The Age of Reptiles mural at the Peabody Museum is basically right. Read left to right, you get Triassic human size dinosaurs, Jurassic giants, and the brutal world of big teeth and thick armor of the Cretaceous. They all got fucked up by volcanoes, asteroids, and global warming and died dead. But it lasted about 900 times longer than human existence so far.

I wanted a contemporary book on dinosaurs. The Rise and Fall of the Dinosaurs was pretty good!

If there is a thesis, it is that the “most successful” species (or clade) may have a good run for millions of years, but will eventually be victims of their own success. They die out (more or less) and are replaced by descendants of a species (or clade) that was previously not a big deal kind of creature. Number one today will always fail.

What “dominant” or “successful” means is totally unclear, but let’s return to that later. This is a popular science book! It’s thesis doesn’t have to make much sense! It gets the people going.

This book has two kinds of content: stories about the work of research and theories about the subject matter. Both are pretty good.

The Work of Research

“Dinosaurs” are only really known through scientific research! Brusatte emphasizes the diversity and quality of this work, often spotlighting friends. Brusatte himself has made substantial efforts to share this research, as a consultant for Walking with Dinosaurs, a player in T. Rex Autopsy, and his popular writing in books, Twitter and elsewhere. Here he has the chance to give an interested audience a deeper dive into how we know dinosaurs.

Romance of Research

At some point in this book project, it must have become clear that the research needed more romance and allure. And so we we get tasty little vignettes, such as this on an assistant at a dig:

His name — Helmuth Redschlag — conjured up images of an imperial Prussian general, but he was from Middle America, and his job was much more sedate: he was an architect. Each night he partied deep into the morning with his friends — feasting on filet mignon and imported Italian cheeses, sipping fruity Belgian beers to the disco trash beat. Still, every morning he was up at six A.M., eager to head back into the furnace of Hell on the trail of dinosaurs. (236)

Brusatte tells us that most academic paleontologists wear plaid and have beards (so most are men?), but some are goth or ravers or DJs or hipsters or aristocrats. But he tells this in pretty little stories. His most loving details are saved for friends and the fantastic personage of Baron Franz Nopcsa von Felső-Szilvás.

The Baron was an inspiring aristocrat chasing about at the periphery of history, exploring Albania and island dinosaurs.

Many Methods

Romance aside, Brusatte reveals the vital network of fellow academics who he considers worth citing and are doing good work of various kinds. He tells us about a researcher who just receives images of flattened fossils and analyzes them at a computer. A researcher who builds mechanical simulations of materials and force to infer resilience, size, and pressure. A researcher who collects all kinds of things in the rural area where he grew up — dinosaurs as well as arrow heads and old mining tools. We learn of Chinese professionals with incredible access to new fossils. We learn who has an MRI, where they got it, and what they use it for. We even learn about someone’s idea to look at the microbiology in fossils which lead to the discovery that you can sometimes tell what colors dinosaurs were.

Brusatte shows how the object of knowledge emerges in increasing detail through the application of various ways of knowing. The T Rex, for example, is the best studied of the dinosaurs, and Brusatte points to specific methods that have brought to light various aspects of the creature.

In his own work, Brusatte tends to collect new fossils and to track similarity between species’ anatomy. His technique involves coding body features (such as a specific bone’s position) as a binary, then then making associations between many species to determine clustering and likely shared ancestry.

Something great about these methods is that none are flawless. They are all speculative and create approximate findings that are still very useful. For example, one researcher making models of body and movement found that a mature T Rex would have a maximum running speed of 10–25 mph. That’s not very specific! But it gives us an important maximum and excludes the possibility that the mature Rex chased down its meals or could catch you fleeing in a jeep.

Money

Although the topic gets very few lines, Brusatte does mention the money. While higher education funding tends to depend on who can use grant outputs for what, and thus who gives grants for what, paleontologists still somehow get funding for dinosaur research. A separate estimate puts total grant money for dino research in the US at under $20 million per year.

Much more money, however, is available for invertebrate paleontology; this is really oil money. Find the ancient worm or gooey sea creature fossils, and you can find fossil fuels! This proximate field probably assures that those interested in paleontology but motivated by money will leave the field, leaving it to die-hards. Presumably die-hards with a solid sense of financial security, such as educated members of whichever national majority.

Brusatte illustrates the character of fossil hunters, including the comment on one compatriot that, “once I saw him push his way through rapids on a broken foot because he saw a bone sticking out of the opposite riverbank” (260).

Popular Science

The book has an evolutionary focus, but isn’t too constrained by a focus and instead eagerly presents any bits of science that looks nice and seem reliable. The overarching theme if that when a species starts doing well, it gets too big and becomes vulnerable, then fails. Another cockroach species rises up quickly.

Dominating the Countryside

But what is this definition of “doing well” or “success?” Humans today make up less than .1% of earth’s biomass, yet 20% of all life on Earth is harvested for their consumption. Plants make up 80% of the biomass of Earth, yet we rarely refer to them as dominant.

In what sense, then, was the Mesozoic the “Age of the Dinosaurs?” In Cretaceous North America, “where T Rex ruled,” was this predator much more important than lions in the savannah or sharks in the ocean? Is learning about lions a good way to get to know the savannah? Identifying an era with its most notable leadership, in human historiography, is sometimes called the “great man theory.” It claims (usually implicitly) that a few important people are what you need to know about an era. And in almost every case, this theory is wrong. Einstein, Washington, Edison, and Steven Jobs were all rather small parts of much larger historical processes.

So that is probably how we should see the dinosaurs. They are interesting to think about and are no less important than the archosaurs or mammals or protosuchidae that preceded or surrounded them. But the Jurassic is no more “the era of dinosaurs” than the US is “the country of Christians.”

Dino Historiography

Brusatte uses the periods of the Mesozoic to frame the rise and fall of dinosaurs.

Artists rendering of a dicynodont. They’re cute, I think. Proto-mammalian and proto-reptilian, they held dominant niches in the ecosystem for a while.

During the Permian era there were lush rain forests all over Pangea. With a rise of volcanic activity and a minor ice age, they became splintered into little islands of rainforest, which created diversity because one species no longer traveled freely. During this period, there were archosaurs, which included early dinosaurs, but the large-bodied charismatic predator and primary producer roles were held by salamanders and other weird shit I don’t know much about.

Typical pseudosuchians

Honestly, archosaur and pseudosuchian body shapes aren’t that different from dinosaurs, but they didn’t get that big and, arguably, they were straight up less evolved, with simpler bones and organs and so forth. Brusatte mentions this as an aside, but the earliest forms of multi-cellular life were “soft sacs of good like sponges and jellyfish” (20). So it might be fair to character earlier life as less evolved than later (on the geological time scale). Anyway, life got onto land 390 million years ago and the Permian is where they were 100 million years later.

The Permian ended with volcanic activity getting way out of hand, torching forests, kicking off runaway global warming, and culminated in the extinction of 96% of all then-living species. It was awful.

Metoposaurus is a salamander about 9' long that ate small dinosaurs who came near the shore.

The Triassic is technically the beginning of the Mesozoic, the “age of reptiles,” but life took a few million years to recover after the end of the Permian and dinosaurs were not a big deal globally during the Triassic. Pseudosuchians evolved larger bodies and became common. Dinosaurs during this time were mostly small and not really ready for TV or movies yet.

Pangea had partially split into Laurasia and Gondwana. Dinosaurs mostly lived in Gondwana, unable to cross the equatorial desert and deterred from the seas where other predators would gobble them up. Geographic fragmentation is pretty important in evolutionary history, as it is in political history.

In one part of what is now Argentina, dinosaurs made up to 30% of the ecosystem. These seem pretty satisfying so we shouldn’t knock the Triassic on content, but these dinosaurs were no T Rex. I know that seems real choosy and we should recognize these dinosaurs are cool, but the basic claim of dinosaur enthusiasm is that dinosaurs are substantially more awesome than salamanders, archosaurs, pterosaurs, angiosperms, etc.

Dinosaur reconstruction in Ischigualasto Provincial Park, Argentina.

The Triassic ends with a bang. More volcanic activity accompanied by climate change. 30% of species extinct and 95% of plant life dead. 3000' deep lava flows remained when it was done (87–95). Pretty brutal, Earth!

The Jurassic follows and, again, life takes a while to rebuild. Brusatte’s basic theme returns here: when life came back, the top niches were now filled with a new animal. Pangea was splitting apart and dinosaurs got past the equator and became common many places. In particular, this is the era for massive sauropods. In general, you see larger dinosaurs more commonly during this era, including stegosaurs. You can even see it in the Zallinger mural at the top of this article.

This is just such a cute picture, let’s pretend the sauropods in Scotland looked like this and were so romantical!

The transition into Cretaceous from Jurassic isn’t marked by any massive event; it’s just a convenience for classification. The very large sauropods went extinct, though the reasons are unclear. Brusatte points out that the ecological niche supporting these creatures is not common or stable! Theropod diversity increased during this time and they took on more interesting diets, such as eating seeds.

The continents during the Cretaceous were approximately here.

The Cretaceous is also the period of dinosaur history with the most distinct land masses. At the same time the Tyrannosaurus Rex took the top predatory niches in North America, the Carcharodontosaurus dominated South America and winged dinosaurs rose up in Asia.

The dinosaur party ends with a mass extinction. A big rock from space, loaded with iridium, landed at Chicxulub, triggering volcanoes on the other side of the planet, blasting dust to block the sun for a while, and starting fires from superhot debris raining down for quite some ways. The book isn’t very precise on how this “fall of the dinosaurs” happened, but does point out that their total extinction likely took a few thousand years and that the birds are definitely dinosaurs so they’re not all dead are they.

This timeline is a helpful framing for Brusatte to introduce meaningful distinctions and say which dinosaurs are like which others and what they did. I know it seems like a lot of mass death but this dinosaur party lasted 185 million years and Rome only half a thousand. All of human existence is maybe 2 million years and civilization only a few thousand, so the “reign of the dinosaurs” should be thought of as 90 times more stable than that of humans and they only experienced 2 periods of major climate change!

Some Salient Body Features

In addition to reviewing the basic history, Brusatte nerds out on the beauties of polymorphous dinosaur anatomy.

Armor: ankylosaur had a lot of this. It’s thick bone and it blocks attacks pretty well. T Rex could bit through it, but otherwise the (probably quite dumb) ankylosaurs did well with this armor.

Incredible growth rates: sauropods developed this to get really big, but their progeny inherited the capacity, and did you know that Tyrannosaurs are related to sauropods?

This chart is too small, but the point is that Tyrannosaurs grow really really fast. They reach full size in 25 years and start smaller than a basketball.

Breathing: this is a major limiting factor on body size because animals need respiration for their metabolism and it’s hard to scale up your in-breaths with body size at a certain point. The sauropods developed air sacs and passed the feature on to the T Rex. This is where birds got the air sacs too.

Another weak diagram, but it’s your best shot at learning quickly about air sacs.

Shedding heat: another limit on metabolism for a large animal, but the air sacs really help. Otherwise, you have declining surface area to volume ratio with larger bodies and cooling is a big problem.

Feathers: I am totally shocked by this, but “feathers are nature’s ultimate Swiss Army knife, multipurpose tools that can be used for display, insulation, protection for eggs and babies, and of course, flight. Indeed, they have so many uses that it has been difficult to figure out which purpose they first evolved to serve and how they were modified” (292). So dinosaurs probably had feathers from the Triassic on, but used them mostly for display, defense, and temperature control (296)! The feathers were psychedelic colors(297).

Body size: this is another interesting feature because it opens up new niches for a species. It’s hard to tell exactly how big an animal was from a partial skeleton, but there’s a fairly consistent ratio with the diameter of the main support bone for its legs. Or you can try to make a complicated 3D model on a computer. Realistically, this is the single most important feature in getting the public excited about dinosaurs, mostly because it isn’t a very dominant strategy on the land today. In the ocean, though, being really big works pretty well these days.

Feeding parts: the teeth are normal to talk about, but the neck is also important and the bones of the jaw, which can indicate how the animal feeds. The Allosaur attacked using its head as a hatchet (137), the Triceratops really just had 2 long blades on the upper jaw and two below, taking cuttings from plants and swallowing them (239). The T Rex does something super intense called “puncture pull” feeding, where it stabs its teeth deep into an animal, then holds down and pulls! Those teeth stabbed through bones.

Spotlight on T Rex

Brusatte gives us a whole chapter on this one dinosaur. The Rex is actually very well studied, with 50 bodies found and very research method applied to it. Brusatte defends Rex as the most massive pure meat eater of all time, though there are many other contenders. The Rex jaw was strong enough to bite through a car, based on a study of a stegosaur body with teeth stuck in it. Juveniles may have been fast runners, but mature Rexes definitely could not run 25mph. Some evidence suggests they hunted in packs, probably of different ages (combining size and speed). None have been found that were over 30 years old. (You can infer age from rings in the bone, as the animal will grow more in one season than another so the bone’s growth is visible).

Birds are Dinosaurs Too

Brusatte is quite compelled that birds are dinosaurs and are not just descendants of dinosaurs, because they can be classified fully within the family tree of dinosaurs. I wasn’t won over by this, but don’t have strong feelings on taxonomy. His basic point is awesome: the birds are drawing on a rich feature set that they inherited for rather arbitrary reasons!

Todays’ birds stand out among all modern animals. Feathers, wings, toothless beaks, wishbones, big heads that bob along on an S-shaped neck, hollow bones, toothpick legs … the list goes on. These signature features define what we call the bird body plan: the blueprint that makes the bird a bird. This body plan is behind the many superskills that birds are so renowned for: their ability to fly, their hypercharged growth rates, their warmblooded physiology, and their high intelligence and sharp senses. 284

In 1861, an archaeopteryx fossil was found that provided the first evidence of a missing link between dinosaurs and birds, really helping out defenders of Darwinism at a difficult time. This little dude (raven sized) could probably glide but not really fly.

Almost all of these critical avian features actually developed in dinosaurs for quite different reasons! The legs with skinny toes appeared very early in dinosauria, with early bipedalism used to run fast and hunt things. Little details like sleeping posture and the harvesting of bone calcium to create eggs developed in dinosaurs, and then were put to use by birds.

The transition from dinosaurs to birds began with many new dinosaur species making use of feathers for short bursts of flight and ended when certain species (probably several!) started being able to make true flight work. This was a watershed moment and the pace of evolutionary change quickened soon after, yielding avians from dinosaurs in a relatively short period of time (a few million years).

Hey, birds

Conclusion

Ok, so subtext. Humans are “dominant” today by similar standards and, if we’re studying kings and top predators, humans can be expected to falter at some point in the next, say, 30 million years and get replaced. Climate change and impact winters are a normal part of life on Earth, though usually don’t cause extinction over night.

Broadening our perspective, the book is really about niches in a changing environment (climate and geography) and the animal features that enable certain kinds of organism to occupy and maintain in a niche. I didn’t mention this, but Brusatte also emphasizes that diversity yields resilience, so you should consider how this process happens with multiple species representing!

It’s kind of a bummer that dinosaurs all died from an asteroid (or comet or something) impact, but it’s nice to imagine that this may also have been how life came to Earth at all.

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