Scientists from the University of Tel Aviv in collaboration with colleagues from the University of Napoli have published a study that suggests having a small brain relative to your body size predisposed Late Quaternary mammals to extinction. If you were a “smart” mammal, with a relatively big brain in proportion to your body size, you were less likely to become extinct.
The Extinction of Megafauna
The Late Quaternary is marked by a drastic global extinction event, mainly of large-bodied, land mammals. Causes proposed for these extinctions include overhunting by an increasing human population, particularly in areas such as the Americas and Oceania where modern humans had been largely absent previously. Earlier papers had proposed that species with traits that make them less prone to human hunting (arboreal, nocturnal, or forest dwelling) were more likely to survive.
However, the rapid decline and extinction of large, terrestrial animals is linked to the end of the last glacial period (25,000 to 12,000 years ago) which saw dramatic climate change. The research team hypothesised that the large mammals that survived the extinctions might have been endowed with larger brain sizes than those that perished. Larger brains might have helped these animals to adapt better and to cope with the wild fluctuations in climate.
To test this idea, the scientists assembled data on the brain size of 291 living mammal species plus 50 more that went extinct during the Late Quaternary.
The team found that models that used brain size in addition to body size predicted extinction status better than models that used only body size. It was concluded that possessing a large brain was an important, yet so far neglected and rarely studied characteristic of surviving megafauna species.
Implications for Large Mammals Living Today
One prominent feature shared by many extinct taxa was their large body size. In mammals, body size is correlated with several traits, including low population density, small population size, long lifespans, extended gestation periods along with prolonged inter-birth intervals and low fecundity.
Brain size is strongly correlated with body size as well and yet, mammals of similar size can have greatly different brain sizes.
In studies of modern birds and mammals, large brains have been found to improve survivability as these animals can modify their behaviour and adapt to rapidly changing environments and new threats such as an expanding human population.
When considering which animals around today might be under the most severe threat of extinction, brain-size should be considered when calculating the risk factors.
The paper published as an open access document in “Scientific Reports”
The scientific paper: “Small brains predisposed Late Quaternary mammals to extinction” by Jacob Dembitzer, Silvia Castiglione, Pasquale Raia and Shai Meiri published in Scientific Reports.
The new for 2022 PNSO Zhuchengtyrannus dinosaur model is due to be in stock at Everything Dinosaur in the next few days and team members have been busy completing the free fact sheet on this fearsome dinosaur that we send out with product purchases.
As part of our preparations, we have created a scale drawing for our free fact sheet. Zhuchengtyrannus might not be the best-known member of the Tyrannosauridae family but based on the fragmentary fossils ascribed to this genus it is the largest tyrannosaur described from Asia known to science.
PNSO Lu Xiong the Zhuchengtyrannus Dinosaur Model
The PNSO Lu Xiong the Zhuchengtyrannus dinosaur model is due to arrive along with several other new for 2022 PNSO figures in the next few days (expected early April 2022). As well as containing the PNSO Zhuchengtyrannus other new PNSO models in the shipment include Jennie the Centrosaurus and Anthony the Styracosaurus along with the 1:35 scale new Triceratops, Tsintaosaurus and Harvey the Iguanodon.
A spokesperson from Everything Dinosaur commented:
“PNSO have earned a formidable reputation over the last few years or so for the excellence of their prehistoric animal models and figures. More new models will be announced in the near future, for the time being we are just delighted to be getting these fantastic dinosaur figures into stock.”
Remarkably, one in four named animal species is a beetle. There are over 380,000 beetle species that have been scientifically described and perhaps several million more awaiting formal description. Members of the Order Coleoptera are distinguished from other insects as their front pair of wings are hardened into wing-cases (elytra) and they exploit a huge range of ecological niches and environments. However, their evolutionary origins remain uncertain and it is not known exactly when these six-legged animals became so numerous and specious.
Seventeen scientists including researchers from the University of Bristol have set about unravelling the evolutionary history of these amazing insects.
Mammoth Mathematical Models
A project to map the evolutionary history of arguably, the most successful and diverse animals of all time was a mammoth task. The researchers used a 68-gene character dataset that had been compiled previously which had sampled 129 out of the 193 recognised beetle families alive today and compared this to the beetle fossil record to provide a refined timescale of beetle evolution. A supercomputer at the University of Bristol’s Advanced Computing Research Centre slogged through the information for 18 months to produce the most comprehensive evolutionary tree of the Coleoptera ever created.
The mathematical models at the very heart of this research demonstrated that different beetle clades diversified independently, as various new ecological opportunities arose. There was no single, immense, all-encompassing divergence event.
One of the corresponding authors of the paper, published by Royal Society Open Science, Professor Chenyang Cai (University of Bristol) commented:
“There was not a single epoch of beetle radiation, their secret seems to lie in their remarkable flexibility. The refined timescale of beetle evolution will be an invaluable tool for investigating the evolutionary basis of the beetle’s success story”.
Carboniferous Origins but the Evolution of Flowering Plants had Little Impact
The oldest beetle fossils date back to around 295 million years ago (Early Permian), molecular clock studies indicate an origin in the Late Carboniferous. The analysis revealed that all the modern beetle suborders had originated by the Late Palaeozoic with a Triassic-Jurassic origin of most of the extant families.
It had been thought that as flowering plants became the dominant terrestrial plants in a period referred to as the Cretaceous Terrestrial Revolution (KTR), so beetles diversified to take advantage of new ecological niches as the angiosperms evolved. However, this study concludes that the major beetle clades were present before the KTR. Nevertheless, some scarabaeoid and cucujiform clades underwent diversification during the Late Jurassic to Early Cretaceous, partly overlapping with the diversification of major angiosperms clades in the Early to mid-Cretaceous.
However, the previously postulated strong link between flowering plant evolution and the rapid expansion of the beetle suborder is refuted by this research.
Advances in Technology and Genetics
Professor Cai explained that this research into the Coleoptera would not have been possible without advances in computer technology and genetics. He stated:
“Reconstructing what happened in the last 300 million years is key to understanding what gave us the immense diversity beetles are known for today”.
Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.
The scientific paper “Integrated phylogenomics and fossil data illuminate the evolution of beetles” by Chenyang Cai, Erik Tihelka, Mattia Giacomelli, John F. Lawrence, Adam Ślipiński, Robin Kundrata, Shûhei Yamamoto, Margaret K. Thayer, Alfred F. Newton, Richard A. B. Leschen, Matthew L. Gimmel, Liang Lü, Michael S. Engel, Patrice Bouchard, Diying Huang, Davide Pisani and Philip C. J. Donoghue published in Royal Society Open Science.
In late January, Everything Dinosaur announced plans to add short videos to the product pages of its award-winning website: Everything Dinosaur however, the lack of a suitable plug-in to facilitate videos without compromising the site speed has led to a suspension of the project.
Balancing the Needs of Customers
The intention had been to include product videos, highlighting prehistoric animal models to compliment the images found on Everything Dinosaur’s product pages. However, the three WordPress plug-ins tried either failed to work properly or compromised the website’s load speed.
A spokesperson from Everything Dinosaur commented:
“Our website is quite sophisticated and we require a plug-in to be able to play embedded videos from our YouTube channel without causing conflicts with other elements of our website and not slowing down the site. So far, despite our dedicated efforts we have not found the ideal partner.”
Everything Dinosaur’s website is optimised for fast loading on all devices including mobile phones. The site loading time is a key performance indicator for the company as fast loading websites provide an enhanced customer experience.
Continuing to Look
Whilst the project has been shelved, Everything Dinosaur will continue to look for suitable plug-ins for their website so that product showcase videos can be played. These videos will still be available on the company’s YouTube channel providing potential purchasers with more information on prehistoric animal models than can be conveyed using standard images alone.
The debate continues as to when the first dinosaurs evolved. Some of the oldest specimens described to date come from the famous Ischigualasto Formation located in north-western Argentina. These sediments are estimated to be around 232 million years old. It is thought that the first true dinosaurs evolved in the Southern Hemisphere and many palaeontologists favour a South American origin whilst others consider the evolutionary cradle of the Dinosauria was Africa: Dinosaurs Out of Africa?
To compound this debate, the fossil record of the ancestors of dinosaurs is particularly sparse. Some older Argentinian deposits have provided evidence of the precursors to the “true dinosaurs”, with some of these fossils estimated to be around 236 million years of age. However, scientists from the Universidade Federal de Santa Maria (Rio Grande do Sul, Brazil), have reported the discovery of a single fossilised thigh bone from Middle Triassic sediments in Brazil that predates all the Argentinian dinosauromorph fossils.
The Dinodontosaurus Assemblage Zone
The fossilised thigh bone (right femur) measures 11 cm in length and it comes from Middle Triassic sediments (Pinheiros-Chiniquá Sequence) from the famous Dinodontosaurus Assemblage Zone, so named because as well as archosaur fossils, the sediments have yielded an abundance of fossil material associated with the dicynodont Dinodontosaurus. The femur has a morphology similar to the thigh bones of other dinosauromorphs, but it comes from much older stratum, estimated to be at least 237 million years old (Ladinian faunal stage of the Middle Triassic).
This newly described specimen establishes that the Dinosauromorpha (dinosaurs and their close ancestors), were present in South America earlier than previously recorded and extends the fossil record of South American dinosauromorphs into the Ladinian stage of the Triassic.
The thigh bone might be small and no genus has been erected based on this single fossil, but it does represent the oldest dinosauromorph fossil found in South America to date.
An Ecosystem Dominated by Other Reptiles
Based on comparisons with more complete fossil specimens the femur came from an animal around a metre in length, most of which was accounted for by its long, thin tail if this dinosauromorph possessed a similar body plan. It lived in a diverse ecosystem dominated by other types of reptile. For example, the giant pseudosuchian Prestosuchus was probably the apex predator and at nearly 7 metres in length, this giant member of the crocodile-line of the Archosauria would have dwarfed all the dinosauromorphs in the ecosystem.
The scientific paper: “Oldest dinosauromorph from South America and the early radiation of dinosaur precursors in Gondwana” by Rodrigo T. Müller and Maurício S. Garcia published in Gondwana Research.
Scientists have identified the first confirmed dinosaur nesting site in Brazil. The fossilised eggs found suggest a colonial titanosaur nesting site and indicate individuals returning periodically to the same location to breed.
The fossils consisting of preserved clutches and isolated egg fragments were excavated from sandy deposits in an abandoned limestone quarry (Lafarge Quarry) at Ponte Alta District, Uberaba Municipality in Minas Gerais State (south-eastern Brazil). The fossils were recovered from the Serra da Galga Formation (Upper Cretaceous) and although no fossilised embryos were found at the site, the shape of the eggs strongly suggest that they were laid by titanosaurs.
Nesting in Colonies and Evidence of Breeding-site Fidelity
The Titanosauria were a highly successful clade of long-necked, long-tailed herbivores that were globally distributed during the Cretaceous and survived up until the very end of the Mesozoic. Some of the biggest terrestrial animals known to science are members of this clade, dinosaurs such as Patagotitan, Argentinosaurus and Notocolossus. All three of these titanosaurs lived millions of years before the Lafarge Quarry eggs were laid and they lived much further south (higher palaeolatitude).
Numerous titanosaur nesting sites are known (Spain, Romania, France, India and most notably Argentina), writing in the academic journal “Scientific Reports”, the researchers report the first titanosaur nesting site from the Late Cretaceous of Brazil (Maastrichtian faunal stage). The fossil material consisting of several egg-clutches, partially preserved, isolated eggs and many eggshell fragments were found in two distinct levels, approximately two metres apart. This discovery adds further support to the theory that these large herbivores nested in colonies and had preferred locations for their nesting sites, what is often referred to as breeding-site fidelity.
Isolated and fragmentary remains of titanosaur eggs had previously been reported from Brazil, but the Lafarge Quarry specimens provide unambiguous proof of titanosaur nesting in Brazil. As no embryos have been found in association with the fossilised eggs, it is not possible to comment on the specific genus involved. However, the researchers state that between the Santonian to the Maastrichtian faunal stages of the Late Cretaceous (86 to 66 million years ago) only derived titanosaurs such as saltasaurids and colossosaurians are recorded from South America. It is likely that the fossils associated with the nesting site represent an unknown genus.
During the Late Cretaceous the Ponte Alta District would have been located at around 26 degrees south of the Equator, putting it on a similar palaeolatitude of titanosaur nesting sites found in India. Previously, South American titanosaur nesting sites have been recorded between 33 to 47 degrees south of the Equator. This latitudinal difference could also influence the distribution of species on the Gondwana continent. The palaeoclimatic variation and geological characteristics could result in a difference in nesting time between titanosaurs living at different latitudes.
How Did Titanosaurs Build Nests?
The Lafarge Quarry site indicates colonial nesting which also suggests that these herbivorous dinosaurs moved around in herds. It is likely that Ponte Alta District titanosaurs scooped out pits in the soft sand using their back legs and then laid their eggs in clutches, before burying them and perhaps covering the nest with vegetation to help incubation.
To read an article about the naming of Austroposeidon magnificus the largest dinosaur from Brazil described to date: Brazil’s Biggest Dinosaur.
The scientific paper: “First titanosaur dinosaur nesting site from the Late Cretaceous of Brazil” by Lucas E. Fiorelli, Agustín G. Martinelli, João Ismael da Silva, E. Martín Hechenleitner, Marcus Vinícius Theodoro Soares, Julian C. G. Silva Junior, José Carlos da Silva, Élbia Messias Roteli Borges, Luiz Carlos Borges Ribeiro, André Marconato, Giorgio Basilici and Thiago da Silva Marinho published in Scientific Reports.
Spinosaurus (S. aegyptiacus) and its close relatives (spinosaurids) are an enigmatic group of theropod dinosaurs that have undergone a radical shift in their place in Early to early Late Cretaceous ecosystems as more evidence has emerged that these predators were adapted to a semi-aquatic lifestyle.
This week, in the journal “Nature”, a new study was published reinforcing the idea that these dinosaurs were perfectly at home in the water. An examination of spinosaurid bone density in comparison to the bone densities of extant animals which are adapted to an aquatic life, demonstrates that Spinosaurus and its close relative Baryonyx (B. walkeri) were capable of submerging themselves underwater to hunt.
Anatomical Adaptations for an Aquatic Life
Recent studies utilising fossil finds from North Africa had demonstrated that Spinosaurus aegyptiacus possessed a number of anatomical adaptations indicating an aquatic existence. It had long, narrow jaws lined with cone-shaped teeth, ideal for catching slippery fish. The nostrils were retracted and located further up the snout, Spinosaurus was a quadruped with short hind legs adapted for swimming and it is now known that it had a fin on its long tail, making it ideal as an organ for propulsion: Spinosaurus a River Monster!
When Baryonyx was first described after the discovery of its fossilised bones in a Surrey clay pit, scientists found evidence of fish scales and the remains of a small iguanodontid in the body cavity where the stomach would have been. This suggests that Baryonyx ate fish as well as other dinosaurs.
Dr Nizar Ibrahim
University of Portsmouth palaeontologist Dr Nizar Ibrahim has been at the forefront of research into spinosaurids, helping to change our perceptions about these super-sized predators. He has been a member of several field teams that have explored the Cretaceous deposits of North Africa helping to find more fossils of Spinosaurus aegyptiacus upon which these new revelations are based.
Dr Ibrahim is one of the co-authors of the bone density paper. The continuing debate about just how much time Spinosaurus spent in the water and whether it was an underwater pursuit predator or hunted fish like a giant heron led lead author Dr Matteo Fabbri, (Chicago Field Museum), senior author Dr Ibrahim and international colleagues to try to find another way to infer the lifestyle and ecology of Spinosaurus.
Dr Fabbri explained:
“The idea for our study was, okay, clearly we can interpret the fossil data in different ways. But what about the general physical laws? There are certain laws that are applicable to any organism on this planet. One of these laws regards density and the capability of submerging into water.”
Bone density can provide evidence to support a vertebrate’s aquatic behaviour. Animals that spend a lot of time underwater tend to have dense bones to help them remain submerged. If spinosaurids had similar bones, then this would provide further evidence in support of the idea that these dinosaurs hunted underwater.
Bone Densities of Living and Extinct Animals Compared
The research team assembled an exceptionally large dataset of femur and rib bone cross-sections from 250 species of extinct and living animals, including both land-dwellers and water-dwellers, and covering animals ranging in weight from a few grammes to several tonnes including seals, whales, elephants, mice, and even hummingbirds.
The scientists also collected data on extinct marine reptiles like mosasaurs and plesiosaurs. The researchers compared bone cross sections of these animals to cross-sections of bone from Spinosaurus and its close relatives Baryonyx and Suchomimus.
A clear link was identified between bone density and aquatic foraging behaviour. Animals that submerge themselves underwater to find food have bones that are almost completely solid throughout, whereas cross-sections of land-dwellers’ bones look more like doughnuts, with hollow centres.
When the researchers applied spinosaurid dinosaur bones to this paradigm, they found that Spinosaurus and Baryonyx both had the type of dense bone associated with full submersion.
Commenting on their research Dr Ibrahim stated:
“The scope of our study kept expanding because we kept thinking of more and more groups of vertebrates to include.”
A Different Environmental Niche for Suchomimus
The closely related Suchomimus (S. tenerensis), fossils of which are known from the Early Cretaceous of Niger, was discovered to have less dense bones than both Baryonyx and Spinosaurus. It lived by water and ate fish, as evidenced by its crocodile-like snout and conical teeth, but based on its bone density, it wasn’t actually swimming much. Perhaps this dinosaur was not a subaqueous forager but hunted for fish by wading into the water, rarely getting out of its depth.
Co-author of the study, Dr Jingmai O’Connor from the Field Museum in Chicago explained that collaborative studies like this one that draw from hundreds of specimens, are “the future of palaeontology”. These studies might be very time-consuming to complete, but they let scientists shed light onto big patterns within the fossil record.
Dr Ibrahim is already thinking about his next research project, he commented:
“I think that, with this additional line of evidence, speculative notions that envisage Spinosaurus as some sort of giant wader lack evidential support and can be safely excluded. The bones don’t lie, and now we know that even the internal architecture of the bones is entirely consistent with our interpretation of this animal as a giant predator hunting fish in vast rivers, using its paddle-like tail for propulsion. It will be interesting to reconstruct in a lot more detail how these river monsters moved around – something we are already working on.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Portsmouth in the compilation of this article.
The scientific paper: “Subaqueous foraging among carnivorous dinosaurs” by Matteo Fabbri, Guillermo Navalón, Roger B. J. Benson, Diego Pol, Jingmai O’Connor, Bhart-Anjan S. Bhullar, Gregory M. Erickson, Mark A. Norell, Andrew Orkney, Matthew C. Lamanna, Samir Zouhri, Justine Becker, Amanda Emke, Cristiano Dal Sasso, Gabriele Bindellini, Simone Maganuco, Marco Auditore and Nizar Ibrahim published in Nature.
There is still time to enter Everything Dinosaur’s competition to win a copy of the fantastic “Explorers of Deep Time” by the eminent American palaeontologist Roy Plotnick. This new book explains what it’s really like to be a palaeontologist. Roy takes readers behind the scenes to reveal the ups and downs, the trials and triumphs of pursuing a career in the Earth sciences. If you have ever thought about studying fossils for a living, then this book is for you!
There is still a week to go before the competition closes (midnight BST 31st March 2022).
Please note this competition is now closed!
“Explorers of Deep Time” Book Competition
All you have to do to enter the competition to win a free copy is visit Everything Dinosaur on Facebook “Like” our page, then leave a comment on the competition post naming the dinosaur whose skull fossil features on the front cover.
To Enter the Competition
To enter Everything Dinosaur’s competition to win a free copy of “Explorers of Deep Time”, all you have to do is:
“Like” our competition post and enter the competition.
Name the dinosaur whose skull is shown on the front cover of the book (a clue – it is the skull of an iconic horned dinosaur).
Not on Facebook? Not a Problem You can Still Enter the Competition
If you are not on Facebook, just leave a comment on this blog post to enter. Tell us the name of the horned dinosaur whose skull is shown on the bottom of the front cover of “Explorers of Deep Time” in the comments section of this blog post and we will automatically enter you into our free prize draw to win a copy.
Terms and Conditions of the “Explorers of Deep Time” Book Competition
Automated entries are not permitted and will be excluded from the draw.
Only one entry per person.
The prize is non-transferable and no cash alternative will be offered.
The Everything Dinosaur “Explorers of Deep Time” competition runs until midnight (BST) Thursday 31st of March 2022.
Winner will be notified by private message on Facebook or via the Everything Dinosaur Blog.
The extraterrestrial impact event that marked the end of the Mesozoic is estimated to have wiped out more than three-quarters of all the marine animal species, including most of the marine reptiles and devastated life on land resulting in the extinction of the non-avian dinosaurs and the Pterosauria. As terrible the impact was, it was made worse by the presence of vast amounts of sulphur within the rocks that bore the brunt of the impact. In the immediate aftermath the sulphur particles thrust high into the atmosphere caused acid rain, blocked sunlight and prolonged planetary-scale cooling exacerbating the extinction event.
It seems the dinosaurs were just very unlucky…
Scientists from the University of Bristol, St Andrews University, Syracuse University (New York), Texas A&M University (College Station, Texas) and Ellington Geological Services (Houston, Texas), have published a paper in the prestigious Proceedings of the National Academy of Sciences that explores the consequences of the extraterrestrial impact event.
They conclude that the expulsion of huge amounts of sulphur into the atmosphere contributed directly to the extinction of the dinosaurs.
The researchers found that sulphur gases circulated globally for years in the Earth’s atmosphere, cooling the climate and contributing to the mass extinction of life. This extinction event was catastrophic for the non-avian dinosaurs and other life, but also allowed for the diversification of mammals including primates, which ultimately led to the evolution of hominins such as our own species.
A Rapid and Catastrophic Change in the Global Geological Record
Commenting on the significance of the research, co-author of the paper Dr James Witts (School of Earth Sciences, University of Bristol) stated:
“Our data provides the first direct evidence for the massive amounts of sulphur released by the Chicxulub impact. It’s amazing to be able to see such rapid and catastrophic global change in the geological record.”
Sulphate aerosols have been implicated previously in the end-Cretaceous mass extinction event which marked the demise of the non-avian dinosaurs and the start of the “Age of Mammals”. The research team were able to examine the rare sulphur isotopes in material ejected by the impact and deposited in a nearby sea, now represented by rocks found along the Brazos River in Texas.
By examining the concentration of the sulphur deposits the team could assess the devastating consequences of the release of huge quantities of sulphur into the atmosphere some 66 million years ago.
Atmospheric sulphur in the stratosphere scattered incoming solar radiation and prolonged planetary-scale cooling for many years after the original impact, causing acid rain and reducing the light available for photosynthesis which further depleted terrestrial vegetation and marine plankton extending the time it would have taken for food chains to recover.
Corresponding author Christopher Junium (Syracuse University) added:
“The initial effects of the impact were caused by rock dust, soot and wildfires, but the sulphur aerosols extended the time period over which life would have suffered from extreme cooling, reduced sunlight and acidification of the land surface and oceans. And it was this extended duration of cooling that likely played a central role in the severity of the extinction.”
In 2017, Everything Dinosaur produced an article that looked at similar research published in Geophysical Research Letters that examined the impact that may have ejected 300 billion tonnes of sulphur into the planet’s atmosphere. This paper too, emphasised the devastation caused by sulphur aerosols and it examined the consequences of the event, which they estimated caused a temperature drop on land by as much as 17 degrees Celsius. The Japan-based researchers also calculated that had the catastrophe occurred elsewhere on the planet, the dinosaurs may not have become extinct and the resulting macroevolution of the mammals may not have occurred. Lucky for us, it did, to read our 2017 article: Chicxulub Impact – A Really Bad Place to Hit.
Lucky for us, the non-avian dinosaurs were very unlucky…
Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.
The scientific paper: “Massive perturbations to atmospheric sulfur in the aftermath of the Chicxulub impact” by Christopher K. Junium, Aubrey L. Zerkle, James D. Witts, Linda C. Ivany, Thomas E. Yancey, Chengjie Liu and Mark W. Claire published in The Proceedings of the National Academy of Sciences.
Most vertebrates have jaws, specialised anatomical features for capturing and processing food. A newly published study suggests that the earliest jaws to evolve were caught in a trade-off between maximising their strength and their bite speed.
The Evolution of Jaws in Vertebrates
Jawed vertebrates dominate modern ecosystems emphasising the importance of jaw development in the evolutionary history of the vertebrates. Over 99% of all living vertebrates have jaws and the very first jaws evolved in prehistoric fish over 400 million years ago. These jaws evolved from gill arches, anatomical structures in fish that support their gills.
How jaws developed has been well documented, for example, Everything Dinosaur has blogged about their evolution: Ancient Shark Provides Insight into Jaw Development, however, researchers led by scientists from the University of Bristol have explored this important topic using a mathematical model to examine the early evolution and radiation of jaw types.
The Development of a Novel Mathematical Model to Explore Jaw Development
Writing in the academic publication “Science Advances”, the researchers collected data on the shapes of fossil jaws and developed a mathematical model to assess their characteristics. The mathematical model produced permitted the scientists to extrapolate an extensive range of theoretical jaw shapes that could have been explored by the first evolving jaws. These theoretical jaws were tested for their strength – the amount of force they could endure without breaking, and their speed – how efficiently they could be opened and closed.
Jaw speed and jaw strength are two traits that conflict with each other. For example, really strong, powerful jaws like those associated with the giant placoderm Dunkleosteus would probably have been quite slow to open and close. Increasing bite force usually means a decrease in jaw speed.
By comparing the fossil record with the theoretical jaw shapes predicted by the mathematical model, the researchers deduced that jaw evolution has been constrained to shapes that have the highest possible speed in relation to their strength. Specifically, the jaws of early members of the Gnathostomata (jawed vertebrates) in the dataset were extremely optimal, and some groups evolved away from this optimum over time. These results suggest that the evolution of biting was very quick.
Bristol University PhD student William Deakin, the lead author of the paper explained:
“Jaws are an extremely important feature to gnathostomes – or jaw-mouths. They are not only extremely widespread, but almost all creatures that have them, use them in the same way – to grab food and process it. That’s more than can be said for an arm or a foot or a tail, which can be used for all sorts of things. This makes jaws extremely useful to anyone studying the evolution of function. Very different jaws from very different animals can be tested in similar ways. Here we have shown that studies on a large variety of jaws, using theoretical morphology and adaptive landscapes to capture their variety in function, can help shed some light on evolutionary questions.”
Co-author of the study Professor Philip Donoghue (University of Bristol), added:
“The earliest jawed vertebrates have jaws in all shapes and sizes, long thought to reflect adaptation to different functions. Our study shows that most of this variation was equally optimal for strength and speed, making for fearsome predators.”
Emily Rayfield, who like Professor Donoghue is also a Professor of Palaeobiology at Bristol University and co-author of the paper, praised the new, insightful mathematical model developed by William Deakin commenting:
“The new software that Will developed to analyse the evolution of jawed vertebrates, is unique. It allows us to map the design space of key anatomical innovations, like jaws, and determine their functional properties. We plan to use it to uncover many more of the secrets of evolutionary history.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.
The scientific paper: “Increasing morphological disparity and decreasing optimality for jaw speed and strength during the radiation of jawed vertebrates” by William J. Deakin, Philip S. L. Anderson, Wendy Den Boer, Thomas J. Smith, Jennifer J. Hill, Martin Rücklin, Philip C. J. Donoghue and Emily J. Rayfield published in Science Advances.