Category Archives: Paleontlontogy

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

 

Fossil Suggests Dinosaur Camouflage Pattern

It is a great age for dinosaur studies, with more and more fossil evidence coming to light, including finds from China, South America, and other areas sparsely recorded until this century.

One of the most exciting developments has been the discovery of non-skeletal remains, which was considered unimaginable when I was a kid (i.e., when I first became interested in dinosaurs and fossils).

In recent years we have seen remarkably preserved feathers, not only proving that dinosaurs wore feathers, but giving us a detailed view of what the feathers look like. Even more, this gives an idea of the color scheme of the animal.

This month an international team led by Jakob Vinther reported a remarkably preserved Psittacosaurus with considerable amounts of skin closely associated with the skeleton. The residues contain melanin, and the distribution was used to infer the possible visible appearance of the animal. Overall, it appears to be a (not too surprising) “countershading” pattern, dark on top, and light underneath, as well as a black or dark face.

Moving rather farther from the fossil remains, they also conducted a computational study, projecting the inferred colors onto a 3D model of the reconstructed body. The resulting model was studied by applying different lighting, representing conditions in possible habitats (open desert, deep forest, etc.) They conclude that the pattern is an effective visual camouflage for a forest. The pattern might also suggest bipedal walking, though that is more speculative.

I note that Psittacosaurus has a rather mysterious bristles on the tail. These don’t resemble familiar avian species, and it is not clear what function they may have had. Dinosaurs are so weird, that’s part of what is so fun!

This is an outstanding find and it is so cool to get some real notion of what dinosaurs looked like.

It is also an interesting example of “computational” argument, sliding farther and farther from the fossil data, piling inferences upon inferences, and comparing models (theoretically based) with reconstructions from the data. The headline conclusions about color scheme and inferred habitat are based on a rather long chain of inference, as well as arguments based on computations.

I call this “computational” argument, though the computations were not fully digital as would be expected. Actually, the modelling in this case was surprisingly “analog”.  For some reason they eschewed the obvious digital modelling in favor of a much less convenient and accurate plaster model. The lighting was done in situ in a botanical garden, rather than using simulations that could explore a broad and continuous range of environments.

The final conclusions are scarcely controversial (countershading is a common adaptation, the fossil was found in a fossil forest environment). Still, I think it will be important to replicate this study, revisiting the assumptions and inferences explicit and implicit in the modelling and computer analysis. I’m not sure whether the published materials are sufficient for such a review or not.

This replicability problem is a perennial challenge for digitally enabled science of all kinds.


  1. Jakob Vinther, Robert Nicholls, Stephan Lautenschlager, Michael Pittman, Thomas G Kaye, Emily Rayfield, Gerald Mayr, and Innes C Cuthill, 3D Camouflage in an Ornithischian Dinosaur. Current Biology, http://www.sciencedirect.com/science/article/pii/S0960982216307060

Theropods in Amber

A really cool fossil find from Myanmar: bird’s wings mumified in Amber. As Lida Xing and coauthors report, the extraordinary fossil preserved “the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues.” (p. 1) I.e., we can have a rare glimpse of what the wing of this animal actually looked like in life.

The sample is dated to approximately 99 million years ago—the mid-Cretaceous period. The specimens are identified as “theropods”, which means something bird or dinosaur-y. The evidence suggests that these are newly hatched birds that became trapped in amber. The fully fledged wings indicate that this species was precocial, i.e., born ready to leave the nest immediately, as some birds are. Thus, the fossil also hints that this developmental pattern was present in the past.

The preserved feathers suggest that the animal might have appeared brown with white undersides. Given that these are baby chicks, it is possible that the mature animals would have different plumage. But this is one of the clearest records of the coloring of a “dinosaur”.

As the BBC says, this is a spectacular find!

Nice work, all.

From Figure 2 (f)” Alula barbs with blunted apices and blade-like barbules with banded pigmentation.” (the scale bar is 1.5 mm) Link: http://www.nature.com/ncomms/2016/160628/ncomms12089/fig_tab/ncomms12089_F2.html

 

  1. Xing, Lida, Ryan C. McKellar, Min Wang, Ming Bai, Jingmai K. O/’Connor, Michael J. Benton, Jianping Zhang, Yan Wang, Kuowei Tseng, Martin G. Lockley, Gang Li, Weiwei Zhang, and Xing Xu, Mummified precocial bird wings in mid-Cretaceous Burmese amber. Nat Commun, 7 06/28/online 2016. http://dx.doi.org/10.1038/ncomms12089

 

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