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.