Hadrosaurs. David A. Eberth

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      A History of the Study of Ornithopods: Where Have We Been? Where Are We Now? and Where Are We Going?

       David B. Weishampel

       ABSTRACT

      Where ornithopod studies have been and where they are going is fascinating. I try to provide answers for the history of the study of ornithopod dinosaurs by collecting bibliographic data from the second edition of The Dinosauria. The resulting publication curves were examined for 10 intrinsic factors, nearly all of which increase through the first decade of the twenty-first century. These measures are used to take stock of present-day ornithopod studies and, finally, to try to predict our future as ornithopod researchers in this historically contingent world.

       INTRODUCTION

      From a historical perspective, knowledge about a taxonomic group can be judged by its publication rate. A zero rate may indicate a momentarily stalled interest in the group or a cessation of interest in it altogether (e.g., Kalodontidae Nopcsa, 1901), while a low rate suggests less than vigorous or meager research activity focused on the group (say, during a war or when there are few publishing scientists). Finally, a high publication rate may have many reasons, including new discoveries and new taxonomic recognition, and evolutionary controversy, to name a few.

      Compilations of taxa are not new to studies of dinosaurs, or even tetrapods or invertebrates (Sepkoski et al., 1981; Benton, 1985, 1998; Dodson, 1990; Weishampel, 1996; Sepkoski, 2002; Fastovsky et al., 2004; Wang and Dodson, 2004). However, this present compilation and survey differs from previous varieties in that it focuses on the number of papers published and the research areas those papers address.

      For Ornithopoda – the most abundant and diverse of which are hadrosaurids – the record of publication begins in 1825 with the publication of Mantell’s Iguanodon, and finishes with the numerous papers, some being issued via conventional journals as well as online-only journals, with no hard copies, of the present day. What this record looks like is presented in Figure 1.1. How it was obtained and how it is interpreted are the subjects of this chapter.

      Caveat: although this volume is the product of a symposium dedicated predominantly to hadrosaurs, which includes hadrosaurids proper as well as hadrosauroids, it has been extended by the organizers to include iguanodontians as well. By stretching it slightly more to include iguanodontians, we are practically down to the base of Ornithopoda. Hence, this chapter is about hadrosaurs – and more.

       MATERIALS AND METHODS

      In order to evaluate the rate of publication of papers dealing with ornithopod dinosaurs, the number of papers was tabulated on a per-decade basis from 1820–2010 from the bibliography of The Dinosauria, second edition (Weishampel et al., 2004). Containing 90 published pages of references on all dinosaurian taxa, this book is likely to be comprehensive enough for our current purposes. Because the decade of 2000–2010 was incomplete in that volume, the remainder of this decade was filled in proportionally based on the approximate representation during the first three and one-half years of the decade. That is, the 2000–2010 decadal numbers are projections based on tabulations from the first three and one-half years. Total papers and papers for each research category (see below) were adjusted by multiplying the raw totals for the first three and one-half years of the 2000–2010 decade by a factor of 2.86 to yield a total proportionally equivalent to other decades. This kind of correction was judged preferable to changing data sources (e.g., Web of Science), which would have resulted in an under-sampling of the more obscure literature.

      In addition to the total curve, I have attempted to characterize the papers that went into this total by identifying nine categories of research (Table 1.1). I provide general description of these categories, denoted in boldface text, below. These categories were usually assessed by title alone, but occasionally it was necessary to consult the paper itself to determine to which category it belonged. I made no account of footprints and eggshell papers, because it was often impossible to assess affinities of the tracks or shell beyond Dinosauria from the title of the paper.

Table 1.1. Categories of Ornithopod Research Identified in This Survey

      General taxonomy refers to those publications announcing new specific or generic taxa, or new taxonomic revisions that do not come under the heading of phylogeny (see below). For example, Gilmore’s (1913) announcement of Thescelosaurus neglectus is here considered a work of general taxonomy.

      Functional morphology is the category for papers involving a biomechanical or functional interpretation of an ornithopod anatomical system. An example of a functional morphology study is Alexander’s (1985) work on stance and gait in ornithopods among other dinosaurs.

      Phylogeny refers to those studies that attempt to portray the evolutionary history, or phylogeny, of the group. In recent years, these studies have emphasized cladistics in phylogenetic reconstruction (e.g., Prieto-Márquez, 2010), but also include a number of pre-Hennigian analyses (e.g., Galton, 1972).

      Biostratigraphy and taphonomy papers involve the geologic disposition of ornithopod specimens, whether within or among rock units. Rogers (1990) provided an example of how bonebed taphonomy can provide evidence for drought-related mortality in dinosaurs that include hadrosaurs.

      Biogeography includes studies that examine the geographic distribution of ornithopods either from a dispersal or vicariant perspective, or both. For example, Casanovas et al. (1999) examined the global distribution of lambeosaurine hadrosaurids, whereas Upchurch et al. (2002) considered the full spectrum of controls on dinosaur diversity, including that of ornithopods, as a function of biogeography and biostratigraphy.

      Paleoecology papers include those of Carrano et al. (1999) on convergence – or lack thereof – among ornithopods and ungulate mammals, and Varricchio and Horner (1993) on the significance of bonebeds in paleoecological interpretations, and are intended to address the reconstruction of particular taxonomically bound or free ecosystems of the past.

      Soft tissue studies have been generally limited to skin impressions. Examples include Osborn (1912) on the “mummy” of Edmontosaurus annectens