A Tyrannosaur’s Last Meal

I, like many six-year olds, love dinosaurs.  And nothing fascinates quite like Tyrannosaurus rex.  THE dinosaur. 

In recent decades we have found more fossils of T. rex and relatives than ever before, and there is a minor industry in T. rex theories.   Whole books have been written (and, I’m sure, soon rewritten).  Controversies about feathers, lips, how fast rexie could run, and so on.

There are now enough remains to estimate rexie populations and distributions. And, one of the most interesting developments are hypotheses about the life cycle of rexies.  In particular, it is now clear that teen age rexies probably hunted in packs, and ate different stuff from fully grown tyrannosaurs.

Which means there were rexies all over the place, from tiny newborns, through midsize juvenile, up to full size, adult, wide bodies.  There were also multiple species, cousins to the classic Tryannosaur, running all over the place.  

This winter, an international team report on a fossil juvenile Gorgosaurus (a cousin of T. rex) found in Alberta.  The partial skeleton includes the ribs and midsection and, importantly, it includes well preserved bones of what the dinosaur last ate before dying! [3]

The ‘last meal’ is identified as two young Citipes, i.e., baby ovirapotors, which would have been about the size of a turkey.  As the researchers note, “Young dinosaurs, like yearling Citipes, could have represented an abundant and reliable food source for juvenile Gorgosaurus.” ([3], p. 7)

This find is consistent with hypotheses about the life cycle of rexies, supporting the existence of “ontogenetic dietary shift”.  I.e., baby rexies at small stuff (insects and lizards, maybe), teen rexes ate larger stuff (baby dinosaurs), and adult rexies ate, well, whatever they wanted to eat.

From a strategic evolutionary perspective, the researchers suggest that this life style let rexies retain “mesopredator” niches (i.e., middle size prey), and as adults, move into megapredator niches, taking the biggest prey.  I.e., as a species, they hogged everything.

Awesome!

“The ability of tyrannosauroids, including tyrannosaurids, to assimilate the apex predator ecological niche while retaining the ancestral mesopredator niche (as juveniles) was likely key to their evolutionary success as some of the largest carnivorous theropods to have existed.”  

([3], p. 7)

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1. Victoria Gill, Tyrannosaur’s last meal was two baby dinosaurs, in BBC News – Science & Environment, December 8, 2023. https://www.bbc.com/news/science-environment-67642374
2. Michael Greshko, A Tyrannosaur Was Found Fossilized, and So Was Its Last Meal, in New York Times. 2023: New York. https://www.nytimes.com/2023/12/08/science/tyrannosaur-last-meal-gorgosaurus.html
3. François Therrien, Darla K. Zelenitsky, Kohei Tanaka, Jared T. Voris, Gregory M. Erickson, Philip J. Currie, Christopher L. DeBuhr, and Yoshitsugu Kobayashi, Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator. Science Advances, 9 (49):eadi0505,  2023. https://doi.org/10.1126/sciadv.adi0505

A Study of T rex Bite Force

Tyrannosaurus rex is everybody’s favorite and paradigmatic dinosaur.

And one big reason is their enormous head, with a frightening array of killer teeth.  This was a beast that could really bite!  Possibly, the all time champion biter, at least in our heads.

Nowadays, we know a bit about the life history and evolution of T rex.  Ancestors of the big boys and girls were smaller, as were young rexies.  Still frightening, but not quite at the peak. 

But, just how strong was their bite? 

This fall an international group of researchers report a study of the biomechanics of the skulls of  T rex and relations [1].  They measured the skulls of a variety of close relations to T rex, some small, some large.  These measurements were used to reconstruct the musculature of the living animal, and to estimate the bite force and stresses on the bones.

These measurements and models took a lot of work, because fossil skulls are usually incomplete and difficult to measure.  So, kudos for the careful work.

Basically, the harder the bite, the more stress on the jaw and skull bones.  Or, alternatively, the more stress the bones could sustain, the harder the animal could have bitten.

In general, the smaller and more gracile specimens would have less stress on the bones.  This means that ancestors of the apex rexies, and also younger rexies, would have less bite force than the big ones.  Pretty much as expected.

The researchers hypothesize that the smaller bite force would mean that these animals fed on relatively small prey, compared to the biggest specimens who would eat, well, whatever they wanted to eat.  This is consistent with notions that young rexies fed on different prey than the grown ups.

It should be noted that even with the differences among the specimens, all of these animals would have delivered a serious bite.  And notably, young juvenile rexies had a more powerful bite that full grown ancestral and related species.  “This was a powerful predator regardless of age.”  [2]

These findings alone don’t really provide much detailed information about the behavior or preferred prey of these animals.  But they will be combined with other information to refined interpretations and understandings about what these animals ate and how they caught them.

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1. Evan Johnson-Ransom, Feng Li, Xing Xu, Raul Ramos, Adam J. Midzuk, Ulrike Thon, Kyle Atkins-Weltman, and Eric Snively, Comparative cranial biomechanics reveal that Late Cretaceous tyrannosaurids exerted relatively greater bite force than in early-diverging tyrannosauroids. The Anatomical Record, n/a (n/a) 2023/09/29 2023. https://doi.org/10.1002/ar.25326
2. Jeanne Timmons, How the T. Rex Built Up That Bone-Crushing Bite, in New York Times. 2023: New York. https://www.nytimes.com/2023/11/10/science/t-rex-bite-skull.html

Can I Have a Pet T. rex?

Hey!  I want one, too!  (Who doesn’t?)

It’s a great headline, and definitely the kind of stuff that makes going to school a great experience.

The PR video doesn’t have a lot of detail or citations, so it looks like the pet T. rex isn’t coming to stores this year. Rats.

The basic idea is part of the great flourishing of digitally enhanced paleontology.  Not only vastly upgraded data and analysis, but also snazzy sensors (UAVs!  Ground penetrating radars!  Laser altimeters!  Cool field spectroscopy!)

But also 3D modelling and graphics, and, as this video suggests cheap and easy robots.

Dinosaurs and robots naturally cohabit in any nerd’s brain, but these days it is feasible to go ahead and try to build robot dinosaurs. You know you want to….

As in any biomimetic robotics, the exploration cuts several ways.  As Dr. Carter says “let’s put a motor on the T. rex spine”.  This forces a fossil reconstruction to get real in ways that static studies never will.  And, going the other way, examining how spines work throughout evolutionary history can teach robot designers about spines. 

Neat.

The Flowers of Chicxulub

The Chicxulub impactor wiped out the dinosaurs (except birds).  A lot of other species died that day, too.

But, astonishingly enough, some animal species survived, including some reptiles (such as turtles and crocodiles), mammals, and avian dinosaurs, AKA birds.  Current estimates are 75-90% of all animal species were killed on this really, really bad day for our planet.

A lot of plants died out, but some survived.  Many species non-flowering plants were wiped out, and many flowering plants were killed off. Post-impact ecosystems were dominated by angiosperms.

(We have little information about the microme.  Presumably, many species of microbes went extinct at that time, but these lines probably recovered quickly.)

(Ditto for insects.)

This fall researchers at Bath and UNAM report a statistical study of fossil plants from the Cretaceous forward [2].  The basic idea is a Bayesian estimate probably extinction rates for high level lineages, based on the genomes of existing plants.

The fossil record is sparse and geographically biased, and it is especially difficult to classify plant species based on fossil remains.  (Classifying plants by appearance without genetic information is always problematic.)  There are hundreds of thousands of plant species today, and the phylogenic tree is complex.  In sort, estimating the evolutionary history of plants back into the Cretaceous is difficult.

The study considered two (of many) genetic families, and tested Bayesian models for extinction rates. These datasets are built from analysis of existing plant genomes, from which family trees are inferred [1]. 

The basic finding—at least for these two groups—shows no evidence of mass extinction at the K-Pg boundary. 

The fossil record shows extinction of non-flowering plants after the impact.  It also shows short term, local die outs of flowering plants (angiosperms).  The new findings suggest that many species of angiosperms went extinct at that time, but families survived and thrived.

“The angiosperm fossil record reveals a high rate of species turnover (which entails elevated species-level extinctions) across the K-Pg, but without loss of Cretaceous higher-taxon diversity”

([2], p. 3)

The researchers hypothesize that angiosperms diversified in the Cretaceous, spreading widely and in many environments.  The Chicxulub impact surely wiped out many plants over wide areas.  But there were so many species of plants that families survived and radiated after the event, rapidly spreading everywhere.

The researchers point out that the definition of the concept of “mass extinction” is ambiguous and can depend on how they are measured.  Generally, mass extinctions are recognized by high loss of species diversity, which happens when entire taxonomic groups disappear. But their study shows that “high extinction rates at the species level can be disassociated from the loss of entire taxonomic groups.” ([2], p.4)  I.e., there can be massive losses of species, but the family can persist.

Is this a mass extinction, or not?  Or something in between?

In any case, assessing a mass extinction needs multiple lines of evidence to get a more complete picture.

“One of the main problems when assessing mass extinction episodes is the definition of what these events entail, and how we measure them. Generally, mass extinctions are characterized and measured by high loss of species diversity that often follow the disappearance of entire taxonomic groups from the palaeontological record. As evidenced by angioperms, high extinction rates at the species level can be disassociated from the loss of entire taxonomic groups. The fossil record indicates that the K-Pg led to mass extinction at the species level, but with no taxonomic selectivity leading to the disappearance of major angiosperm lineages.”

([2], p.4])

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1. Jack Tamisiea, Wiping Out the Dinosaurs Let Countless Flowers Bloom, in New York Times. 2023: New York. https://www.nytimes.com/2023/09/12/science/flowers-dinosaurs-extinction.html
2. Jamie B. Thompson and Santiago Ramírez-Barahona, No phylogenetic evidence for angiosperm mass extinction at the Cretaceous–Palaeogene (K-Pg) boundary. Biology Letters, 19 (9) September 2023. https://doi.org/10.1098/rsbl.2023.0314

Dino v Mammal

Everybody knows that mammals lived in the shadows of the great non-avian dinosaurs before Chicxulub.  Mammals were small, creeping, nocturnal, egg stealers. 

But, of course, there were lots of mammals and lots of dinosaurs and lots of time.  So, who knows all the ways these animals interacted?

This summer researchers from Hainan and Canada report an astonishing fossil from the Yixian Formation, which appears to be a fight to the death between a mammal and a dinosaur [2]. Whoa!  

“The entombed individuals represent the small ceratopsian dinosaur Psittacosaurus lujiatunensis entangled with the even smaller gobiconodontid mammal Repenomamus robustus”

([2], p. 3)

The two skeletons are nearly complete, and they are coiled around each other.  Not only that, but they are biting each other! In fact, the researchers hypothesize that the mammal is attacking the dinosaur! Chomp!   

The natural interpretation is that these animals were fighting and were caught in a sudden volcanic event which rapidly buried them, preserving them together.

This fossil is amazing!  But is it too good to be real?

This kind of Hollywood find is often a fake, assembled into a cool story from separate fossils.   There have been fakes as long as fossils have been studied, and the researchers were properly skeptical.  One of the neat things about the paper is the careful analysis of the authenticity.

The rock matrix does seem to be from the specified location, and both skeletons are embedded in the stone together.  The team exposed one of the teeth still in the matrix, and found it was, indeed, embedded in the rib of the antagonist.

As Dr. Jordan Mallon put it, if it’s a fake, it’s “the best I’ve ever seen.” (quoted in [1])

Wow!

Now I would expect a version of this scene to show up in the next Jurassic Park sequel, “Jurassic Park: The Rechompment.  Did you call me an “egg stealer”?”

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1. Kate Golembiewski, This Fossil Is a Freeze-Frame of a Mammal Fighting a Dinosaur, in New York Times. 2023: New York. https://www.nytimes.com/2023/07/18/science/dinosaur-fossil-fighting-mammal.html
2. Gang Han, Jordan C. Mallon, Aaron J. Lussier, Xiao-Chun Wu, Robert Mitchell, and Ling-Ji Li, An extraordinary fossil captures the struggle for existence during the Mesozoic. Scientific Reports, 13 (1):11221, 2023/07/18 2023. https://doi.org/10.1038/s41598-023-37545-8

Zaria Gorvett on Dinosaur Sex

In my lifetime, we have learned a ton of stuff about dinosaurs, including stuff that was “impossible to know” according to my grade school text books.  We have discovered fossil traces of footprints, poop, and other stuff that show us dinosaurs on the move.  We have found not just eggs, but nests and nesting colonies.  We have found fossilized soft tissue, including skin!  We have the first notions of what dinosaurs looked like and sounded like.

But, as Zaria Gorvett reported last year, “The sordid details of how dinosaurs got it on have long eluded scientists.” [1]  The fact is, we can’t even tell boy from girl dinosaurs, let alone how boy-met-girl might have worked out, Jurassic style.

Given their descendants, and the fact that there were a lot of dinosaurs for a long time, “one thing is certain: they would have been doing it.” [1]

Gorvett reports on a relative handful of fossils that may have caught dinosaurs in the act, including a pair of Tyrannosaurs (with feathers!) from a lake bed in China.

And then there is the Psittacosaurus, whose cloaca was preserved in death.  In fact, there seems to be evidence of visual marking around the cloaca, which could be interpreted as sexual signaling.  If so, then it suggests that these dinosaurs relied on sharp color vision.  Because, why show off your bottom, unless the boys will be able to see it, and will be interested to see it.

Suggestive, but without further examples, it’s hard to be very sure about exactly what they had and how they used it.

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On the other hand, we have a lot of examples of interesting visual features—including spikes, sails, and head crests.  In the absence of other evidence, these features are often hypothesized to be forms of social or sexual signaling.  Perhaps the spectacular shields of Triceratops are displays to attract mates?

In the case of contemporary animals, many flashy features are interpreted as social and sexual signals.  This is a very tricky scientific case to make.  From living animals that we have observed for many years (Red-winged Blackbirds come to mind), we know that animals do use visual and audible displays.  And it is possible to create a strong case that these traits are sexually selected—i.e., the most successful display gets the mate, and passes on his or her genes.

But in the absence of behavioral observations, arguments about possible sexual selection are speculative and often pure fantasy. 

Since we have so little information about dinosaurs, pretty much every theory about behavior is speculation.

Gorvett discusses some of the logical guidelines for sifting the evidence.

In contemporary animals, sexual dimorphism is a big give away.  Showy features in one gender but not the other are likely liked to sexual display.  Furthermore, sexual displays often develop at maturity, which is another strong hint.

Unfortunately, we have no secure knowledge of dinosaur genders, and only shaky knowledge of dinosaur growth and maturation.  So…not much help.

The basic criteria remains:  a feature that has no known evolutionary advantage is a candidate for social or sexual display.

So there has been a lot of examination of, say, Tricerotops crests, to see if they have a role in thermoregulation or defense, for instance.  A lot of this can get pretty speculative.

One of the more interesting areas has been discovery of traces of behavior that appear to be related to sexual competition. There is evidence of Anky fights, and similar evidence of Tricerotops on Tricerotops fights.  These behaviors would, presumably, be similar to contemporary species where males joust for dominance, which is believed to select for “better” equipment in the form of antlers, plumes, and whatever.

There is even evidence of ostrich-like “scrape-ceremony” behavior, in which prospective mates demonstrate nest digging to win favor. [2]

This is an example where the complexity of contemporary bird behavior suggests the potential of their dinosaurian ancestors and cousins.  There is a huge, indeed, preposterous range of mating behavior in our contemporary dinosaurs, so it makes sense to think that their ancestors did such things, too.

On the other hand, bird behavior is too complicated, and too weird, to help too much. Avian behavior is so varied, and even closely related species are so different, that it’s impossible to predict much about the behavior of an unknown species.  They might do anything!

So, basically, reasoning back from contemporary feathery dinosaurs tells us: ancient dinosaurs might have done practically anything.

So, the theme is, “why not?”

“[I]n recent years we have gained many previously unimaginable insights into dinosaur lives – who knows, perhaps in a few decades we’ll all know an uncomfortable amount about the perverted ways they courted – and yes, what kind of genitals they had.” 

(from [1])

Well, I don’t know about “perverted”. Steamy, perhaps.

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1. Zaria Gorvett, The mystery of how dinosaurs had sex, in BBC News – Future, June 29, 2022. https://www.bbc.com/future/article/20220629-the-strange-search-for-dinosaur-genitals
2. Martin G. Lockley, Richard T. McCrea, Lisa G. Buckley, Jong Deock Lim, Neffra A. Matthews, Brent H. Breithaupt, Karen J. Houck, Gerard D. Gierliński, Dawid Surmik, Kyung Soo Kim, Lida Xing, Dal Yong Kong, Ken Cart, Jason Martin, and Glade Hadden, Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs. Scientific Reports, 6 (1):18952, 2016/01/07 2016. https://doi.org/10.1038/srep18952

Dinosaurs Got So Big

(Straight man: “How Big Did They Get?”
Comedian:  “They Got So Big … 
[I don't know what the punch line is....])

One of the many, many cool things about dinosaurs is how freaking big they got.  Much bigger than contemporary land animals, or anything seen since. Only the ocean giants are in the same class today.

It’s really a mystery.  Why did the top end dinosaurs get so much larger than today?  I’ve seen various hypotheses, but no one really knows.  For that matter, how did they get so big?  How could they grow from an egg to the size of a building in a single lifetime? How could they get enough food?  How could they even stand up, let alone move around? 

This spring Kamala Thiagarajan discusses another question:  why weren’t they even bigger? [1] If we don’t know how and why they grew large, then we don’t really know if the ones we know were the maximum possible, or whether they could, in principle, have grown even bigger. If the Chixulub impactor had missed, maybe even larger variante or species might have emerged.

There were a lot of large dinosaurs, of course, as long ago as the Jurassic period.  Titanosaurs lived in the Cretaceous, and were even larger than their Brontosauran ancestors, which is an additional mystery.  Why would getting even bigger be adaptive?  Were there new factors in the Cretaceous favoring gigantism, such as new food sources?

Since we don’t really know why Titanosaurs grew so much bigger than their ancestors, so it is possible they might eventually have evolved even larger.  On the other hand, Titanosaurs were around for quite a while before Chixulub (likely more than 100 million years), so what we see may be pretty near the limit. 

And there are plenty of reasons why there might never be land animals larger than Titanosaur.  For one thing, the ones we know of are “impossible”—intuitively, they are far too big. 

They are as big a whale, but don’t live in water to help support their weight.  It’s hard to imagine how they managed to move around. They must have had to eat insane amounts of vegetation to survive.  They must have grown really fast for many years.  

It all seems so impossible.

Yet, they really lived. : – )

My own intuition is that the Titanosaurs we know of are near the limits. 

We know what the challenges and costs of getting even bigger would be.  Gravity is gravity, and flesh is flesh.  Land animals have to fight gravity and have to be able to move.  They have to stand on the ground, which can only hold so much weight.  They have to grow up from an egg in one lifetime. 

We don’t know what the advantages of being even larger might be.  Would they be even safer from predators?  Would they ge able to access even more or alternative food?  Would they live even longer and lay even more eggs?  Who knows.

So, basically, I can’t really make an evolutionary case for super-titanosaurs.  In fact, I would guess that in many environments there would be adaptive pressures to get smaller.  As Titanosaurs moved into places with limited resources, the logic of “island” evolution would push for smaller body sizes. 

But, who knows?  I guess I won’t be completely surprised if yet another, even bigger, Titanosaur is discovered tomorrow because there is so much we don’t know.

(Gosh, I love dinosaurs!)

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1. Kamala Thiagarajan, Could dinosaurs have grown any bigger?, in BBC News – Future, April 5, 2023. https://www.bbc.com/future/article/20230405-did-the-dinosaurs-reach-their-maximum-possible-size

T. Rex Lips?

We all know what T rex looked like, because we’ve seen them in movies and comic books.  OK, the reconstructions have evolved over the last century, and there is that slight dispute over whether they had feathers or not.  (Feathers?  On the fiercest monster ever?  That’s hard to swallow.)

But, rexie is always shown with a full set of dagger-like teeth, fully visible. So it must be true.

This spring, an international team of researchers report a study of T rex facial anatomy [1].  They analyzed the anatomy of different species of reptiles, including crocodylians, Komodo dragons, and Tyrannosaurs.  They find that rexie is similar to Komodo dragons, and argue that Tyrannosaurs also had lips over their teeth.

This is consistent with the observation that T. rex teeth seem to have equal wear on inner and outer sides, unlike crocodylians which are more worn on the exposed outer side.

The researchers argue that lips keep tooth enamel wet and strong.  Exposed teeth tend to become brittle, as well as exposed to damage. Notably, crocodilians which have exposed teeth are also aquatic, so the exposed fangs will not dry out. 

Their new reconstruction makes a Tyrannosaur look a lot like a big lizard—which it was. 

I gather that this hypothesis is not universally agreed [2].  It is based on indirect evidence and somewhat speculative hypotheses.  To date, no soft tissue from a Tyrannosaur face or lips has been discovered.  So, we don’t really know.

This hypothesis seems plausible to me.  Most animals have lips, especially land animals.  And this would not be the first case where reconstructions based on spectacular looking skulls with big teeth and no lips, were misleading.

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1. Thomas M. Cullen, Derek W. Larson, Mark P. Witton, Diane Scott, Tea Maho, Kirstin S. Brink, David C. Evans, and Robert Reisz, Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology. Science, 379 (6639):1348-1352, 2023/03/31 2023. https://doi.org/10.1126/science.abo7877
2. Jack Tamisiea, Imagine T. Rex. Now Imagine It With Lips., in New York Times. 2023: New York. https://www.nytimes.com/2023/03/30/science/lips-tyrannosaurus-rex-dinosaur.html

Songs of the Ankylosaur?

“Ankylosaurs are weird”

(Professor Julia Clarke quoted in [1])

Birds, AKA avian dinosaurs, are famous singers. But what about their non-avian cousins, AKA dinosaurs?

We do have evidence from remains of dinosaur ears, which certainly suggests that many dinosaurs could have heard many kinds of vocalizations.  But for all the fossils of non-avian dinosaurs, there has been no direct evidence of vocal organs, and only one voice box for an avian dinosaur has been identified. 

This winter researchers in Japan report a fossilized larynx from an ankylosaur (Pinacosaurus grangeri) [2].  The larynx is similar, though larger, to that found in other animals.  They suggest that it might have been used for vocalization.

Who knows?  

This larynx did control the airway, and the ankylosaur probably had lungs similar to birds.  But, birds don’t vocalize via their larynx, they have a separate organ for that, and crocodiles vocalize in different ways, too.

So maybe.

In any case, an animal as large as an adult anky would not be chirping and cooing.  It would be humming and hissing, possibly very loudly.  But who knows what sounds anky might have been able to make?

Now, baby dinosaurs are a different story.  Baby crocodiles chirp, and their parents can hear them.  The ears of many dinosaurs suggest they could hear chirps, so it is very possible that nestlings vocalized and caretaking parents listened to their chirps and coos.

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For whatever reason, this seems to be the season of the ankylosaur, with new findings rolling out.  Anky camouflage schemes!  Anky tail club fighting!  And now, the songs of the Anky! 

C’mon!  Anky’s aren’t ‘weird’, they’re cool!

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1. Carolyn Wilke, What Sounds Did Dinosaurs Make?, in New York Times. 2023: New York. https://www.nytimes.com/2023/02/24/science/dinosaur-sounds-fossils.html
2. Junki Yoshida, Yoshitsugu Kobayashi, and Mark A. Norell, An ankylosaur larynx provides insights for bird-like vocalization in non-avian dinosaurs. Communications Biology, 6 (1):152, 2023/02/15 2023. https://doi.org/10.1038/s42003-023-04513-x

Dinosaur Path Lab

While the fossil record will always be sparse and unevenly distributed, where we do have fossils we sometimes have a lot of fossils.  So we are learning that some dinosaurs lived in herds, and nested in groups.  And we are learning about the life cycle of individual animals, as they grow from tiny hatchlings to behemoths in a relatively short time. And so much more.

Large caches of fossils also open the possibilities of finding rare specimens, including, notably, cases of visible diseases. 

This winter, Jocelyn Timperley discusses the emerging field of palaeopathology, which has found evidence of familiar bone disease, fungal infection, and cancers in dinosaurs and other ancient animals [2].

The evidence is, of course, exceptionally rare.  Most diseases leave no fossil remains, and microscopic traces would rarely be noticed even if they are present.  In addition, an abnormal fossil might or might not reflect a disease, so the evidence can be very ambiguous. 

Diagnosing ancient cases based only on bones is challenging even when the fossil bone is complete and histology can be done.  We know nothing of the physiology of the animal, and have no direct observation of microorganisms present, so many conventional data used to corroborate a possible diagnosis are unavailable.

Given the challenges, it is remarkable that a number of cases of cancer and other specific diseases have been clearly identified from ancient fossils. 

One of the interesting findings is that these maladies are similar to contemporary diseases.  Cancer, arthritis, and fungal infections that plagued dinosaurs plague humans today have been confirmed in dinosaurs and ancient animals.   At the very least, these findings show that these pathologies have long histories, and seem to affect a broad range of species. 

This may offer insights into the origins and nature of these diseases.

For example, I note that a bone cancer in a dinosaur is not likely caused by human activity such as industrial pollution, is it?  And if a dinosaur is infected by a fungus that we still see today, we understand that this fungus had a long evolutionary history before it ever met a human, and that the infection strategies probably have been around for millions of years before humans.

Also, by the way, we note that even the mass extinction following the Chicxulub impact did not kill off these surviving pathologies.  This reminds us that the concept of “mass extinction” often leaves out microbial life, including parasites and infections fungi, though, of course, they are a part of “all life on Earth”.

It seems likely that we may discover that dinosaurs and other ancient life had pathologies we no longer see.  Some diseases may have been specific to ancient species, and some we may not even recognize by their traces, should we encounter them.  Indeed, in at least one case, researchers have identified lesions that are probably traces of disease, but no one knows what the disease is. Whatever it is, it isn’t seen today.

An unknown or unrecognized pathogens might be considered to have gone extinct with their hosts, part of the mass extinction.

Timperley’s article was mainly interested in animals, but I bet there is similar information in fossil plant remains. 

Timperley also notes that diseases may reveal more about the life and death of ancient animals than just which individual had cancer.  For example, the Centrosaurus diagnosed with cancer was found in a bone bed that contained hundreds of animals [1].  This bed is interpreted as a Centrosaurus herd who died together in a catastrophe.  If so, then one of them was dying with advanced cancer, and would surely have been easy pickings for carnivores.  Yet he or she was still with the herd when the flood hit.  This suggests that the herd may have protected sick individuals as some contemporary herd animals do and some don’t.

So, Centrosaurus might have behaved something like zebras.

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1. Seper Ekhtiari, Kentaro Chiba, Snezana Popovic, Rhianne Crowther, Gregory Wohl, Andy Kin On Wong, Darren H. Tanke, Danielle M. Dufault, Olivia D. Geen, Naveen Parasu, Mark A. Crowther, and David C. Evans, First case of osteosarcoma in a dinosaur: a multimodal diagnosis. The Lancet Oncology, 21 (8):1021-1022, 2020/08/01/ 2020. https://www.sciencedirect.com/science/article/pii/S1470204520301716
2. Jocelyn Timperley, The ancient diseases that plagued the dinosaurs, in BBC Future, February 14, 2023. https://www.bbc.com/future/article/20230214-could-dinosaurs-get-cancer