A new species of tyrannosauroid described by scientists as a “missing link” sheds new light on the evolution of Late Cretaceous tyrannosaurs.  The dinosaur, named Khankhuuluu mongoliensis represents a transitional form between the small, gracile early tyrannosauroids and the giant, bone-crushing, apex predators such as Daspletosaurus and Tyrannosaurus rex.  The large tyrannosaurs from the end of the Cretaceous (Campanian and Maastrichtian) have been intensively studied.  However, the evolutionary origins of these super-sized theropods remains poorly understood.  It is known that these dinosaurs evolved from much smaller ancestors.  The discovery of Khankhuuluu (pronounced: khan-KOO-loo), helps palaeontologists to fill in a gap between these ancestral forms and the Late Cretaceous giants.

Khankhuuluu mongoliensis represents a transitional form between small tyrannosauroids of the early Late Cretaceous and the giants of Campanian and Maastrichtian. Yes, I know Maastrichtian is not correct in the diagram :). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Khankhuuluu mongoliensis

A team of researchers led by scientists from the University of Calgary (Alberta) have described a new species of tyrannosauroid from the Upper Cretaceous Bayanshiree Formation of southeastern Mongolia. University of Calgary PhD student Jared Voris found unique autapomorphies in two fossil specimens that had been assigned to the tyrannosauroid Alectrosaurus. For example, an air cavity was identified in the nasal bone and the student found other traits that indicate this dinosaur was evolving the skull anatomy that would generate immense bite forces.

Phylogenetic analysis suggests that K. mongoliensis sits just outside the Eutyrannosauria. This is the clade which contains giant tyrannosaurs such as Gorgosaurus, Lythronax, Tarbosaurus and T. rex as well as, smaller more lightly built predators.

The Eutyrannosauria is split into two tribes:

• Alioramini (for example Qianzhousaurus and Alioramus): smaller, slender, shallow-skulled forms.
• Tyrannosaurini (for example Tyrannosaurus rex): massive, deep-skulled forms.

Khankhuuluu and the Alioramini both share certain traits. They are lightly built, have long hind limbs and shallow skulls.  These characteristics are seen in juvenile specimens of the giant tyrannosaurs such as Tarbosaurus and T. rex. These traits evolved due to heterochrony, meaning changes in the timing of growth during evolution.  Writing in the journal “Nature” the research team which included Professor Darla Zelenitsky (University of Calgary) suggest that accelerated growth led to the evolution of the giant forms of tyrannosaur (peramorphosis). In contrast, the Alioramini retained juvenile traits into adulthood (paedomorphosis).  This explains, their smaller size and gracile build.

It is postulated that the different body types of the Alioramini and Tyrannosaurini likely helped them live side by side in Asia by filling different ecological roles.

The Prince of Dragons

The fossils were discovered in the 1970s at the Baishin-Tsav locality (Bayanshiree Formation). The strata are believed to have been laid down in the Turonian to Santonian faunal stages of the Late Cretaceous. The fossils of Khankhuuluu mongoliensis are thought to be approximately 86 million years old. Khankhuuluu is estimated to have weighed around 750 kilograms and measured around four metres in length.

The dinosaur’s name translates as “Mongolia’s Prince of Dragons”.  It hints that this theropod was a prince that led to the evolution of the “tyrant kings”.

The Everything Dinosaur blog has documented numerous articles about new discoveries leading to the erection of new Tyrannosauroidea taxa.  Most of these dinosaurs were considerably smaller than Khankhuuluu.

To read about the discovery of a small-bodied tyrannosauroid from southern Laramidia: Suskityrannus – The Shape of Things to Come.

The contemporary Timurlengia from Uzbekistan: New Dinosaur Sheds Light on How Tyrannosaurs Got Big.

Moros intrepidus, a member of the Superfamily Tyrannosauroidea from Utah: Moros – A Diminutive Tyrannosauroid.

Alioramini Not a Basal Lineage

Previously, phylogenetic analysis had relied too much on immature specimens, and this led to the assumption that the Alioramini were a primitive, early diverging group. However, the researchers postulate that the Alioramini were not basal, but more derived representing theropods that retained immature features into adulthood.

Furthermore, the study reveals that Asian tyrannosauroids (similar to Khankhuuluu) dispersed to North America. They gave rise to the Eutyrannosauria. The Eutyrannosauria diversified and remained exclusively in North America until a single dispersal to Asia in the latest Cretaceous that established the Alioramini and Tyrannosaurini tribes.

The scientific paper: “A new Mongolian tyrannosauroid and the evolution of Eutyrannosauria” by Jared T. Voris, Darla K. Zelenitsky, Yoshitsugu Kobayashi, Sean P. Modesto, François Therrien, Hiroki Tsutsumi, Tsogtbaatar Chinzorig and Khishigjav Tsogtbaatar published in Nature.

The Everything Dinosaur website: Dinosaur Models and Toys.

Scientists have revealed the last meal of an Australian herbivorous dinosaur that lived ninety-five million years ago.  Researchers writing in the journal “Current Biology” report on the discovery of Diamantinasaurus matildae stomach contents.  This remarkable discovery is the first time that sauropod stomach contents have been identified.  The analysis of the plant remains suggests bulk feeding and multi-level browsing.  The Diamantinasaurus nicknamed “Judy” was not fussy when it came to food.  Plants eaten by Diamantinasaurus include conifers, seed ferns and angiosperms. In addition to the fossilised stomach contents, the scientists also examined mineralised skin found with the specimen. This revealed a pattern of polygonal (often hexagonal) non-overlapping scales, a characteristic commonly seen in other sauropods.

A life reconstruction of the Australian titanosaur Diamantinasaurus matildae. Picture credit: Travis Tischler.

Picture credit: Travis Tischler

Diamantinasaurus matildae Stomach Contents

Sauropods were abundant and diverse throughout the Jurassic and Cretaceous.  The Sauropoda include the largest terrestrial animals known to science.  Studies of teeth suggest these dinosaurs were herbivorous.  However, our knowledge of their diet is based on indirect evidence such as coprolites (dung).  Furthermore, no fossilised gut contents (cololites) were known.  Intriguingly, this all changes with the publication of a remarkable study that describes Diamantinasaurus matildae stomach contents.

Subadult Diamantinasaurus matildae stomach contents. Undigested leaves can be clearly observed in the cololite. Picture credit: Australian Age of Dinosaurs.

Picture credit: Australian Age of Dinosaurs

The fossil material was collected from Winton Formation exposures (Queensland, Australia).  The cololite was located in the abdominal region and closely associated with a layer of mineralised skin.  Detailed analysis of the cololite reveals the plant material eaten.  Conifer pinnules, angiosperm leaves, and seed-fern fruiting bodies are preserved.  In addition, chemical biomarkers are identified consistent with angiosperms and gymnosperms.

This Diamantinasaurus matildae cololite provides the first direct, empirical evidence in sauropods of herbivory, demonstrating generalist feeding, low- to high-level browsing, and minimal oral processing of food.  It seems that these animals were not fussy what plant material they consumed.  They did not chew or grind up their food, relying on their enormous guts to digest the plant material.  Food may have persisted in their guts for a fortnight or more before being excreted.

Australian Age of Dinosaurs Collection Manager Mackenzie Enchelmaier (co-author of the study) highlighting the Diamantinasaurus gut contents. Picture credit: Australian Age of Dinosaurs.

Picture credit: Australian Age of Dinosaurs

The study marks the first use of molecular techniques to identify sauropod stomach contents.

Sauropods Feeding at a Range of Heights

The research was led by Dr Stephen Poropat (Curtin University, Perth, Western Australia).  The Diamantinasaurus specimen, originally found in 2017 has provided unprecedented detail on the feeding habits and diets of the Sauropoda.

The first direct, empirical evidence in sauropods of herbivory, demonstrating generalist feeding, low- to high-level browsing, and minimal oral processing of food. Picture credit: Australian Age of Dinosaurs.

Picture credit: Australian Age of Dinosaurs

To read Everything Dinosaur’s blog post from 2009 about the discovery of Diamantinasaurus: A Trio of New Dinosaurs from Australia.

Dr Poropat stated:

“The specific plants that they ate, and the height above ground at which they fed, have remained unknown – until now. The stomach contents we found belonged to a 12-metre-long, subadult sauropod that was still growing at the time of its death. Our findings show that at least some species of subadult sauropods were able to feed at a range of heights above ground level, and consequently were equipped to deal with environmental and vegetation changes throughout the Jurassic and Cretaceous periods.”

Co-author of the study, John Curtin Distinguished Professor Kliti Grice added:

“By using advanced organic geochemical techniques, we were able to confirm the presence of both angiosperms and gymnosperms in the diet of this sauropod. This unique approach provided molecular evidence of the plants that sauropods consumed.”

Mineralised Skin

Furthermore, this amazing titanosaur fossil specimen revealed details of its skin texture. The researchers identified a pattern of five-sided (often hexagonal), non-overlapping scales. This type of integumentary covering has been found in other sauropod specimens. The scales measure between seven and thirteen mm in diameter.   Each scale is covered in small bumps (papillae).  Their appearance is consistent with other known sauropod skin fossils.

Mineralised skin found with the Diamantinasaurus specimen known as Judy reveals polygonal (often hexagonal) scales. Picture credit: Australian Age of Dinosaurs.

Picture credit: Australian Age of Dinosaurs

The Diamantinasaurus matildae stomach contents and mineralised skin were preserved alongside yet-to-be-published body fossils of the subadult.  The fossils are housed at the Australian Age of Dinosaurs Museum. These fossils will form a key part of the Australia Through Time exhibition in the Museum’s future multi-million-dollar facility.

The longevity of the clade Sauropoda was underpinned by the persistence through time of generalist feeders like Diamantinasaurus matildae that were capable of feeding at a range of heights on a wide variety of different plant species.

Everything Dinosaur acknowledges the assistance of a media release from the Australian Age of Dinosaurs in the compilation of this article.

The scientific paper: “Fossilized gut contents elucidate the feeding habits of sauropod dinosaurs” by Stephen F. Poropat, Anne-Marie P. Tosolini, Samantha L. Beeston, Mackenzie J. Enchelmaier, Adele H. Pentland, Philip D. Mannion, Paul Upchurch, Karen Chin, Vera A. Korasidis, Phil R. Bell, Nathan J. Enriquez, Alex I. Holman, Luke M. Brosnan, Amy L. Elson, Madison Tripp, Alan G. Scarlett, Belinda Gode, Robert H. C. Madden, William D. A. Rickard, Joseph J. Bevitt, Travis R. Tischler, Tayla L. M. Croxford, Trish Sloan, David A. Elliott and Kliti Grice published in Current Biology.

For models and replicas of dinosaurs and other prehistoric animals: Dinosaur Models.

A newly published paper postulates that ungulate evolution has been shaped by two major ecological shifts. Tectonic shifts and global climate change have been the drivers of major biota turnover amongst large herbivorous mammals.

Ungulates are hoofed mammals.  This extremely diverse clade is subdivided into two orders, the Artiodactyla (even-toed) mammals that walk on two of their five toes and the Perissodactyla (odd-toed) mammals that walk on one or three toes. Molecular data led to a reclassification at the turn of the century with the establishment of a larger clade the Euungulata.

• Typical artiodactyls – ruminants such as cattle, goats, sheep, llamas, camels, hippos, giraffes, deer, pigs.
• Typical perissodactyls – rhinos, horses, tapirs.

It should be noted that the odd-toed ungulates were much more diverse in the past.  Brontotheres and knuckle-walking chalicotheres are extinct members of the Perissodactyla.

A wonderful prehistoric animal model. A 1:20 scale replica of the chalicothere Moropus – an extinct perissodactyl.

The picture above shows a typical chalicothere.  It is a 1:20 scale replica of Moropus from CollectA.  To view the range of CollectA scale prehistoric animal models: CollectA Deluxe Prehistoric Life.

Large Herbivores Shaping the Landscape

Large herbivores have shaped the Earth’s landscapes for the last forty million years.  A new study led by researchers from the University of Gothenburg in collaboration with scientists from Spain and the Museum für Naturkunde Berlin examines how these animals reacted to dramatic environmental changes.  The study, published in “Nature Communications” demonstrates that ecosystems managed to remain stable despite the extinction of many families.

Ungulates and other large mammals such as elephants are key ecosystem engineers.  The decline of large herbivores threatens entire habitats.  These large herbivores shape landscapes and promote biodiversity.  Current extinction rates, often referred to as the sixth mass extinction could lead to a loss of key taxa.

Dr Fernando Blanco, a visiting scientist at the Museum für Naturkunde Berlin led the research.  The fossils of over three thousand large herbivores from the past sixty million years to more recent times were studied.

Dr Blanco commented:

“We found that these ecosystems have remained surprisingly stable over long periods of time, even though species were added and others became extinct. Twice in the last sixty million years, however, the environmental pressure was so great that the entire system was globally reorganised.”

The End of the Tethys

The team discovered that the first major reorganisation of ecosystems took place around twenty-one million years ago.  This was during the Miocene Epoch.  The Tethys Sea closed and this created a landbridge between Eurasia and Africa.  A mass migration of species occurred. The ancestors of many extant ungulates moved into new habitats.  This had a profound effect on ungulate evolution.

A second major reorganisation of ecosystems occurred approximately ten million years ago.  This was during the Tortonian stage of the Miocene. Global cooling led to a massive reduction in forests and the spread of grasslands.  This led to a dramatic increase in grazing species and a gradual disappearance of many forest-dwelling species.  The researchers postulate that this was the beginning of a sustained decline in the functional diversity of large, herbivorous mammals.  This has led to a decrease in their influence over the planet’s ecosystems. Despite the extinctions, the researchers found that the basic ecological structure of herbivore communities remained remarkably stable.  Ecosystems remained stable even when many iconic taxa died out such as mastodons, mammoths and giant rhinoceroses.

A typical artiodactyl – a Cape buffalo (Syncerus caffer) photographed in Tanzania. Scientists reflect on ungulate evolution and the impact of large herbivores on the Earth’s ecosystems. Picture credit: Juan López Cantalapiedra.

Picture credit: Juan López Cantalapiedra

Co-author of the study, Dr Ignacio A. Lazagabaster from CENIEH (Centro National de Investigacion Sobre la Evolucion Humana, Spain) commented:

“It’s like a football team changing players during a game without the line-up changing significantly. New species came into play and the communities changed, but the new players fulfilled similar ecological tasks – as a result, the overall structure remained stable.”

The Resilience of Large Herbivores is Not Guaranteed

The research team remarks on the resilience of large mammals to survive glaciation, global cooling and other environmental crises.  However, many large taxa are extremely vulnerable today.

Fellow co-author of the study Dr Juan L. Cantalapiedra from the Spanish MNCN (Museo Nacional de Ciencias Naturales) stated:

“Our results show how enormously adaptable ecosystems can be. But there are limits. If we continue to lose species and their ecological roles on such a massive scale as in the present, we could soon reach a third global tipping point – and we humans are actively contributing to this.”

Everything Dinosaur acknowledges the assistance of the Museum für Naturkunde Berlin in the compilation of this article.

The scientific paper: “Two major ecological shifts shaped 60 million years of ungulate faunal evolution” by Fernando Blanco, Ignacio A. Lazagabaster, Óscar Sanisidro, Faysal Bibi, Nicola S. Heckeberg, María Ríos, Bastien Mennecart, María Teresa Alberdi, Jose Luis Prado, Juha Saarinen, Daniele Silvestro, Johannes Müller, Joaquín Calatayud and Juan L. Cantalapiedra published in Nature Communications.

For models of extinct mammals and other prehistoric animals: Prehistoric Animal Models and Toys.

Researchers have discovered the earliest evidence known to science of birds nesting in the Arctic.  A newly published study in the journal “Science” indicates that birds were nesting in polar regions during the Late Cretaceous.  Ancient Arctic birds nested alongside dinosaurs.  Fossils collected from the famous Prince Creek Formation of Alaska push back the record of Arctic nesting birds by up to thirty million years.

An illustration of Cretaceous Period birds with other dinosaurs from the same time period in the background. A paper in the journal Science documents the earliest-known example of birds nesting in the polar regions. A dromaeosaur feeds whilst Pachyrhinosaurus congregate in the background. Picture credit: Gabriel Ugueto.

Picture credit: Gabriel Ugueto

Ancient Arctic Birds

The University of Alaska Fairbanks led the research team.  However, researchers from the University of Reading were involved.  The scientists identified dozens of tiny fossil bones and teeth from the Alaskan excavation site.  Multiple types of birds were breeding in the Arctic. For example, diving birds that resembled loons, gull-like birds, and several kinds of birds similar to modern ducks and geese.  Analysis of the structure of the fossil material demonstrated that the bones represented very young birds such as hatchlings.

A hatchling bird beak, top left, and three foot bones are pictured to scale on a penny. The bones’ spongy texture tells scientists that they come from hatchlings, rather than adult birds. Picture credit: Pat Druckenmiller.

Picture credit: Pat Druckenmiller

The sediments are approximately seventy-three million years old (late Campanian faunal stage of the Cretaceous).

To read a blog post about dinosaurs nesting in the Arctic: Dinosaurs Nested in the Arctic.

Lead author of the study, Lauren Wilson, a doctoral student at Princeton University commented:

“Birds have existed for 150 million years. For half of the time they have existed, they have been nesting in the Arctic. Finding bird bones from the Cretaceous is already very rare. To find baby bird bones is almost unheard of. That is why these fossils are significant.”

More than Fifty Bird Fossils Found

Birds are key components in modern polar ecosystems.  Many species breed in these regions and spend all year either in the Arctic or Antarctic.  Although the Cretaceous polar regions were much warmer than today, they were still extreme, harsh environments.  Cretaceous polar regions would have experienced months of near total darkness.  They were challenging environments to colonise even though they were not as cold as they are today.  The fossil assemblage from the Prince Creek Formation suggests that chicks and adults of multiple species lived in the Arctic.  This suggests that birds began breeding in the Arctic early on in their evolution.

Prior to this research, the earliest known evidence of birds breeding in the polar regions dates to approximately forty-seven million years ago.  This was during the Eocene Epoch. The fossil material used in this study was collected from Prince Creek Formation exposures along the Colville River. Rather than focusing on large bones, the scientists collected every bone and tooth they could find from screen washes. Screen washing involves taking tubs of sediment and screening the sediments using sieves.  Once the majority of the stones and pebbles have been removed the remaining material is examined under a microscope.  In this way, tiny fossils including those of hatchling birds can be identified.

Joe Keeney, Patrick Druckenmiller and Jim Baichtal excavate at a site on the Colville River. Picture credit: Lauren Wilson.

Picture credit: Lauren Wilson

Evidence of Neornithes

Some of the tiny bones have skeletal features only found in Neornithes, the group that includes all extant birds. Like extant birds, some of these ancient species had no true teeth.

Co-author of the study, Dr Jacob Gardner (University of Reading) commented:

“Determining the identity of fossils using separate individual bones is notoriously difficult. For the first time, we determined the identities of large numbers of fossils using high-resolution scans and the latest computer tools, revealing an enormous diversity of birds in this ancient Arctic ecosystem. Polar bird communities have deeper evolutionary roots than previously imagined.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Reading in the compilation of this article.

The scientific paper: “Arctic bird nesting traces back to the Cretaceous” by Wilson, L. N., Ksepka, D. T., Wilson, J. P., Gardner, J. D., Erickson, G. M., Brinkman, D., Brown, C. M., Eberle, J. J., Organ, C. L. and Druckenmiller, P. S. published in the journal Science.

For models and replicas of prehistoric animals: Dinosaur and Prehistoric Animal Models.

Newly published research suggests that Allosaurus europaeus is not a valid taxon. A detailed study of Portuguese fossil material has led to the conclusion that the A. europaeus holotype (ML 415) represents Allosaurus fragilis.

The remains of large theropods ascribed to the Allosaurus genus have been found in Portugal. In 1988, fossils of a meat-eating dinosaur were discovered near the village of Andrés, (Leiria District, Portugal). Additional fossil finds from the coast at Praia de Vale Frades, (Lourinhã, Portugal) and a coal mine in the district of Leiria were assigned to Allosaurus. Subsequently, a European Allosaurus was erected in 2006 (Mateus et al). This dinosaur was named Allosaurus europaeus.  However, a detailed analysis of cranial material has led researchers to conclude that fossils attributed to A. europaeus should be bracketed as Allosaurus fragilis.

A life-size replica of an Allosaurus. The genus was first erected in 1877 (Marsh). Several species have been named but the validity of many of these species has been challenged. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The Demise of Allosaurus europaeus

Allosaurus fragilis was first described in the Upper Jurassic of Portugal in 1999 based on a set of postcranial remains collected at the Andrés fossil site in Pombal. The description of a second species, Allosaurus europaeus, based on elements from the back of the skull and a sequence of tail bones (ML 415) collected at Praia de Vale Frades in Lourinhã was controversial.  The scientists provide a detailed description of a new sample of skull fossil material.  These fossils from the village of Andrés are confidentially assigned to the Allosaurus genus.

In addition to the fossil study a comprehensive phylogenetic assessment of the Morrison Formation fossil record of Allosaurus was performed. The phylogenetic analysis indicates that there were only two valid Allosaurus species present in the Late Jurassic ecosystems of North America.  These species are Allosaurus fragilis and the recently erected Allosaurus jimmadseni.

To read Everything Dinosaur’s blog post about the establishment of A. jimmadseni as a separate species: A New Species of Allosaurus.

Manufacturers of prehistoric animal models were quick to introduce replicas of this new Allosaurus species.  Allosaurus jimmadseni was erected in 2020.  The American company Creative Beast Studios introduced an articulated replica of A. jimmadseni.

This figure has proved popular with collectors, especially collectors based in the USA.

To view the range of Beasts of the Mesozoic/Cenozoic figures: Beasts of the Mesozoic Figures.

The new Beasts of the Mesozoic Cyberzoic figure (A. jimmadseni) is one of the highlights of the latest customer newsletter. Shortly, after this new species was erected, new Allosaurus models came onto the market. Picture credit: Everything Dinosaur.

Referring Specimens to Allosaurus fragilis

The authors of the paper postulate that their analysis indicates that only two valid Allosaurus species were present in the Late Jurassic ecosystems of North America.  These two species are Allosaurus fragilis and Allosaurus jimmadseni.  The researchers provide an updated reference for Allosaurus classification.  The Portuguese specimens MNHN/UL.AND.#, ML 415, and MG 27804 are interpreted as belonging to A. fragilis.

This new research helps palaeontologists to better understand the evolution of theropods associated with the Lusitanian Basin.  The researchers consider that this study provides evidence of a close biogeographical relationship between North America and Europe during the Late Jurassic.

The scientific paper: “Cranial osteology of a new specimen of Allosaurus Marsh, 1877 (Theropoda: Allosauridae) from the Upper Jurassic of Portugal and a specimen-level phylogenetic analysis of Allosaurus” by Elisabete Malafaia, Pedro Dantas, Fernando Escaso, Pedro Mocho and Francisco Ortega published in the Zoological Journal of the Linnean Society.

The Everything Dinosaur website: Dinosaur Models.

Researchers have identified fossil tracks with skin impressions of early synapsids from the famous Bromacker fossil site in Thuringia (Germany).  These are the oldest skin impressions of early mammalian relatives known.  They provide unique insights into the evolution of scales and integumentary coverings within an Early Permian ecosystem.  The Bromacker quarry exposes 290-million-year-old deposits associated with the Tambach Formation. This rare site preserves exquisite, articulated fossils of a unique vertebrate fauna.  This quarry has been at the centre of a long research project, lasting decades led by the Museum für Naturkunde Berlin.

290-million-year-old skin impression fossils. Picture credit: Lorenzo Marchetti.

Picture credit: Lorenzo Marchetti

Studying the Trace Fossils of Early Synapsids

The fossil tracks were discovered over a century ago. These rare fossils were re-examined as part of the ongoing Bromacker research project.  This research project is run by the Federal Ministry of Research, Technology and Space.  The scientific paper has been published in the journal “Current Biology”.

Senior author of the study, Professor Jörg Fröbisch commented:

“It has been shown time and again that certain characteristics and traits of modern vertebrates, such as skin structure, lifestyle or social behaviour, appeared earlier in the course of evolutionary history than was initially assumed. The study once again demonstrates the globally unique significance of the fossil deposit at Bromacker and its enormous potential for future research.”

To read a blog post about a Dimetrodon fossil found at the Bromacker locality: Fossil Mystery is Solved.

Scales on the Underside, Legs and the Tail

One trackway preserved at the site is particularly illuminating. An impression preserved in the fine-grained Tambach sandstone reveals skin folds on the toes and various types of scales on the upper and lower legs.  There are also scale impressions from the ventral portion of the tail, the hip area and the abdomen.  The scientists have identified this as a resting track or evidence of a Permian vertebrate wallowing.

The arrangement and shape of the scale marks, sometimes diamond-shaped, rectangular, pentagonal to polygonal, sometimes overlapping like roof tiles, is reminiscent of the horny scales of membranous reptiles.

Evidence of Social Behaviour in Early Synapsids

A number of sandstone slabs preserve large numbers of tracks.  Several tracks are adjacent to each other, and some tracks are parallel.  The researchers suggest this is evidence of animals of the same species walking together.  The track producers, early synapsids such as Dimetrodon teutonis, probably rested, basked and cooled down together.  This suggests that these Permian animals demonstrated group behaviours, just like modern lizards, birds and mammals.

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

The scientific paper: “Early Permian synapsid impressions illuminate the origin of epidermal scales and aggregation behaviour” by Marchetti, L., Logghe, A., Buchwitz, M., and Fröbisch, J. published in Current Biology.

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

Newly published research in the journal “Nature” postulates that reptiles originated forty million years earlier than previously thought.  Fossil tracks (trace fossils) created by a small tetrapod with clawed feet, most probably a reptile, from the Snowy Plains Formation of Victoria, Taungurung Country significantly changes our view on the timeline of early amniote evolution.

The known fossil record of crown-group amniotes (the group that includes mammals, birds and reptiles), begins in the Late Carboniferous with sauropsid trace fossils and the body fossils of Hylonomus. The earliest body fossils of crown-group tetrapods are mid-Carboniferous, and the oldest trackways are Early Carboniferous.  Based on this evidence, it had been thought that the tetrapod crown group originated in the earliest Carboniferous (early Tournaisian), with the amniote crown group appearing in the early part of the Late Carboniferous.  This new fossil discovery challenges this view.

Flinders University Professor John Long and colleagues identified the fossilised tracks of an amniote with clawed feet.  The slab containing the fossil tracks is around 350 million years old.

Professor Long commented:

“Once we identified this, we realised this is the oldest evidence in the world of reptile-like animals walking around on land, and it pushes their evolution back by 35-to-40 million years older than the previous records in the Northern Hemisphere.”

Professor Long and his co-workers think the tracks were made by a small, lizard-like creature.

A reconstruction of an early amniote. The researchers believe the tracks were produced by an early reptile. This suggests that reptiles evolved some 40 million years earlier than previously thought. Picture credit: Martin Ambrozik.

Picture credit: Martin Ambrozik

Early Amniote Evolution

This discovery indicates that the first amniotes probably evolved in the Southern Hemisphere.  They may have evolved on the ancient supercontinent Gondwana.  Amniotes are vertebrates that undergo an embryonic developmental stage within an amnion. An amnion is a thin membrane that encloses the embryo and immerses the developing foetus in fluid. In simple terms, the amnion provides an environment in which the foetus can develop. In contrast, the eggs of amphibians do not have an amnion. They are dependent on a source of water in their environment in which to raise their young.

Professor Young added that the implications of this discovery for the early evolution of tetrapods are profound. All stem-tetrapod and stem-amniote lineages must have originated during the Devonian. It seems that tetrapod evolution proceeded much faster, and the Devonian tetrapod record is much less complete, than has been thought.

He explained:

“All stem-tetrapod and stem-amniote lineages must have originated during the Devonian period – but tetrapod evolution proceeded much faster, and the Devonian tetrapod record is much less complete than we have believed.”

Much remains uncertain regarding the evolution of early tetrapods and the rise of the amniotes. Scientists think that global warming may have led to the gradual dominance of the Reptilia and the demise of amphibians and their close relatives.

A dramatic change in climate may have aided the rise of the reptiles: Global Climate Change May Have Helped Reptile Evolution.

New Fossil Evidence

This new fossil evidence from Australia falsifies the previous, widely accepted timeline.  For Professor Long, his involvement with this amazing research goes back some forty-five years.  He did his PhD thesis on the fossils of the Mansfield district.  However, it was only recently after organising palaeontology field trips with Flinders University students that locals joined the hunt for fossils.

Two locals, Craig Eury and John Eason (co-authors of the study), found the slab covered in trackways.  At first, it was thought this trace fossil represented amphibian tracks.  However, a closer examination revealed that one track has a hooked claw coming off the digits, evidence for a reptile-like animal.

Searching for fossils in the Mansfield district of northern Victoria. Picture credit: Flinders University.

Picture credit: Flinders University

Crystal Clear Trackways

The trackways are preserved in astonishing detail. Dr Alice Clement (Flinders University and co-author), helped scan the fossil tracks to create digital models that could be analysed in detail.  Scientists from Uppsala University (Sweden) led by Professor Per Erik Ahlberg collaborated in this research. Digital heat maps were produced highlighting the depth and the topography of individual prints.

Dr Clement stated:

“We study rocks and fossils of the Carboniferous and Devonian age with specific interest to observe the very important fish-tetrapod transition. We’re trying to tease apart the details of how the bodies and lifestyles of these animals changed, as they moved from being fish that lived in water, to becoming tetrapods that moved about on land.”

Dr Aaron Camens (Flinders University), an expert in early tetrapod and amniote trackways explained that trackways record behaviour and tell scientists a lot about the animal’s locomotion.

He commented:

“A skeleton can tell us only so much about what an animal could do, but a trackway actually records its behaviour and tells us how this animal was moving.”

As Professor Long has been studying fossils from the Mansfield district since 1980, the team had a clear idea of the age of the rock deposits.  He has produced an extensive catalogue of fish fossils from the Mansfield district.  These fossils could then be compared with other fossil sites, with accurately dated rocks from around the world.  This location has produced some amazing fish fossils.  However, the quest had always been to find evidence of land animals (tetrapods).

Revising the Timeline of Early Amniote Evolution

The Mansfield district trace fossil slab dates from the Early Carboniferous (Tournaisian faunal stage).  Ironically, it was a comparison of fish fossils that permitted the team to calculate the age of the specimen to within ten million years.  This ground-breaking research has permitted the team to re-write the timeline of early amniote evolution. They conclude that these fossilised tracks show reptile-like animals appeared on Earth up to forty million years earlier than previously thought.

Revised timescale of early tetrapod evolution. Stratigraphic timescale representation of the Devonian and Carboniferous, showing the impact of the Snowy Plains Formation sauropsid tracks. The track record is shown as a pink rectangle, of double height to indicate possible age range. Picture credit: Long et al.

Picture credit: Long et al

Everything Dinosaur acknowledges the assistance of a media release from Flinders University in the compilation of this article.

The scientific paper: “Earliest amniote tracks recalibrate the timeline of tetrapod evolution” by John A. Long, Grzegorz Niedźwiedzki, Jillian Garvey, Alice M. Clement, Aaron B. Camens, Craig A. Eury, John Eason and Per E. Ahlberg published in the journal Nature.

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A new species of rinconsaurian titanosaur has been named based on fossils unearthed in northern Patagonia.  The dinosaur has been named Chadititan calvoi. The Rinconsauria clade comprises Late Cretaceous, relatively small and gracile Argentinian titanosaurs. Its composition remains disputed. Phylogenetic analyses reveal contrasting results depending on statistical parameters, but some academics have proposed as many as twenty taxa within this clade.

The fossil material, representing several individuals comes from outcrops of the Anacleto Formation. This formation is thought to have been laid down in the early to middle Campanian faunal stage of the Cretaceous.  The bedding plane associated with these fossils suggests that this dinosaur lived around seventy-eight million years ago.

Chadititan calvoi

The genus name is derived from the local dialect meaning “salt”. The type locality is an extensive salt flat. The species name honours the Argentine palaeontologist Jorge O. Calvo who first proposed the Rinconsauria clade.  Although known from fragmentary remains, palaeontologists have been able to estimate the size of this herbivore.  The partial femora (thigh bones), were compared to more complete Bonatitan (B. reigi) limb bones.  Chadititan is estimated to have been around seven metres long.

A scale drawing of the rinconsaurian titanosaur from northern Patagonia Chadititan calvoi. This dinosaur is estimated to have been about seven metres in length. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The Rinconsauria was erected in 2007.  The clade consists of slender relatively small titanosaurs with long limbs and modified pelvic girdles.  As far as we at Everything Dinosaur are aware, no osteoderms have been found in association with rinconsaurian fossils.  Dermal armour could have been absent in this clade of titanosaurs.

A Diverse Fossil Assemblage Dominated by Freshwater Turtles

The fossils were found at a location owned by the Marin family near General Roca city (Rio Negro province).  The authors of the scientific paper report a new assemblage of fossils representing a diverse biota.  The site could represent an oasis in what was an exceptionally arid environment.  Gastropods, lungfishes, freshwater turtles and crocodilian fossils have been found.

Turtle fossils are the most common vertebrate fossils present.  They represent over ninety percent of the recovered material.

The scientific paper: “New fossiliferous locality from the Anacleto Formation (Late Cretaceous, Campanian) from northern Patagonia, with the description of a new titanosaur” by Agnolín, Federico L.; Motta, Matías J.; Garcia Marsà, Jordi; Aranciaga-Rolando et al. Paper published – Revista del Museo Argentino de Ciencias Naturales.

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The direct ancestor of the iconic Tyrannosaurus rex came from Asia. Newly published research lends weight to the theory that the direct ancestor of Tyrannosaurus rex dispersed into North America from Asia via an ancient land bridge. Fossils of T. rex are known from Canada and the USA. However, there is some evidence to suggest that this super-predator may also have roamed what is now Mexico.  The origins of this famous dinosaur, more specifically the Tyrannosaurini, have been hotly debated.

Did the ancestors of T. rex come from Asia or did its ancestors evolve in North America (southern Laramidia)?

The spectacular Titus the T. rex exhibit at Wollaton Hall. A newly published study (May 2025) supports the theory that the ancestors of the iconic Tyrannosaurus rex originated in Asia. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The Origins of the Iconic Tyrannosaurus rex

Previous studies had suggested that the ancestors of the iconic Tyrannosaurus rex migrated into North America from Asia. This theory was primarily based on the closer taxonomic relationship that T. rex has with Asian tyrannosaurids such as Zhuchengtyrannus and Tarbosaurus. Tyrannosaurus rex was more distantly related to Laramidian tyrannosaurids such as Daspletosaurus and Teratophoneus. So, based on this evidence, it was thought that the lineage of tyrannosaurs that were direct ancestors of the “Tyrant Lizard King” probably evolved in Asia.

Dalman et al in their scientific description of Tyrannosaurus mcraeensis (2024) proposed that the Tyrannosaurus genus evolved in southern Laramidia. Their theory was underpinned by the Late Campanian–Early Maastrichtian age of the T. mcraeensis holotype. However, doubt has been cast over the exact age of the holotype fossil material.

In this new study, a biogeographical analysis of the Tyrannosauridae family, particularly the tribe Tyrannosaurini suggests that tyrannosaurines diversified in the Late Campanian. This diversification supports the idea of a migration of ancestors of T. rex from Asia into North America.

To read Everything Dinosaur’s blog post about Tyrannosaurus mcraeensis: A New Tyrannosaurus Species is Described.

Tyrannosaurus Genus Likely Endemic to North America

The research team conclude that Tyrannosaurus is likely an endemic, North American genus.  The ancestor of the genus dispersed into North American biotas, where it would give rise to Tyrannosaurus. In addition, gigantism occurred numerous times within the Tyrannosauroidea. It was potentially driven by cooler or cooling climates. This study supports the idea that evolutionary changes within the Dinosauria of the Late Cretaceous was partly in response to climate change. The research illustrates the importance of using climate and ecological data to better understand dinosaurian evolution within wider global climatic shifts.

Shedding Light on the Enigmatic Megaraptoridae

The study also sheds light on the evolution of the enigmatic megaraptors.  The Megaraptoridae are a different family of theropod dinosaurs.  How closely related they were to the tyrannosaurs remains disputed.

Some megaraptors were giants.  They occupied the apex predator niche within many ecosystems.  For example, Maip macrothorax from the Late Cretaceous of Argentina may have measured in excess of ten metres long.  Whilst the Tyrannosaurini evolved massive skulls and powerful jaws to take down prey.  Megaraptorids such as Maip evolved in a different direction.  These predators had powerful forelimbs and grasping digits tipped with huge claws.

The new for 2025 CollectA Deluxe M. macrothorax figure shown in lateral view.

The picture (above) shows a 1:40 scale model of Maip macrothorax.  It is part of the CollectA Deluxe range of prehistoric animal figures.

To view the CollectA Deluxe range of models: CollectA Deluxe Prehistoric Animal Models.

Although the extremely fragmentary nature of the megaraptorid was a limiting factor in this research, the team postulate that the megaraptors most likely diverged from the tyrannosaurs around 170 million years ago in Asia.  The megaraptors spread south into what is now Australia, South America and Antarctica via Europe and Africa.

Megaraptorids evolved into the top predators in areas such as Patagonia and Australia, but elsewhere in the world, such as Asia they were replaced by tyrannosaurs.

The scientists would like to extend their modelling but to do so more early tyrannosaur and megaraptor fossils would be needed to make any analysis robust.

The scientific paper: “Rise of the king: Gondwanan origins and evolution of megaraptoran dinosaurs” by Cassius Morrison, Charlie Roger Scherer, Ezekiel V. O’Callaghan, Collin Layton, Colin Boisvert, Mauro Aranciaga Rolando, Leroy Durrant, Pedro Salas, Steven J. R. Allain and Samuel J. L. Gascoigne published by Royal Society Open Science.

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Numerous bonebeds associated with horned dinosaurs are known.  For example, the remains of hundreds of Pachyrhinosaurus lakustai have been excavated from a single site in Alberta, Canada. Fossil sites such as this provide evidence that many horned dinosaurs lived in herds. However, until recently there was very little evidence to support the idea of a herd of Triceratops.  That the most famous horned dinosaur “three horned face” formed large, social groups.

To read about the excavation of a Pachyrhinosaurus skull from a bonebed: Remarkable Horned Dinosaur Skull Excavated from Bonebed.

Researchers from the Naturalis Biodiversity Centre (Leiden, Netherlands) have helped to change our view of Triceratops.  They have identified the remains of a least five individuals that lived and died together.  A decade of careful study of a dinosaur bonebed discovered in Wyoming has revealed that Triceratops too moved around in groups.

An artist’s reconstruction of a herd of Triceratops dinosaurs. Picture credit: Bart Bus.

Picture credit: Bart Bus

A Fossil Site Reviews a Herd of Triceratops

Ironically, the field team set out to find a T. rex. Nonetheless, what they found in the summer of 2013 has proved to be of much greater value to science than a single theropod specimen.  The research work at the Lance Formation (Maastrichtian) exposures has revealed a large bonebed of Triceratops (T. horridus). Over the last decade, some twelve hundred individual bones have been excavated from the site. Importantly, the abundant postcranial material displays features of both subadult and adults. This fossil locality can shed new light on the ontogeny and possible gregarious behaviour of this iconic dinosaur.

Field team member Jimmy de Rooij digging up a Triceratops fossil. Picture credit: Marten van Dijl (Naturalis Biodiversity Centre).

Picture credit: Marten van Dijl (Naturalis Biodiversity Centre)

A team of palaeontologists and volunteers spent many summers at the site mapping and extracting the precious bones.  One of the researchers Jimmy de Rooij hopes to receive a PhD from Utrecht University for his work on this remarkable bonebed.

He commented:

“The material is of very god quality.  This enabled us to show that these Triceratops grew really slowly for instance.”

It is thought that all these dinosaurs perished together, perhaps mired in a swamp.  The fossils are all contained in a thin layer, without the bones of other species present.

Jimmy de Rooij holding a Triceratops horn. Picture credit: Naturalis Biodiversity Centre.

Picture credit: Naturalis Biodiversity Centre

Publishing Scientific Papers and Opening an Exhibition

A scientific paper outlining the fossil discoveries and postulating that this was strong evidence to indicate that Triceratops horridus was gregarious was published in 2019.  However, the research into this treasure trove of horned dinosaur bones continues today.  An exhibition telling the story of the Wyoming bonebed and its significance to palaeontology has opened at the Naturalis Biodiversity Centre.

A sixth Triceratops specimen on display at the Naturalis Biodiversity Centre. Picture credit: Naturalis Biodiversity Centre.

Picture credit: Naturalis Biodiversity Centre

Study of the physical and chemical properties of hundreds of individual bones indicates that Triceratops migrated.  All five Triceratops specimens exhibit the same characteristics.  In other words, this iconic dinosaur species moved around in groups, at least for part of the time.  Visitors to Wyoming at the end of the Cretaceous might have spotted a herd of Triceratops!

A Herd of Triceratops horridus

The CollectA T. horridus ceratopsian figure in right lateral view. This Triceratops dinosaur model has an articulated lower jaw. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The image (above) shows a 1:40 scale model of Triceratops horridus.  This is the biggest Triceratops species described to date and one of the largest ceratopsids known to science.  The replica is from the CollectA Deluxe range of scale prehistoric animal figures.

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

The discovery of what potentially could be a small herd of Triceratops poses some intriguingly questions.  For example, did these herbivores indulge in complex social behaviours?

Professor Anne Schulp (Naturalis Biodiversity Centre/Utrecht University), and De Rooij’s PhD supervisor proudly stated:

“Naturalis, the national natural history museum of the Netherlands, now has the biggest Triceratops find in the world, and Utrecht University has the first Dr Triceratops in the Netherlands. De Rooij’s work didn’t just result in research papers, but also in an exhibition about his findings.”

Mike from Everything Dinosaur commented:

“The exhibition will give dinosaur fans young and old the chance to learn more about Triceratops.  Indeed, visitors will be able to see the five fossil Triceratops specimens together some sixty-seven million years after they lived and died together.”

Visit the Everything Dinosaur website, which is award-winning and customer-friendly: Dinosaur Models and Prehistoric Animal Figures.

Everything Dinosaur acknowledges the assistance of a media release from the Naturalis Biodiversity Centre in the compilation of this article.