All about dinosaurs, fossils and prehistoric animals by Everything Dinosaur team members.
Articles, features and information which have slightly more scientific content with an emphasis on palaeontology, such as updates on academic papers, published papers etc.
Whilst on a short visit to the London Natural History Museum team members at Everything Dinosaur took the opportunity to visit the dinosaur gallery. Amongst the dinosaur bones and exhibits of fossil teeth, a trace fossil was spotted. It was a fossil dinosaur footprint, a specimen from the famous Lark Quarry site (Australia).
A fossil dinosaur footprint photographed at the London Natural History Museum. The exhibit features a three-toed print from the famous Lark Quarry track site in Australia. Picture credit: Everything Dinosaur.
Picture credit: Everything Dinosaur
A Fossil Dinosaur Footprint
The Lark Quarry site is regarded as one of the most remarkable non-avian trace fossils in the world. The site, near the town of Winton (Queensland, Australia) preserves the fossilised footprints of at least three different types of dinosaur. When first extensively studied, it was thought the tracks represented a large theropod disturbing smaller dinosaurs and causing a stampede.
It had been suggested that the big tridactyl prints were made by an ornithopod and not a carnivorous theropod.
Other scientists have suggested that the larger tracks were made by Australovenator. Australovenator (A. wintonensis) was named and described in 2009 (Hocknull et al). It has been classified as a member of the Megaraptoridae family. Australovenator may have been a sister taxon of Fukuiraptor, which is known from Japan.
The CollectA Australovenator replica.
The picture (above) shows a CollectA Australovenator model from the CollectA Age of Dinosaurs Popular range.
A spokesperson from Everything Dinosaur commented:
“The Lark Quarry site is extremely important for ichnologists. The site preserves around 3,300 dinosaur tracks. The tracks have been interpreted in several ways. For example, the largest tridactyl prints could represent an ornithopod, or perhaps they were made by a theropod like Australovenator.”
A new taxon of armoured dinosaur has been described from fossils found on the Isle of Wight. The new ankylosaurid has been named Vectipelta barretti (pronounced Vec-tea-pelt-tah bar-rett-ee). The genus name is derived from the Roman name for the Isle of Wight “Vectis” and “pelta” the Latin for shield. The species name honours Professor Paul Barrett of the London Natural History Museum. This is the first dinosaur named honouring Professor Barrett. The name recognises the on-going contribution Professor Barrett has made to vertebrate palaeontology and his support and mentoring of other scientists who also worked on this study.
An artist’s impression of a pair of Vectipelta armoured dinosaurs from the Wessex Formation of the Isle of Wight. Picture credit: Stu Pond.
Vectipelta barretti
Lead author of the paper, published in the Journal of Systematic Palaeontology, Stuart Pond (London Natural History Museum), commented:
“This is an important specimen because it sheds light on ankylosaur diversity within the Wessex Formation and Early Cretaceous England.”
The fossil material consists of a partial skeleton. Cervical, dorsal, sacral and caudal vertebrae have been recovered along with numerous osteoderms, limb elements and a well-preserved but fragmentary pelvic girdle. The first fossils were discovered in the early 1990s, following a landslip west of Chilton Chine (south-western coast of the Isle of Wight). Like many armoured dinosaur fossils associated with the Wessex Formation, the fossils were ascribed to Polacanthus foxii. However, the researchers were able to identify several unique traits in the bones that confirmed that this was a new species.
Vectipelta barretti IWCMS 2021.75 pelvis in dorsal view. Picture credit: Stuart Pond.
Not Closely Related to Polacanthus
A phylogenetic analysis demonstrated that Vectipelta was not closely related to Polacanthus. It is more closely related to the geologically younger Chinese ankylosaurids Zhejiangosaurus and Dongyangopelta. This suggests that during the Early Cretaceous there may have been extensive faunal interchange between continents. The picture of ankylosaurid distribution and dispersal may be much more complicated than previously suspected.
Vectipelta is estimated to have measured around four metres in length. It would have been relatively slow-moving with broad hips.
When asked to comment about the spiky, ponderous dinosaur named after him, Professor Barrett stated:
“I’m flattered and absolutely delighted to have been recognised in this way, not least as the first paper I ever wrote was also on an armoured dinosaur in the NHM collections. I’m sure that any physical resemblance is purely accidental.”
A closer view of the new armoured dinosaur from the Isle of Wight (V. barretti). Picture credit: Stu Pond.
More Wessex Formation Armoured Dinosaurs Awaiting Discovery
Although the Wessex Formation is notoriously difficult to date, Vectipelta fossil material is associated with the early Barremian. This armoured dinosaur could have roamed the Isle of Wight around 125 million years ago. The Polacanthus holotype material could be late Barremian in age. This suggests that Vectipelta barretti could be 6-8 million years older than Polacanthus foxii. The other ankylosaurid associated with the Wealden Group is Hylaeosaurus armatus. Hylaeosaurus fossils are associated with even older strata (Valanginian faunal stage). There could be as much as three million years separating Hylaeosaurus from Vectipelta.
The researchers conclude that there were probably lots of different armoured dinosaurs roaming southern England during the Early Cretaceous.
Vectipelta life reconstruction. Picture credit: Stuart Pond.
Historically, the assignment of fragmentary ankylosaurid remains to Polacanthus was probably incorrect. There are likely to be several other armoured dinosaurs awaiting discovery in the rocks of southern England and the Isle of Wight. Recent fossil discoveries have led to the revision of the hadrosauriforms and iguanodontids associated with the Wealden Supergroup. It is likely that the Thyreophora will also have to be revised and more taxa erected.
A single Vectipelta armoured dinosaur. Picture credit: Stu Pond.
Everything Dinosaur acknowledges the assistance of a media release from the London Natural History Museum in the compilation of this article.
The scientific paper: “Vectipelta barretti, a new ankylosaurian dinosaur from the Lower Cretaceous Wessex Formation of the Isle of Wight, UK” by Stuart Pond, Sarah-Jane Strachan, Thomas J. Raven, Martin I. Simpson, Kirsty Morgan and Susannah C. R. Maidment published in the Journal of Systematic Palaeontology.
The fossils representing the first, non-avian dinosaur with feather-like structures found in South America has been returned to Brazil. The Ubirajara fossil specimen has been repatriated from Germany. This prized but controversial fossil, was named and described in 2020 (Ubirajara jubatus).
Since the scientific publication, campaigners, including many prominent Brazilian scientists, had requested that this dinosaur be returned home. One of the leading advocates for the repatriation was Professor Aline Ghilardi of the Federal University of Rio Grande do Norte (UFRN).
Professor Aline Ghilardi, right, next to Professor Juan Cisnero (UFPI) and the minister of MCTI, Luciana Santos (centre). The Ubirajara fossil specimen is returned to Brazil. Picture credit: Luara Baggi – Ascom/MCTI.
The excitement in Brazil sparked by the scientific publication turned to dismay when it was realised that the fossil had been removed from the country. The materials and methods section of the paper stated that the specimen had been taken out of Brazil in 1995.
The first Brazilian law dealing with the protection of fossils was created in 1942. The legislation permitted fossils to leave the country, but authorisation was required. Subsequently, the law was strengthened, and it outlined how fossils should be collected, exported and insisted that Brazilian scientists should be involved in the study of such artifacts.
Ubirajara jubatus life reconstruction by the very talented palaeoartist Bob Nicholls.
Following a campaign, the paper describing U. jubatus, the first non-avian dinosaur to be found in the Southern Hemisphere with feather-like filaments was withdrawn.
After the allegations of illegal smuggling, it was agreed to return the specimen to Brazil. The scientific name Ubirajara jubatus was removed from the International Commission on Zoological Nomenclature (ICZN) registry. The dinosaur’s name currently is regarded as invalid. Whether the scientific name for this little theropod is to be retained has yet to be decided.
UbirajaraBelongstoBR
The repatriation was assisted by a highly successful social media campaign using the hashtag UbirajaraBelongstoBR.
An investigation was launched in Germany. This culminated in the recognition of the misconduct and unethical behaviour of the researchers involved. With that, finally, it was decided to return the dinosaur home in July 2022.
The controversy surrounding Ubirajara highlights a growing trend within palaeontology for assessing the impact of colonialism and the removal of fossil material from countries to America and Europe.
Professor Aline explained:
“Colonialist attitudes influence our science and make it a worse science and the results biased.”
Taking photographs of the Ubirajara fossil (counter slab). Picture credit: Juan Cisneros.
The Return of the Ubirajara Fossil Specimen
The social media campaign played a significant role in the successful repatriation. The return of the Ubirajara fossil specimen was achieved through a collaboration with the public, governments and palaeontologists.
A spokesperson commented that this campaign highlights how the public wants to engage and participate with scientific debate. The return of Ubirajara will hopefully inspire other scientists to engage in such campaigns, helping to improve palaeontology by making it more inclusive, fair and ethical.
Everything Dinosaur acknowledges the assistance of a media release from the Federal University of Rio Grande do Norte in the compilation of this article.
The first tetrapods (land living animals) were amphibious. It had been thought that the development of an egg with a semi-permeable shell (amniote egg) was a fundamental step in the development of life on land. This adaptation meant that land animals did not have to return to water to breed and spawn. Freed from having to return to the water, early tetrapods could explore new environments and expand into new habitats.
However, a new paper written by researchers from Nanjing University (China) and the University of Bristol challenges this view of evolution.
The researchers conclude that the earliest reptiles, birds and mammals (Amniota), may have borne live young.
What is an Amniote?
Amniotes lay eggs that have a semi-permeable shell that protects the embryo from drying out. A tough, internal membrane called the amnion surrounds the growing embryo as well as the yolk, the food source. Development of the embryo in a shelled egg meant that for the first time in history, the tetrapods were no longer tied to water to breed. We as mammals are amniotes, along with the birds and reptiles.
The amniotic egg, showing the semipermeable shell and the extraembryonic membranes. Picture credit: M. J. Benton (University of Bristol).
Studying Extinct and Extant Species
However, a study of 51 fossil species and 29 living species which could be categorised as oviparous (laying hard or soft-shelled eggs) or viviparous (giving birth to live young) suggests that the earliest reptiles, mammals and birds probably were capable of bearing live young.
The findings, published today in the academic journal “Nature Ecology & Evolution”, show that all the great evolutionary branches of the Amniota, the Mammalia, Lepidosauria (lizards and relatives), and the Archosauria (dinosaurs, crocodilians, birds) reveal viviparity and extended embryo retention in their ancestors.
Extended embryo retention (EER) occurs when the young are retained by the mother for a varying amount of time, likely depending on when conditions are best for survival. While the hard-shelled egg (amniote egg), has often been seen as one of the greatest innovations in evolution, this research implies it was extended embryo retention that gave this particular group of animals the ultimate protection.
Professor Michael Benton (School of Earth Sciences at the University of Bristol) explained:
“Before the amniotes, the first tetrapods to evolve limbs from fishy fins were broadly amphibious in habits. They had to live in or near water to feed and breed, as in modern amphibians such as frogs and salamanders.”
Professor Benton added:
“When the amniotes came on the scene 320 million years ago, they were able to break away from the water by evolving waterproof skin and other ways to control water loss. But the amniotic egg was the key. It was said to be a “private pond” in which the developing reptile was protected from drying out in the warm climates and enabled the Amniota to move away from the waterside and dominate terrestrial ecosystems.”
Challenging the Standard View About Amniote Egg Evolution
Project leader and corresponding author Professor Baoyu Jiang (Nanjing University) stated:
“This standard view has been challenged. Biologists had noticed many lizards and snakes display flexible reproductive strategy across oviparity and viviparity. Sometimes, closely related species show both behaviours, and it turns out that live-bearing lizards can flip back to laying eggs much more easily than had been assumed.”
Phylogeny of amniotes, showing known reproduction mode and eggshell mineralization, and EER of 80 modern and extinct species, and the estimated ancestral states for all branching points. The dominant inferred state at the origin of amniotes is viviparity with extended embryo retention (EER). Picture credit: M.J. Benton, University of Bristol.
Many Marine Reptiles were Live-bearers
Co-author Dr Armin Elsler (University of Bristol) commented:
“Also, when we look at fossils, we find that many of them were live-bearers, including the Mesozoic marine reptiles like ichthyosaurs and plesiosaurs. Other fossils, including a choristodere from the Cretaceous of China, described here, show the to-and-fro between oviparity and viviparity happened in other groups, not just in lizards.”
The picture (above) shows the CollectA Age of Dinosaurs Popular Temnodontosaurus model. The ichthyosaur is giving birth, demonstrating viviparity within the Ichthyosauria.
In many types of extant vertebrate extended embryo retention (EER) is quite common. The developing young are retained by the mother for a lesser or greater span of time. The mother delays giving birth until conditions are most favourable to permit the survival of her offspring. The mother deliberately gives birth at the most propitious time.
Co-author of the paper, Dr Joseph Keating commented:
“EER is common and variable in lizards and snakes today. Their young can be released, either inside an egg or as little wrigglers, at different developmental stages, and there appears to be ecological advantages of EER, perhaps allowing the mothers to release their young when temperatures are warm enough and food supplies are rich.”
Skeleton of a baby choristodere, Ikechuosaurus, from the Early Cretaceous of China, found curled up inside the remnants of a parchment-shelled egg. Picture credit: Baoyu Jiang (Nanjing University).
Profound Implications for our Understanding of Tetrapod Evolution
Professor Benton summarised the study:
“Our work, and that of many others in recent years, has consigned the classic ‘reptile egg’ model of the textbooks to the wastebasket. The first amniotes had evolved extended embryo retention rather than a hard-shelled egg to protect the developing embryo for a lesser or greater amount of time inside the mother, so birth could be delayed until environments become favourable.”
The professor implied that this study had profound implications for our understanding of tetrapod evolution. He added:
“Whether the first amniote babies were born in parchment eggs or as live, snapping little insect-eaters is unknown, but this adaptive parental protection gave them the advantage over spawning earlier tetrapods.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.
The scientific paper: “Extended embryo retention and viviparity in the first amniotes” by Baoyu Jiang, Yiming He, Armin Elsler, Shengyu Wang, Joseph N. Keating, Junyi Song, Stuart L. Kearns and Michael J. Benton published in Nature Ecology and Evolution.
Researchers from the University of Southampton studying a partial spinosaurid tooth have concluded that several different spinosaurs inhabited southern England during the Early Cretaceous. The tooth consisting of a crown with a partial root is reputed to have come from East Sussex, most probably from Lower Cretaceous (Valanginian) exposures of the Hastings Group (part of the Wealden Supergroup). If this is the case, then this tooth is amongst the oldest spinosaurid fossils known from the UK.
The spinosaurid tooth (specimen number HASMG G369a) shown in lingual view (left) and mesial view (right). Picture credit: University of Southampton.
Sorting the Stratigraphy
In common with many other isolated teeth found in strata associated with the Wealden Supergroup, it had been suggested that this tooth represented Baryonyx (B. walkeri). However, The Hastings Group underlies the Weald Clay Group from where the famous Baryonyx walkeri fossil material (NHMUK PV R9951) originates. Therefore, this fossil tooth is much older than the Baryonyx holotype material.
The fossil tooth could be around 138 million years old, much older than Baryonyx walkeri and therefore probably a different spinosaurid genus.
The Southampton University EvoPalaeoLab team carried out a series of tests on the isolated tooth. A statistical analysis confirmed that whilst the tooth was spinosaurid, it did not match any already described spinosaur species.
Project supervisor and co-author of the paper Dr Neil Gostling (University of Southampton explained:
“While we can’t formally identify a new species from one tooth, we can say this spinosaur tooth doesn’t match any of the existing species we know about. Given how many individual teeth exist in collections, this could be just the tip of the iceberg and it’s quite possible that Britain may have once teemed with a diverse range of these semi-aquatic, fish-eating dinosaurs.”
Many Different Spinosaurs
The Wealden Supergroup is famous for its dinosaur fossils. Baryonyx was discovered in a Surrey clay pit in 1983. Since then, isolated teeth from spinosaurids have tended to be assigned to this genus. Spinosaurids are a highly derived group of theropods. They evolved into piscivores and specialised in hunting and eating fish. Their jaws became elongated and crocodile-like and spinosaurids may have had their evolutionary origins in Europe.
The CollectA new for 2020 Prehistoric Life Baryonyx dinosaur model. Picture credit: Everything Dinosaur.
Picture credit: Everything Dinosaur
The model (above) is a CollectA Prehistoric Life Baryonyx figure.
Palaeontologists had suspected that there were several spinosaurid taxa represented by the Wealden Supergroup material. Spinosaurid teeth are known from formations that span much of the circa 25-million-year depositional history of the Wealden Supergroup, and recent works suggest that British spinosaurids were more taxonomically diverse than previously thought.
“We used a variety of techniques to identify this specimen, in order to test whether isolated spinosaur teeth could be referred to Baryonyx. The tooth did not group with Baryonyx in any of our data runs. It must belong to a different type of spinosaur.”
Distinct and Distantly Related Spinosaurids Lived in Southern England
The results demonstrate that distinct and distantly related spinosaur types lived in the region during the Early Cretaceous. This backs up research by the EvoPalaeoLab team, who argued in previous studies that the spinosaurs of southern England are more diverse than previously thought.
Illustration of White Rock spinosaurid. Picture credit: University of Southampton/Anthony Hutchings.
The Importance of Museum Collections
The study was able to take place as the researchers had access to a wealth of data as well as the fossil specimens themselves. It demonstrates the importance of maintaining access to fossil material for research purposes.
Dr Gostling explained:
“What this work highlights is the importance of keeping collections alive, and developing our understanding of them. Curators are essential to help us navigate the cupboards and displays, helping us to unpick the often-incomplete records – either never fully recorded, or lost to time. The diversity of palaeoenvironments is not always hidden in rocks, it is often waiting in a museum, its importance waiting to be rediscovered!”
Co-author Darren Naish added:
“Dinosaur teeth preserve numerous anatomical details, and we can use various analytical techniques to see how similar, or different, they are to other teeth. Our new study shows that previously unrecognised spinosaur species exist in poorly known sections of the Wealden’s history, and we hope that better remains will be discovered that improves our knowledge. Here’s another reminder that even well-studied places like southern England have the potential to yield new dinosaur species.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Southampton in the compilation of this article.
The scientific paper: “Isolated tooth reveals hidden spinosaurid dinosaur diversity in the British Wealden Supergroup (Lower Cretaceous)” by Chris T. Barker, Darren Naish and Neil J. Gostling published in PeerJ.
A new study examining diapsid fossil teeth from Lower Triassic sediments in South Africa has provided further evidence of the recovery of terrestrial ecosystems after the end-Permian mass extinction event. The research highlights the growing diversity of archosauromorphs following the extinction of parareptiles and therapsids.
Diapsid fossil teeth study sees rise of the Archosauromorpha in southern Africa. Temnospondyls (grey), archosauromorphs (monochrome), early mammals (yellow) and extinct therapsids (red). Picture credit: Everything Dinosaur.
The research team collected teeth from the Driefontein locality in Free State Province, South Africa. The strata represent Lower Triassic deposits (late Olenekian stage). The rocks are part of the Burgersdorp Formation and form part of the Karoo Basin, which provides an extensive geological record, crucially deposition that occurred before and after the end-Permian extinction event.
A total of 102 teeth were collected. The scientists identified 81 diapsid teeth with the remaining teeth classified as coming from temnospondyls. Analysis of the tooth morphology demonstrated that there was a greater diversity of archosauromorphs and other diapsids.
This research suggests that diapsids, especially archosauromorphs benefitted from the mass extinction event. They played an important role in the recovery of terrestrial ecosystems. Archosauromorphs filled many of the niches left vacant after the extinction of therapsids and anapsid reptiles.
The prehistoric life of South Africa. The image shows the diverse flora and fauna that had evolved in South Africa by the Early Jurassic (Hettangian faunal stage). Archosaurs dominated terrestrial ecosystems but shared these habitats with other diapsids and early mammals. Picture credit: The Evolutionary Studies Institute (The University of Witwatersrand).
The fossil teeth from Driefontein provide palaeontologists with an important window into how terrestrial ecosystems recovered. The largest mass extinction recorded in the Phanerozoic occurred approximately 252 million years ago. The end-Permian mass extinction event devastated both marine and terrestrial ecosystems. The Karoo Basin may yield further evidence to help palaeontologists to better understand how life bounced back from the mass extinction event. It may also help scientists to understand how the Archosauromorpha were able to gain an evolutionary advantage over other tetrapods. This may have ultimately helped the Dinosauria and their close relatives to dominate terrestrial habitats.
The scientific paper: “A diverse diapsid tooth assemblage from the Early Triassic (Driefontein locality, South Africa) records the recovery of diapsids following the end-Permian mass extinction” by Devin K. Hoffman, John P. Hancox and Sterling J. Nesbitt published in Plos One.
The discovery of a fossil sturgeon scute demonstrates that these “royal fish” were present in North Africa during the Late Cretaceous. The single, fossil scute is the first ever sturgeon fossil to have been found in Africa. The scute is a bony plate embedded into the sturgeon’s skin. Scutes provided a form of dermal armour that evolved to help protect these very ancient fish.
A digital photo of the sturgeon scute (also called buckler) specimen. Picture credit: University of Portsmouth.
A Significant Fossil Discovery
The sturgeon (there are more than two dozen extant species), belongs to the Acipenseriformes Order, which probably originated in the Late Triassic. Sturgeon fossils which are very similar to extant species, are known from Upper Cretaceous strata. Historically, they are associated with cooler waters of the Northern Hemisphere. The specimen was discovered by Professor David Martill (University of Portsmouth). It proves that these magnificent fish were present in Africa.
Sturgeons were more widespread in the Cretaceous than previously thought.
An extant European sturgeon. Picture credit: University of Portsmouth.
Professor Martill was exploring a well-known Moroccan fossil site during a field trip last November. He spotted a row of bony plates (bucklers) on a piece of rock and instinctively recognised the fossils represented the scutes from a sturgeon.
Discussing this significant fossil find, the Professor commented:
“It was a surprising discovery because all sturgeon species have been exclusively found in the Northern Hemisphere in the past. They’ve been located in North America, Europe, Russian Asia, Chinese Asia, but never in South America, Australia, Africa or India, which are the land masses that made up Gondwana, a supercontinent that existed around 336 million years ago and began breaking up around 150 million years ago.”
A drawing showing an extant sturgeon in lateral view. The different scutes are highlighted. Picture credit: University of Portsmouth.
A “Royal Fish”
The sturgeon has long been prized for its meat and for its roe (eggs). The roe is commonly referred to as caviar. King Edward II of England declared that all sturgeon from the waters of Wales and England belong to the monarch. This declaration was made in the early 14th century. Since then, these fish have been regarded as “royal fish”.
Sadly, due to overfishing and pollution, many species of extant sturgeon are close to extinction.
Commenting on his African fossil discovery Professor Martill stated:
“Russian beluga caviar is one of the most expensive in the world. Little did we know that at one time an extremely rare African sturgeon could have been a source of this delicacy!”
A digital photo of the dorsal surface of the fossil. Note the scale bar of 20 mm. Picture credit: University of Portsmouth.
Fossil Sturgeon Scute
Sturgeon are thought of as being “living fossils”, for they seem to have remained relatively unchanged since the time of Tyrannosaurus rex and Triceratops. Records from the 18th and 19th centuries indicate specimens reaching more than seven metres in length and weighing over 1.5 tonnes, but fish of this size are exceedingly rare today.
Professor Martill added:
“The very first sturgeons appear in the fossil record in the Late Triassic period in China. But the oldest true sturgeon ever discovered is probably a specimen in the Steve Etches collection from Dorset’s Jurassic Coast in England, which is mentioned in a book Steve and I wrote about fossils in the Kimmeridge Clay Formation.”
The discovery of a sturgeon fossil in Morocco complicates models of the geographical distribution of these fish during the Late Cretaceous.
A map of the continents at the end of the Cretaceous (66 million years ago). Sturgeon fossil localities are marked by solid black circles. Picture credit: University of Portsmouth
The fossil specimen is now in the collection of the University King Hassan II, Casablanca.
Everything Dinosaur acknowledges the assistance of a media release from the University of Portsmouth in the compilation of this article.
The scientific paper: “A sturgeon (Actinopterygii, Acipenseriformes) from the Upper Cretaceous of Africa” by David M. Martill published in Cretaceous Research.
Whilst the Dinosauria dominated terrestrial environments during the Mesozoic the seas and oceans of the world were home to a diverse assemblage of marine reptiles. Many different types of marine reptile evolved, and the diverse swimming techniques employed by these ancient animals have been revealed in a recently published scientific paper.
The swimming secrets of Mesozoic marine reptiles have been decoded thanks to a research team from the University of Bristol.
A replica of the ichthyosaur Eurhinosaurus (PNSO). During the Mesozoic, many different types of marine reptile evolved. Scientists from the University of Bristol have unlocked the swimming secrets of ancient marine reptiles.
The image (above) shows a replica of an Eurhinosaurus. An ichthyosaur (Leptonectidae family) that lived during the Early Jurassic (approximately 180 million years ago).
During the Mesozoic, which lasted from approximately 252 million years ago to the end-Cretaceous mass extinction event around 66 million years ago, many different types of marine reptile evolved. There were placodonts, turtles, the first ichthyosaurs and nothosaurs during the Triassic and these were replaced by marine crocodiles, derived ichthyosaurs, long-necked plesiosaurs and pliosaurs. During the Cretaceous the mosasaurs evolved.
In the new paper, published in the academic journal “Palaeontology”, the research team report on the use of cutting-edge statistical methods used to undertake a substantial quantitative study. This research, the first of its kind, provides a fresh perspective on the locomotion of Mesozoic marine reptiles.
Examining 125 Skeletons
In total, 125 marine reptile skeletons were studied. The research team mapped the changes in swimming styles within the different lineages over time. There was no explosive radiation at the beginning of the Triassic, but a gradual diversification of swimming styles. This diversity peaked during the Cretaceous.
Marine reptiles from the Mesozoic Era evolved a great diversity of body forms and sizes. Changes in their body and limb anatomy throughout evolution are associated with swimming adaptations. The variety of locomotory modes in Mesozoic marine reptiles is illustrated by (bottom-to-top) an early mosasauroid, a placodont, a plesiosaur and a fish-shaped ichthyosaur. Picture credit: Dr Susana Gutarra.
Dr Susana Gutarra (School of Earth Sciences at the University of Bristol), lead author of the paper commented:
“Changes in anatomy in land-to-sea transitions are intimately linked to the evolution of swimming. For example, sea lions’ flippers have relatively short forearm and large hands, very different from the walking legs of their ancestors. The rich fossil record of Mesozoic marine reptiles provided great opportunity to study these transitions at a large scale.”
The End-Permian Mass Extinction Event
At the end of the Permian, the Earth experienced a catastrophic mass extinction event. Life on Earth was devastated. It has been estimated that 50% of all marine families and over 80% of all marine genera died out (Raup and Sepkoski).
Remarkably, marine environments recovered relatively quickly. Various groups of reptiles became aquatic hunters.
To read an article from 2010 that documents a remarkable fossil site in China that provides evidence of how marine food webs recovered from the end-Permian mass extinction event: Ancient Ecosystem Revealed.
To test the validity of the statistical analysis, measurements from extant aquatic animals were included in the study.
Co-author Beatrice Heighton (University of Bristol), explained:
“We included measurements from living aquatic animals, such as otters, seals and turtles, of which we know their swimming behaviour. This is very important to provide a functional reference for the ancient species, with unknown swimming modes.”
Palaeobiologist Dr Susana Gutarra taking measurements from a very complete specimen of Liopleurodon, a pliosaur from the Middle-Late Jurassic of Germany (Museum of Palaeontology in Tübingen). Picture credit: Dr Susana Gutarra.
A Gradual Diversity of Swimming Styles
Co-author Dr Tom Stubbs (University of Bristol) added:
After this devastating event, there was a gradual diversification of locomotory modes, which contrasts with the rapid radiation described previously for feeding strategies. This is fascinating because it suggests a ‘head-first’ pattern of evolution in certain lineages.”
The scientific paper sheds light into the swimming styles of specific groups of marine reptile.
Dr Ben Moon (University of Bristol) explained the significance of this study, stating:
“Ichthyosaurs were highly specialised for aquatic locomotion from very early in their evolution. This includes their close relatives, the hupehsuchians, which had a morphology unlike any other known aquatic tetrapod. Further, we see overlap between mosasaurs and ichthyosaurs, which is indicative that mosasaurs evolved a swimming mode by oscillating flukes, different from the eel-like body undulation suggested in the past.”
An almost 8m-long specimen of Temnodontosaurus, an ichthyosaur from the Early Jurassic of Germany (State Museum of Natural History of Stuttgart, Germany), is one of the fossils included in this study. Picture credit: Dr Susana Gutarra.
Dr Moon of Bristol University’s School of Earth Science went onto add:
“In contrast, we don’t find evidence of convergence between ichthyosaurs and metriorhynchids (the highly aquatic crocodyliform thalattosuchians). This group retained quite primitive-looking hindlimbs, which seems incompatible with swimming by fluke oscillation.”
Examining the Evolution of Size
This comprehensive study also examined the evolution of size, a feature related to locomotion, animal physiology and ocean productivity.
The University of Bristol’s Professor Mike Benton, a co-author of the research paper commented:
“We know that transition to life in water is usually accompanied by an increase in body mass, as seen in cetaceans, and one of our previous studies shows that large sizes benefit aquatic animals in reducing the mass-specific costs of drag. Thus, it was essential to explore this trait in the wider ensemble of Mesozoic marine reptiles.”
Dr Gutarra explained that body mass follows a similar trend to the diversification of locomotory modes. The widest spread of body size also occurred in the Cretaceous. This confirms a strong correlation between the evolution of diverse swimming styles and changes in body mass.
Dr Gutarra added:
“The rate of increase and the maximum limits to body size seems to vary a lot between groups. This is a fascinating observation. We need to explore further what factors influence and limit the increase in body mass in each group.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.
The scientific paper: “The locomotor ecomorphology of Mesozoic marine reptiles” by Susana Gutarra, Thomas L. Stubbs, Benjamin C. Moon, Beatrice H. Heighton and Michael J. Benton published in Palaeontology.
A virtually complete titanosaur skull has been found in Queensland. The fossil discovery is Australia’s most complete sauropod skull found to date. It supports the hypothesis that Australian sauropods originated in South America. The titanosaur skull has been assigned to Diamantinasaurus matildae.
A view of the Diamantinasaurus skull bones in approximate life position: Picture credit: Australian Age of Dinosaurs.
Diamantinasaurus matildae
Australian Age of Dinosaurs Museum researchers in collaboration with Curtin University (Perth) despatched a media release announcing the discovery of the stunning sauropod skull. The fossil specimen, nicknamed “Ann” was excavated in 2018 at a dig site located at Elderslie Station, near Winton (Queensland).
Field team members working at the “Ann” dig site. Picture credit: Australian Age of Dinosaurs.
The fossil specimen is believed to be between 98-95 million years old (Cenomanian faunal stage of the Late Cretaceous). It is the fourth specimen of Diamantinasaurus matildae to have been discovered by Australian Age of Dinosaurs Museum staff.
Studying the Skull
Research on the titanosaur skull was led by Museum Research Associate Dr Stephen Poropat, a Postdoctoral Research Fellow at Curtin University.
Dr Poropat stated:
“This skull gives us a rare glimpse into the anatomy of this enormous sauropod that lived in northeast Australia almost 100 million years ago.”
Dr Stephen Poropat (left) and right, Dr Phil Mannion (University College London) examining the “Ann” site fossil material including the Diamantinasaurus skull bones, the Oliver scapula and vertebra two. Picture credit: Australian Age of Dinosaurs.
Implications for Titanosaur Evolution
The researchers identified similarities between “Ann” and the skull of another titanosaur Sarmientosaurus musacchioi. S. musacchioi fossils come from southern Argentina, from rocks which are roughly contemporaneous with the Winton Formation strata. The braincases of these two titanosaurs were similar, along with the dentition (teeth). Similar anatomical characteristics were also identified in the quadratojugal (a bone from the back of the skull near the posterior of the lower jaw).
Dr Poropat commented that their findings support previous theories that sauropods were using Antarctica as a migratory pathway between South America and Australia between 100 and 95 million years ago.
The doctor added:
“Our research suggests that Diamantinasaurus was one of the most ‘primitive’ titanosaurs. Gaining a better understanding of this species might explain why titanosaurs were so successful, across so much of the world, right until the end of the Age of Dinosaurs.”
A life reconstruction of the titanosaur Diamantinasaurus. Picture credit: Australian Age of Dinosaurs.
Titanosaur Skull Links Australian Dinosaurs to Antarctica and South America
At the beginning of the Late Cretaceous (100 to 95 million years ago), the Earth was much warmer than it is today. Antarctica which was located approximately where it is today, was ice free. Australia was much further south and closely associated with the Antarctic landmass. The huge conifer forests of Antarctica might have been an attractive habitat for migratory sauropods. The similarities between “Ann” and Sarmientosaurus skull matieral lends weight to the theory that titanosaurs used Antarctica as a pathway to Australia.
The Diamantinasaurus skull fossils are currently on display at the Australian Age of Dinosaurs Museum.
Everything Dinosaur acknowledges the assistance of a media release from the Australian Age of Dinosaurs Museum in the compilation of this article.
The scientific paper: “A nearly complete skull of the sauropod dinosaur Diamantinasaurus matildae from the Upper Cretaceous Winton Formation of Australia and implications for the early evolution of titanosaurs” by Stephen F. Poropat, Philip D. Mannion, Samantha L. Rigby, Ruairidh J. Duncan, Adele H. Pentland, Joseph J. Bevitt, Trish Sloan and David A. Elliott published by Royal Society Open Science.
A new study suggests that the key to the evolutionary success of the early mammals, was to stay small, eat insects and to reduce the number of bones in their skull. The reduction of mammalian skull bones led to a more efficient absorption of bite forces and this adaptation helped mammals to diversify and to ultimately dominate modern ecosystems.
The study, published in the academic journal “Communications Biology” contrasts the skulls of other vertebrates and mammalian ancestors with mammals known from the Jurassic and Cretaceous. In many vertebrate groups such as reptiles and fishes, the skull and lower jaw are composed of numerous bones. This configuration was also seen in the earliest ancestors of modern mammals that lived over 300 million years ago (Cynodontia). However, during evolution the number of bones in the skull was reduced.
Digital skull model of the small-sized Jurassic mammal ancestor Hadrocodium wui with coin providing scale. Picture credit: Dr Stephan Lautenschlager, University of Birmingham.
A Reduction in Mammalian Skull Bones
Computer simulations based on three-dimensional skull models permitted the research team to examine bite forces and skull stresses. Their research demonstrates that reducing the number of skull bones did not lead to higher bite forces or increased skull strength as postulated previously.
Instead, the researchers, found that the skull shape of these early mammals redirected stresses during feeding in a more efficient way.
Lead author for the study, Dr Stephan Lautenschlager, Senior Lecturer for Palaeobiology (University of Birmingham) explained:
“Reducing the number of bones led to a redistribution of stresses in the skull of early mammals. Stress was redirected from the part of the skull housing the brain to the margins of the skull during feeding, which may have allowed for an increase in brain size.”
Switching Diets
The study, which also involved scientists from the University of Hull, Bristol University, the University of Chicago and the London Natural History Museum, demonstrated that alongside the reduction of skull bones, early mammals also became a lot smaller. Some Mammaliaformes for example, had skulls around 1 cm in length.
This miniaturisation considerably restricted the available food sources and early mammals adapted to feeding mostly on insects.
Dr Lautenschlager added:
“Changes to skull structure combined with mammals becoming smaller are linked with a dietary switch to consuming insects – allowing the subsequent diversification of mammals which led to development of the wide-range of creatures that we see around us today.”
Life reconstruction of Hadrocodium wui. This Jurassic mammal is depicted hunting insects, illustrating how the adoption of an insectivorous diet and miniaturisation played a significant role in mammal evolution. Picture credit: Dr Stephan Lautenschlager, University of Birmingham.
Hadrocodium wui
One of the mammaliaforms used in the study, is Hadrocodium wui fossils of which are known from the Early Jurassic (Sinemurian faunal stage) of China. At around ten centimetres long, this tiny animal was a very small and inconsequential member of the Lufeng Formation biota, which was dominated by dinosaurs such as Lufengosaurus.
An illustration of Lufengosaurus. Picture credit: Everything Dinosaur.
Picture credit: Everything Dinosaur
The image (above) is a drawing of the Early Jurassic sauropodomorph Lufengosaurus.
The research team concludes that miniaturisation and staying small, combined with a reduction in skull bones and a switch to an insectivorous diet allowed the ancestors of modern mammals to thrive in the shadows of the Dinosauria. Having nocturnal habits may also have permitted these animals to carve out their own ecological niches in dinosaur dominated ecosystems.
It was not until dinosaurs became extinct at the end of the Cretaceous, some 66 million years ago, that mammals had a chance to further diversify and reach the large range of body sizes seen in many extant mammals today.
Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham in the compilation of this article.
The scientific paper: “Functional reorganisation of the cranial skeleton during the cynodont–mammaliaform transition” by Stephan Lautenschlager, Michael J. Fagan, Zhe-Xi Luo, Charlotte M. Bird, Pamela Gill and Emily J. Rayfield published in Communications Biology.
