This is the second of a two-part dive into the world of pterosaurs, following on from my review of Mark Witton’s 2013 book Pterosaurs. Almost a decade later, the well-known independent palaeontologist and palaeoartist Gregory S. Paul has written and illustrated The Princeton Field Guide to Pterosaurs. Admittedly, a field guide to extinct creatures sounds contradictory. Really, this is an illustrated guide for the palaeo-enthusiast in which Paul’s signature skeletal reconstructions take centre stage.

The Princeton Field Guide to Pterosaurs, written by Gregory S. Paul, published by Princeton University Press in June 2022 (hardback, 184 pages)

This is Paul’s third Princeton Field Guide to prehistoric life. Paul wrote and illustrated The Princeton Field Guide to Dinosaurs in 2010, followed by a second edition in 2016 (which is when Donald Prothero wrote The Princeton Field Guide to Prehistoric Mammals) and a third edition in 2024. A fourth book was published in October 2023 with The Princeton Field Guide to Mesozoic Sea Reptiles which completed Paul’s informal trilogy covering all the major reptile groups of the Mesozoic. Finally, The Princeton Field Guide to Predatory Dinosaurs has been announced for November 2024. All these guides follow a unified style. Indeed, when comparing the dinosaur guide with this book, I noticed that it closely follows the same format and layout, down to very similar wording in some sections.

The Princeton Field Guide to Pterosaurs is divided into two halves: an introduction, and the group and species accounts. The introduction opens with the history of pterosaur research, describes what kind of reptile pterosaurs were and who they were related to, and gives some basics on dating fossils. The problem Witton flagged up in 2013 holds a decade on: clear transitional fossils showing how pterosaurs became airborne are still lacking. Paul then introduces the world in which pterosaurs evolved and I liked how he effectively zooms out to provide more context. What was the world like in the Triassic? What other organisms lived in it? How did all this interact throughout the approximately 162 million-year lifespan of the pterosaurs? And what creatures exploited their ecological niche after they went extinct?

Most of the introduction is dedicated to pterosaur biology, giving an overview of anatomy, locomotion and flight, pneumatic skeletons, integument and colouration, physiology, sensory biology, diseases and injuries, behaviour, and metabolism and growth. Much of the material here agrees with what Witton wrote in 2013, but Paul provides a more thorough introduction to locomotion and especially flight. Where Witton covered flight in eight pages, Paul lavishes 22 pages on the topic, going into quite some technical depth by making thorough comparisons to birds, bats, and aircraft, and drawing on aerodynamics and aeronautics. Given the way he references classic fighter planes, I got the impression he has at least an abiding interest in aeroplanes. Another noticeable difference is that Paul is bolder in his assertions and opinions as to what pterosaurs did or were capable of. For example, since reptiles and birds have full-colour vision extending into the UV range, “pterosaurs almost certainly did as well” (p. 70). I noticed the same in the species accounts, where data is presented in bullet-point statements, leaving little room to indicate how robust or speculative ideas are about e.g. lifestyles and foraging strategies of different species. A final section describes where fossils are typically found and how many species there might have been. Paul also engages in a bit of speculative zoology, imagining a spot of time travel to go on a pterosaur safari, and what might have happened had pterosaurs not gone extinct.

“Paul lavishes 22 pages on the topic [of flight], going into quite some technical depth by making thorough comparisons to birds, bats, and aircraft, and drawing on aerodynamics and aeronautics. “

The second half of the book discusses groups and species. Where Witton made taxonomy the leitmotif of his book, picking a phylogeny and dedicating a chapter to each major group, Paul refuses to put his nickel down. He recognizes the division between rhamphorhynchoids (a name he admits is obsolete but that he prefers over “nonpterodactyloid pterosaurs”) and pterodactyloids, divided into basal and derived forms. But since there is no consensus and phylogenetic studies are too conflicting for his liking, he shows no family tree. He does arrange species in a phylogenetic order, with derived groups nested inside basal clades, but he uses “a degree of personal choice and judgment in arranging the groups“, some of which reflect “my considered opinion, but most are arbitrary choices among a large array of competing research results” (p. 91). A second difference with Witton’s approach is that Paul writes the species entries as if this were a real field guide, with telegram-style entries describing size and weight estimates, known fossil remains, anatomy, geological age, location and geological formation of fossils, habitat, lifestyle, and other notes. This is the reference section of the book, collecting facts without a guiding narrative.

A stand-out feature of this book is the illustrations, specifically the skeletal reconstructions. Paul’s signature style of white bones on the black outline of a body is well-known and one he has been practising for decades. Rather than full skeletons, most show only the bones that have been found for a species, positioned in the right place. Where sufficient fossil material is available, full skeletons are shown. Some of these, Paul mentions, are composites. For a few species there is even enough material to show hatchlings, juveniles, or immature individuals. Paul criticizes the quadrupedal launch pose used by Witton and others for skeletal reconstructions as visually awkward and obscuring wing shape and proportions. He instead shows animals taking off with the wing at the top of an upstroke. I actually agree with Paul’s choice of pose: it looks more familiar, resembling a large bird taking off. For a select few species, there are muscle studies, which he admits are speculative but based on sound anatomical principles, as well as life reconstructions. Lastly, there are some palaeoart pieces showing animals in their natural environment. I admit I was not fond of all of these; some show a pencil-drawn animal placed on a photographic background, which is visually rather jarring. Notably absent are photos of fossils.

“A stand-out feature of this book is the illustrations, specifically the skeletal reconstructions. Paul’s signature style of white bones on the black outline of a body […] show only the bones that have been found for a species, positioned in the right place.”

So, what has happened in the world of pterosaur research since Witton’s 2013 book? Paul makes no particular point of highlighting significant advances, and without an expert background, the different approach of the two books makes it quite hard to determine this. Two studies that caught my attention were the evidence for pterosaurs eating cephalopods (quite logical) and a study on istiodactylid hyoid bones (the bone to which the tongue attaches). Obviously, Paul references new papers describing new species: China has continued to be a goldmine; Witton was involved in the 2017 description of the giant azhdarchid Hatzegopteryx thambema; and I found the 2014 description of Ikandraco avatar equally interesting. The last one is mentioned as a potential skim-feeder, a foraging strategy Witton has strongly rejected before. Maybe this time it is for real?

To wrap up, how do the two books compare? Pterosaurs is more narrative-driven and Witton is more circumspect in his claims; The Princeton Field Guide to Pterosaurs is more data-dense and Paul is bolder in his claims. If you are completely new to pterosaurs, I would actually recommend that you start with the former; I found its overview of the different groups more accessible. Then, if you want to read deeper into the details or need a reference work, the latter is a good follow-up; the two books complement each other nicely that way. If you already have Witton’s book, I think it is worthwhile getting Paul’s book. Next to being up to date, The Princeton Field Guide to Pterosaurs offers a different, sometimes more thorough take, and much more factual detail.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

The Princeton Field Guide to Pterosaurs

Other recommended books mentioned in this review:

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The downside of starting a review blog is that certain books will have missed the cut, having been published sometime before you started. And with the constant churn of exciting new titles, it is hard to make time for them. Sometimes a new book on a certain topic is just the prompt you need though. Thus, with Princeton University Press having recently published Gregory S. Paul’s The Princeton Field Guide to Pterosaurs, I decided to finally take Mark Witton’s 2013 book Pterosaurs off the shelf and read them back-to-back. This, then, is the first of a two-part dive into the world of these extinct flying reptiles.

Pterosaurs: Natural History, Evolution, Anatomy, written by Mark P. Witton, published by Princeton University Press in May 2013 (hardback, 291 pages)

Palaeontologist and palaeoartist Mark Witton can safely be called a pterosaur specialist, having written his PhD thesis on them in 2008, followed five years later by this, his first solo-outing writing a book. It has been the most substantive, go-to popular book on pterosaurs for years. The book is one-third general introduction and two-thirds taxonomic coverage, taking a look at all the major groups.

Witton opens with an overview of the long history of pterosaur research (which began in the late 1700s) and the mystery of their early evolution: we still lack the transitional fossils that reveal how pterosaurs took to the air. Most of the introduction focuses on the biology though. Palaeontologists only have fossils to work with, so Witton introduces the typical characters of the skeleton and the jargon used to describe them. There is also the occasional yet spectacular evidence of fossilized soft tissue: integument, head crests, wing membranes, and (very rarely) fossilized muscle and brain casts. Based on this fossil evidence, further introductory chapters explain what we have inferred from this about pterosaur flight, locomotion on land, and their life history, including birth, growth, diet, reproduction, injuries, disease, and death.

The remaining two-thirds of the book covers 16 major groups. Pterosaur taxonomy continues to be hotly debated and there are two schools of thought, one based on a dataset compiled by David Unwin, and the other on work done by Alexander Kellner. Witton considers other phylogenetic work to be derivations from these ground schemes. Though he admits the Kellner scheme has some advantages, he largely adheres to the Unwin scheme for this book, but carefully highlights controversies and differences of opinion throughout. He goes through the groups by geological age from oldest to youngest which roughly results in a tripartite division. He first discusses a group of older and smaller, generally long-tailed pterosaurs that once upon a time went by the now-defunct name of Rhamphorhynchoidea (an important member are the titular Rhamphorhynchinae, if only because of the huge amount of fossil material that has been found). These groups are all offshoots—technically speaking a paraphyletic grouping—before Witton arrives at the very speciose group Pterodactyloidea that flourished during the Jurassic and Cretaceous and is further divided into two groups. First, the Ornithocheiroidea, generally lighter fliers associated with marine habitats; the genus Pteranodon is a well-known member. Second, the Lophocratia (a name not embraced by all pterosaur workers), which are generally heavier-built and associated with terrestrial habitats; the genus Pterodactylus is a well-known member. Witton’s aim is not to be comprehensive and discuss every single species. For example, for Ornithocheiridae, one of the best-studied groups, he only discusses genera. For each group, he talks you through their taxonomy, research history, anatomy, locomotion (both flight and terrestrial) and ecology (topics such as foraging strategies, growth, and mating behaviour).

“Witton shows the importance of corroborating evidence. The depositional setting […] can support ideas about locomotion. […] Conversely, there is no evidence to corroborate the idea that pterosaurs were skim-feeders. “

Before commenting some more on the writing, let me mention the illustrations. There are numerous colour photos of fossils, showing not just spectacular specimens but also the sometimes heavily compressed, fragmented, and scrappy remains palaeontologists have to work with. There are amazing photos of soft-tissue preservation, some taken under ultraviolet light that reveals heretofore invisible details. There are redrawn illustrations from old publications. And Witton has made full-page artwork for each group with sometimes comical captions, as well as life and skeletal reconstructions in a standardised pose. Reading the text closely, my impression is that for some groups we have not found complete skeletons, meaning some of these reconstructions do contain a certain amount of educated guesswork. Paul’s book approaches them slightly differently. Taken together, Pterosaurs is a visual delight to flick through.

But, back to the text itself, there is much to like about Witton’s narrative style of presenting data, with four observations standing out. First, he acknowledges different opinions, especially where taxonomy is concerned. In some cases, various fragmented remains have all been assigned unique species names but might be synonymous, i.e. belong to a single species. More excitingly, some might represent a growth series from juvenile to adult individuals. Second, he does not just describe what we know but also why it matters and what it reveals. The pay-off to the often jargon-laden anatomical descriptions comes when discussing locomotion and palaeoecology. What did this particular morphology allow an animal to do? How does bone betray the presence of soft tissue in life? (Seasoned readers might be aware that Witton has, well, somewhat of a soft spot for soft-tissue reconstruction in palaeoart) Fibrous bone texture on skulls is a strong indication that the animal had a head crest (though there are exceptions). The smooth texture of the enormous Nyctosaurus head prong is thus used to argue against it sporting a sail-like crest.

“What I particularly appreciated, and what I have gotten to know Witton for in his later books, is his circumspection and care.”

Third, Witton shows the importance of corroborating evidence. The depositional setting, i.e. the original type of environment in which a body was laid down, can support ideas about locomotion. For instance, rhamphorhynchids are considered to have had a soaring flight style like gulls and are indeed commonly found in marine sediments. Conversely, there is no evidence to corroborate the idea that pterosaurs were skim-feeders. This unique feeding behaviour, today seen in birds of the genus Rynchops, requires a suite of anatomical adaptations beyond a long and narrow beak that is missing in pterosaurs. Fourth, Witton shows that being a good palaeontologist means being a good natural historian. Knowledge of the behaviour of today’s animals is useful when imagining the behaviour of extinct ones. Comparisons to birds are particularly apt as they have thoroughly explored the ecological niche available to airborne creatures. Ctenochasmatoids have jaws with many hundreds of teeth and comparing the genus Pterodaustro with its comb-like teeth rows and upturned bill to filter-feeding birds today is appropriate. Similarly, could the giant azhdarchids with their long necks and beaks have behaved like waders, catching prey in shallow waters? The tiny feet make this seem unlikely. Waders patrolling soft ground benefit from splayed feet, so Witton rather imagines azhdarchids as terrifyingly large terrestrial stalkers. Lastly, he makes a strong case that the often spectacular head crests were for sexual display. In some species, we have clear evidence of their absence in juveniles and females, while presumed males possess them. Witton is not convinced they function in thermoregulation. Sure, he admits, birds lose heat through their beaks, “but this is obviously not their primary function and is only a consequence of their construction” (p. 242). The same is very likely true of head crests.

Pterosaurs is an incredibly accessible and educational book that provides plenty of technical information and references to the primary literature without overwhelming the reader. Witton occasionally injects his sense of off-beat humour, which I much enjoyed. By the end of the book, I had a far better idea of the richness of pterosaurs in terms of species and lifestyles. What I particularly appreciated, and what I have gotten to know Witton for in his later books, is his circumspection and care. He is at pains throughout to highlight that our ideas are always provisional on available data; sometimes these are so limited that we can only speculate. He opens the taxonomical section with the humble admission that “the following pages are only a snapshot of pterosaur diversity as we know it in 2012–13“, and does an unintended bit of foreshadowing: “should anyone write another book of this type in another decade, the number [of species] will have undoubtedly increased even more, and perhaps the arrangements of the chapters themselves would be very different” (p. 94). Well now. Let me turn to The Princeton Field Guide to Pterosaurs next, which was indeed published a decade later, to see what has changed in the meantime, and wrap up with a comparison between these two books.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Pterosaurs

Other recommended books mentioned in this review:

The deep past harbours many events, epochs, and places that are still a mystery to me. Case in point: once upon a time, North America was cut in half by an enormous ocean. Something I was only dimly aware of. Luckily, Indiana University Press’s flagship palaeontology series Life of the Past has just the book to remedy that. I may be three years late to the party, but this 2017 book provides all the details one could ask for, and then some.

Oceans of Kansas: A Natural History of the Western Interior Sea, written by Michael J. Everhart, published by Indiana University Press in July 2017 (hardback, 427 pages)

The title of this book is possibly why I initially overlooked it. The Western Interior Sea bisected North America from the Gulf of Mexico to the Arctic, covering far more than the state of Kansas. But since the author Michael J. Everhart (the Adjunct Curator of Paleontology at the Sternberg Museum of Natural History in Hays, Kansas) has spent his professional career in Kansas, and the pickings here are particularly good, Oceans of Kansas it is. It was one of many ancient oceans: bodies of water that no longer exist due to plate tectonics, changes in sea-level, or both (see my review of Earth History and Palaeogeography). Where, for instance, the Tethys Ocean closed over time, land uplift and retreating water left the Western Interior Sea high and dry but very much in place. This is why you can find fossils of ancient fish, turtles, and marine reptiles in what are now the Great Plains of North America.

The first two chapters introduce the location and the history of the discovery of this inland sea. Although the book takes regular excursions, the focus is squarely on the Cretaceous rock record in Kansas, spanning about 30 million years, and within that specifically on the Smoky Hill Chalk. This was deposited when microscopic shelled creatures lived and died over some 5 million years, blanketing the bottom of the Western Interior Sea with marine sediment that turned into chalk. It is this particular layer that offers a unique window into life between 87 to 82 million years ago.

“[…] land uplift and retreating water left the Western Interior Sea high and dry but very much in place. This is why you can find fossils of ancient fish, turtles, and marine reptiles in what are now the Great Plains of North America.”

The bulk of the book systematically details all the relevant taxonomic groups. It was a world where the sea bottom was blanketed with inoceramid clams while overhead the large marine fauna took centre stage. There were sharks in many sizes, including terrifyingly large Ginsu sharks (genus Cretoxyrhina) that left scratches and bite marks on, and sometimes even teeth embedded in, the bones of numerous other animals. But also unusual shell-crushing sharks (genus Ptychodus) with knobbly, dome-shaped teeth. There were numerous fish, including the enormous 5.5 m Xiphactinus, fanged fish (genus Enchodus), and Saurodontid fish with a sword-shaped lower jaw. Turtles shared the waters with a riot of other large marine reptiles: the plesiosaurs, divided into the long-necked elasmosaurids and the short-necked pliosaurids, and the massive mosasaurs, the top predators of this realm. Especially that last group is well portrayed here, providing a welcome update to the now fairly dated 1997 book Ancient Marine Reptiles and the 2005 book Sea Dragons. There is enough fossil material here for Everhart to include a well-informed natural history section, while the colour plates by the late Dan Varner provide some welcome eye candy.

For other groups, the information is scanter. Ammonites and related cephalopods must have populated these waters, but fossilised remains are few as their aragonite shells readily dissolved. There are the occasional remains of pteranodons, although these flying reptiles probably did not fly hundreds of miles to the middle of the Western Interior Sea to forage here. Everhart conjectures these were the victims during long-distance migrations. There were toothed seabirds of the genera Hesperornis and Ichthyornis, two branches of the bird family tree that are now extinct. And there are rare dinosaur remains. How they got there? The clue is in the title of a wonderful 2012 paper: Float, explode or sink: postmortem fate of lung-breathing marine vertebrates – these are the remains of carcasses washed out to sea.

“terrifyingly large Ginsu sharks […] left scratches and bite marks on, and sometimes even teeth embedded in, the bones of numerous other animals”

This brief natural history sketch is gleaned from fossils, and they are the focus of this book. Everhart provides museum accession numbers and exacting details on what animal parts were found when and where, who dug them up, who described them, and how taxonomic redescriptions means fossil specimens have sometimes been known by three or four different names since their discovery.

Take for example the mosasaur species currently known as Tylosaurus kansaensis. The type specimen (FHSM VP-2295) was originally collected in 1968 and identified as “Clidastes or Tylosaurus” when it was exhibited at the Sternberg Museum of Natural History in Kansas. Over the ensuing decades it was renamed Platecarpus, then T. nepaeolicus, then downgraded to the generic Tylosaurus n. sp. (short for new species). When the author and his colleagues examined the specimen in 1990, they agreed it was something else after all and named it T. kansaensis in 2005. This paper was criticised, claiming that T. kansaensis could not be separated from T. nepaeolicus and was a juvenile form of it. Everhart disagrees and that is where this particular matter rests for now. It makes me wonder: is there a central database to keep track of all these name changes?

Thus, Oceans of Kansas is not a very difficult or overtly technical book, but it is highly detailed. These kinds of minutiae are probably of limited interest to the general reader, but they are the hard currency of aspiring and practising palaeontologists. I always like to clarify that this remark is not intended as a criticism but as an observation of the level a book is pitched at – good to know going in. That said, it is not a dry read and Everhart livens it up by opening each chapter with a fictionalised account of “a day in the life of…”, and tells of curious historical incidents, backstories to remarkable fossils, and his personal experiences collecting in the field.

“Oceans of Kansas is […] highly detailed. These kinds of minutiae are probably of limited interest to the general reader, but they are the hard currency of aspiring and practising palaeontologists. “

Two things, in particular, emerged while reading Oceans of Kansas. First is a revealing look into the history of palaeontology. Not surprisingly, the infamous rivalry between O.C. Marsh and E.D. Cope features here. But others are equally important to the story of the Western Interior Sea: Joseph Leidy, Benjamin F. Mudge, Samuel W. Williston, and the Sternberg family. One thing that bedevils research to this day is the lack of stratigraphical data for older specimens, something that was not considered particularly important at the time! It was not until 1982 that E.D. Hattin produced an accurate chronostratigraphy based on numerous thin layers of residual volcanic ash deposits found in the Smoky Hill Chalk. This has allowed more precise dating of fossils.

Second is what this book reveals about palaeontology as a discipline. I already mentioned the confusing tangle of taxonomic name changes. Then there is the large amount of undescribed material lingering in museum collections. Everhart repeatedly writes, rather casually, how specimens collected sometimes a century ago are only now studied and described (I called this the dirty secret of natural history museums in my review of The Lost Species). The book also made me appreciate again just how fragmentary and haphazard the material is with which palaeontologists work. Much of the seafloor of the Western Interior Sea was exposed to erosion millions of years ago already, and thus no longer exists. So much information has been lost to time that it is a miracle that Everhart and his many colleagues have been able to reveal this much through their diligent work.

“The book made me appreciate again just how fragmentary and haphazard the material is with which palaeontologists work. […] it is a miracle that Everhart and his many colleagues have been able to reveal this much.”

Two final observations. The first thing you will notice when picking up this book is its sheer weight: the large trim size and thick paper stock make this book a lot heavier than you would expect for 400 pages. But this has been put to good use as the book is liberally illustrated with about 220 photos and drawings. Some weight could have been saved at the end of the book as references are given separately for each chapter, duplicating many of them. The second thing to note is that the first edition of Oceans of Kansas was published in 2005. I have not read it, but in the current preface, Everhart explains with some satisfaction how this second edition allowed him to finish what he started. Next to the obvious updates and new findings in the intervening twelve years, the first edition left out material that he wanted to include, but could not due to deadlines and publication schedules. This is a valuable update.

Like other site-specific books in the Life of the Past series (e.g. Mesozoic Sea Dragons, Dinosaurs of Darkness, and Jurassic West) Oceans of Kansas synthesizes a huge amount of information and is the definitive reference work to this time and place. It is thanks to scientists such as Everhart who dedicate their career to the exacting study of localised fossil-rich sites that we can a get glimpse into deep history.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Oceans of Kansas (2nd edition) hardback or ebook

Other recommended books mentioned in this review:

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