Category Archives: Paleontlontogy

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

Dinosaur Tail Preserved in Amber

When in doubt, go with dinosaurs!

As I have commented before, when I was a lad first interested in dinosaurs, the idea that feathers, skin, and other soft tissue might be preserved in fossils was considered remote to the point of fantasy. We would never have the data, and we would never know what dinosaurs looked like (or sounded like).

But we are now in a great age of fossil discovery, with new discoveries everyday, including well preserved tissue and many specimens with skin and feathers.

This month the buzz is about yet another find preserved in amber, which includes the feathered tail of an animal that lived in the Mid-Cretaceous (circa 99 million years ago) [1]. Found in Myanmar, this is yet another fabulous specimen emerging from this corner of Asia.

Fossils in amber can be beautifully preserved, and the this one certainly has extremely complete remnants of the feathers, revealing microscopic details. The specimen is especially informative, too, because it is preserved as a whole, with the skeleton, traces of flesh, and feathers together suggesting the structure of the living animal.

With preservation in amber, the finest details of feathers are visible in three dimensions, providing concrete evidence for feather morphologies and arrangement upon the tail” (p. 7)

The researchers interpret this as part of the tail of a non-avian dinosaur, likely a juvenile. As such, it is not known whether the structure or color of the feathers might represent the appearance of the adult, or might have molted as the animal matured.

In any case, this individual had brown feathers, nearly white underneath. The feathers themselves are somewhat “primitive” looking, they are not specialized for flight, and similar throughout the length of the tail. Again, this could be juvenile plumage, or it might represent the adult appearance, we don’t know.

Artist’s impression: the dinosaur was about the size of a sparrow. BBC 2016 http://www.bbc.com/news/science-environment-38224564

With the growing accumulation of fossil remains, we are gaining a much more detailed picture of the complicated story of feathered dinosaurs, both early avians and non-avians. Part of the story is the long history of feathers, which we now know have been evolving for 100 million years or more. (See the article for some detailed discussion of feather evolution.)


  1. Lida Xing, Ryan C. McKellar, Xing Xu, Gang Li, Ming Bai, W. Scott I. V. Persons, Tetsuto Miyashita, Michael J. Benton, Jianping Zhang, Alexander P. Wolfe, Qiru Yi, Kuowei Tseng, Hao Ran, and Philip J. Currie, A Feathered Dinosaur Tail with Primitive Plumage Trapped in Mid-Cretaceous Amber. Current Biology, http://dx.doi.org/10.1016/j.cub.2016.10.008

 

(PS. Wouldn’t “feather evolution” be a good name for a band?)

Did Dinosaurs Sing?

Very possibly not.

In this great age of dinosaur science, we are learning more and more about dinosaurs and other ancient species, including what they looked like, how they moved  and how they lived.

One thing we really know very little about is what dinosaurs sounded like.

We also have a sketchy understanding of the evolution of birds, i.e., the avian dinosaurs. Setting aside the messy “missing link” question (just how and when did birds diverge from their cousins the dinosaurs?), we know surprisingly little about the history of the key features of birddom:

  • Flight!
  • Feathers!
  • Eggs in Nests!
  • Song!

We know that there are early birds, contemporary with other dinosaurs, which had feathers (check) (and so did non-avian dinos) and nests (check) (and so did non-avian dinos), but we’re not sure about flight (probably some did, others may not have) (and non-avian dinos may also have flown).

But what about the most attractive feature of all, birdsong?

Our contemporary world is filled with bird and insect songs, at least if you can make the humans quiet down. Did the dinosaurs hear a chorus of birds? What might it have sounded like. And, if so, did non-avian dinos also sing? Or is that something uniquely avian?

Inquiring minds would like to know.

Julia A. Clarke,  and an international team of colleagues report this month a recent fossil find from Antarctica (which is a neat place to be paleontolgizing, no?), with the syrinx of an ancient bird [2]. The syrinx is the anatomical structure in birds that support their unique vocalizations, i.e., the honks, whistles, and songs.

The researchers note that very few remains of the syrinx are known in the fossil record, so this find is the oldest and only one from the time of the dinosaurs.

Interestingly, no similar finds are known for non-avian dinosaurs; which do have feathers and other features in common with birds–but not this distinctive sonic organ. This raises the possibility that dinosaurs could not chirp/honk/tweet, at least not the way birds do.

In fact, this particular specimen may suggest that modern vocal production might be a relatively recent evolutionary innovation, preceded by metabolic changes and feathered ornamentation. The researchers note that this possibility is interesting given current hypotehses about the importance of vocalization for the development of social structure and possibly the development of larger brains.

This fossil also suggests that there is a complicated evolutionary story to unravel, elucidating the relationships of social and mating behavior to brain, display, and vocal communication. Did birds sing, and then evolve brains to use vocal signals? Or were birds communicating to each other, and then singing evolved into a new channel?

These are deep and interesting questions about our favorite cohabitants on this planet.

In any case, it is possible that birdsong as we know it is a fairly recent development, and something that is unique to avians.

Cool!   As Patrick O’Connor comments,

“Clarke and colleagues have uncovered one key piece of that puzzle in a small bird fossil from Antarctica, foreshadowing the soundscape of things yet to come during avian diversification.” [2]

  1. Julia A. Clarke, Sankar Chatterjee, Zhiheng Li, Tobias Riede, Federico Agnolin, Franz Goller, Marcelo P. Isasi, Daniel R. Martinioni, Francisco J. Mussel, and Fernando E. Novas, Fossil evidence of the avian vocal organ from the Mesozoic. Nature, advance online publication 10/12/online 2016. http://dx.doi.org/10.1038/nature19852
  2. Patrick M. O’Connor,  Palaeontology: Ancient avian aria from Antarctica. Nature, advance online publication 10/12/online 2016. http://dx.doi.org/10.1038/nature19480