Fossils illuminate dinosaur evolution in eastern North America
Tyrannosaurus rex, the fearsome predator that once roamed what is now western North America, appears to have had an East Coast cousin.
A new study by Yale undergraduate Chase Doran Brownstein describes two dinosaurs that inhabited Appalachia — a once isolated land mass that today composes much of the eastern United States — about 85 million years ago: an herbivorous duck-billed hadrosaur and a carnivorous tyrannosaur. The findings were published Aug. 25 in the journal Royal Society Open Science.
The two dinosaurs, which Brownstein described from specimens housed at Yale’s Peabody Museum of Natural History, help fill a major gap in the North American fossil record from the Late Cretaceous and provide evidence that dinosaurs in the eastern portion of the continent evolved distinctly from their counterparts in western North America and Asia, Brownstein said.
“These specimens illuminate certain mysteries in the fossil record of eastern North America and help us better understand how geographic isolation — large water bodies separated Appalachia from other landmasses — affected the evolution of dinosaurs,” said Brownstein, who is entering his junior year at Yale College. “They’re also a good reminder that while the western United States has long been the source of exciting fossil discoveries, the eastern part of the country contains its share of treasures.”
For most of the second half of the Cretaceous, which ended 66 million years ago, North America was divided into two land masses, Laramidia in the West and Appalachia in the East, with the Western Interior Seaway separating them. While famous dinosaur species like T. rex and Triceratops lived throughout Laramidia, much less is known about the animals that inhabited Appalachia. One reason is that Laramidia’s geographic conditions were more conducive to the formation of sediment-rich fossil beds than Appalachia’s, Brownstein explained.
The specimens described in the new study were discovered largely during the 1970s at the Merchantville Formation in present day New Jersey and Delaware. They constitute one of the only known dinosaur assemblages from the late Santonian to early Campanian stages of the Late Cretaceous in North America. This fossil record period, dating from about 85 to 72 million years ago, is limited, Brownstein noted.
Brownstein examined a partial skeleton of a large predatory therapod, concluding that it is probably a tyrannosaur. He noted that the fossil shares several features in its hind limbs with Dryptosaurus, a tyrannosaur that lived about 67 million years ago in what is now New Jersey. The dinosaur has different hands and feet than T. rex, including massive claws on its forelimbs, suggesting that it represents a distinct family of the predators that evolved solely in Appalachia.
“Many people believe that all tyrannosaurs must have evolved a specific set of features to become apex predators,” Brownstein said. “Our fossil suggests they evolved into giant predators in a variety of ways as it lacks key foot or hand features that one would associate with western North American or Asian tyrannosaurs.”
The partial skeleton of the hadrosaur provided important new information on the evolution of the shoulder girdle in that group of dinosaurs, Brownstein found. The hadrosaur fossils also provide one of the best records of this group from east of the Mississippi and include some of the only infant/perinate (very young) dinosaur fossils found in this region.
Brownstein, who works as a research associate at the Stamford Museum and Nature Center in Stamford, Connecticut, has previously published his paleontological research in several peer-journals, including Scientific Reports, the Journal of Paleontology, and the Zoological Journal of the Linnaean Society. In addition to eastern North American fossils, he currently focuses his research on the evolution of fishes, lizards, and birds. He is particularly interested in how geographic change and other factors contribute to how fast different types of living things evolve.
He currently works in the lab of Thomas J. Near, curator of the Peabody Museum’s ichthyology collections and professor and chair of the Department of Ecology and Evolutionary Biology at Yale. Brownstein also collaborates with Yale paleontologists Jacques Gauthier and Bhart-Anjan Bhullar in the Department of Earth and Planetary Sciences.
While Brownstein is considering pursuing an academic career in evolutionary biology, he says his research is driven by enjoyment.
“Doing research and thinking about these things makes me happy,” he said. “Like biking, it’s something I love to do.”
Story Source:
Materials provided by Yale University. Original written by Mike Cummings. Note: Content may be edited for style and length.
Journal Reference:
- Chase Doran Brownstein. Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America. Royal Society Open Science, 2021; 8 (8): 210127 DOI: 10.1098/rsos.210127
New fossils show what the ancestral brains of arthropods looked like
Exquisitely preserved fossils left behind by creatures living more than half a billion years ago reveal in great detail identical structures that researchers have long hypothesized must have contributed to the archetypal brain that has been inherited by all arthropods. Arthropods are the most diverse and species-rich taxonomic group of animals and include insects, crustaceans, spiders and scorpions, as well as other, less familiar lineages such as millipedes and centipedes.
The fossils, belonging to an arthropod known as Leanchoilia, confirm the presence — predicted by earlier studies in genetics and developmental biology of insect and spider embryos — of an extreme frontal domain of the brain that is not segmented and is invisible in modern adult arthropods. Despite being invisible, this frontal domain gives rise to several crucial neural centers in the adult arthropod brain, including stem cells that eventually provide centers involved in decision-making and memory. This frontal domain was hypothesized to be distinct from the forebrain, midbrain and hindbrain seen in living arthropods, and it was given the name prosocerebrum, with “proso” meaning “front.”
Described in a paper published today in the journal Current Biology, the fossils provide the first evidence of the existence of this discrete prosocerebral brain region, which has a legacy that shows up during the embryonic development of modern arthropods, according to paper lead author Nicholas Strausfeld, a Regents Professor of Neuroscience at the University of Arizona.
“The extraordinary fossils we describe are unlike anything that has been seen before,” Strausfeld said. “Two nervous systems, already unique because they are identically preserved, show that half a billion years ago this most anterior brain region was present and structurally distinct before the evolutionary appearance of the three segmental ganglia that denote the fore-, mid- and hindbrain.”
The term ganglion refers to a system of networks forming a nerve center that occurs in each segment of the nervous system of an arthropod. In living arthropods, the three ganglia that mark the three-part brain condensed together to form a solid mass, obscuring their evolutionary origin as segmented structures.
Fossils of Brain Tissue are Extremely Rare
Discovered in deposits of the Kaili formation — a geological formation in the Guizhou province of southwest China — the fossilized remains of Leanchoilia date back to the Cambrian period, about 508 million years ago. The Kaili fossils occur in sedimentary rock that has high concentrations of iron, the presence of which probably helped preserve soft tissue, which subsequently was replaced by carbon deposits.
“The Kaili fossils open a window for us to glimpse the body plan evolution of animals that lived more than half a billion years ago,” said the paper’s first author, Tian Lan of the Guizhou Research Center for Palaeobiology at Guizhou University in China. “For the first time, we now know that arthropod fossils of the Kaili formation have the potential to preserve neural tissue that show us the primitive brain of the early stem arthropod existing at the dawn of the animal world.”
“Nervous systems, as other soft tissues, are difficult to fossilize,” added co-author Pedro Martinez of the Universitat de Barcelona and Institut Catalá in Barcelona, Spain. “This makes the study of the early evolution of neural systems a challenging task.”
The fossils also shed new light on the evolutionary origin of two separate visual systems in arthropod evolution: pairs of front-facing eyes or sideward looking eyes, the descendants of which are still present in species living today.
Many arthropods, including insects and crustaceans, have a distinct bilateral pair of faceted compound eyes and another set of less obvious eyes — with more primitive architecture — known as nauplius eyes, or ocelli. These are structurally similar to the principal eyes of spiders and scorpions. These simpler eyes correspond to the prosocerebrum’s forward eyes in Leanchoilia, in line with evidence obtained by previous studies analyzing gene expression patterns during embryonic development of living arthropods.
Leanchoilia‘s sideward eyes, on the other hand, relate to the protocerebrum, which is the segmental ganglion defining the arthropod forebrain, lying just behind the prosocerebrum. In living arthropods, the protocerebrum provides the compound eyes of insects and crustaceans, or the lateral single-lens eyes of arachnids, centipedes and millipedes. The visual centers serving those eyes also belong to the brain’s protocerebral region.
Strausfeld explained that in living arthropods, the protocerebrum, or forebrain, has incorporated — in a way, swallowed up — the ancient centers provided by the prosocerebrum, so that it is no longer discernible as a distinct anatomical entity.
The fossils are so well-preserved that they demonstrate that in addition to frontward eyes, the prosocerebrum has also given rise to ganglia associated with the labrum, or “upper lip,” of modern arthropods. The fossils also confirm an earlier hypothesis suggesting that the labrum must have originally evolved from the grasping appendages of Radiodonta, a group of stem-arthropods that were top predators during the Cambrian period.
“When compared with other, similar fossil material belonging to more advanced lineages, the organization of the Leanchoilia brain demonstrates that the ganglionic arrangement of the early brain underwent condensation and fusion of its components, which explains why in living species the prosocerebrum cannot be individually distinguished,” Strausfeld said.
Implications for Brain Evolution in Vertebrates
In addition to closing a century-old gap in the understanding of arthropod brain evolution, the findings have important implications for the early evolution of vertebrate brains, Strausfeld said.
Although simple, fishlike animals existed at the same time as these now-fossilized arthropods, there are no convincing fossils of their brains and, thus, neither fossil evidence nor anatomical evidence for a prosocerebrum in vertebrates. Yet, modern studies show that genes defining the fore- mid- and hindbrains of, for example, mice correspond to genes defining the three ganglionic divisions of the arthropod brain. And in vertebrates, certain crucial centers involved in decision making and in learning and memory have some genetic correspondences with the higher centers in the arthropod brain, which originated in the ancient arthropod prosocerebrum.
Thus, it is plausible that even earlier than the Cambrian period, possibly even before the evolution of segmentally organized body plans, the common ancestor of both vertebrates and invertebrates possessed basic circuits for simple cognition and decision making. And while an ancient prosocerebral-like brain might have been present in the very early ancestors of vertebrates, no such fossil has even suggested evidence for a discrete, nonsegmental domain.
“Nevertheless, one can reasonably speculate that vertebrates have embedded in their ‘modern’ brains parts of an ancient, non-segmented brain that has so far only been demonstrable in an early arthropod, such as Leanchoilia,” Strausfeld said.
Additional co-authors on the study are Yuanlong Zhao of the Guizhou Research Center for Palaeobiology at Guizhou University in Guiyang, China; Fangchen Zhao of the State Key Laboratory of Palaeobiology and Stratigraphy of the Chinese Academy of Sciences in Nanjing, China; and You He of Shanghai Synchrotron Radiation Facility.
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Materials provided by University of Arizona. Original written by Daniel Stolte. Note: Content may be edited for style and length.
Journal Reference:
- Tian Lan, Yuanlong Zhao, Fangchen Zhao, You He, Pedro Martinez, Nicholas J. Strausfeld. Leanchoiliidae reveals the ancestral organization of the stem euarthropod brain. Current Biology, 2021; DOI: 10.1016/j.cub.2021.07.048
Study of tyrannosaur braincases shows more variation than previously thought
Among the fierce carnivores that lived during the late Cretaceous was a predator named Daspletosaurus. The massive tyrannosaur, about nine metres long, lived in the coastal forest of what is now Alberta around 75 million years ago — preceding the more famous T. rex by about 10 million years.
For the first time, scientists in Canada and Argentina have used CT scans to digitally reconstruct the brain, inner ear, and surrounding bones (known as the braincase) of two well-preserved Daspletosaurus specimens.
Their results, published online today in the Canadian Journal of Earth Sciences, counter a prevailing view that dinosaur brains and the bones enclosing and protecting them varied little within species, or among closely related species, especially when compared with changes observed in other parts of the skeleton. “Our study with the two Daspletosaurus specimens suggests otherwise,” explains Dr. Tetsuto Miyashita, palaeontologist with the Canadian Museum of Nature and senior author of the study.
“We know that tyrannosaurs had relatively good-sized brains for a dinosaur, and this study shows that this pattern holds for Daspletosaurus. Furthermore, based on the shapes of the brain, ear structure, and braincase, we suggest that these two specimens represent distinct species of daspletosaurs.”
Access to a braincase, the internal part of the skull that surrounds and protects the brain, helps unlock one of the most complex parts of dinosaur anatomy. This requires advanced medical technology such as a CT scanner to image the internal spaces hidden underneath thick bones, with the resulting hundreds of hours of work to reconstruct the brain and other fleshy parts slice by slice. Therefore, most studies on dinosaur brains have each focused on one specimen from a representative species of the group. As an exception, Tyrannosaurus rex has several such reconstructions of their brains. Now, this new study investigates two remarkably well-preserved skulls of Daspletosaurus, a much rarer tyrannosaur than T. rex.
One belongs to the original specimen of Daspletosaurus, which is prominently displayed at the Canadian Museum of Nature in Ottawa. Unearthed in 1921 along the banks of Alberta’s Red Deer River, its description in 1970 as Daspletosaurus torosus (“muscular frightful lizard)” by Dr. Dale Russell ushered in the modern era of research on tyrannosaurids. The second specimen, uncovered in 2001, is with the Royal Tyrrell Museum of Palaeontology in Alberta. Miyashita is continuing to study it with Dr. Philip Currie of the University of Alberta, another author of the study.
Study of the braincase structure and its endocranial cavity provides insights on the brain itself, as well as characteristics such as the layout of cranial nerves, and some aspects of the sensory biology such as auditory and visual anatomy that drove the life of the dinosaur.
Dr. Ariana Paulina Carabajal, a dinosaur braincase expert in Argentina and study co-author at the Instituto de Investigaciones en Biodiversidad y Medioambiente (CONICET-Universidad Nacional del Comahue), provided the detailed models of the brain and inner ear anatomy and related structures. Among the findings were the presence of large bony canals that would have transmitted thick nerve bundles that moved the eyeballs. The researchers also describe large air sacs that filled up most of the braincase bones, which is in line with the limited studies known of other tyrannosaurs.
“These cavities within the bones not only make the huge skull lighter, but also are related to the middle region of the ear,” explains Paulina Carabajal. “The cavities probably helped to amplify sound and assist the system that communicates to the left and right ears, allowing the brain to determine where a sound is coming from.”
Yet, even within the two braincases of Daspletosaurus, there were differences. “It was surprising to see so many variations in the braincases even though the skeletons are similar,” says Miyashita, who offers that their study provides a good reason to look at more braincases within similar groups of dinosaurs, or even within species.
“Researchers have looked inside so few braincases in dinosaurs, typically one each for whatever species they studied, that this reinforced the assumption that these structures don’t change much within and among species. We just haven’t looked inside enough skulls to document variation.”
Additional authors of the paper, entitled “Two braincases of Daspletosaurus (Theropoda: Tyrannosauridae): anatomy and comparison,” are Thomas Dudgeon, and Dr. Hans Larsson of McGill University, who contributed the scanning data for the Canadian Museum of Nature specimen. The study authors are grateful to the Montfort Hospital in Ottawa, the University of Alberta Hospital in Edmonton, and the Canada Diagnostic Centre in Calgary for access to their CT scanners.
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Journal Reference:
- Ariana Paulina Carabajal, Philip J. Currie, Thomas W. Dudgeon, Hans C.E. Larsson, Tetsuto Miyashita. Two braincases of Daspletosaurus (Theropoda: Tyrannosauridae): anatomy and comparison. Canadian Journal of Earth Sciences, 2021; 1 DOI: 10.1139/cjes-2020-0185
Discovery of prehistoric mammals suggests rapid evolution of mammals after dinosaur extinction
Research published today in the peer-reviewed Journal of Systematic Palaeontology describes the discovery of three new species of ancient creatures from the dawn of modern mammals, and hints at rapid evolution immediately after the mass extinction of the dinosaurs.
These prehistoric mammals roamed North America during the earliest Paleocene Epoch, within just a few hundred thousand years of the Cretaceous-Paleogene boundary that wiped out the dinosaurs. Their discovery suggests mammals diversified more rapidly after the mass extinction than previously thought.
New-to-science, the creatures discovered are Miniconus jeanninae, Conacodon hettingeri, and Beornus honeyi. They differ in size — ranging up to a modern house cat, which is much larger than the mostly mouse to rat-sized mammals that lived before it alongside the dinosaurs in North America.
Each have a suite of unique dental features that differ from each other.
Beornus honeyi, in particular has been named in homage to The Hobbit character Beorn, due to the appearance of the inflated (puffy) molars (cheek teeth).
The new group belong to a diverse collection of placental mammals called archaic ungulates (or condylarths), primitive ancestors of today’s hoofed mammals (eg, horses, elephants, cows, hippos).
Paleontologists from the University of Colorado in Boulder unearthed parts of lower jaw bones and teeth — which provide insights into the animals’ identity, lifestyle and body size.
The three new species belong to the family Periptychidae that are distinguished from other ‘condylarths’ by their teeth, which have swollen premolars and unusual vertical enamel ridges. Researchers believe that they may have been omnivores because they evolved teeth that would have allowed them to grind up plants as well as meat, however this does not rule out them being exclusively herbivores.
The mass extinction that wiped out the non-avian dinosaurs 66 million years ago is generally acknowledged as the start of the ‘Age of Mammals’ because several types of mammal appeared for the first time immediately afterwards.
As lead author Madelaine Atteberry from the University of Colorado Geological Sciences Department in the USA explains, “When the dinosaurs went extinct, access to different foods and environments enabled mammals to flourish and diversify rapidly in their tooth anatomy and evolve larger body size. They clearly took advantage of this opportunity, as we can see from the radiation of new mammal species that took place in a relatively short amount of time following the mass extinction.”
Atteberry and co-author Jaelyn Eberle, a curator in the Museum of Natural History and Professor of Geological Sciences at the University of Colorado, studied the teeth and lower jaw bones of 29 fossil ‘condylarth’ species to determine the anatomical differences between the species, and used phylogenetic techniques to understand how the species are related to each other and to other early Paleocene ‘condylarths’ in the western United States.
The evidence supports the discovery of these three new species to science.
About the size of a marmot or house cat, Beornus honeyi was the largest; Conacodon hettingeri is similar to other species of Conacodon, but differs in the morphology of its last molar, while Miniconus jeanninae is similar in size to other small, earliest Paleocene ‘condylarths’, but is distinguished by a tiny cusp on its molars called a parastylid.
“Previous studies suggest that in the first few hundred thousand years after the dinosaur extinction (what is known in North America as the early Puercan) there was relatively low mammal species diversity across the Western Interior of North America, but the discovery of three new species in the Great Divide Basin suggests rapid diversification following the extinction,” says Atteberry. “These new periptychid ‘condylarths’ make up just a small percentage of the more than 420 mammalian fossils uncovered at this site. We haven’t yet fully captured the extent of mammalian diversity in the earliest Paleocene, and predict that several more new species will be described.”
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Journal Reference:
- Madelaine R. Atteberry, Jaelyn J. Eberle. New earliest Paleocene (Puercan) periptychid ‘condylarths’ from the Great Divide Basin, Wyoming, USA. Journal of Systematic Palaeontology, 2021; 1 DOI: 10.1080/14772019.2021.1924301
Researchers find a ‘fearsome dragon’ that soared over outback Queensland
Australia’s largest flying reptile has been uncovered, a pterosaur with an estimated seven-metre wingspan that soared like a dragon above the ancient, vast inland sea once covering much of outback Queensland.
University of Queensland PhD candidate Tim Richards, from the Dinosaur Lab in UQ’s School of Biological Sciences, led a research team that analysed a fossil of the creature’s jaw, discovered on Wanamara Country, near Richmond in North West Queensland.
“It’s the closest thing we have to a real life dragon,” Mr Richards said.
“The new pterosaur, which we named Thapunngaka shawi, would have been a fearsome beast, with a spear-like mouth and a wingspan around seven metres.
“It was essentially just a skull with a long neck, bolted on a pair of long wings.
“This thing would have been quite savage.
“It would have cast a great shadow over some quivering little dinosaur that wouldn’t have heard it until it was too late.”
Mr Richards said the skull alone would have been just over one metre long, containing around 40 teeth, perfectly suited to grasping the many fishes known to inhabit Queensland’s no-longer-existent Eromanga Sea.
“It’s tempting to think it may have swooped like a magpie during mating season, making your local magpie swoop look pretty trivial — no amount of zip ties would have saved you.
“Though, to be clear, it was nothing like a bird, or even a bat — Pterosaurs were a successful and diverse group of reptiles — the very first back-boned animals to take a stab at powered flight.”
The new species belonged to a group of pterosaurs known as anhanguerians, which inhabited every continent during the latter part of the Age of Dinosaurs.
Being perfectly adapted to powered flight, pterosaurs had thin-walled and relatively hollow bones.
Given these adaptations their fossilised remains are rare and often poorly preserved.
“It’s quite amazing fossils of these animals exist at all,” Mr Richards said.
“By world standards, the Australian pterosaur record is poor, but the discovery of Thapunngaka contributes greatly to our understanding of Australian pterosaur diversity.”
It is only the third species of anhanguerian pterosaur known from Australia, with all three species hailing from western Queensland.
Dr Steve Salisbury, co-author on the paper and Mr Richard’s PhD supervisor, said what was particularly striking about this new species of anhanguerian was the massive size of the bony crest on its lower jaw, which it presumably had on the upper jaw as well.
“These crests probably played a role in the flight dynamics of these creatures, and hopefully future research will deliver more definitive answers,” Dr Salisbury said.
The fossil was found in a quarry just northwest of Richmond in June 2011 by Len Shaw, a local fossicker who has been ‘scratching around’ in the area for decades.
The name of the new species honours the First Nations peoples of the Richmond area where the fossil was found, incorporating words from the now-extinct language of the Wanamara Nation.
“The genus name, Thapunngaka, incorporates thapun [ta-boon] and ngaka [nga-ga], the Wanamara words for ‘spear’ and ‘mouth’, respectively,” Dr Salisbury said.
“The species name, shawi, honours the fossil’s discoverer Len Shaw, so the name means ‘Shaw’s spear mouth’.”
The fossil of Thapunngaka shawi is on display at Kronosaurus Korner in Richmond.
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Journal Reference:
- Timothy M. Richards, Paul E. Stumkat, Steven W. Salisbury. A new species of crested pterosaur (Pterodactyloidea, Anhangueridae) from the Lower Cretaceous (upper Albian) of Richmond, North West Queensland, Australia. Journal of Vertebrate Paleontology, 2021; e1946068 DOI: 10.1080/02724634.2021.1946068
Sharp size reduction in dinosaurs that changed diet to termites
Dinosaurs were generally huge, but a new study of the unusual alvarezsaurs show that they reduced in size about 100 million years ago when they became specialised ant-eaters.
The new work is led by Zichuan Qin, a PhD student at the University of Bristol and Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. He measured body sizes of dozens of specimens and showed that they ranged in size from 10-70 kg, the size of a large turkey to a small ostrich, for most of their existence and then plummeted rapidly to chicken-sized animals at the same time as they adopted a remarkable new diet: ant-eating.
The alvarezsaurs lived from the Late Jurassic to Late Cretaceous (160 to 70 million years ago) in many parts of the world, including China, Mongolia, and South America. They were slender, two-legged predators for most of their time on Earth, pursuing lizards, early mammals, and baby dinosaurs as their diet.
“Perhaps competition with other dinosaurs intensified through the Cretaceous,” says Prof Michael Benton, one of Zichuan’s supervisors, at Bristol’s School of Earth Sciences. “The Cretaceous was a time of rapidly evolving ecosystems and the biggest change was the gradual takeover by flowering plants. Flowering plants changed the nature of the landscape completely, and yet dinosaurs mostly did not feed on these new plants. But they led to an explosion of new types of insects, including ants and termites.”
This restructuring of ecosystems has been called the Cretaceous Terrestrial Revolution, marking the time when modern-style forests and woodlands emerged, with diverse plants and animals, including insects that specialised to pollinate the new flowers and to feed on their leaves, petals and nectar.
A key problem with many alvarezsaur specimens, especially the chicken-sized ones, was to be sure they were all adults. “Some of the skeletons clearly came from juveniles,” says Dr Qi Zhao, a co-author and an expert on bone histology, “and we could tell this from sections through the bone. These showed the ages of the dinosaurs when they died, depending on the number of growth rings in the bone. We were able to identify that some specimens came from babies and juveniles and so we left them out of the calculations.”
Ant-eating might seem an amazing diet for dinosaurs. “This was suggested years ago when the arms of Mononykus were reported from Mongolia,” says Professor James Clark in Washington, DC, a co-author of this paper, and also one of the first discoverers of tiny alvarezsaurs from Mongolia. “Mononykus was one of the small alvarezsaurs, just about 1 metre long, but probably weighing 4-5 kilograms, a decent-sized Christmas turkey. Its arm was short and stout and it had lost all but one of its fingers which was modified as a short spike. It looked like a punchy little arm, no good for grabbing things, but ideal for punching a hole in the side of a termite mound.”
“Interestingly, alvarezsaur dinosaurs were indeed not small in size or ant eaters at start,” says Professor Jonah Choiniere in South Africa, a co-author of this paper, who was first to report the earliest alvarezsaurs in China. “Their ancestors, like Haplocheirus, are relatively large, close to the size of a small ostrich, and their sharp teeth, flexible forelimbs and big eyes suggest they had a mixed diet.”
Zichuan Qin took all the measurements of body size and mapped these across a dated evolutionary tree of the alvarezsaurs. “My calculations show how body sizes went up and down for the first 90 million years they existed, ranging from turkey to ostrich-sized, and averaging 30-40 kg,” says Zichuan. “Then, 95 million years ago, their body size suddenly dropped to 5 kg, and their claw shapes changed from grabbing and cutting to punching.”
“This is a very strange result, but it seems to be true,” says Professor Xing Xu, a co-supervisor to Zichuan in Beijing. “All other dinosaurs were getting bigger and bigger, but one group of flesh-eaters miniaturized, and this was associated with living in trees and flying. They eventually became birds. We’ve identified a second miniaturization event — but it wasn’t for flight, but to accommodate a completely new diet, switching from flesh to termites.”
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Journal Reference:
- Zichuan Qin, Qi Zhao, Jonah N. Choiniere, James M. Clark, Michael J. Benton, Xing Xu. Growth and miniaturization among alvarezsauroid dinosaurs. Current Biology, 2021; DOI: 10.1016/j.cub.2021.06.013
New beetle species found pristinely preserved in fossilized dropping of dinosaur ancestor
Fossilized feces are common finds at paleontological dig sites and might actually contain hidden treasures. By scanning fossilized dung assigned to a close dinosaur relative from the Triassic period, scientists discovered a 230-million-year-old beetle species, representing a new family of beetles, previously unknown to science. The beetles were preserved in a 3D state with their legs and antennae fully intact. The finding appears June 30 in the journal Current Biology.
The discovery that fossilized droppings, also known as coprolites, can preserve ancient insect species offers a new alternative to amber fossils — fossilized tree resin, which normally yield the best-preserved insect fossils. The oldest insect fossils from amber, however, are approximately 140-million-years old, and thus from relatively recent geological times. With coprolites, researchers can now look even further into the past, allowing them to learn more about insect evolution and food webs of yet unexplored time intervals.
“We didn’t know how insects looked in the Triassic period and now we have the chance,” says Martin Fiká?ek (@fikacek_martin), an entomologist at National Sun Yat-sen University, Taiwan and a co-author on the paper. “Maybe, when many more coprolites are analyzed, we will find that some groups of reptiles produced coprolites that are not really useful, while others have coprolites full of nicely preserved insects that we can study. We simply need to start looking inside coprolites to get at least some idea.”
“I was really amazed to see how well preserved the beetles were, when you modeled them up on the screen, it was like they were looking right at you,” says first author Martin Qvarnström (@M_Qvarnstroem), a paleontologist at Uppsala University, Sweden and a postdoctoral fellow in the lab of Per Ahlberg. “This is facilitated by coprolites’ calcium phosphatic composition. This together with early mineralization by bacteria likely helped to preserve these delicate fossils.”
The research team named the new beetle species Triamyxa coprolithica, which refers to its Triassic age and indicating that it belongs to the suborder Myxophaga — whose modern rep-resentatives are small and live on algae in wet environments — and that it was found in a cop-rolite. Triamyxa likely lived in semiaquatic or humid environments and were likely consumed by Silesaurus opolensis — the probable producer of the coprolite — a beaked dinosaur ancestor about 2 meters long and 15 kilograms that lived in what is now Poland at the same time.
“Although Silesaurus appears to have ingested numerous individuals of Triamyxa coprolithi-ca, the beetle was likely too small to have been the only targeted prey,” says Qvarnström. “Instead, Triamyxa likely shared its habitat with larger beetles, which are represented by disarticulated remains in the coprolites, and other prey, which never ended up in the copro-lites in a recognizable shape. So it seems likely that Silesaurus was omnivorous, and that a part of its diet was comprised of insects.”
The coprolite was scanned using synchrotron microtomography at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The method, which works like a CT scanner in a hospital except with strong x-ray beams, makes it possible to visualize internal structures in fossils in three dimensions with great contrast and resolution,
“So if you find an insect in the coprolite, you can scan it using microCT in the same way as we do with amber insects, and you can see all the tiny details of the insect body as we do in amber,” says Fiká?ek. “In that aspect, our discovery is very promising, it basically tells people: ‘Hey, check more coprolites using microCT, there is a good chance to find insects in it, and if you find it, it can be really nicely preserved.'”
“There are heaps of things you can study based on fossilized droppings but it had been hard to understand what to do with it, hard to recognize what is inside, and hard to draw conclusions from it, but now there are tons of data,” says Qvarnström. “The ultimate goal is to use the coprolite data to reconstruct ancient food webs and see how they changed across time.”
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Journal Reference:
- Martin Qvarnström, Martin Fikáček, Joel Vikberg Wernström, Sigrid Huld, Rolf G. Beutel, Emmanuel Arriaga-Varela, Per E. Ahlberg, Grzegorz Niedźwiedzki. Exceptionally preserved beetles in a Triassic coprolite of putative dinosauriform origin. Current Biology, 2021; DOI: 10.1016/j.cub.2021.05.015
Dinosaurs were in decline before the end
The death of the dinosaurs 66 million years ago was caused by the impact of a huge asteroid on the Earth. However, palaeontologists have continued to debate whether they were already in decline or not before the impact.
In a new study, published today in the journal Nature Communications, an international team of scientists, which includes the University of Bristol, show that they were already in decline for as much as ten million years before the final death blow.
Lead author, Fabien Condamine, a CNRS researcher from the Institut des Sciences de l’Evolution de Montpellier (France), said: “We looked at the six most abundant dinosaur families through the whole of the Cretaceous, spanning from 150 to 66 million years ago, and found that they were all evolving and expanding and clearly being successful.
“Then, 76 million years ago, they show a sudden downturn. Their rates of extinction rose and in some cases the rate of origin of new species dropped off.”
The team used Bayesian modelling techniques to account for several kinds of uncertainties such as incomplete fossil records, uncertainties over age-dating the fossils, and uncertainties about the evolutionary models. The models were each run millions of times to consider all these possible sources of error and to find whether the analyses would converge on an agreed most probable result.
Guillaume Guinot, also of the Institut des Sciences de l’Evolution de Montpellier, who helped run the calculations, added: “In all cases, we found evidence for the decline prior to the bolide impact.
“We also looked at how these dinosaur ecosystems functioned, and it became clear that the plant-eating species tended to disappear first, and this made the latest dinosaur ecosystems unstable and liable to collapse if environmental conditions became damaging.”
Phil Currie, a co-author of the study, from the University of Edmonton (Alberta, Canada), said: “We used over 1,600 carefully checked records of dinosaurs through the Cretaceous.
“I have been collecting dinosaurs in North America, Mongolia, China, and other areas for some time, and I have seen huge improvements in our knowledge of the ages of the dinosaur-bearing rock formations.
“This means that the data are getting better all the time. The decline in dinosaurs in their last ten million years makes sense, and indeed this is the best-sampled part of their fossil record as our study shows.”
Professor Mike Benton from the University of Bristol’s School of Earth Sciences, another co-author, added: “In the analyses, we explored different kinds of possible causes of the dinosaur decline.
“It became clear that there were two main factors, first that overall climates were becoming cooler, and this made life harder for the dinosaurs which likely relied on warm temperatures.
“Then, the loss of herbivores made the ecosystems unstable and prone to extinction cascade. We also found that the longer-lived dinosaur species were more liable to extinction, perhaps reflecting that they could not adapt to the new conditions on Earth.”
Fabien Condamine added: “This was a key moment in the evolution of life. The world had been dominated by dinosaurs for over 160 million years, and as they declined other groups began their rise to dominance, including the mammals.
“The dinosaurs were mostly so huge they probably hardly knew that the furry little mammals were there in the undergrowth. But the mammals began to increase in numbers of species before the dinosaurs had gone, and then after the impact they had their chance to build new kinds of ecosystems which we see today.”
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Journal Reference:
- Fabien L. Condamine, Guillaume Guinot, Michael J. Benton, Philip J. Currie. Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures. Nature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-23754-0
Research team discovers Arctic dinosaur nursery
Images of dinosaurs as cold-blooded creatures needing tropical temperatures could be a relic of the past.
University of Alaska Fairbanks and Florida State University scientists have found that nearly all types of Arctic dinosaurs, from small bird-like animals to giant tyrannosaurs, reproduced in the region and likely remained there year-round.
Their findings are detailed in a new paper published in the journal Current Biology.
“It wasn’t long ago that people were pretty shocked to find out that dinosaurs lived up in the Arctic 70 million years ago,” said Pat Druckenmiller, the paper’s lead author and director of the University of Alaska Museum of the North. “We now have unequivocal evidence they were nesting up there as well. This is the first time that anyone has ever demonstrated that dinosaurs could reproduce at these high latitudes.”
The findings counter previous hypotheses that the animals migrated to lower latitudes for the winter and laid their eggs in those warmer regions. It’s also compelling evidence that they were warm-blooded.
For more than a decade, Druckenmiller and Gregory Erickson, a Florida State University professor of biological science, have conducted fieldwork in the Prince Creek Formation in northern Alaska. They have unearthed many dinosaur species, most of them new to science, from the bluffs above the Colville River.
Their latest discoveries are tiny teeth and bones from seven species of perinatal dinosaurs, a term that describes baby dinosaurs that are either just about to hatch or have just hatched.
“One of the biggest mysteries about Arctic dinosaurs was whether they seasonally migrated up to the North or were year-round denizens,” said Erickson, a co-author of the paper. “We unexpectedly found remains of perinates representing almost every kind of dinosaur in the formation. It was like a prehistoric maternity ward.”
Recovering the bones and teeth, some no larger than the head of a pin, requires perseverance and a sharp eye. In the field, the scientists hauled buckets of sediment from the face of the bluffs down to the river’s edge, where they washed the material through smaller and smaller screens to remove large rocks and soil.
Once back at their labs, Druckenmiller, Erickson and co-author Jaelyn Eberle from the University of Colorado, Boulder, screened the material further. Then, teaspoon by teaspoon, the team, which included graduate and undergraduate students, examined the remaining sandy particles under microscopes to find the bones and teeth.
“Recovering these tiny fossils is like panning for gold,” Druckenmiller said. “It requires a great amount of time and effort to sort through tons of sediment grain-by-grain under a microscope. The fossils we found are rare but are scientifically rich in information.”
Next, the scientists worked with Caleb Brown and Don Brinkman from the Royal Tyrrell Museum of Palaeontology in Alberta, Canada, to compare the fossils to those from other sites at lower latitudes. Those comparisons helped them conclude that the bones and teeth were from perinatal dinosaurs.
Once they knew the dinosaurs were nesting in the Arctic, they realized the animals lived their entire lives in the region.
Erickson’s previous research revealed that the incubation period for these types of dinosaurs ranges from three to six months. Because Arctic summers are short, even if the dinosaurs laid their eggs in the spring, their offspring would be too young to migrate in the fall.
Global temperatures were much warmer during the Cretaceous, but the Arctic winters still would have included four months of darkness, freezing temperatures, snow and little fresh vegetation for food.
“As dark and bleak as the winters would have been, the summers would have had 24-hour sunlight, great conditions for a growing dinosaur if it could grow quickly enough before winter set in,” said Brown, a paleontologist at the Royal Tyrrell Museum.
Year-round Arctic residency provides a natural test of the animals’ physiology, Erickson added.
“We solved several long-standing mysteries about the dinosaur reign, but opened up a new can of worms,” he said. “How did they survive Arctic winters?”
“Perhaps the smaller ones hibernated through the winter,” Druckenmiller said. “Perhaps others lived off poor-quality forage, much like today’s moose, until the spring.”
Scientists have found warm-blooded animal fossils in the region, but no snakes, frogs or turtles, which were common at lower latitudes. That suggests the cold-blooded animals were poorly suited for survival in the cold temperatures of the region.
“This study goes to the heart of one of the longest-standing questions among paleontologists: Were dinosaurs warm-blooded?” Druckenmiller said. “We think that endothermy was probably an important part of their survival.”
This research was supported by the National Science Foundation.
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Materials provided by University of Alaska Fairbanks. Note: Content may be edited for style and length.
Journal Reference:
- Patrick S. Druckenmiller, Gregory M. Erickson, Donald Brinkman, Caleb M. Brown, Jaelyn J. Eberle. Nesting at extreme polar latitudes by non-avian dinosaurs. Current Biology, 2021; DOI: 10.1016/j.cub.2021.05.041
Footprints discovered from the last dinosaurs to walk on UK soil
Footprints from at least six different species of dinosaur — the very last dinosaurs to walk on UK soil 110 million years ago — have been found in Kent, a new report has announced.
The discovery of dinosaur footprints by a curator from Hastings Museum and Art Gallery and a scientist from the University of Portsmouth is the last record of dinosaurs in Britain.
The footprints were discovered in the cliffs and on the foreshore in Folkestone, Kent, where stormy conditions affect the cliff and coastal waters, and are constantly revealing new fossils.
Professor of Palaeobiology, David Martill, said: “This is the first time dinosaur footprints have been found in strata known as the ‘Folkestone Formation’ and it’s quite an extraordinary discovery because these dinosaurs would have been the last to roam in this country before becoming extinct.
“They were walking around close to where the White Cliffs of Dover are now — next time you’re on a ferry and you see those magnificent cliffs just imagine that!”
The footprint fossils formed by sediment filling the impression left behind when a dinosaur’s foot pushes into the ground, which then preserves it.
The footprints are from a variety of dinosaurs, which shows there was a relatively high diversity of dinosaurs in southern England at the end of the Early Cretaceous period, 110 million years ago.
They are thought to be from ankylosaurs, rugged-looking armoured dinosaurs which were like living tanks; theropods, three-toed flesh-eating dinosaurs like the Tyrannosaurus rex; and ornithopods, plant-eating ‘bird-hipped’ dinosaurs so-called because of their pelvic structure being a little bit similar to birds.
Philip Hadland, Collections and Engagement Curator at the Hastings Museum and Art Gallery is lead author on the paper. He said: “Back in 2011, I came across unusual impressions in the rock formation at Folkestone. They seemed to be repeating and all I could think was they might be footprints.
“This was at odds with what most geologists say about the rocks here, but I went looking for more footprints and as the tides revealed more by erosion, I found even better ones. More work was needed to convince the scientific community of their validity, so I teamed up with experts at the University of Portsmouth to verify what I’d found.”
Most of the findings are isolated footprints, but one discovery comprises six footprints — making a ‘trackway’, which is more than one consecutive print from the same animal.
This trackway of prints are similar in size to an elephant footprint and have been identified as likely to be an Ornithopodichnus, of which similar, but smaller-sized footprints have also been found in China from the same time period.
The largest footprint found — measuring 80 cm in width and 65 cm in length — has been identified as belonging to an Iguanodon-like dinosaur. Iguanodons were also plant-eaters, grew up to 10 metres long and walked on both two legs or on all fours.
Professor Martill said: “To find such an array of species in one place is fascinating. These dinosaurs probably took advantage of the tidal exposures on coastal foreshores, perhaps foraging for food or taking advantage of clear migration routes.”
In the Late Cretaceous period, this part of Kent, and indeed much of the United Kingdom was beneath a shallow sea, but this study also shows unequivocally that the Folkestone Formation was inter-tidal.
Mr Hadland said: “Aside from finding that dinosaurs went to the seaside just like their modern relatives the birds, we have also found new evidence that changes the interpretation of the geology of the Folkestone Formation strata.
“It just goes to show that what has been previously published about the geology of an area isn’t always correct and new insights can be made. There is also the potential for almost anyone to make a discovery that adds to scientific knowledge from publicly accessible geological sites.”
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Materials provided by University of Portsmouth. Note: Content may be edited for style and length.
Journal Reference:
- Philip T. Hadland, Steve Friedrich, Abdelouahed Lagnaoui, David M. Martill. The youngest dinosaur footprints from England and their palaeoenvironmental implications. Proceedings of the Geologists’ Association, 2021; DOI: 10.1016/j.pgeola.2021.04.005