Category Archives: Paleontlontogy

New Studies About The Chicxulub Asteroid Impact

As everyone knows, there was a large impact at what is now the Gulf of Mexico (the Chicxulub impact) at the exact time that the non-avian dinosaurs died out .  What we don’t really know, though, is how such an impact could wipe out so many species around the globe. It was a big hit for sure, but not necessarily that big.   And, don’t forget that the avian dinosaurs and lots of other species did survive.

The outer rim (white arc) of the crater lies under the Yucatan Peninsula itself, but the inner peak ring is best accessed offshore. Image credit: NASA

There are various ideas about what might have happened. Perhaps the body was a comet, with a lot of gook in the slush. Perhaps the dinosaurs were on the edge of extinction anyway, and the impact was a coincidence that finished them off.  Perhaps there were fires and volcanoes, that created a ‘nuclear winter’ for a century or more. (There is a layer of soot, indicating something like that.)

This year there have been a series of detailed analyses of the Chicxulub Impact Event (and wouldn’t that be a great name for a band!). Much of the new analysis comes from a drilling expedition sponsored by ECORD, the European Consortium for Ocean Research Drilling, Expedition 364 Chicxulub K-Pg Impact Crater“.  (There is no substitute for actual field research, no?)

 The impact was in shallow water, and therefore gouged out a huge amount of the sea floor, which filled the atmosphere with dust [2]. This could have released hundreds of gigatons of CO2 and other chemicals, which could have caused decades of cooling and even longer lasting acidification of the oceans  [3].

This fall, a Japanese team suggested that the area of the impact had a relatively high concentration of hydrocarbons in the rock, resulting in an especially large fireball and huge amounts of soot in the atmosphere [5].

And so on.

I’m no expert on geology or climate modelling, so I can’t really dissect these ideas in detail.

There doesn’t seem to be much disagreement that there was a big boom, with tsunamis and huge forest fires, and very probably earthquakes and volcanoes.  (The Earth ‘rang like a bell’ as one geologist told me.)  For decades after the hit, it looks like there was global cooling and other climate changes—a ‘nuclear winter’ scenario, which killed plants and land animals, and profoundly changed life in the oceans.

It’s clear enough that a Chicxulub scale impact is very bad news for a planet.

But it’s still not clear why the dinosaurs were wiped out everywhere, while plenty of other species survived, including ancestors of birds, frogs, fish, and mammals which lived side-by-side with dinosaurs.

But these new and more detailed studies are giving us a lot to work with.  Combined with more and more fossil evidence, we may be able to come up with some ideas about what combination of luck, geography, physiology, and who knows what may have influenced who died out and who survived Chicxulub.


  1. Jonathan Amos, Asteroid impact plunged dinosaurs into catastrophic ‘winter’, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-41825471
  2. Jonathan Amos, Dinosaur asteroid hit ‘worst possible place’, in BBC News – Science and Environment. 2017. http://www.bbc.com/news/science-environment-39922998
  3. Natalia Artemieva, Joanna Morgan, and Expedition 364 Science Party, Quantifying the Release of Climate-Active Gases by Large Meteorite Impacts With a Case Study of Chicxulub. Geophysical Research Letters, 44 (20):10,180-10,188, 2017. http://dx.doi.org/10.1002/2017GL074879
  4. Julia Brugger, Georg Feulner, and Stefan Petri, Baby, it’s cold outside: Climate model simulations of the effects of the asteroid impact at the end of the Cretaceous. Geophysical Research Letters, 44 (1):419-427, 2017. http://dx.doi.org/10.1002/2016GL072241
  5. Kunio Kaiho and Naga Oshima, Site of asteroid impact changed the history of life on Earth: the low probability of mass extinction. Scientific Reports, 7 (1):14855, 2017/11/09 2017. https://doi.org/10.1038/s41598-017-14199-x

 

PS.  Some great names for bands:

Chicxulub
The Chicxulub Event
We Are Children of Chicxulub
Thanks to Chicxulub
Brought to You By Chicxulub

 

 

 

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

 

New Study of Mass Extinctions

There have been five mass extinctions in the history of life on Earth, during which vast numbers of animals and plants died out. So far, after each big die off, new species and families have evolved, filling the world with a new, but just as diverse array of life forms as before the disaster

The general intuition is that a mass extinction creates an impoverished, less diverse collection of species. The survivors who weather the disaster are the founders of the great radiation of new diversity. (This pattern is seen at a smaller scale in local disasters, such as volcanic eruption that obliterates almost all life.)

This intuition is often applied to our own age, which we recognize as the beginning of the sixth great extinction.. We see many specialized species reduced and wiped out, while other robust “generalists”, such as cockroaches or rats, thrive and spread. Presumably, 100,000 years from now, there may be a vast radiation of new species of rodents, expanding into the empty niches of the post human Earth.

But is this process really what has happened in the past extinctions?

This month, David J. Button and colleagues publish a report of their study of “faunal cosmopolitanism” among 1046 early amniote species ranging from 315–170 M years ago. This period includes the Permian–Triassic and Triassic–Jurassic mass extinctions [1].

They take into account the relationships among the species, so that individuals from related but distinct species can reflect the geographical range of the group, even if only a few samples are available.

The basic finding supports the common intuition: there is a sharp rise in their index of cosmopolitanism (phylogenetic biogeographic connectedness) after the Permian–Triassic extinction, followed by a decrease (i.e., more geographic specialization through the Triassic, and another spike after the Triassic–Jurassic extinction.

Furthermore, they find evidence that “the increases in pBC following each extinction were primarily driven by the opportunistic radiation of novel taxa to generate cosmopolitan ‘disaster faunas’, rather than being due to preferential extinction of endemic taxa .” (p. 4)  I.e., new “cosmopolitan” species emerge, rather than a old species survives to spread over the world.  (This is bad news for cockroaches and rats, I’m afraid.)

These results certainly indicate the importance of unique events in the history of life, such as mass extinctions. They also suggest that mass extinctions have a predictable effect, at least at a global level.

Neat.


  1. David J Button, Graeme T. Lloyd, Martin D.Ezcurra, and Richard J. Butler, Mass extinctions drove increased global faunal cosmopolitanism on the supercontinent Pangaea. Nature Communications, 8 (1):733, 2017/10/10 2017. https://doi.org/10.1038/s41467-017-00827-7

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

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

 

Study Proposes New Family Tree For Dinosaurs

There is quite a bit of buzz this week about Matthew Barron and colleagues report on a new classification of dinosaurs [1].

The researchers amassed a very large dataset of dinosaur fossils, the largest and most comprehensive known collection. The data include specimens from 74 taxa which were scored on 457 traits. (While Dinosaurian in comparison to earlier studies, in this age of Big Data this dataset is still pretty puny.   As the press reports noted, it took years to round up the data by hand, and five minutes to run the program.)

The resulting family tree is considerably different from text book consensus up to now. As it should be. The overthrown classifications were based on small datasets and quite a few untested assumptions and intuitions. Since the new analysis doesn’t include these assumptions, the results are different.

From: Figure 1: Phylogenetic relationships of early dinosaurs. From A new hypothesis of dinosaur relationships and early dinosaur evolution Matthew G. Baron, David B. Norman & Paul M. Barrett Nature 543, 501–506 (23 March 2017) doi:10.1038/nature21700

Of course, this sort of analysis needs to be taken carefully. This dataset is big enough and broad enough that it is worth taking seriously, but we still need to remember the limitations of the method.

First of all, the data are based mainly on skeletal remains, which are only a partial picture of the animals in question. We know only too well that skeletal analysis can mislead.

In addition, this kind of analysis can be quite sensitive to the exact sample used. Adding or omitting some traits, or additional fossils could rearrange the results, possibly quite a bit.   This means that future contributions might well produce different results.

The researchers point out some aspects of the classification that seem to add face validity to the results. In this tree, the earliest taxa seem to be small and omnivorous, which makes sense. Gigantic size and specialized diets would seem to be evolved from more moderate sized and general animals.

One conclusion that is particularly interesting is that in this taxonomy, “the supinated, grasping hands seen in some early taxa are interpreted as the primitive dino- saurian condition.” (p. 505) In other words, early dinosaurs had grasping front pawa. As they say, this might have been a key evolutionary advantage, and might also have been a precursor to development of bipedalism.

Cool.


  1. Matthew G. Baron, David B. Norman, and Paul M. Barrett, A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543 (7646):501-506, 03/23/print 2017. http://dx.doi.org/10.1038/nature21700