The Dinosauria

The Dinosauria: Second Edition

DAVID B. WEISHAMPEL
PETER DODSON
HALSZKA OSMÓLSKA
Copyright Date: 2004
Edition: 2
Pages: 880
https://www.jstor.org/stable/10.1525/j.ctt1pn61w
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  • Book Info
    The Dinosauria
    Book Description:

    When theThe Dinosauriawas first published more than a decade ago, it was hailed as "the best scholarly reference work available on dinosaurs" and "an historically unparalleled compendium of information." This second, fully revised edition continues in the same vein as the first but encompasses the recent spectacular discoveries that have continued to revolutionize the field. A state-of-the-science view of current world research, the volume includes comprehensive coverage of dinosaur systematics, reproduction, and life history strategies, biogeography, taphonomy, paleoecology, thermoregulation, and extinction. Its internationally renowned authors-forty-four specialists on the various members of the Dinosauria-contribute definitive descriptions and illustrations of these magnificent Mesozoic beasts. The first section ofThe Dinosauriabegins with the origin of the great clade of these fascinating reptiles, followed by separate coverage of each major dinosaur taxon, including the Mesozoic radiation of birds. The second part of the volume navigates through broad areas of interest. Here we find comprehensive documentation of dinosaur distribution through time and space, discussion of the interface between geology and biology, and the paleoecological inferences that can be made through this link. This new edition will be the benchmark reference for everyone who needs authoritative information on dinosaurs.

    eISBN: 978-0-520-94143-4
    Subjects: Paleontology

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
  3. ABBREVIATIONS USED IN FIGURES
    (pp. ix-xvi)
  4. FOREWORD
    (pp. xvii-xviii)
    David B. Weishampel, Peter Dodson and Halszka Osmólska

    A new edition ofThe Dinosauriashould be more than just an update of the first edition, especially given the unprecedented developments in dinosaurian research over the past decade. To reflect this growth, we have fully reorganized the book to reflect the monumental increase in dinosaurian diversity that comes from new discoveries in the field (and museums) and the taxonomic revisions of this material but more especially the profound impact that phylogenetic analysis has made on Dinosauria as a whole. This latter research has substantially influenced how we interpret not only the contents and features of taxa but also their...

  5. INTRODUCTION
    (pp. 1-4)
    DAVID B. WEISHAMPEL, PETER DODSON and HALSZKA OSMÓLSKA

    We have now entered the third millennium of the Common Era. The third century of dinosaur research will commence soon, and the study of dinosaurs is in a state of unprecedented activity everywhere. In earlier times, specimens were collected in remote terrains around the globe and delivered to major academic centers in North America and Europe for study. Today, vigorous research programs across the globe are broadening not only our understanding of dinosaur diversity but also the range of the intellectual perspectives brought to dinosaur studies. In Europe, long-standing dinosaur research in England, Wales, Scotland, France, Germany, Portugal, Spain, Belgium,...

  6. SECTION I Dinosaur Systematics
    • ONE Origin and Relationships of Dinosauria
      (pp. 7-20)
      MICHAEL J. BENTON

      Dinosauria is a well-diagnosed clade, and since birds are included within it the group is clearly significant among terrestrial vertebrates. Dinosaurs belong within Archosauria, a broader clade that also includes crocodilians as well as pterosaurs and various basal groups of Triassic age. Over the past thirty years considerable effort has been devoted to disentangling the phylogeny of archosaurs: some relationships have been firmly established, while others have yet to be discovered. This chapter considers the origin of the dinosaurs in terms of phylogeny and the timing of events. The primary evidence comes from a cladistic analysis of the Triassic archosaurs,...

    • SAURISCHIA
      (pp. 21-24)
      THOMAS R. HOLTZ JR. and HALSZKA OSMÓLSKA

      Saurischia, the sister group of Ornithischia, was first recognized by Harry Govier Seeley in 1887 (Seeley 1887a). Most of the members of this clade are placed in three higher taxa—Theropoda, Prosauropoda, and Sauropoda. Gauthier (1986) provided the first numerical cladistic analysis of Saurischia, which has provided the baseline for all subsequent studies of these three clades.

      Saurischia is a stem-based clade defined as all dinosaurs more closely related toTyrannosaurusthan toTriceratops(fig. S.1; Langer [this vol.] usesAllosaurusandStegosaurusas clade exemplars). Its diagnostic features are provided by Langer (chapter 2). Padian et al. (1999) defined...

    • TWO Basal Saurischia
      (pp. 25-46)
      MAX C. LANGER

      The name Saurischia was coined by Seeley in lectures given in 1887 (Seeley 1887a, 1888a) to designate those dinosaurs possessing a propubic pelvis. This plesiomorphic feature distinguishes them from ornithischians, which have an opisthopubic pelvis. Despite its general acceptance as a taxonomic unit since the proposal of the name (Huene 1932; Romer 1956; Colbert 1964a; Steel 1970), the monophyly of Saurischia was heavily questioned in the 1960s and 1970s (Charig et al. 1965; Charig 1976b; Reig 1970; Romer 1972c; Thulborn 1975; Cruickshank 1979). Its status as a natural group was, however, fixed by Bakker and Galton (1974), Bonaparte (1975b), and,...

    • THREE Ceratosauria
      (pp. 47-70)
      RONALD S. TYKOSKI and TIMOTHY ROWE

      Ceratosauria represents the first widespread and diverse radiation of theropod dinosaurs (table 3.1). The remains of these predators are the most common theropod fossils recovered from Upper Triassic and Lower Jurassic deposits worldwide, and members of the clade evidently became dominant predators on the Gondwanan landmasses during Cretaceous time. Their fossils are known from Africa, India, Madagascar, North America, South America, and Europe. There is considerable debate over the phylogenetic relationships of the group (Gauthier 1986; Rowe 1989; Rowe and Gauthier 1990; Holtz 1994, 1998a; Rowe et al. 1997a; Rauhut 1998, 2000a; Tykoski 1998; Carrano and Sampson 1999; Forster 1999;...

    • FOUR Basal Tetanurae
      (pp. 71-110)
      THOMAS R. HOLTZ JR., RALPH E. MOLNAR and PHILIP J. CURRIE

      Tetanurae was coined by Gauthier (1986) as a new taxon name for modern birds (Aves in his taxonomy) and all taxa sharing a more recent common ancestor with birds than with Ceratosauria (see also Sereno 1998; Padian et al. 1999). As then described, this taxon comprised Carnosauria (in Gauthier’s study essentiallyAllosaurus,tyrannosaurids, and their allies) and a redefined Coelurosauria, containing modern birds and all taxa closer to modern birds than to Carnosauria. At that time Gauthier recognized that some medium to large theropods, such asMegalosaurusandEustreptospondylus,possessed some carnosaur-like attributes but lacked certain apomorphies shared byAllosaurus,...

    • FIVE Tyrannosauroidea
      (pp. 111-136)
      THOMAS R. HOLTZ JR.

      Tyrannosauroids are among the most distinctive and best known of Mesozoic theropods (table 5.1). They are characterized by large skulls with a specialized, heterodont dentition, a derived squamosal-quadratojugal flange, and a highly pneumatic basicranium; greatly reduced forelimbs (both in size and in digit count); and elongate hindlimbs bearing a pinched third metatarsal (arctometatarsus).

      In recent years new discoveries and the use of modern phylogenetic analytical techniques have revealed the presence of taxa outside Tyrannosauridaesensu strictobut closer to this clade than to all other theropod groups. These include the newly described Early CretaceousEotyrannus lengi(Hutt et al. 2001;...

    • SIX Ornithomimosauria
      (pp. 137-150)
      PETER J. MAKOVICKY, YOSHITSUGU KOBAYASHI and PHILIP J. CURRIE

      Ornithomimosauria is a group of medium to large, lightly built theropods that are mainly known from Cretaceous sediments of central Asia and North America (table 6.1). They are characterized by having short, delicate skulls, elongate forelimbs with a weak, nonraptorial manus, and long hindlimbs. Advanced ornithomimosaurs are edentulous, although more basal members of the clade possess derived dentition. There are currently 11 named species of ornithomimosaurs, placed in seven genera. The oldest,Pelecanimimus polyodon,is from the Barremian of Spain, whereas all remaining taxa are from younger strata in either central Asia or western North America.

      Marsh (1890b) described the...

    • SEVEN Therizinosauroidea
      (pp. 151-164)
      JAMES M. CLARK, TERESA MARYAŃSKA and RINCHEN BARSBOLD

      In the decade since the publication of the first edition of this book several important discoveries have greatly expanded our understanding of the group previously known as Segnosauria and resolved the controversy over their relationships (table 7.1). Rather than their being relegated to a chapter between sauropodomorphs and ornithischians and considered Saurischiasedis mutabilis(Barsbold and Maryanska 1990), new evidence has reaffirmed their identity as theropods, as proposed by Perle and Barsbold in their original descriptions of this group. These important new discoveries include individuals with simple, feather-like integumentary structures (Xu et al. 1999a), the first record outside of Asia,...

    • EIGHT Oviraptorosauria
      (pp. 165-183)
      HALSZKA OSMÓLSKA, PHILIP J. CURRIE and RINCHEN BARSBOLD

      Oviraptorosauria comprises a group of Cretaceous maniraptoran theropods (table 8.1) unquestionable remains of which are so far known only from the Northern Hemisphere (Barsbold et al. 1990). They were cursorial, had slender hindlimbs and grasping hands, and rarely exceeded 2 m in length. Although the known postcranial skeletons of oviraptorosaurs deviate only slightly from the structure of other theropods, their skulls and mandibles are unlike those of any other dinosaurs known. Oviraptorosaurs had massive toothless jaws, and tall, median bony crests, or casques, sometimes surmounted their shortened, deep, and highly pneumatized skulls. Their tails included fewer vertebrae than in other...

    • NINE Troodontidae
      (pp. 184-195)
      PETER J. MAKOVICKY and MARK A. NORELL

      Troodontidae is a clade of small, lightly built maniraptorans known from Cretaceous deposits of Asia and North America (table 9.1). These theropods have serrated teeth, raptorial hands, and an enlarged sickle-shaped claw on the foot, indicative of a predatory lifestyle. Troodontids possess one of the highest encephalization quotients among nonavian dinosaurs and had keen senses, as indicated by their enlarged orbits and well-developed middle ear. Proportionately long hindlimbs indicate an agile lifestyle.

      Troodon formosuswas one of the earliest dinosaurs described from North America (Leidy 1856) based on an isolated tooth crown, but the name Troodontidae Gilmore, 1924, was originally...

    • TEN Dromaeosauridae
      (pp. 196-209)
      MARK A. NORELL and PETER J. MAKOVICKY

      Dromaeosaurids were small- to medium-sized carnivores (fig. 10.1). Several phylogenetic studies have found them to be close relatives to Avialae; consequently, their anatomy is of direct relevance to an understanding of avialan origins. They were bipedal animals with long, three-fingered forelimbs that ended in sharp, trenchant claws. Their hindlimbs sported three toes with a second digit that was large and hyper-retractable. The tail was stiffened by long chevrons and prezygapophyses spanning several vertebrae. Direct fossil evidence shows that at least some of these animals were covered with featherlike integumentary structures (fig. 10.2; Xu et al. 1999, 2000, 2001; Ji et...

    • ELEVEN Basal Avialae
      (pp. 210-231)
      KEVIN PADIAN

      Birds evolved from small carnivorous dinosaurs some 150 million years ago. Most of the features associated with birds—feathers, sternum, furcula, hollow limb bones, and so on—first evolved in carnivorous dinosaurs for purposes unrelated to the origins of birds or to flight. The animals that became birds ultimately co-opted for flight some features that had first evolved in their dinosaurian ancestors. These features mostly evolved in the context of the behavior of fast-running, ground-living maniraptorans, a group that includes dromaeosaurids, oviraptorids, and troodontids, as well as birds. Flight, as far as it can be reconstructed, evolved in one lineage...

    • TWELVE Prosauropoda
      (pp. 232-258)
      PETER M. GALTON and PAUL UPCHURCH

      Prosauropod dinosaurs were medium- to large-sized (approximately 2.5 to 10 m), bipedal, facultatively bipedal or quadrupedal sauropodomorphs with long necks and tails (fig. 12.1A, C). They were obligate or facultative herbivores and are usually the most common terrestrial vertebrates in the beds in which they occur. The skull is small, less than half the length of the femur; the jaw articulation is situated slightly to well below the level of the maxillary tooth row; and the dentition consists of small, homodont or weakly heterodont, spatulate teeth with coarse, obliquely angled marginal serrations. Digit I of the manus bears an enormous...

    • THIRTEEN Sauropoda
      (pp. 259-322)
      PAUL UPCHURCH, PAUL M. BARRETT and PETER DODSON

      Sauropod dinosaurs were gigantic quadrupedal herbivores (fig. 13.1). The group includes the largest terrestrial animals ever to have existed; some estimates suggest that they reached lengths of 35 m and may have weighed as much as 100 tonnes. Sauropods appeared in the Late Triassic (Buffetaut et al. 2000b), were the predominant terrestrial herbivores for much of the Jurassic (Bakker 1978), and remained an important part of the dinosaur fauna until their extinction at the end of the Cretaceous. They achieved a global distribution by the Middle Jurassic, and their remains have now been recovered from all continents except Antarctica (Weishampel...

    • ORNITHISCHIA
      (pp. 323-324)
      DAVID B. WEISHAMPEL

      Ornithischia, the sister group of Saurischia and hence half the evolutionary legacy of the common ancestor of these two groups, was first recognized by Harry Govier Seeley in 1887 (Seeley 1887a). Members of this clade, presently known from more than 200 species, have traditionally been grouped into five higher taxa—Stegosauria, Ankylosauria, Ornithopoda, Pachycephalosauria, and Ceratopsia, with a few species intercalated among them. Efforts to understand the phylogenetic relationships of these taxa using cladistics began in 1984 with the coincident publications of Norman (1984a) and Sereno (1984). Sereno (1986) provided a refinement and expansion of his earlier work, and the...

    • FOURTEEN Basal Ornithischia
      (pp. 325-334)
      DAVID B. NORMAN, LAWRENCE M. WITMER and DAVID B. WEISHAMPEL

      Ornithischia is a long-established and well-corroborated clade of dinosaurs that share a considerable number of anatomical characters. In recent years it has become apparent that a number of taxa of stratigraphically early and anatomically conservative ornithischians can be recognized. These are referred to in this chapter as basal ornithischians and, in the absence of further data, occupy a position on the ornithischian cladogram on the stem prior to Genasauria.

      The phylogenetic positions ofLesothosaurus, Pisanosaurus, Technosaurus,and several other taxa, notablyFabrosaurus,that are based on nondiagnostic remains (table 14.1) have proved controversial. Recent cladistic analyses of their relationships to...

    • FIFTEEN Basal Thyreophora
      (pp. 335-342)
      DAVID B. NORMAN, LAWRENCE M. WITMER and DAVID B. WEISHAMPEL

      Dinosaurs that bear prominent and/or extensive dorsal armor on the body are known as thyreophorans. They are best represented by ankylosaurs and stegosaurs, but several more basal forms can also be included in this group. These includeScelidosaurusOwen, 1861a, from England,EmausaurusHaubold, 1990, from Germany, andScutellosaurusColbert, 1981, from the southwestern United States, all known from the Early Jurassic.Scelidosaurusalso has the singular distinction of being the first reasonably complete, well-preserved dinosaur ever to be discovered and described (Norman 2000).

      Thyreophora is the name applied to the stem clade representing all taxa more closely related to...

    • SIXTEEN Stegosauria
      (pp. 343-362)
      PETER M. GALTON and PAUL UPCHURCH

      The first remains of stegosaurs were described 160 years ago, and Stegosauria has been in existence since Marsh (1877d) erected it more than 125 years ago (table 16.1). For the first 50 years, Stegosauria comprised all the armored and quadrupedal taxa from the Jurassic and Cretaceous. However, on the basis of the form of the pelvic girdle and hindlimbs, Romer (1927) recognized Stegosauria as primarily a Jurassic clade of Ornithischia. Stegosaurs are medium-sized to large quadrupedal herbivores (length up to approximately 9 m) with proportionally small heads, short and massive forelimbs, long columnar hindlimbs with a long femur, short metacarpals...

    • SEVENTEEN Ankylosauria
      (pp. 363-392)
      MATTHEW K. VICKARYOUS, TERESA MARYAŃSKA and DAVID B. WEISHAMPEL

      Ankylosauria is a monophyletic clade of quadrupedal herbivorous dinosaurs characterized, at least in part, by the pervasive development of parasagittal rows of osteoderms across the dorsolateral surfaces of the body and an unusual skull architecture with small denticulate teeth and an external investment of cranial ornamentation. With the possible exception of Africa, ankylosaurs are known from every continent (including Antarctica, Gasparini et al. 1987), distributed from the Kimmeridgian to the end of the Maastrichtian.

      Historically, the name Ankylosauria was introduced by Osborn (1923a), although the group was not diagnosed until several years later (Romer 1927, see also 1956, 1968). Whereas...

    • EIGHTEEN Basal Ornithopoda
      (pp. 393-412)
      DAVID B. NORMAN, HANS-DIETER SUES, LAWRENCE M. WITMER and RODOLFO A. CORIA

      Ornithopoda (table 18.1) is the name first used by Marsh (1881b) to designate bipedal, unarmored, herbivorous dinosaurs, some of which (hadrosaurids) had complex dentitions. Ornithopods have a stratigraphic range spanning the Lower Jurassic–Upper Cretaceous. The systematic position of the clade has been clarified and subsequently refined within a phylogenetic framework (Sereno 1986, 1998; Weishampel 1990a; Weishampel and Heinrich 1992). Use of the terms Ornithopoda and Euornithopoda follows that established by Weishampel (1990a).

      The ornithopod clade includes the small heterodontosaurids from the Early Jurassic and euornithopods, which range widely in body size and are known from the Middle Jurassic to...

    • NINETEEN Basal Iguanodontia
      (pp. 413-437)
      DAVID B. NORMAN

      Iguanodon-like ornithopod dinosaurs have been known since the early years of the nineteenth century, following the discovery ofIguanodon(Mantell 1825; see table 19.1).Iguanodonwas in fact one of the founding members of Dinosauria (Owen 1842b). Additional taxa have been described since that time, notablyCamptosaurus(Marsh 1879c; Hulke 1880b),Zalmoxes robustus(Nopcsa 1902; Weishampel et al. 2003),Dryosaurus(Gilmore 1925b; Janensch 1955),Probactrosaurus(Rozhdestvensky 1966; Lü 1997),Tenontosaurus(Ostrom 1970a; Forster 1990),Ouranosaurus(Taquet 1975, 1976), andMuttaburrasaurus(Bartholomai and Molnar 1981). More recently there has been a considerable increase in the number of taxa referred to this...

    • TWENTY Hadrosauridae
      (pp. 438-463)
      JOHN R. HORNER, DAVID B. WEISHAMPEL and CATHERINE A. FORSTER

      More is known about hadrosaurids than about virtually any other group of dinosaurs. Remains are often abundant and range from fully articulated skeletons (sometimes complete with sclerotic rings, stapes, hyoids, and ossified tendons) to disarticulated and isolated material. In addition, remains of eggs, embryos, hatchlings (perinates), and juveniles, as well as footprints and trackways, skin impressions, and coprolites have provided investigators with glimpses of dinosaur biology that are not generally afforded for other groups of dinosaurs. Hadrosaurids, the so-called duck-billed dinosaurs, were large (7–12 m long, average adult body weight 3,000 kg) and had broad edentulous beaks, long, low...

    • TWENTY-ONE Pachycephalosauria
      (pp. 464-477)
      TERESA MARYAŃSKA, RALPH E. CHAPMAN and DAVID B. WEISHAMPEL

      Pachycephalosauria, often called dome-headed or thick-headed dinosaurs, is a group of bipedal ornithischians with thickened bones of the skull roof. Pachycephalosaurians retain a few primitive ornithischian features, including a short premaxilla, premaxillary dentition, pronounced heterodonty, small leaflike cheek teeth, a mandible with a low coronoid process and a moderately developed retroarticular process, and an ischium without an obturator process. The group is restricted to the Late Cretaceous, with the exception of two Early Cretaceous species,Yaverlandia bitholusandStenopelix valdensis.Pachycephalosauria, as treated in this chapter, includes 14 genera, all but one(Stegoceras)of which are monospecific. The number of...

    • TWENTY-TWO Basal Ceratopsia
      (pp. 478-493)
      YOU HAILU and PETER DODSON

      Ceratopsia consists of Psittacosauridae and Neoceratopsia, the latter formed by numerous basal taxa and Ceratopsidae. Consequently, this chapter on basal ceratopsians includes psittacosaurids and nonceratopsid neoceratopsians. Psittacosauridae is a monogeneric(Psittacosaurus)clade consisting of 10 species, while basal Neoceratopsia is formed by 11 genera, with 12 species of basal Neoceratopsia being recognized (table 22.1). Psittacosaurids are known from the Early Cretaceous of Asia, whereas basal neoceratopsians come from the latest Jurassic(Chaoyangsaurus youngi,Zhao et al. 1999; Swisher et al. 2002) to the latest Cretaceous in Asia and North America. Basal ceratopsians are small (1–3 m long), bipedal or...

    • TWENTY-THREE Ceratopsidae
      (pp. 494-514)
      PETER DODSON, CATHERINE A. FORSTER and SCOTT D. SAMPSON

      Ceratopsids, or horned dinosaurs, comprise a monophyletic assemblage of large-bodied (4–8 m long), quadrupedal, herbivorous ornithischians. Easily recognized by their varied and elaborate horn and frill morphologies, as well as their hypertrophied narial regions and complex dental batteries, ceratopsids possess some of the largest, most elaborated skulls found among vertebrates. Indeed, skulls of certain taxa (e.g.,TorosaurusandPentaceratops) reached lengths greater than 2 m, the largest known for any terrestrial vertebrate (Colbert and Bump 1947; Lehman 1998). Ceratopsidae consists of two well-defined clades: Centrosaurinae and Chasmosaurinae. Although some genera and species are represented by single, incomplete individuals (e.g.,...

  7. SECTION II Dinosaur Distribution and Biology
    • TWENTY-FOUR Dinosaur Distribution
      (pp. 517-606)
      DAVID B. WEISHAMPEL, PAUL M. BARRETT, RODOLFO A. CORIA, JEAN LE LOEUFF, XU XING, ZHAO XIJIN, ASHOK SAHNI, ELIZABETH M. P. GOMANI and CHRISTOPHER R. NOTO

      Research on dinosaurs, whether on systematics, biogeography, paleoecology, or functional morphology, ultimately depends on their discovery in the field. This update of known dinosaur occurrences reflects an incredible 55% increase in the number of entries over those provided by Weishampel (1992), indicating the astonishing growth in the underpinnings of our research base in just over a decade. Not only has the number of dinosaur localities increased, but the high-latitude faunas are better known and the “midperiod” gaps are beginning to be filled in. As will be seen in this chapter, there have been substantial increases in the number of specimens...

    • TWENTY-FIVE Dinosaur Taphonomy
      (pp. 607-613)
      ANTHONY R. FIORILLO and DAVID A. EBERTH

      Taphonomy was originally defined as the study of the physical transition of animal remains from the biosphere to the lithosphere (Efremov 1940). In its broader modern definition and applications (Behrensmeyer and Kidwell 1985; Behrensmeyer et al. 2000), taphonomy is the study of all biotic and abiotic factors that influence the preservation of organismal remains after death. Taphonomic factors remove or modify information about living organisms and assemblages (e.g., soft tissue decomposition, bone dispersal) and therefore create a biased picture of their biology and environmental and ecological associations. Thus, studies of taphonomic influences provide opportunities to identify biases and remove them...

    • TWENTY-SIX Dinosaur Paleoecology
      (pp. 614-626)
      DAVID E. FASTOVSKY and JOSHUA B. SMITH

      In fact, little is known about the paleoecology of dinosaurs. We have their bones, and behavioral inferences can be made on the basis of functional morphology. Separations into crude categories like herbivore and carnivore are generally feasible and reliable and, within Dinosauria at least, such behavioral categories generally (but not exclusively) follow phylogenetic lines. The bones of particular dinosaurs are commonly found in association with the bones of other vertebrates (including other dinosaurs), and careful taphonomic detective work can, on occasion, turn an assemblage into a fauna. As has been noted for many years by Lockley (e.g., 1997; see also...

    • TWENTY-SEVEN Mesozoic Biogeography of Dinosauria
      (pp. 627-642)
      THOMAS R. HOLTZ JR., RALPH E. CHAPMAN and MATTHEW C. LAMANNA

      Between the first appearance of Dinosauria sometime near the beginning of the Late Triassic and the Cretaceous–Tertiary extinction event, the geography of Earth went through as profound a transformation as did the life on its surface. The assembly of Pangea was completed sometime in the Triassic, uniting all major continental units into a single landmass. However, this union began to break apart by the Triassic–Jurassic boundary, with the split between Gondwanan (South America, Africa, India, Madagascar, Antarctica, and Australia) and Laurasia (North America, Greenland, Europe, and Asia) along what is now the mid-ocean ridge of the southern North...

    • TWENTY-EIGHT Physiology of Nonavian Dinosaurs
      (pp. 643-659)
      ANUSUYA CHINSAMY and WILLEM J. HILLENIUS

      Ever since dinosaurs were first recognized as a distinct group of reptiles, the question of what they were like as living animals has sparked considerable interest. In many respects, dinosaurs were arguably the most successful of all land vertebrates. With their spectacular morphological diversity and impressive size range, they dominated the terrestrial fauna from the Late Triassic to the Late Cretaceous. Their cosmopolitan reign far surpassed that of any other group of tetrapods, including mammals. Not surprisingly, the possible reason for this unparalleled success—their biology—has been the focus of much attention. Dinosaur paleobiology remains a vibrant, exciting, and,...

    • TWENTY-NINE Dinosaur Physiology
      (pp. 660-671)
      KEVIN PADIAN and JOHN R. HORNER

      When Richard Owen named Dinosauria (1842b), he did so specifically to set them apart from other reptiles. He had only a few forms to work with, and they were known only from fragmentary remains. However, even on the basis of what was then known aboutIguanodon, Hylaeosaurus,andMegalosaurus,Owen knew two things about these animals: that they belonged together, and that they were like no other reptiles ever discovered, living or extinct (Torrens 1992).

      Today, when we look at the paintings and statues of these early dinosaurs made by such artists as Waterhouse Hawkins under Owen’s direction (fig. 29.1),...

    • THIRTY Dinosaur Extinction
      (pp. 672-684)
      J. DAVID ARCHIBALD and DAVID E. FASTOVSKY

      The disappearance of nonavian dinosaurs is probably the most notorious extinction event of all time, yet it is only a small part of a greater class of extinctions known as “mass extinctions.” Mass extinctions are global events characterized by unusually high rates of extinction. The magnitude of these rates is usually unspecified but it is generally significantly higher than the rate of so-called “background extinctions”; that is, extinctions that occur constantly through geologic time (Raup and Sepkoski 1982). Mass extinctions are also characterized by geologically short timescales and by a significant diminution in the number of surviving taxa, as well...

  8. LITERATURE CITED
    (pp. 685-774)
  9. CONTRIBUTORS
    (pp. 775-776)
  10. GENERA AND SPECIES INDEX
    (pp. 777-812)
  11. STRATIGRAPHIC AND GEOGRAPHIC INDEX
    (pp. 813-834)
  12. SUBJECT INDEX
    (pp. 835-861)
  13. Back Matter
    (pp. 862-862)