A team of international researchers has named a remarkable new species of long-necked dinosaur from Thailand. Uragasaurus kalasinensis is the first formally described member of the Mamenchisauridae from Thailand. Although the fossil evidence consists of a single vertebra, the bone preserves a unique combination of anatomical features that enabled scientists to identify an entirely new dinosaur.  It is the fifteenth dinosaur to be named from fossils discovered in Thailand.

The research, published as an open-access paper in the journal “Scientific Reports”, highlights the growing importance of Thailand in helping palaeontologists understand the evolution and distribution of giant sauropod dinosaurs during the Late Jurassic.

Uragasaurus kalasinensis and the Mamenchisauridae

The newly described dinosaur lived approximately 145–150 million years ago during the Late Jurassic. Its fossil was recovered from the Phu Noi locality in Kalasin Province, north-eastern Thailand, within the Phu Kradung Formation.

Mamenchisaurids are famous for their extraordinarily long necks. Most known mamenchisaurids have been discovered in China, so the identification of Uragasaurus kalasinensis (pronounced You-rah-ga-sore-us cal-ah-sin-en-sis), considerably extends the confirmed geographical distribution of this distinctive group.

Scientists estimate that Uragasaurus measured around twenty metres in length and was a huge plant-eater that browsed vegetation growing high above the ground. Its neck has been described as being as long as a cricket pitch.

A herd of Uragasaurus kalasinensis feeding in a Late Jurassic forest in Thailand. A metriacanthosaurid theropod can be seen in the background along with a pair of rhamphorhynchoid pterosaurs. Picture credit: Pakorn Chotchaiyaporn.

Picture credit: Pakorn Chotchaiyaporn. Licensed under a Creative Commons Attribution 4.0 International License.

A Single Vertebra Tells an Extraordinary Story

The fossil consists of an anterior dorsal vertebra. At first glance, naming a dinosaur from just one bone might seem surprising. However, vertebrae contain numerous anatomical characteristics that are extremely useful for identifying different dinosaur groups. Individual sauropod vertebrae often preserve unique anatomical characteristics that enable researchers to recognise and describe new species.

The researchers carefully compared the fossil with vertebrae belonging to many other Asian sauropods. They found a unique arrangement of bony ridges, cavities and supporting structures, known as laminae, which had not previously been documented in any recognised species. This distinctive combination of features justified the establishment of the new genus Uragasaurus.

The holotype anterior dorsal vertebra of Uragasaurus kalasinensis (PRC 460) in anterior (a) and posterior (b) views. Digital rendering of the specimen in anterior (c), posterior (d), right lateral (e), left lateral (f), dorsal (g), and ventral (h) views. Asterisk refers to an autapomorphic character. The blue highlight indicates the pneumatic fossa and pleurocoel. Picture credit: Nilpanapan et al.

Picture credit: Nilpanapan et al. Licensed under a Creative Commons Attribution 4.0 International License.

A Growing Picture of Thailand’s Dinosaur Fauna

Thailand has become increasingly important for dinosaur research over the last three decades. Numerous excavations have revealed an impressive diversity of prehistoric animals, including theropods, ornithopods and several species of sauropod.

To read an article from 2019 highlighting the discovery of two new theropod species from north-eastern Thailand: Two New Theropod Dinosaurs from Thailand.

The discovery of Uragasaurus kalasinensis demonstrates that north-eastern Thailand preserves fossils of dinosaur groups previously thought to be largely restricted to China. It also suggests that mamenchisaurids dispersed more widely across eastern Asia than palaeontologists had previously appreciated. The researchers propose that continued exploration of the Phu Kradung Formation is likely to reveal additional fossils that will help clarify the evolutionary history of these spectacular long-necked dinosaurs.

The giant Nagatitan chaiyaphumensis, the fourteenth dinosaur to be described from Thailand: The Last Titan from Thailand.

A Single Vertebra Can Rewrite Dinosaur History

While complete dinosaur skeletons understandably capture the public imagination, they are extremely rare. Discoveries such as Uragasaurus kalasinensis remind us that experienced palaeontologists can extract an enormous amount of scientific information from isolated bones. Careful anatomical comparisons often reveal evolutionary relationships that would otherwise remain hidden.

A comparison of the anterior dorsal vertebrae of Uragasaurus kalasinensis with other Late Jurassic mamenchisaurids. Mamenchisaurus youngi (Upper Shaximiao Formation of Sichuan, China) and Mamenchisaurus hochuanensis (Upper Shaximiao Formation of the Chongqing municipality, China). Abbreviations lprdl, lower prezygodiapophyseal lamina; uprdl, upper prezygodiapophyseal lamina. Other abbreviations can be found in the second image in this article.  Asterisk refers to an autapomorphic character. The blue highlight indicates the pneumatic fossa and pleurocoel. Note images are not to scale. Picture credit: Nilpanapan et al.

Picture credit: Nilpanapan et al. Licensed under a Creative Commons Attribution 4.0 International License.

A Significant Discovery

The description of Uragasaurus kalasinensis represents another important milestone for Southeast Asian palaeontology. The discovery strengthens evidence that Thailand preserves an exceptionally important record of Jurassic dinosaurs and demonstrates that many new species remain to be discovered.

As fieldwork continues across the region, further fossil discoveries are likely to improve our understanding of how giant sauropods evolved and dispersed across Asia during the Jurassic.

Commenting on the research, Mike from Everything Dinosaur said:

“This fascinating study demonstrates how even a single fossil bone can significantly improve our understanding of dinosaur evolution. Thailand continues to produce scientifically important discoveries, and Uragasaurus kalasinensis adds another impressive dinosaur to the country’s growing fossil record.”

The scientific paper: “A new mamenchisaurid sauropod from the Lower Phu Kradung Formation, Upper Jurassic of northeastern Thailand” by Apirut Nilpanapan, Sita Manitkoon, Varavudh Suteethorn and Komsorn Lauprasert an open-access paper published in Scientific Reports.

A new study examining Tyrannosaurus rex hatchlings has provided fresh insight into the early lives of these famous theropod dinosaurs. Researchers writing in the journal “Biology” investigated evidence linked to the development and reproductive strategies of large meat-eating dinosaurs.  The researchers concluded that tyrannosaurs produced relatively small hatchlings compared to modern birds. This suggests that they laid large numbers of eggs and invested less energy in caring for their young.

Although adult Tyrannosaurus rex specimens are amongst the most famous fossils ever found, the earliest growth stages remain poorly understood. Fossils of very young tyrannosaurs are exceptionally rare. Therefore, palaeontologists continue to search for clues about how these remarkable animals developed.

The beautiful Tristan the Tyrannosaurus rex skull shown in lateral view. A new study suggests different niches in the ecosystem for juvenile tyrannosaurs compared to the adult animals. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Studying Tyrannosaurus rex Hatchlings

The enormous size of adult T. rex raises fascinating questions about reproduction. Every giant dinosaur began life as a small hatchling.  All dinosaurs emerged from eggs. Consequently, scientists want to understand how these animals grew from vulnerable juveniles into apex predators.

The scientists, which included researchers from the University of Bath, examined fossil evidence and compared growth patterns seen in related dinosaurs. This work helps palaeontologists build a more complete picture of tyrannosaur biology. Dinosaurs occupied an evolutionary position between more primitive reptiles and modern birds, both in their anatomy and in some aspects of their biology such as reproduction strategies.

Young tyrannosaurs would have looked very different from adults. They were probably lightly built, long-legged animals adapted for speed. In contrast, mature T. rex individuals developed huge skulls, powerful jaws and immense bite forces.

This dramatic transformation demonstrates how dinosaurs could occupy different ecological roles during their lives.

Tyrannosaur hatchlings had very different body proportions compared to adults. A new study provides fresh insights into tyrannosaur reproduction strategies. Picture credit: Everything Dinosaur (AI Assisted).

Picture credit: Everything Dinosaur (AI Assisted)

Understanding Dinosaur Growth and Reproduction

The study also highlights the challenges associated with investigating dinosaur reproduction. Unlike modern birds and reptiles, palaeontologists cannot directly observe extinct dinosaurs nesting or raising their young.

Instead, scientists rely on fossils, bone histology, eggs, embryos and comparisons with related, extant animals. Dinosaur reproductive strategies probably represented an intermediate stage between more primitive reptiles, such as crocodilians which typically provide limited parental care, and modern birds. Birds often demonstrate advanced parental behaviours and significant investment in their offspring.

Evidence from other theropod dinosaurs shows that many species grew rapidly. This fast growth helped them reach larger sizes more quickly and may have reduced the risks faced by young animals.

From Tiny Hatchling to Apex Predator

An adult Tyrannosaurus rex could reach more than twelve metres in length. However, newly hatched individuals would have been tiny compared to their parents. The research team studied bones and teeth of hatchlings from the Frenchman Formation of Saskatchewan (Canada). These fossils reputedly represent T. rex. In addition, juvenile tyrannosaur fossils from the geologically older Dinosaur Provincial Park formation were studied. These fossils have been assigned to Gorgosaurus.

The difference between hatchlings and adults suggests that young tyrannosaurs may have hunted different prey. This reduced competition between generations and allowed animals of different ages to exploit separate ecological niches. Indeed, the contrasting body shapes between juvenile and mature tyrannosaurs fuelled the Nanotyrannus debate.  However, recent studies have concluded that lightly built, long-legged tyrannosaurs thought to represent T. rex juveniles are most likely a different tyrannosaur taxon.

To read more about the recent Nanotyrannus research: New Paper Reinforces Nanotyrannus Unique Taxon Theory.

This idea, animals of the same species filling different niches depending on their age is known as ontogenetic niche partitioning, has been proposed for several dinosaur groups.

Revealing the Early Lives of Famous Dinosaurs

The study of Tyrannosaurus rex hatchlings remains an exciting area of palaeontology. For example, in this paper, the researchers stated that synchrotron scans revealed Haversian bone re-modelling, suggesting that tyrannosaurs moved soon after hatching.  It is speculated that tyrannosaurs may have been precocial.  Precocial young are relatively mobile and independent soon after hatching.

A 2021 article that highlights a study suggesting that baby tyrannosaurs were precocial: Tyrannosaurs – Born Ready to Hunt!

Future fossil discoveries may reveal more information about nesting behaviour, growth rates and juvenile anatomy.

Everything Dinosaur team members regularly highlight that even the most famous dinosaurs continue to surprise scientists. New research techniques and fossil discoveries are helping experts build a clearer picture of how these extraordinary animals lived. Understanding the youngest members of this species provides valuable information about one of the most remarkable predators in Earth’s history.

A dinosaur egg (believed to be from a theropod dinosaur). Theropod dinosaur eggs tend to be elongated and less round compared to the eggs of other dinosaurs such as sauropods. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Estimating Nest Sizes

Clutch sizes were likely large. The team conservatively estimated that a small, female adult T. rex would lay around twenty eggs. The largest T. rex females could perhaps lay thirty eggs. In comparison, Gorgosaurus (G. libratus), may have laid more eggs per clutch. For example, the researchers propose clutch sizes of up to a hundred eggs for Gorgosaurus.

Scientists can only speculate about the mortality rate of hatchling tyrannosaurs. However, animals that produce large numbers of offspring typically experience high juvenile mortality rates. Many predators could have killed a baby T. rex. For example, hatchlings had to avoid dromaeosaurs, crocodilians and the powerful beaks of azhdarchid pterosaurs.

The scientific paper “Hatchlings of Tyrannosaurus rex and the Evolution of Dinosaur Reproductive Strategies” by Nicholas R. Longrich, Peter J. Makovicky, Tim Tokaryk, David M. L. Cooper, Evan T. Saitta, Gregory M. Erickson, Tamas Szekely and Eric Snively published in Biology.

The Everything Dinosaur website: Models of Theropods and Other Dinosaurs.

The study of Thylacoleo carnifex anatomy has revealed one of the most unusual mammalian predators known to science. Often called the “marsupial lion”, this apex predator was not a member of the cat family.  Indeed, its closest living relatives are wombats and koalas. Despite evolving from primarily plant-eating ancestors, Thylacoleo carnifex became a highly specialised carnivore. Its powerful jaws, extraordinary teeth and muscular body made it a significant predator of the Pleistocene Epoch.  Early studies suggested that it may have been frugivore (fruit eater), or that it was a scavenger.  However, more modern interpretations depict Thylacoleo carnifex as a hypercarnivore.

Understanding Thylacoleo carnifex Anatomy

The first fossils of Thylacoleo carnifex were scientifically described in the 19th century. Since then, more complete fossil discoveries have transformed our understanding of this animal. Older reconstructions often depicted Thylacoleo as cat-like. However, detailed studies show that this marsupial had a very different body plan. It combined tremendous strength with adaptations for climbing, gripping and ambushing prey.

A large individual may have measured around 1.5 metres long. Many adults probably weighed between 100 and 130 kilograms, although exceptionally large specimens may have approached 160 kilograms. Larger individuals may represent males, suggesting possible sexual dimorphism. After all, sexual dimorphism is seen in extant relatives of this species.

This extinct marsupial continues to inspire scientists and palaeoartists.  For instance, it has featured on the front cover of the prestigious “Prehistoric Times” magazine.

The front cover features a Marsupial lion. Thylacoleo carnifex features on the front cover art of “Prehistoric Times” magazine issue 85. Picture credit: Mike Fredericks.

Picture credit: Mike Fredericks

A Powerful Skull and an Incredible Bite

The skull of Thylacoleo carnifex was short, broad and extremely robust. Huge jaw muscles helped generate a tremendous bite force. Indeed, studies suggest that relative to body size, Thylacoleo possessed one of the most powerful bites of any known mammalian predator. The eyes faced forwards, providing binocular vision. This adaptation would have helped with judging distance when attacking prey. Consequently, palaeontologists often interpret Thylacoleo as an ambush hunter rather than a pursuit predator.

The Remarkable Teeth of Thylacoleo carnifex

One of the most fascinating aspects of Thylacoleo carnifex anatomy is the dentition. Unlike felids, Thylacoleo did not rely on large canine teeth to despatch prey. Its upper canines were small and rounded, whilst the lower jaw lacked canine teeth entirely.

The dental formula of T. carnifex:

• Upper jaw (each side): 3 incisors, 1 canine, 3 premolars and 1 molar
• Lower jaw (each side): 1 incisor, no canines, 3 premolars and 2 molars.

The lower incisors were enlarged, chisel-shaped and projected forwards.  In addition, fossils show extensive wear. The enormous third premolars were highly specialised. They acted like shears and were functionally similar to the carnassial teeth found in modern carnivorous mammals.

No living predator has a set of teeth quite like Thylacoleo carnifex.

To read an article about the discovery of an ancestor of the “marsupial lion”: Attenborough’s New Kitty.

Strong Forelimbs and a Deadly Thumb Claw

The forelimbs of Thylacoleo were exceptionally powerful. The shoulders and front legs were heavily muscled, suggesting an animal that relied on strength to subdue prey. Furthermore, the manus (hand) had five digits, each equipped with a claw. The first digit, equivalent to a thumb, was particularly remarkable. It was semi-opposable and carried a large, strongly curved claw.

This enlarged claw was probably used to grip prey and assist with climbing. It may have been protected when not in use, although it worked differently from the retractable claws of modern cats.

A Marsupial Built for Power Not for Speed

The body of Thylacoleo carnifex was compact and muscular. It had a deep chest, broad shoulders and a relatively short back. Its body proportions suggest that this predator was not built for chasing prey over long distances. Instead, it was adapted for explosive power, climbing ability and controlling struggling animals. The hind feet provide further evidence that Thylacoleo was no cat-like predator. It walked with the sole of the foot contacting the ground, a posture known as plantigrade locomotion. Bears and humans also use this type of stance.

The potential maximum velocity of Thylacoleo remains unknown.  The combat bodies of extant wombats (see image below) share many characteristics with their close relatives (Thylacoleonidae).  At first sight, these animals might look like they are incapable of running at speed.  However, appearances can be deceptive.  Wombats have been recorded running at twenty-five miles per hour (forty kilometres per hour) over short distances.

Like other diprotodontian marsupials, the second and third toes were probably fused together.

Thylacoleo is classified as a member of the Diprotodontia suborder the Vombatiformes. Extant wombats such as this forest wombat (Vombatidae family) are closely related to marsupial lions (Thylacoleonidae).

Picture credit: Everything Dinosaur

The Tail of Thylacoleo carnifex

For many years, the tail of Thylacoleo was poorly understood. However, more complete fossil discoveries have revealed that this predator had a long and muscular tail.

The tail may have provided extra support when the animal reared upwards. This “tripod” posture is seen in some living marsupials.

Some Australian rock art has been suggested to represent Thylacoleo. These interpretations remain debated, but they raise interesting questions about the external appearance of this extinct animal. For example, there could have been a tuft on the end of the tail.

Did Thylacoleo carnifex Hunt Diprotodon?

Thylacoleo carnifex shared its environment with many famous Australian megafauna species, including the giant marsupial Diprotodon optatum. Diprotodon was the largest marsupial known to science. A fully-grown male Diprotodon had a shoulder height of approximately 1.8 metres.  It weighed around three tonnes, around twenty-five times heavier than Thylacoleo.

However, Thylacoleo may have targeted young, injured or vulnerable individuals. Its powerful forelimbs, gripping claws and devastating bite would have made it a dangerous predator.  The CollectA Deluxe Diprotodon, introduced in 2024 shows some remarkable detail.  For example, the top of the left hind limb reveals an old scar from an attack from a Thylacoleo. The scars are old suggesting an attack when this Diprotodon was much younger.

Whilst speculative, it is interesting to note that CollectA added this detail, a speculation on a predator/prey relationship.

The CollectA Diprotodon model has an old scar from a marsupial lion on its rump.

The relationship between these two iconic marsupials highlights the complexity of prehistoric Australian ecosystems.

To view the CollectA Deluxe model range: CollectA Deluxe Age of Dinosaurs.

Thylacoleo carnifex Anatomy Reveals A Unique Australian Predator

Research into Thylacoleo carnifex anatomy continues to demonstrate how unusual this animal was. It was not simply Australia’s version of a big cat. Instead, evolution produced a completely different type of predator. Indeed, several species have been classified, tracing the origins of these bizarre carnivores back into the Oligocene Epoch.

To read a blog post outlining ideas into Thylacoleo hunting strategy: How the Marsupial Lion Got to Grips with its Prey.

Mike from Everything Dinosaur commented:

“With its powerful front limbs, extraordinary teeth and specialised hunting adaptations, Thylacoleo remains one of the most fascinating mammals to have ever lived.  Thylacoleo carnifex died out around 40,000 years ago.  Modern humans would have encountered it.  Imagine viewing a living Thylacoleo!  I am sure this creature would have had a special status amongst those hunter gatherers that shared its environment.”

The award-winning Everything Dinosaur website: Dinosaur Toys and Prehistoric Animal Models.

New research suggests that colourful tapejarid pterosaurs may have been even more spectacular than previously imagined. A recently published study proposes that some of these flying reptiles possessed iridescent pycnofibres that produced shimmering colours. As a result, these structures may have played an important role in visual signalling and display.

The bodies of pterosaurs, the first vertebrates to achieve powered flight, are covered with integumentary filaments (pycnofibres). They are thought to be homologous with feathers associated with the Dinosauria.

The Age of Dinosaurs Deluxe Caiuajara pterosaur figure with a moveable jaw. Tapejarid pterosaurs like Caiuajara have been depicted with colourful crests, however, a recent study (May 2026) proposes that the pycnofibres covering their bodies may have been iridescent.

The image (above) shows the CollectA Supreme Deluxe Caiuajara figure.  It is pronounced – Kay-you-ah-jar-rah.  CollectA have introduced an extensive range of beautiful pterosaur scale models.

To view the CollectA Deluxe model range: Scale Models of Pterosaurs and Other Prehistoric Animals.

Colourful Tapejarid Pterosaurs

The Tapejaridae were a geographically widespread Early Cretaceous pterosaur family with probable Asian origins.  Tapejarid fossil material is known from the UK, Europe, Africa, South America and possibly from North America too.  All known tapejarids were edentulous (lacked teeth). These pterosaurs are famed for their large and flamboyant crests.  A recently published paper suggests that pycnofibres covering their bodies may have been capable of iridescence.  If this is the case, they would have been extremely colourful.

To read a blog post from 2020 about the discovery of a tapejarid pterosaur in the Wessex Formation (Wightia declivirostris): A Terrific Tapejarid from the Isle of Wight.

Significantly, the recently published paper reveals evidence of something remarkable.

Scientists identified a layered arrangement of melanosomes within the pycnofibres of a tapejarid specimen. The fossil material represents Sinopterus dongi from the Early Cretaceous Jehol Biota.  It had not been formally studied previously. Importantly, this internal structure of melanosomes resembles the organisation seen in the iridescent feathers of living birds. In modern species, such arrangements generate structural colours that can shift and shimmer when viewed from different angles. Consequently, the researchers propose that these pterosaurs exhibited colours ranging from green to magenta.

Did Iridescence Appear Early in the Evolution of Integumentary Filaments?

The research also has wider implications. According to the authors, this discovery indicates that the capacity for producing iridescence evolved very early in the evolution of integumentary filaments. Therefore, complex colour signalling and visual displays may have originated long before the appearance of birds.

In addition, the research provides further evidence that pycnofibres were multifunctional. Although they probably helped with insulation and thermoregulation, they also appear to have been used for communication and display. This finding supports the idea that visual signalling played a significant role in pterosaur behaviour. After all, if you are a tapejarid with a bold crest, then why not have iridescent pycnofibres too?  The Early Cretaceous skies could have been filled with colourful tapejarid pterosaurs.

Highlighting the importance of this recent research, Mike from Everything Dinosaur commented:

“Large head crests already made tapejarids some of the most distinctive pterosaurs known. Now, scientists suggest that these reptiles may have enhanced their appearance with dazzling colours. Such displays could have helped attract mates, establish dominance or identify members of the same species.”

Implications for Palaeoartists and Model Makers

Most pterosaurs very probably had excellent colour vision.  Using colour for signalling, social status and display makes sense.  This has implications for model makers and palaeoartists. As a result of this study, colourful tapejarid pterosaurs may have looked far more vibrant than traditionally portrayed. They might have rivalled many modern birds in both appearance and visual complexity.

A model of Tapejara imperator (Safari Ltd)

The image (above) shows a model of a tapejarid pterosaur (Tapejara imperator).  Most models have bright crests, but the pycnofibres tend to be plain in comparison. The conclusions from this study suggest a re-think when it comes to pterosaur colouration.

The paper highlights how exceptionally preserved fossils continue to transform our understanding of prehistoric life. Moreover, it demonstrates that the skies of the Cretaceous Period may have been filled with flying reptiles adorned with brilliant, iridescent colours.

The scientific paper: “Iridescence in pterosaur pycnofibers and the evolution of integumentary coloration” by Zelin Wu, Liliana D’ Alba, Chang-Fu Zhou, Julia A. Clarke, Jinhua Li, Matthew D. Shawkey and Quanguo Li published in bioRxiv.

The award-winning Everything Dinosaur website: Models of Pterosaurs and Other Prehistoric Animals.

A newly published study examining the growth rates of Dimetrodon teutonis and Dimetrodon natalis has provided a fresh perspective on a famous, primitive synapsid. Researchers have discovered that the smallest known species of Dimetrodon achieved their diminutive size in contrasting ways. The study provides fresh insights into the lives of these iconic sail-backed predators that roamed the Earth millions of years before the dinosaurs evolved.

The Dimetrodon genus comprises several species. Most of these species grew into large predators more than three metres in length.  For example, Dimetrodon grandis measured about 3.2 metres long and weighed approximately 250 kilograms. However, a few species were much smaller. An international team of researchers has now investigated how these animals evolved their reduced body size.

Dimetrodon teutonis – The Smallest Known Dimetrodon Species

The study focused on two species. One is Dimetrodon natalis from North America. The other is Dimetrodon teutonis from the Bromacker fossil site in Germany. This German species is significant because it is the only known Dimetrodon discovered outside North America.

For many years, D. natalis was regarded as the smallest species. However, D. teutonis turned out to be even smaller.

• Dimetrodon natalis – named in 1936 by Romer from earlier work by Cope. It measures about 1.7 metres long with an estimated bodyweight of 38 kilograms*.
• Dimetrodon teutonis – named in 2001 (Berman, Reisz, Martens and Henrici) and measuring around 70 cm in length and weighing approximately 24 kilograms*.

Limb bone midshaft circumference analysis of fossil material used in this research suggests that the individual animals representing D. teutonis had a body weight of 6.3 to 6.8 kilograms. In contrast, the same analysis method provides body weight estimates for the D. natalis individuals between 20.9 and 21.7 kilograms.

To learn more about these animals, the scientists examined the microscopic structure of fossil bones. Bone tissue preserves information about growth rates and development. Therefore, it can reveal important details about the life history of extinct species.

Bone Histology Reveals Different Life Histories

The results have been published in the academic journal “Scientific Reports”. They show that the two species followed contrasting growth strategies. Dimetrodon natalis appears to have grown quickly. However, it stopped growing at an early age. As a result, it reached adulthood while remaining small. In contrast, Dimetrodon teutonis grew much more slowly. It continued developing over a longer period. The researchers suggest that it probably reached sexual maturity later in life.

Bone histology comparison between D. teutonis and D. natalis demonstrates fundamentally different bone microanatomy. The humerus cross section of D. teutonis (left) exhibits thin cortices composed of poorly vascularized parallel-fibered bone. This suggests slow growth and delayed maturity. In contrast, the bone histology of D. natalis (right) shows thick and highly vascularised woven to parallel-fibered bone cortices. Picture credit: Frederik Spindler, PALAEONAVIX.

Picture credit: Frederik Spindler, PALAEONAVIX

Dr Tom Hübner, curator and head of the Bromacker project at the Friedenstein Foundation Gotha, commented:

“This work demonstrates that bone histology can provide direct insights into the palaeobiology of long-extinct animals. Who would have thought that these two small species had such different life histories?”

Different Environments Influenced Growth

According to the research team, environmental conditions played a key role. North American Dimetrodon species lived in humid lowland habitats. These ecosystems contained abundant food resources. In addition, predators were common. Under these conditions, rapid growth would have offered advantages for survival and reproduction.

The Bromacker ecosystem in Germany presented different challenges. Seasonal droughts and limited resources shaped this environment. Fossilised burrows suggest that potential prey animals retreated underground during dry periods. Consequently, slower growth may have helped Dimetrodon teutonis cope with fluctuating food supplies.

Dr Aurore Canoville explained:

“These new findings once again highlight the uniqueness of the Bromacker locality compared with other Early Permian fossil sites. They make Dimetrodon even more fascinating. Long before dinosaurs dominated the Earth, these early synapsids were already responding in remarkably flexible ways to climate, food availability, competition and predation.”

Unique Insights from the Bromacker Fossil Site

Professor Jörg Fröbisch of the Museum für Naturkunde Berlin emphasised the importance of the discovery.

He stated:

“These fascinating results provide an increasingly complete picture of the Bromacker ecosystem and its enormous potential for many decades of future research.”

The study highlights how adaptable these early synapsids were. It also demonstrates the importance of the Bromacker fossil locality. Thanks to discoveries such as these, scientists continue to improve our understanding of life during the Early Permian.

Unique fossil provides information on Bromacker food web: Regurgitated Pellet from a Dimetrodon.

In the paper, the researchers state that the largest known species of Dimetrodon is D. angelensis.  It is stated that this species was up to 4.6 metres long and weighed 250 kilograms.

Everything Dinosaur acknowledges the assistance of a media release from the Museum für Naturkunde Berlin in the compilation of this article.

The scientific paper: “Contrasting life history in the diminutive Dimetrodon species from North America and Germany” by Aurore Canoville, Philipp L. Knaus, Lorenzo Marchetti and Jörg Fröbisch published in Scientific Reports.

The award-winning Everything Dinosaur website: Models of Palaeozoic Creatures and Other Prehistoric Animals.

The debate about lips in dinosaurs continues.  Whether dinosaurs possessed extraoral tissue remains controversial. However, a remarkable new study has added substantial support to the idea that most dinosaurs possessed extraoral tissues that covered and protected their teeth. A new study, published in the journal “Palaeontology” provides compelling evidence that lips were the ancestral condition in dinosaurs and many other reptiles.

Researchers led by Rafael Terras (Programa de Pós-Graduação em Ciências Ambientais, Universidade Comunitária da Região de Chapecó, Chapecó, Brazil), have examined Triassic archosaurs from Brazil. Their findings suggest that lips in dinosaurs were not an unusual feature. Instead, they may represent the ancestral condition for the entire Sauropsida, the group that includes reptiles and birds.

Importantly, this study does not stand alone. Rather, it builds upon previous work by researchers such as Robert Bakker, Thomas Paul, Casey Holliday, Mark Witton and Thomas Cullen. Consequently, the scientific case for lips in dinosaurs continues to grow.

A Debate That Goes Back More Than a Century

The idea of lips in dinosaurs is not new. In the 1920s, palaeontologist Charles Gilmore suggested that openings in the jaw of Ceratosaurus transmitted nerves and blood vessels to the lips. Later, Robert Bakker proposed that many dinosaurs possessed thin, immobile lips similar to those seen in living lizards. Ironically, the advent of cinema and the need to make dinosaurs scary by showing their teeth could have popularised non-lipped dinosaurs with the public.

More recently, the landmark 2023 study by Cullen and colleagues demonstrated that theropod teeth show little evidence of the wear expected if they had remained permanently exposed. Their work also highlighted similarities between theropod skull anatomy and living squamates.

To read more about the 2023 study: New Paper Suggests Dinosaurs Had Lips.

Now, this new study extends these observations far beyond the Theropoda.

Studying Triassic Archosauromorphs from Brazil

The researchers examined numerous Triassic archosaurs from southern Brazil. These included early dinosaurs and several crocodile-line relatives.

They found several features associated with covered teeth.  For example, the team examined the location of foramina (tiny openings in the skull bones which are location points for nerves).

The researchers identified the following, consistent characteristics:

• rows of horizontally arranged facial foramina.
• fewer than one hundred foramina per rostral bone.
• vertically orientated teeth.
• a lack of interlocking teeth.
• uniform enamel thickness.
• no evidence of exposed dentine.
• a positive relationship between skull length and tooth crown height.

These characteristics closely resemble those seen in living lizards (lepidosaurs) rather than modern crocodilians. As a result, the authors concluded that labial scales and extensive gingiva (soft tissue that supports the teeth – gums) probably enclosed the teeth.

Foramina in selected Triassic saurischians. A, Buriolestes (ULBRA PVT 280). B, Buriolestes (CAPPA/UFSM 0035). C, Pampadromaeus (ULBRA PVT 016). D, Gnathovorax (CAPPA/UFSM 0009). E, Unaysaurus (UFSM 11069). F, Macrocollum (CAPPA/UFSM 0001a). G, Gnathovorax (CAPPA/UFSM 0009). H, Macrocollum (CAPPA/UFSM 0001d). Abbreviations: edf, ellipsoid dentary foramen; emf, ellipsoid maxillary foramen; faaf, foramen anterior to the maxillary fenestra; fdaf, foramen dorsal to the antorbital fenestra; gif, groove-inserted foramen; odf, oval dentary foramen; omf, oval maxillary foramen; opmf, oval premaxillary foramen; sbg, subnarial gap; sf, subnarial foramen. Scale bars represent: 10 mm (A–C, E, H); 25 mm (D, F, G). Picture credit: Terras et al.

Picture credit: Terras et al

Tooth Histology Provides Important Clues for Lips in Dinosaurs

The researchers also examined thin sections of fossil teeth. They discovered that enamel thickness remained consistent around the crowns. Furthermore, the dentine showed no signs of wear. This condition contrasts strongly with crocodilians, whose exposed teeth experience significant abrasion. Therefore, the teeth of these Triassic archosaurs appear to have remained hydrated and protected.

This conclusion mirrors the findings published by Cullen and colleagues in the 2023 paper. Consequently, independent lines of evidence are converging on the same answer.

Studying the Pseudosuchian Prestosuchus

One of the most intriguing aspects of the study concerns the giant pseudosuchian Prestosuchus. This large, terrestrial predator possessed a distinctive gap between the upper and lower jaws. At first glance, this arrangement might suggest permanently exposed teeth. However, the researchers argue otherwise. They propose that a mandibular gap existed between the jaws. Soft tissues and gingiva would have occupied this space and maintained a complete oral seal. In effect, the teeth remained covered despite the unusual skull shape.

Prestosuchus skulls and reconstructions. A, ULBRA PVT 281 crushed skull in right lateral view. B, reconstruction of UFRGS PV 0629 T in right lateral view (mirrored) with a mandibular gap; modified from Mastrantonio et al. (2019). C–D, life reconstructions of ULBRA PVT 281: C, in right lateral view with a closed mouth displaying the oral seal; D, in frontal view with an open mouth displaying the oral rim; artwork by Matheus F. Gadelha used with permission. Scale bars represent: 300 mm (A, C, D); 100 mm (B). Picture credit: Terras et al with illustrations by Matheus F. Gadelha.

Picture credit: Terras et al with illustrations by Matheus F. Gadelha

This interpretation is significant. It demonstrates that specialised skull anatomy does not necessarily imply exposed teeth. Moreover, it suggests that lips could be retained even in large-bodied predators with unusual cranial morphology.

Prestosuchus (P. chiniquensis) is an extinct archosaur more closely related to extant crocodilians than to the Dinosauria. Size estimates vary but it could have reached a length of five metres or more. It was one of the largest Triassic pseudosuchians and an apex predator.

The Wild Safari Prehistoric World Prestosuchus model.

The image (above) shows a model of the Triassic predator Prestosuchus.  This model was introduced in 2019.  The model has exposed teeth and no extraoral tissue.  It was made prior to the recent research suggesting the presence of lips in dinosaurs and other archosaurs.  The Prestosuchus model is from the Wild Safari Prehistoric World range of figures.

Wild Safari Prehistoric World: Prehistoric Animal Models and Figures.

Lips in Specialised Archosauromorphs

The authors also considered a number of highly specialised forms. They concluded that lips probably occurred in a wide variety of archosaurs.  For example, the researchers suggest that Triassic theropods had lips, along with sauropodomorph dinosaurs.  In addition, they propose that ornithosuchids (pseudosuchian archosaurs – crocodilian lineage) had lips.  Furthermore, the researchers propose that proterosuchids (basal archosaurs) also had extraoral tissue.  It is suggested that phytosaurs had lips too. Some archosauromorphs evolved additional keratinous coverings. These structures formed primitive beaks (rhamphothecae).

Triassic archosauromorphs reconstructed with labial scales and the oral seal in lateral view. A, Gnathovorax (CAPPA/UFSM 0009; Herrerasauria). B, Pampadromaeus (ULBRA PTV 016; Sauropodomorpha). C, Machaeroprosopus (NMMNH P-4983; Phytosauria). D, Riojasuchus (PVL 3827; Ornithosuchidae). E, Proterosuchus (NMQR 880; Proterosuchidae). F, Silesaurus (ZPAL Ab III/361; Silesauridae). G, Venetoraptor (CAPPA/UFSM 0356; Lagerptidae). H, ‘Hyperodapedon’ (ULBRA PVT 053; Rhynchosauria). I, Prestosuchus (ULBRA PTV 281; Loricata). Artwork by Matheus F. Gadelha used with permission. Scale bars represent: 50 mm (A, D); 20 mm (B, F); 100 mm (C, H); 30 mm (E); 10 mm (G); 300 mm (I). Picture credit: Terras et al with illustrations by Matheus F. Gadelha.

Picture credit: Terras et al with illustrations by Matheus F. Gadelha

A Complex Picture

The evolution of facial tissues in archosaurs appears to have been far more complex than previously thought.  However, extraoral soft tissues such as lips were probably the ancestral condition. According to the authors of the study, lips represent the primitive condition for the Sauropsida. Therefore, the common ancestor of reptiles and birds likely possessed covered teeth.

If correct, exposed teeth evolved later.  Extant crocodilians would represent a more derived branch of the Archosauria. Their exposed dentition and highly sensitive facial skin appear to be derived adaptations rather than the ancestral state. This finding reverses a common assumption.  However, the debate about lips in dinosaurs and their near relatives is likely to continue.

Instead of asking why dinosaurs had lips, researchers may need to explain why crocodilians lost them.

A Growing Scientific Consensus

No single paper or study can settle such a complex question. Nevertheless, the evidence continues to accumulate. Studies of facial foramina, tooth wear, enamel thickness and skull proportions increasingly point in the same direction. Taken together, they indicate that most dinosaurs probably possessed extraoral tissues covering their teeth. As a result, reconstructions showing permanently exposed teeth may eventually become less common.

This study is significant because it suggests origins for this condition originated much earlier in archosaur evolution. Consequently, it provides fresh evidence that covered teeth were widespread among early members of the Archosauria. Furthermore, it strengthens the idea that the familiar crocodilian condition evolved later.

The head of a stuffed crocodile specimen (Nile crocodile) on display at the London Natural History Museum. The lack of extraoral tissue (lips) in this archosaur might be a derived condition. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Mike from Everything Dinosaur commented:

“This exciting new research adds another important piece to the puzzle. Evidence supporting lips in dinosaurs has been steadily accumulating for many years. The research team have shown that these soft tissues probably have much deeper evolutionary roots than previously thought. Their work strengthens the view that covered teeth represented the ancestral condition in dinosaurs and many of their close relatives. As a result, palaeoartists and scientists are gaining an increasingly detailed picture of how these remarkable animals actually looked.”

Everything Dinosaur acknowledges the assistance of the study’s corresponding author in the compilation of this article.

The scientific paper: “Inferred presence of extraoral tissues in Triassic archosauromorphs and the evolutionary implications for the clade Sauropsida” by Rafael Terras, Jaqueline Borger, Manuelle O. P. Almeida, Silvia Bettin, Owen A. Higgins, Giulia Marciani, Stefano Benazzi, Rodrigo T. Müller, Leonardo Kerber and Mirian Carbonera published in Palaeontology.

The Everything Dinosaur website: Museum Quality Models of Archosaurs.

Recently, we published a post highlighting the on-going research into the remarkable Oxfordshire “dinosaur highway”.  A limestone quarry preserves the remains of numerous dinosaur tracks.  The tracks are preserved in strata laid down in the Middle Jurassic.  Palaeontologists estimate that the trackways are around 166 million years old (Bathonian faunal stage).  In a recent radio interview, a researcher commented that one of the tracks could be a record breaker. At around 220 metres in length, one Oxfordshire trackway could represent the longest continuous sauropod trackway known to science. However, describing them as Cetiosaurus dinosaur tracks is somewhat controversial.

To read Everything Dinosaur’s earlier blog post: Oxfordshire Trackway Could be the Longest Sauropod Trackway Discovered to Date.

Could a Cetiosaurus Have Left the Longest Sauropod Trackway?

Whilst undoubtedly made by sauropods, it is difficult to assign with any certainty the taxon that walked across a lagoon that led to the footprints being trapped in time.  Indeed, as the tracks are different sizes, they could represent several taxa.  Alternatively, the tracks might represent a single species, but different aged individuals walking together.  However, Cetiosaurus is the sauropod most often mentioned in association with the trace fossils.  Why might that be the case?

An artist’s reconstruction of the Dewars Farm Quarry site 166 million years ago. A Megalosaurus tracks an adult Cetiosaurus with a second sauropod in the background whilst pterosaurs soar overhead. Picture credit: Mark Witton.

Picture credit: Mark Witton

Cetiosaurus is regarded as being a primitive member of the Sauropoda. Nevertheless, this is an important genus. It has the distinction of being regarded as the first sauropod dinosaur to be formally described (Owen 1841). However, Owen’s scientific study was inaccurate. For example, Owen suggested that the large vertebrae with their rough texture were similar to extant whale vertebrae. As the fossils had been found in marine deposits, Owen incorrectly concluded that the fossils represented an enormous marine crocodile.

Cetiosaurus oxoniensis

Unfortunately, most Cetiosaurus fossil specimens consist of fragmentary material.  Indeed, little is known about Middle Jurassic sauropods.  Significantly, the species Cetiosaurus oxoniensis was described from fossils found in Oxfordshire.  The material comes from deposits that are approximately the same age as the trackway bedding planes at the quarry site.  So, it is possible that these extensive trace fossils do indeed represent Cetiosaurus dinosaur tracks.

The enormous and robust right femur of a Middle Jurassic sauropod. The femur has been ascribed to the taxon Cetiosaurus. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Cetiosaurus Dinosaur Tracks

Whether or not these footprints represent Cetiosaurus dinosaur tracks remains open to debate.  However, as perhaps the first sauropod formally described, this taxon is iconic.  In addition, it is pleasing symmetry if a Cetiosaurus did leave what may prove to be the world’s longest sauropod trackway. Such an accolade only enriches England’s rich fossil heritage.

Mike from Everything Dinosaur commented:

“At around 220 metres in length, one Oxfordshire trackway could represent the longest continuous sauropod trackway ever discovered. Other lengthy European sauropod trackways are known.  For example, from Portugal and France.  These fossil trackways are over 140 metres in length, so they are considerably shorter than the trackway from Oxfordshire.  Nonetheless, they are still impressive and give palaeontologists the opportunity to learn more about these enormous creatures.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham supplied in January 2025 in the compilation of this article.

For sauropod models and other dinosaurs: Dinosaur Figures and Prehistoric Animal Models.

Scientists studying the famous Oxfordshire “dinosaur highway” have announced that one of the giant trackways may represent the longest known sauropod trackway discovered anywhere in the world. The remarkable sequence of footprints, uncovered at Dewars Farm Quarry, could have been made by a single Cetiosaurus as it wandered across a Jurassic mudflat around 166 million years ago.

The Dewars Farm Quarry excavation work taking place in June 2024. Picture credit: The University of Birmingham.

Picture credit: The University of Birmingham

A Giant Dinosaur Left Its Footprints

Researchers have traced the trackway for approximately two-hundred and twenty metres. This enormous trail records the movements of a huge, long-necked herbivore. Furthermore, scientists think the tracks were made by a Cetiosaurus or a sauropod similar to Cetiosaurus, the first sauropod to be scientifically described (Owen, 1841). In total, four sauropod trackways at the site have been discovered. In addition, the site has yielded several other trackways, including those of a meat-eating dinosaur.  These tracks have been tentatively assigned to Megalosaurus.

The original discovery attracted worldwide attention when details were formally announced in early 2025. The sauropod tracks represent animals of different sizes.  This suggests some intriguing possibilities.  For example, the tracks could represent a family moving together, or the trackways could represent a group of unrelated animals moving together.  In an interview with Radio Oxfordshire, co-leader of the excavation Dr Emma Nichols (Oxford University Museum of Natural History), opined that the trace fossils could represent more than one type of sauropod.

Working on the Dewars Farm Quarry dinosaur tracks. Picture credit: Caroline Wood University of Oxford.

Picture credit: Caroline Wood University of Oxford

The Oxfordshire “Dinosaur Highway” Made by a Cetiosaurus (Possibly)

The tracks cannot be linked directly to a skeleton. However, the footprints closely resemble those expected from a large, narrow-gauge sauropod. Consequently, scientists have suggested that the trackmaker was probably Cetiosaurus.

Cetiosaurus lived during the Middle Jurassic. It reached lengths of around eighteen metres and weighed many tonnes. Moreover, the type species, Cetiosaurus oxoniensis, was named from fossils discovered in Oxfordshire. Therefore, assigning the tracks to this dinosaur makes geological sense.

Fossils ascribed to the taxon Cetiosaurus on display at the Oxford University Museum of Natural History (OUMNH). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

To read Everything Dinosaur’s article from January 2025 (formal announcement of quarry discovery): Remarkable Dinosaur Highway Uncovered in Oxfordshire.

Following in the Footsteps of Jurassic Giants

Trackways provide a different type of evidence from fossil bones. Skeletons reveal anatomy. However, footprints capture behaviour. They show how dinosaurs moved and interacted with their environment. Using modern imaging techniques, researchers have created detailed three-dimensional models of the trackway. As a result, scientists can estimate walking speed and study the animal’s gait. The Oxfordshire trackways represent one of the most important dinosaur discoveries made in Britain for decades. Furthermore, they provide a rare snapshot of life during the Middle Jurassic.

An illustration of a typical sauropod from the Middle Jurassic (Cetiosaurus). It is thought that the Oxfordshire “dinosaur highway” was created by Cetiosaurus or sauropods similar to Cetiosaurus. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

One of the World’s Most Important Dinosaur Sites

At the time the tracks were made, much of Britain was covered by a shallow sea. The Oxfordshire area formed part of a shallow tropical landscape. Mudflats and lagoons provided ideal conditions for preserving footprints. Consequently, the tracks survived for millions of years beneath layers of sediment.

Scientists continue to investigate the quarry. Therefore, further discoveries may yet emerge from this extraordinary site.  However, it is not the only site where long trackways of sauropod dinosaurs have been discovered.

Commenting on the on-going research, Mike from Everything Dinosaur stated:

“The Dewars Farm Quarry site is remarkable. Scientists think there are more footprints awaiting discovery. Hopefully, the site’s owners will continue to work closely with the researchers as well as Natural England to ensure that these fossils are preserved.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Birmingham supplied in January 2025 in the compilation of this article.

The award-winning Everything Dinosaur website: Models of Dinosaurs.

Researchers have described a single dinosaur caudal vertebra (tail bone) from Denman Island (British Columbia, Canada).  It has been identified as an ornithomimosaur caudal vertebra. The fossil, thought to represent a bone from the middle part of the tail, is only the second dinosaur fossil identified from the Upper Cretaceous Nanaimo Group. In addition, it is the first definitive dinosaur fossil found in Canadian outcrops. Specifically, the caudal vertebra is from marine sediments of the Campanian-aged Cedar District Formation. The fossil discovery suggests that ostrich-like dinosaurs were present on the western margins of Laramidia.

A single dinosaur caudal vertebra similar to the fossil discovery. A tail bone ascribed to the Ornithomimosauria clade has been found in Upper Cretaceous deposits on Denman Island (British Columbia). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

A Dinosaur Caudal Vertebra

The discovery of the single caudal bone is only the second reported occurrence of dinosaur fossils from the Upper Cretaceous Nanaimo Group. In 2015, we reported a partial theropod femur from Sucia Island (Washington State, USA). Interestingly, this bone also derives from the Cedar District Formation, but it is geologically older than the ornithomimosaur tail bone.

• Partial theropod femur (Washington State, USA) – 83.6 to 79.8 mya
• Mid-caudal ornithomimosaur vertebra (Denman Island, British Columbia, Canada) – 79.8 to 75.5 mya

mya = millions of years ago.

To read our blog post from 2015 about the partial theropod femur fossil discovery: Washington State’s First Dinosaur.

The Upper Cretaceous Nanaimo Group

The deposits of the Upper Cretaceous Nanaimo Group of Vancouver Island have been studied for decades. Numerous vertebrate fossils have been collected representing a diverse marine biota. For example, fossils of fish including sharks, pterosaurs, elasmosaurids and birds have been found. However, despite intensive collecting no dinosaur fossils had been discovered.

Writing in the journal “FACETS” researchers, Victoria Arbour (Royal British Columbian Museum), Timon Bullard (École Secondaire Esquimalt High School) and David Evans (Royal Ontario Museum) describe an isolated theropod caudal vertebra. The fossil was found in marine sediments of the Campanian-aged Cedar District Formation of Denman Island. This small island is located off the eastern coast of the much larger Vancouver Island.

Contemporaneous with Judith River and Two Medicine Formation Biotas

The bone resembles the tail bones of ornithomimosaurs. However, the specimen cannot be identified at the family level. It was likely transported from the western margin of North America to the east. The Nanaimo Group was deposited at least 37o miles (600 km) south of its present position, and this ornithomimosaur likely lived at a similar palaeolatitude to contemporaneous dinosaur faunas in the Two Medicine and Judith River formations in the Western Interior.

Ornithomimosaurs were probably feathered.  In addition, they had long necks, small skulls and lengthy tails. Analysis of the long and graceful hindlimbs suggests that these dinosaurs were fast runners. The caudal vertebra found on Denman Island is likely to have come from the middle part of the animal’s tail.

The image (above) is that of the recently introduced CollectA Deluxe Gallimimus model.  It is a popular figure with collectors and dinosaur fans.  Furthermore, it is one of very few models representing ornithomimosaurs available.

To view the CollectA Deluxe range of prehistoric animal models: CollectA Deluxe Prehistoric Animals.

The scientific paper: “An ornithomimosaur from the Campanian Cedar District Formation (Nanaimo Group) of Denman Island, British Columbia, Canada” by Victoria M. Arbour, Timon S. Bullard and David C. Evans published in FACETS.

For models of ornithomimosaurs and other dinosaurs: Theropod Models and Dinosaur Toys.