It's a Tyrannosaur-eat-Tyrannosaur world
- Date:
- October 29, 2015
- Source:
- Geological Society of America
- Summary:
- A nasty little 66-million-year-old family secret has been leaked by a recently unearthed tyrannosaur bone. The bone has peculiar teeth marks that strongly suggest it was gnawed by another tyrannosaur. The find could be some of the best evidence yet that tyrannosaurs were not shy about eating their own kind.
A nasty little 66-million-year-old family secret has been leaked by a recently unearthed tyrannosaur bone. The bone has peculiar teeth marks that strongly suggest it was gnawed by another tyrannosaur. The find could be some of the best evidence yet that tyrannosaurs were not shy about eating their own kind.
"We were out in Wyoming digging up dinosaurs in the Lance Formation," said paleontologist Matthew McLain of Loma Linda University in California. "Someone found a tyrannosaur bone that was broken at both ends. It was covered in grooves. They were very deep grooves."
The grooves were clearly those of an animal pulling the flesh off the bone -- pulling in a direction perpendicular to the bone, in the same way humans eat a piece of fried chicken. But one groove stood out. It was located at the larger end of the bone and contained smaller parallel grooves caused by the diner's head turning, so that the serrated edges of its teeth dragged across the bone.
Serrated teeth rule out crocodiles and point directly to a theropod dinosaur like T. rex. The fact that the only large theropods found in the Lance Formation are two tyrannosaurs --Tyrannosaurus rex or Nanotyrannus lancensis -- eliminates all interpretations but cannibalism, explained McLain, who will be presenting the discovery on 1 Nov. at the annual meeting of the Geological Society of America in Baltimore.
"This has to be a tyrannosaur," said McLain. "There's just nothing else that has such big teeth."
The direction of the grooves is consistent with getting flesh from bones off an animal that was quite dead at the time. The bones don't reveal whether the cannibal was scavenging or was also the killer of the tyrannosaur.
"Exactly who did the eating that day, in the Late Cretaceous, could still be sorted out by the same grooves," McLain said.
The serration grooves are a valuable clue to the size of the animal who owned the teeth. Previous work using Komodo dragon teeth has demonstrated the relationship between serration sizes and the size of the animal. This approach has been used on tyrannosaurs, and McLain thinks it will work in this case, too.
"It only works if you know what species it is," he said. "And since tyrannosauruses are the only large predators in these formations, it's pretty straightforward."
Even without knowing the size of the eater, it may be easy to say which species of tyrannosaur was eating, because, according to McLain, many paleontologists believe Nanotyrannus were really juvenile T. rex.
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300 million-year-old 'supershark' fossils found in Texas
- Date:
- October 29, 2015
- Source:
- Society of Vertebrate Paleontology
- Summary:
- Even before the age of dinosaurs, big toothy predators were roaming Texas. 300 million years ago, during a time called the Carboniferous, the area surrounding what is now Dallas, Texas was flooded by a shallow sea. Fossils from this ancient environment were recently recovered from Jacksboro, Texas. Among these were two fossil braincases from massive extinct relatives of modern-day sharks.
Previously, giant sharks had only been recovered from rock dating back 130 million years, during the age of the dinosaurs. The largest shark that ever lived, commonly called "Megalodon," is much younger, with an oldest occurrence at about 15 million years ago. This means the new fossils from Texas indicate giant sharks go much further back into the fossil record.
After the generous donation of these fossils and careful study with Dr. John Maisey of the American Museum of Natural History in New York, the team was able to estimate how big the entire sharks would have been by comparison with smaller and more complete fossils of closely related sharks. The results were very impressive.
The size range estimated for these two Texas 'supersharks' was between 18 and 26 feet in length (5.5 to 8 meters). The largest of these specimens was 25% bigger than today's largest predatory shark, the Great White. Although not nearly as large as Megalodon, which might have reached up to 67 feet in length (about 20 meters), the fossil sharks from Texas would have been by far the biggest sharks in the sea.
These fossil braincases may belong to an extinct species of shark called Glikmanius occidentalis, or they may represent a new and larger related species that is new to science. Closely related sharks are known from as far off as Scotland, showing this group of sharks was capable of dispersing across great distances.
Maisey, McKinzie, and Williams timed their research results very well, being able to present their Texas 'supershark' at the annual meeting for the Society of Vertebrate Paleontology in Dallas, Texas. According to Maisey, even 300 million years ago, "everything is bigger in Texas!"
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Transitional species of duckbilled dinosaurs illuminate relationship between evolution and growth
- Date:
- October 29, 2015
- Source:
- Society of Vertebrate Paleontology
- Summary:
- The discovery of two new transitional species is helping reveal the pattern of evolution in duckbilled dinosaurs, providing key insight into the intricate relationship between changes during growth and the evolution of elaborate display structures.
An emergent field of research in dinosaur paleobiology investigates the relative importance of linear, non-branching evolution (anagenesis) compared with branching evolution (cladogenesis). Increasingly, paleontologists are discovering that many dinosaur species are arranged into anagenetic lineages of rapidly evolving "transitional" species which do not overlap in time. These transitional species usually differ only slightly from their forebears, typically in the shape and size of display structures such as horns or crests.
At the SVP 2015 annual meeting, Dr Elizabeth Freedman Fowler of the Museum of the Rockies, and Great Plains Dinosaur Museum, Montana, presented on two new transitional species of duckbilled (hadrosaurid) dinosaurs from the Upper Cretaceous Judith River Formation of northern Montana.
"This particular part of the Judith River Formation is important because it yields a dinosaur fauna that is intermediate in age between an older fauna from the Two Medicine Formation of western Montana, and a younger fauna from the famous Oldman and Dinosaur Park Formations of Alberta." Dr Freedman Fowler continued, "because the formation is intermediate in age, then it is exactly where we might expect to find new, intermediate kinds of dinosaur."
The first new dinosaur described by Dr. Freedman Fowler is a transitional form of Brachylophosaurus, a large hadrosaurid with a broad paddle shaped crest over the back of its head. The second, a transitional Gryposaurus hadrosaurid, has an arched nasal crest on its snout, and is known from a bonebed of at least 10 individuals, ranging from juvenile to adult.
"The Gryposaurus bonebed is a fantastic site because the different growth stages show us that as Gryposaurus grew, the arch on its nose gets larger and moves backward, so that the nose of a one year old looks very different from the nose of a three year old," Dr. Freedman Fowler explained, "the most interesting thing is that we see the same morphological trend through time as Gryposaurus evolves. The preceding species from the Two Medicine Formation has a low crest over the middle of the nose, whereas in the succeeding species the crest is taller and more retracted towards the eyes"
This suggests that successive generations of Gryposaurus grew larger crests by changing the timing or pace of crest development during growth. Fragmentary juveniles of the transitional Brachylophosaurus species suggest that this same process is also occurring in that lineage. Changing of timing or rate of development is called heterochrony, a process which is being increasingly recognized as a major driving force in evolution.
"Heterochrony is key to understanding how evolution actually occurs in these dinosaurs, but to study heterochrony we need large collections of dinosaurs with multiple growth stages, and a really precise time framework for the rock formations that we collect them from" said Dr. Freedman Fowler.
This kind of research has only really become possible with recent technical advances in the radiometric dating of rocks, coupled with increased intensity of fossil collecting in North America.
"The Late Cretaceous of western North America is the only place in the world where we can do these kinds of intense paleobiological studies on dinosaurs. Nowhere else combines the precise dating of rocks coupled with an exceptional fossil record that has been so extensively collected."
Dr. Freedman Fowler predicts that many more transitional species remain to be discovered; "We've been collecting dinosaurs in this region for over a century, yet there are still exciting discoveries being made every year."
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Mammal body-size responds to climate change in ancient Wyoming
- Date:
- October 29, 2015
- Source:
- Society of Vertebrate Paleontology
- Summary:
- Evidence from fossils suggests that multiple global warming events, which occurred over 50 million years ago, impacted the evolution of mammals living in ancient Wyoming. Using over seven thousand fossilized teeth, paleontologists found a reduction in body size of mammal populations, hypothesized to be related to warming events. This work provides a unique glimpse at the long-term impact of climatic change on mammal populations.
To unravel the link between past climates and animal faunas requires an exceptional fossil record. Chew, an associate professor at Western University of Health Sciences, California, used fossils from the Bighorn Basin of Wyoming, a nearly complete record of around 5 million years of mammalian evolution, to study responses of mammal communities through time. "The Bighorn Basin fossil record, particularly from this part of the basin, is one of the best early Cenozoic terrestrial records in the world." remarks Chew. "My colleagues have been assembling the fossil samples on which this work is based for more than 30 years. Their efforts have produced a superb, highly resolved, thoroughly studied record that is unparalleled. This record allows us to examine more sophisticated questions about faunal response to climate and environmental change than was previously possible."
Information on past climate in the Bighorn basin comes from the structure of carbon atoms, known as isotopes, preserved in the rock. This technique revealed three global warming events. The first occurred 55 million years ago, and has been previously linked to decreasing body-size. However, data from the next two events, occurring two million years later, is required to test if this forms part of a larger evolutionary pattern. "No other terrestrial record exists with the density of fossils necessary to test faunal response to the later hyperthermals [climatic warming]. The central Bighorn Basin record essentially documents a set of repeated, natural experiments in climate warming." Chew explains.
Chew examined the size of over 7500 fossil teeth from over one hundred types of mammals, and compared them before, during and after the climatic warming events. On average, the Bighorn Basin teeth were 10-20% smaller during the warm periods. Some lineages of mammals became smaller themselves, in a process known as dwarfing. However, mostly size change was driven by an increase in the abundance of small species relative to large ones in the basin during warm periods.
These findings add to the increasing evidence for the strong link between climatic change and animal populations. "The ability to compare faunal response between events is critical for establishing mechanisms of change and predicting the consequences of future warming."
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Society of Vertebrate Paleontology. "Mammal body-size responds to climate change in ancient Wyoming." ScienceDaily. ScienceDaily, 29 October 2015. <www.sciencedaily.com/releases/2015/10/151029112230.htm
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Adolescent T. rex unraveling controversy about growth changes in Tyrannosaurus
- Date:
- October 29, 2015
- Source:
- Society of Vertebrate Paleontology
- Summary:
- A much-anticipated study of an adolescent Tyrannosaurus rex is poised to help resolve long-standing controversies over the growth of tyrannosaurid dinosaurs.
- Share:
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In 2001, a paleontology field crew from Burpee Museum of Natural History (Rockford, IL) were prospecting for dinosaur fossils near Ekalaka, Montana, when they discovered bones of a half-grown T. rex weathering out from exposures of the Hell Creek Formation. "Jane," as she was later named, turned out to be the most complete adolescent T. rex ever discovered, filling a critical gap between juvenile and adult that had caused decades of scientific debate.
Prior to Jane's discovery, a small lightly built tyrannosaur skull collected near Ekalaka in 1942 had been at the center of a controversy over how much T. rex changed during growth. The skull had spent an uneventful half century on display at Cleveland Museum of Natural History, Ohio, when in 1988, famed paleontologist Dr. Robert Bakker redescribed the fossil as a new species, Nanotyrannus lancensis, proposing that it represented a smaller, more sleek cousin of T. rex.
This interpretation has been controversial since 1999 when Dr. Thomas Carr showed that the differences between "Nanotyrannus" and those of adult T. rex are also seen during growth in other species of tyrannosaurids. This suggested that the Cleveland skull was from a juvenile T. rex rather than being a separate species in its own right. However, this hypothesis met with surprising resistance. Could a dinosaur really change that much during growth?
"The extreme changes from the sleek skull of juveniles to the robust skull of adults were too much for some people to believe; for example, they didn't like to hear that T. rex lost tooth positions as it grew from a juvenile with many teeth, to an adult with fewer teeth. Regardless, the search was on for a transitional specimen that could test the hypothesis."
Enter Jane. Her fine skull and skeleton was intermediate in size and shape between the Cleveland skull and fully adult T. rex. Carr's research team presented a detailed study of Jane at the Society of Vertebrate Paleontology 2015 annual meeting in Dallas.
"Jane shows us that the gap is in fact bridgeable because many features seen in her are more similar to adult T. rex than to the Cleveland skull. The features are exactly what we'd predict are necessary to make the change to a full adult." said Carr.
Another important dimension of the "Jane" story is that she was discovered on public lands, then collected and mounted for display by a public museum. "Dinosaur fossils such as this emphasize the importance of accredited institutions collecting on public lands, which makes the specimens on them available for scientific study," asserts Dr Carr.
In a world where commercially collected dinosaurs demand ever upwardly spiralling prices, Jane is a world-class dinosaur that didn't come with a million dollar price tag. Burpee Museum director of science and exhibits, Scott Williams, summed up:
"Jane is simply the best preserved and most complete example of a publicly accessible, subadult Tyrannosaurus rex in the world. For the last 10 years she has been available to qualified researchers as well as exhibited to the general public. The quality of the specimen and its availability will undoubtedly provide researchers decades of important data regarding the ontogeny of the most recognized dinosaur species in the world."
Regardless of Jane's completeness and growth stage, she doesn't close the book on T. rex growth and evolution; there is still a gap for yet undiscovered fossils to fill between her sleek form and the deep, imposing skulls of adults.
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Dinosaurs used nasal passages to keep brains cool
- Date:
- October 29, 2015
- Source:
- Society of Vertebrate Paleontology
- Summary:
- Dinosaur nasal passages were certainly nothing to sneeze at. Possessing among the largest and most complex nasal passages seen in animals, their function has puzzled paleontologists. New research suggests that the size and shape of these nasal passages would have allowed incoming air to cool the blood making its way to the brain, maintaining the brain at an optimum temperature.
"My work represents the first test of the hypothesis that the elaborated nasal passages of large dinosaurs functioned as efficient heat exchangers," explained Jason Bourke, doctoral student researcher at Ohio University and lead author of the study. Using a branch of engineering known as computational fluid dynamics, Bourke simulated the movement of air and heat through the nasal passages of various dinosaur species.
Nasal passages act as air conditioners, warming and humidifying air as it is breathed in, and cooling and drying it as air leaves the body. This process cools blood destined for the brain. Modern mammals, birds, lizards, and crocodiles use a variety of structures -- some simple, and some complex -- to accomplish heat exchange efficiently. However, detailed reconstruction of the 3-dimensional shape of the nasal passages in dinosaurs have shown that large dinosaurs, whose bodies would have held on to more heat than smaller-bodied animals, needed elaborate and specialized nasal passages to avoid overheating their brains.
"For most dinosaurs that I looked at, there would have been a substantial amount of physiologically active soft tissues in their noses," continued Bourke. "This strongly suggests that dinosaur airways were more than capable of changing the attributes of respired air." These findings provide an answer to the mystery of how dinosaurs avoided having their large bodies overheat their small brains, a question that has plagued paleontologists reconstructing dinosaur physiology.
" By having this blood detour through the nasal passages and dump some of that excess heat before reaching the brain, dinosaurs were able to keep their brains at an optimum temperature for their bodies," said Bourke.
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Meet the first Iberian lynx on the Iberian Peninsula
- Date:
- October 28, 2015
- Source:
- FECYT - Spanish Foundation for Science and Technology
- Summary:
- The remains of an Iberian lynx specimen which lived 1.6 million years ago -- the oldest ever discovered -- were found resting in a cave in Barcelona. This discovery not only allows us to shed light on the origins of one of the world's most endangered feline species, but it also means that the emergence of this species on the Iberian Peninsula dates back half a million years earlier than what was originally believed.
The remains of an Iberian lynx specimen which lived 1.6 million years ago -- the oldest ever discovered -- were found resting in a cave in Barcelona (Spain). This discovery not only allows us to shed light on the origins of one of the world's most endangered feline species, but it also means that the emergence of this species on the Iberian Peninsula dates back half a million years earlier than what was originally believed.
This newly discovered specimen was 10 to 20 centimetres larger and around 10 kilograms heavier than the Iberian lynx that currently inhabits Doñana National Park in Spain. Its coat was also longer than it is today in order to withstand continuous near-freezing temperatures. This description of the feline was formulated after a study was carried out on one of the first Iberian lynxes that ever lived in Spain.
Part of a cranial fossil belonging to an Iberian lynx (Lynx pardinus) was uncovered among the horse, goat, deer, woolly mammoth, fox and wolf bones preserved in the Avenc Marcel Cave located in the Garraf massif of Barcelona. This is the oldest Iberian lynx that has been found on the Iberian Peninsula to date and it was discovered by the scientist Manel Llenas in 2003.
The fossil remains of this feline are proof of its presence on the Iberian Peninsula as early as 1.6 to 1.7 million years ago. Up until now scientists had dated the appearance of the Iberian lynx to between 1 and 1.1 million years ago. Thus, this discovery means that the emergence of this feline on the Iberian Peninsula actually dates back 500,000 years earlier than what scientists originally thought.
"We have confirmed this earlier appearance of the Iberian lynx based on initial molecular studies that estimate the emergence of this feline during the Early Pleistocene in the Iberian Peninsula," asserts Alberto Boscaini, a researcher at the Miquel Crusafont Catalan Institute of Palaeontology (ICP) and the main author of this study published by Quaternary Science Reviews.
Timeline of the evolution of this species
In order to understand the origins of the Iberian Peninsula's most emblematic species and one of the world's most endangered felines according to the International Union for Conservation of Nature (UICN), we must first go back in time.
The common ancestor of all the species belonging to the Lynx genus, Lynx issiodorensis, first appeared in North America about four million years ago before spreading to the continents of Asia and Europe where it persisted throughout time. These species underwent few changes, with the most evident being a decrease in size.
The first species of lynx to evolve was Lynx rufus about 2.5 million years ago when it scattered across North America. In Asia Lynx lynx emerged, the species that would later spread across Europe. This feline also spread across North America about 200,000 years ago, thus giving rise to Lynx canadensis which displaced Lynx rufus towards the south.
The European population of L. issiodorensis led to the appearance of Lynx pardinus one and half million years ago. Since then, this species has endured few changes to its genetics and continues to inhabit the Iberian Peninsula today. According to scientists, this evolution may have taken place when the Iberian Peninsula became isolated due to one or several consecutive glacial periods.
The new date provided by the study -1.6 million years ago- lines up with the period of time when all of southern Europe, especially the Iberian Peninsula, became a refuge from the Quaternary glaciation.
Glacial periods alternated with interglacial periods that "greatly influenced wildlife, especially mammals, in that habitat," the expert adds.
This refuge was also home to the European rabbit (Oryctolagus cunilus), the Iberian lynx's primary prey more than 75% of the time. The morphological analyses carried out on the cranium found in Catalonia confirm the type of diet consumed by this feline.
"Other cranial features -- such as those related to this carnivore's diet -- are proof that the Iberian lynx hunted small-sized prey such as lagomorphs and rodents which had a great presence during that time period," the researcher states.
According to the study, speciation of the Iberian lynx could therefore be related to the special diet still followed by these specimens inhabiting our planet today, including the rabbit as their primary prey.
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Journal Reference:
- Alberto Boscaini, Joan Madurell-Malapeira, Manel Llenas, Bienvenido Martínez-Navarro. The origin of the critically endangered Iberian lynx: Speciation, diet and adaptive changes. Quaternary Science Reviews, 2015; 123: 247 DOI: 10.1016/j.quascirev.2015.07.001
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