DOCSLIB.ORG

Late Cretaceous Theropod Dinosaur Diversity: Latitudinal Differences in North America and Implications for the K/T Extinctions

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Late Cretaceous Theropod Dinosaur Diversity: Latitudinal Differences in North America and Implications for the K/T Extinctions Catastrophic Events Conference 3148.pdf LATE CRETACEOUS THEROPOD DINOSAUR DIVERSITY: LATITUDINAL DIFFERENCES IN NORTH AMERICA AND IMPLICATIONS FOR THE K/T EXTINCTIONS. J.T. Sankey, Museum of Geology, South Dakota School of Mines and Technology, 501 E. Saint Joseph Ave., Rapid City, SD, 57701, U.S.A. [email protected] Although the evidence for an impact at the end of the collecting. Fossils from Alberta are in the Royal Tyrrell Cretaceous no longer makes this event controversial, the Museum of Paleontology (Drumheller, Alberta) and link between an impact and the terrestrial vertebrate those from Big Bend, at Louisiana State University extinctions is still controversial among some (Baton Rouge) and University of Texas at Austin. There paleontologists. The proposed ecosystem collapse as a are only five theropods from Big Bend: result of impact does not fit with the selective nature for Saurornitholestes, Richardoestesia cf. R. gilmorei, these extinctions. This paper reports on the differences Richardoestesia sp. nov., Paronychodon lacustris, and in theropod dinosaur diversity between southern and tyrannosaurid [2, 3, 4]. However, there are at more taxa northern North America during the last 10 million years from Albertan deposits, including Troodon, of the Cretaceous, and suggests that climatic and Dromaeosaurus, "Saurornithoides", and several environmental changes were important factors in the tyrannosaurids [5, 6, 7]. dinosaur extinctions. Paleoecologically, the Aguja and Javelina (late Temperature and rainfall differences along a north- Campanian to latest Maastrichtian) of Big Bend may south latitudinal gradient in the Western Interior of North have been more similar to the lower Scollard Formation America resulted in distinct terrestrial faunal and floral (latest Maastrichtian) of Alberta: both had warm, dry, provinces during the late Campanian. The open environments producing lower theropod diversity "Corythosaurus" dinosaur fauna was from Wyoming to and abundance. This connection between climate, the north and the "Kritosaurus" fauna occurred to the environment, and theropod diversity suggests that these south. These faunas correspond approximately to the factors were important in their extinctions. Aquillapollenites and Normapolles palynofloral provinces. More temperate and humid climates, with References more closed-canopy forests occurred to the north and warm, dry, and non-seasonal climates, with more open- [1] Lehman T.M. (1997) Dinofest Intl, Phila. Acad. Nat. canopy woodlands occurred to the south [1]. Sci., 223-240. [2] Standhardt B. R. (1986) Ph.D. Diss., Late Cretaceous southern theropods are not as well Louisiana State Univ., 1-298. [3] Rowe T. et al. (1992) J. known, especially from west Texas (Aguja and Javelina Vert. Paleo, 12, 472-493. [4] Sankey J.T. (1998) Ph.D. Formations, Big Bend National Park), where deposits Diss., Louisiana State Univ, 1-263. [5] Currie P. J. et al. have received less attention, have less outcrop area, and (1990) in Dinosaur Systematics: Perspectives and are generally less fossil-rich. Northern Late Cretaceous Approaches (eds, Carpenter, K. & Currie, P.J.) 107-125 theropods are better known, especially from Alberta (Cambridge Univ. Press). [6] Baszio, S. (1997b) Courier (Judith River and Edmonton Groups), due to more Forschungsinstitut Senckenberg, 196, 33-77. [7] Sankey, intense collection, more outcrop area, and richer J.T. et al. (in prep). [8] Baszio, S. (1997a) Courier deposits. Forschungsinstitut Senckenberg, 196, 1-31. Fossils studied are teeth collected by various workers by screening microvertebrate sites and by surface.
Load more

Recommended publications
  • Theropod Teeth from the Upper Maastrichtian Hell Creek Formation “Sue” Quarry: New Morphotypes and Faunal Comparisons
    Theropod teeth from the upper Maastrichtian Hell Creek Formation “Sue” Quarry: New morphotypes and faunal comparisons TERRY A. GATES, LINDSAY E. ZANNO, and PETER J. MAKOVICKY Gates, T.A., Zanno, L.E., and Makovicky, P.J. 2015. Theropod teeth from the upper Maastrichtian Hell Creek Formation “Sue” Quarry: New morphotypes and faunal comparisons. Acta Palaeontologica Polonica 60 (1): 131–139. Isolated teeth from vertebrate microfossil localities often provide unique information on the biodiversity of ancient ecosystems that might otherwise remain unrecognized. Microfossil sampling is a particularly valuable tool for doc- umenting taxa that are poorly represented in macrofossil surveys due to small body size, fragile skeletal structure, or relatively low ecosystem abundance. Because biodiversity patterns in the late Maastrichtian of North American are the primary data for a broad array of studies regarding non-avian dinosaur extinction in the terminal Cretaceous, intensive sampling on multiple scales is critical to understanding the nature of this event. We address theropod biodiversity in the Maastrichtian by examining teeth collected from the Hell Creek Formation locality that yielded FMNH PR 2081 (the Tyrannosaurus rex specimen “Sue”). Eight morphotypes (three previously undocumented) are identified in the sample, representing Tyrannosauridae, Dromaeosauridae, Troodontidae, and Avialae. Noticeably absent are teeth attributed to the morphotypes Richardoestesia and Paronychodon. Morphometric comparison to dromaeosaurid teeth from multiple Hell Creek and Lance formations microsites reveals two unique dromaeosaurid morphotypes bearing finer distal denticles than present on teeth of similar size, and also differences in crown shape in at least one of these. These findings suggest more dromaeosaurid taxa, and a higher Maastrichtian biodiversity, than previously appreciated.
    [Show full text]
  • At Carowinds
    at Carowinds EDUCATOR’S GUIDE CLASSROOM LESSON PLANS & FIELD TRIP ACTIVITIES Table of Contents at Carowinds Introduction The Field Trip ................................... 2 The Educator’s Guide ....................... 3 Field Trip Activity .................................. 4 Lesson Plans Lesson 1: Form and Function ........... 6 Lesson 2: Dinosaur Detectives ....... 10 Lesson 3: Mesozoic Math .............. 14 Lesson 4: Fossil Stories.................. 22 Games & Puzzles Crossword Puzzles ......................... 29 Logic Puzzles ................................. 32 Word Searches ............................... 37 Answer Keys ...................................... 39 Additional Resources © 2012 Dinosaurs Unearthed Recommended Reading ................. 44 All rights reserved. Except for educational fair use, no portion of this guide may be reproduced, stored in a retrieval system, or transmitted in any form or by any Dinosaur Data ................................ 45 means—electronic, mechanical, photocopy, recording, or any other without Discovering Dinosaurs .................... 52 explicit prior permission from Dinosaurs Unearthed. Multiple copies may only be made by or for the teacher for class use. Glossary .............................................. 54 Content co-created by TurnKey Education, Inc. and Dinosaurs Unearthed, 2012 Standards www.turnkeyeducation.net www.dinosaursunearthed.com Curriculum Standards .................... 59 Introduction The Field Trip From the time of the first exhibition unveiled in 1854 at the Crystal
    [Show full text]
  • Rule Booklet
    Dig for fossils, build skeletons, and attract the most visitors to your museum! TM SCAN FOR VIDEO RULES AND MORE! FOSSILCANYON.COM Dinosaurs of North America edimentary rock formations of western North America are famous for the fossilized remains of dinosaurs The rules are simple enough for young players, but and other animals from the Triassic, Jurassic, and serious players can benefit Cretaceous periods of the Mesozoic Era. Your objective from keeping track of the cards that is to dig up fossils, build complete skeletons, and display have appeared, reasoning about them in your museum to attract as many visitors as possible. probabilities and expected returns, and choosing between aggressive Watch your museum’s popularity grow using jigsaw-puzzle and conservative plays. scoring that turns the competition into a race! GAME CONTENTS TM 200,000300,000 160,000 VISITORS VISITORS PER YEAR 140,000 VISITORS PER YEAR 180,000 VISITORS PER YEAR 400,000 VISITORS PER YEAR Dig for fossils, build skeletons, and 340,000 VISITORS PER YEAR RD COLOR ELETONS CA GENUS PERIODDIET SK FOSSIL VISITORSPARTS 360,000 VISITORS PER YEAR PER YEAR attract the most visitors to your museum! VISITORS PER YEAR PER YEAR Tyrannosaurus K C 1 4 500,000 Brachiosaurus J H 1 3 400,000 ON YOUR TURN: TM SCAN FOR VIDEO Triceratops K H 1 3 380,000 RULES AND MORE! Allosaurus J C 2 Dig3 a first360,000 card. If it is a fossil, keep it hidden. FOSSILCANYON.COM Ankylosaurus K H 2 If it3 is an340,000 action card, perform the action.
    [Show full text]
  • A Revised Taxonomy of the Iguanodont Dinosaur Genera and Species
    ARTICLE IN PRESS + MODEL Cretaceous Research xx (2007) 1e25 www.elsevier.com/locate/CretRes A revised taxonomy of the iguanodont dinosaur genera and species Gregory S. Paul 3109 North Calvert Station, Side Apartment, Baltimore, MD 21218-3807, USA Received 20 April 2006; accepted in revised form 27 April 2007 Abstract Criteria for designating dinosaur genera are inconsistent; some very similar species are highly split at the generic level, other anatomically disparate species are united at the same rank. Since the mid-1800s the classic genus Iguanodon has become a taxonomic grab-bag containing species spanning most of the Early Cretaceous of the northern hemisphere. Recently the genus was radically redesignated when the type was shifted from nondiagnostic English Valanginian teeth to a complete skull and skeleton of the heavily built, semi-quadrupedal I. bernissartensis from much younger Belgian sediments, even though the latter is very different in form from the gracile skeletal remains described by Mantell. Currently, iguanodont remains from Europe are usually assigned to either robust I. bernissartensis or gracile I. atherfieldensis, regardless of lo- cation or stage. A stratigraphic analysis is combined with a character census that shows the European iguanodonts are markedly more morpho- logically divergent than other dinosaur genera, and some appear phylogenetically more derived than others. Two new genera and a new species have been or are named for the gracile iguanodonts of the Wealden Supergroup; strongly bipedal Mantellisaurus atherfieldensis Paul (2006. Turning the old into the new: a separate genus for the gracile iguanodont from the Wealden of England. In: Carpenter, K. (Ed.), Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs.
    [Show full text]
  • Implications for Predatory Dinosaur Macroecology and Ontogeny in Later Late Cretaceous Asiamerica
    Canadian Journal of Earth Sciences Theropod Guild Structure and the Tyrannosaurid Niche Assimilation Hypothesis: Implications for Predatory Dinosaur Macroecology and Ontogeny in later Late Cretaceous Asiamerica Journal: Canadian Journal of Earth Sciences Manuscript ID cjes-2020-0174.R1 Manuscript Type: Article Date Submitted by the 04-Jan-2021 Author: Complete List of Authors: Holtz, Thomas; University of Maryland at College Park, Department of Geology; NationalDraft Museum of Natural History, Department of Geology Keyword: Dinosaur, Ontogeny, Theropod, Paleocology, Mesozoic, Tyrannosauridae Is the invited manuscript for consideration in a Special Tribute to Dale Russell Issue? : © The Author(s) or their Institution(s) Page 1 of 91 Canadian Journal of Earth Sciences 1 Theropod Guild Structure and the Tyrannosaurid Niche Assimilation Hypothesis: 2 Implications for Predatory Dinosaur Macroecology and Ontogeny in later Late Cretaceous 3 Asiamerica 4 5 6 Thomas R. Holtz, Jr. 7 8 Department of Geology, University of Maryland, College Park, MD 20742 USA 9 Department of Paleobiology, National Museum of Natural History, Washington, DC 20013 USA 10 Email address: [email protected] 11 ORCID: 0000-0002-2906-4900 Draft 12 13 Thomas R. Holtz, Jr. 14 Department of Geology 15 8000 Regents Drive 16 University of Maryland 17 College Park, MD 20742 18 USA 19 Phone: 1-301-405-4084 20 Fax: 1-301-314-9661 21 Email address: [email protected] 22 23 1 © The Author(s) or their Institution(s) Canadian Journal of Earth Sciences Page 2 of 91 24 ABSTRACT 25 Well-sampled dinosaur communities from the Jurassic through the early Late Cretaceous show 26 greater taxonomic diversity among larger (>50kg) theropod taxa than communities of the 27 Campano-Maastrichtian, particularly to those of eastern/central Asia and Laramidia.
    [Show full text]
  • Phylogeny and Biogeography of Iguanodontian Dinosaurs, with Implications from Ontogeny and an Examination of the Function of the Fused Carpal-Digit I Complex
    Phylogeny and Biogeography of Iguanodontian Dinosaurs, with Implications from Ontogeny and an Examination of the Function of the Fused Carpal-Digit I Complex By Karen E. Poole B.A. in Geology, May 2004, University of Pennsylvania M.A. in Earth and Planetary Sciences, August 2008, Washington University in St. Louis A Dissertation submitted to The Faculty of The Columbian College of Arts and Sciences of The George Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy August 31, 2015 Dissertation Directed by Catherine Forster Professor of Biology The Columbian College of Arts and Sciences of The George Washington University certifies that Karen Poole has passed the Final Examination for the degree of Doctor of Philosophy as of August 10th, 2015. This is the final and approved form of the dissertation. Phylogeny and Biogeography of Iguanodontian Dinosaurs, with Implications from Ontogeny and an Examination of the Function of the Fused Carpal-Digit I Complex Karen E. Poole Dissertation Research Committee: Catherine A. Forster, Professor of Biology, Dissertation Director James M. Clark, Ronald Weintraub Professor of Biology, Committee Member R. Alexander Pyron, Robert F. Griggs Assistant Professor of Biology, Committee Member ii © Copyright 2015 by Karen Poole All rights reserved iii Dedication To Joseph Theis, for his unending support, and for always reminding me what matters most in life. To my parents, who have always encouraged me to pursue my dreams, even those they didn’t understand. iv Acknowledgements First, a heartfelt thank you is due to my advisor, Cathy Forster, for giving me free reign in this dissertation, but always providing valuable commentary on any piece of writing I sent her, no matter how messy.
    [Show full text]
  • Vertebrate Paleontology of the Cretaceous/Tertiary Transition of Big Bend National Park, Texas (Lancian, Puercan, Mammalia, Dinosauria, Paleomagnetism)
    Louisiana State University LSU Digital Commons LSU Historical Dissertations and Theses Graduate School 1986 Vertebrate Paleontology of the Cretaceous/Tertiary Transition of Big Bend National Park, Texas (Lancian, Puercan, Mammalia, Dinosauria, Paleomagnetism). Barbara R. Standhardt Louisiana State University and Agricultural & Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses Recommended Citation Standhardt, Barbara R., "Vertebrate Paleontology of the Cretaceous/Tertiary Transition of Big Bend National Park, Texas (Lancian, Puercan, Mammalia, Dinosauria, Paleomagnetism)." (1986). LSU Historical Dissertations and Theses. 4209. https://digitalcommons.lsu.edu/gradschool_disstheses/4209 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. INFORMATION TO USERS This reproduction was made from a copy of a manuscript sent to us for publication and microfilming. While the most advanced technology has been used to pho­ tograph and reproduce this manuscript, the quality of the reproduction is heavily dependent upon the quality of the material submitted. Pages in any manuscript may have indistinct print. In all cases the best available copy has been filmed. The following explanation of techniques is provided to help clarify notations which may appear on this reproduction. 1. Manuscripts may not always be complete. When it is not possible to obtain missing pages, a note appears to indicate this. 2. When copyrighted materials are removed from the manuscript, a note ap­ pears to indicate this. 3.
    [Show full text]
  • A Census of Dinosaur Fossils Recovered from the Hell Creek and Lance Formations (Maastrichtian)
    The Journal of Paleontological Sciences: JPS.C.2019.01 1 TAKING COUNT: A Census of Dinosaur Fossils Recovered From the Hell Creek and Lance Formations (Maastrichtian). ______________________________________________________________________________________ Walter W. Stein- President, PaleoAdventures 1432 Mill St.. Belle Fourche, SD 57717. [email protected] 605-210-1275 ABSTRACT: A census of Hell Creek and Lance Formation dinosaur remains was conducted from April, 2017 through February of 2018. Online databases were reviewed and curators and collections managers interviewed in an effort to determine how much material had been collected over the past 130+ years of exploration. The results of this new census has led to numerous observations regarding the quantity, quality, and locations of the total collection, as well as ancillary data on the faunal diversity and density of Late Cretaceous dinosaur populations. By reviewing the available data, it was also possible to make general observations regarding the current state of certain exploration programs, the nature of collection bias present in those collections and the availability of today's online databases. A total of 653 distinct, associated and/or articulated remains (skulls and partial skeletons) were located. Ceratopsid skulls and partial skeletons (mostly identified as Triceratops) were the most numerous, tallying over 335+ specimens. Hadrosaurids (Edmontosaurus) were second with at least 149 associated and/or articulated remains. Tyrannosaurids (Tyrannosaurus and Nanotyrannus) were third with a total of 71 associated and/or articulated specimens currently known to exist. Basal ornithopods (Thescelosaurus) were also well represented by at least 42 known associated and/or articulated remains. The remaining associated and/or articulated specimens, included pachycephalosaurids (18), ankylosaurids (6) nodosaurids (6), ornithomimids (13), oviraptorosaurids (9), dromaeosaurids (1) and troodontids (1).
    [Show full text]
  • A Fast-Growing Basal Troodontid (Dinosauria: Theropoda) from The
    www.nature.com/scientificreports OPEN A fast‑growing basal troodontid (Dinosauria: Theropoda) from the latest Cretaceous of Europe Albert G. Sellés1,2*, Bernat Vila1,2, Stephen L. Brusatte3, Philip J. Currie4 & Àngel Galobart1,2 A characteristic fauna of dinosaurs and other vertebrates inhabited the end‑Cretaceous European archipelago, some of which were dwarves or had other unusual features likely related to their insular habitats. Little is known, however, about the contemporary theropod dinosaurs, as they are represented mostly by teeth or other fragmentary fossils. A new isolated theropod metatarsal II, from the latest Maastrichtian of Spain (within 200,000 years of the mass extinction) may represent a jinfengopterygine troodontid, the frst reported from Europe. Comparisons with other theropods and phylogenetic analyses reveal an autapomorphic foramen that distinguishes it from all other troodontids, supporting its identifcation as a new genus and species, Tamarro insperatus. Bone histology shows that it was an actively growing subadult when it died but may have had a growth pattern in which it grew rapidly in early ontogeny and attained a subadult size quickly. We hypothesize that it could have migrated from Asia to reach the Ibero‑Armorican island no later than Cenomanian or during the Maastrichtian dispersal events. During the latest Cretaceous (ca. 77–66 million years ago) in the run-up to the end-Cretaceous mass extinc- tion, Europe was a series of islands populated by diverse and distinctive communities of dinosaurs and other vertebrates. Many of these animals exhibited peculiar features that may have been generated by lack of space and resources in their insular habitats.
    [Show full text]
  • Competition Structured a Late Cretaceous Megaherbivorous Dinosaur Assemblage Jordan C
    www.nature.com/scientificreports OPEN Competition structured a Late Cretaceous megaherbivorous dinosaur assemblage Jordan C. Mallon 1,2 Modern megaherbivore community richness is limited by bottom-up controls, such as resource limitation and resultant dietary competition. However, the extent to which these same controls impacted the richness of fossil megaherbivore communities is poorly understood. The present study investigates the matter with reference to the megaherbivorous dinosaur assemblage from the middle to upper Campanian Dinosaur Park Formation of Alberta, Canada. Using a meta-analysis of 21 ecomorphological variables measured across 14 genera, contemporaneous taxa are demonstrably well-separated in ecomorphospace at the family/subfamily level. Moreover, this pattern is persistent through the approximately 1.5 Myr timespan of the formation, despite continual species turnover, indicative of underlying structural principles imposed by long-term ecological competition. After considering the implications of ecomorphology for megaherbivorous dinosaur diet, it is concluded that competition structured comparable megaherbivorous dinosaur communities throughout the Late Cretaceous of western North America. Te question of which mechanisms regulate species coexistence is fundamental to understanding the evolution of biodiversity1. Te standing diversity (richness) of extant megaherbivore (herbivores weighing ≥1,000 kg) com- munities appears to be mainly regulated by bottom-up controls2–4 as these animals are virtually invulnerable to top-down down processes (e.g., predation) when fully grown. Tus, while the young may occasionally succumb to predation, fully-grown African elephants (Loxodonta africana), rhinoceroses (Ceratotherium simum and Diceros bicornis), hippopotamuses (Hippopotamus amphibius), and girafes (Girafa camelopardalis) are rarely targeted by predators, and ofen show indiference to their presence in the wild5.
    [Show full text]
  • Dinosaurs of Portugal Dinosaures Du Portugal
    C. R. Palevol 2 (2003) 77–95 Systematic Palaeontology / Paléontologie systématique (Vertebrate Palaeontology / Paléontologie des Vertébrés) Dinosaurs of Portugal Dinosaures du Portugal Miguel Telles Antunes a,b,c,d, Octávio Mateus c,d,* a Academia de Ciências de Lisboa, Portugal b European Academy of Sciences and Humanities, 60, rue Monsieur-le-Prince, 75006 Paris, France c Centro de Estudos Geológicos, Faculdade de Ciências e Tecnologia (UNL)/Quinta da Torre, 2829-516 Caparica, Portugal d GEAL - Museu da Lourinhã, 2530 Lourinhã, Portugal Accepted 6 January 2003 Written on invitation of the Editorial Board Abstract A synthesis on the state of art on dinosaur knowledge in Portugal is presented. The following genera have been recognized: Ceratosaurus, Torvosaurus, Lourinhanosaurus, Allosaurus, cf. Compsognathus, Stokesosaurus, cf. Richardoestesia, cf. Archaeopteryx, Euronychodon, cf. Paronychodon, Dinheirosaurus, Lourinhasaurus, Lusotitan, cf. Pleurocoelus, Lusitanosau- rus, Dacentrurus, Dracopelta, Phyllodon, Hypsilophodon, Alocodon, Trimucrodon, Draconyx, Iguanodon, and Taveirosaurus. Most are from Late Jurassic localities at the Lourinhã area and Guimarota. A new genus, Lusotitan, is here raised to include the Late Jurassic ‘Brachiosaurus’atalaiensis. Lower Cretaceous until Cenomanian material is scarce, except for dinosaur footprints. An interesting Late-Cretaceous, mostly small dinosaur association has been collected between Aveiro and Taveiro. To cite this article: M.T. Antunes, O. Mateus, C. R. Palevol 2 (2003) 77–95. © 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. Résumé On présente une synthèse concernant l’état actuel des connaissances sur les dinosaures du Portugal. Les genres suivants ont été reconnus : Ceratosaurus, Torvosaurus, Lourinhanosaurus, Allosaurus, cf. Compsognathus, Stokesosaurus, cf. Richardoes- tesia, cf. Archaeopteryx, Euronychodon, cf. Paronychodon, Dinheirosaurus, Lourinhasaurus, Lusotitan, cf.
    [Show full text]
  • Body-Size Evolution in the Dinosauria
    8 Body-Size Evolution in the Dinosauria Matthew T. Carrano Introduction The evolution of body size and its influence on organismal biology have received scientific attention since the earliest decades of evolutionary study (e.g., Cope, 1887, 1896; Thompson, 1917). Both paleontologists and neontologists have attempted to determine correlations between body size and numerous aspects of life history, with the ultimate goal of docu- menting both the predictive and causal connections involved (LaBarbera, 1986, 1989). These studies have generated an appreciation for the thor- oughgoing interrelationships between body size and nearly every sig- nificant facet of organismal biology, including metabolism (Lindstedt & Calder, 1981; Schmidt-Nielsen, 1984; McNab, 1989), population ecology (Damuth, 1981; Juanes, 1986; Gittleman & Purvis, 1998), locomotion (Mc- Mahon, 1975; Biewener, 1989; Alexander, 1996), and reproduction (Alex- ander, 1996). An enduring focus of these studies has been Cope’s Rule, the notion that body size tends to increase over time within lineages (Kurtén, 1953; Stanley, 1973; Polly, 1998). Such an observation has been made regarding many different clades but has been examined specifically in only a few (MacFadden, 1986; Arnold et al., 1995; Jablonski, 1996, 1997; Trammer & Kaim, 1997, 1999; Alroy, 1998). The discordant results of such analyses have underscored two points: (1) Cope’s Rule does not apply universally to all groups; and (2) even when present, size increases in different clades may reflect very different underlying processes. Thus, the question, “does Cope’s Rule exist?” is better parsed into two questions: “to which groups does Cope’s Rule apply?” and “what process is responsible for it in each?” Several recent works (McShea, 1994, 2000; Jablonski, 1997; Alroy, 1998, 2000a, 2000b) have begun to address these more specific questions, attempting to quantify patterns of body-size evolution in a phylogenetic (rather than strictly temporal) context, as well as developing methods for interpreting the resultant patterns.
    [Show full text]