Category Archives: Dinosaurs

Dinosaur Face Coloring and Camouflage

In recent years, we have learned tons of things about Dinosaurs, including stuff that used to be thought beyond discovery, such as their color schemes.

We now have evidence about the camouflage schemes of dinosaurs, which are similar to contemporary animals. (Earlier posts here, here, here, here)

This month Fiann M. Smithwick
 and colleagues from University of Bristol describe the coloring of a small theropod that lived in the Early Cretaceous [2]. The work is based on three well preserved specimens from the prolific beds of Liaoning, China. These fossils have fairly complete skeletons, and trances of melanin that indicate the skin coloring. These little guys were about the size of a kitten, except for their half-meter long tail.

The new study found evidence that the tail was ringed, the body dark on top with light belly (countershatding) and the head had a “mask” that surrounded the eye.

Sinosauropteryx probably lived in open environments, under constant threat of predation Artwork Robert Nicholls:

All of these features are known form contemporary species (the BBC notes that this bandit mask is known in man contemporary species, including raccoons, badgers, and nuthatches, among others.) What evolutionary advantage may be incurred by a striped tail or bandit mask is not known.

To investigate the purported camouflage effects countershading coloration, the researchers conducted an interesting computer graphics aided study.

The idea is that “the pattern of pigmentation from the dorsal to ventral body regions should match the illumination gradient created by the lighting environment in which it lives”. The countershading serves to “self-shadow”, and reduce the visual cues that outline the animal’s body—ideally, making it less noticeable to any passing T. rex or its own small tasty lunch.

Specifically, out in a clearly lighted area, the shadows are sharp and high up on the body. In diffuse light of a forest, the shadows are softer. Thus, “Paleocolor can help predict paleohabitat.”

Using Blender, they created 3D computer models of the torso, which were 3D printed. The models could be photographed in different lighting conditions, to show how the shadows fall.

The research showed that in strong overhead light, the shadow transition falls in the area of the imputed countershading. This suggests that the animal was adapted to live in an open, well sunlit environment.

As a computer scientist, I noticed that the researchers didn’t trust the lighting algorithms of Blender for this exercise. I suspect they would have worked well. But, I grant you that this would have introduced complicated logical dependencies on the shading algorithms and software implementation.

The conclusion is that this small animal lived in open areas, where there was little cover to hide. They comment that one of the specimens had recently eaten a lizard at the time of its death, and that lizard resembles species that live in the open.

Paleocolor can help predict paleohabitat.”

This is a pretty cool study, demonstrating that color schemes may add to understanding of ancient species and ecologies.

The study shows that even without much direct data about the habitat,

reconstructing the color of extinct animals can inform on their ecologies beyond what may be obvious from skeletal remains alone.” (p.1)

It is also interesting that this and other studies of paleocolor adds to the evidence of similar adaptations among contemporary and ancient species. This can only improve understanding of the contingencies of evolution and adaptive advantages.

Oh, and also, “Yay for computer graphics and simulations!”


  1. Paul Rincon, Dinosaur sported ‘bandit mask, in BBC News – Science & Environment 2017. http://www.bbc.com/news/science-environment-41763478
  2. Fiann M. Smithwick, Robert Nicholls, Innes C. Cuthill, and Jakob Vinther, Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal Heterogeneous Habitats in the Early Cretaceous Jehol Biota. Current Biology, https://www.sciencedirect.com/science/article/pii/S0960982217311971

 

PS.  Several Ideas for Great Band Names:

Countershading
Banded tail
Dinosaur bandit mask
Paleocoloration

 

Book Review: “Weird Dinosaurs” by John Pickrell

Weird Dinosaurs by John Pickrell

You had me at “Dinosaurs”! : – )

I mean, a big part of the appeal of Dinophilia is that Dinosaurs are, and always have been mind-blowingly weird.

Pickrell’s point, of course, is that the last two decades have seen an explosion of new fossils, as well as new information from Buck Rogers technology. The weirdness we knew and loved has gotten even more weird.

Just as a for instance: when I was a lad, Triceratops was Triceratops, with three horns. One of the plates in this book is a painting of dozens of different species of Triceratops with an astonishing variety of facial horns and crests. It’s stunning.

This fine little book is a quick tour around the world, sampling the newest Dinosaur discoveries from China, South America, Australia, Antarctica—everywhere. Mostly, this is about all the new species of Dinosaurs that have been discovered, but the main point is the diversity and wonderful strangeness of the new understanding of the ancient times.

Some of the discoveries have had a splash of publicity, but almost all of the big finds are part of a stream of equally interesting, but less known new discoveries.

Pickrell gives a lot of attention to the history and lives of Paleontologists. These Dinosaurs didn’t discover themselves, and the story of how they were found and interpreted is important and cool.  He’s also a working paleontologist, so he explains the techniques and challenges of the field work that yields these wonders.

In some cases, fossils were uncovered a long time ago, and have been reinterpreted in light of later information. Other finds have been lost forever, but reconstructed from new data. Yet others have been discovered in some dusty back room. And, of course, whole new regions of the world are being scientifically explored for the first time.

Altogether, the story of Dinosaurs, and birds and mammals, too, is becoming much more complicated and nuanced. Everywhere we look there are more and different Dinosaurs, and we know that there are far more to be found.


Pickrell is a good writer, and his love of Dinosaurs comes through on every page. He seems to get to travel all over the world visiting Paleontologists, which is good work if you can get it.

The biggest problem with the book is that there are so few pictures. Honestly, telling me a list of all the species found at a given location is impossible for me to follow, especially with no illustrations to help. This is definitely a book that deserves a plate on every few pages. I know that is probably impractical, but I can wish for it.


  1. John Pickrell, Weird Dinosaurs: The Strange New Fossils Challenging Everything We Thought We Knew, New York, Columbia University Press, 2016.

 

Sunday Book Reviews

 

Dinosaur Camouflage: Hiding From Hunters

Regular readers know that I love dinosaurs.

T. rex. Avian and bird-like dinos.   Stegosaurs. Triceratops. So cool!

And how about ankylosaurs, the wild family of armored dinosaurs.

This month Caleb Brown and colleagues report on an astonishingly well-preserved fossil of an ankylosaur discovered in Alberta [1]. The specimen was tagged Borealopelta markmitchelli, and lived about 110 million years ago.

The animal was about the size of a rhinoceros or moose. It’s back and neck are covered with hard, spiky armor, so characteristic of ankylosaurs.

The biggest news, though, is that the scales are so well-preserved that it is possible to discern the pigments that indicate the skin color. These observations indicate that the Borealopelta had a camouflage scheme similar to deer and other heavily hunted species. The color scheme appears to be a darker brown on top, with light underbelly.

Royal Tyrrell Museum of Palaeontology, Drumheller, Image caption An illustration of the 110-million-year-old Borealopelta markmitchelli

 

The researchers indicate that the color scheme is an important indication that these animals were under significant pressure from predators. The “armor” of anlyosaurs has long been assumed to be defensive, though no direct evidence of predation is available. The new evidence of coloration suggests that this was indeed the case.

Preserved evidence of countershading suggests that the preda- tion pressure on Borealopelta, even at large adult size, was strong enough to select for camouflage from visual predator.” ([1], p. 6)

The paper points out that in living species, larger animals do not show countershading, nor to smaller animals with defensive equipment. The Borealopelta is large, yet still has both armor and camouflage. The researchers conclude that this means only one thing: they were prey for large, powerful, and visual hunters. The obvious candidates are theropods. What else could bring down such a large, heavily armored beast?

Finding a large, heavily armored herbivorous dinosaur is the most concrete evidence, therefore, for intense predation on very large prey in the Mesozoic.” ([1], Supplemental Discussion)

Neat!


  1. Caleb M. Brown, Donald M. Henderson, Jakob Vinther, Ian Fletcher, Ainara Sistiaga, Jorsua Herrera, and Roger E. Summons, An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics. Current Biology, http://dx.doi.org/10.1016/j.cub.2017.06.071
  2. Sarah Gabbott, Armoured tank-like dino used camouflage to hide, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-40815935

How Fast was T. Rex?

Tyrannosaurus Rex is everyone’s favorite dinosaur, and we’ve all seen dozens of depictions of T. rex, and various more or less scientific reconstructions of its appearance and behavior.

One question has always been, “how fast did T. rex run?”

Experience from living land animals suggests that really large individuals are often slow-moving. On the other hand, T rex certainly looks like a fast runner, though it might have relied on surprise ambushes or even on harvesting carrion.

This month Sellers, William I published a study that uses mathematical models of the structure of the T rex skeleton, taking into account the strength of the bones [1]. The idea is that running stresses the body, and ultimately an animal cannot run so fast that it breaks its bones and joints.

There is a long history of biomechanica studies of living animals which has been applied to fossils including T. rex. These methods use the measurements of the skeleton along with plausible hypotheses about the muscles and other tissues to estimate the “locomotor performance” of the ancient animals. The authors report that these studies have given a range of estimates for how fast a T rex could move, from 5 to 15 m/s, including walking and running gaits.

The current study refines these estimates using two simulations, a mechanical model of the skeleton and a model of the stress on the bones.

Machine learning algorithms are used to generate the muscle activation patterns that simultaneously produce the maximum locomotor speed of a MBDA model of T. rex whilst maintaining defined skeletal safety factors.” ([1], p. 3)

These simulations were run driven by models of walking and running gaits. The detailed model involves all the muscle firings in the animal, so finding a stable gait is a huge computation. The system was run many times to search for maximum speed using the gaits. (See the paper for details.)

These computations indicate that the fast walking gait is consistent with bone stresses typically seen in living animals, which the running gaits often exceed typical stress levels. The authors argue that this indicates that adult T. rex did not run.

Considering the size of the animal, this isn’t a completely surprising conclusion. This fast walk may have been perfectly sufficient, given the size of their herbivore prey, which probably couldn’t run fast either.

The researchers are careful to point out that their simulations are simplified in order to make them computationally feasible. This method is effectively searching through all possible designs for a T. rex, which is a ludicrously large number of variables. In the future, more complete models may be possible, and the results may be refined.

They note that the behavior of a T. rex must have changed as it developed. The smaller young ones might have been fast runners, but reduced to walking as they grow enormous. But little is known about the developmental process.

The also note that their result overturned estimates based on analogy.

It is somewhat paradoxical that the relatively long and gracile limbs of T. rex—long argued to indicate competent running ability […]—would actually have mechanically limited it to walking gaits, and indeed maximised its walking speed. This observation illustrates the limitation of approaches that rely solely on analogy and the importance of a full biomechanical analysis when investigating animals with extreme morphologies such as T. rex.” ([1], p..13)

Cool.

Both dinosaurs and a neat example of multiphysics models, and an example of why HPC is relevant to lots of fields.


  1.  William I. Sellers, Stuart B. Pond, Charlotte A. Brassey, Philip L. Manning, and Karl T. Bates, Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis. PeerJ, 5:e3420, 2017/07/18 2017. https://doi.org/10.7717/peerj.3420

Life After the Dinosaurs

Everyone knows about the mass extinction that ended the age of dinosaurs. This is often said to have opened the way for the age of mammals and eventually us.

Of course, it wasn’t exactly like that.

In the wake of the mass extinction, there was an explosive radiation of all the surviving species, not just mammals.

This month saw two articles about this exciting period.

First of all, the dinosaurs didn’t actually all die out. One whole wing of the family survived and thrived until today: the birds.

Ksepka, Daniel T., Thomas A. Stidham, and Thomas E. Williamson report on new findings which document the rapid diversification of birds after the extinction event.[2].  Specifically, they report a small bird that is dated from the very early Paleocene, i.e., soon after the end of the dinosaurs. They argue that dating this species implies that four major groups of birds arose soon after that.

The authors comment that this observation puts the diversification of birds on approximately the same time line as the expansion of mammals.


In a different study, Yan-Jie Feng and collagues analyzed DNA from 156 living species of frogs to construct a putative taxonimic history, anchored by 20 representative fossils [1]. The results suggest that “three species-rich clades (Hyloidea, Microhylidae, and Natatanura), which together comprise ∼88% of extant anuran species, simultaneously underwent rapid diversification” right after the end of the dinosaurs. ([1], p. 1)

They argue that the “mass extinction may have triggered explosive radiations of frogs by creating new ecological opportunities.” There is a very telling diagram in the full article, with a gigantic fan out of species just past the red line of the Cretaceous extinction event.

The researchers comment that their molecular study is important because the fossil record of frogs is sparse. This is one of the clearest pictures, albeit indirectly, that documents the evolutionary history of frogs during this period.

Again, this is the same time scale as mammals and birds, suggesting that there was a mad evolutionary scramble to fill the huge void left by the mass extinction at the end of the Cretaceous.

Cool!


After the Dinosaurs came not the “Age of Mammals” but the “Age of Pretty Much Everything Except Non-Avian Dinosaurs”! 🙂


  1. Yan-Jie Feng, David C. Blackburn, Dan Liang, David M. Hillis, David B. Wake, David C. Cannatella, and Peng Zhang, Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences, July 3, 2017 2017. http://www.pnas.org/content/early/2017/06/26/1704632114.abstract
  2.  Daniel T. Ksepka, Thomas A. Stidham, and Thomas E. Williamson, Early Paleocene landbird supports rapid phylogenetic and morphological diversification of crown birds after the K–Pg mass extinction. Proceedings of the National Academy of Sciences, July 10, 2017 2017. http://www.pnas.org/content/early/2017/07/05/1700188114.abstract

 

Dinosaurs Rising From The Ashes

We’re all fascinated with the story of the end of the Dinosaurs, which corresponds with a really big impact, and possibly other catastrophes. The death of the dinosaurs is not only a puzzle, it is the event that made room for mammals and puny humans to evolve.

But there was also a mass extinction that cleared the way for the great adaptive radiation of dinosaurs. At the end of the Triassic period, about 200M years ago, there was a massive extinction of animals. The dinosaurs rose after this catastrophe.

This month a team of British scientists published new evidence that there was a huge sequence volcanic eruptions at that time, which would have been devastating for living things. This event has been suspected from other evidence of huge lava flows, global cooling (due to volcanic material in the atmosphere), and, of course, mass extinctions.

The new study uses a new techniques which measures mercury (Hg) in the rocks. This element is highly correlated with volcanic activity, which spews Hg into the air.  The mercury falsl out and is incorporated into rock, where it persists for long periods of time–hundreds of millions of years.

Careful measurements indicate high levels of mercury in the period between the extinctions at the end of the Triassic, and the beginning of the Jurassic. In other words, a very clear suggestion that the volcanic disaster caused the extinctions, and the end of the episode was followed by the rise of the dinosaurs.

A key aspect of this work is to trace mercury deposits to many locations around the world. Furthermore, the deposits should be temporally aligned, rising and falling at the same time.   These signatures are consistent with large volcanic “pulses”.

The researchers report that the “Hg excursions are recorded in five of the six sections studied”, and that “The onset of Hg enrichment occurred synchronously across the globe, coincident with the end-Triassic extinction and associated global carbon cycle perturbation.“ (p.5)

In other words, there is clear evidence of very widespread effects of volcanism at the precise time of the mass extinctions.

As Rebecca Morelle puts it, “The onset of Hg enrichment occurred synchronously across the globe, coincident with the end-Triassic extinction and associated global carbon cycle perturbation.

And, evidently, ancestors of the dinosaurs survived this catastrophe, and “once the volcanoes had simmered down, few of their competitors were left, allowing the age of the dinosaurs to begin.”

The dinosaur age began and ended in world-wide catastophe that wiped out most living species, clearing the way for another burst of speciation.

The “age of mammals” started with the catastrophe that killed off the dinosaurs.  It is ending now with the sixth extinction, and, most likely, a spike in global temperature.


  1. Rebecca Morelle, Volcanoes ‘triggered dawn of dinosaurs’, in BBC News: Science & Environment. 2017. http://www.bbc.com/news/science-environment-40333902
  2. Lawrence M. E Percival, Micha Ruhl, Stephen P. Hesselbo, Hugh C. Jenkyns, Tamsin A. Mather, and Jessica H. Whiteside, Mercury evidence for pulsed volcanism during the end-Triassic mass extinction. Proceedings of the National Academy of Sciences, June 19, 2017 2017. http://www.pnas.org/content/early/2017/06/13/1705378114.abstract

New Study: Tyrannosaurs Not Furry

One rule of thumb for blogging is, “when in doubt, go with Dinosaurs!”.  And, for preference, T. rex, of course.  🙂

As I have said, this is the great age of Dinosaur science. Aided in part by the opening of rich fossil beds in China, but also by better and better technology that lets us see much more from the fossils we find.

No controversy has been more controversial than the kerfluffle over feathered Dinosaurs. It’s not that many Dinosaurs couldn’t or shouldn’t have feathers—they did.  They are the ancestors of birds, after all.

But it’s very hard to accept a feathery T. rex. The very paragon of bad ass, top of the top predators, T. rex really should not be fluffy. I mean you’re dead anyway, but you don’t want to be saying, “ooh, look at that gorgeous thing” just as you are snarfed down by the most ferocious land animal ever. It’s just not dignified.

This month Phil Bell and colleagues from around the world published a new detailed study of the skin of Tyrannosaurus rex and family [1]. They conclude that T. rex was not feathered, though it might have had a some feathers on its back. It remains possible that baby rexes may have had features that shed as the animals matured. (We don’t know much at all about baby rexes.)

This finding makes sense form the point of view of thermoregulation. Large, active animals don’t really need a coat of feathers to keep warm. It also might indicate T. rex migrated to live a warmer climate, or out into hot open spaces.

Ancestors of T. rex definitely had a lot of hair-like feathers, and some of them grew to be fairly large, as large as some Tyrannosaurs. So there is still a lot to be learned about the evolution of these animals, and what may have influenced the evolution of feathers and scales.

It is important to note that this is one of the most comprehensive studies of fossils that preserve the skin, but it is nevertheless a pretty tiny dataset (a dozen or two samples). In addition, feathers are a lot less likely to be preserved than skin, so the absence of fossil feathers isn’t necessarily evidence of absence [2].

But for now, I’m not going to visualize T. rex as being fluffy.


  1. Phil R. Bell, Nicolás E. Campione, W. Scott Persons, Philip J. Currie, Peter L. Larson, Darren H. Tanke, and Robert T. Bakker, Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution. Biology Letters, 13 (6) 2017. http://rsbl.royalsocietypublishing.org/content/13/6/20170092.abstract
  2. Helen Briggs, Study casts doubt on the idea of ‘big fluffy T. rex’, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-40172587