New species of Allosaurus discovered in Utah
A remarkable new species of meat-eating dinosaur has been unveiled at the Natural History Museum of Utah. Paleontologists unearthed the first specimen in early 1990s in Dinosaur National Monument in northeastern Utah. The huge carnivore inhabited the flood plains of western North America during the Late Jurassic Period, between 157-152 million years ago, making it the geologically oldest species of Allosaurus, predating the more well-known state fossil of Utah, Allosaurus fragilis. The newly named dinosaur Allosaurus jimmadseni, was announced today in the open-access scientific journal PeerJ.
The species belongs to the allosauroids, a group of small to large-bodied, two-legged carnivorous dinosaurs that lived during the Jurassic and Cretaceous periods. Allosaurus jimmadseni, possesses several unique features, among them a short narrow skull with low facial crests extending from the horns in front of the eyes forward to the nose and a relatively narrow back of the skull with a flat surface to the bottom of the skull under the eyes. The skull was weaker with less of an overlapping field of vision than its younger cousin Allosaurus fragilis. Allosaurus jimmadseni evolved at least 5 million years earlier than fragilis, and was the most common and the top predator in its ecosystem. It had relatively long legs and tail, and long arms with three sharp claws. The name Allosaurus translates as “different reptile,” and the second part, jimmadseni, honors Utah State Paleontologist James H. Madsen Jr.
Following an initial description by Othniel C. Marsh in 1877, Allosaurus quickly became the best known — indeed the quintessential — Jurassic theropod. The taxonomic composition of the genus has long been a debate over the past 130 years. Paleontologists argue that there are anywhere between one and 12 species of Allosaurus in the Morrison Formation of North America. This study recognizes only two species — A. fragilis and A. jimmadseni.
“Previously, paleontologists thought there was only one species of Allosaurus in Jurassic North America, but this study shows there were two species — the newly described Allosaurus jimmadseni evolved at least 5 million years earlier than its younger cousin, Allosaurus fragilis,” said co-lead author Mark Loewen, research associate at the Natural History Museum of Utah, and associate professor in the Department of Geology and Geophysics at the University of Utah led the study. “The skull of Allosaurus jimmadseni is more lightly built than its later relative Allosaurus fragilis, suggesting a different feeding behavior between the two.”
George Engelmann of the University of Nebraska, Omaha initially discovered the initial skeleton of the new species within Dinosaur National Monument in 1990. In 1996, several years after the headless skeleton was collected, the radioactive skull belonging to the skeleton using a radiation detector by Ramal Jones of the University of Utah. Both skeleton and skull were excavated by teams from Dinosaur National Monument.
“Big Al,” another specimen belonging to the new species, was discovered in Wyoming on United States Bureau of Land Management (BLM) land in 1991 and is housed in the collections of the Museum of The Rockies in Bozeman, Montana. Previously thought to belong to Allosaurus fragilis, “Big Al” was featured in the BBC’s 2001 “Walking with Dinosaurs: Ballad of Big Al” video. Over the last 30 years, crews from various museums have collected and prepared materials of this new species. Other specimens include “Big Al Two” at the Saurier Museum Aathal in Switzerland and Allosaurus material from the Dry Mesa Quarry of Colorado at Brigham Young University.
Early Morrison Formation dinosaurs were replaced by some of the most iconic dinosaurs of the Late Jurassic
Allosaurus jimmadseni lived on the semi-arid Morrison Formation floodplains of the interior of western North America. The older rocks of the Morrison Formation preserve a fauna of dinosaurs distinct from the iconic younger Morrison Formation faunas that include Allosaurus fragilis, Diplodocus and Stegosaurus. Paleontologists have recently determined that specimens of this new species of dinosaur lived in several places throughout the western interior of North America (Utah, Colorado and Wyoming).
Study summary
Dinosaurs were the dominant members of terrestrial ecosystems during the Mesozoic. However, the pattern of evolution and turnover of ecosystems during the middle Mesozoic remains poorly understood. The authors report the discovery of the earliest member of the group of large-bodied allosauroids in the Morrison Formation ecosystem that was replaced by Allosaurus fragilis and illustrate changes acquired in the genus over time. The study includes an in-depth description of every bone of the skull and comparisons with the cranial materials of other carnivorous dinosaurs. Finally, the study recognizes just two species of Allosaurus in North America with Allosaurus fragilis replacing its earlier relative Allosaurus jimmadseni.
Fact sheet: Major points of the paper
- A remarkable new species of meat-eating dinosaur, Allosaurus jimmadseni, is described based on two spectacularly complete skeletons. The first specimen was unearthed in Dinosaur National Monument, in northeastern Utah.
- Allosaurus jimmadseni is distinguished by a number of unique features, including low crests running from above the eyes to the snout and a relatively narrow back of the skull with a flat surface to the bottom of the upper skull under the eyes. The skull was weaker with less of an overlapping field of vision than its younger cousin Allosaurus fragilis.
- At 155 million years old, Allosaurus jimmadseni is the geologically-oldest species of Allosaurus predating the more well-known State Fossil of Utah Allosaurus fragilis.
- Allosaurus jimmadseni was the most common and the top predator in its ecosystem. It had relatively long legs and tail, and long arms with three sharp claws.
Study design
- Comparison of the bones with all other known allosauroid dinosaurs indicate that the species possessed unique features of the upper jaw and cheeks (maxilla and jugal) and a decorative crest stretching from just in front of the eyes to the nose.
- Many of the comparisons were made with the thousands of bones of Allosaurus fragilis collected from the famous Cleveland-Lloyd Dinosaur Quarry administered by the Bureau of Land Management that are housed in the collections of the Natural History Museum of Utah.
- On the basis of these features, the scientific team named it a new genus and species of dinosaur, Allosaurus jimmadseni (translating to “Jim Madsen’s different reptile”).
- Allosaurus jimmadseni is particularly notable for its slender, narrow skull with short sharp nasal crests compared to its close relative and successor Allosaurus fragilis.
- The study was funded in part by the University of Utah, the National Park Service and the National Science Foundation.
New dinosaur name: Allosaurus jimmadseni
- The first part of the name, Allosaurus, (a·luh·SAW·ruhs) can be translated from Greek as the “other,” “strange” or “different” and “lizard” or “reptile” literally to “different reptile.” The second part of the name jimmadseni (gym-MAD-sehn-eye) honors the late Utah State Paleontologist James Madsen Jr. who excavated and studied tens of thousands of Allosaurus bones from the famous Cleveland-Lloyd Dinosaur Quarry in central Utah and contributed greatly to the knowledge of Allosaurus.
Size
- Allosaurus jimmadseni was approximately 26 to 29 feet (8-9 meters) long.
- Allosaurus jimmadseni weighed around 4000 lbs. (1.8 metric tonnes).
Relationships
- Allosaurus jimmadseni belongs to a group of carnivorous dinosaurs called “allosauroids,” the same group as the famous Allosaurus fragilis.
- Other dinosaurs found in rocks containing Allosaurus jimmadseni include the carnivorous theropods Torvosaurus and Ceratosaurus; the long-necked sauropods Haplocanthosaurus and Supersaurus; and the plate-backed stegosaur Hesperosaurus.
- Allosaurus jimmadseni is closely related to the State Fossil of Utah, Allosaurus fragilis.
Anatomy
- Allosaurus jimmadseni was a two-legged carnivore, with long forelimbs and sharp, recurved claws that were likely used for grasping prey.
- Like other allosauroid dinosaurs, Allosaurus jimmadseni had a large head full of 80 sharp teeth. It was also the most common carnivore in its ecosystem.
Age and geography
- Allosaurus jimmadseni lived during the Kimmeridgian stage of the Late Jurassic period, which spanned from approximately 157 million to 152 million years ago.
- Allosaurus jimmadseni lived in a semi-arid inland basin filled with floodplains, braided stream systems, lakes, and seasonal mudflats along the western interior of North America.
- Allosaurus jimmadseni represents the earliest species of Allosaurus in the world.
Discovery
- Allosaurus jimmadseni can be found in a geologic unit known as the Salt Wash Member of the Morrison Formation and its equivalents exposed in Colorado, Wyoming, and Utah.
- The first specimen of Allosaurus jimmadseni was discovered in the National Park Service administered by Dinosaur National Monument in Uintah County, near Vernal, Utah.
- Allosaurus jimmadseni was first discovered by George Engelmann of the University of Nebraska, Omaha on July 15, 1990 during a contracted paleontological inventory of the Morrison Formation of Dinosaur National Monument.
- Another specimen of Allosaurus jimmadseni known as “Big Al,” was found on land administered by the U.S. Department of the Interior’s Bureau of Land Management in Wyoming.
- Further specimens of Allosaurus jimmadseni have been subsequently recognized in the collections of various museums.
- Allosaurus jimmadseni specimens are permanently housed in the collections of Dinosaur National Monument, Utah; the Museum of the Rockies, Bozeman, Montana; the Saurier Museum of Aathal, Switzerland; the South Dakota School of Mines, Rapid City, South Dakota; Brigham Young University’s Museum of Paleontology, Provo, Utah; and the United States National Museum (Smithsonian) Washington D.C.
- These discoveries are the result of a continuing collaboration between the Natural History Museum of Utah, the National Park Service, and the Bureau of Land Management.
Excavation
- The first skeleton of Allosaurus jimmadseni was excavated during the summers of 1990 to 1994 by staff of the National Park Service’s Dinosaur National Monument. The skeleton block was so heavy it required the use of explosives to remove surrounding rock and a helicopter to fly out the 2700 kg block. The head of the skeleton was missing
- The first bones of Allosaurus jimmadseni discovered included toes and some tail vertebrae. Later excavation revealed most of an articulated skeleton missing the head and part of the tail.
- The radioactive skull of the first specimen of Allosaurus jimmadseni, which had previously eluded discovery, was found in 1996 by Ramal Jones of the University of Utah using a radiation detector.
Preparation
- It required seven years to fully prepare all of the bones of Allosaurus jimmadseni.
- Much of the preparation was done by then Dinosaur National Monument employees Scott Madsen and Ann Elder, with some assistance from Dinosaur National Monument volunteers and students at Brigham Young University.
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Journal Reference:
- Daniel J. Chure, Mark A. Loewen. Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America. PeerJ, 2020; 8: e7803 DOI: 10.7717/peerj.7803
New feathered dinosaur shows dinosaurs grew up differently from birds
A new species of feathered dinosaur has been discovered in China, and described by American and Chinese authors and published today in the journal, The Anatomical Record.
The one-of-a-kind specimen offers a window into what the earth was like 120 million years ago. The fossil preserves feathers and bones that provide new information about how dinosaurs grew and how they differed from birds.
“The new dinosaur fits in with an incredible radiation of feathered, winged animals that are closely related to the origin of birds,” said Dr. Ashley Poust, who analyzed the specimens while he was a student at Montana State University and during his time as a Ph.D. student at University of California, Berkeley. Poust is now postdoctoral researcher at the San Diego Natural History Museum.
“Studying specimens like this not only shows us the sometimes-surprising paths that ancient life has taken, but also allows us to test ideas about how important bird characteristics, including flight, arose in the distant past.”
Scientists named the dinosaur Wulong bohaiensis. Wulong is Chinese for “the dancing dragon” and references the position of the beautifully articulated specimen.
About the Discovery
The specimen was found more than a decade ago by a farmer in China, in the fossil-rich Jehol Province, and since then has been housed in the collection of The Dalian Natural History Museum in Liaoning, a northeastern Chinese province bordering North Korea and the Yellow Sea. The skeletal bones were analyzed by Poust alongside his advisor Dr. David Varricchio from Montana State University while Poust was a student there.
Larger than a common crow and smaller than a raven, but with a long, bony tail which would have doubled its length, Wulong bohaiensis had a narrow face filled with sharp teeth. Its bones were thin and small, and the animal was covered with feathers, including a wing-like array on both its arms and legs and two long plumes at the end of its tail.
This animal is one of the earliest relatives of Velociraptor, the famous dromaeosaurid theropod dinosaur that lived approximately 75 million years ago. Wulong’s closest well-known relative would have been Microraptor, a genus of small, four-winged paravian dinosaurs.
The discovery is significant not only because it describes a dinosaur that is new to science, but also because it shows connection between birds and dinosaurs.
“The specimen has feathers on its limbs and tail that we associate with adult birds, but it had other features that made us think it was a juvenile,” said Poust. To understand this contradiction, the scientists cut up several bones of the new dinosaur to examine under a microscope. This technique, called bone histology, is becoming a regular part of the paleontology toolbox, but it’s still sometimes difficult to convince museums to let a researcher remove part of a nice skeleton. “Thankfully, our coauthors at the Dalian Natural History Museum were really forward thinking and allowed us to apply these techniques, not only to Wulong, but also to another dinosaur, a close relative that looked more adult called Sinornithosaurus.”
The bones showed that the new dinosaur was a juvenile. This means that at least some dinosaurs were getting very mature looking feathers well before they were done growing. Birds grow up very fast and often don’t get their adult plumage until well after they are full sized. Showy feathers, especially those used for mating, are particularly delayed. And yet here was an immature dinosaur with two long feathers extending beyond the tip of the tail.
“Either the young dinosaurs needed these tail feathers for some function we don’t know about, or they were growing their feathers really differently from most living birds,” explained Poust.
An additional surprise came from the second dinosaur the scientists sampled; Sinornithosaurus wasn’t done growing either. The bone tissue was that of an actively growing animal and it lacked an External Fundamental System: a structure on the outside of the bone that vertebrates form when they’re full size. “Here was an animal that was large and had adult looking bones: we thought it was going to be mature, but histology proved that idea wrong. It was older than Wulong, but seems to have been still growing. Researchers need to be really careful about determining whether a specimen is adult or not. Until we learn a lot more, histology is really the most dependable way.”
In spite of these cautions, Poust says there is a lot more to learn about dinosaurs.
“We’re talking about animals that lived twice as long ago as T. rex, so it’s pretty amazing how well preserved they are. It’s really very exciting to see inside these animals for the first time.”
About the Jehol Biota
The area in which the specimen was found is one of the richest fossil deposits in the world. The Jehol biota is known for the incredible variety of animals that were alive at the time. It is also one of the earliest bird-rich environments, where birds, bird-like dinosaurs, and pterosaurs all shared the same habitat.
“There was a lot of flying, gliding, and flapping around these ancient lakes,” says Poust. “As we continue to discover more about the diversity of these small animals it becomes interesting how they all might have fit into the ecosystem.” Other important changes were happening at the same time in the Early Cretaceous, including the spread of flowering plants. “It was an alien world, but with some of the earliest feathers and earliest flowers, it would have been a pretty one.”
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100 million years in amber: Researchers discover oldest fossilized slime mold
Most people associate the idea of creatures trapped in amber with insects or spiders, which are preserved lifelike in fossil tree resin. An international research team of palaeontologists and biologists from the Universities of Göttingen and Helsinki, and the American Museum of Natural History in New York has now discovered the oldest slime mould identified to date. The fossil is about 100 million years old and is exquisitely preserved in amber from Myanmar. The results have been published in the journal Scientific Reports.
Slime moulds, also called myxomycetes, belong to a group known as ‘Amoebozoa’. These are microscopic organisms that live most of the time as single mobile cells hidden in the soil or in rotting wood, where they eat bacteria. However, they can join together to form complex, beautiful and delicate fruiting bodies, which serve to make and spread spores.
Since fossil slime moulds are extremely rare, studying their evolutionary history has been very difficult. So far, there have only been two confirmed reports of fossils of fruiting bodies and these are just 35 to 40 million years old. The discovery of fossil myxomycetes is very unlikely because their fruiting bodies are extremely short-lived. The researchers are therefore astounded by the chain of events that must have led to the preservation of this newly identified fossil. “The fragile fruiting bodies were most likely torn from the tree bark by a lizard, which was also caught in the sticky tree resin, and finally embedded in it together with the reptile,” says Professor Jouko Rikkinen from the University of Helsinki. The lizard detached the fruiting bodies at a relatively early stage when the spores had not yet been released, which now reveals valuable information about the evolutionary history of these fascinating organisms.
The researchers were surprised by the discovery that the slime mould can easily be assigned to a genus still living today. “The fossil provides unique insights into the longevity of the ecological adaptations of myxomycetes,” explains palaeontologist Professor Alexander Schmidt from the University of Göttingen, lead author of the study.
“We interpret this as evidence of strong environmental selection. It seems that slime moulds that spread very small spores using the wind had an advantage,” says Rikkinen. The ability of slime moulds to develop long-lasting resting stages in their life cycle, which can last for years, probably also contributes to the remarkable similarity of the fossil to its closest present-day relatives.make a difference: sponsored opportunity
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