Dinosaurs could get cancer


This 4 August 2020 video, in Indonesian, is about the recent discovery that a Centrosaurus dinosaur had bone cancer.

Translated from Dutch NOS radio today:

Canadian scientists have for the first time found evidence that dinosaurs could also develop bone cancer.

Paleontologists discovered this when they re-examined malformations on the fossil of a Centrosaurus – a horned, herbivorous dinosaur that lived in the Cretaceous period more than 70 million years ago.

The fossil was excavated in the Canadian province of Alberta in 1989 and was notable for a fibula defect, which was then assessed by scientists as a healed fracture. New research with detailed CT scans found it likely to be an aggressive form of bone cancer.

The tumor was the size of an apple, the scientists said in an article in the scientific journal Lancet Oncology.

Triassic dinosaurs family tree, new research


This 2016 video says about itself:

Triassic Age Of Dinosaur – AMAZING DINOSAURS DOCUMENTARY

Dinosaurs are a diverse group of animals of the clade Dinosauria. They first appeared during the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the start of the Jurassic (about 200 million years ago) until the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups at the end of the Mesozoic Era.

The fossil record indicates that birds are modern feathered dinosaurs, having evolved from theropod ancestors during the Jurassic Period. Birds were the only dinosaurs to survive the extinction event that occurred 66 million years ago.

From the Massachusetts Institute of Technology in the USA:

Study sheds light on the evolution of the earliest dinosaurs

Geological evidence suggests the known dinosaur groups diverged early on, supporting the traditional dinosaur family tree

July 29, 2020

Summary: Geological evidence suggests the known dinosaur groups diverged early on, supporting the traditional dinosaur family tree.

The classic dinosaur family tree has two subdivisions of early dinosaurs at its base: the Ornithischians, or bird-hipped dinosaurs, which include the later Triceratops and Stegosaurus; and the Saurischians, or lizard-hipped dinosaurs, such as Brontosaurus and Tyrannosaurus.

In 2017, however, this classical view of dinosaur evolution was thrown into question with evidence that perhaps the lizard-hipped dinosaurs evolved first — a finding that dramatically rearranged the first major branches of the dinosaur family tree.

Now an MIT geochronologist, along with paleontologists from Argentina and Brazil, has found evidence to support the classical view of dinosaur evolution. The team’s findings are published today in the journal Scientific Reports.

The team reanalyzed fossils of Pisanosaurus, a small bipedal dinosaur that is thought to be the earliest preserved Ornithiscian in the fossil record. The researchers determined that the bird-hipped herbivore dates back to 229 million years ago, which is also around the time that the earliest lizard-hipped Saurischians are thought to have appeared.

The new timing suggests that Ornithiscians and Saurischians first appeared and diverged from a common ancestor at roughly the same time, giving support to the classical view of dinosaur evolution.

The researchers also dated rocks from the Ischigualasto Formation, a layered sedimentary rock unit in Argentina that is known for having preserved an abundance of fossils of the very earliest dinosaurs. Based on these fossils and others across South America, scientists believe that dinosaurs first appeared in the southern continent, which at the time was fused together with the supercontinent of Pangaea. The early dinosaurs are then thought to have diverged and fanned out across the world.

However, in the new study, the researchers determined that the period over which the Ischigualasto Formation was deposited overlaps with the timing of another important geological deposit in North America, known as the Chinle Formation.

The middle layers of the Chinle Formation in the southwestern U.S. contain fossils of various fauna, including dinosaurs that appear to be more evolved than the earliest dinosaurs. The bottom layers of this formation, however, lack animal fossil evidence of any kind, let alone early dinosaurs. This suggests that conditions within this geological window prevented the preservation of any form of life, including early dinosaurs, if they walked this particular region of the world.

“If the Chinle and Ischigualasto formations overlap in time, then early dinosaurs may not have first evolved in South America, but may have also been roaming North America around the same time,” says Jahandar Ramezani, a research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, who co-authored the study. “Those northern cousins just may not have been preserved.”

The other researchers on the study are first author Julia Desojo from the National University of La Plata Museum, and a team of paleontologists from institutions across Argentina and Brazil.

“Following footsteps”

The earliest dinosaur fossils found in the Ischigualasto Formation are concentrated within what is now a protected provincial park known as “Valley of the Moon” in the San Juan Province. The geological formation also extends beyond the park, albeit with fewer fossils of early dinosaurs. Ramezani and his colleagues instead looked to study one of the accessible outcrops of the same rocks, outside of the park.

They focused on Hoyada del Cerro Las Lajas, a less-studied outcrop of the Ischigualasto Formation, in La Rioja Province, which another team of paleontologists explored in the 1960s.

“Our group got our hands on some of the field notes and excavated fossils from those early paleontologists, and thought we should follow their footsteps to see what we could learn,” Desojo says.

Over four expeditions between 2013 to 2019, the team collected fossils and rocks from various layers of the Las Lajas outcrop, including more than 100 new fossil specimens, though none of these fossils were of dinosaurs. Nevertheless, they analyzed the fossils and found they were comparable, in both species and relative age, to nondinosaur fossils found in the park region of the same Ischigualasto Formation. They also found out that the Ischigualasto Formation in Las Lajas was significantly thicker and much more complete than the outcrops in the park. This gave them confidence that the geological layers in both locations were deposited during the same critical time interval.

Ramezani then analyzed samples of volcanic ash collected from several layers of the Las Lajas outcrops. Volcanic ash contains zircon, a mineral that he separated from the rest of the sediment, and measured for isotopes of uranium and lead, the ratios of which yield the mineral’s age.

With this high-precision technique, Ramezani dated samples from the top and bottom of the outcrop, and found that the sedimentary layers, and any fossils preserved within them, were deposited between 230 million and 221 million years ago. Since the team determined that the layered rocks in Las Lajas and the park match in both species and relative timing, they could also now determine the exact age of the park’s more fossil-rich outcrops.

Moreover, this window overlaps significantly with the time interval over which sediments were deposited, thousands of kilometers northward, in the Chinle Formation.

“For many years, people thought Chinle and Ischigualasto formations didn’t overlap, and based on that assumption, they developed a model of diachronous evolution, meaning the earliest dinosaurs appeared in South America first, then spread out to other parts of the world including North America,” Ramezani says. “We’ve now studied both formations extensively, and shown that diachronous evolution isn’t really based on sound geology.”

A family tree, preserved

Decades before Ramezani and his colleagues set out for Las Lajas, other paleontologists had explored the region and unearthed numerous fossils, including remains of Pisanosaurus mertii, a small, light-framed, ground-dwelling herbivore. The fossils are now preserved in an Argentinian museum, and scientists have gone back and forth on whether it is a true dinosaur belonging to the Ornithiscian group, or a ” basal dinosauromorph” — a kind of pre-dinosaur, with features that are almost, but not quite fully, dinosaurian.

“The dinosaurs we see in the Jurassic and Cretaceous are highly evolved, and ones we can nicely identify, but in the late Triassic, they all looked very much alike, so it’s very hard to distinguish them from each other, and from basal dinosauromorphs,” Ramezani explains.

His collaborator Max Langer from the University of São Paulo in Brazil painstakingly reanalyzed the museum-preserved fossil of Pisanosaurus, and concluded, based on certain key anatomical features, that it is indeed a dinosaur — and what’s more, that it is the earliest preserved Ornithiscian specimen. Based on Ramezani’s dating of the outcrop and the interpretation of Pisanosaurus, the researchers concluded that the earliest bird-hipped dinosaurs appeared around 229 million years ago — around the same time as their lizard-hipped counterparts.

“We can now say the earliest Ornithiscians first showed up in the fossil record roughly around the same time as the Saurischians, so we shouldn’t throw away the conventional family tree,” Ramezani says. “There are all these debates about where dinosaurs appeared, how they diversified, what the family tree looked like. A lot of those questions are tied to geochronology, so we need really good, robust age constraints to help answer these questions.”

This research was mainly funded by the National Council for Scientific and Technical Research (Argentina) and the São Paulo State Research Support Foundation (Brazil). Geochronologic research at the MIT Isotope Lab has been supported in part by the U.S. National Science Foundation.

Prehistoric amphibians, four or five fingers?


This 2016 video says about itself:

OSTEOHISTOLOGICAL AND COMPUTED FEA OF METOPOSAURUS KRASIEJOWENSIS SKULL BIOMECHANICS

By Kamil Gruntmejer

Recorded at XIV Annual Meeting of the European Association of Vertebrate Palaeontologists, Teylers Museum, Haarlem, Netherlands.

From the University of Bonn in Germany:

Fossil tracks: Wrong number of fingers leads down wrong track

July 24, 2020

Have you ever wondered why our hands have five fingers? And what about amphibians? They usually only have four. Until now it was assumed that this was already the case with the early ancestors of today’s frogs and salamanders, the Temnospondyli. However, a new find of the crocodile-like Temnospondyl Metoposaurus krasiejowensis from the late Triassic (about 225 million years old) in Poland shows five metacarpal bones and thus five fingers. As the researchers from the Universities of Bonn and Opole (Poland) note, this finding is very important, because until now, fossil animal tracks may have been wrongly assigned. The results have now been published in the Journal of Anatomy.

Modern amphibians usually have four fingers on the forelimb (and never more), which is called a “four-rayed hand,” as opposed to our five-rayed hand. Of all groups of terrestrial vertebrates, amphibians show the greatest variation in the number of frontfingers. Reptiles are the most conservative and usually have five. In birds, the finger bones in the wing have been lost completely. In mammals, the number of toes in the forelimb also varies greatly: Primates and raccoons have five, in horses only the third has survived, while in cattle and other even-toed ungulates fingers three and four remain. What they all have in common, however, is that this loss of toes or fingers originates from a five-ray pattern, which is why amphibians cannot be the ancestors of all these terrestrial vertebrate groups.

Exact number of toes is controversial

It has been known for some time that the earliest quadrupeds had significantly more fingers than five, such as Acanthostega, which had eight in the forelimb, or Ichthyostega with seven in the hind foot. As early as 300 million years ago, all but the five-fingered forms became extinct. The five-ray pattern was then retained in the real land animals, but was reduced again and again (see horses). The ancestors of today’s amphibians, the Temnospondyli, presented contradictory evidence of skeletons with four fingers, but also tracks that had five.

Temnospondyli is an important group of the early, very diverse quadrupeds. Some temnospondyls became as big as crocodiles, others were rather small. However, like all amphibians, they were dependent on water during their larval stage. Their most famous representatives include Eryops or Mastodonsaurus. “It’s also important to understand the evolution of modern amphibians, as this group probably evolved from the Temnospondyli,” says Dr. Dorota Konietzko-Meier from the Institute for Geosciences at the University of Bonn, who discovered and prepared the left forelimb of a Metoposaurus krasiejowensis in Krasiejów (southwest Poland).

However, despite the long history of research, the exact number of fingers in Metoposaurus and other temnospondyls is still controversial. “It’s remarkable that even in the case of the very well-researched Eryops, the skeletal reconstruction exhibited at the Muséum National d’Histoire Naturelle in Paris has five fingers, while only four fingers can be seen at the National Museum of Natural History in Washington,” says Ella Teschner, a doctoral student from Bonn and Opole. Lately, science has assumed that, similar to most modern amphibians, all Temnospondyli have only four toes in their forelimbs. This resulted in the five-toed footprints common in the Permian and Triassic periods being almost automatically assumed to not belong to Temnospondyli.

“The find from the famous Upper Triassic site Krasiejów in Poland therefore offers a new opportunity to study the architecture and development of the hand of the early quadrupeds,” says paleontologist Prof. Dr. Martin Sander from the University of Bonn. A considerably broader view of the entire group of Temnospondyli did not show a clear trend with regard to the five-ray pattern and suggested that the number of digits was not as limited in the phylogenetic context as was assumed. “Evidently, the temnospondyls were already experimenting with the four-ray pattern, and the five-ray pattern died out before the emergence of modern amphibians,” adds Sander.

Five fingers on each hand?

“Even if the ossification of five metacarpal bones described here was only a pathology, it still shows that a five-ray pattern was possible in Temnospondyli,” says Konietzko-Meier. However, it could not be assumed with certainty that the reduction in the number of fingers/digits from five to four always affected the fifth place on the hand in these fossil taxa. The possibility that some of the four-fingered taxa were caused by the loss of the first ray cannot be excluded. Sander: “The new finding of a five-fingered hand is particularly important for the interpretation of tracks, as it shows that a five-fingered forefoot print could also belong to the Temnospondyli and thus indicate a considerably wider distribution area of these animals.”

These results are also of general importance, since limb development plays an important role in evolutionary biology and medicine, and fossils may therefore provide important information for the evaluation of theories of hand development.

Beelzebufo, big dinosaur age Madagascar frog


This 22 July 2020 video says about itself:

Untangling the origins of Beelzebufo — the giant frog that lived alongside the dinosaurs — turns out to be one of the most bedeviling problems in the history of amphibians.

Triassic era catastrophes and wildlife


This 18 June 2020 video from the USA says about itself:

Big Amphibians of the Chinle Formation!

Dinosaur Journey Re-Opens today! And to celebrate we wanted to share a video of Dr. Julia McHugh talking amphibians. Ever noticed the large red rock base of Independence Monument?! Well, that’s the Triassic age rock these amazing creatures were discovered. WATCH now to learn more!

From the University of Texas at Austin in the USA:

Arizona rock core sheds light on Triassic dark ages

July 20, 2020

A rock core from Petrified Forest National Park, Arizona, has given scientists a powerful new tool to understand how catastrophic events shaped Earth’s ecosystems before the rise of the dinosaurs.

The quarter-mile core is from an important part of the Triassic Period when life on Earth endured a series of cataclysmic events: Our planet was struck at least three times by mountain-sized asteroids, chains of volcanoes erupted to choke the sky with greenhouse gases, and tectonic movement tore apart Earth’s single supercontinent, Pangea.

Among the chaos, many plants and animals, including some of the long-snouted and armored reptiles that ruled Pangea throughout the Triassic, vanished in a possible shake-up of life on Earth that scientists have yet to explain.

The study, published July 20 in GSA Bulletin, offers scientists a foundation to explain the changes in the fossil record and determine how these events may have shaped life on Earth.

By determining the age of the rock core, researchers were able to piece together a continuous, unbroken stretch of Earth’s history from 225 million to 209 million years ago. The timeline offers insight into what has been a geologic dark age and will help scientists investigate abrupt environmental changes from the peak of the Late Triassic and how they affected the plants and animals of the time.

“The core lets us wind the clock back 225 million years when Petrified Forest National Park was a tropical hothouse populated by crocodile-like reptiles and turkey-size early dinosaurs,” said Cornelia Rasmussen, a postdoctoral researcher at the University of Texas Institute for Geophysics (UTIG), who led the analysis that determined the age of the core.

“We can now begin to interpret changes in the fossil record, such as whether changes in the plant and animal world at the time were caused by an asteroid impact or rather by slow geographic changes of the supercontinent drifting apart,” she said.

Petrified Forest National Park’s paleontologist Adam Marsh said that despite a rich collection of fossils from the period in North America, until now there was little information on the Late Triassic’s timeline because most of what scientists knew came from studying outcrops of exposed rock pushed to the surface by tectonic movements.

“Outcrops are like broken pieces of a puzzle,” said Marsh, who earned his Ph.D. from The University of Texas at Austin’s Jackson School of Geosciences. “It is incredibly difficult to piece together a continuous timeline from their exposed and weathered faces.”

Marsh was not an author of the study but is part of the larger scientific coring project. UTIG is a unit of the Jackson School.

The Petrified Forest National Park core overcomes the broken puzzle problem by recovering every layer in the order it was deposited. Like tree rings, scientists can then match those layers with the fossil and climate record.

To find the age of each layer, the researchers searched the rock core for tiny crystals of the mineral zircon, which are spewed into the sky during volcanic eruptions. Zircons are a date stamp for the sediments with which they are buried. Researchers then compared the age of the crystals with traces of ancient magnetism stored in the rocks to help develop a precise geologic timeline.

Geoscience is rarely so simple, however, and according to Rasmussen, the analysis of the core gave them two slightly different stories. One shows evidence that a shake-up in the species might not be connected to any single catastrophic event and could simply be part of the ordinary course of gradual evolution. The other shows a possible correlation between the change in the fossil record and a powerful asteroid impact, which left behind a crater in Canada over 62 miles wide.

For Marsh, the different findings are just part of the process to reach the truth.

“The two age models are not problematic and will help guide future studies,” he said.

The research is the latest outcome of the Colorado Plateau Coring Project. The research and the coring project were funded by the National Science Foundation and International Continental Drilling Program.

How trilobites grew, new research


This 2017 video from the USA is called Elrathia kingi – Trilobite Fossil.

From the American Museum of Natural History:

Growth rate of common trilobites

July 15, 2020

If you’ve ever held a trilobite fossil, seen one in a classroom, or walked by one in a store, chances are it was Elrathia kingii, one of the most common and well-recognized trilobites, and collected by the hundreds of thousands in western Utah. But despite the popularity of this species, scientists had not determined how it grew — from hatchling to juvenile to adult — until now. New work from the American Museum of Natural History published today in the journal Papers in Palaeontology describes the development and growth rate of Elrathia kingii — only the second such dataset to be compiled for a trilobite — allowing for the first comparison among trilobite species.

“There’s quite a big size range among trilobites. Some never got bigger than about a centimeter, while the largest on record is 72 centimeters (28 inches),” said Melanie Hopkins, an associate curator in the Museum’s Division of Paleontology and the study’s author. “Growth-rate studies like this one can help us tackle some of the big-picture questions: How did some trilobites get so big? What was the environmental context for that? And how did body size evolve over the evolutionary history of the clade?”

Trilobites are a group of extinct marine arthropods — distantly related to the horseshoe crab — that lived for almost 300 million years. They were incredibly diverse, with more than 20,000 described species. Their fossilized exoskeletons are preserved in sites all over the world, from the United States to China. Like insects, they molted throughout their lifetimes, leaving clues to how they changed during development. But to calculate the species’ growth rate, scientists need fossils representing all stages of the animal’s life — and lots of them.

“There are tons of specimens of Elrathia kingii out there but most of them are adults, and data from exactly where they were collected is inconsistent,” Hopkins said. “I needed material that I could collect from as small a section as possible that included a lot of juveniles.”

So in May 2018, Hopkins spent five days in Utah with a crew consisting of Museum staff and volunteers at a new fossil site said to preserve bucketloads of Elrathia kingii. By the end of the trip, they had collected about 500 specimens — many of them juveniles, which can be as small as half a millimeter long — from a section of outcrop just 1.5 meters (about 5 feet) long.

Hopkins estimated the growth rate and compared it to previously published data on a different trilobite, Aulacopleura konincki — the first time two trilobite species have been compared in this way. The two species look very similar and Hopkins found that they also grow in similar ways: for example, the growth of the trunk — the area immediately below the trilobite’s head made up of segments that increase with age — was controlled by a growth gradient, with those that were younger and closer to the back of the body undergoing faster growth. But while Elrathia kingii was smaller in early development and went through fewer molts before adulthood, it had faster growth rates, ultimately reaching sizes on par with Aulacopleura konincki, the largest of which are about 4 centimeters long.

In future studies, Hopkins is planning to add growth-rate data on different, more diverse-looking trilobite species to her models.

Dinosaurs became extinct, deep-sea animals survived


This 2015 video from Canada says about itself:

Cretaceous Seas Exhibit at Mount Royal University

Cretaceous Seas is the largest marine vertebrate exhibit in Calgary. Installed from the atrium ceilings in Mount Royal’s East Gate and B-Wing, Cretaceous Seas provides students and the public the opportunity to view life-sized specimens of extinct marine reptiles and fishes that swam or flew the seas of western North America during the Cretaceous Period, more than 65 million years ago. The casts on display were constructed from molds produced from bones of marine reptiles, pterosaurs and fishes unearthed from sea bottom muds deposited in the Western Interior Seaway.

From the Geological Society of America:

Evolution after Chicxulub asteroid impact: Rapid response of life to end-cretaceous mass extinction

July 14, 2020

The impact event that formed the Chicxulub crater (Yucatán Peninsula, México) caused the extinction of 75% of species on Earth 66 million years ago, including non-avian dinosaurs. One place that did not experience much extinction was the deep, as organisms living in the abyss made it through the mass extinction event with just some changes to community structure.

New evidence from International Ocean Discovery Program (IODP) Expedition 364 of trace fossils of burrowing organisms that lived in the seafloor of the Chicxulub Crater beginning a few years after the impact shows just how quick the recovery of the seafloor ecosystem was, with the establishment of a well-developed tiered community within approximately 700,000 years after the event.

In April and May 2016, a team of international scientists drilled into the Chicxulub impact crater. This joint expedition, organized by the International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) recovered an extended syn- and post-impact set of rock cores, allowing study of the effects of the impact on life and its recovery after the mass extinction event. The end-Cretaceous (K-Pg) event has been profusely studied and its effect on biota are relatively well-known. However, the effect of these changes on the macrobenthic community, the community of organisms living on and in the seafloor that do not leave body fossils, is poorly known.

The investigators concluded that the diversity and abundance of trace fossils responded primarily to variations in the flux of organic matter (i.e., food) sinking to the seafloor during the early Paleocene. Local and regional-scale effects of the K-Pg impact included earthquakes of magnitude 10-11, causing continental and marine landslides, tsunamis hundreds of meters in height that swept more than 300 km onshore, shock waves and air blasts, and the ignition of wildfires. Global phenomena included acid rain, injection of aerosols, dust, and soot into the atmosphere, brief intense cooling followed by slight warming, and destruction of the stratospheric ozone layer, followed by a longer-term greenhouse effect.

Mass extinction events have punctuated the past 500 million years of Earth’s history, and studying them helps geoscientists understand how organisms respond to stress in their environment and how ecosystems recover from the loss of biodiversity. Although the K-Pg mass extinction was caused by an asteroid impact, previous ones were caused by slower processes, like massive volcanism, which caused ocean acidification and deoxygenation and had environmental effects that lasted millions of years.

By comparing the K-Pg record to earlier events like the end Permian mass extinction (the so-called “Great Dying” when 90% of life on Earth went extinct), geoscientists can determine how different environmental changes affect life. There are similar overall patterns of recovery after both events with distinct phases of stabilization and diversification, but with very different time frames. The initial recovery after the K-Pg, even at ground zero of the impact, lasted just a few years; this same phase lasted tens of thousands of years after the end Permian mass extinction. The overall recovery of seafloor burrowing organisms after the K-Pg took ~700,000 years, but it took several million years after the end Permian.

Prehistoric fish teeth, new research


This July 2018 video says about itself:

When Fish Wore Armor

420 million years ago, some fish were more medieval. They wore armor, sometimes made of big plates, and sometimes made of interlocking scales. But that armor may actually have served a totally different purpose, one that many animals still use today.

From the European Synchrotron Radiation Facility:

The origin of our teeth goes back more than 400 million years back in time, to the period when strange armoured fish first developed jaws and began to catch live prey. We are the descendants of these fish, as are all the other 60,000 living species of jawed vertebrates — sharks, bony fish, amphibians, reptiles, birds and mammals. An international team of scientists led by Uppsala University (Sweden), in collaboration with the ESRF, the European Synchrotron (France), the brightest X-ray source, has digitally ‘dissected’, for the first time, the most primitive jawed fish fossils with teeth found near Prague more than 100 years ago. The results, published today in Science, show that their teeth have surprisingly modern features.

Teeth in current jawed vertebrates reveal some consistent patterns: for example, new teeth usually develop on the inner side of the old ones and then move outwards to replace them (in humans this pattern has been modified so that new teeth develop below the old ones, deep inside the jawbone). There are, however, several differences between bony fish (and their descendants the land animals) and sharks; for example, the fact that sharks have no bones at all, their skeleton is made of cartilage, and neither the dentine scales nor the true teeth in the mouth attach to it; they simply sit in the skin. In bony fish and land animals, the teeth are always attached to jawbones. In addition, whilst sharks shed their worn-out teeth entire, simply by detaching them from the skin, bony fish and land animals shed theirs by dissolving away the tooth bases.

This diversity raises many questions about the origin of teeth. Until now, researchers have focused on fossils of a group of ancient fish that lived about 430 to 360 million years ago, called the arthrodires, which were the only stem jawed vertebrates in which teeth were known. However, they struggled to understand how they could have evolved into the teeth of modern vertebrates, as arthrodire teeth are so different in position and mode of tooth addition in comparison to bony fish and sharks.

Scanning the most primitive jawed fishes

A team from Uppsala University, Charles University (Czech Republic), Natural History Museum in London (UK), National Museum in Prague (Czech Republic) and the ESRF, the European Synchrotron (France) set out to determine whether this peculiar type of dentition was really ancestral to ours, or just a specialised offshoot off the lineage leading towards modern jawed vertebrates.

With this aim, they turned to the acanthothoracids, another early fish group that are believed to be more primitive than the arthrodires and closely related to the very first jawed vertebrates. The problem with acanthothoracids is that their fossils are rare and always incomplete. The very finest of them come from the Prague Basin in the Czech Republic, from rocks that are just over 400 million years old, and were collected at the turn of the last century. They have proved difficult to study by conventional techniques because the bones cannot be freed from the enclosing rock, and have therefore never been investigated in detail.

The researchers used the unique properties of the ESRF, the world’s brightest X-ray source and the synchrotron microtomography ID19’s beamline, to visualise the internal structure of the fossils in 3D without damaging them. At the ESRF, an 844 metre-ring of electrons travelling at the speed of light emits high-powered X-ray beams that can be used to non-destructively scan matter, including fossils.

“The results were truly remarkable, including well-preserved dentitions that nobody expected to be there” says Valéria Vaškaninová, lead author of the study and scientist from Uppsala University. Follow-up scans at higher resolution allowed the researchers to visualize the growth pattern and even the perfectly preserved cell spaces inside the dentine of these ancient teeth.

Like arthrodires, the acanthothoracid dentitions are attached to bones. This indicates that bony fish and land animals retain the ancestral condition in this regard, whereas sharks are specialized in having teeth that are only attached to the skin — in contrast to the common perception that sharks are primitive living vertebrates. Again, like arthrodires, the teeth of acanthothoracids were not shed.

More different from arthrodires than expected

In other ways, however, acanthothoracid dentitions are fundamentally different from those of arthrodires. Like sharks, bony fish and land animals, acanthothoracids only added new teeth on the inside; the oldest teeth were located right at the jaw margin. In this respect, the acanthothoracid dentitions look remarkably modern.

“To our surprise, the teeth perfectly matched our expectations of a common ancestral dentition for cartilaginous and bony vertebrates.” explains Vaškaninová.

The tooth-bearing bones also carry small non-biting dentine elements of the skin on their outer surfaces, a character shared with primitive bony fish but not with arthrodires. This is an important difference because it shows that acanthothoracid jaw bones were located right at the edge of the mouth, whereas arthrodire jaw bones lay further in. Uniquely, one acanthothoracid (Kosoraspis) shows a gradual shape transition from these dentine elements to the neighboring true teeth, while another (Radotina) has true teeth almost identical to its skin dentine elements in shape. This may be evidence that the true teeth had only recently evolved from dentine elements on the skin.

“These findings change our whole understanding of the origin of teeth” says co-author Per Ahlberg, professor at Uppsala University. And he adds: “Even though acanthothoracids are among the most primitive of all jawed vertebrates, their teeth are in some ways far more like modern ones than arthrodire dentitions. Their jawbones resemble those of bony fish and seem to be directly ancestral to our own. When you grin at the bathroom mirror in the morning, the teeth that grin back at you can trace their origins right back to the first jawed vertebrates.”

Oligocene prehistoric dolphin discovery


This 9 July 2020 video says about itself:

A giant 16-foot long dolphin has been discovered. It lived 25 million years ago. It feasted on … whales and it was the apex predator of the ocean

Researchers found a full skeleton of a cetacean called Ankylorhiza tiedemani. It shared many similar features with both baleen whales and modern toothed whales. This dolphin had tusk-like front teeth. It lived in present-day South Carolina. Fossil evidence includes skull anatomy and teeth, a flipper and its vertebral column. It revealed that this large dolphin was a ‘top predator’ in the community. It was very clearly preying upon large-bodied prey like a killer whale.

Ankylorhiza was a ruthless ‘ecological specialist’ when it came to hunting. At about 16 feet long, it was about twice the size of average-sized dolphins. Ankylorhiza has proportionally large teeth with thickened roots. It is an adaptation for higher bite force. The teeth have longitudinal ridges which cut through flesh more efficiently. It is also believed to be the first marine animal that used echolocation. It used sound to obtain information about surroundings and to find food.

From ScienceDaily:

15-foot-long skeleton of extinct dolphin suggests parallel evolution among whales

July 9, 2020

A report in the journal Current Biology on July 9 offers a detailed description of the first nearly complete skeleton of an extinct large dolphin, discovered in what is now South Carolina. The 15-foot-long dolphin (Ankylorhiza tiedemani comb. n.) lived during the Oligocene — about 25 million years ago — and was previously known only from a partial rostrum (snout) fossil.

The researchers say that multiple lines of evidence — from the skull anatomy and teeth, to the flipper and vertebral column — show that this large dolphin (a toothed whale in the group Odontoceti) was a top predator in the community in which it lived. They say that many features of the dolphin’s postcranial skeleton also imply that modern baleen whales and modern toothed whales must have evolved similar features independently, driven by parallel evolution in the very similar aquatic habitats in which they lived.

“The degree to which baleen whales and dolphins independently arrive at the same overall swimming adaptations, rather than these traits evolving once in the common ancestor of both groups, surprised us,” says Robert Boessenecker of the College of Charleston in Charleston, South Carolina. “Some examples include the narrowing of the tailstock, increase in the number of tail vertebrae, and shortening of the humerus (upper arm bone) in the flipper.

“This is not apparent in different lineages of seals and sea lions, for example, which evolved into different modes of swimming and have very different looking postcranial skeletons,” he adds. “It’s as if the addition of extra finger bones in the flipper and the locking of the elbow joint has forced both major groups of cetaceans down a similar evolutionary pathway in terms of locomotion.”

Though first discovered in the 1880s from a fragmentary skull during phosphate dredging of the Wando River, the first skeleton of Ankylorhiza was discovered in the 1970s by then Charleston Museum Natural History curator Albert Sanders. The nearly complete skeleton described in the new study was found in the 1990s. A commercial paleontologist by the name of Mark Havenstein found it during construction of a housing subdivision in South Carolina. It was subsequently donated to the Mace Brown Museum of Natural History, to allow for its study.

While there’s much more to learn from this fossil specimen, the current findings reveal that Ankylorhiza was an ecological specialist. The researchers say the species was “very clearly preying upon large-bodied prey like a killer whale.”

Another intriguing aspect, according to the researchers, is that Ankylorhiza is the first echolocating whale to become an apex predator. When Ankylorhiza became extinct by about 23 million years ago, they explain, killer sperm whales and the shark-toothed dolphin Squalodon evolved and reoccupied the niche within 5 million years. After the last killer sperm whales died out about 5 million years ago, the niche was left open until the ice ages, with the evolution of killer whales about 1 or 2 million years ago.

“Whales and dolphins have a complicated and long evolutionary history, and at a glance, you may not get that impression from modern species,” Boessenecker says. “The fossil record has really cracked open this long, winding evolutionary path, and fossils like Ankylorhiza help illuminate how this happened.”

Boessenecker notes that more fossils of Ankylorhiza are awaiting study, including a second species and fossils of Ankylorhiza juveniles that can offer insight into the dolphin’s growth. He says that there’s still much to learn from fossilized dolphins and baleen whales from South Carolina.

“There are many other unique and strange early dolphins and baleen whales from Oligocene aged rocks in Charleston, South Carolina,” Boessenecker says. “Because the Oligocene epoch is the time when filter-feeding and echolocation first evolved, and since marine mammal localities of that time are scarce worldwide, the fossils from Charleston offer the most complete window into the early evolution of these groups, offering unparalleled evolutionary insight.”

Extinct giant dormouse, new research


An artist’s impression of the giant dormouse Leithia melitensis (left) and its nearest living relative the garden dormouse (right). Image credit: James Sadler, University of York

From the University of York in England:

Skull of two million year-old giant dormouse reconstructed

July 9, 2020

A PhD student has produced the first digital reconstruction of the skull of a gigantic dormouse, which roamed the island of Sicily around two million years ago.

In a new study, the student from Hull York Medical School, has digitally pieced together fossilised fragments from five giant dormouse skulls to reconstruct the first known complete skull of the species.

The researchers estimate that the enormous long-extinct rodent was roughly the size of a cat, making it the largest species of dormouse ever identified.

The digitally reconstructed skull is 10 cm long — the length of the entire body and tail of many types of modern dormouse.

PhD student Jesse Hennekam said: “Having only a few fossilised pieces of broken skulls available made it difficult to study this fascinating animal accurately. This new reconstruction gives us a much better understanding of what the giant dormouse may have looked like and how it may have lived.”

The enormous prehistoric dormouse is an example of island gigantism — a biological phenomenon in which the body size of an animal isolated on an island increases dramatically.

The palaeontological record shows that many weird and wonderful creatures once roamed the Italian islands. Alongside the giant dormouse, Sicily was also home to giant swans, giant owls and dwarf elephants.

Jesse’s PhD supervisor, Dr Philip Cox from the Department of Archaeology at the University of York and Hull York Medical School, said: “While island dwarfism is relatively well understood, as with limited resources on an island, animals may need to shrink to survive, the causes of gigantism are less obvious.

“Perhaps, with fewer terrestrial predators, larger animals are able to survive as there is less need for hiding in small spaces, or it could be a case of co-evolution with predatory birds where rodents get bigger to make them less vulnerable to being scooped up in talons.”

Jesse spotted the fossilised fragments of skull during a research visit to the Palermo Museum in Italy, where a segment of rock from the floor of a small cave, discovered during the construction of a motorway in northwest Sicily in the 1970s, was on display.

“I noticed what I thought were fragments of skull from an extinct species embedded in one of the cave floor segments,” Jesse said. “We arranged for the segment to be sent to Basel, Switzerland for microCT scanning and the resulting scans revealed five fragmented skulls of giant dormice present within the rock.”

The reconstruction is likely to play an important role in future research directed at improving understanding of why some small animals evolve larger body sizes on islands, the researchers say.

“The reconstructed skull gives us a better sense of whether the giant dormouse would have looked similar to its normal-sized counterparts or whether its physical appearance would have been influenced by adaptations to a specific environment,” Jesse explains.

“For example, if we look at the largest living rodent — the capybara — we can see that it has expanded in size on a different trajectory to other species in the same family.”

Jesse is also using biomechanical modelling to understand the feeding habits of the giant dormouse.

“At that size, it is possible that it may have had a very different diet to its smaller relatives,” he adds.