Palaeontology – Hoopoe – A blog by nhbs

Book Review: The Last Days of the Dinosaurs

*****A unique on the story of dinosaur extinction and its aftermath

The day an asteroid slammed into the Yucatán Peninsula some 66 million years ago is a strong contender for “the worst day in history”. The K–Pg extinction ended the long evolutionary success story of the dinosaurs and a host of other creatures, and has lodged itself firmly in our collective imagination. But what happened next? The fact that a primate is tapping away at a keyboard writing this review gives you part of the answer. The rise of mammals was not a given, though, and the details have been hard to get by. Here, science writer Riley Black examines and imagines the aftermath of the extinction at various times post-impact. The Last Days of the Dinosaurs ends up being a fine piece of narrative non-fiction with thoughtful observations on the role of evolution in ecosystem recovery.

Before delving in, a brief word on what is not in the book. Black does not discuss the history of the research that discovered evidence of an asteroid impact, such as the iridium spike and the crater. Nor does she go into the ongoing debate on the relative contributions of the asteroid and Deccan Trap volcanism. Instead, Black’s approach is to imagine a day in the life of the survivors at various time points post-impact: after an hour, a day, a month, a year, a century, all the way up to one million years. She focuses on the Hell Creek formation in western North America as it offers one of the clearest windows into the mass extinction and its aftermath. Most chapters have a short coda that looks at how life was faring elsewhere on the planet. Black’s style of choice is narrative non-fiction: she is resurrecting individual animals and imagining their lives. As she explains in her preface, to allow full immersion, she is not interrupting the flow of her story with notes and references, which are found at the back of the book. An extensive, 58-page(!) chapter-by-chapter appendix reveals her process and discusses what we know, what is hypothetical, and where she has speculated to smooth over the gaps in our knowledge.

Barringer Crater in Arizona. — Barringer Crater by Simon Morris, via flickr.

Now, when this book was announced, just the prospect of dipping into the story of the disaster and the ensuing recovery already had me excited. However, The Last Days of the Dinosaurs surpassed even these expectations for two main reasons.

First, there are plenty of exciting new ideas and scientific findings here. Black’s interpretation of the impact will no doubt ruffle some feathers as it is particularly catastrophic. Forget the often-depicted idea of an asteroid seen streaking across the sky, Black writes, this thing came in fast at some 45,000 miles per hour (~20 km/s). Forget, too, the often-depicted drawn-out hunger winter for the surviving dinosaurs. I had not come across this idea before, but Black writes how a global heat pulse that lasted several hours fried anyone that could not crawl underground or stay submerged underwater. This is based on estimates of the amount of material ejected by the impact that, upon re-entry, heated the atmosphere to several hundreds of degrees centigrade. It would have ignited global wildfires. Finally, the impact injected vast amounts of sulfate aerosols into the atmosphere as the impact site was rich in calcium sulfate. The ensuing acid rain “might have effectively erased some of the slowly forming fossil record” (p. 256), explaining why fossils are hard to find in the layers around the K–Pg boundary.

Fossil of dinosaur jaw full of sharp teeth. — Fossil of dinosaur jaw full of sharp teeth by Ivan Radic, via flickr.

Regarding the survivors, Black has plenty of interesting ideas too. As seen at other times and other places, there was a fern spike. A rapid initial proliferation of ferns is frequently seen in devastated ecosystems where plants have died. And why did birds survive? One novel idea is that the survival of beaked, but not toothed birds is part of the answer. “Maintaining a mouth of sharp teeth comes with a reliance on animal food. […] A consumer that feeds on other consumers has very little to survive on now. But beaked birds do not face the same constraints” (p. 117). With the extinction of toothed birds and pterosaurs, the beaked birds were poised for an evolutionary radiation. Something similar happened with the mammals. Black prominently mentions the idea that Elsa Panciroli promoted in Beasts Before Us, that “it was competition between mammals that limited the number of different forms and niches Mesozoic mammals evolved into” (p. 158). With the extinction of more archaic mammaliaformes, the placental and marsupial mammals would flourish.

The second reason the book surpassed my expectations is Black’s reflections on the process of evolution and its role in ecological recovery. This is where her prose sings in places. One thousand years post-impact “[…] there is no script for what’s about to unfold, no cast of characters that inevitably must be filled” (p. 142). One million years post-impact a reptilian resurgence seems unlikely, but “the rise of the mammals is anything but assured […] When a global disaster ends one evolutionary dance, shifting the tempo, another begins, with no certainty as to who will lead” (p. 182). She poignantly notes how the fossil record “is not in any way a complete record of life on Earth. It is a record of fortuitous burials” (p. 254). And on the process of evolution, she writes how variation and happenstance provide “the raw material for natural selection and other evolutionary forces to shunt down different pathways. Not that there is any intent to this. It’s a passive state, a constantly running routine that is merely part of existence itself” (p. 196). This is music to my ears and Black’s writing is one of the highlights of this book.

Fossil of a dinosaur hand in a museum in sand. — Fossil of a dinosaur hand in a museum by Ivan Radic, via flickr.

Writing about such an iconic event carries the risk of intense scrutiny. No doubt, some experts and other palaeo-nerds will disagree with some of the details presented here. I think her appendix is sufficiently explicit about where she speculates and where she has chosen not to hedge her bets on different explanations. I was willing to read the book in this spirit, as one possible interpretation of how things might have unfolded, though one that Black carefully backs up with scientific evidence. My quibbles are rather minor instead. One is that the book has no index, the other is that there are no notes to the appendix. Relegating the discussion of the underlying science to the appendix is a defensible choice. But not properly referencing the studies mentioned here is, to me, a minor blemish on an otherwise excellent book.

If you have any interest whatsoever in dinosaurs and their extinction, this book comes highly recommended. Her take on the topic, dipping into the extinction and recovery at various moments post-impact, is novel. I am not familiar with other books attempting this. As a bonus, I expect that many readers will come away with a better understanding of the process of evolution.

The Last Days of the Dinosaurs is available from our online bookstore.

Book Review: Dinosaur Behaviour

**** Handsomely illustrated and accessible

Reconstructing how dinosaurs behaved from just their fossilised bones might seem like science fiction but is very much science fact. In Dinosaur Behavior: An Illustrated Guide, veteran palaeontology professor Michael J. Benton joins forces with palaeoartist Bob Nicholls to do what it says on the tin: write a richly illustrated introductory book on dinosaur behaviour that is well-suited for novices.

In Dinosaur Behaviour, Benton takes the reader through five main topics: physiology (which sets the pace for everything else), locomotion, senses and intelligence, feeding, and social behaviour (which includes courtship, reproduction, parental care, and communication). One or several ‘forensics’ boxes in each chapter introduce the basic gist of certain methods.

Reading through this book, it becomes abundantly clear that our understanding of dinosaur behaviour relies on two approaches. Though Benton does not mention it as explicitly as in his previous book The Dinosaurs Rediscovered, the first of these is new high-tech toys and tools. Examples include computed tomography (CT) scanners, normally used in hospitals, to make detailed X-ray scans of fossilised brains (so-called endocasts) and so determine brain anatomy. Or finite element analysis normally used in engineering to model forces and stresses on jaws and teeth and so determine e.g. bite force. The second approach is ‘old-fashioned’ comparative anatomy and ethology: it pays to have a good knowledge of natural history when you are a palaeontologist. One example is the histological study of fossil dinosaur bones. Cutting thin bone sections and examining these under a microscope shows that some dinosaurs closely resemble mammals and birds, supporting the idea that smaller species were endotherms (‘warm-blooded’, i.e. generating their own body heat). Or take the microscopic study of melanosomes (pigment-containing organelles) in fossil feathers to determine colour in life. A final example is the comparison of footprints made by modern running birds with fossil tracks to determine things such as gait and running speed.

If you are well-versed in (popular) palaeontology, much of what is presented here will be familiar. Even so, I picked up interesting titbits. One example is a recent study of Psittacosaurus that describes a cloaca, the multipurpose orifice also seen in birds where the digestive, urinary, and reproductive tracts all open to the outside world. This suggests that dinosaur sex, for at least some species, was a matter of the appropriately named ‘cloacal kiss’ rather than the brandishing of reptilian genitals. Other insights fell into the embarrassing ‘I should have known this’ category. We tend to think of walking on two legs as something advanced because our mammalian ancestors walked on all fours, but for dinosaurs, it was the reverse; they started out bipedal and quadrupedality only evolved later in e.g. the large sauropods. Particularly interesting is the study by Kat Schroeder and colleagues who looked at fossil communities of theropods and noticed a so-called carnivore gap: there is a lack of medium-sized ones in the fossil record, even though there are medium-sized herbivores. One explanation could be that dinosaur eggs had an upper size limit, meaning that young carnivores hatched small and had an awful lot of growing to do. As they did, ‘they passed through a whole range of feeding modes, each step along the way acting like a different species’ (p. 137), effectively plugging the ecological niche of medium-sized carnivores.

Despite the broad range of topics, there are some curious omissions. The chapter on feeding e.g. discusses jaws, teeth, and the use of isotopes to determine diet, but not microwear analysis of teeth. What I found most surprising is that Benton does not introduce the concept of trace fossils or ichnology, their study. Yet, examples such as trackways (some possibly showing long-distance migrations), coprolites (fossil poop), and nests are all discussed here. Another surprising omission is that the two-page bibliography does not include most studies mentioned in the text, even though it references other technical articles.

Dinosaur Behavior is mostly very suitable for readers with little to no background in palaeontology. Benton explains even basic terminology (physiology, cannibalism) as he goes, though there is the occasional curveball. One example is the morphospace diagram showing a principal component analysis on page 131, which, I hope those with a background in statistics will agree, is a rather abstract way of visualizing data that requires a bit more explanation than is given here. Though the book is published by Princeton University Press, it has been produced by UniPress Books who can be considered the spiritual successor to popular science publisher Ivy Press. What this means is that information is accessibly presented in bite-sized sections on one or several page spreads, with long sections further divided using subheadings. The downside is that this restricts how thoroughly topics can be explored. Leafing through e.g. Naish & Barrett’s Dinosaurs: How They Lived and Evolved shows more nuance in its chapter on behaviour.

Finally, I have to mention the excellent colour and black-and-white artwork by Bob Nicholls that livens up the text. I loved the drawing of courtship in Confusiusornis on pages 168–169. Despite the overlap in topic, this is all-new artwork compared to Locked in Time. Other diagrams have all been carefully designed or redrawn, using colours where appropriate. The only design element that did not work for me was the choice of sans-serif font which made e.g. the letters ‘a’ and ‘o’ hard to tell apart.

Serious palaeontology buffs might find the contents here somewhat superficial, but overall, this is a handsomely illustrated book that offers an accessible introduction suitable for novices and possibly even curious high-school pupils. It would also make for a great gift.

Dinosaur Behaviour: An Illustrated Guide is available from our online bookstore.

Author Interview with Thomas Halliday: Otherlands

Otherlands is the exquisite portrayal of the last 500 million years of life on Earth. Palaeobiologist Thomas Halliday takes readers on an exhilarating journey into deep time, interweaving science and creative writing to bring to life the unimaginably distant worlds of Earth’s past. Each chapter is an immersive voyage into a series of ancient landscapes, throwing up mysterious creatures and the unusual landscapes they inhabit.

Thomas Halliday has kindly taken the time to answer a few questions for us below.

Could you begin by explaining what you mean by ‘otherlands’? How did your fascination with these ‘otherlands’ begin and what drew you to write about this?

The word ‘otherlands’ came about in trying to come up with a title that reflected some level of familiarity and strangeness. It falls somewhere between the idea of something being ‘otherworldly’, but also recalls ‘motherland’ – a safe, familiar home. I think all palaeobiologists, whatever subdiscipline they are part of, have the shared goal of understanding how life used to be. Biomechanists might concentrate on the engineering of a skeleton to understand the behaviours it would have been capable of, and phylogeneticists are interested in how living things are related and changed over time, but all of it adds up into a picture of past life. I’ve always been more interested in big picture, ecological questions rather than the minutiae of anatomy – as important as anatomical knowledge is – and so writing through an ecological lens made most sense to me. In essence, it’s just putting down on paper what we as a community have discovered about life at different points, which is a useful exercise in bringing together science from groups who don’t necessarily read one anothers’ papers. I can’t visit these places except through some creative process – whether that’s a painting, an animation, or text. And I can’t paint or animate.

It is a great feat of work to bring Earth’s deep past to life and to render the unseeable things seeable through prose. How did you approach such an immense task from not only a literary perspective, but a philosophical and scientific perspective too?

Every site in the book has some kind of layout in my mind. It may be known to a fairly high degree of accuracy scientifically – the extent of the playa lake in Moradi, just over 250 million years ago in what is now Niger – is sketched out in papers on that site, so we can get an estimate of how big it was, and which way the water was flowing from. In others, our knowledge is a bit more generic but I have a mental map of where the different beats take place. The line of the story in each place moves through that space, which means that I can be consistent in timing, sights and so on. I think this internal consistency of a place is essential to making it seem immersive. Most of the actual visual descriptions of the animals and plants I use, though in my own words, are no more detailed or evocative than those of other writers, so if I have managed to create a better sense of things being ‘seeable’, as you suggest, then I think that it is everything else around it that make the scene believable. If the scene has been describing the smell of a limestone cave, that colours the subsequent description of the next animal, because mentally you begin to frame it as seen while emerging into the light. We experience an environment through all our senses, and so appealing to those other aspects of reality brings out the realness of an organism.

One of the things I most appreciated about Otherlands was how you focus on landscapes, the settings that are necessary for life to evolve, versus our society’s sensationalised image of the prehistoric world that typically conjures up images of monstrous creatures. What is it that draws us to the dinosaurs compared to the often forgotten plants, fungi, invertebrates and other species?

I blame Gideon Mantell. Well, not really, but the early pioneers of popular geology at the end of the 18th and beginning of the 19th century drew crowds because of the enormous creatures they could put on display. The first fossil animals to be displayed in sensationalist shows were mastodons – relatives of elephants – and giant ground sloths. You have to remember that this is a pre-Darwinian time, when extinction has only recently been recognised, and when the timescale of the age of the Earth is still very much debated. They drew in the crowds with claims of antediluvian monsters from some barbaric era, and I think a lot of the popular depictions of the past have remained since then. If you think of the most influential European and American artistic works featuring palaeontology over the last – Jules Verne’s Journey to the Centre of the Earth, Arthur Conan Doyle’s The Lost World, Disney’s Fantasia, all the way through the Ray Harryhausen B-movies to Michael Crichton’s Jurassic Park, there’s a common thread of violence and peril, which is undoubtedly a crowd-pleasing approach but doesn’t really reflect what biology is typically like.

That doesn’t quite explain why many fossil mammals or crocodilians, for instance, are poorly known by the public. Dinosaurs do have the advantage of being typically very large compared with the biggest land animals of today – and indeed the recent past – so if you’re going into a museum it’s a lot harder to miss the big Diplodocus than the display of fossil horsetails. There is something awe-inspiring in size, but I hope that people can take the time here to recognise the wonder in the very small things that are going around. I do of course have dinosaurs in the book, but because they have been covered so extensively, I didn’t want to deal with many of the clichés. There’s a dinosaur hunting for food, sure, but it ends in failure. The big tyrannosaur has a drink and scratches off some dandruff against a tree. There’s more to dinosaurs than violence.

I was struck by the level of detail that is revealed from the fossil record, to the point that we can know the presence of different types of insects based on the distinct ways in which they damage leaves. As you collated such an array of research for the book, were there any particular findings that captivated your imagination the most?

One piece of information that I really enjoyed learning about, just because of the implications throughout, was one that I picked up at a conference talk (and which has since been peer reviewed and published). Oviraptorosaurs are a group of dinosaurs that have been associated with nests for a long time. The name means ‘egg thief reptiles’ because it was initially assumed that they were eating the eggs, but more and more finds have accrued, including of parents sitting on the nests at the time of burial, that show that these are their own nests that they are caring for. We can reconstruct how the nests were built based on the arrangement of eggs and the nest mound – a ring of eggs was laid, and then buried, and another ring later added. But what is wholly remarkable is that we can chemically analyse the eggshells even now, and identify different isotopic ratios of calcium in each layer. The isotopic pattern is a sort of chemical signature that is tied to the individual mother that provided the raw material for the eggshell. What this means is that each nest contains the eggs of more than one mother. There are a couple of possible explanations for this, but the best modern example of communal nesting like this is in ostriches, where a single male builds and guards each nest, and several females lay eggs in the same nest. In ostriches, the males then rear the chicks once hatched – I don’t go so far as to claim this for oviraptorosaurs, as this could only be speculation, but I think the best examples of fossil record detail are those where a preserved detail of chemistry opens up a whole trove of behavioural implication.

Thomas Halliday. Credit: Desiree Adams, Penguin Random House

Scientist Robert H. Cowie writes: “Humans are the only species capable of manipulating the biosphere on a large scale. We are not just another species evolving in the face of external influences. In contrast, we are the only species that has conscious choice regarding our future and that of Earth’s biodiversity.” Speaking to this, how can our current epoch defined by destructive human influence be compared to these past worlds, and what lessons might be learned?

Our epoch is known as the Holocene, and makes up the last 11,700 years of geological time. Human environmental influence extends past the beginning of the Holocene, but recently it has been both accelerating and fundamentally changing in type. With deep ocean dredging and drilling, we are disturbing ecosystems that had until now never encountered us, plastic is pervading every part of the biosphere, we are altering the atmosphere globally, and our consumption of resources has boomed. When we look to the past, we find a few occasions when some similar traits can be observed. New chemicals in an environment – from oxygen in the single-celled earth of the Proterozoic to wood in the Carboniferous – have disturbed the balance of the world, but ultimately incorporated in fundamental processes. The Great Oxygenation Event is widely suggested to have caused a turnover in microbial communities as those oxygen-intolerant species retreated to environments this new toxic gas could not reach. The delay between the origin of wood and the development of lignin-digesting bacteria has been suggested as a reason for the preponderance of peat forming swamps in the Carboniferous, although this is disputed. Whatever the reason, the laying down of peat – and then coal – changed the atmosphere radically, which led to greater aridity worldwide, ultimately destroying the suitable environment for the very trees that had caused that change. But the biggest effect we are having is that of disturbance, and for that we have to look to mass extinction events for parallels. Earth has existed in all kinds of climatic states over its history, but mass extinctions have occurred during times of sudden transition. From the end-Ordovician, when glaciers rapidly advanced and retreated from the poles, to the end-Permian, when unfathomably large volcanic eruptions deoxygenated the oceans and threw greenhouse gases into the atmosphere, to the end-Cretaceous, when the aftermath of a meteorite impact darkened the skies for years, rapid change is typically bad. Although life eventually returns, it can take millions of years, and the species that thrive afterwards are rarely those that had thrived before.

Our effects are often extreme and rapid, and part of the problem is that they are done with a short-term mindset. Some human modifications – such as the pre-Columbian cultivation of the Amazon rainforest, the development of clam gardens, or well-managed meadowlands – have increased diversity locally, and are sustainable in the long term. We mustn’t fall into the trap of thinking that humans can only be destructive, or that we are separate from the ecosystems we live in. But, looking to the past, it is clear what the consequence of destructive behaviours is. This is the Earth we live in, and we are part of this world, but worlds can change in a moment.

This book is a timely reminder of the impermanence of life on Earth, evocatively revealing the fragility of our existence. As a researcher of the past, what do you see for our future?

People often assume that I might answer this question in terms of biology of life after humanity, or of the evolutionary direction humans are heading in. Although speculation can be fun, I don’t think that’s a useful way of thinking, because as Earth history shows us, the broad strokes of biology will remain the same. There will always be the same patterns of energy flow through ecosystems, and amazing adaptations to environments so complex that to form any predictions of the truly long term is futile. But we must think ahead to our immediate future. Nobody is suggesting that humankind will become extinct any time soon – we are too generalist, too adaptable to any environment to suffer that kind of loss. But that doesn’t mean that people, societies, cultures will not suffer under the environmental change that is already underway. And of course, portraying climate change as something that is future is itself untrue; we have been feeling the effects of climate change for decades already, especially those of us in low-lying island nations, those prone to storms, or dependent on seasonal ice. The effects will continue to accrue and to spread, but I remain optimistic that we will do what needs to be done – cease extraction of fossil fuels, move to a less all-consuming society, and support less wealthy countries in improving quality of life through renewable energy rather than repeat the errors we have repeatedly made. I am optimistic, and hopeful, but it is not something that will just happen. I see hard work, and that it will be entirely worth it.

Otherlands: A World in the Making
Hardback | £19.99