DOCSLIB.ORG

Journal of Dental Research

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Journal of Dental Research Journal of Dental Research http://jdr.sagepub.com/ The Origin and Evolution of the Human Dentition: A Palaeontological Review William K. Gregory J DENT RES 1920 2: 89 DOI: 10.1177/00220345200020011101 The online version of this article can be found at: http://jdr.sagepub.com/content/2/1/89.citation Published by: http://www.sagepublications.com On behalf of: International and American Associations for Dental Research Additional services and information for Journal of Dental Research can be found at: Email Alerts: http://jdr.sagepub.com/cgi/alerts Subscriptions: http://jdr.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav >> Version of Record - Mar 1, 1920 What is This? Downloaded from jdr.sagepub.com at COLUMBIA UNIV on September 26, 2014 For personal use only. No other uses without permission. THE ORIGIN AND EVOLUTION OF THE HUMAN DENTITION A PALAEONTOLOGICAL REVIEW WILLIAM K. GREGORY Columbia University and the American Museum of Natural History, New York City PART I. STAGES OF ASCENT FROM THE SILURIAN FISHES TO THE MAM- MALS OF THE AGE OF REPTILES CONTENTS I. Early stages of vertebrate evolution, seen in the fishes of the Paleozoic era.... 90 The ostracoderms of the Upper Silurian and Devonian ................... 90 The Devonian sharks ................................................ 91 The Devonian ganoids and lung-fishes .................................. 93 II. The emergence of four-footed, air-breathing vertebrates (primitive stegocephs) in the Upper Devonian and Lower Carboniferous ages ................. 97 III. The stem reptiles (Cotylosauria) and the mammal-like reptiles (Therapsida) of the late Paleozoic and early Mesozoic eras ............................ 100 IV. The Mesozoic mammals ................................................ 111 The Protodonta from the Upper Triassic of North Carolina ............... 111 Family Dromotheriidae ............. ................................ 111 Karoomys, a fore-runner of the Trituberculata from the Upper Triassic of South Africa.................................................... 114 Multituberculates from the Upper Triassic of England and Germany.. 115 Family Plagiaulacide ............ .................................. 115 Pachygeneleus, a possible ancestor of the multituberculates from the Storm- berg (Upper Triassic) of South Africa .............................. 117 The mammals of the Stonesfield Slate (Lower Jurassic)..................... 119 Order Triconodonta .............. ................................... 120 Family Triconodontide .......... .................................. 120 Order Trituberculata.... ...: .... 123 Family Amphitheriide ................. 123 Order Multituberculata? ................. 127 Stereognathus ................. 127 The South African mammal Tritylodon (Lower Jurassic) ..... .............. 128 Order Multituberculata? .............................................. 128 Family Tritylodontid.e............................................. 128 The mammals of the Purbeck and Morrison Beds (Upper Jurassic) .... .... .. 128 Order Multituberculata ................................................ 129 89 Downloaded from jdr.sagepub.com at COLUMBIA UNIV on September 26, 2014 For personal use only. No other uses without permission. 90 WILLIAM K. GREGORY Family Plagiaulacid .............................................. 129 Order Triconodonta ................................................. 130 Family Triconodontidze ............................................ 130 Order Triconodonta (?) .............................................. 133 Family Spalacotherildae ............................................ 133 Order Trituberculata ............................................... 136 Family Amphitherida ............................................ 136 Order Trituberculata ............................................... 139 Family Stylodontide ....................... ............... 139 Upper molars of Purbeck Trituberculata ................................ 141 Order Trituberculata ............................................... 147 Family Diplocynodontidw .......................................... 147 Summary and defence of the primitive characters of the Lower Jurassic Am- phitherium ...................................................... 149 V. The Late Mesozoic mammals (Upper Cretaceous) ....... .................. 151 Order Multituberculata............................................... 151 Family Polymastodontidae ................ .......................... 151 Order Marsupialia, Suborder Polyprotodontia ........................... 152 Family Cinolestida ........................................... 152 VI. The origin and evolution of the marsupials (Cretaceous to Recent) . 156 Suborder Polyprotodontia ....................... ...................... 157 Suborder Diprotodontia ............................................... 162 VII. Summary and conclusions for Part I ..................................... 166 I. EARLY STAGES OF VERTEBRATE EVOLUTION, SEEN IN THE FISHES OF THE PALEOZOIC ERA The later chapters in the evolution of the human dentition can only be understood in the light of the whole story, so it is advisable to begin at the beginning, or as near to the beginning as the palhonto- logical record extends. THE OSTRACODERMS OF THE UPPER SILURIAN AND DEVONIAN The problem of the origin of the vertebrates we must necessarily ignore, because the innumerable answers to it cannot be tested by an appeal to the paleontological record. We can, however, begin at a very early stage, represented by the ostracoderms of Silurian and Devonian times, which are on the whole the most primitive of all known chordates. It is true that the modern Amphioxus and the cyclostomes have acquired a world-wide reputation as primitive chordates but, in the absence of paleontological evidence, their real status is still unsettled; and, in their present conditions, they teem Downloaded from jdr.sagepub.com at COLUMBIA UNIV on September 26, 2014 For personal use only. No other uses without permission. EVOLUTION OF THE HUMAN DENTITION 91 with specializations which conceal their primitive characters. The Paleozoic ostracoderms, on the other hand, afford definite information of a pregnathostome stage of evolution which is lower and, as a whole, older, than any other group-of vertebrates. Although much excellent material is preserved in the museums of the world, none of these lowly fish-like chordates shows the least evidence of having attained "gill- arch jaws" of the normal vertebrate type. Some of them had a capacious mouth and, in the latest and more specialized ones (Bothrio- lepis, Pierichthys), the ossified dermal plates around the slit-like mouth acquired jagged edges and may have functioned in the prehension of food; but no known ostracoderm had either teeth or calcified oral and bronchial arches. For the most part they probably fed on small organisms found in the mud on the bottom of the streams in which they lived. Possibly they may have extracted the nutriment from FIG. 1. Birkenia elegans, A PRIM E FISH FROM TEE UPPER SILURIAN OF SCOTLAND Illustrating a stage of evolution before the formation of teeth and jaws. Natural size. After Traquair. the mud by ciliary tracts, as in Amphioxus and the larval lamprey. One of them (Birkenia) was shaped somewhat like Amphioxus and could perhaps dart about freely in the water, but most of them were depressed in form and probably lived on the bottom. None of them had attained the swift-swimming, predatory form, armed with strong teeth, which, there is much evidence to indicate, was the starting-point for the development of vertebrates higher in the scale. THE DEVONIAN SHARKS The numerous group of sharks, dating back to the Upper Silurian but well known only in the Devonian and later periods, are with good reason regarded as primitive in their class characters, since they all have the primitive vertebrate ground-plan of the endoskeleton. While most of the known ostracoderms had over-emphasized the exo- THE JOURNAL OF DENTAL RESEARCH, VOL. II, NO. 1 Downloaded from jdr.sagepub.com at COLUMBIA UNIV on September 26, 2014 For personal use only. No other uses without permission. 92 WIKLIAMK. GREGORY skeleton, the elasmobranchs very early built up an endoskeleton by precipitating calcium salts in the connective tissues and septa, which form a nucleus or core of the endoskeleton. They were active, preda- tory, fishes and developed further than did the ostracoderms the method of moving by rhythmic contraction of the muscle segments, FIG. 2. UNDER-SIDE OF THE HEAD OF Cladoselache fyleri, A. PRIMITIVE SHARK PROM THE UPPER DEVONIAN OF OHIO Showing the primary jaws, homologous with the bronchial arches, and bearing teeth on the skin inside the mouth. The eyes are surrounded by rows of sclerotic plates, which are homologous with the teeth and with the shagreen denticles of the skin. After Dean. or myomeres, arranged on either side of the mid-line. The develop- ment of the endoskeleton stiffened the median axis against the thrust of the myomeres and made possible the assumption of aggressive habits. In the earliest known sharks the mouth is supported by cartilagi- nous jaws of the "gill-arch" type. Even modern sharks retain much Downloaded from jdr.sagepub.com at COLUMBIA UNIV on September 26, 2014 For personal use only. No other uses without permission. EVOLUTION OF THE HUMAN DENTITION 93 evidence tending to show that the cartilage jaws are serially homolo- gous
Load more

Recommended publications
  • Owen—New Pur Beck Mammal. 199 But, Indeed, As Respects The
    Owen—New Pur beck Mammal. 199 But, indeed, as respects the controversy as to the comparative influence exercised by marine or atmospheric erosion in moulding our present land-surfaces, an equally vast lapse of time must in either case be assumed. The object of this paper is simply to suggest that the two denuding agencies have been always at work upon the surface of the earth, and that there is ample reason to consider the one to have produced effects quite as considerable as the other. II.—DESCRIPTION OP PART OP THE LOWEE JAW AND TEETH OF A SMAXL OOLITIC MAMMAL (STYLODON1 PUSILLVS, OW.) By Professor OWEN, F.E.S., F.G.S., etc. (PLATE X., FIGS. 1, 2.) T HAVE been favoured by the Eev. Peter B. Brodie, M.A., F.G.S., X with part of the lower jaw, including eight back teeth (PL X., Fig. 1, natural size), of a small mammal, nearly allied to Spalaco- therium tricuspidens, Ow., and from the same formation and locality, viz., the Marly bed Upper Oolite, Purbeck, Dorsetshire. The part of the lower jaw is embedded in a small block of the matrix, with the outer surface exposed: it includes the proportion of the ascending ramus supporting the coronoid process, a film of which only remains in the depression of the matrix, mainly indicat- ing its size and shape, and so much of the horizontal ramus as includes the alveoli of the nine posterior teeth, eight of which are in situ. The articular and angular processes, and the fore part of the ramus, have been broken away, and there is no indication in the matrix of the entire ramus having been imbedded therein; so it may be inferred, therefore, that the mutilation took place prior to imbedding.
    [Show full text]
  • Aspects of the Microvertebrate Fauna of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, Southern England
    ASPECTS OF THE MICROVERTEBRATE FAUNA OF THE EARLY CRETACEOUS (BARREMIAN) WESSEX FORMATION OF THE ISLE OF WIGHT, SOUTHERN ENGLAND By STEVEN CHARLES SWEETMAN M.A. (Oxon.) 1980 F.G.S. A thesis submitted in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy of the University of Portsmouth School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth, PO1 3QL, U.K. April, 2007 0 Disclaimer Whilst registered for this degree, I have not registered for any other award. No part of this work has been submitted for any other academic award. 1 Acknowledgements At inception of this project there was a significant risk that the Wessex Formation would not yield a microvertebrate fauna. I would, therefore, like to express special thanks to Dave Martill (University of Portsmouth) for his initial support and for securing the research scholarship which made this study possible. I would also like to thank him for his supervision, generous support, encouragement and advice thereafter. Special thanks also to Susan Evans (UCL) for her enthusiastic help and advice on all matters relating to microvertebrates in general, and lizards in particular, and to Jerry Hooker (NHM) for everything relating to mammals; also to Brian Gasson for his support in the field and for the generous donation of many exceptional specimens from his private collection. The broad scope of this study has engendered the help, support and advice of many others and I am grateful to all. At the University
    [Show full text]
  • Mammal Disparity Decreases During the Cretaceous Angiosperm Radiation
    Mammal disparity decreases during the Cretaceous angiosperm radiation David M. Grossnickle1 and P. David Polly2 1Department of Geological Sciences, and 2Departments of Geological Sciences, Biology, and Anthropology, rspb.royalsocietypublishing.org Indiana University, Bloomington, IN 47405, USA Fossil discoveries over the past 30 years have radically transformed tra- ditional views of Mesozoic mammal evolution. In addition, recent research provides a more detailed account of the Cretaceous diversification of flower- Research ing plants. Here, we examine patterns of morphological disparity and functional morphology associated with diet in early mammals. Two ana- Cite this article: Grossnickle DM, Polly PD. lyses were performed: (i) an examination of diversity based on functional 2013 Mammal disparity decreases during dental type rather than higher-level taxonomy, and (ii) a morphometric analysis of jaws, which made use of modern analogues, to assess changes the Cretaceous angiosperm radiation. Proc R in mammalian morphological and dietary disparity. Results demonstrate a Soc B 280: 20132110. decline in diversity of molar types during the mid-Cretaceous as abundances http://dx.doi.org/10.1098/rspb.2013.2110 of triconodonts, symmetrodonts, docodonts and eupantotherians dimin- ished. Multituberculates experience a turnover in functional molar types during the mid-Cretaceous and a shift towards plant-dominated diets during the late Late Cretaceous. Although therians undergo a taxonomic Received: 13 August 2013 expansion coinciding with the angiosperm radiation, they display small Accepted: 12 September 2013 body sizes and a low level of morphological disparity, suggesting an evol- utionary shift favouring small insectivores. It is concluded that during the mid-Cretaceous, the period of rapid angiosperm radiation, mammals experi- enced both a decrease in morphological disparity and a functional shift in dietary morphology that were probably related to changing ecosystems.
    [Show full text]
  • Jaw Shape and Mechanical Advantage Are Indicative of Diet in Mesozoic Mammals ✉ Nuria Melisa Morales-García 1 , Pamela G
    ARTICLE https://doi.org/10.1038/s42003-021-01757-3 OPEN Jaw shape and mechanical advantage are indicative of diet in Mesozoic mammals ✉ Nuria Melisa Morales-García 1 , Pamela G. Gill1,2, Christine M. Janis 1,3 & Emily J. Rayfield 1 Jaw morphology is closely linked to both diet and biomechanical performance, and jaws are one of the most common Mesozoic mammal fossil elements. Knowledge of the dietary and functional diversity of early mammals informs on the ecological structure of palaeo- communities throughout the longest era of mammalian evolution: the Mesozoic. Here, we analyse how jaw shape and mechanical advantage of the masseter (MAM) and temporalis (MAT) muscles relate to diet in 70 extant and 45 extinct mammals spanning the Late 1234567890():,; Triassic-Late Cretaceous. In extant mammals, jaw shape discriminates well between dietary groups: insectivores have long jaws, carnivores intermediate to short jaws, and herbivores have short jaws. Insectivores have low MAM and MAT, carnivores have low MAM and high MAT, and herbivores have high MAM and MAT. These traits are also informative of diet among Mesozoic mammals (based on previous independent determinations of diet) and set the basis for future ecomorphological studies. 1 School of Earth Sciences, Wills Memorial Building, University of Bristol, Bristol, UK. 2 Department of Earth Sciences, Natural History Museum, London, UK. ✉ 3 Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA. email: [email protected] COMMUNICATIONS BIOLOGY | (2021) 4:242 | https://doi.org/10.1038/s42003-021-01757-3 | www.nature.com/commsbio 1 ARTICLE COMMUNICATIONS BIOLOGY | https://doi.org/10.1038/s42003-021-01757-3 ur understanding of Mesozoic mammals has dramatically metric) has been used as a proxy for prey choice and feeding improved in the past three decades.
    [Show full text]
  • Morphological Evidence Supports Dryolestoid Affinities for the Living Australian Marsupial Mole Notoryctes
    Reviewing Manuscript Morphological Evidence supports Dryolestoid affinities for the living Australian Marsupial Mole Notoryctes Federico Agnolin, Nicolas Roberto Chimento Recent discoveries demonstrated that the southern continents were a cradle for the evolutionary radiation of dryolestoid mammals at the end of the Cretaceous. Moreover, it becomes evident that some of these early mammals surpassed the K/T boundary in South America, at least. Notoryctes is a poorly known living mammal, currently distributed in the s t deserts of central Australia. Due to its extreme modifications to fossoriality and peculiar n i anatomy, the phylogenetic relationships of this genus were debated in the past, but most r P recent authors agree in its marsupial affinities. A comparative survey of the anatomy of e Notoryctes reveals the poorly sustained marsupial affinities for the genus and striking r P plesiomorphies for a living mammal. Surprisingly, Notoryctes exhibits similarities with dryolestoids. Dryolestoids were a diverse and mainly mesozoic mammalian group phylogenetically nested between the egg-lying monotremes and derived therians. In particular, Notoryctes share a number of shared features with the extinct dryolestoid Necrolestes, from the Miocene of Patagonia. Both taxa conform a clade of burrowing and animalivorous dryolestoids that survived other members of their lineage probably due to their peculiar habits. Accordingly, Notoryctes constitutes a “living-fossil” from the supposedly extinct dryolestoid radiation, extending the biochron of the group more than 20 million years to the present day. The intermediate phylogenetic position of Notoryctes has the pivotal potential to shed light on crucial anatomical, physiological, ecological, and evolutionary topics in the deep transformation from egg-lying to placental mammals.
    [Show full text]
  • New Jurassic Mammials from Non-Tribosphenic Theria
    NEW JURASSIC MAMMIALS FROM COMO BLUFF, WYOMING, AND THE INTERRELATIONSHIPS OF NON-TRIBOSPHENIC THERIA DONALD R. PROTHERO BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 167: ARTICLE 5 NEW YORK: 1981 7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 34 v,~~~~~~~~~~~~~~~~~ "AT~~~ ~ ~ ~ 4K~~~~~~~~~~~~~~~4 4 ' j4'~~"T'4"444 4 ~~~~Z '4'''44444444~ 44~ *4~~4.4.4"~ " '- -,44~'4~':J"'-.'4 '~ " '" 4 4'', 4 ;q~W'7'44f~~~44~~~~~~~~444.4''"4~ ~ ~ '4'4"'~~~~~~~~~~~~~~' '4 '~~~~~~~~~~4''4,'7 ~ 4 ~ '.4 '4 4444.~ .444?,k4~4.4~X'4 '4~~~~/4:~~~~~.~~~'44444444.,~~~~~~~~~~ ~~ ~ ~ ~ ~~ 4"'' "'4 4" .~~~~~~~~~~~~~.. ' 4,. ~ ~ ~ ~ *44~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~N~4';i.44444'~ * g4 " ' 'A.~ ~~~" 74:'4'14~4 ' 7 -44-7p""'''4.'''444.44 *44~~~~~~~4.4...4'44 '~~~~~~~~~~~~~~'4 y,~'~ f ' ~ n #44~ 4 4~.44444'4 " 4 44',~~~~~~~~~~~4'~~~~~~~ 4. 4~~~~~~~~~~~~~~~~"4 7~~~~~~~~~'4 '4"''''4''' 4.''--. 4 ~~~~~~~ "'<''~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.4" 44444 "'.4 44V.. ~~'.'~~~4'.'.~~~~44"."4.. 4 4~~- '4' .4 4'' 4 4444 4' 4''~~~~~~~4~ ~ NEW JURASSIC MAMMALS FROM COMO BLUFF, WYOMING, AND THE INTERRELATIONSHIPS OF NON-TRIBOSPHENIC THERIA DONALD R. PROTHERO Graduate Student, Department of Geological Sciences Columbia University BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 167: ARTICLE 5 NEW YORK: 1981 BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Volume 167, article 5, pages 277-326, figures 1-12, tables 1-9 Issued February 26, 1981 Price: $3.20 a copy ISSN 0003-0090 Copyright ©) American Museum of Natural History 1981 CONTENTS Abstract ........................ 281 Introduction .............................. 281 Abbreviations ........................ 282 Acknowledgments ........................ 282 Stratigraphy and Localities ........................ 283 Systematic Descriptions ........................ 286 Taxa Known from Upper Jaws ........................ 286 Comotherium, New Genus .............................. 286 Melanodon and Herpetairus ......................... 289 Melanodon Simpson, 1927 .......................
    [Show full text]
  • University of Oklahoma Graduate College
    UNIVERSITY OF OKLAHOMA GRADUATE COLLEGE THE EVOLUTION OF EARLY TRIBOSPHENIC MAMMALS A DISSERTATION SUBMITTED TO THE GRADUATE FACULTY in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY By BRIAN MICHAEL DAVIS Norman, Oklahoma 2011 THE EVOLUTION OF EARLY TRIBOSPHENIC MAMMALS A DISSERTATION APPROVED FOR THE DEPARTMENT OF ZOOLOGY BY ______________________________ Dr. Richard Cifelli, Chair ______________________________ Dr. Laurie Vitt ______________________________ Dr. Nicholas Czaplewski ______________________________ Dr. Cynthia Gordon ______________________________ Dr. Stephen Westrop ______________________________ Dr. Richard Lupia © Copyright by BRIAN MICHAEL DAVIS 2011 All Rights Reserved. ACKNOWLEDGEMENTS I am deeply indebted to Dr. Richard Cifelli for his mentoring and friendship over the course of the past decade. I came to him with a year of college under my belt, and Rich immediately set me on a course to academic independence. His scholarship and immeasurable wit have been inspirations throughout my academic career. Also of special note is Dr. Cynthia Gordon, whom I have known for just as long. Cindy provided me with early guidance and, most importantly, teaching experience. She has been a model for that very important side of academia; for that, and for her friendship, I am grateful. I would also like to thank Dr. Nicholas Czaplewski for his accessibility and willingness to drop everything to discuss anything. Dr. Stephen Westrop has been highly instrumental in my understanding of phylogenetics and interpreting character evolution. Drs. Richard Lupia and Laurie Vitt have served as valued committee members, as well. My work could not have been possible without help and mentoring by the staff of the Department of Vertebrate Paleontology at the Sam Noble Oklahoma Museum of Natural History.
    [Show full text]
  • Mandibular and Dental Characteristics of Late Triassic Mammaliaform
    Mandibular and dental characteristics of Late Triassic PNAS PLUS mammaliaform Haramiyavia and their ramifications for basal mammal evolution Zhe-Xi Luoa, Stephen M. Gatesyb, Farish A. Jenkins Jr.c,d,1, William W. Amaralc,d,2, and Neil H. Shubina,3 aDepartment of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637; bDepartment of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912; cDepartment of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; and dMuseum of Comparative Zoology, Harvard University, Cambridge, MA 02138 Contributed by Neil H. Shubin, October 5, 2015 (sent for review July 29, 2015; reviewed by Guillermo W. Rougier and Timothy B. Rowe) As one of the earliest-known mammaliaforms, Haramiyavia clem- eleutherodontids or eleutherodontid-related forms with skeletons menseni from the Rhaetic (Late Triassic) of East Greenland has held from the Tiaojishan Formation (Middle to Late Jurassic) of China an important place in understanding the timing of the earliest (18–20) have greatly augmented the fossil record of haramiyidans, radiation of the group. Reanalysis of the type specimen using ranking them among the most diverse mammaliaform clades of the high-resolution computed tomography (CT) has revealed new de- Late Triassic and Jurassic. tails, such as the presence of the dentary condyle of the mammalian Historically, it has been a contentious issue whether haramiyidans jaw hinge and the postdentary trough for mandibular attachment (later expanded to include theroteinids and eleutherodontids) of the middle ear—a transitional condition of the predecessors to are closely related to the more derived multituberculates from crown Mammalia. Our tests of competing phylogenetic hypotheses the Middle Jurassic to Eocene (13) or represent a stem clade of with these new data show that Late Triassic haramiyids are a sep- mammaliaforms excluded from crown mammals (21, 22).
    [Show full text]
  • Supplemental Data
    Supplementary Information Diversity Data The Paleobiology Database [1] was used as the principal source for taxonomic ranges of the early mammalian genera. Much of the data in the Paleobiology Database came from Kielan- Jaworowska et al. [2], Lofgren [3], Clemens [4], Archibald [5], Hartman [6], Fox [7], Eaton and Cifelli [8], Montellano [9], Pearson et al. [10], and Lillegraven and McKenna [11]. Dental Functional Types For our purposes, triconodont refers to a molar with three primary cusps in a linear or obtuse- angled arrangement, such as in eutriconodontans, amphilestids, and morganucodontans. Symmetrodont molars are those with three primary cusps in a triangular arrangement and no talonid. Tribosphenic molars have dual-function trigonids and talonids such as in true tribosphenic eutherians, metatherians, and stem boreosphenidans, as well as pseudo-tribosphenic australosphenidans. Upper molars of plagiaulacoid multituberculates possess two rows of cusps and upper molars of cimolodont multituberculates have three rows, although the two dental types are also distinguished by number of incisors and premolars [2]. See Kielan-Jaworowska et al. [2] for descriptions of gondwanatherians, haramiyids, eupantotherians, and docodonts. One of the most contentious assignments for dental functional type involves the triconodonts (in the most general usage of the term) (see [71]). It should be noted, however, that even if alternative dental functional types were chosen for triconodont genera (e.g., if amphilestids were included with symmetrodonts instead of triconodontans), the overall diversity patterns of tribosphenic mammals and multituberculates relative to other dental types in the Cretaceous (the main focus of this portion of the study) would not be altered (figure 1).
    [Show full text]
  • HARPER-DISSERTATION-2019.Pdf
    CRANIODENTAL ADAPTATION AND HOMOPLASY IN EARLY MAMMALS by Anthony Maxwell Harper A dissertation submitted to Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy Baltimore, Maryland September, 2019 Abstract For the first two-thirds of their over 180-million-year history, mammals left a sparse fossil record. Often the only direct evidence of these early forms are small and unassociated craniodental fragments. Despite these limitations, the three chapters of this thesis support the effectiveness of this type of material for estimating the functional and autecological capacities in Mesozoic mammals, through high resolution imaging and morphometric analysis of the molariform dentition. Each of the three chapters is a self-contained study addressing separate topics relating to the evolution of dental and petrosal morphology. The common thread between all sections is that variation in craniodental structure among Mesozoic lineages is greater than would be expected based only on the disparity seen among extant small mammals. This is a result of both the more “modern” dynamics of dental evolution in more Mesozoic mammalian lineages than historically appreciated (Chapters 1 and 3), and the more “primitive” morphology of the inner ear, even in groups very closely related to extant crown therians (Chapter 2). In both cases, the craniodental morphologies described are outside the range of variation seen in extant species. Chapter 1 describes several new specimens from the herbivorous stem-therian mammal Reigitherium, from the Late Cretaceous of Patagonia. These newly available specimens demonstrate that the herbivorous molar morphology seen in Reigitherium is ii derived from the more plesiomorphic tuberculosectorial pattern seen in the South American endemic group Meridiolestida.
    [Show full text]
  • On the Fossil Mammalia from the Stonesfield Slate. by E
    FOSSIL MAMMALIA FROM THE STONESF1ELD SLATE. 407 On the Fossil Mammalia from the Stonesfield Slate. By E. S. Goodricli, F.L.S., Assistant to the Linacre Professor of Comparative Anatomy, Oxford. With Plate 26. EVER since the discovery, made some eighty years ago, of Mammalian remains in the Stonesfield Slate near Oxford, these fossils have excited the interest of naturalists, and have been the subject of much discussion amongst geologists and palaeontologists both in England and abroad. Nevertheless something still remains to be described in the few specimens which exist; and, while one of them has not yet been figured at all, others have been only inaccurately represented. I therefore propose to write a short history of each fossil, as far as it is known, giving figures when necessary; and to sum up the most important results which have been reached with regard to them by previous authors, together with some remarks as to the bearing of the facts ascertained by a careful study of the teeth belonging to these remains on the general question of the origin and homology of the cusps of Mam- malian teeth. Besides the fragment of the multituberculate form Stereo- gnathus, which I shall mention later, there are only twelve undoubted fossil Mammalian remains from the Stonesfield Slate at present known; ten of these are lower jaws, two are limb bones. Six of the fossil jaws are in the Oxford Museum, one in the York Museum, one in the private collection of 408 E. S. GOODBICH. Mr. Parker of Oxford ;l the two remaining jaws and the limb bones are in the British Museum.
    [Show full text]
  • Uncertain-Tree: Discriminating Among Competing Approaches to the Phylogenetic Analysis of Phenotype Data
    Downloaded from http://rspb.royalsocietypublishing.org/ on March 1, 2017 Uncertain-tree: discriminating among rspb.royalsocietypublishing.org competing approaches to the phylogenetic analysis of phenotype data Mark N. Puttick1,3,†, Joseph E. O’Reilly1,†, Alastair R. Tanner2, Research James F. Fleming1, James Clark1, Lucy Holloway1, Jesus Lozano-Fernandez1,2, Cite this article: Puttick MN et al. 2017 Luke A. Parry1, James E. Tarver1, Davide Pisani1,2 and Philip C. J. Donoghue1 Uncertain-tree: discriminating among 1School of Earth Sciences, and 2School of Biological Sciences, University of Bristol, Life Sciences Building, competing approaches to the phylogenetic 24 Tyndall Avenue, Bristol BS8 1TQ, UK analysis of phenotype data. Proc. R. Soc. B 3Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK 284: 20162290. MNP, 0000-0002-1011-3442; JEO, 0000-0001-9775-253X; JC, 0000-0003-2896-1631; http://dx.doi.org/10.1098/rspb.2016.2290 LH, 0000-0003-1603-2296; JL-F, 0000-0003-3597-1221; LAP, 0000-0002-3910-0346; PCJD, 0000-0003-3116-7463 Morphological data provide the only means of classifying the majority of life’s Received: 19 October 2016 history, but the choice between competing phylogenetic methods for the Accepted: 5 December 2016 analysis of morphology is unclear. Traditionally, parsimony methods have been favoured but recent studies have shown that these approaches are less accurate than the Bayesian implementation of the Mk model. Here we expand on these findings in several ways: we assess the impact of tree shape and maximum-likelihood estimation using the Mk model, as well as analysing Subject Category: data composed of both binary and multistate characters.
    [Show full text]