BOOK REVIEWS
King of the Crocodylians: The Paleobiology of Deinosuchus, David R. Schwimmer, 2002, Indiana University Press, Bloomington, 240 p. (Hardcover, $45.00) ISBN: 0-253-34087-X In a media world driven by dinosaurs, crocodyliforms have finally made the big time. The giants and oddities of the group have appeared in feature articles in National Geographic (e.g., Flynn and Krause, 2000; Sereno, 2001) and on television programs. This attention comes with a cost, as the same media biases plaguing dinosaurs arise, especially the push to find the biggest. But every clade has cool stories to tell, and a truly fascinating group is finally reaching a broad audience. David Schwimmer’s King of the Crocodylians is the most complete effort to date to tell the story of an animal crocodile aficionados have long admired—the enormous Campanian alligatoroid Deinosuchus. Deinosuchus found its way into the public imagination, however modestly, before any other big extinct crocodyliform; and, as Schwimmer describes, the famous restoration displayed by the American Museum of Natural History left an indelible mark in the minds of many. In many ways, King of the Crocodylians reads like two separate works combined into one. Parts of the book discuss the paleoenvironments and stratigraphy of the Cretaceous of eastern North America, and it is here that Schwimmer is at his best. Other parts are an account of the paleobiology of Deinosuchus, and it is here that the book is weakest. Nonetheless, Schwimmer has made a real contribution with the material he has collected and some of the conclusions drawn in this book. The first chapter sets the stage, beginning with a you-are-there description of a Late Cretaceous salt marsh somewhere in Alabama. Schwimmer describes the vegetation, the marine life, and the animals that lived on the land-sea interface. In a nod to the correct Scala
79 Naturae, the peace is broken by Deinosuchus killing and dismembering a tyrannosaur. The world he paints for us is both detailed and compelling. Schwimmer describes the early history of research on Deinosuchus in Chapter 2. We see the evolution of our understanding of Deinosuchus, from the original material from Montana, Texas, and North Carolina to new discoveries from Texas and the southeastern United States. The famous restoration at the AMNH was based on a very incomplete specimen. The assumptions that drove the reconstruction in the 1940‘s were valid then, but have been overturned by our improved sample. The real Deinosuchus skull looked very different from that original plaster restoration. Chapter 2 argues that the type species of Deinosuchus is Deinosuchus rugosus, based on a set of worn teeth from North Carolina reworked into Miocene deposits. This argument is further developed in chapter 6. I am not convinced that teeth are as diagnostic for Deinosuchus as this book suggests, but the relevant literature is cited, so readers can make up their own minds. Chapter 3 discusses the size of Deinosuchus, starting with a review of previous approaches to the problem, with estimates ranging from 15 meters in the older literature to 9 meters based on more recent work. Using an approach based on jaw length as a proxy for head length (Erickson and Brochu, 1999), the book derives a total length estimate of 8 meters for Deinosuchus from the Southeast. Comparisons with Deinosuchus from the western United States are complicated by the rarity of complete skulls or jaws; thus, the book assumes dorsal vertebral centrum length scales isometrically with jaw length and then compares the vertebrae of these southeastern specimens with larger vertebrae from Texas and Montana. This approach derives a total length estimate of 12 meters for the western form. These vertebrae are not associated with the mandible used by Erickson and Brochu (1999), so this is not necessarily a discrepancy. Moreover, the length estimate of around 9 meters derived by Erickson and Brochu was not, as stated in the book, a maximum size estimate—it was simply an estimate for a specimen. The size of Deinosuchus is placed in the context of other giant animals, including other giant crocodyliforms (though I was disappointed that Schwimmer did not mention the huge longirostrine crocodylian Rhamphosuchus, as the type material suggests an animal at least as long as Sarcosuchus). The chapters on Late Cretaceous paleogeography, paleoecology, and geochronology (chapters 4 and 5) are insightful and have a proper balance of detail and general language. The biostratigraphy section does a very good job of explaining the challenge of correlating farflung nonmarine deposits and includes a lucid discussion of absolute dating in a sedimentary context. The rationale behind an estuarine setting for many of the important Deinosuchus localities synthesizes disparate sources of information, and a nonspecialist reader will learn something about paleoecology. Schwimmer’s expertise in the geology of the southern Atlantic Coastal Plain clearly comes through in this book, and these sections make a good companion to Weishampel and Young’s (1996) Dinosaurs of the East Coast and Gallagher’s (1997) When Dinosaurs Roamed New Jersey. In spite of the strengths of the above chapters, chapters 6 and 7 (on the number of species of Deinosuchus and on Deinosuchus’ genealogy, respectively) are undermined by factual errors and misinterpretations of the primary literature. Sadly, the severity of this situation detracts from the quality of this book. A reader without access to the primary literature—and that is the kind of reader to whom this book presumably is aimed—will be unable to sort the accurate nucleus from the inaccurate flesh. Chapter 6 tentatively concludes that only a single species of Deinosuchus is known from North America. This could be right, but the evidence presented is not convincing. Much of the chapter discusses differences between Deinosuchus samples from east and west of the Western Interior Seaway. These samples also are separated stratigraphically, with the eastern samples occurring lower in the Campanian. Differences are dismissed as the result of size. This is plausible, but how size can be ruled out as a diagnostic feature is not really explained; and a false dichotomy is implied between parallelism (eastern and western samples represent independent derivations of gigantism) and conspecificity. The possibility of a vicariance event leading to sister species on either side of the seaway is not entertained. Moreover, many of the similarities between samples do not
80 support his conclusion. For example, the occlusal pattern in Deinosuchus on both sides of the Seaway combines an overbite between maxillary and dentary teeth (alligator-like) with exposure of the third and fourth dentary teeth in a notch between the maxilla and premaxilla (crocodile-like), which is described in the book as unique. In fact, this is the plesiomorphic condition for Crocodylia, and is known from several fossil taxa, including basal members of Borealosuchus, Pristichampsus, the basal-most crocodyloids (e.g., Prodiplocynodon), most outgroups to Eusuchia (such as Bernissartia), and Leidyosuchus (as shown dramatically in the Leidyosuchus skull on p. 155). Derived alligatoroids lost the notch, and several lineages (gavialoids, derived crocodyloids, derived Diplocynodon, derived Borealosuchus) independently lost the overbite (Willis, 1993; Brochu, 1999). Eastern populations are said to have given rise to western populations. This comes from a literal reading of the fossil record—eastern samples are older than western, so the western must be derived from the eastern. Assuming this (and assuming they represent coherent populations), a dispersal pattern is implied. The most obvious solution, a crossing of the Western Interior Seaway, is dismissed. I agree that Deinosuchus probably was not a regularly sea-going crocodylian, but the book’s arguments to discount periodic crossings of the Western Interior Seaway are flawed. We are told (p. 120) that extant crocodylians cannot drink salt water, and that those with salt-excreting glands on the tongue use these to maintain osmotic balance in drought conditions. This is not the complete story. Crocodylians cannot drink seawater, but they can nonetheless thrive in it given time to adjust (see Leslie and Taplin, 2001, and references therein). In at least some crocodylids, fresh water can be obtained from food (crocodylians can and will feed in seawater), not from drinking. Lingual salt glands may not play a significant role in draught-condition survival, and crocodylians can survive for long periods of time without drinking (Christian et al., 1996). The argument that a single individual crossing a marine barrier would not found a population is well taken, but as presented in this book, it sets up a false dichotomy—either one croc crossed the Seaway, or several did simultaneously. That crocs might cross a marine barrier independently, but close enough in time to encounter each other on the far side, was not considered. Crocodylians probably crossed marine barriers and founded populations several times since Late Cretaceous (e.g., Buffetaut, 1982; Molnar, 1982; Salisbury and Willis, 1996; Langston and Gasparini, 1997; Worthy et al., 1999; Brochu, 2000a). Crossings of the Western Interior Seaway cannot be ruled out. The book’s difficulty in accepting the dispersal of nonmarine, nonvolant animals across island chains (p. 133) is contradicted by the Galapagos Islands—or, for that matter, by the dispersal of extant Crocodylus throughout the Antilles or Indopacific region (a point acknowledged on p. 120). Many of the remaining problems in these two chapters reflect an attempt to combine the results of a phylogenetic analysis (and a nomenclature established to reflect it) with pre-phylogenetic taxonomic concepts and stratigraphic approaches to phylogeny. I was reminded of Biblical prohibitions against clothes made from combined wool and linen. Schwimmer is to be congratulated for using contemporary phylogenetic nomenclatural terms for fossil crocodylians, but the application here reveals a character-based concept of taxa that is completely incompatible with the way the names are applied in the phylogenetic system. This is revealed, for example, in the claim on p. 139 that a particular characteristic ‘‘is a necessary but not sufficient means to diagnose’’ a clade, which misses the point—a particular character can never be necessary or sufficient to diagnose a taxon if its name is defined in reference to phylogeny. As a result, these chapters are confusing and internally inconsistent. The phylogenetic definition of Crocodylia as the last common ancestor of gavialoids, alligatorids, and crocodylids and all of its descendents is discussed in the prologue and on p. 137. Crocodylia is a subset of Eusuchia, as acknowledged in Table 7.1 and on p. 157. But this meaning is inconsistent with its use, for example, on p. 29–30, where Crocodylia appears to take on a much broader meaning. If Crocodylia is a subset of Eusuchia (as current phylogenetic results indicate), then all crocodylians are eusuchians, but not all eusuchians are crocodylians. ‘‘Eusuchian crocodylian’’ is like ‘‘avian duck.’’ If procoelous vertebrae characterize eusuchians, then all crocodylians have them (unless they are secondarily lost, which is not what the book implies
BOOK REVIEWS on p. 30 by ‘‘less derived crocodylians’’ having ‘‘other morphologies’’). The definition of Crocodylia reported on p. 158 (lack of scapular blade flare) is a diagnosis. And Crocodylia is used as a morphological grade on p. 149, where mesoeucrocodylians are ranked on their degree of ‘‘crocodylian-ness’’. This kind of confusion also leads to some eye openers in the text. Although ‘‘bird’’ is not a formal taxon, the statement that tyrannosaurs are ‘‘really another form of bird’’ (p. 3) is like saying a moose is really another form of fruit bat. Another striking example comes from the book’s use of the names Leidyosuchus and Borealosuchus. The last paragraph on p. 162 presents Leidyosuchus as a geographically and stratigraphically widespread alligatoroid, but then states that many former Leidyosuchus are now outside Alligatoroidea in a clade named Borealosuchus. Elsewhere in the book, the number of species remaining in Leidyosuchus is specified as one. (In fact, Leidyosuchus is known with certainty only from the Dinosaur Park Formation of Alberta.) How can Leidyosuchus be geographically and stratigraphically widespread if it is restricted to a single species from one formation? Leidyosuchus is similar to Borealosuchus at a gross level, but the morphological details reveal a more distant relationship (Brochu, 1997; Wu et al., 2001a,b). Whether a specimen belongs to one or the other is not a point of mere semantics, as the names refer to very different biological entities. King of the Crocodylians approaches Leidyosuchus as a morphological category stripped of phylogenetic meaning, sometimes applying pre-phylogenetic diagnoses that relied as much on plesiomorphy as on apomorphy. The result is a flawed discussion of the historical biogeography of North American crocodylians. At issue is the identity of a set of remains, figured on p. 123, from the Campanian of Alabama. Since both Leidyosuchus and Borealosuchus are known from west of the Seaway during the Late Cretaceous, the presence of either in eastern North America could suggest some sort of faunal interaction between the two regions. Schwimmer states that ‘‘the question to address is whether a species of Leidyosuchus, or Borealosuchus, crossed the Seaway,’’ dismissing the distinction by stating on p. 121 ‘‘we will not delve into details of the proper systematics relating to the clade.’’ This seems to indicate that the difference between Leidyosuchus and Borealosuchus is a matter of morphological opinion and not a phylogenetic conclusion. But Leidyosuchus and Borealosuchus do not form an exclusive clade, and the distinction is not irrelevant (Brochu, 2000b). We cannot just shrug our shoulders and say ‘‘Leidyosuchus, Borealosuchus. . . whatever.’’ A close faunal relationship between east and west during the Campanian might be supported if the Alabaman specimen were closely related to L. canadensis or the Maastrichtian species of Borealosuchus (B. sternbergii), but a close relationship to B. sternbergii does not follow from a Campanian age of these remains. What about a closer relationship to post-Cretaceous Borealosuchus from the Cordilleran region? That might suggest minimal interaction during the Late Cretaceous, followed by increased interaction after withdrawal of the Seaway and dispersal of eastern Borealosuchus westward. Without an understanding of how this specimen relates to other crocodylians, we cannot rule out any biogeographic scenario. Identification of this material as Leidyosuchus is not convincing. Characters cited as diagnostic of Leidyosuchus—short mandibular symphysis, paired dentary caniniforms—would also apply to most species of Borealosuchus (including those from the Cenozoic), Diplocynodon, and to several crocodylian outgroups. And the stratigraphic argument is not convincing; on phylogenetic grounds, Borealosuchus also should appear in the Campanian, even if its first appearance (other than the Alabaman specimen) is Maastrichtian, and clade rank need not match the age rank. A thorough consideration of the morphological details is needed to resolve this issue. (I have seen this material—full discussion should await detailed description, but it is neither Leidyosuchus nor Diplocynodon, and is not closely related to B. sternbergii.) The osteoderms Schwimmer figures on p. 124 with ‘‘diagnostic Leidyosuchus features’’ have strongly concave anterior margins, which is unlike the dorsal osteoderms of Leidyosuchus canadensis. The features listed as diagnostic of Leidyosuchus scutes—rectangular, no keel, thin, zone of overlap—are common to all dorsal osteoderms from basal crocodylian lineages. The scutes shown here are very similar to those of Borealosuchus and the basal gavialoid Thor-
BOOK REVIEWS acosaurus, both known from the Atlantic Coastal Plain Cretaceous. The surficial pits are a bit small for Thoracosaurus, but most Thoracosaurus scutes I have seen are of Maastrichtian age. The review of crocodylomorph phylogeny in chapter 7 is verbose and convoluted. The equivalent of a full page is taken to simply state that archosaurs include two lineages, one leading to living crocs and including a bunch of cool extinct relatives, the other leading to birds and including a bunch of cool extinct relatives. Some of the cool extinct croc relatives are discussed, and the characters bringing them progressively closer to living crocodylians are discussed reasonably well, but why discuss aetosaurs, then poposaurids (which are closer to crocodylomorphs), then phytosaurs (which are very far down the tree), and then crocodylomorphs? Add to this the inconsistent use of taxon names and the confusion of definition and diagnosis, and I fail to see how an uninitiated reader can come away with a better understanding of the group. Given the volume of information that Schwimmer tries to summarize (and its complexity), this chapter could have been simplified greatly by including some sort of evolutionary diagram (i.e., cladogram, phylogram, Romerian bubblegram, or any other branching pattern that shows hypothesized relationships). The taxonomic table in the chapter (Table 7.1) is nice, but some taxa named in the text are not in the table. The discussion of Deinosuchus’ place in Alligatoroidea is generally good, though I would quibble with some of the character polarity interpretations. The last chapter of the book speculates on the diet of Deinosuchus. Given that modern crocodylians will eat any organic matter they can process and swallow, the inclusion of nonavian dinosaurs on a Deinosuchus menu is reasonable. The evidence marshalled in this book for bite marks on turtle carapaces and dinosaur bones is interesting, though it was not thoroughly convincing. The depressions shown on these bones could be Deinosuchus bites, but they also could be postmortem damage not related to a bite. Still, Deinosuchus (and other large crocodyliforms) probably dined on ornithopods from time to time. The glossary at the back of the book is generally good, but some of the definitions could be simplified. The rostrum is described on p. 197 as ‘‘an elongation of the skull forward to the orbits, containing the nasals, maxilla, and premaxilla,’’ but it also could be described as the snout. (Moreover, the plural form of rostrum is rostra, not rostrums.) The definition of kinesis (‘‘bone connections capable of movement’’, p. 196) does not describe kinesis in the broadest physical sense. And the definition of monophyletic is accurate, but is inconsistent with the phrase ‘‘monophyletic ancestor’’ encountered elsewhere in the book. There are a few minor detail errors scattered throughout the book. The Hungarian paleontologist Franz Nopcsa, for example, is described as German (p. 21), and the Cretaceous eusuchian Hylaeochampsa is placed in the Jurassic (p. 157). The South Atlantic is said to have opened before the North Atlantic (p. 12), but it was the other way around. The book’s claim that only two croc species occur in North America (p. 160) is true only if Mexico is disregarded. These have little to do with the ultimate conclusions of the book, but they should be fixed in a revised edition. Misspellings are few, but many of them are taxon names. The group including Diplocynodon in phylogenetic nomenclature is Diplocynodontinae, not Diplocynodontidae; the small crocodyliform shown on p. 151 is Araripesuchus patagonicus, not A. patagonensis; the big caiman shown on p. 58 is Purussaurus brasiliensis, not P. brasilicus; the two putative teleosaurids at the bottom of p. 153 are Machimosaurus (not Machismosaurus) and Rhytisodon (not Rhytiosodon); and the alligatoroid from Montana on p. 162 is Brachychampsa montana, not B. montanensis. The skull of Albertochampsa shown on p. 163 is the holotype of Stangerochampsa mccabei, and the Goniopholis skull shown on p. 155 is Leidyosuchus canadensis. The book uses the term ‘‘deinosuchid,’’ implying a taxon named Deinosuchidae that does not, to my knowledge, exist. Most of the problems with figure quality are not the author’s fault. Most Deinosuchus specimens, especially those from the Atlantic Coastal Plain, are black in color and water-worn. They will look like lumps of dark mud no matter how carefully they are photographed, though a set of plates on glossy paper would be an improvement. The artwork by D. Miller and R. Hirzel is quite good. But some pictures in this book are very dark and blurry (e.g., the photos of Giganotosaurus
81 on p. 54 or of Araripesuchus on p. 151), and, in some cases, labels would have been very helpful. Readers unfamiliar with crocodylian morphology may have trouble identifying the choana of the Alligator skull in Fig. 7.5 or interpret the partial ilium in Fig. 7.13. These should be addressed in future editions. A final issue is timeliness. The book often refers to new Deinosuchus material undergoing study. Schwimmer even states that this material could render large parts of the book obsolete. If this material is worth mentioning now, why not wait until it is prepared and published before completing a lengthy review on Deinosuchus? Ultimately, I came away with the strong impression that the book could have been reviewed more carefully. This is a shame, because the material it describes is important, and Schwimmer’s interdisciplinary approach is a model for all paleontologists. Some of the errors were fairly simple and could have been fixed easily without really changing the major conclusions. In summary, King of the Crocodylians is a commendable effort to summarize what we know about a truly magnificent animal. I look forward to the revised edition, which will belong on the shelf of anyone interested in fossil reptiles and paleoecology.
REFERENCES BROCHU, C.A., 1997, A review of ‘‘Leidyosuchus’’ (Crocodyliformes, Eusuchia) from the Cretaceous through Eocene of North America: Journal of Vertebrate Paleontology, v. 17, p. 679–697. BROCHU, C.A., 1999, Phylogeny, systematics, and historical biogeography of Alligatoroidea: Society of Vertebrate Paleontology Memoir v. 6, p. 9–100. BROCHU, C.A., 2000a, Phylogenetic relationships and divergence timing of Crocodylus based on morphology and the fossil record: Copeia, v. 3, p. 657–673. BROCHU, C.A., 2000b, Borealosuchus (Crocodylia) from the Paleocene of Big Bend National Park, Texas: Journal of Paleontology, v. 74, p. 181–187. BUFFETAUT, E., 1982, Systematique, origine et e´volution des Gavialidae Sud-Ame´ricains: Geobios: Memoire Special, v. 6, p. 127–140. CHRISTIAN, K., GREEN, B., and KENNETT, R., 1996, Some physiological consequences of estivation by freshwater crocodiles, Crocodylus johnstoni: Journal of Herpetology, v. 30, p. 1–9. ERICKSON, G.M., and BROCHU, C.A., 1999, How the ‘‘terror crocodile’’ grew so big: Nature, v. 398, p. 205–206. FLYNN, J.J., and KRAUSE, D.W., 2000, Monsters of Madagascar: National Geographic Magazine, v. 198, p. 44–57. GALLAGHER, W., 1997, When Dinosaurs Roamed New Jersey: Rutgers University Press, New Brunswick, 176 p. LANGSTON, W., and GASPARINI, Z., 1997, Crocodilians, Gryposuchus, and the South American gavials: in Kay, R.F., Madden, R.H., Cifelli, R.L., and Flynn, J.J., eds., Vertebrate Paleontology in the Neotropics: The Miocene Fauna of La Venta, Colombia: Smithsonian Institution Press, Washington, D. C., p. 113–154. LESLIE, A.J., and TAPLIN, L.E., 2001, Recent developments in osmoregulation of crocodilians: in Grigg, G., Seebacher, F., and Franklin, C.E., eds., Crocodilian Biology and Evolution: Surrey, Beatty and Sons, Chipping Norton, NSW, p. 265–279. MOLNAR, R.E., 1982, A longirostrine crocodilian from Murua (Woodlark), Solomon Sea: Memoirs of the Queensland Museum, v. 20, p. 675–685. SALISBURY, S.W., and WILLIS, P.M.A., 1996, A new crocodylian from the Early Eocene of southeastern Queensland and a preliminary investigation of the phylogenetic relationships of crocodyloids: Alcheringa, v. 20, p. 179–227. SERENO, P.C., 2001, SuperCroc: National Geographic Magazine, v. 200, p. 84–89. WEISHAMPEL, D. B., and YOUNG, L., 1996, Dinosaurs of the East Coast: Johns Hopkins University Press, Baltimore, 275 p. WILLIS, P.M.A., 1993, Trilophosuchus rackhami gen et sp. nov., a new crocodilian from the early Miocene limestones of Riversleigh, northwestern Queensland: Journal of Vertebrate Paleontology, v. 13, p. 90–98. WORTHY, T.H., ANDERSON, A.J., and MOLNAR, R.E., 1999, Megafaunal expression in a land without mammals—the first fossil faunas
82 from terrestrial deposits in Fiji (Vertebrata: Amphibia, Reptilia, Aves): Senckenbergiana Biologica, v. 79, p. 237–242. WU, X.-C., BRINKMAN, D.B., and FOX, R.C., 2001a, A new crocodylian (Archosauria) from the basal Paleocene of the Red Deer River valley, southern Alberta: Canadian Journal of Earth Sciences, v. 38, p. 1689–1704. WU, X.-C., RUSSELL, A.P., and BRINKMAN, D.B., 2001b, A review of
BOOK REVIEWS Leidyosuchus canadensis Lambe, 1907 (Archosauria: Crocodylia) and an assessment of cranial variation based upon new material: Canadian Journal of Earth Sciences, v. 38, p. 1665–1687. CHRISTOPHER BROCHU University of Iowa Department of Geoscience Iowa City, IA 52242