The Diminutive Tyrannosaur Moros intrepidus

A small, but speedy dinosaur is the newest member of the Superfamily Tyrannosauroidea, a distant relative of the most famous dinosaur of all Tyrannosaurus rex.  T. rex et al might have a reputation for being giant, bone-crunching apex predators, but for much of their evolutionary history, the tyrannosaurs have been rather over-shadowed by other super-sized dinosaur carnivores.  Indeed, it was only in the last few million years of the Cretaceous that these types of theropod emerged as the apex predators of northern latitudes.  The new dinosaur, named Moros intrepidus, at approximately 78 kilograms (data range 53 to 85 kilograms), around the same bodyweight as a South American Jaguar (Panthera onca), is about ninety times lighter than its famous top-of-the-food-chain relative.

Moros intrepidus

Ironically, contrary to public opinion, M. intrepidus might just be more typical of the Tyrannosauroidea bauplan than its more famous relatives – Gorgosaurus, Albertosaurus and T. rex.

The Newly Described Moros intrepidus from the Late Cretaceous of Central Utah

Picture credit: Jorge Gonzalez

Teeth and a Hind Limb from a New Theropod Dinosaur

The fossilised remains of a partial right leg consisting of a femur, a tibia, metatarsal bones and some toe bones from the fourth toe were discovered in sediments representing the lower Mussentuchit Member of the Cedar Mountain Formation located in Emery County (Utah).  These fossils, in conjunction with isolated teeth from the front portion of the upper jaw (premaxilla) found nearby provide the basis for this new taxon.  The deposits represent a terrestrial environment, a large delta and they date from approximately 96 million years ago (Cenomanian faunal stage of the Late Cretaceous).

Moros intrepidus represents the oldest known Cretaceous-aged tyrannosauroid discovered to date in North America. It extends the definitive fossil record for these types of dinosaurs by around 15 million years.

The Temporal Relationships and Phylogeny of the Tyrannosauroidea

Picture credit: Nature Communications Biology

In the diagram (above), the section on the left (a), shows the fossil record gap between Late Jurassic tyrannosauroids and much larger Late Cretaceous members of the Tyrannosauridae family such as Lythronax (L. argestes).  Section (b) demonstrates the temporal range of these theropods and the change in bauplan, whilst (c) demonstrates key evolutionary anatomical changes.  The blue and pink coloured shapes in (d) reflect the transition from allosaur/megaraptoran dominated ecosystems to tyrannosaur dominated palaeoenvironments.

A Changing of the Guard When it Comes to Apex Predators

Palaeontologists know that the tyrannosaur lineage dates back a long way.  For example, basal tyrannosaurids such as Stokesosaurus (S. clevelandi) are known from Upper Jurassic deposits of Utah.  By the Late Cretaceous (Campanian faunal stage), tyrannosaurs were large and had become the iconic apex predators beloved by dinosaur fans and film directors.  The fossil record for North American tyrannosaurs was essentially blank, giving palaeontologists a T. rex skull-sized headache when it came to piecing together how these theropods changed over time.

The discovery of Moros helps to narrow a 70-million-year-gap in the fossil record of tyrant lizards in North America.

Lead-author of the study, published in “Nature Communications” Lindsay Zanno of the North Carolina Museum of Natural Sciences explained:

“When and how quickly tyrannosaurs went from wallflower to prom king has been vexing palaeontologists for a long time.  The only way to attack this problem was to get out there and find more data on these rare animals.”

A Silhouette of M. intrepidus Showing the Anatomical Position of the Known Fossil Material

Picture credit: Nature Communications Biology

Living in the Shadow of Siats meekerorum

In 2013, two of the authors of the Moros intrepidus paper, Lindsay Zanno and Peter Makovicky (Field Museum, Chicago), published a study on a large allosauroid from similar-aged sediments.  The dinosaur, named Siats meekerorum is estimated to have measured around 12 metres in length, dwarfing the contemporary Moros, which had a hip height of around 1.2 metres.  The researchers conclude that within a palaeoenvironment dominated by giant, allosauroid theropods, tyrannosaurs such as M. intrepidus relied on their speed and small size and would have kept out of the way of the larger predators.

A spokesperson from Everything Dinosaur commented:

“During the Cenomanian, tyrannosauroids like Moros intrepidus were secondary predators within an ecosystem dominated by apex predators from a completely different part of the theropod family tree.  For the greater part of the tyrannosaur evolutionary history, these types of dinosaurs were marginal predators, living in the shadow of much bigger carnivorous dinosaurs.”

A Life Reconstruction of Siats meekerorum with two Tyrannosauroids shown in the Foreground

Picture credit: Julio Laceardo

To read Everything Dinosaur’s article on the discovery of Siats meekerorum: Unravelling the Apex Predators of the Cretaceous Before Tyrannosaurs.

Phylogeny Points at Asian Ancestry

A study of the longer limb bones indicates that the individual was around six to seven years of age when it died.  It was likely to have reached its adult size.  A phylogenetic assessment indicates an affinity with Asian tyrannosaur taxa, in essence, the ancestors of famous North American dinosaurs such as Gorgosaurus and Tyrannosaurus rex migrated into North America from Asia.

Assistant Research Professor Zanno stated:

“T. rex and its famous contemporaries such as Triceratops may be among our most beloved cultural icons, but we owe their existence to their intrepid ancestors who migrated here from Asia at least 30 million years prior.  Moros signals the establishment of the iconic Late Cretaceous ecosystems of North America.”

Views of the Lower Leg Bones from the Right Leg of M. intrepidus

Picture credit: Nature Communications Biology

What’s in a Name?

The etymology of this new tyrannosauroid reflects the later faunal turnover that led to the apex predator roles in North America being dominated by tyrannosaurs.  The genus name is from the Greek “Moros”, the embodiment of impending doom, for the descendants of this fast-running dinosaur were to evolve into some of the largest and most formidable terrestrial predators known to science.  The species name is from the Latin “intrepidus”, a reference to these intrepid dinosaurs making the migration from Asia into North America and their subsequent dispersal.

Size is Not Everything

Although around ninety times lighter than Tyrannosaurus rex, Lindsay warns against underestimating the predatory abilities of Moros.

She added:

“Moros was lightweight and exceptionally fast.  These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator.  It could easily have run down prey, while avoiding confrontation with the top predators of the day.  Although the earliest Cretaceous tyrannosaurs were small, their predatory specialisations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous.  We now know it took them less than 15 million years to rise to power.”

The scientific paper: “Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record” by Lindsay E. Zanno, Ryan T. Tucker, Aurore Canoville, Haviv M. Avrahami, Terry A. Gates and Peter J. Makovicky published in Nature Communications Biology.

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Mnyamawamtuka moyowamkia – Heart-shaped Tail Bones Help to Flesh Out Titanosaur Evolution

Scientists writing in the on-line, open access journal PLOS One, have published details of a new species of African titanosaur.  It took several years to carefully remove the fossil material from a high cliff wall overlooking the Mtuka riverbed in south-western Tanzania, but the fossils, representing a not fully mature dinosaur, are providing palaeontologists with important information about how African ecosystems changed over the course of the Cretaceous.  The new titanosaur has been named Mnyamawamtuka moyowamkia (pronounced Mm-nya-ma-wah-mm-too-ka mm-oh-yo-wa-mm-key-ah).  The name is derived from Kiswahili for “animal of the Mtuka river with a heart-shaped tail”.

The heart-shaped tail element of the name refers to the strange shape of the most intact middle caudal vertebra described in the paper.  It bulges out at the sides (dorsolateral expansion of the posterior articular surface of the centrum), a unique tail bone morphology that resembles the shape of a romantic, love heart.

A Life Reconstruction of a Pair of  Mnyamawamtuka moyowamkia Titanosaurs

Picture credit: Mark Witton

Mnyamawamtuka moyowamkia

The first evidence of the dinosaur fossils was noted in 2004 and some fossils were excavated from the cliff face, in what were quite hazardous conditions, with field team members having to be lowered over the cliff on numerous occasions to work on the exposed bones.  Annual excavations took place until 2008, it was important to keep returning to the site as the fossils were in danger of being lost to the river in seasonal floods.

A Line Drawing of the Quarry Site Showing the Extent of the Annual Excavations

Picture credit: PLOS One

Around 110 -100 Million Years Old

The specimen was excavated from the Mtuka Member of the Cretaceous Galula Formation, which was deposited around 110 to 100 million years ago (Aptian to Cenomanian faunal stage of the Cretaceous).  A substantial portion of the postcranial skeleton has been recovered.

Dangerous Work!  The Excavation Site in 2007

Picture credit: Ohio University

Commenting on the importance of this discovery, in relation to the evolution of African titanosaurs, lead author of the paper, Dr Eric Gorscak, a recent PhD graduate of Ohio University and now an assistant professor at the Midwestern University (Illinois), stated:

“Although titanosaurs became one of the most successful dinosaur groups before the infamous mass extinction capping the Age of Dinosaurs, their early evolutionary history remains obscure, and Mnyamawamtuka helps tell those beginnings, especially for their African-side of the story.  The wealth of information from the skeleton indicates it was distantly related to other known African titanosaurs, except for some interesting similarities with another dinosaur, Malawisaurus, from just across the Tanzania–Malawi border.”

Adding to the Diversity of Titanosaurian Sauropods from Africa

The field team responsible for this discovery have also found the fossilised remains of two other titanosaurs in this part of Africa.  In 2017, Everything Dinosaur reported upon the discovery of Shingopana songwensis.

To read about S. songwensis: A New Species of African Titanosaur is Named.

In addition, Rukwatitan bisepultus another Titanosaurian sauropod dinosaur, was named and described in 2014: A New Species of Titanosaurian Sauropod Rukwatitan bisepultus.

The researchers conclude that Mnyamawamtuka moyowamkia was distantly related to both Shingopana songwensis and Rukwatitan bisepultus, fossils of which come from younger Cretaceous sediments, although it did share some anatomical characteristics with Malawisaurus dixeyi from Malawi, that might have been contemporaneous.  This new fossil discovery is helping palaeontologists to better understand the distribution of titanosaurs between Africa and South America and their evolutionary relationships.

Heart-shaped Tail Bones

One of the middle caudal centra (tail bone from the middle portion of the tail), exhibits a unique dorsolateral expansion of the posterior articular surface of the centrum.  This unique characteristic was found to be present in the most intact middle caudal vertebra described.  This unique shape inspired the dinosaur’s name.

Heart-shaped Tail Bone Centrum (Rear View)

Picture credit: PLOS One

Tail Bones of Different Titanosaurs Compared

Picture credit: PLOS One

The scientific paper: “A New African Titanosaurian Sauropod Dinosaur from the Middle Cretaceous Galula Formation (Mtuka Member), Rukwa Rift Basin, Southwestern Tanzania” by Eric Gorscak and Patrick M. O’Connor published in PLOS One.

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Gobiraptor minutus – The Diversity of the Oviraptoridae in the Late Cretaceous

A new species of oviraptorid dinosaur (Oviraptoridae family), has been described by an international team of scientists.  The little dinosaur was probably feathered and it possessed thickened jaws, an adaptation to feeding on hard food items such as seeds, nuts or the shells of bivalves, molluscs and crabs.  Animals that have a diet of hard items are referred to as durophagous.   

The fossilised remains of a single, very young individual were found in the Altan Uul area of Ömnögovi Province, Mongolia, in strata from the famous Upper Cretaceous Nemegt Formation.  The new species has been named Gobiraptor minutus and it helps to demonstrate that this part of Asia in the Late Cretaceous was home to diverse variety of oviraptorids, many of which, probably occupied specialist niches within the ecosystem in a bid to minimise competition for resources.

A Life Reconstruction of Gobiraptor minutus

Picture credit: Do Yoon Kim with additional annotation by Everything Dinosaur

Gobiraptor minutus – Rare for the Altan Uul Area of Southern Mongolia

Oviraptorid fossil specimens are relatively rare in the Altan Uul area of the Gobi Desert, however, within the Upper Cretaceous deposits exposed within the Gobi Desert, some ten oviraptorid taxa have so far been named and described.  Gobiraptor increases the diversity of oviraptorids known from the Nemegt Formation and demonstrates that these types of theropod dinosaurs were exceptionally abundant in the mesic environment* of that part of the world during the Late Cretaceous.

A mesic environment* – is a term used in ecology to describe an environment with a moderate amount of water.  Much of this part of Asia during the Late Cretaceous may be associated with a dry, arid environment, for example numerous types of other theropod fossils come from strata that represent almost desert-like conditions.  These fossils are found in the older Barun Goyot Formation which was laid down under more arid conditions.  The rocks in which the fossils of Gobiraptor were found consist mainly of river channel deposits, indicating that the palaeoenvironment changed and the environment became considerably wetter.

Thus, the finding of a new member of the Oviraptoridae family in the Nemegt Formation, which consists mostly of river and lake deposits, confirms that these dinosaurs were extremely well adapted to wet habitats.

Fragmentary Fossils and Skeletal Reconstruction of Gobiraptor minutus

Picture credit: PLOS One

Robust and Thickened Jaws Hint at a Dietary Specialism

Gobiraptor minutus, can be differentiated from other members of the Oviraptorosauria clade in having unusually robust and thickened jaws.  This unique mandibular morphology suggests that Gobiraptor was adapted to feeding on hard food items, it used its strong jaws to crush, indicating potential niche partitioning in the palaeoenvironment to reduce competition amongst small theropods and within the local population of oviraptorids.  Osteological analysis of the femur suggests that the fossil material represents a very young individual.

The phylogenetic analysis carried out by the researchers defines Gobiraptor as a derived oviraptorid closely related to three taxa from the Ganzhou region of southern China, but, ironically, the analysis suggests that it was rather distantly related to other Nemegt oviraptorids which, as the results of recent studies, are also not closely related to each other.

The authors propose that different dietary strategies may explain the wide taxonomic diversity and evolutionary success of this group of dinosaurs in this part of Asia.

Post-cranial Elements of G. minutus

Picture credit: PLOS One

The genus name honours the Gobi Desert, whilst the specific epithet is from the Latin for small, a reflection on the small size of the holotype.

The scientific paper: “A New Baby Oviraptorid Dinosaur (Dinosauria, Theropoda) from the Upper Cretaceous Nemegt Formation of Mongolia” by Sungjin Lee, Yuong-Nam Lee , Anusuya Chinsamy, Junchang Lü, Rinchen Barsbold and Khishigjav Tsogtbaatar published in PLOS One.

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Galagadon nordquistae – Shark Resident of Hell Creek

Perhaps the most famous exhibit at the Field Museum (Chicago), is the Tyrannosaurus rex specimen named “Sue”, the most complete T. rex fossil discovered to date.  A great deal of research has been carried out on the 66 million-year-old fossilised bones of this giant, meat-eating theropod that measures over twelve metres in length.  However, the matrix that surrounded the fossil material has helped to shed light on another resident of the famous Hell Creek Formation of South Dakota.  Fossil teeth found in the matrix surrounding the bones of the most famous T. rex in the world has led to the naming and description of a prehistoric shark that lived in freshwater, say hello to Galagadon nordquistae.

A Life Reconstruction of the Late Cretaceous Shark G. nordquistae

Picture credit: Velizar Simeonovski (Field Museum)

Galagadon nordquistae – A Small, Freshwater Predator

Ever since the preparation work on “Sue” began in the 1990s, the leftover sediment (matrix), was carefully stored at the Field Museum.  Researchers examined this material searching for micro-fossils in a bid to build up a picture of what life was like in this part of Laramidia towards the end of the age of dinosaurs.  Teeth were found from a shark which would have measured around half a metre in length.

Peter Makovicky (Curator of Dinosaurs at the Field Museum) commented:

“This shark lived at the same as Sue the T. rex, it was part of the same world.  Most of its body wasn’t preserved, because sharks’ skeletons are made of cartilage, but we were able to find its tiny fossilised teeth.”

The shark, named Galagadon nordquistae, is described in a scientific paper published in the “Journal of Palaeontology”.

Named After a 1980s Video Game

Lead author of the research, Terry Gates (North Carolina State University), explained that the shark’s name was inspired by the stepped, triangular shape of the teeth that reminded the research team of the spaceships in the 1980s video game Galaga.  The species epithet honours Field Museum volunteer Karen Nordquist who discovered the fossilised teeth in the matrix material.

Fossil Teeth Reminded the Scientists of Video Game Spaceships

Picture credit: Terry Gates (North Carolina State University)/Journal of Paleontology

Commentating on her fossil find, Nordquist stated:

“It [a tooth] was so tiny, you could miss it if you weren’t looking really carefully.  To the naked eye, it just looks like a little bump, you have to have a microscope to get a good view of it.”

Tiny Teeth Change our View of the Prehistoric Environment

The tiny teeth are only about a millimetre wide, about the size of a pinhead.  Galagadon was small too, estimated at around thirty to sixty centimetres in length.

Dr Makovicky added:

“Galagadon was less than two feet long, it’s not exactly Jaws.  It’s comparable to bamboo sharks living today.  It probably had a flat face and was very likely camouflage-coloured, since its relatives today have a camouflage pattern.  It would have eaten small invertebrates and probably spent a fair amount of time lying on the bottom of the riverbed.”

Galagadon may not have been huge, but its discovery has forced scientists into a re-think over what they thought they knew about the area where the T. rex named “Sue” was found.  It had been thought that the fossil locality represented a lake formed from a partially dried-up river, the presence of a shark suggests there must have been at least some connection to the sea.

Galagadon nordquistae – A Member of the Orectolobiformes

The shark has been classified as a member of the Orectolobiformes Order of sharks, making it distantly related to extant carpet sharks including bamboo sharks.  These types of shark are believed to have originated in the Jurassic and had a global distribution, today they are mostly restricted to waters in southeast Asia and Australia.

Co-author of the study, Eric Gorscak (Field Museum) explained:

“It’s surprising to find their fossils at the Sue locality.  During the Late Cretaceous, the continents continued to drift apart, further isolating dinosaurs and other land animals, and at the same time created the Atlantic and Indian oceans.  With occasional seaways connecting these young oceans, we have found fossils of marine life flourishing globally, including Galagadon and its relatives.”

Various Views of the Galagadon Teeth

Picture credit: Terry Gates (North Carolina State University)/Journal of Paleontology

Hell Creek – More than Flashy Dinosaurs

The study also reflects the importance of learning about fossils beyond big, flashy dinosaurs.  Each species discovered helps to build up a picture of the ecosystem in which the dinosaurs and other megafauna existed.

Karen Nordquist added:

“Most people, when they think of fossils, think of big huge dinosaur bones, but in the dirt, there are the bones of tiny animals.  When you get those bones and identify them, you get an idea of the whole environment, everything that lived with the big dinosaurs.  You learn so much from micro-sorting.”

The scientific paper: “New Sharks and Other Chondrichthyans from the Latest Maastrichtian (Late Cretaceous) of North America” by Terry A. Gates, Eric Gorscak and Peter J. Makovicky published in the Journal of Paleontology.

Everything Dinosaur acknowledges the help of a press release from the Field Museum (Chicago), in the compilation of this article.

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