When asked to name an armoured dinosaur, we suspect that most readers would quickly reply with “Stegosaurus” or possibly “Ankylosaurus”. True, some armoured dinosaurs are very famous, having seeped into the public consciousness thanks to countless appearances in the media, dinosaur documentaries and films. However, very little is known about the origins of this diverse and highly successful ornithischian clade. Newly, published research on the labrador-sized early thyreophoran Scutellosaurus (S. lawleri) is helping scientists to better understand the evolutionary origin of these dinosaurs.

A Palaeontological Project Lasting Sixteen Years

The scientific paper, the first detailed anatomical assessment of Scutellosaurus covering its entire skeleton, has been published in the on-line, open access journal Royal Society Publishing. The dedicated research team consisted of PhD student Benjamin Breeden (University of Utah), Professor Richard Butler (University of Birmingham), Professor Timothy Rowe (University of Texas at Austin) along with PhD student Tom Raven and Dr Susannah Maidment (Natural History Museum, London).

This research project was first proposed back in 2005. Sixteen years after the project’s inception, the paper has been published providing a new perspective on the evolution of the armoured dinosaurs.

Scutellosaurus lawleri

Named and described in 1981, from material discovered ten years earlier. Scutellosaurus lawleri fossils come from the Kayenta Formation of Arizona, more specifically mudstones associated with the “middle third” of this Formation (Lower Jurassic). It has been estimated that the Scutellosaurus fossils are around 181 to 186 million years old (Pliensbachian and Toarcian stages).

More than seventy Scutellosaurus specimens are known, representing all parts of the skeleton. As such, Scutellosaurus fossil material is much more abundant than that of other early armoured dinosaurs such as Scelidosaurus (S. harrisoni), which was named and described by the famous Victorian anatomist Richard Owen. This relative abundance of fossil material in comparison with other early armoured dinosaurs makes Scutellosaurus an ideal candidate to help palaeontologists to better understand the evolution of this important group of plant-eating dinosaurs.

Scutellosaurus was a Biped

One of the key findings of this research is that based on limb proportions and postcranial skeletal assessments, Scutellosaurus was bipedal. As such, it is the only bipedal thyreophoran known to science. It had been suggested that as thyreophorans evolved into larger and more heavily armoured forms they lost this ability to adopt a bipedal posture.

Although the exact layout of the dermal armour of Scutellosaurus is not known, the researchers tested the hypothesis that heavier armour led these dinosaurs to adopt a quadrupedal stance. The research team calculated the centre of mass of Scutellosaurus with its armour, without armour, with the armour of Stegosaurus and with the armour of the Late Cretaceous ankylosaurid Euoplocephalus. They found that the addition of armour did cause the centre of mass to move slightly further back in the body in all the tests. However, the team concluded that the evolution of armour probably was not the reason to cause early armoured dinosaurs to adopt quadrupedal locomotion. More derived taxa of armoured dinosaurs required forelimb support for their body weight for other, as yet not understood reasons.

Armoured Dinosaurs Grew Slowly

Detailed analysis of Scutellosaurus bones indicate that this dinosaur grew very slowly throughout its life. This supports other studies that suggest that thyreophorans had lower metabolic rates when compared to other dinosaurs, even closely related ornithischians.

Lots of Variety in Early Jurassic Dinosaur Faunas

The supercontinent Pangaea did begin to break-up during the Jurassic, but at the time Scutellosaurus roamed what was to become the western United States, this landmass was largely intact, which in theory would have helped homologous populations of dinosaurs to evolve. That is to say, that given the absence of any geographical barriers preventing movement, similar dinosaur faunas would have existed across Pangaea. When this study of Scutellosaurus is looked at from the wider perspective of dinosaur evolution and radiation, a different picture emerges.

The ornithischian dinosaurs from the Kayenta Formation are represented by Scutellosaurus lawleri, a larger unnamed thyreophoran known from isolated bones and an undescribed hetrodontosaurid. Scutellosaurus fossils are the most abundant dinosaur fossils associated with the Kayenta Formation, they are much more common than theropod or sauropodomorph fossils. In contrast, the roughly contemporaneous upper Elliot Formation of South Africa has many more sauropodomorphs than ornithischians and the dinosaur biota of the Lufeng Formation of China is dominated by sauropodomorphs with ornithischian material exceptionally rare.

This suggests that there was considerable variation in the composition of dinosaur biotas during the Early Jurassic.

The scientific paper: The anatomy and palaeobiology of the early armoured dinosaur Scutellosaurus lawleri (Ornithischia: Thyreophora) from the Kayenta Formation (Lower Jurassic) of Arizona by Benjamin T. Breeden, Thomas J. Raven, Richard J. Butler, Timothy B. Rowe and Susannah C. R. Maidment published by Royal Society Publishing.

Analysis of sediments taken from the famous Prince Creek Formation of northern Alaska has revealed tiny, fossilised bones and teeth representing perinatal dinosaurs – either embryonic (just about to hatch) or dinosaurs that have recently hatched. Several different types of dinosaurs are represented, which means that high latitudes in the northern hemisphere were probably the dinosaur’s permanent home and that they nested there.

A Dinosaur Nursery

Researchers from the University of Alaska Museum, the Royal Tyrrell Museum, Florida State University and the University of Colorado writing in the academic journal “Current Biology”, report the discovery of tiny teeth — some less than 2 mm in length along with bones from seven species of perinatal dinosaurs. These tiny fossils were found after conducting a microscopic analysis of sediments from the bluffs that can be found along the shores of the Coleville River. These sediments are from the Prince Creek Formation and represent deposition that took place around 70 million years ago,

The field season is very short at such a high latitude. In the three weeks of field work that are possible, the team removed hundreds of kilograms of sediment from the face of the bluffs. The buckets of sediment are hauled down to the river’s edge, where team members wash the material through smaller and smaller screens until they have removed any large rocks and soil.

Once back at the lab, researchers run the material through more screens to remove all the clay, until all that’s left is sandy particles. Then, teaspoon by teaspoon, the team, including graduate and undergraduate students examine the sand under microscopes to find the tiny bones and teeth. This work has revealed tiny teeth of mammals, but in addition, tiny teeth and bones of dinosaurs have been discovered.

Endothermic Dinosaurs

Although not as cold as today, conditions in this part of northern Laramidia during the Late Cretaceous were extremely challenging. For around 120 days each year there was total darkness and it has been calculated that the mean average temperature was just 6.3°C ± 2.2°C (43.3°F ± 4.0°F). The Eumeralla and Wonthaggi Formations of Australia at a palaeolatitude of about 70° south, have also provided evidence of recently hatched dinosaurs and yearlings. However, the Prince Creek Formation at a latitude of 80°– 85° north represents the most extreme environment yet described for the Dinosauria. Intriguingly, whilst dinosaurs living in southern Gondwana (Eumeralla and Wonthaggi Formation fossil remains), would have experienced around 45 days of total darkness each year, this palaeoenvironment was still warm enough for ectothermic animals such as crocodilians and amphibians to thrive. However, no such “cold-blooded” animals are found in association with Prince Creek Formation sediments.

To survive such harsh conditions, the researchers conclude that the dinosaurs of Prince Creek Formation were endothermic, just like modern mammals and birds.

Lead author of the research Patrick Druckenmiller (University of Alaska Museum) commented:

“Recovering these tiny fossils is like panning for gold. It requires a great amount of time and effort to sort through tonnes of sediment grain-by-grain under a microscope. The fossils we found are rare but are scientifically rich in information”.

Dinosaurs were Year-round Residents of Northern Alaska

The presence of such young dinosaurs, who were not capable of making long, seasonal migrations is strong evidence to suggest that the dinosaur biota was present all year. The palaeoenvironment was extreme but numerous different types of dinosaur were able to thrive in this harsh habitat.

This discovery demonstrates just how adaptable members of the Dinosauria were and hints at a diverse and rich dinosaur dominated ecosystem hundreds of miles inside the Palaeo-Arctic Circle.

The scientific paper: “Nesting at extreme polar latitudes by non-avian dinosaurs” by Patrick S. Druckenmiller, Gregory M. Erickson, Donald Brinkman, Caleb M. Brown and Jaelyn J. Eberle published in Current Biology.

A new species of ancient beetle has been named and described based on preserved remains found in the poo (coprolite) of an ancestor of the dinosaurs. The beetle named Triamyxa coprolithica, is the first insect to be scientifically described from coprolite and this research, suggests that coprolite remains could become as important as insects preserved in amber when it comes to identifying new species.

Published in Current Biology

The researchers from Uppsala University (Sweden), in collaboration with entomologists from Sun Yat-sen National University (Taiwan), Jena University (Germany) and Guadalajara University in Mexico used synchrotron microtomography to examine the coprolite’s contents and sophisticated computer software to rebuild the tiny insects so that they could be studied. The coprolite contained numerous insect remains preserved in three-dimensions. Most insect fossils are squashed so flat that deciphering them is extremely difficult.

The researchers conclude that coprolites may prove to be an important source of information for exploring insect evolution. Their paper is published this week in “Current Biology”.

Silesaurus opolensis

Although the scientists cannot be certain, they speculate that the coprolite represents the scat from a relative of the dinosaurs called Silesaurus opolensis, which is known from the same Polish deposits associated with the coprolite. An animal (probably S. opolensis), swallowed a large number of these tiny insects 230 million years ago, the greedy reptile inadvertently giving palaeontologists a rare opportunity to study a beetle, at a time (the Triassic), when many different types of insect were evolving and diversifying.

Phylogenetic analysis suggests that T. coprolithica is a member of Myxophaga (fungal beetles), a small suborder of beetles with a sparse fossil record whose extant representatives are small and often associated with wet environments.

Complete Specimens Preserved

Some of the beetles were almost complete with even their antennae and thin legs intact and attached to the body.

Commenting on the significance of this research, lead author of the scientific paper, Martin Qvarnström, (Uppsala University), remarked:

“We were very positively surprised by how many beetle remains there were in the coprolite and above all how well preserved they were. We really have to thank Silesaurus, who was probably the animal that helped us collect and preserve the beetles”.

The labrador-sized Silesaurus did not usually dine on such small insects, it probably was a generalist eating a wide variety of prey. It had a beak that was possibly used to bite insects just like today’s living dinosaurs – the birds. Despite the fact that Silesaurus ingested lots of individuals of Triamyxa coprolithica, these small beetles probably did not constitute its main food. Triamyxa lived in the same environments as larger insects and it was these insects as well as small vertebrates that probably made up the majority of the diet of this fast running, agile reptile.

The beetle fossils are reminiscent of other beetle remains associated with amber. Both coprolites and amber are capable of preserving insects in three-dimensions and this study suggests coprolites can be extremely valuable for studying early insect evolution and extinct animal food chains at the same time.

The scientific paper: “Exceptionally preserved beetles in a Triassic coprolite of putative dinosauriform origin” by
Martin Qvarnström, Martin Fikáček, Joel Vikberg Wernström, Emmanuel Arriaga-Varela, Per E. Ahlberg and Grzegorz Niedźwiedzki published in Current Biology.