” says Brusatte. “The oldest dinosaurs were small and rare.”
In addition to Brusatte and Niedźwiedzki, Richard Butler of the Bayerische Staatssammlung für Paläontologie und Geologie in Germany was an author of the paper. Brusatte is also affiliated with Columbia University. The research was funded in part by the National Science Foundation, the Percy Sladen Fund, the Alexander von Humboldt Research Fellowship, and the University of Warsaw.
- Stephen L. Brusatte, Grzegorz Niedźwiedzki, Richard J. Butler. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic. Proceedings of the Royal Society B, 2010; DOI: 10.1098/rspb.2010.1746
Dinosaur bones have rounded ends with rough surfaces that mark where blood vessels fed large amounts of cartilage in the joint. The cartilage could have added 10 percent or more to the height of a dinosaur. (Credit: Casey Holliday/University of Missouri)
It might seem obvious that a dinosaur”s leg bone connects to the hip bone, but what came between the bones has been less obvious. Now, researchers at the University of Missouri and Ohio University have found that dinosaurs had thick layers of cartilage in their joints, which means they may have been considerably taller than previously thought. The study is being published this week in the journal PLoS ONE (Public Library of Science).
“Our study of the limbs of modern-day relatives of dinosaurs shows that dinosaurs were significantly taller than original estimates,” said Casey Holliday, lead author of the study and an anatomy professor in the MU School of Medicine. “The ends of many dinosaurs” long bones, which include leg bones such as the femur or tibia, are rounded and rough and lack major articulating structures like condyles, which are bony projections. This indicated that very thick cartilages formed these structures, and therefore the joints themselves, and would have added significant height to certain dinosaurs. This study offers new data into how and why reptiles, and mammals, such as humans, build their joints with such different amounts of bone and cartilage.”
Holliday and Lawrence Witmer, a professor of anatomy at the Ohio University College of Osteopathic Medicine, conducted research on ostriches and alligators, the closest, modern-day relatives of dinosaurs, and then studied the fossilized limbs of different dinosaurs including Tyrannosaurus rex, Allosaurus, Brachiosaurus and Triceratops. The team determined that the lengths of alligators” and ostriches” limbs included between 6 and 10 percent cartilage.
Using a “cartilage correction factor,” Holliday determined that many theropod dinosaurs, such as Tyrannosaurus, were only modestly taller whereas ornthischian and sauropod dinosaurs, such as Triceratops and Brachiosaurus, may have been 10 percent taller or more. For example, Brachiosaurus, previously thought to be 42 feet tall, may actually have been more than a foot taller with the additional joint cartilages.
“This study is significant because it shows that bones can”t always speak for themselves,” Witmer said. “To understand how dinosaurs moved, we need to analyze the bones as they were inside their bodies, including their cartilage. The dinosaur bones mounted in museums don”t accurately reflect what the animals actually had in their bodies in life because the cartilage caps were lost along with the other soft tissues. Knowing how much cartilage was lost allows us to better restore the structure of a living dinosaur bone, which then allows us to better understand how dinosaurs moved and lived”
Understanding the structures of the soft tissues in dinosaurs might also have implications for their speed and posture. While an increase in limb length typically means a taller dinosaur, it could also mean a faster or slower animal, depending on how it affects the skeleton, Holliday said. This finding could have major implications on how scientists currently understand dinosaur anatomy.
Dinosaur bones are different than the bones of mammals, including humans. Mammals have small protrusions at the end of each bone that help it connect with another bone at a joint, like two puzzle pieces. The bones are linked by a very thin layer of cartilage, which provides padding in the joint, but often wears down leading to painful conditions like arthritis.
Story Continues -> http://www.sciencedaily.com/releases/2010/09/100930171418.htm
Koen Stein holding Magyarosaurus lower leg bones. In the background, the lower leg of the Argentinosaurus dinosaur exhibition at the Museum Koenig in Bonn. (Credit: Jose Carballido / Koen Stein / University of Bonn)
In 1895, the sister of an eccentric palaeontologist called Franz Baron Nopcsa discovered small dinosaur bones on their family estate in Transylvania. Nopcsa interpreted these as the remains of dwarfed animals that had once lived on an island. Among these finds were a number of bones belonging to a sauropod dinosaur which Nopcsa named Magyarosaurus dacus, after his native country.
A team of scientists led by Koen Stein and Professor Dr. Martin Sander from the University of Bonn, decided to cut up the fossil bones of the dwarfed dinosaur and study their microstructure.
“It’s astonishing that the microanatomy of these bones has been preserved for us to study after 70 million years,” says Stein, who carried out the research as part of his PhD studies. “Bone is a living tissue, and throughout an animal’s life it is constantly dissipating and building up again.” Humans, for example, have completely resorbed and rebuilt their skeleton by the time they are fully grown. This also occurred in sauropod dinosaurs. “We were able to distinguish these rebuilding features in Magyarosaurus, which prove that the little dinosaur was fully grown,” Stein explains.
A dwarf among giants
Over the years, palaeontologists have frequently debated the question of whether or not the Magyarosaurus was a dwarf. Martin Sander, spokesperson of the Research Group on Sauropod Biology funded by Germany’s central research funding foundation the DFG (Deutsche Forschungsgemeinschaft) notes, “An animal the size of a horse may not seem like a dwarf to most people but, in sauropod terms, it’s tiny!”
When Magyarosaurus was discovered in Transylvania (then part of the Austro-Hungarian Empire), the palaeontologist Nopcsa advanced the idea that Magyarosaurus was an island dwarf, but he could not prove it back then, at the beginning of the 20th century. Many discoveries have since indicated that his theory might be correct, especially the fossils of dwarf elephants and hippopotamuses found on Mediterranean islands like Sicily, Malta and Cyprus.
However, scientists first pursued a different theory. For in the subsequent decades, other researchers found big sauropod bones on the Transylvanian site. They therefore concluded that Magyarosaurus was simply a youngster, while the larger bones came from fully grown adults.
The study now being published provides conclusive evidence that Nopcsa’s hunch had been right all along. “Our study shows that dinosaurs on islands were subject to the same ecological and evolutionary processes that shape modern mammals,” explains Martin Sander. “We were also able to demonstrate that the bigger bones found in that area belong to a different dinosaur species.” Whether they come from stray animals who swam to the island from the mainland, or from large ancestors of the dwarf Magyarosaurus, remains a secret shrouded in the mists of pre-historic time.
The team’s findings are now to appear in the science journal Proceedings of the National Academy of Sciences.
Adapted from materials provided by University of Bonn.
- K. Stein, Z. Csiki, K. C. Rogers, D. B. Weishampel, R. Redelstorff, J. L. Carballido, P. M. Sander. Small body size and extreme cortical bone remodeling indicate phyletic dwarfism in Magyarosaurus dacus (Sauropoda: Titanosauria). Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1000781107
Rapid and bizarre switches suggest dinos had birds beat for plumage diversity.
Charles Q. Choi
Published April 28, 2010
Farmers in northeastern China have unearthed two roughly 125-million-year-old specimens of the dinosaur Similicaudipteryx, a member of the group called the oviraptorosaurs, which are believed to be ancestors of birds.
The species, most likely a plant-eater, was first described in 2008. It had robust jaws similar to those of other oviraptorosaurs, but with two unusually large buck teeth.
The two new fossils belong to a pigeon-size juvenile dinosaur thought to be just a year or two old and a three- to four-year-old duck-size youth.
The younger animal’s fossil included short ribbonlike feathers. On its tail, each feather was just 1.6 inches (4 centimeters) long, while on its arms a typical feather was less than 0.8 inch (2 centimeters) long. (Related: “Dino-Era Feathers Found Encased in Amber.”)
By contrast, the older dinosaur sported long quills, with each tail feather measuring 13.7 inches (35 centimeters) long and a typical arm feather measuring roughly 9.8 inches (25 centimeters) long.
The findings suggest feathered dinosaurs might have undergone a flurry of changes as they matured—unlike anything seen in modern birds, said study co-author Xing Xu of the Chinese Academy of Sciences in Beijing.
Dinosaur’s Ribbonlike Feathers “Really Bizarre”
Modern birds continuously replace old feathers with new ones. But birds completely change the types of feathers in their coats just once their entire lives: when they switch from warm down to their adult plumage.
Very young dinosaurs are thought to have been covered in down, so the new find suggests that dinosuars went through at least three stages of feather types: full down, to a mix of down and “ribbons,” to down and quills.
The long quills on the older Similicaudipteryx are much like those seen on modern birds, and they might have served as ornaments or to help the dinosaur balance itself as it ran. (Related: “First Dinosaur Feathers for Show, Not Flight?”)
The younger dinosaur’s ribbonlike feathers are superficially similar to some specialized plumes seen today, for example, on birds of paradise. But the ancient feathers are actually a type that has been lost in the course of evolution, and the role they played on the younger juvenile remains unknown.
These extinct feathers would not have been useful for warmth, for example, given how flat they are, Xu said.
While the “ribbons” might have served as ornaments, “in modern animals, structures used for display generally develop relatively late, when the animal is mature, for attracting mates,” he added. “Their appearance here is at the wrong stage—it’s really bizarre.”
Similicaudipteryx’s odd changes suggest that early birds and feathered dinosaurs experimented with a diversity of feather types and a variety of ways to use them, “which only later stabilized to the more conservative system we see now with modern birds,” Xu said.
“There were very, very strange structures in the history of feathers.”
The feathered dinosaurs are described in this week’s issue of the journal Nature
A 95 million-year-old fossilized jaw discovered in Texas has been identified as a new genus and species of flying reptile, Aetodactylus halli, says paleontologist Timothy S. Myers, who identified and named Aetodactylus halli. The rare pterosaur — literally winged lizard — is also one of the youngest members of the pterosaur family Ornithocheiridae in the world. It’s only the second ornithocheirid ever documented in North America, says Myers, a postdoctoral fellow at Southern Methodist University, Dallas. (Credit: Illustration by Karen Carr)
A 95 million-year-old fossilized jaw discovered in Texas has been identified as a new genus and species of flying reptile, Aetodactylus halli.
Aetodactylus halli is a pterosaur, a group of flying reptiles commonly referred to as pterodactyls.
The rare pterosaur — literally a winged lizard — is also one of the youngest members in the world of the pterosaur family Ornithocheiridae, according to paleontologist Timothy S. Myers, who identified and named Aetodactylus halli. The newly identified reptile is only the second ornithocheirid ever documented in North America, says Myers, a postdoctoral fellow in the Huffington Department of Earth Sciences at Southern Methodist University in Dallas.
Aetodactylus halli would have soared over what is now the Dallas-Fort Worth area during the Cretaceous Period when much of the Lone Star state was under water, covered by a vast ancient sea.
While rare in North America, toothed pterosaurs belonging to the Ornithocheiridae are a major component of Cretaceous pterosaur faunas elsewhere in the world, Myers says. The Texas specimen — a nearly complete mandible with most of its 54 teeth missing — is definitively younger than most other ornithocheirid specimens from Brazil, England and China, he says. It is five million years younger than the only other known North American ornithocheirid.
Myers describes the new species in the latest issue of the Journal of Vertebrate Paleontology. Go to www.smuresearch.com to see illustrations of Aetodactylus halli and the Cretaceous marine environment, an image of the fossilized jaw and links to more information.
Myers named the pterosaur Aetodactylus halli after Lance Hall, a member of the Dallas Paleontological Society who hunts fossils for a hobby. Hall found the specimen in 2006 in North Texas. It was embedded in a soft, powdery shale exposed by excavation of a hillside next to a highway. The site was near the city of Mansfield, southwest of Dallas. Hall donated the specimen to SMU.
Pterosaurs ruled the skies from the late Triassic, more than 200 million years ago, to the end of the Cretaceous, about 65 million years ago, when they went extinct. They represent the earliest vertebrates capable of flying.
Fossil hunter saw long row of teeth sockets
The Aetodactylus halli jaw was discovered in the geologic unit known as the Eagle Ford Group, which comprises sediments deposited in a shallow sea, Myers says. Outcrop of the Eagle Ford Group extends northward from southwestern Texas into southern Oklahoma and southwestern Arkansas.
“I was scanning the exposure and noticed what at first I thought was a piece of oyster shell spanning across a small erosion valley,” Hall recalls of the discovery. “Only about an inch or two was exposed. I almost passed it up thinking it was oyster, but realized it was more tan-colored like bone. I started uncovering it and realized it was the jaw to something — but I had no idea what. It was upside down and when I turned over the snout portion it was nothing but a long row of teeth sockets, which was very exciting.”
SMU vertebrate paleontologist Louis L. Jacobs, a dinosaur expert internationally recognized for his fossil discoveries in Texas and Africa, and SMU paleontologist Michael J. Polcyn, recognized for his expertise on the extinct marine reptiles called mosasaurs, both told Hall it was a pterosaur and an important find.
Unique jaw differs from others
The 38.4-centimeter Aetodactylus jaw originally contained 54 slender, pointed teeth, but only two remain in their sockets, Myers says. The lower teeth were evenly spaced and extended far back along the jaw, covering nearly three quarters of the length of the mandible. The upper and lower teeth interlaced when the jaws were closed.
In Aetodactylus, changes in tooth size along the jaw follow a similar pattern to those of other ornithocheirids. However, Aetodactylus differs from all other ornithocheirids in that its jaws were thin and delicate, with a maximum thickness not much greater than 1 centimeter, Myers says. But the specimen does compare favorably with Boreopterus, a related pterosaur from the Early Cretaceous of China, in terms of the number of teeth present in the lower jaw, he says.
Myers has estimated the wingspan around roughly 3 meters, or about 9 feet, indicating Aetodactylus would have been a “medium-sized” pterosaur, he says. While it’s not known how Aetodactylus died, at the time of death the reptile was flying over the sea and fell into the water, perhaps while fishing, Jacobs says.
Find hints at new diversity of pterosaurs
North American pterosaurs that date from the Cretaceous are all toothless, except for Aetodactylus and Coloborhynchus, Myers says. The thinness of the jaws, the upward angle of the back half of the mandible and the lack of a pronounced expansion of the jaw tips indicate that Aetodactylus is different from other ornithocheirids and represents a new genus and species of pterosaur.
“Discovery of another ornithocheirid species in Texas hints at a diversity of pterosaurs in the Cretaceous of North America that wasn’t previously realized,” Myers says. “Aetodactylus also represents one of the final occurrences of ornithocheirids prior to the Late Cretaceous transition to pterosaur faunas that were dominated by the edentulous, or toothless, species.”
Texas now claims the only two of their kind
Much of Texas was once submerged under the Western Interior Seaway. The massive sea split North America from the Gulf of Mexico to the Arctic Ocean.
On shore, the terrain was flat and flowering plants were already dominating flora communities in this part of North America, according to paleobotanist Bonnie Jacobs, associate professor of Earth Sciences at SMU.
“There were still conifers and ferns as well, but mostly of the sort that had tiny needle leaves, like junipers, says Bonnie Jacobs. “Sycamores and their relatives would have been among the flowering plants.”
The first ornithocheirid remains from North America, discovered in Fort Worth, were described by former SMU student Young-Nam Lee and donated by amateur collector Chris Wadleigh, says SMU’s Louis Jacobs.
“The ancient sea that covered Dallas provided the right conditions to preserve marine reptiles and other denizens of the deep, as well as the delicate bones of flying reptiles that fell from their flight to the water below,” says Louis Jacobs, a professor in SMU’s Huffington Department of Earth Sciences. “The rocks and fossils here record a time not well represented elsewhere in North America. That’s why two species of ornithocheirids have been found here but nowhere else, and that’s why discoveries of other new fossils are sure to be made by Lance Hall and other fossil lovers.”
The research was funded by the Roy M. Huffington Department of Earth Sciences at SMU and SMU’s Institute for the Study of Earth and Man.
- Timothy Myers. A new ornithocheirid pterosaur from the Upper Cretaceous (Cenomanian-Turonian) Eagle Ford Group of Texas. Journal of Vertebrate Paleontology, 2010; 30 (1): 280 DOI: 10.1080/02724630903413099
An international team of scientists led by the paleontologist Steffen Kiel at the University of Kiel, Germany, found the first fossil boreholes of the worm Osedax that consumes whale bones on the deep-sea floor. They conclude that “boneworms” are at least 30 Million years old.
This result was published in the current issue of the scientific journal Proceedings of the National Academy of Sciences.
Six years ago Osedax was first described based on specimens living on a whale carcass in 2891 m depth off California. Since then paleontologists have been searching for fossil evidence to pin down its geologic age. Now researchers at the Institute of Geosciences at the Christian-Albrechts-University at Kiel, Germany, found 30 Million year old whale bones with holes and excavations matching those of living Osedax in size and shape. The evidence of the boreholes and cavities made by the living worms was provided by Greg Rouse (Scripps Institution of Oceanography), one of the original discoverers of Osedax.
To produce accurate images of the fossil boreholes, the bones were CT-scanned by the scientists. The fossil bones belong to ancestors of our modern baleen whales and their age was determined using so-called co-occurring index fossils. “The age of our fossils coincides with the time when whales began to inhabit the open ocean” explains Steffen Kiel, who has been working on the evolution and fossil history of deep-sea ecosystems for many years. Only from the open ocean dead whales could sink to the deep-sea floor where they served as food for the boneworms. “Food is extremely rare on the vast deep-sea floor and the concurrent appearance of these whales and Osedax shows that even hard whale bones were quickly utilized as food source,” Steffen Kiel explains the relevance of their discovery.
The ancient bones were found by the American fossil collector Jim Goedert. He has been collecting fossil along the American Pacific coast for more than 30 years and is well known in the scientific community. Steffen Kiel says: “I got to know Jim when I was a PhD student, when he visited Hamburg University. We kept in touch ever since.” By now, Steffen Kiel has done several field trips with Jim Goedert to the US Pacific coast, a geologically active area where fossil-rich sediments are continuously uplifted by plate tectonic processes.
Vertebrate paleontologists are probably less happy about the old age of Osedax: because it has been feeding on bones for most of the evolutionary history of whales, it is likely to have destroyed many potential whale fossils.
Adapted from materials provided by Kiel University.