“This book is both academically interesting and truly fun to read. That is a difficult balance to reach, but Witton does an excellent job of it by using a lighthearted, informal writing style in combination with a well-referenced, serious scientific review. An invaluable reference.”–Michael Habib, University of Southern California

Mark P. Witton is a paleontologist in the School of Earth and Environmental Sciences at the University of Portsmouth. He has served as a technical consultant for Walking with Dinosaurs 3D and many other film and television productions. His illustrations of pterosaurs, dinosaurs, and other prehistoric creatures have appeared in numerous publications, including Science and newspapers around the world.

PTEROSAURS

Natural History, Evolution, Anatomy

By MARK P. WITTON

PRINCETON UNIVERSITY PRESS

Copyright © 2013 Princeton University Press
All rights reserved.
ISBN: 978-0-691-15061-1

Contents

Preface…………………………………………………………..ixAcknowledgments……………………………………………………xi1. Leathery-Winged Harpies………………………………………….12. Understanding the Flying Reptiles…………………………………43. Pterosaur Beginnings…………………………………………….124. The Pterosaur Skeleton…………………………………………..235. Soft Bits………………………………………………………396. Flying Reptiles…………………………………………………567. Down from the Skies……………………………………………..648. The Private Lives of Pterosaurs…………………………………..749. The Diversity of Pterosaurs………………………………………9010. Early Pterosaurs and Dimorphodontidae…………………………….9511. Anurognathidae…………………………………………………10412. “Campylognathoidids”……………………………………………11313. Rhamphorhynchidae………………………………………………12314. Wukongopteridae………………………………………………..13515. Istiodactylidae………………………………………………..14316. Ornithocheiridae……………………………………………….15217. Boreopteridae………………………………………………….16418. Pteranodontia………………………………………………….17019. Ctenochasmatoidea………………………………………………18320. Dsungaripteroidea………………………………………………20121. Lonchodectidae…………………………………………………21122. Tapejaridae……………………………………………………21623. Chaoyangopteridae………………………………………………22824. Thalassodromidae……………………………………………….23425. Azhdarchidae…………………………………………………..24426. The Rise and Fall of the Pterosaur Empire…………………………259References………………………………………………………..265Index…………………………………………………………….283

Excerpt

CHAPTER 1

Leathery-Winged Harpies

If TV, film, and overzealous internet users have taughtme anything, it’s that the prehistoric world was harshand brutal, and everyday existence was a life-or-deathstruggle. These terrible landscapes would be unrecognizableto our modern eyes, and only the biggest,nastiest animals survived. Consider, for example, thegiant birds that stalked the Earth as recently as twomillion years ago. Taller than basketball players, theykicked and stabbed small, defenseless mammals todeath. The ancestors of our pet cats and dogs wieldedsabre teeth and bone-crushing jaws that they usedto hunt giant elephants and rhinoceros, themselvesarmed with tusks and horns that would shame theirmightiest modern relatives. The world was even moreferocious before these birds and mammals existed.During the span of time known as the Mesozoic (245–65million years ago, or “Ma”), terrible reptiles ruledthe day and predator-prey arms races were more intensethan the Cold War. Gangs of carnivorous dinosaursattacked their enormous herbivorous relatives,contesting their switchblade claws and armor-piercingteeth against the spikes, clubs, shields, and armoredhides of their quarry. The Mesozoic oceans were justas deadly, teeming with giant, snaggle-toothed marinereptiles that render Moby Dick as intimidating as Flipper.Even the planet itself had a bad attitude in thisAge of Reptiles. Angry volcanoes perpetually smoked,continents ripped themselves to pieces, and giganticmeteorites collided with the Earth, thowing enoughdust and ash into the skies to block out the sun andcause cataclysmic extinction events.

The skies of this terrible age were no less formidable.They were dominated by a group of lanky grotesques,strange hybrids of birds and bats with a decidedly reptilianflavor. Their oversize heads were bristling withferocious teeth or else bore savage beaks, each usedto spear fish from primordial seas. Their outstretchedmembranous wings attained dimensions rivalingthe wingspans of small aircraft, but were supportedby lank, undermuscled limbs and tiny bodies. Theywere weak, flimsy, and pathetic animals, barely ableto power their own locomotion and reliant on cliffsand headwinds to achieve flight. They were virtuallyhelpless when grounded, barely able to push or dragthemselves about, and completely at the mercy of anycarnivorous reptile that fancied chewing on their hollow,twiglet-like bones. These creaky beasts were anarchaic first attempt by vertebrate animals to achieveflight before graceful birds and nimble bats inheritedthe skies later in Earth’s history. Given their obviousphysical ineptitude, it’s hardly surprising these creatures,the pterosaurs, collectively bought the farm atthe end of the Mesozoic, along with any dinosaur thatwas not lucky enough to have evolved into a bird.

But That’s All Hokum

Of course, the world and animals described aboveare nothing but caricatures of reality, the sort of landscapeyou may expect to find in Arthur Conan Doyle’sThe Lost World or similar-grade fiction. The popularview of primordial Earth as violent and totally unfamiliaris probably entirely untrue, a construct of poorscientific communication, overdramatic media representation,and romantic storytellers. In reality, ancientanimals were no less sophisticated or intelligent, normore freakish and savage, than those alive today. Paleontologicalresearch has probed deeply into the exoticand strange natures of many ancient animals to revealthat they merely represent “extreme” variants of anatomiesand behaviors we see in our modern, familiarspecies. Such research has not made animals like thelong-necked sauropods or giant theropod dinosaursany less spectacular, but they are certainly not as mysteriousand enigmatic as they once were.

Pterosaurs, which translates from Greek to”winged lizards,” have suffered more than most intheir depiction as ancient savages. All that remainsof these animals are their fossil bones, oddly proportionedskeletons that have proved difficult to comprehendand continue to cause frequent controversiesamong those who study them. The pterosaur’sability to fly, combined with bizarre anatomy, oftengigantic size, and an old-fashioned attitude thatextinct animals were inherently inferior to modernspecies, resulted in them being perceived as crude,biological hang gliders, which were rather useless ateverything but remaining airborne. Constant, oftenunwarranted, comparisons with birds and bats hascast pterosaurs as evolutionary also-rans, vertebratesthat took the bold first stab at powered flight butwere ultimately only the warm-up act for later, moresophisticated fliers.

Thankfully, these attitudes have slowly changed.Most modern pterosaurologists perceive pterosaursas successful, diverse animals with interesting andintricate life histories, and in this book we’ll discoverthe evidence for this change in attitude. We’llsee that, while pterosaurs were undeniably very welladapted for powered flight (fig. 1.1), they were alsoskilled walkers, runners, and swimmers. They livedin diverse habitats across the globe and fueled theiractive lifestyles with prey caught in distinct, dynamicways. They grew from precocial beginnings to adulthoodand invested heavily in social and sexual displaybefore becoming old and, in some cases, sick and arthritic.We’ll meet numerous pterosaur groups (fig.1.2) and over one hundred species spread across a dynastyspanning almost the entire Mesozoic, beginningin the Triassic period (245–205 Ma), thriving in theJurassic (205–145 Ma), before ending at the very endof the Cretaceous, 65 Ma.

Our overview of pterosaurs is split into three parts.We’ll start with an assessment of their general paleobiology,looking at their anatomy, locomotion, andother generalities of their lifestyles. Then, beginningwith chapter 9, we’ll meet, chapter by chapter, thediverse array of pterosaur groups currently recognizedby pterosaur researchers, or “pterosaurologists.”Finally, in the last chapter, we’ll ponder their evolutionarystory and try to ascertain why the skies ofmodern times are not full of membranous, reptilianwings in the way they once were.

CHAPTER 2

Understanding the Flying Reptiles

Pterosaurs have a track record of being a rather difficultgroup of animals to study. Since their discoverywell over two centuries ago, they have frequentlyconfounded attempts to comprehend their relationshipsto other animals (chapter 3), their terrestriallocomotion (chapter 7), or even simply parts of theiranatomy (chapters 4 and 5). The history of these specificaspects of pterosaur research will be covered insubsequent chapters but, before we get to these, wewill take a moment to familiarize ourselves with abroad outline of the first 230 years of pterosaur studies.In addition to the subsequent chapters offeredhere, readers particularly interested in the history ofpterosaur research may enjoy the excellent discourseson this topic by the godfather of modern pterosaurology,Peter Wellnhofer (1991a, 2008). As we’ll seebelow, Wellnhofer almost single-handedly revolutionizedpterosaur research and laid the foundations forour modern understanding of these animals. He alsoprovided a critical link between the three main agesof pterosaur paleontology, which can be roughly dividedinto the fruitful 1800s, a slump in the middle ofthe twentieth century, and our current golden age ofpterosaurology.

1700–1900: Discovery After Discovery,Revelation After Revelation

The first pterosaur fossil, an exquisitely preserved,complete skeleton of an animal that would later becalled Pterodactylus (figs. 2.1 and 2.2; also see chapter19), was found at some point between 1767 and1784 in the world famous Jurassic Solnhofen Limestoneof Germany, the same deposit that would lateryield the famous fossil bird Archaeopteryx (Wellnhofer1991a). The skeleton was brought to the attention ofthe Italian naturalist Cosimo Collini. Despite carefulstudy, he remained unsure about the nature of thefossil. He thought the specimen represented a petrifiedamphibious creature, and suggested that the longfourth digit on each hand may have represented thespar of a flipper. Collini published his illustrationand description of the fossil in 1784, the first documentationof a pterosaur in scientific literature. Hiswork was soon noticed by the most eminent naturalhistorian and comparative anatomist of the time,Baron Georges Cuvier. Cuvier’s tremendous knowledgeof animal form enabled him to see through thealien nature of the remains, and he realized fromCollini’s illustration that the elongate fourth fingerwas not a flipper at all, but the supporting strut of amembranous wing on an ancient, flighted, and reptiliancreature (Cuvier 1801; see Taquet and Padian 2004for details).

It is hard for us to imagine how significant Collini’sPterodactylus was to those originally studying it. Farfrom just revealing the existence of pterosaurs, thisanimal was also strong evidence for a concept thatwas once considered radical by even the most eminentnineteenth century researchers: extinction. Most fossilsknown at that point were the remains of marineanimals that, although never seen by humans, mayhave still existed in unexplored depths of the oceans.Collini’s pterosaur, by contrast, was a relatively large,conspicuous creature that would live in our own realmif it existed today. This distinctive creature, as well asseveral other newly discovered, large, terrestrial fossilvertebrates, had never been witnessed in the surveyedparts of the world, forcing scholars like Colliniand Cuvier to grapple with, and eventually accept,the concepts of life before human history and extinction(Taquet and Padian 2004). These ideas were onlysome of the heretical concepts proposed in what wenow term the Age of Enlightenment, a century-longperiod in which eighteenth-century researchers beganto place empirical observations and data before thereligious doctrine that had previously been used toexplain the natural world. Thus, our introduction topterosaurs coincided with a rich period of scientificdiscovery, making them an integral part of the foundationsof paleontology and geology.

Spurred on by a new understanding of the world,nineteenth-century investigators were prolific in theirdocumentation and analysis of pterosaur fossils, althoughit was the middle of the nineteenth centurybefore Cuvier’s reptilian identification of pterosaurswas fully accepted. Fossils of new pterosaurs werebeing found across southern Germany and in otherparts of Europe (e.g., Buckland 1829) and by the late1800s, they were uncovered in the newly opened andfossil-rich deposits of North America (Marsh 1871).Much of the pterosaur material available to these Victorianinvestigators was rather scrappy, and followingthe once fashionable idea that every slight differenceamong fossil specimens was of taxonomic significance,dozens of pterosaur species were named that are ofdubious validity to our modern eyes. Pterosaurologistsare still struggling with the fallout of this overzealousnaming, but by way of redeeming themselves,many Victorian paleontologists were also extremelyskilled at describing and illustrating their pterosaurspecimens (fig. 2.3). Thus, over one hundred yearson, their work remains relevant and valuable to modernresearchers, and is still cited heavily in modernliterature.

1900–1970: Midlife Crisis

The turn of the twentieth century started well forpterosaur scientists. The British paleontologist HarrySeeley published the world’s first popular pterosaurbook Dragons of the Air in 1901 (fig. 2.4), andthe first aeronautical studies of pterosaur flight wereperformed shortly after (Hankin and Watson 1914).The chimneys of the pterosaur research factory continuedto smoke until the 1930s, when pterosaur researchinexplicably almost ground to a halt for threedecades. Only a handful of contributions were madeto technical pterosaur literature during this time (fig.2.5), and many of these were simply brief descriptionsof scrappy new pterosaur fossils. As the seeds of ourmodern age were sown by men walking on the Moon,the advent of digital technology, and Jimi Hendrixplaying guitar with his teeth, our perception of pterosaursgathered dust and was no more advanced than itwas at the end of the Victorian era.

1970–Present: The New Golden Age

Interest in pterosaurs picked up again in the 1970s,largely thanks to the work of the aforementioned fatherof modern pterosaurology, Peter Wellnhofer. Dedicatinghis research almost entirely to pterosaurs, Wellnhofer’sfirst publications on these animals were landmarkworks on the taxonomy, growth, and functionalmorphology of the pterosaurs of the Solnhofen Limestone,the same deposit that yielded the first pterosaurremains almost two hundred years earlier (Wellnhofer1970, 1975). In 1978, he summarized pterosaur knowledgeknown at that time in the Handbuch der Paläoherpetologie,Teil 19: Pterosauria (translated from Germanto Handbook of Paleoherpetology, Volume 19: Pterosauria,or the Pterosaur Handbook for short) and documented,in the superb detail typical of his work, the anatomyof newly discovered, exquisitely preserved pterosaursfrom Brazil (Wellnhofer 1985, 1987a, 1991b). Roundingoff his achievements was the incredibly successfulEncyclopedia of Pterosaurs (Wellnhofer 1991a), thefirst popular pterosaur book since Seeley’s 1901 effort,which remains an incredibly useful reference tool foracademics and laymen alike. His substantial body ofwork, only touched on here, not only established amodern framework for subsequent pterosaur researchersto work with but, as importantly, made pterosaursan attractive topic to investigate again. By the early1980s, pterosaur research had surpassed the intensityof its pre-1930 heyday with new discussions of pterosaurtaxonomy, the description of numerous new speciesand a keen interest in pterosaur flight (e.g., Bramwelland Whitfield 1974; Stein 1975; also see fig. 2.6).Although dated now, these early flight studies pavedthe way for modern research into pterosaur flight biomechanicsand are still routinely discussed by modernpterosaur workers.

As if rewarding this renewed interest in flying reptiles,the 1980s and 1990s saw fossil sites in Brazil andChina termed “Lagerstätten” (fossil sites of exceptionallyhigh preservation quality) yielding the best pterosaurfossils anyone had ever seen (fig. 2.7). The BrazilianSantana Formation was the first to do so, providing fantasticallypreserved, three-dimensional remains of largepterosaurs (e.g., Unwin 1988a), while the neighboringCrato Formation provided crushed pterosaur materialwith extensive soft-tissue preservation (reviewedby Unwin and Martill 2007). New discoveries in theLiaoning Province of China revealed similarly crushedpterosaur fossils in the late 1990s, but unlike the CratoFormation, these remains were often complete (fig.2.8). These deposits have revolutionized our appreciationof pterosaur diversity by revealing several entirelynew pterosaur groups, and have allowed for a greaterunderstanding of pterosaur anatomy and systematicsthan ever before. In turn, this has provided a significantwindow into the nature of the more fragmentary pterosaurmaterial common to non-Lagerstätten deposits,so a greater understanding of the group’s evolutionaryhistory has been gained overall.

The monumental explosion in technology thatmarked the end of the twentieth century has alsochanged how we understand pterosaurs. Scanningelectron microscopes (SEMs) allow observation ofpterosaur remains at nanometer scales, and viewingspecimens under ultraviolet (UV) light revealssoft-tissue structures that are invisible to the nakedeye (fig. 2.9). Computed tomography (CT) scanningof pterosaur fossils has revealed brain casts and thecomplicated internal structure of pterosaur bonesthat were previously only accessible in broken fossilsor through destructive sectioning techniques (fig.2.10). Pterosaurology has also benefited, as has muchof paleontology, by the availability of powerful computingpower. A simple laptop can hold two centuriesof technical pterosaur literature, predict relationshipsbetween pterosaur species, calculate scaling regimesjoint mechanics, and provide a platform to communicateideas between research institutes, as well as describeand illustrate fossil specimens for publication.Pterosaurology has never progressed so rapidly orbeen so accessible, and is only set to grow as a paleontologicaldiscipline as more and more students aredrawn to it.

This third century of pterosaur research, then, isbound to be the most productive yet, where everyspecimen, new and old, offers greater insight intomore aspects of pterosaur paleobiology than ever before.Alas, all this productivity means we’ve got a lotof ground to cover and necessitates the brevity of thisoverview. We had best tuck away our nostalgia andmove on to our next stop: Just what are pterosaurs?
(Continues…)Excerpted from PTEROSAURS by MARK P. WITTON. Copyright © 2013 by Princeton University Press. Excerpted by permission of PRINCETON UNIVERSITY PRESS.
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