SASS SSRIS A Note toetactne Property of Remington Kellogg ln Memory of Remington Hellogg \d69 cs Mammalogist 2s Fe omer Z : EL, Los Pal eontolo qg ist ai —~ _ te mtgttie Sth Ps a oe THE AGE.OF MAMMALS THE MACMILLAN COMPANY NEW YORK - BOSTON - CHICAGO ATLANTA + SAN FRANCISCO MACMILLAN & CO., LimiTED LONDON - BOMBAY « CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Ltp. TORONTO XX Y ir “THE AGE OF MAMMALS TN EUROPE, ASIA AND NORTH AMERICA BY HENRY FAIRFIELD OSBORN LL.D. (Trinity, Princeton, Cotumsia), Hon. D.Sc. (CAMBRIDGE) VERTEBRATE PALZONTOLOGIST OF THE UNITED STATES GEOLOGICAL SURVEY, DACOSTA PROFESSOR OF ZOOLOGY IN COLUMBIA UNIVERSITY, CURATOR OF VERTEBRATE PALZON- TOLOGY IN THE AMERICAN MUSEUM OF NATURAL HISTORY se ILLUSTRATED SEP 18 19 Netu Bork THE MACMILLAN COMPANY 1910 All rights reserved CopyricHT, 1910, By HENRY FAIRFIELD OSBORN. Set up and electrotyped. Published October, rg10. Norwood 4press J.S. Cushing Co. — Berwick & Smith Co. Norwood, Mass., U.S.A. TO MY BRITISH TEACHERS THOMAS HENRY HUXLEY AND FRANCIS MAITLAND BALFOUR THIS COMPARATIVE STUDY OF CHNOZOIC MAMMALS IN THE OLD AND NEW WORLDS IS DEDICATED PREFACE To the memory of Huxley as my chief teacher in comparative anatomy, as well as to that of Balfour, my first teacher in embryology, I have dedicated this work. Huxley set forth the logic of Darwin as applied to paleontology ; Balfour’s genius was beyond imitation, but his pupils may follow the example of his ardent enthusiasm and his genial way of living the life of science. Only a few men of the last century had the gift of speaking in clear language both to the learned and unlearned, and the greatest of these was Huxley. To write both for the man of one’s own profession and for the layman, to be accurate and abreast of the specialist who knows as much or more of a subject than you do, while intelligible to the non-specialist — there is the difficulty. Many times have I thought to myself in the course of the preparation of these and similar lectures how simple it would be to address either audience separately. Yet I consider it fortunate that both are with us, because I share Huxley’s confidence in addressing those who are willing to do a little serious thinking in order to enjoy the vast vistas of interesting truth which come as the reward of effort. I share also his conviction that it is the duty of the man of science to devote a certain part of his time, however absorbed in research he may be, to an honest attempt to scatter scientific truth. Although I may not claim that any parts of this volume are light reading, I have endeavored both to hold the attention of those who are already within the charmed temples of paleontology and to attract new votaries to its shrines. It should, however, be clearly understood that considerable sections of this work are purely documentary and may be passed over rapidly by the general reader. Time and place are the main theme of this work rather than descent, which has been the main theme of all previous general treatises on the Cenozoic mammals; it is a study of the sources or birthplaces of the several kinds of mammals, of their competitions, migrations, and extinctions, and of the times and places of the occurrence of these great events in the world’s history. To set forth this history in all its grandeur, it is interesting to consider the question of past environments, such as the past geography (palzogeography) of the earth, the changes in climate and in the earth’s surface which conditioned the evolution of plant life (palzobotany) as the primary source of food supply for the mammals. Thus geology, geography, botany, and climate are treated as leading to a clear understanding of each of the successive groups and movements of mammalian life. In a way this work marks the completion of a special line of study vil Vili PREFACE which I began in 1898 and have been pursuing at intervals for eleven years, namely, the comparison of the new and old world life. It is thus an exposition and explanation of two presidential addresses of mine delivered before the New York Academy of Sciences in February, 1899 and 1900, entitled “Correlation between Tertiary Mammal Horizons of Europe and America,” also of a paper published recently by the United States Geological Survey, entitled “Cenozoic Mammal Horizons of Western North America.” In the Introduction I have drawn freely on several popu- lar addresses of mine, “The Rise of the Mammalia in North America” (1893), “Ten Years’ Progress in the Mammalian Paleontology of North America” (1905), “The Present Problems of Paleontology ” (1905), and, finally, “ Paleontology,” an article prepared for the forthcoming edition of the Encyclopedia Britannica. The stimulus to put these studies into the present collected form was given by the generous foundation of the Harris Lectureship in Northwestern University by Mr. Norman Waite Harris in 1906. As originally delivered in December, 1908, to the students of that institution, the lectures were in general popular form. It has required a year to verify and expand them, so that the volume is practically of date December 31, 1909. The oral style appropriate to the lecture has given way necessarily to the written style; there is a greater fullness and I trust a greater clearness. In gathering the materials for the preparation of these addresses and of this volume, my foremost acknowledgments are due to the profound and accurate researches of my friend, Professor Charles Depéret of the University of Lyons, as well as of my former student and present colleague in the American Museum of Natural History, Dr. William Diller Matthew. The very precise data which they have brought together, coupled with my own researches and observations on the mammals of the Old and New Worlds, have furnished the chief material for the broad comparisons and generaliza- tions which I have attempted to make. I have also reviewed the general literature of the subject, and I desire to acknowledge the aid of my former student and present research assistant, Mrs. Johanna Kroeber Mosenthal, who has been intrusted with a large part of the reading, translation, and collation of facts derived from the foreign and American sources. The reader will observe that the collections in the American Museum of Natural History as well as our observations in the field are very largely drawn upon. These have been gathered and planned during the past twenty years under my direction, and the fullest acknowledgments are due to the able and energetic explorers who have helped to bring these rare treasures of the past together, especially to Dr. J. L. Wortman, Dr. W. D. Matthew, Mr. J. W. Gidley, Mr. 0. A. Peterson, Mr. Walter Granger, Mr. Barnum Brown, and Mr. Albert Thomson. The necessity for great precision in field records, especially for recording the exact levels on which specimens are found, I have impressed constantly upon the minds of these explorers. Such precise records have important bearing on the question of time as well as : PREFACE 1x of evolution; they were omitted in the pioneer work of Leidy, Marsh, and Cope. This precision in America, coupled with the precision especially of Professor Depéret’s records and observations in France, has rendered possi- ble the present comparison between the New and Old Worlds. Large collections have been secured also by the museums of Princeton University and the University of California, by the Carnegie Museum of Pittsburgh, the Field Museum of Natural History of Chicago; and some few additions have been made in recent years to the famous collection brought together by Professor Marsh in Yale University. The equally famous collection of Cope is now the property of the American Museum of Natural History. The space and time distribution of the mammal life of Europe as set forth in Depéret’s articles in the Comptes rendus, I have brought together in visual form in a new series of maps. The American records, sections, and maps are drawn from those brought together in my recent bulletin, “Cenozoic Mammal Horizons of Western North America,” together with some additions from my observations in Africa and from the very latest work in Wyoming. I am here indebted especially to the codperation of Mr. Granger. The United States Geological Survey has given permission to reproduce many of the illustrations from my bulletin. The reader who finds it difficult to picture the rare and ancient forms of mammals has to thank that gifted artist of the life of the extinct world, Mr. Charles R. Knight, for the series of restorations drawn under my personal direction, which are brought together for the first time in this volume. It is always to be understood that such restorations represent hypotheses merely or approximations to the truth. We know little or nothing about the color markings of these extinct forms, and even the attempt to outline the proportions of the limbs and body is somewhat hazard- ous; yet these representations serve, in connection with photographs of the skeletons, to give us a sense of the general size and proportion, and to assemble before the eye such inferences as to the homes and habits of the animals as can be deduced from their skeletons, especially from the teeth and feet, and from the kind of rock in which their remains have been discovered. Mrs. L. M. Sterling has prepared many of the anatomical and geological illustrations with artistic fidelity. Mr. Aleth Biorn and Mrs. Mosenthal have prepared the Depéret series of maps. Mr. Erwin 8. Christman has contributed several drawings. The field photographs are chiefly the work of Mr. Albert Thomson and other members of our field parties. ‘lhe photo- graphs of skeletons are part of the remarkable series executed by Mr. A. E. Anderson. I am indebted to many workers in other institutions for generous assistance. In the paleobotanie work I have enjoyed the assistance of Miss Elsbeth Kroeber, also of Messrs. F. A. Knowlton, A. A. Hollick, and T. D. A. Cockerell. X PREFACE The entire text has been studied by Dr. W. D. Matthew and Dr. W. K. Gregory, to whom I am indebted for many valuable criticisms and suggestions. A liberal appropriation by the trustees of the American Museum of Natural History has facilitated the large amount of special study, which has been devoted to the preparation and illustration of this work. I have also recently been transferred from a teaching to a research professorship in Columbia University. Finally, the especial purpose of the work is to spread the knowledge of paleontology in the United States. It will be cause for regret if the extended information as to localities, here brought together for the first time, should lead to the hasty or untrained collection of fossils, or to the still more harmful ill-considered description of new species. All descriptions should be preceded by painstaking examination of previous types, and should be accompanied by figures and short, clear diagnoses. All type specimens should find their way into large central and accessible museums where they can be readily examined. HENRY FAIRFIELD OSBORN. AMERICAN MusEuM OF NATURAL HISTORY, DECEMBER 31, 1909. CONTENTS PAGE PREFACE ° ° ° . . . ° - ° ° . ° : é Vv CHAPTER I. INTRODUCTION J. PuHrLosopny OF THE STRUCTURE OF MAMMALS . : : ‘ : 1 Rise of Paleontology . : : : : ; : ; 3 1 Law of Correlation. : : : - 2 Systematic Paleontology . : : : : < : - : | Darwin’s Influence ; : : : : : : ; ; : 5 Primitive and Progressive Stages : : : : ° : 7 Precise and Philosophical Research . : - 5 . , 7 Influence of American Discovery : : : ° : : Eres 9 Primitive and Progressive Forms of Teeth. : x : : : e 10 Primitive and Progressive Foot Structure . 6 : é : : on readies Primitive and Progressive Skull Structure . : : : - : et AY II. MAMMALS AND THEIR ENVIRONMENT . 5 : ; : : : ¢. (18 Origin and Migration . : : : : : : : : fe 1) The Law of Adaptive Radiation: 5 - : - ; : : i tee The Orders of Mammals. : < : . : 2 ; ooo Adaptive Radiation and Geogr apt : : : 5 ; j Pyne!) The Polyphyletic Law . : : : - : : : oy eo Adaptations to Alternations of Habitat . - : : : : ot Voi The Law of Analogous Evolution : : : - : : : Pi oe The Law of Irreversibility of Evolution . : : - : : . o4 III. GroGraruic or SPACE DisTRIBUTION OF MAMMALS. é : £ 48h Zoégeography ; s . : F : “ : : : mie Migration Routes and Barriers . : 5 : : : : : Sie IV. Geroroeic or Time DistripuTion OF MAMMALS. : : : Paes!) Time Divisions . : ; 9 5 i : ; : é : igo Preliminary Correlation . 3 . : . : : ° : . 41 Importance of Time Correlation . : : s : : ; : . 42 Time Value of Fossils . : 5 : : : : : : . . 44 Geologic Formations and Life Zones . : : ° : : : oy eke Progressive Correlation : § 5 : : ‘ : 5 ot 8 50 Geologie Formations as a Record of Environments . . 5 ° . OD V. Duration OF THE AGE OF MAMMALS ; s 5 X : . eos Mountain Births . : : ; : : ° 5 : . OS Modes of Estimating Ceenozoic cence - ; ; . . . =) earn Length of the Cznozoic Era : é : : : . . . ow Gs VI. THe Worip Suppty or MAMMALS . : 5 : . . . . 64 Mammals of the Northern Hemisphere, Holarctica . ‘ ° . > 16D Africa as a Center of Mammalian Evolution . - rat ° Sy Lite) xl xii CONTENTS Antarctica, Australia, and South America . : A “ - - - Australasia or Notogeea : - : - ° : . ° ° : South America or Neogea . ~ . : . . . . . . : General Conclusions. : : - ; . ‘ . ° ° : 7. PALHZOGEOGRAPHY . ; ; : ; - - : ° ° ° : CHAPTER Il. THE EOCENE PALAOGEOGRAPHY OF EOCENE EUROPE . 4 3 : - 4 - é PALEZOGEOGRAPHY OF NortTH AMERICA . A : 6 : : c Atlantic Border Region ; 4 : . 5 : . . . . Mountain Region. 5 : : : ‘ ° . . . ° Mountain Basin Deposits : : 4 5 ; : . * + Voleanic Materials . : A is 6 4 . - “ . 3 Pacific Coast. Close of the Cretaceous ; a A 5 ; A 4 LATE CRETACEOUS AND EARLY EOCENE FLORA 6 , ; ALTERNATE UNION AND DISUNION OF EUROPEAN AND NORTH AMERICAN LIFE Faunal Phases . : The Archaic Manuele: : : j : F j F A I. THe Basat Eocene LIFE oF EUROPE AND AMERICA : 3 Close of the Age of Reptiles and Beginning of the Age of Men ouiale Seashore Transition Beds in Europe Continental Transition Beds in America Animals of the First Faunal Zone . 4 ; : , : Basal Eocene, First Faunal Phase : ; 3 c : . Basal Eocene of Europe, Thanetian Roemanous : - . Basal Eocene of North America . : é 6 3 a Puerco Life ; A é , ; : 3 5 3 Torrejon Life. : ; : ; F : , 5 Il. Tue Lower Eocenrt LIFE or Europe AND AMERICA . 3 3 Lower Eocene, Second Faunal Phase . : : : ; : Lower Eocene Life of Europe : Sparnacian Life, Coryphodon Zone Lower Ypresian Formations . Upper Ypresian Formations . : : : . . Lower Eocene Life of North America, Wasatch, and Wind River . Formations of the Coryphodon Zone Wasatch Life . Wind River : : : Fishes of the Green River Shales . Ill. Mrirppie anp Upper Eocene Lire or Evrore anp NortTH AMERICA . Third Faunal Phase. : . . . Middle and Upper Eocene Life of Europe . : - Geological Succession. : : ; é : . : : 4 Mammalian Succession . Collective Fauna of the Phosphoriies of Guerey : Middle and Upper Eocene Life of the Rocky Mountain Region . Geology of the Middle Eocene PAGE 75 ae 78 100 102 102 103 104 106 107 1b 112 113 114 15 117 118 119 124 128 135 137 138 140 143 146 151 153 157 CONTENTS xii PAGE Bridger Fish and Reptile Fauna. - : . ‘ ° : . 160 The Succession of Middle Eocene Mammals : - : - ea ial Upper Eocene . : : : : : : : : : : 166 The Atlantic Coast Region . ; : ‘ : ; ba te (0) Causes of Extinction of the Archaic @rdems of Basie Marimals . oe ie CHAPTER III. THE OLIGOCENE FourtH FauNAL PHASE . : : 3 : , : : : : SM Ui) Mammals of the Lower Oligocene. : ° : 5 ° : = »L79 PALAOGEOGRAPHY : . : : 5 . = : - 5 a 4 6182 Continental Connections. 5 : : - : - ; : Se bom Geographic Changes in Europe . ‘ : : : : : : . 183 FLORA AND CLIMATE . : - : : ; = . ° : : . 184 Europe. . . : : . : : “ ° A - ; . 184 America : : : : : : . é ° : 5 ; . 185 PuystoGRAPHIC CONDITIONS : 3 : : = : . ° : - 185 Europe . : : : : : ‘ 5 . : ° : : > 2185 I. OLigoceNr Lire or Evrore : "5 : : : : : BE EASY Lower Oligocene, Sannoisian —. : ° : : : : q 2 UeLST Middle Oligocene, Stampian - : . : : : : : oa. 90) Upper Oligocene, Aquitanian . : - : ° : : : aloe Il. Upper Eocene AnD OLIGOCENE Lire oF NortH AFRICA : : ~ £99 Geology of the Fayim Deposits . : ; 4 : . a ees “ 2200 Fauna of the Fayam Deposits. : : : : : : , aol Ill. Oxicocene Lire oF AMERICA . : ; . : : : : . 204 Geologie Conditions . ; 5 : : : : A : . . 204 Prevailing Mammal Types . ‘ d : - : ; : 5 2208 Lower Oligocene, Titanotherium Zone . - : : ; 5 e110) Middle Oligocene, Oreodon Zone : é ° . ; ; ; oe UL Upper Oligocene, Protoceras Zone. . ° é : 5 4 wee0 Upper Oligocene, Diceratherium Zone : < : . : : ee ea Upper Oligocene, Promerycochcerus Zone . é : : : : sual Causes of Extinction of Oligocene Mammals. - : : . wea CHAPTER IV. THE MIOCENE Firtra FAuNAL PHASE. 5 : 5 : : : - : : 5 . 242 FLORA AND CLIMATE OF EUROPE F , : : : : - : s. 242 CONTINENTAL CONNECTIONS : : : : : : : : : . 244 PuysioGRAPHIc CHANGES IN EuROPE : ‘ : j A ; ; . 246 Miocene Lire or Europe AND AMERICA COMPARED. : 5 : . 246 I. Miocene Lire or Europe . . ; , 3 : 4 : ; . 249 The Older Fauna 5 : : : : : : : : : . 249 Lower Miocene or Burdigalian . : : E : : : : a eo) CONTENTS Middle Miocene or Vindobonian 1. Stage of Sansan 2. Stage of Simorre 3. Stage of St. Gaudens. Middle Miocene Primates Upper Miocene or Pontian . Physiographie Conditions Pikermi . ; Characteristic Life . Upper Miocene Primates The Seven Rhinoceros Phyla of the NU pcote Mippie Miocene Lire or AsIA. Miocene Lire oF NortTH AMERICA . Transition, Arikaree Ancient Physiographic Gondinent Miocene Flora ) > y' oO OUs aS Oo on RN bw bh WH bb bt tO Co co co oS “Tote bo Ss bt © Lower Miocene, Metsoceherns Fane 5 ' Middle Miocene, Ticholeptus Zone 3 Upper Miocene, Hipparion and Procamelus Zone Miocene History of American Deer CHAPTER V. THE PLIOCENE bo bw hw NH WW bd to [0 9) (0 6) Orv bo co So © wo Io SrxtH FAUNAL PHASE . PLIOCENE LIFE OF EUROPE Modernization Paleeogeography Flora and Climate Pliocene Birds Pliocene Primates Partial List of Mammals Faunal Break with the Miocene . Faunal Divisions . 4 Lower Pliocene or Plaisancian Middle Pliocene or Astian . Upper Pliocene or Sicilian PLIOCENE LIFE OF ASIA Life of Southern Asia . Evolution of the Proboscidea Conclusions as to the Age of the Siwvalie Tigi Life of Eastern Asia Pleistocene Life of India PLIOCENE LIFE oF NortTH AMERICA Relations with Eurasia American Migration of Asiatic Mateiones . Reunion with South America Evidence of Fish Faunas Geologic Succession CONTENTS XV PAGE Climatic and Physiographic Conditions. ° . ° : ~ . 342 Flora of the Pliocene . : : ‘ A - s ‘ - . 043 Flora of California :. A ; : - . 2 - : 343 Sirenians on the Pacific Coast : F “ : - = : : . 044 Flora of the Eastern States . ; ‘ - ‘ 3 ; ‘ : 2 os 1. Late Miocene or EARLY PLIOCENE . ‘ 6 3 : se aller: . 384d Alachua Clays or ‘ Archer Beds’ of Florida : : : : 4 . 346 Republican River of Kansas, Peraceras Zone. : : : : . 348 Characteristic Lower Pliocene Mammals. : 300 Horses, Rhinoceroses, ‘Tapirs, Even-toed ieumiisis: Mastaibies Gas nivores : d : : Z : ; : j : : 5 350 2. LowER PLIOCENE, LATE PHASE . ; ; ‘ ; é ‘ a oDo Snake River Formation, Neotragoceros Zone. ‘ : A : 5) obs Virgin Valley and Thousand Creek of Nevada . : ; : : . 306 Rattlesnake Formation of the John Day Valley, Oregon . : : DL 3. MippLeE PLIOCENE . ‘ , - : ‘ : . 360 Blanco Formation of Texas, Gly Piomeniee hawt : , . , . 960 4. Upper PLIOCENE OR LOWER PLEISTOCENE . . : P : ; Rees 1016) Peace Creek Formation, Florida F ; ‘ : . 366 ‘Loup River’ Formation of Nebraska, Elephas Tiapenator ane : - 368 Conclusions as to American Pliocene . F : : ‘ ; A . 93869 Causes of Pliocene Extinction . 5 is ; : . < : . 369 CHAPTER VI. THE PLEISTOCENE SEVENTH FAUNAL PHASE . ‘ . 3dBt4 Similar Divisions of the See cei ‘Phase i in ie Sue a Ola Worlds 5 BE! Time Divisions of the Quaternary. “ . “ : ; : . 375 Glacial Period in the Alpine Region . : : : : : : - hd Alternate Migration Theory . : : : : : : : Aer fis) Faunal, Glacial, and Culture Stages. ° : : ° ° sate The Eolithie Stage : ‘ : A 3 A A é é - oo2 Duration of the Pleistocene : 5 s é c 0 : . 3885 Geologic Deposits : : : : : : ° . ° . . 386 I. PLeIstocENE LIFE OF EuROPE- . ; : 5 - é a 4 . 386 Flora and Climate : : : ; . 386 Four Faunas, Secular Noviteand Bae Southward Maraciens 5 : . 388 Rhinoceroses A : : : : 3 : : . 390 1. Tue First or Earty Phuverodient FAUNA : : * A : ~ vou Geologic Proofs of the First Glacial Advance. : ° : : soe Flora of the Norfolk Interglacial : : : : . ° : . 393 Mammals of the Norfolk Interglacial . : : ° : ° : . 393 Lower Pleistocene of France : : A : < : . 395 Characteristic Lower Pleistocene Manan ; : - : “ Parson Elephants : é : : : : . . ° . : . 897 Rhinoceroses . ‘ ; ¢ 4 - A : : : - - 099 Human Culture Stages. Eolithic Flints . : . . . . . 399 2. THE Seconp or Mip-PLEISTOCENE FAUNA . : 3 : - a 399 Flora of the Interglacial Periods : : . : . . . - 401 Xvl CONTENTS First Faunal Sub-Zone ; . . ° ° Eolithic Stage. Heidelberg Man : . . ° Paleolithic Stage. The Chellean ° ° . . Second Faunal Sub-Zone . S F - : : Hlora, |; 5 ; : s : A e Characteristic Mataiale ; s “ C Horses of the II and III Faunal Tones A z A Life of the Mediterranean Islands : : - A Human Culture Stage. Mousterian . : 3 5 3. Tue Tuirp or Upper PLEISTOCENE FAUNA A 4 Pleistocene and Recent Habitat Zones 4 , 5 Tundra Fauna and Flora = ; 5 6 5 Steppe Fauna. Elevation. : : ° . Forest Fauna . : : F 3 : 5 : Migration ; . ° ° : Mammals of the Third iar aal Fotis ; : ‘ a Mammoths . ; F , b . A é Rhinoceroses . : c . ; Reindeer or Caribou ; ‘ : ; : ; Carnivores : : P s F : : , Herbivores. a A Geographic Distribution of ie Third Swaine : ~ The Schweizersbild Cave ‘ : ; é Kesslerloch Cave . : : : : i . Voklinshofen . : F ; 6 A ; : Human Culture Stages : : : : “ 5 Solutrian : : , < A é : 5 Magdalenian . : : : 2 : : : 4. Tue Fourtu, Post-PLeEIsTOCENE, OR MopERN FAUNA Jt III. 1. EARLY AND Mrp-PLEISTOCENE MAMMALS OF THE PLAINS . PLEISTOCENE LIFE OF NorTH AFRICA Climate : : : 5 3 : Sources of African plats : : ‘ : 3 : PLEISTOCENE LiFE oF NorTH AMERICA . : 5 Introduction : : : : Geologic Divisions of the nierioan Ouier : Faunal Divisions of the American Quaternary . 0 Succession of Elephants or Mammoths Physiographic and Climatic Changes . Elevation. Subsidence. Reélevation . Glacial and Interglacial Stages Climate of the Great Mountain Basin Migrations of the Sangamon Flora in Canada Migrations of Mammals Migrations of Birds Insects . Relative Age of the Equus and Megalonyx Faunas Early Phases of the Equus Zone . PAGE 402 403 404 405 407 407 408 409 410 412 414 415 415 417 419 419 419 421 429 422 424 495 425 425 426 427 427 427 428 429 430 430 434 .. 434 435 438 440 442 442 444 447 448 449 46° din 452 455, 454 CONTENTS Hay Springs, Nebraska . 5 . : ° ; Rock Creek, Texas . : ~ : ; : Silver Lake of the Oregon Been - ‘ - Late Phases of the Equus Zone A Early and Late Pleistocene Life of Kansas 2, Mip-PLEISTOCENE MAMMALS OF THE FORESTED REGIONS . Characteristic Mammals Aftonian Interglacial Stage . : : ° Upper Lake Lahontan Beds Port Kennedy Cave, Pennsylvania Frankstown Cave, Pennsylvania . Ashley River, South Carolina. z : : : Rancho La Brea, Southern California 2 F Washtucna Lake, Washington . . . . Afton, Indian Territory ; - F - é ‘ Potter Creek Cave, California Samwel Cave, California. : : ‘ : 5 Big Bone Lick, Kentucky . : , Characteristic Mid-Pleistocene Masumale ; 3 Mastodons < : 3 : ; : = Bison é a ‘ ‘ : 5 Mountain Atalones 5 : : : ; ; Tapirs. : : : ; ; : : n Horses . 4 F 3 : ‘ A a : Lions : : 4 : i A ; Q 3. FAUNA OF THE OviBos ZONE ; , : : 5 Conard Fissure of Arkansas : 5 : 5 : Canadian Deposits 5 é : 5 The Alaskan Fauna . ‘ ; Characteristic Mammals of the Third or Onhes Zone Distribution of Musk Oxen . ; ‘ : Sirenians or Sea-Cows ANTIQUITY OF MAN IN NorTH AMERICA . Man and the Mastodon , : . Man and Megalonyx . . : : Human Implements and Brine Manes : F Human Remains in Cave Deposits : Skeletal Remains attributed to Early Man CausES OF PLEISTOCENE EXTINCTION . P a ut 0 de Sn ye ae oi " v8 ‘ VAM py 7 ‘ 9.7, weg | Ni ‘ A t-f Panta le oaks) id by .h Padre r q pt aS ‘ ‘ ee Pn Fhe bi. a ut 4 it THE HARRIS LECTURES i DELIVERED AT NORTHWESTERN UNIVERSITY, DECEMBER, 1908 a det ay CHAPTER I— INTRODUCTION HISTORY OF PALAONTOLOGY — ENVIRONMENT— PAST AND PRESENT GEOGRAPHIC DISTRIBUTION OF MAMMALS I. PHILOSOPHY OF THE STRUCTURE OF MAMMALS Rise of Paleontology PALMHONTOLOGY is the zodlogy of the past. As a science it arose dur- ing the latter part of the eighteenth century in various parts of Europe with the first comparisons of the extinct with existing forms of life. Among the mammals such comparisons were instituted by Buffon and others; Cuvier subsequently formulated these into a complete system of study, and was thus the founder of vertebrate paleontology; he was also the pioneer in the art of restoration of the extinct forms of mammalian life and the conditions under which they lived. Cuvier in his famous Discours' observed that naturalists recoiled from the difficulties which faced them because of the imperfections of fossils. “Even if we should meet with the whole skeleton,’ he remarked, ‘we should have great difficulty in applying to it characteristics for the most part derived from the hair, color, and other marks which disappear before incrustation. It is uncommonly rare to find a fossil skeleton at all perfect; the bones are isolated, confusedly intermingled, most frequently broken, and reduced to fragments; this is all which our geologic layers furnish us, and is the sole resource of the natural- ist. . . . Frightened at these difficulties, the majority of observers have passed lightly over the fossil bones of quadrupeds, classed them very vaguely after super- ficial resemblances, or have not even hazarded the giving of a name to them, so that this part of fossil history, the most important and instructive of all, is of all others the least cultivated.”’ “T do not pretend by this remark,” continues Cuvier, “‘ to detract from the obser- vations of Camper or of Pallas, of Blumenbach, Scemmering, Merk, Faujas, Rosen- miller, Home, and others; but their assembled labors which have been very use- ful to me and which I have cited elsewhere are only partial.” [Footnote to French Edition, p. 47.] Among these pioneers of mammalian palzeontology in Europe to whom Cuvier refers were the vertebrate zodlogists and comparative anatomists 1 Baron Georges Léopold Chrétien Frédéric Dagobert Cuvier, 1769-1832, Discours sur les Révolutions de la Surface du Globe; et sur les changemens qu’elles ont produits dans le régne animal. 4to. Paris, 1826. B 1 2 THE AGE OF MAMMALS Peter Simon Pallas, Pieter Camper, and Johann Friedrich Blumenbach. Pallas (1747-1811) in his great journey (1768-1774) through Siberia dis- covered the vast deposits of extinct mammoths and rhinoceroses. Cam- per (1722-1789) contrasted (1777) the Pleistocene and recent species of elephants; Cuvier (1799) published ‘his memoir on the living and fossil elephants; and Blumenbach (1752-1840) separated (1803) the mammoth from the existing species of elephants as Hlephas primigenius. In 1792 Kerr distinguished the American mastodon as Elephas americanus. In 1799 Thomas Jefferson (1748-1826) described the giant American Pleis- tocene sloth Megalonyx.' ; The ancient life of the Atlantic border of North America was also becoming known through the pioneer work of Richard Harlan (1796—- 1843), Jeffries Wyman (1814-1874), and Joseph Leidy (1823-1891). The master works of Joseph Leidy began with the first fruits of western explora- tion in 1847, and extended through a series of grand memoirs, culminating in 1874. Leidy adhered strictly to Cuvier’s exact descriptive methods, and while he was at heart an evolutionist and recognized clearly the genetic relationships of the horses and other groups, he never indulged in speculation. — Cuvier’s Law of Correlation. — As a means of escaping the difficulties * caused by the imperfections of fossils, Cuvier formulated and announced his famous ‘law of correlation.’ He reposed in this law a buoyant confidence which subsequent experience has shown to have been largely misplaced. He replied to the critics of the new science of palzeontology, who deplored the imperfect nature of fossils, that the comparative anatomist does not require the entire animal, because certain laws of invariable association enable him to predict from a single part the structure of other parts. Thus, he observed, we are establishing supposititious laws which become almost as certain as the laws of reasoning, so that now any one who sees the track of a cleft foot may conclude that the animal which left it is ruminant; and this assertion is as sure as any other in physics or morality. This footmark alone gives to the observer both the formation of the teeth, the shape of the jaws, the structure of the vertebre, and the form of all the bones of the legs, thighs, shoulders, and even the frame of the animal which has passed. It is a more certain mark than all those of Zadig.* None of the numerous and genuine scientific discoveries of the great Frenchman brought him such immediate prestige as did this famous law. In reference to it Balzac said at the time that Cuvier ‘rebuilt like Cad- mus cities, from a tooth”; yet, although in part defended by Huxley,’ there is more error than truth in this law as Cuvier conceived it, for there ! Jefferson, Thomas, A Memoir on the Discovery of Certain Bones of a Quadruped of the Clawed Kind in the Western Parts of Virginia. Trans. Amer. Philos. Soc., Vol. 1V, 1799, pp. 246-260. * The above paragraph is a literal translation from Cuvier’s Discours. See full title, p. 1. 3’ Huxley, On the Method of Paleontology. Ann. Nat. Hist., Vol. XVIII, 1856. Scien- tific Memoirs, 1898, Vol. I, pp. 436-439. INTRODUCTION 3 never is, as he believed, any ‘invariable association’ between the various parts of mammals. This is because each part is adapted to the particular service which it has to perform for the animal as a whole, service which may be rendered in many different environments and on many different kinds of food. While the feet and limbs are becoming fitted to moving in the water, or on land, in trees or in flight through the air, the teeth at the same time may become fitted to one of many different kinds of food, to shrubs, grasses, bark, insects, or to other animals. Thus, while serving the whole, different parts of animals evolve separately and independently, and there have arisen consequently an almost unlimited number of com- binations of foot, limb, skull, and tooth structure.'| The simple reason why a law conceived by a special creationist is invalid is that while all parts of an animal conspire to make the animal as a whole adaptive, there is no fixed correlation either in the form of the parts or in the speed with which they evolve. It is consequently impossible for the paleontologist to predict the entire structure of an unknown animal from one of its parts only, unless the part happens to belong to a type already very familiar. For example, if we found the fossil claw bone of the cat we would know that it belonged to a cat and would be able to restore the cat; but if we found a claw bear- ing only a general likeness to that of the cat it would be very unsafe to restore the cat. There are herbivorous quadrupeds (fam. Chalicotheriid) in which the claws remotely resemble those of the giant ground sloths and anteaters; it happened that one of these very claws (of the genus Macro- theritwm) was brought to Cuvier, and full of confidence in his law, but en- tirely deceived by the resemblance of the claw to that of one of the exist- ing scaly anteaters (the pangolins of Africa and India), he termed the animal Pangolin gigantesque. Had he restored the animal according to his own ‘law of correlation,’ he would have pictured a giant anteater of a structure as wide as the poles from what we now know to be the actual form of the quadruped, Macrotherium, which in body, limbs, and teeth is a true herbivore remotely related to the odd-toed quadrupeds known as titanotheres. Again, in direct opposition to Cuvier’s law we find that certain Ameri- can Eocene monkeys (Notharctus), in which the limbs are fitted to tree- living, or arboreal, habits, exhibit grinding teeth very similar to those of the ground-living Eocene horses (Orohippus), in which the limbs, on the contrary, are distinctly of the running, or cursorial, type. Because of their teeth these monkeys were at first thought to be hoofed animals. Thus teeth do not give us certain indications of the form of the hoofs, nor does the form of the hoof give certain indications of the form of the teeth. Evolutionary law of correlation. — Yet despite this independent evolu- tion of parts, every part does conspire to make the animal as a whole adap- 1 See the Law of Adaptive Radiation, p. 22. 4 THE AGE OF MAMMALS tive, so that there is always a true adaptive correlation, although not of invariable association of certain kinds of organs, as Cuvier conceived it. The law of correlation of tooth and foot structure may, therefore, be restated as follows: — The feet, which are correlated chiefly with the limb and body structure,and the teeth, which are correlated chiefly with the skull and neck structure, diverge and evolve independently in adapta- tion to securing food and to-eating food under different condi- tions of life and in different environments. Each part evolves directly to perform its own mechanical functions and purposes, yet in such a manner that each subserves all the other parts.' Systematic Paleontology After the splendid osteological investigations of Cuvier had revealed a new mammalian world of wonderful richness, his successors were bent upon multiplying the diversity of this extinct creation, that is, adding new species and genera, rather than on closely studying the osteology of the fossil forms or adding new working principles to the science. In France De Blainville was the one great generalizer up to the time of Gaudry. Thus both in France and America facts accumulated more rapidly than principles. Cuvier’s chief contributions were to the Upper Eocene mam- mals, to a few Miocene forms, and to many Pieistocene forms. His suc- cessor, Henri Marie Ducrotay de Blainville (1778-1850), in his Ostéo- graphie des Mammiferes? (1839-1864) added to the knowledge of the Basal and Lower Eocene fauna of France. Croizet and Jobert * described (1828) the mammals of Perrier and Malbattu, Upper Pliocene. In the middle of the century Paul Gervais (1816-1879) published his Zoologie et Paléontologie Francaises. In 1851 Edouard Lartet (1801-1870) published his Notice sur la Colline de Sansan.2 Sansan is a rich Middle Miocene deposit discovered by Lartet in 1834, explored for many years, and finally monographed by Henri Filhol (1843-1907) in 1891.° ‘Cf. pp. 192, 193, of Osborn, The Rise of the Mammalia in North America. Amer. Jour. Sci., Nov. and Dec., 1893. * Ducrotay de Blainville, Ostéographie ou Description Iconographique Comparée du Squelette et du Systéme Dentaire des Mammiféres Récents et Fossiles pour Servir de Base 4A la Zoologie et 4 la Géologie. Paris, 1839-1864. * Croizet et Jobert, Recherches sur les Ossemens fossiles du Département du Puy-de- Dome. Paris, 1828. * Gervais, Zoologie et Paléontologie Frane¢aises. Nouvelles Recherches sur les Animaux Vertébrés dont on Trouve les Ossements Enfouis dans le Sol de la France et sur leur Compa- raison avec Hspéces Propres aux Autres Régions du Globe. Paris, 1859. 5 Lartet, Notice sur la Colline de Sansan, suivie d’une Récapitulation des Diverses Es- péces d’Animaux Vertébrés Fossiles Trouvés soit a Sansan, soit dans d’Autres Gisements du Terrain Tertiaire Miocéne dans le Bassin Sous-Pyrénéen. Auch, 1851. ® Filhol, Etude sur les Mammiféres Fossiles de Sansan. Ann. Sc. Geol: XO Art ale Paris, 1891. INTRODUCTION 5 The still richer Lower Oligocene and Upper Eocene mammals of the phos- phorites near Quercy, discovered in 1865 and noticed by various authors, were monographed by Filhol in 1877.' The important Lower Oligocene mammals of Ronzon, discovered by Auguste Aymard, first reported in 1856, were fully and ably monographed by Filhol in 1881. The Upper Oligocene of the center of France (l’Allier, Puy-de-Déme, Haute-Loire), successively described by Charles Depéret, Antoine Jacques Louis Jourdan (1788-1848), Gervais (1851), Nicolas Auguste Pomel (1853), was also finally monographed by Filhol in 1880. It remained for Victor Lemoine (1837-1897) to describe the Basal Eocene mammalian fauna from Cernay near Rheims, discovered in 1873, and continuously explored up to the present time. In the meantime in Germany the works of Georg August Goldfuss (1782-1848), Georg Friedrich von Jager (1785-1866), and Christoph Gott- fried Giebel (1820-1881, Fauna der Vorwelt, 1846, 1847) were followed by the more exhaustive publications of Johann Jakob Kaup (1803-1873), which covered the Upper Miocene mammals of the Mainz Basin (Eppels- heim near Worms). The gifted Christian Erich Hermann von Meyer (1801-1869) also described Hipparion and other mammals from Eppels- heim (1832). To Johann Andreas Wagner (1797-1861) we owe our first knowledge of the Upper Miocene fauna (1848-1857) of Pikermi, a won- derfully rich deposit which was finally monographed (1862) by Albert Gaudry (1827-1908). The Middle Miocene mammals of Wiirttemberg were described (1870-1885) by Friedrich August Quenstedt (1809-1889) and Osear Friedrich van Fraas (1824-1897). The work of William Buckland (1784-1856) and John Phillipps (1800- 1874) on the sparse Tertiary formations of Great Britain was followed by that of Richard Owen (1804-1892), which was finally summarized in his “A History of British Fossil Mammals and Birds” (1846), and ‘‘Con- tributions to the History of British Fossil Mammals” (1848), treating especially of the Upper Eocene of the Isle of Wight. Darwin’s Influence A review of the two classic works? of Darwin (Charles Robert, 1809- 1882), of 1839 and 1859, proves that he was the founder of modern palz- ontology. He applied to the living world the earth-forming principles of Hutton which had been grandly developed and expressed by Charles Lyell. The ideas of the descent of mammals and other applications of this law of similarity between the past and present history 1 Filhol, Recherches sur les Phosphorites du Quercy. Paris, 1877. ? Narrative of the Surveying Voyages of His Majesty’s Ships Adventure and Beagle between the years 1826 and 1836, Describing their Examination of the Southern Shores of South America and the Beagle’s Cireumnavigation of the Globe, published in 1839. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, published in 1859. 6 THE AGE OF MAMMALS of the earth, or uniformitarianism, had been struggling for expres- sion in the writings of the French evolutionists Lamarck (Jean Baptiste Pierre Antoine de Monet de, 1744-1829) and Etienne Geoffroy St. Hilaire (1772-1844), as well as in the classifications of another great Frenchman, De Blainville. These ideas found in Darwin their first true interpreta- tion, because the geological succession, the rise of mammals, their migra- tions, their extinctions, were all connected with the great central idea of divergent evolution from primordial forms. The impulse which Darwin gave to mammalian paleontology was immediate and unbounded, finding expression especially in the writings of Thomas Henry Huxley (1825-1895) in England, of Jean Albert Gaudry (1827-1908) in France, of Edward Drinker Cope (1840-1897) and Othniel Charles Marsh (1831-1899) in America. The first fine exposition of the new spirit of the period as applied to extinct Mammalia is Gaudry’s Animaux Fossiles et Géologie de lV Attique (1862), based on the Upper Miocene fauna of Pikermi near Athens. This work, to which we shall make many references, is full of genius. Espe- cially noteworthy is Gaudry’s discovery that mammals in their descent or phylogeny follow not one but many contemporaneous and _ parallel lines. In other words, Gaudry first enunciated the polyphyletic law as applied to mammals, but singularly his subsequent writings were not con- sistent with this law. The remarkable memoirs of Vladimir Onufrievich Kowalevsky (1842- 1883), published in 1873, are monuments of exact observation of the details of evolutionary change in the skull, teeth, and feet, and of the apprecia- tion of Darwinism. In the most important of these memoirs, entitled Versuch einer Natiirlichen Classification der Fossilen Hufthiere (1873), we find a model union of detailed inductive study with theory and working hypothesis. These works swept aside the dry traditional fossil lore which had been accumulating in France and Germany. They breathed the new spirit of recognition of the struggle for existence, of adaptation and de- scent. — Huxley’s most vital contribution was his development of the method of paleontology, or the modes of examining and testing facts, of synthesis and analysis. These may now be studied in his collected memoirs.' His principles of analysis are complete except in his failure to realize the wonderful operation of the law of analogy in the repeated creation of similar forms from dissimilar ancestors. All these writers attacked the problem of descent, and published pre- liminary phylogenies of such animals as the horse, rhinoceros, and ele- phant, which time has proved to be of only general value and not at all comparable to the exact descent series which were being established dur- ing the same period by invertebrate paleontologists, beginning with the 1 Scientific Memoirs of Thomas Henry Huxley, 4 vols, London, 1898-1903. INTRODUCTION a memoirs of Wilhelm Heinrich Waagen in 1869. Phyletic or ancestral gaps began to be filled in a general way, however, especially through re- markable discoveries in North America by Leidy, Cope, and Marsh; and the ensuing phylogenies, or ‘trees,’ of animal descent gave enormous pres- tige to paleontology, as affording the most convincing proofs of evolution. Primitive and progressive stages. —It was early (1870-1873) observed by Huxley, Cope, and others that Cuvier’s broad belief in a universal law of perfection was erroneous, and they began to perceive the difference between persistent primitive types (Huxley) and progressive or advancing types. Darwin himself had anticipated that primitive or stem forms of the existing modernized or specialized kinds of animals would be discovered. The analytic steps by which from existing knowl- edge the stem form might be reconstructed before its discovery, were first fully and clearly described by Huxley in 1880," namely, by separating all the specialized, or modern, characters of mammals from all the primitive, or original and simple characters, and by putting together the latter to compose an ancestral or stem form of mammal. Thus, more or less inde- pendently, Huxley, Kowalevsky, and Cope had ventured to picture what the ancestor of the hoofed mammals, or ungulates, would be like when discovered, namely, an animal whose chief characters would be grinding teeth with simple, rounded cusps, and feet with five separate and com- plete digits. This prophecy and restoration at first seemed to have been entirely realized and fulfilled in the discovery in northern Wyoming, in 1873, of a generalized hoofed mammal, to which Cope gave the name Phenacodus, although this mammal has since proved not to be directly ancestral to any form, but rather to stand for a type. The reconstruction of primitive ancestral forms was so much more facile and enjoyable than the arduous labor of exploration and research that it naturally went to extremes. Here we are reminded of a critical saying of the late Professor von Gudden, the distinguished neurologist of Munich: “Hin Steinchen der Wahrheit hat mehr Werth als ein grosser Schwindelbau.”” In paleontology the great ‘Schwindelbau,” literally “the false structure,” is the phyletic tree, which adorns the end of many good as well as many superficial papers. Recently, because of their ex- tremely brief existence, these phylogenies have fallen somewhat into dis- favor, yet the present reaction against these trees does not seem to be altogether wise, for we must remember that they are among the working hypotheses of this science, which serve to express most clearly the author’s meaning. Precise and philosophical research. — The first twenty years after the publication of Darwin’s “Origin” will always remain a golden era in the 1 Huxley, On the Application of the Laws of Evolution to the Arrangement of the Ver- tebrata and more Particularly of the Mammalia. Proc. Zodl. Soc., London, 1880, pp. 649-662; Scientific Memoirs, Vol. IV, pp. 457-472. 8 THE AGE OF MAMMALS history of mammalian paleontology, including the labors of those men- tioned above as well as of the great Swiss paleontologist, Ludwig Riiti- meyer (1825-1895). It was under the inspiration of the ‘““Odontographie”’ ' of Riitimeyer that Kowalevsky completed and published in 1873 his four remarkable memoirs upon the hoofed mammals. He wrote these four hundred and fifty quarto pages in three languages not his own, in French upon Anchitherium and the ancestors of the horses, in English on the Hyopotamide, in German upon other types of even-toed mammals, namely, Gelocus, Anthracotherium, and Entelodon,’ including the first attempt at an arrangement of these great groups of mammals on the basis of the descent theory. It is to the everlasting renown of the veteran Riitimeyer and of Kowalevsky, unfortunately so soon deceased, that while their main inductions as to the descent of the mammals and even as to the structure of certain parts of mammals, such as the teeth, have suffered by the fullness of American discoveries, their methods of thought and still more their thorough methods of research have not been displaced. Kowalevsky’s theory of the pedigree of the horses, like that of Huxley, was not the right one; Riitimeyer believed that the grinding teeth of hoofed mammals sprang from lophodont or crested forms, which also has been disproved. It is, nevertheless, the right system of thought which is most essential to prog- ress; and better in the end wrong results which have been reached by tight methods than right results reached haphazard by vicious methods. If a student to-day asks, ‘‘ how shall I study paleontology,’’ we can do no better than to direct him to the Versuch einer Natiirlichen Classification der Fossilen Hufthiere of Kowalevsky, out of date in some of its facts, thoroughly modern in its method of approach to ancient nature. This work is a model union of the detailed study of form and function with theory and the working hypothesis. It regards the fossil not as a petri- fied skeleton, but as having belonged to a moving and feeding animal; every joint and facet has a meaning, each cusp a certain significance. Ris- ing to the philosophy of the matter, it brings the mechanical perfection and adaptiveness of different types into relation with environment, with changes of herbage, with the introduction of grasses. In this survey of competition it speculates upon the causes of the rise, spread, and extinc- tion of each animal group. In other words the fossil quadrupeds are treated biologically — so far as possible in the obscurity of the past. From such models and from our own experience we learn to feel free to abandon outworn traditions in the use of the tools of science, such as mere methods of description and classification, and to conserve a reasonable priority in nomenclature only. 1 Riitimeyer, L., Beitrag zur Kenntniss der fossilen Pferde und zu einer vergleichenden Odontographie der Hufthiere im Allgemeinen. Verh. naturf. Ges. Basel, Vol. III, no. 4, 1863. ? Readers desiring to ascertain the zodlogical relations of these and other mammals mentioned in the text should consult the index and appendix. INTRODUCTION 9 New discoveries continually produce new conditions; there is nothing more obstructive than reverence for old ideas and systems which have outlived their usefulness. In observation the old motto seems to have been de minimis non curat lex, to the effect that one can afford to pass over the minute; at the present time we cannot be too exact in the ob- servation of the minute. The vertebrate palzontologist must follow the precise methods long ago introduced by Waagen (1869) among the in- vertebrates. Every rudiment of a cusp on a tooth, or facet, or articulating surface on a bone has its value, not as a sign-post on which to hang a new species, but as suggestive of the dawn of some new character, or the instru- ment of some function or relationship; the old bird’s-eye methods of comparison, which found no difference between the grinding teeth of a rhinoceros and of a lophiodon, are of no service when we are called upon to distinguish between many lines of ancient mammals crowding in among the ancestors of existing mammals. Such methods of precise observa- tion we owe largely to the influence of Riitimeyer and Kowalevsky. Influence of American Discovery The first mammalian remains from the Badlands of the Great Plains of the West, east of the Rocky Mountains, consisted of fragments of the lower jaw of the enormous quadruped, later called Titanotheriwm, which was described by Dr. Hiram A. Prout of St. Louis in the American Journal of Science in 1846. We now know that this specimen was of Lower Oli- gocene Age. ‘Travelers connected with the American Fur Company brought other specimens East in 1846 and 1847. In 1849 Dr. David Dale Owen and Dr. John Evans explored the ‘‘ Mauvaises terres,”’ and brought back collections which were first described in Owen’s Geological Report of 1852. This attracted a great deal of attention, and led to the prolonged explorations of Ferdinand Vandeveer Hayden (1829-1887) and Fielding Bradford Meek (1817-1876) between 1853 and 1866 of the whole region of Nebraska and Dakota. The collections of mammalian remains, prac- tically all of which were new to science, fell into the able hands of Dr. Joseph Leidy of Philadelphia. In 1852 he published his first volume, entitled “The Ancient Fauna of Nebraska,’ ! and in 1869 appeared his great work “The Extinct Mammalian Fauna of Dakota and Nebraska,” ” which closed with a synopsis of all fossil mammalian remains of North America known at that time. This monumental work laid the broad foundations of modern study and must still be considered one of the great- est single contributions to the mammalian paleontology of North America. 1 Leidy, The Ancient Fauna of Nebraska, or a Description of Remains of Extinct Mam- malia and Chelonia. Smithson. Contrib. to Knowl., Vol. VI, 1852. *Leidy, J., The Extinct Mammalian Fauna of Dakota and Nebraska, including an Account of some Allied Forms from other Localities, together with a Symopsis of the Mam- malian Remains of North America. Philadelphia, 1869. 10 THE AGE OF MAMMALS Subsequent research has shown that, considering the great difficulties under which they labored, Hayden and Leidy formed a surprisingly accurate conception of the geologic or time succession of mammalian forms in Oligo- cene, Miocene, and Pliocene times. Hayden’s explorations of 1869-1870 in the interior of the Rocky Mountain region led to the discovery of the Bridger deposits of Middle Eocene Age, the rich extinct mammalian life of which was monographed by Leidy in 1873. The complete geologic succession of the vast ancient life of the Amer- ican continent was destined to demonstrate the evolution law. The brief narrative of this succession, as known to-day, forms one of the chief sub- jects of the present volume. Between 1871 and 1873 Marsh and Cope took up the labors of Leidy in the exploration of the Rocky Mountain ba- sins, rich in fossil life. The first ten years of their work not only modified our ideas of the descent of the mammals, but brought together data for a number of important generalizations: for Marsh’s demonstration ! that the size of the brain was an important factor in survival, that most small- and smooth-brained mammals early became extinct; for Cope’s proof that the hoofed animals sprang from types with simple, five-toed feet, rest- ing largely upon the sole, and with conic cusps on the grinding teeth. Finally between 1879 and 1883 came Cope’s demonstration that the grinding teeth of most of the mammals had passed through a triangular form in the early Eocene period, in which three tubercles, or a tritubercular struc- ture, is apparent. Primitive and progressive forms of teeth. — This dis- covery by Cope?’ of primitive and widespread trituberculy in the molar or grinding teeth was a great step forward. ‘Dl. We find in the previous descriptive works or odontog- _ Fic. 1.— Primi- raphies of Cuvier and of Owen not even a suspicion of tive stage in tooth A Bi otic 3 F development. Typ- the existence of a common or primitive type of grinding ical tritubercular, tooth from which the highly specialized ‘‘cheek teeth”’ of upper molar of the a : mesonychid creo- the different mammals have evolved. At the present time dont, Triisodon of we may compare the molars of the clawed and the hoofed the Basal Eocene, e Puerco Formation, Mammals with each other because they sprang from a After Osborn, 1907. common tritubercular type, just as we compare the hand or foot of man, of the horse, the cat, because we know they sprang from a common five-fingered type. Nearly all kinds of mammals, hoofed quadrupeds, monkeys, carnivores, insectivores, rodents, marsupials, are found building up their grinding teeth on the basis of this primitive tritubercular ancestral form.* We thus have a key to the com- 1 Marsh, O. C., Dinocerata. A Monograph of an Extinct Order of Gigantic Mammals. U.S. Geol. Surv., Vol. X, Washington, 1884, p. 58 fol.; see also Marsh, ’74 and ’85 in Bibliography. 2 Cope, E. D., On the Trituberculate Type of Molar Tooth in the Mammalia. Pal. Bull. no. 37, Proc. Amer. Philos. Soc., Vol. X XI, Dec. 7, 1883, pp. 324-326. % See Osborn, H. F., Evolution of Mammalian Molar Teeth, 8vo. New York, 1907. INTRODUCTION +} parison of the molar teeth of nearly all mammals, and similar names can be given to the cusps in the upper and lower molar teeth respectively. This tritubercular molar owed its survival to three features: (1) the original advantage of its triangular form as expressed in the term “trigo- nodont”’ proposed by Riitimeyer; (2) the possibility of free addition of Fig. 2.— Types of superior molar or grinding teeth. A. Bunodont, all conic, Hyra- cotherium. B. Selenodont, all crescentic, Protoceras. C. Lophodont, all crested, Rhinoceros. D. Buno-selenodont, conic-crescentic, . Palewosyops. E. WLopho-bunodont, crested-conic, Tapirus. F. Lopho-selenodont, crested-crescentic, Anchitherium. new cusps as worked out in detail by Cope, Osborn, Scott, Wortman, Schlosser, and others; and (3) the wonderful independent modeling of these cusps either singly or in pairs into different forms, some remaining rounded, or bunoid, others becoming elongate, crested, or lophoid, others becoming crescentic or selenoid, as shown in the accompanying figures (Fig. 2). Taking the Greek derivatives Bovvés (hillock), Addos (crest), ceAnvy (moon, 7.e. crescent), and joining them with the word déots (tooth), we have very simple names for the various types of teeth in which all the tubercles passed through the same form. These teeth may be either buno- dont, lophodont, or selenodont. There is a marvelous, independent, adaptive evolution of each cusp; one cusp may remain rounded while its neighbors become crescentic, and we thus find compound patterns, which may be given the somewhat cacophonous terms “bunoselenodont,” or in the case of the conic-crested form, ‘‘bunolophodont.”’ - Fic. 3.—Skull of the rat, showing Diprotodonty, or the enlargement of a extreme diprotodonty of the upper pair of cutting teeth, is an adaptation which 204 lower incisor teeth. After Mat- ; F aye thew, 1905. arises frequently and independently in in- sectivores, rodents, monkeys, tillodonts, primitive edentates, and other orders. Sometimes it is the middle pair of incisor teeth, sometimes the second pair which is enlarged, while the surrounding teeth are reduced. 13 THE AGE OF MAMMALS The enlarged teeth are often so similar as to be very misleading in regard to relationship or affinity. As regards the elongation of the teeth the parallel with that of the feet is very close indeed, for we distinguish the following kinds of teeth: BRACHYODONT, primitive short-crowned teeth, with simple roots and simple cusps, and usually with simple conic, crescentic, or crested cusps, as of the pig, deer, and mastodon. Hypsopont, elongate grinding teeth, as of the ox, horse, and elephant. Just as the power of an herbivorous animal to move long distances or to take wide excursions in search of food or to move rapidly in escaping its enemies is brought about through changes in the number of digits, and in the form and proportions of the feet, so the power of an animal to live a long period of time and to assimilate the harder kinds of food is increased through changes of form and propor- tion in the teeth. The hypso- dont horse attains over thirty years of age; the hypsodont elephant lives about a hundred years. Elongate teeth may be far more highly perfected me- chanically and have more complicated crowns, consist- ing of three different dental tissues of three degrees of density, namely, enamel, den- Fic. 4.— Tooth proportions, or brachyodonty and tine. and cement. thus afford- hypsodonty. B. Brachyodont, short-toothed, Masto- . Y : é don american us. A. Hypsodont, long-toothed, Hlephas Ing three degrees of resistance, rerio usehyodont, short toothed, Arch and always presenting @ Tough Equus caballus. or uneven grinding surface. The passage from _— short- crowned to long-crowned teeth also marks the passage from browsing forms, living on softer kinds of food, to the grazing forms, living on the harder kinds of food, as well as from more short-lived animals to more long-lived animals. Here again we see that the elongation of the teeth like the elongation of the feet is eminently adaptive. For example, where physiographic changes reduce the softer herbage and increase the harder grasses, and separate the favorable feeding grounds as well as the drinking pools, the change of proportion is principally in the direction of elongation of the feet, the teeth, and the skull respectively, or dolichopody (feet), hypsodonty (teeth), and dolichocephaly (skull). INTRODUCTION 13 Primitive and progressive foot structure. —It is surprising how little attention was given to the feet of mammals between the time of Cuvier and that of Gaudry, Kowalevsky, Huxley, and Cope. Cuvier himself had assembled a lot of wholly unrelated animals as ‘‘ Les Pachydermes”’ because of the common possession of a thick skin; this was virtually a new desig- nation for the assemblage termed ‘Multungula’ by Storr (1780). In this unnatural assemblage consorted the thick-skinned rhinoceroses, hippo- potami, and other quadrupeds. De Blainville (1816) founded the modern classification of the ungulates by observing the number of digits in the feet and separating certain of the Herbivora into two classes, “a doigts pairs” and ‘“‘a doigts impairs,” or with an even and an odd number of toes respectively. This suggested to Owen (1847) the separation of the Artio- dactyla (dptvos, even in number, dd«tvdos, finger) from the Perissodactyla (zepiooos, odd in number, ddxrvaAos, finger), including the sharp separation between hippopotami with their even toes and rhinoceroses with their odd number, into two distinct orders. Thus attention was concentrated upon the numerical changes in the evolution of the feet, and Huxley, Kowalevsky, and Cope more or less independently reasoned that hoofed animals with one, two, three, and four toes must have sprung from more primitive forms with five toes. The number of digits, therefore, became an important means of distinguishing the adaptive stages of evolution in many differ- ent lines of mammals, as follows: PENTADACTYL, primitive five-toed mammals such as Phenacodus. TETRADACTYL, Mammals with four digits such as Hippopotamus and dog. TRIDACTYL, Mammals with three digits such as Rhinoceros and early stages in the evolution of the horse. DipactTyL, mammals with two digits such as the deer and cattle. MonopactyL, mammals with one digit, typified by the horse. It was also observed that the simple number of digits does not tell the whole story because of differences of proportion related to the amount of service which each digit renders to the animal. Thus in an early stage in the evolution of the horse there are three full-sized digits and a short ad- ditional digit in process of degeneration. The former rest on the ground and are functional or in active service; the latter is suspended at the side of the foot, has lost contact with the ground, and is becoming vestigial. This gave rise to a distinction between functional tridactylism, in which all three toes are of service, and numerical tridactylism, as in Hipparion, where the middle toe is doing all the work, and the two side toes are dan- gling above the ground. De Blainville’s (1816) and Owen’s (1847) sepa- ration of the even- and odd-toed hoofed animals led to the observation that the main weight of the animal either passes through the central digit, as in the rhinoceros and horse (Perissodactyla) or between the two cen- 14 THE AGE OF MAMMALS tral digits (Artiodactyla). This difference was expressed in other words by Marsh! by the terms Mesaxonia and Paraxonia respectively. The pose or angle of the foot as a whole, including the wrist and ankle joints (carpals and tarsals), the intermediate bones (metacarpals and metatarsals), and the terminal joints (phalanges and ungues), began to Fie. 5.— Evolution from pentadactyl to monodactyl condition as illustrated in the foot of the horse (above) ; comparison with the human hand (below). A. Pentadactyl, hypothetical ancestral stage. B. Tetradactyl, Protorohippus stage. C. Tetradactyl-tridactyl, Epihippus stage (three toes resting on the ground, one raised slightly above). D. Tridactyl, Mesohippus stage. HE. Monodactyl, Equus stage. attract increasing attention. In primitive forms it was seen that the entire hand and foot is stretched along the ground, as in the bear and in the foot of man, while in the opposite extreme the foot rests on the nail or on the very extremity of the last phalanx, as in the hoof of the horse. Thus in the gradus, or step, a series of important intermediate stages are observed, as follows: PLANTIGRADISM, where the entire sole of the hand or foot rests upon the ground, as in the hind foot of the bear. SEMI-PLANTIGRADISM, where half the sole rests upon the ground, as in the fore foot of the bear. 1 Marsh, O. C., Dinocerata. A Monograph of an Extinct Order of Gigantic Mammals. U.S. Geol. Surv., Vol. X, Washington, 1884, p. 186. INTRODUCTION 15 DicitiGRapisM, where the foot rests only on the rows of phalanges, as in the dog and cat. UNGULIGRADISM, where the foot rests only upon the end phalanx, as in the horse and the deer. RecTiGRADISM, where the foot is immobile and the entire weight rests on a large pad, as in the elephant. Reduction of digits. — This led to the further generalization that all primitive types of mammals were pentadactyl or five-fingered and planti- grade, or with the sole of the hand and foot resting upon the ground. From this it was an easy step to perceive that the raising of the wrist and ankle joints from the ground in the passage from plantigradism to digitigradism also tended to raise the shorter digits, namely, the thumb, or first digit in the hand, and the big toe, or first digit in the foot, from the ground, to render them useless in progression and to initiate their degeneration or retrogression. It is, in fact, in this stage, where the inside digits of both hand and foot are in process of disappearance, that we discover most hoofed mammals of the early geological periods. The loss of one digit after another occurs under what is known as the law of digital reduction. Thus the passage from five to four, to three, to two, to a single digit is a gradual process, not the work of a century or centuries, but of vast periods of time. Perfection of joints and facets. — Another and more intricate law in the science of foot evolution concerns the changes in the articulations, or facets, between the bones of the wrist and ankle and the bones of the metapodium on which they rest. Kowalevsky first directed close attention to the fact that all these facets and articulations are altered while the wrist or ankle is in process of be- coming raised from the ground, while the digits are being reduced, and while the weight is being concentrated more and more on the central digits and taken from the lateral digits. This shifting of the joints or facets was found by Kowalevsky,' Cope,’ Riitimeyer,* and Osborn‘ to produce an interlocking system, so that the bones are placed above each other like rows of bricks with ‘‘struck”’ or alternating joints, and this alternation of the joints with the closed surfaces is brought about by more rapid growth ci some parts of the foot bones than of other parts, producing at every stage a perfect mechanism, calculated to resist the enormous strains which come upon the foot, especially in the rapid movements of swift running 1 Kowalevsky, Monographie der Gattung Anthracotherium Cuv. und Versuch einer natirlichen Classification der fossilen Hufthiere. Paliéontographica, Vol. XXII, 1873. ? Cope, The Vertebrata of the Tertiary Formations of the West. Rept. U. S. Geol. Surv. Terr., Vol. III, Washington, 1884; also, The Perissodactyla, Amer. Natural., Vol. X XI, 1887. 3 Riitimeyer, L., Uber einige Beziehungen zwischen den Siiugethierstiimmen Alter und Neuer Welt. Abh. Schweiz paliont. Ges., Vol. XV, pp. 1-151, Ziirich, 1888. * Osborn, The Evolution of the Ungulate Foot, Pt. IV of The Mammalia of the Uinta Formation by Scott and Osborn. Trans. Amer. Philos. Soc., n.s. Vol. XVI, Aug. 20, 1889, pp. 531-569. 16 THE AGE OF MAMMALS types of hoofed animals. Another device of nature in the same direction is the development of tongue-and-groove joints out of rounded or universal joints, bringing about precision of movement and preventing lateral dislo- cation. All these steps seem to have a distinct survival value, that is, to affect mammals in the struggle for existence. Thus Kowalevsky was the first to point out that certain quadrupeds with less perfected foot mechanisms were gradually replaced by others with more perfected foot mechanisms. A lowly organized or primitive hoofed mammal is found to be full of mechanical defects when its feet are applied to the severe tests of rapid progression; it is condylarthrous, ‘ball and socket’ or loose-jointed, it is plantigrade, or clumsy, or slow-gaited, it is pentadactyl, or with five fingers Fic. 6.— Foot proportions among rhinoceroses. A. Brachypody, short-footed, T7’eleoceras fossiger. B. Mesatipody, medium-footed, A phelops malacorhinus. C. Mesatipody, medium- footed, Rhinoceros unicornis. D. Dolichopody, long-footed, Colodon longipes. still resting on the ground, it is often taxeopod, or with imperfectly alter- nating joints in the different rows of bones in the hands and feet. As a rule also it is short-footed, or brachypod. In short, all the ancestral adaptations to ambulatory, tree, and rock- climbing purposes must be abandoned and new adaptations acquired. Like the teeth, the feet evolve partly through changes of proportion as well as through reduction, or loss of useless parts. Thus the passage from slow-walking, or ambulatory types, to swift-moving, or cursorial types, is almost invariably marked by elongation of the primitively short hand and foot. This gives us another series of stages, as follows: Mesatipeopy, mean, or intermediate foot forms, as of the tapir. Bracuypopy, extremely short feet, as of the elephant. Douicuopopy, elongate foot forms, as of the horse. Altogether the changes of foot structure in the hoofed animals con- stitute a fascinating study and are easily comprehended. Through these changes the prehensile and locomotor powers of the limbs of animals are INTRODUCTION 17 profoundly affected and diversified, and numbers of types are evolved, as, - for example: AMBULATORY, slow-moving, mostly primitive. CURSORIAL, swift-moving, secondary. SALTATORIAL, swift-moving, leaping, secondary. FossoriAL, slow-moving, digging, and burrowing. NATATORIAL, amphibious, aquatic, swimming. ARBOREAL, slow-moving, tree-climbing. GLISSANT, gliding, as in the ‘flying’ squirrel. VOLANT, flying, as in the bat. Primitive and progressive skull structure. — Changes in tooth proportion and foot proportion may or may not be accompanied by changes of propor- Fic. 7.—Skull proportions among Titanotheres. A. Brachycephaly, short-headed, Paleosyops major. B. Mesaticephaly, medium-headed, Manteoceras manteoceras. C. Doli- chocephaly, long-headed, Dolichorhinus cornutus. tion in the skull. Here again we find that there are three general stages in the anatomy of the skull of mammals,’ and that the descriptive terms are the same as those which were introduced long ago (1842) in the anatomy of the human skull by the great Swedish anthropologist, Anders Adolf Retzius (1796-1860), namely: MESATICEPHALY, an intermediate or partly elongated condition, charac- teristic of many intermediate and primitive forms, such as the tapir. 1 See Osborn, H. F., Dolichocephaly and Brachycephaly in the Lower Mammals. Bull. Amer. Mus. Nat. Hist., Vol. XVI, Art. VII, Feb. 3, 1902, pp. 77-89. c 18 ; THE AGE OF MAMMALS BRACHYCEPHALY, a short, broad-headed condition of the skull, charac- teristic of some progressive forms. DoLicHOCcEPHALY, an elongate condition of the skull, especially of the anterior or facial portion in front of the eyes, as in the horse (Hquus) and in the moose (Alces). The rationale of these changes of proportion is very different in dif- ferent skulls, so that we never can assume that long-headedness is due to any single cause. In the horse long-headedness is a very ancient char- acter; even the earliest known four-toed horses have quite elongate, or at least mesaticephalic, skulls. The progressive elongation of the skull in horses is apparently for two purposes: first, to facilitate reaching the ground with the row of incisor or cropping teeth; second, and no less important, to allow space in front of the eye sockets for the great rows of elongate, or hypsodont, grinding teeth, the marvelous dental battery of the horse. We might assume from these facts that long-headedness is correlated with long teeth, but the giant pigs (elotheres) have still longer and narrower skulls than the horse, yet all the teeth are brachyodont, or short-crowned. Again, the elephant has extremely elongate or hypsodont molar teeth, yet it possesses also the shortest, or most brachycephalic, skull known among the Mammalia. Thus all kinds of combinations and changes of proportion occur in the evolution of mammals. The correlation is not that of certain fixed types of structure, but it is a correlation of perfect adaptations to different de- mands brought about by the changes in habitat. Il. MAMMALS AND THEIR ENVIRONMENT The fitness of mammals to their environment takes us back to another line of thought in the history of paleontology, in which we see that the idea of the evolution of the environment, as revealed by the study of fossils and the earth itself, grew step by step with the idea of the evolution of mammalian life. It has become clear that there are two ways in which mammals experience a change of environment: either through their own migrations, or through “‘the migration of the environment itself,’ as Van den Broeck has expressed it, in the successive historic changes of certain parts of the earth in course of time. Thus if we imagine a family of mam- mals residing continuously in the region now known as South Dakota, the early humid environment has migrated to quite a different part of the American continent, and an entirely new, arid environment has come in. Sometimes mammals and their environment migrate together. This was certainly the case during the Glacial Period, when physiographic condi- tions, faunas, and floras all moved southward together before the advance of the ice sheet, and again moved northward together as the ice retreated. INTRODUCTION 19 Origin and Migration The crude idea of centers of origin and dispersal, or migration of differ- ent kinds of animals, is a very ancient one. Even Moses’ treatise on Noah’s ark and the spread of its passengers was probably not the first attempt at a theory of geographic origin and distribution of the beasts and birds, because this theory had its antecedents in the traditions of Mesopotamia. There is no question that these myths strongly influenced the early at- tempts at scientific explanation. For the approaches to modern views one should read successively the writings of the great French naturalists Buffon and Cuvier. We find in Buffon,! who wrote in the middle of the eighteenth century, many instances of anticipation of what are commonly regarded as modern views. Buffon’s laws of animal distribution were regarded by Cuvier as veri- table discoveries. They set forth some of the fundamental principles of geographic distribution, contrasting successively all the continents (Eu- rope and Asia, or Hurasia, Africa, North America, and Australia), and enumerating especially the kinds of animals which each possessed and in which each was lacking. In comparing the new and old worlds, Buffon observed that the quadrupeds of North America were of smaller size than those of Eurasia and Africa, since the largest North American animals were inferior to the elephants, rhinoceroses, and hippopotami of Africa. His second remark is more important: it is, that the North American animals form a parallel or collateral animal kingdom which more or less duplicates that of the Old World with some important exceptions, and this remark may be construed as an anticipation of the law of evolution of analogous groups on large continental surfaces. Every animal, he re- marked further, has its natural country or habitat, a fact which links z00logy with geography. His theory of evolution — and he certainly was an evolutionist — may be known to-day as Buffon’s law of the di- rect action of the environment upon the organism; he believed that climate or environment exerted the strongest influence in the modi- fication of animal forms.. Thus he attributed the shades of color in the skin of human races to the more or less intense action of the sun. Palzogeography, or the study of the past relations of the land and sea surfaces of the globe, also had its beginnings in Buffon’s time. In com- menting on the giant extinct fauna, the mammoths (Hlephas primigenius) and woolly rhinoceroses (Rhinoceros tichorhinus), which had been made known in northern Asia and Siberia through the explorations of Pallas, and on the former distribution of the elephants in North America, Buffon significantly pointed out that parts of the globe now submerged beneath ' Georges Louis Leclerc, Comte de Buffon, 1707-1788. Edition of Buffon’s works here referred to is the first, Histoire naturelle générale et particuliére, avec la description du cabi- net du Roi, 1749-1789, 44 vols., illustrated, including Supplements. Flourens’s Buffon, Histoire de Ses Travaux et de Ses Idées, 12mo, Paris, 1844, is based on this edition. 20 THE AGE OF MAMMALS the sea were formerly elevated and furnished land bridges or connections between the continents; he thus clearly adumbrated the idea of the migra- tions of quadrupeds and of the subsequent separation of faunas, or animal groups, by continental depressions and the submergence of old migration routes. The accompanying map, the dotted areas on which represent the land bridges which would emerge through the elevation of the continental borders to a height of two hundred fathoms, shows the reader that no | : Gabe hal L teal eh om _| Fic. 8.— Map of the world with existing outlines and 200 fathom lines (dotted areas) showing former land connections at the last period of maximum elevation. very profound or cataclysmal changes are required to connect the northern continents with each other and with the outlying masses. With the south- ern continents, South America, Africa, and Australia, it is different; an emergence of 3040 meters, or 1662 fathoms, is necessary to connect them as shown on the map on p. 77. Still more definitely Buffon placed the land separation between the old and new worlds in his ‘‘Sixth Epoch,” and in this connection clearly brought out a theory of extinction of certain species, as of the mammoths of Siberia and of North America. This problem of the interpretation of the giant fossils of the north had been one of the first to attract the attention of naturalists; Johann Georg Gmelin (1709-1755) left it as a legacy to Buf- fon, Buffon handed it down to Blumenbach, the pioneer of vertebrate paleontology in Germany. Buffon attributed (Tome V, p. 172) the dis- appearance of the great animals from the north partly to the refrigeration of the temperature, and partly to migration to the south. Nows ne powvons INTRODUCTION 21 douter quwapres avoir occupé les parties septentrionales de la Russie et de la Sibérie . . . ow Von a trouvé leurs dépouilles en grande quantité, ils n’aient ensuite gagné les terres moins septentrionales . . . en sorte qu’d mesure que les terres du Nord se refroidissoient, ces animaux cherchoient des terres plus chaudes.... (Tome V, p. 172, Supplément.) This sagacious naturalist also pointed out that these monuments of the extinct life of the earlier ages-of the world were understandable by comparison of their structure with that of living animals of related type; such comparison, he observed, demonstrates the existence in times past of species different from those actually existing but closely related (Tome V, p. 154, Minéraux). Cuvier observes that fossils, which have given birth to the theory of the earth, have also furnished it with its principal lights, the only ones which have been generally recognized down to the present period. He extends Buffon’s ideas, and gives new and beautiful theoretical illustrations of the possible effects of continental elevation and depression, which we may paraphrase with slight modifications of his own language. Let us suppose, Cuvier remarks in his Discours (Paris, 1826, pp. 64-65), that a great invasion of the sea covers with a mass of sand or other deposit the continent of Australia; it would bury the carcasses of the kangaroos, wombats, dasyures, bandicoots, flying phalangers, as well as of the duck- bills [Ornithorhynchus| and spiny anteaters [Hchidna]. It would entirely destroy these species of animals because none of them exist in any other country. Suppose, further, that the same convulsion of nature were to leave dry the numerous small straits which separate Australia from the continent of Asia; it would open the way for the entrance into Australia of the elephant, rhinoceros, buffalo, horse, camel, tiger, and all other Asiatic quadrupeds, which would come to people this continent in which they were before unknown. If, however, a naturalist studying these living ani- mals were to lay open the soil on which they moved he would find the re- . mains of the buried ancient fauna of marsupials, ete. What Australia would become were such a hypothetical invasion realized, Europe, Siberia, and a great portion of America are to-day, and it may some day be dis- covered in the examination of these countries, and even of Australia itself, that they have all experienced similar revolutions. To carry the above hypothesis still further, Cuvier concludes, after the Asiatic animals have migrated into Australia let us imagine that a second revolution destroyed Asia, the original home of these animals: the naturalist who discovered their second country would be as much embarrassed to find whence they came as we can now be to discover the origin of those animals which are found in our own countries. Despite these sagacious views, Cuvier was an exponent of the cata- clysmal rather than the uniformitarian school of transformation, that is, he believed in violent changes in past times rather than in the slow changes such as we observe to-day. Experience has proved that he was somewhat 22 THE AGE OF MAMMALS extreme in his idea of the total depopulation of the continents through great physical revolutions; we have no evidence that such sweeping changes have ever occurred, yet he was not far from the truth, and it is certain that in these specific illustrations, cited above, he clearly thought out and furnished some of the chief ideas underlying our modern work, namely, of theinvasionsof great groups of mammals through the forma- tion of new routes for migration and of wide resulting con- trasts between the existing and the extinct forms of life, or faunas in all continental areas. As regards mammalian origin and descent it is well known that Cuvier was not an evolutionist, but on the contrary a convinced believer in special creation. This belief kept him from fully anticipating the ground work of modern paleontology. He did not consider the Age of Mammals as furnishing the source of any animals now existing. He recorded his dis- covery of the mammals of the Gypse de Montmartre as a revelation of a phase of mammal life which he believed to belong early in the Age of Mam- mals (it is now known to be Upper Eocene), but he did not seek among these mammals ancestors of existing forms. Although he believed that all these older forms had become extinct, he did not appeal to new crea- tions to produce the species now existing, but maintained that such species were existing elsewhere, that is, in other parts of the world. This in- genious and interesting feature of Cuvier’s theories as to the replacement of faunas has not been understood sufficiently because, as recently pointed out by Depéret,! he has been credited generally with a theory which really arose in the imagination of some of his followers rather than his own, namely, of a succession of extinctions followed by a succession of creations. Cuvier rather believed that an extinction on one continent or in one region was followed by repopulation through migration from another region, and he illustrated his meaning very clearly in the hypothetical cases cited above of the possible invasion of the sea over the continent of Australia and subsequent repopulation from Asia. The Law of Adaptive Radiation The law of evolution even as crudely perceived by Buffon added another element of fascination to the ideas of centers of origin and of migration, namely, that of modification of mammals under new and strange con- ditions of environment. Such general modification was about as far as Buffon’s thoughts went. Those of Lamarck went farther, namely, to adaptation to new conditions of life, and with this idea is coupled his con- ception of the principle of divergence or radiation in the formation of differ- ent habits and the search for different kinds of food. 1 Depéret, L’évolution des Mammiféres tertiaires; l’importance des migrations (Eocéne). C. R. Acad. Sci., Paris, Vol. CXLI, Nov. 6, 1905, p. 702. INTRODUCTION Fis Darwin independently and at a somewhat late day discovered this essential principle as told in his Autobiography: ! “ But at that time I overlooked one problem of great importance; and it is astonishing to me, except on the principle of Columbus and his egg, how I could have overlooked it and its solution. This problem is the tendency in organic beings descended from the same stock to diverge in character as they become modified. That they have diverged greatly is obvious from the manner in which species of all kinds can be classed under genera, genera under families, families under sub- orders and so forth; and I can remember the very spot in the road, whilst in my carriage, when to my joy the solution occurred to me; and this was long after I, had come to Down. The solution, as I believe, is that the modified offspring of all dominant and increasing forms tend to become adapted to many and highly diversified places in the economy of nature.”’ The writer has termed this principle of embranchement of Lamarck, or of divergence of Darwin, the law of adaptive radiation.2. According to this law each isolated region, if large and sufficiently varied in its topog- raphy, soil, climate, and vegetation, will give rise to a diversified mam- malian fauna. From primitive central types branches will spring off in all directions with teeth and prehensile organs modified to take advan- tage of every possible opportunity of securing food and in adaptation of the body, limbs, and feet to habitats of every kind, as shown in the diagrams on page 24. The larger the region and the more diverse the conditions, the greater the variety of mammals which will result. The most primitive kinds of mammals were probably small insec- tivorous or omnivorous forms, therefore with simple, short-crowned teeth, of slow-moving, ambulatory, terrestrial, or arboreal habit, and with short feet provided with claws. In seeking food and avoiding enemies in different habitats the limbs and feet radiate in four diverse directions; they either become fossorial or adapted to digging habits, natatorial or adapted to amphibious and finally to aquatic habits, cwrsorial or adapted to swift-moving, terrestrial progression, arboreal or adapted to tree life. Tree life leads as its final stage into the parachute types of the flying squirrels and phalangers, or into the true flying types of the bats. We have not thus far found a single instance in which a mammal is known to have been transformed from an aquatic into a land type; it is always the reverse. Nor have we found an instance where the extreme fossorial or cursorial types have retrogressed into slow-moving, ambulatory, or terrestrial types. There is some evi- dence, however, of arboreal types secondarily taking up terrestrial habits, as in the case of many of the terrestrial and cursorial marsupial mammals of Australia, which are believed to have evolved from specialized arboreal 'The Life and Letters of Charles Darwin, including an Autobiographical Chapter. Edited by his son Francis Darwin. London, 1888, Vol. I, pp. 68-69. * Osborn, The Law of Adaptive Radiation. Amer. Natural., Vol. XXXIV, 1902, pp. 353- 363. 24 THE AGE OF MAMMALS LIMBS AND FEET VOLANT FOSSORIAL as ARBOREAL Short-limbed, vine AMBULATORY pentadactyl, unguicu- or late Stem TERRESTRIAL NATATORIAL CURSORIAL Amphibious Digitigrade Aquatic Unguligrade TEETH 1s Grass OMNIVOROUS | Herb HERBIVOROUS Fee Fish Fruit CARNIVOROUS [ish ; Root Carrion : MYRMECOPHAGOUS Ae es Dentition reduced Stem INSECTLVOROUS forms. Similarly, Matthew' has suggested that most placental mammals bear evidence of descent from primitive arboreal ancestors. Similarly, in the case of the teeth, insectivorous and omnivorous types appear to be more central and ancient than either the exclusively carnivo- rous or herbivorous types. Thus the extremes of carnivorous adaptation, as in the case of the cats, of omnivorous adaptation, as in the case of the bears, of herbivorous adaptation, as in the case of the horses, or myrme- cophagous adaptation, as in the case of the anteaters, are all secondary. ‘Matthew, W. D., The Arboreal Ancestry of the Mammalia. Amer. Natural., Vol. XX XVIII, nos. 445-446, Nov.—Dee., 1904. INTRODUCTION 25 It is obvious that a mammal may hunt for its herbivorous diet in sev- eral different habitats, in the water, on land, on trees, beneath the surface of the earth, and since the limbs are the means of locomotion in these habitats a mammal may be herbivorous and natatorial, like the manatee (Manatus) and dugong (Halicore), herbivorous and arboreal, like the tree sloths (Bradypodidz), herbivorous and cursorial, like the horses. This makes it perfectly clear why there is no fixed correlation between the structure of the teeth and that of the limbs, and is another proof of our inability to predict the form of one part of an animal from our knowledge of another part. The prolonged operation of the adaptive radiation of mammals from primitive and generalized forms into specialized and adaptive forms has in the vast periods of geologic time (see p. 63) evolved or created the existing Orders of Mammals. The Orders of Mammals A brief review of the chief kinds of mammals living and extinct is needed before we can take a survey of their history; otherwise the reader will be lost in details without being able to comprehend general kinds and relations. A full conspectus of the classification of the principal types of mammals living and extinct will be found in the Appendix of this volume, to which the student or reader may make rapid reference through the index. With reference to adaptive radiation, each order of mammals should be thought of as having a typical mode of life from which its various mem- bers diverge in various degrees, sometimes so far as to take up an entirely different mode of life. The typical life is usually the original, ancestral or primitive life which characterized the order when it first diverged from other orders; as a rule it is the typical mode of life which gives or has given the dominant or profound anatomical characters to the teeth and skeleton. For example, the rodents were originally herbivorous, gnawing animals, and this is still typical of most rodents, but certain rodents have departed so far from their ancestral habits as to become not only aquatic but fish-eating. Thus there is a clear distinction between the primary, typical, original, fundamental adaptation of an order, and the secondary or acquired adaptations which many of its members may enter upon and thus imitate the typical adaptation of another order. The grand divisions and subdivisions of the Chass MamMatta of Linnzeus are as follows: 1 For a review of the evolutionary relationships of the principal groups of mammals, see Gregory, W. K., The Orders of Mammals. Bull. Amer. Mus. Nat. Hist., Vol. X XVII, 1909. 26 THE AGE OF MAMMALS A. EGG-LAYING MAMMALS. Very Primitive, Reptile-like, or Transitional, Reproducing their Young from Deposited Eggs. I. PROTOTHERIA. 1. PROTODONTA. Very small and primitive, North American mam- mals (?) of the early Age of Reptiles. 2. MONOTREMATA. Of Australia, New Guinea, and Tasmania, highly specialized Prototheria. No Pre-Pleistocene forms certainly known. Duckbill Platypus (Ornithorhynchus) and Spiny Anteater (Echidna). B. VIVIPAROUS MAMMALS. Of Higher Grade, Bringing Forth their Young Alive. Il. MARSUPIALIA, DIDELPHIA, or METATHERIA. Pouched Mammals, or Marsupials, typically carrying the young in a pouch. Placental structure rudimentary or primitive. Extinct and living families of Australia, South America, and (opossums, etc.) Holarctica. 1. TrriconoponvTa. Polyprotodont carnivorous marsupials (?) of the Age of Reptiles. 2. MARSUPIALIA PROPER. a. Multituberculata. Diprotodont, herbivorous marsupials of the Age of Reptiles and early Age of Mammals. b. Polyprotodontia. Polyprotodont, carnivorous, and omnivorous Mar- supials of the Age of Mammals. Opossums, dasyures, etc. c. Diprotodontia. Diprotodont, herbivorous marsupials of the Age of Mammals. Phalangers, kangaroos, etc. III. PLACENTALIA, MONODELPHIA, or EUTHERIA. Mammals nour- ished before birth by a typical placenta. Young never carried in a pouch. A. UNGUICULATA. Clawed Mammals, adapted to terrestrial, fossorial, arboreal, aquatic, cursorial, and volant life. Including all the actual and theoretical primitive forms of mammals, as well as many modern- ized or highly specialized forms. 1. PANTOTHERIA (TRITUBERCULATA). Small primitive insectivores of the Age of Reptiles (Jurassic), generally with numerous cheek teeth. 2. INSECTIVORA. Modern insectivores, such as moles, shrews, hedge- hogs, and tenrecs. 3. TILLODONTIA. Lower to Middle Eocene, tillotheres or tillodonts, herbivorous or phytophagous mammals, in some respects similar to rodents. 4. DERMOPTERA. Represented only by the “flying lemur,” Galeo- pithecus, of the Oriental region. 5. CHIROPTERA. The bats, including the fruit bats, vampires, insect- eating bats, ete. 10. 1k INTRODUCTION 27 CARNIVORA. a. Creodonta, or Primitive Carnivora (Eocene). Surviving to the Lower Oligocene. , b. Fissipedia, of Middle Eocene to recent times, including the civets, hyzenas, dogs, raccoons, bears. ce. Pinnipedia. Seals, walruses. Known from Miocene to recent times. RODENTIA. Squirrels, beavers, mice, porcupines, etc. Lower Eocene to recent times. T ZNIODONTA, or GANODONTA. Probably ancestral or related to the edentates. Primitive, with enamel on the teeth. Basal to Middle Eocene, North America only. EDENTATA, or XENARTHRA. True South American edentates (also North America, Eocene and Recent), without enamel on the teeth, Eocene to Recent. Sloths, armadillos, glyptodonts, ground sloths, ant-bears, ete. PHOLIDOTA. Scaly Anteaters, or Pangolins (Manis), of India and Africa. Oligocene to recent times. TUBULIDENTATA. Aardvarks (Orycteropus). Oligocene to recent times. Africa (recent species), and Europe (extinct species only). B. PRIMATES, primarily adapted to arboreal and ambulatory life, fingers terminating in “nails,” rarely in claws. Frugivorous, phytophagous, and omnivorous. The primitive forms are distantly allied to the Unguiculata-Insectivora. PRIMATES, including a. Lemuroidea, lemurs, galagos, “aye-aye,” tarsier, etc., and extinct lemuroids. Eocene to recent times. b. Anthropoidea, monkeys and apes, including South American mar- mosets, Old World monkeys, baboons, apes, and anthropoid apes, also man. Miocene to recent times. C. UNGULATA, or Hoorep Mammats, herbivorous, primarily ambula- 15. 14. 15. tory and cursorial, secondarily aquatic and rarely arboreal. Originally derived from members of the Unguiculata. 1. ARCTOGHAN HOOFED MAMMALS i.e. of North America, Asia, Europe, and Africa. A. Probably of Holarctie Origin. CONDYLARTHRA. Archaic, primitive, light-limbed, hoofed mammals, surviving to the Lower Eocene. AMBLYPODA. Archaic, heavy-limbed quadrupeds, surviving to the Upper Eocene. . ARTIODACTYLA. Even-toed, hoofed mammals, including pigs, hippopotami, camels, tragulines, deer, giraffes, antelopes, sheep, oxen, and many extinct forms. Lower Eocene to recent times. 28 THE AGE OF MAMMALS 16. PERISSODACTYLA. Odd-toed, hoofed mammals, Lower Eocene to recent times, including tapirs, horses, rhinoceroses, and the extinct paleotheres, titanotheres, lophiodouts, ete. 17. ANCYLOPODA. Closely related to the Perissodactyla. Middle Eocene to Upper Miocene times, with hoofs secondarily modified into claws, ~ partly for digging. B. Probably of African Origin. 18. PROBOSCIDEA. Mastodons and elephants. Upper Eocene to recent times. 19. BARYTHERIA. Including only one (discovered) large, peculiar herbi- vore, of the Lower Oligocene of North Africa. 20. SIRENIA. Sea-cows or manatees, and dugongs. A highly modified aquatic offshoot of the hoofed mammals. Upper Eocene to recent times. 21. HYRACOIDEA. The dassies and conies of Africa and Syria, small rock and tree-living hoofed animals. Upper Eocene to recent times. 22. EMBRITHOPODA. Including the “ Arsinoitheres” of the Upper Eo- cene and Oligocene of northern Africa only. 2, NEOGHAN HOOFED MAMMALS OR NOTOUNGULATA i.e. of South America. 23. HOMALODOTHERIA. Including Homalodotherium and others. Penta- dactyl, secondarily clawed mammals. Teeth in continuous series. Eocene to Miocene, South America. 24. ToxopDontTia. Including the protypotheres, typotheres, nesodonts, and toxodonts. Eocene to Pleistocene, South America. Molars with flattened outer wall, more or less rhinocerotoid. Incisors often enlarged. 25. ASTRAPOTHERIA. Including the rhinoceros-like astrapotheres. Chiefly Miocene, South America. Upper canines forming elongate tusks. Limbs pillar-like. 26. LITOPTERNA. Including light-limbed, three-toed, and virtually one- toed forms, some resembling three-toed horses. Eocene to Pleistocene, South America. bo 7. PYROTHERIA. Including ‘diprotodont’ forms with crested masto- don-like molar teeth. Eocene, South America. Limbs pillar-hke. CETACEA, or whales, aquatic mammals probably derived from the Unguiculate Division. 28. ZEUGLODONTIA. Primitive Eocene whales, transitional in certain characters to primitive carnivores. 29. ODONTOCETI. Toothed whales, including the extinct squalodonts, the river and marine dolphins, the belugas and narwhals, the beaked whales, and the sperm whales. 30. MYSTACOCETI. Whalebone whales, including the right whales, the humpbacked whales, and the fin-backed whales. INTRODUCTION 29 This classification is followed in the same order in the Appendix of this volume, where the families and principal genera are also introduced. Adaptive Radiation and Geography We may now consider the relation between the adaptive radiation of the different kinds of mammals and the geography of past and present times. Adaptive radiation, continental.‘ — The law of adaptive radiation natu- rally operates on a grand scale on great continents like Africa, or a great insular continent like Australia. Through its geographic distribution and isolation there originate from common primitive forms new species, genera, families, and even orders of mammals. It is most important to grasp in imagination the ideas of adaptive radiation as applying wherever there is a large theater for the operation of this law and of a succession of radiations in the course of the Age of Mammals. Thus we shall study the proofs of primeval or archaic radiation of mammals which began during the Age of Reptiles and extended in all directions into forms resembling modern insectivores, rodents, bears, dogs, cats, monkeys, sloths, buno- dont, and selenodont hoofed mammals and lophodont hoofed mammals. Through the extinction of many of these mammalian branches or radii, through the survival of other branches, or through the invasion or entrance of branches from some distant radiation, the process begins over again. For these grand continental radiations there seems to be some ratio between the degree or extent of divergence and the physiographic diversity and extent of the geographic area in which the radiation occurs. As shown below (p. 38) this connects adaptive radiation with the science of zodgeography or geographic distribution. Thus the highly diversified land area of Arctogzea, comprising Africa, Eurasia, and North America, constituted a vast center in which twenty- one primitive and specialized orders of mammals radiated from each other. In the more restricted continent of South America four to five orders of mammals enjoyed their chief radiation. Adaptive radiation, local.? — Quite as important although not on so grand a scale is the local adaptive radiation in the same or neighboring geographic regions wherever there is found a diversity of habitat and of food supply. Good living illustrations of this local adaptive radiation are seen in the geo+ graphic distribution in Africa, previous to the extinction by man, of the “white” or square-lipped rhinoceros (Rhinoceros simus), which lives upon grasses and has long-crowned or hypsodont teeth, and the ‘‘black”’ or ‘See Osborn, Correlation between Tertiary Mammal Horizons of Europe and North America: An Introduction to the More Exact Investigation of Tertiary Zoégeography. Ann. N.Y. Acad. Sci., Vol. XIII, no. 1, July 21, 1900, pp. 49 ff. ? Osborn, 1902, op. cit. 30 THE AGE OF MAMMALS pointed-lipped rhinoceros (2. bicornis), with short-crowned or brachyodont. teeth, which browses mainly upon shrubs. The feeding ranges of these animals are not very far apart. They do not subsist upon exactly the same food, thus they do not compete. The grazing ‘white rhinoceros” is long-headed, or dolichocephalic, the browsing ‘black rhinoceros”’ is rela- tively short-headed, or mesaticephalic. The local adaptive radiation of the antelopes of Africa furnishes still more remarkable illustrations of the same kind. ' Among living forms we find long-headed and short-headed, long-footed and short-footed, long-toothed and short-toothed types, living near each other, resorting to the same water courses for drink, and thus liable to be killed in the same spot. We thus find a clue in the present to the inter- pretation of what frequently occurs among fossilized types, namely: in the same geological deposits are often mingled short-footed, or ambulatory, with long-footed, or cursorial, quadrupeds. The cursorial types subsisted upon grasses and ranged out on the plains, the ambulatory types, chiefly browsers, frequented the river borders, the thickets, and the hillsides. Among the best illustrations of this kind is the difference between the forest- living horse Hypohippus and the plains-living horse Hipparion of the Upper Miocene. (See pp. 243, 295.) Thus local adaptive radiation causes the splitting up of mammals dwelling in the same geographic regions into side branches or series which we call phyla. We may find preserved in the same geologic deposits two, three, four, or even as many as five phyla of mammals belonging to direct and collateral lines. Local adaptive radiation is, therefore, one explana- tion of the next very general principle of divergence, which may be known as the polyphyletic law. The polyphyletic law. —In these locally separated phyla, sometimes minute, sometimes conspicuous differences are developed. One of the most frequent distinctions is in adaptations to speed, 7.e., in ambulatory and cursorial types; another is in the proportions of the skull, whether brachycephalic or dolichocephalic; a third is in the proportions of the horns, if such are developed. This law is so general in Oligocene and Mio- cene times that if we discover light-limbed types we may anticipate the discovery of their more slow-moving counterparts. Horses, camels, rhinoceroses, the related titanotheres, have one after another proved to break up under this polyphyletic law into grazing and browsing types, slender and heavy types, in the same or neighboring geographic regions. It is seen at once that this polyphyly renders the study of phylogeny, or the tracing of successive lines of descent among the mammals, far more interesting and at the same time far more difficult, because the fossil re- mains of members of these different series or phyla are often intermingled and it is difficult to separate them. In other cases the nature of the geo- logic deposition affords a ready key to the separation of these phyla. For aes INTRODUCTION 31 example, sediments which we find deposited in rivers are found to contain chiefly the forest-living and slow-moving, browsing types, while deposits which were made on flood plains contain the grazing, swift-moving types. Another fact of great interest is that this separation of the quadrupeds or Herbivora naturally brought about a separation of their carnivorous enemies into powerful, short-limbed types with massive jaws, and swifter, light-limbed types, with more slender parts. Adaptation to alternations of habitat. — In the long vicissitudes of time and processions of continental changes, animals have been subjected to alternations of habitat either through their own migrations or through the migrations of the environment itself; that is, a habitat to which an animal has become adapted may be abandoned for a long’ period of time and adaptations are acquired for a second habitat. Following this again, life in the first habitat may be resumed. Dr. Louis Dollo has contributed most brilliant discussions * to this alternation of habitat theory as applied to the interpretation of the anatomy of the marsupial mammals of Australia and of several of the orders of reptiles and fishes. Although often obscure, the anatomical proofs of adaptations corresponding to alternations of habitat are recorded both in the skeleton and in the soft parts of animals. In his brilliant essay of 1880 Huxley ? suggested that the primitive forms of marsupials were all arboreal, or tree-living, an hypothesis which has been abundantly confirmed by the careful studies of Dollo' and Bensley,’ according to which we may imagine that the marsupials passed through: (1) a very primitive land-living, or terrestrial phase, in which the limbs would be normally developed; (2) an arboreal, or tree-living phase, in which some modifications of the limbs for grasping of the boughs would be acquired, as illustrated in the tree phalangers of Australia; (3) a sec- ondary land-living, or terrestrial phase, in which the arboreal adaptation of the limbs is checked and a new adaptation to swift-moving, or cursorial habits is acquired, as in the kangaroos, in which the hind limbs especially are modified for leaping and rapid progression; (4) a return to arboreal life, with further adaptations for tree-living habits in limbs which have already been extremely modified in course of the earlier phases, as in the tree-kangaroos. ; Improbable as such a theory of alternation of habitats appears at first to be, it is none the less supported by the strongest anatomical evidence in the study of the feet of the marsupials, in which the record of one adap- e 'Dollo, Louis, Les anecétres des Marsupiaux étaient-ils arboricoles? Trav. Stat. zodl. Wimereux, Tome VII, 1899, pp. 188-600, pl. XII. * Huxley, T. H., On the Application of the Laws of Evolution to the Arrangement of the Vertebrata and more Particularly of the Mammalia. Proc. Zodl. Soc., 1880, pp. 649-662; Sci. Mem., Vol. IV, pp. 457-472. * Bensley, B. Arthur, On the Evolution of the Australian Marsupialia; with remarks on the Relationships of the Marsupials in General. Trans. Linn. Soc., London (2) Vol. IX, Pt. 3, 1903, pp. 83-214. ae THE AGE OF MAMMALS tation on another is plainly written. Similar, but less extreme examples are known among the higher placental mammals of the northern hemisphere, in which the theoretical life phases are as follows: 1. A primitive ambulatory phase of a small, slow-moving animal, of insectivorous or omnivorous type, provided with claws. 2. The transformation into an herbivorous, ambulatory type pro- vided with more or less well-formed hoofs, adapted to terrestrial gait and relatively swift movements. 3. Partial adaptation of a slower gait, accompanied by the conversion of the hoofs into clumsy claws, adapted to digging or tearing down the smaller branches of trees, as in the larger sloths. This return of an ungu- late or hoofed type back to an imitation clawed type, like that of the large ground-living sloths, occurs several times independently among the typically hoofed mammals, the most extreme case being that of the chali- cotheres (Macrotherium), which were mistaken for giant sloths by Cuvier, but which really show a regression to an older habit. (See Fig. 130.) The Law of Analogous Evolution All the modes of change described above are divergent, or tending to separate animals from each other. If the surface of the earth were infi- nitely varied, and if animals had an infinite variety of means of adaptation to certain conditions, undoubtedly all families and genera of mammals would be entirely dissimilar from each other, but in comparing the habi- tats of mammals in different parts of the earth, among the diversities of condition we find similarities or repetitions of similar environments: each continent has its mountains, its hillsides, its plains, its pampas, river borders, swamps, deserts, grazing grounds, forests, its open country. Again, the modes of adaptation of the epidermis, of the teeth, feet, and limbs of mammals are also limited. The ingenuity of Nature in adapting animals to similar conditions is not infinite; the same devices are repeatedly em- ployed by her to accomplish the same adaptive ends. This repetition or duplication of habitat in different parts of the earth underlies the law of analogous evolution, because mammals in their adapta- tions to similar conditions of habitat or environment in different parts of the earth have repeatedly converged or come together in their external and more or less in their internal form, as well as in separate structures. As regards the similar molding of single organs in many independent groups of mammals, one of the first to trace this law in detail was W. B. Scott in his masterly paper of 1891.'| This process of the analogous fash- ioning of animals which may be only remotely related or not at all related to each other is known as homoplasy, parallelism, and convergence. ‘Thus ' Scott, W. B., On the Mode of Evolution in the Mammalia and on some of the Factors in the Evolution of the Mammalia. Jour. Morphol., Vol. V, 1891, no. 3, pp. 361-378, 375-402. INTRODUCTION 33 homoplasy affects not only separate organs but entire types of animals, groups of families and entire groups of orders, in a manner often extremely confusing to the seeker of real ancestral relationships. Analogy, or like- ness of function, through its power to transform unlike and unrelated mammals or unlike and unrelated parts of mammals into likeness, has per- formed such miracles that the inference of kinship or descent is often irre- sistible; yet it is now well understood that a deeper ancestral resemblance may closely relate animals which are externally dissimilar, while it may just as widely separate animals which are externally similar. Similar desert or steppe environments have fashioned the African jumping hare (Pedetes) of the Cape, the true jerboas (Dipus, Alactaga) of the steppes of Asia, and the American jumping mice (Zapus) into similar saltatorial forms, yet these are partly independent transformations. These Jumping mice (Di- podide) are paralleled by many forms: among other rodents by the Heteromyide (pocket mice), among the insectivores by the elephant shrews (macroscelids), among marsupials by the rat-kangaroos (Bettongia), etc. Thus analogous adaptation is the counterforce to divergence, and strongly tends to bring mammals together. Nevertheless two very im- portant exceptions are to be noted. First, we rarely find exactly and precisely the same means adopted in several groups of organs twice over; and second, all the externally similar forms may be found on close exam- ination to bear record of real internal and ancestral differences. Thus the marsupial mole Notoryctes closely parallels the placental mole Talpa in external appearance, but in its internal structure and dentition, in its mode of reproduction, and in its skeleton it is fundamentally different. Thus similarity of adaptation can never be mistaken by the close and logical student of anatomy for similarity of descent or of ancestry. Of these two kinds of adaptation and genetic resemblance, analogy is the woof, composed of the horizontal strands which tie animals together by their superficial resemblances, while homogeny (homology as applied to organs) is the warp, composed of the vertical, hereditary strands which connect animals with their ancestors and their successors. The grander applications of analogy to the groups of mammals were first observed by Buffon in similar adaptations of animals evolving on different continents. In earlier studies of the marsupials of Australia Geoffroy St. Hilaire, De Blainville, and Richard Owen observed the re- markable analogies between the “families”? into which these mammals are divided and the “orders” of the northern continents. Cope ' also ob- served this grand mimicry of marsupial and placental orders. More recently it has been discovered that the collective mammals of ancient South America, although of partly independent stock, in many ways mimic the collective mammals of North America in Ceenozoic times. 1 Cope, E. D., Origin of the Fittest. Essays on Evolution. Svo, New York, 1887. D 34 THE AGE OF MAMMALS Again, the archaic, or Cretaceous placentals of North America and Europe, although alike marked by extremely low organization in certain characters, in other characters more or less closely imitate the radiations o1 higher groups and give us bear-like, cat-like, dog-like, and hyzna-like forms. Connecting this principle with the laws of adaptive radiation, conti- nental and local, we find that the radiations in different areas are more or less analogous with each other; that is, we discover many analogous radii or lines of adaptation, among other radii which are entirely dissimilar. When we come to compare the early evolution of the mammals in Africa, for example, we shall find that adaptation pursued entirely different lines from those pursued in Europe, Asia, and North America; so that when the African mammals finally entered Europe, after having undergone a long independent evolution of their own, they were entirely dissimilar and foreign in appearance to any with which they competed in Europe. One of the most important advances of the past twenty years has been the clear recognition of this law of analogy and of the pitfalls which it con- stantly spread for the earlier students of mammals. It may be described as the very ‘will o’ the wisp” of evolution, always tending to lead the student of descent astray. The Law of Irreversibility of Evolution A very frequent feature of divergent adaptation is the loss of parts as explained on p. 15, or the very profound modification of parts, as in the “tree phase,” of the early life of the marsupials, in which two of the toes become syndactylous, or closely applied to each other. These lost parts are never reacquired, nor can such profound modifications of form and proportion be overcome; a specialized organ can never again become generalized, lost parts are irretrievable. It follows that while the condi- tions of life may be recurrent or reversible, the conditions of adaptive structure are not reversible. Hence the dictum of Dollo’ that evolution, while frequently reversible in conditions of environment and adaptation, is irreversible in animal structure. Each part that is lost, like a tooth or a digit, narrows down the possibility of future plastic adaptation to new conditions. Nature often resorts to other remedies to repair her losses, namely, to substitution of parts, or to change of function. Thus extreme specialization accompanied by the great enlargement of certain parts and the great reduction of other parts often places a mammal in a cul de sac of structure, where it is incapable of further modification to meet a new environment. This may become a cause of extinction. 1 Dollo, Les Lois de Evolution. Bull. Soc. Belge Géol., Paléont., Hydrol., Vol. VII, 1893, pp. 164-166. INTRODUCTION a III. GEOGRAPHIC OR SPACE DISTRIBUTION OF MAMMALS Zoégeography. — We have seen above that we owe to Buffon (p.19 ff.) and Cuvier (p. 22 ff.) the beginnings of the fascinating study of geographic distribution in past and present times. Cuvier clearly saw that the mam- mals which we find at any point on the earth to-day may not have origi- nated there but have had their homes or centers of origin at far distant points. It has since become more and more evident that only through paleontology can we connect the present distribution of mammals with their distribution in the past, and set forth a science of geographic dis- tribution, or zodgeography, which will be in harmony with both sets of facts. The importance of this more thorough study of present and past geo- graphic distribution was recognized by Alexander von Humboldt. The first exact attempt to compare the animals and plants of the present and past in a single region was that of Edward Forbes in his remarkable paper on the geological relations of the fauna and flora of the British Isles... In this paper he attempts to distinguish those animals and plants which are native to the British Isles from the immigrants, and among the latter he attempts to trace the sources, or geographic centers from which they came. Many of the principles of zodgeographic distribution were clearly un- derstood by Darwin and set forth in ‘‘The Origin of Species”’ in the year 1859, and it is noteworthy that in the same year Philip Lutley Sclater ? divided the world into six zodgeographic regions, as follows: Peak : ( Nearctic, Boreal Zone. North America ore \ Neotropical Tropical Zone South America { Palzearctic Boreal Zone Europe and Asia weno mA Indian Tropical Zone Southern Asia Ethiopian Tropical Zone Africa Australian Austral Zone Australia We observe that Sclater’s was an east and west division, or a new and old world division, based on the lines of longitude rather than of latitude. Murray’s “Geographical Distribution of Mammals,” published in 1866, at 3 served to arouse further investigation of this subject. The six great regions of Sclater were subsequently adopted in their en- tirety by Altred Russel Wallace in his great work of 1876, ‘Geographical Distribution of Animals ...’’* the first comprehensive attempt at this 1 Forbes, E., On the Connection between the Distribution of the Existing Fauna and Flora of the British Isles with the Geological Changes which have affected their Area. Mem. Geol. Surv., Vol. I, 1846. 2 Seclater, P. L., On the General Geographical Distribution of the Members of the Class Aves. Jour. Proc. Linn. Soc. (Zoél.), Vol. II, p. 130 (1857), 1859. 3 Murray, A., The Geographical Distribution of Mammals, London, 1866. 4 Wallace, A. R., Geographical Distribution of Animals, with a Study of the Relations of Living and Extinct Faunas as Elucidating the Past Changes of the Earth’s Surface, 2 vols, London, 1876. 36 THE AGE OF MAMMALS study. The fundamental suggestion of Sclater to divide the world into astern (Palzeogeea) and western (Neogzea) divisions proved, however, to be entirely inconsistent with the facts of past and present distribution. Hux- ley as early as 1868 had proposed a northerly (Arctogzea) and southerly (Notogzea) division, and it became gradually apparent! that the six great regions should be grouped into larger northern and southern ReALMs. Sclater (1874), J. A. Allen (1878), W. T. Blanford (1890), and Alfred Newton (1893), along various lines contributed to the conclusion that there are three such great primary realms based on a north and south divi- sion, namely: Arctogea, Notogwa, and Neogewa. The regions as embraced in these realms are clearly set forth in the accompanying table. REALMS REGIONS GEOGRAPHIC BOUNDARIES I. ARcTOGHA Hoiarctic Region Europe, Asia, and North America. Nearctic Region North America north of Mexico. Palearctic Region Asia, north of the Himalayas, Europe, and Africa north of the Desert of Sahara. Ethiopian Region Africa, south of the Sahara Desert. Oriental Region Asia south of the Himalayas, including Su- matra, Java, Borneo, and the Philippines. II. Norogma Australian Region Australia. Ill. Nrogama Neotropical Region South America. This division into grand zoégeographic Realms and Regions broadly, or in a general way only, conforms to the facts of distribution of mammals in past and present times, and these divisions correspond with the main events during the Age of Mammals, but are not to be understood as being separated either by sharp or continuous barriers. For example, while Neo- gea, embracing the single Neotropical Region of South America, was during the greater part of the Age of Mammals separate from the other Realms, it shows at the beginning unmistakable proof of connection both with Notogzea (Australia) and with Arctogzea (the northern hemisphere), and toward the close of this Age it shows the most positive evidence of renewed union with Arctogea through a commingling of the North and South American faunas. Reatms. — Thus it appears that while these grand Realms were the main centers of the adaptive radiation of the orders of mammals, the orders were not confined to these realms, but during periods of land connection certain members strayed into adjacent realms; that each realm, there- fore, contains a mingling of its original, or autochthonous types and its ‘The history of opinion on this subject is fully set forth in Lydekker’s invaluable work, A Geographical History of Mammals, 1896, chap. i. Additional interesting details are found in R. F. Scharff’s History of the European Fauna (1899). INTRODUCTION 37 migrant, or derived types. Thus Arctogwa, containing the broadest and most highly diversified land areas of North America, Asia, Europe, and Africa, appears as the center in which twenty-one primitive and special- ized orders of mammals radiated from each other. In the southern Realm of Neogwa, more restricted geographically, four or five orders of mammals enjoyed their chief radiation. During the larger part of the Age of Mam- mals Notogzea (Australia, New Zealand, and Tasmania), shut off by the sea from Arctogzea, witnessed the highly diversified radiation of the Mar- supials and of the declining group of Monotremes. REGIONS in the zodgeographical sense may be thought of as more restricted areas of adaptive radiation of mammals which have been isolated ARCTIC eunasianien “Andi TEMPERATE Ne AMERICA (Palaearctic) (Nearctic) Sy BS oti Scans Iriental) AFRICAN \ (Ethiopian) Oy Fic. 9.— Chief zojgeographic Realms and Regions of the world on the Sclater- Huxley system. from each other for shorter periods either by climatic barriers, as in the case of the arctic conditions of the north, or by great physical barriers, such as masses of water or desert sands. Whereas the Realms are the centers in which orders originate, Regions in general are chiefly distin- guished by the adaptive radiation of families of mammals. This, while broadly true, is not universally true, for the Ethiopian Region (Africa south of the Sahara) appears to have given birth during early Tertiary times to several orders of mammals, namely: Barytheria, Embrithopoda, Hyracoidea, Proboscidea, and perhaps the Sirenia and Cetacea. The two marine orders of mammals, last named, are also attributed to the hypothet- ical ‘Atlantis,’ or atlantic archipelago connecting Africa and South America (see J. W. Gregory, Eigenmann, and others). It must be very clearly understood, therefore, that all the modern zoogeographic divisions, Realms, Regions, sub-Regions, etc., are chiefly 38 THE AGE OF MAMMALS used for purposes of convenience, that they express the truths of geographic distribution in their grander outlines but not in their details. In the shifting geographic and physiographic scenes of the enormously protracted Age of Mammals the lines of division are now sharpened by continental depression and separation, by isolation and insulation, and again blended by continental elevation or by the formation or renewal of migration routes, and by the opportunities, of which the mammals are prone to take immediate advantage, to extend their geographic range by migration. ‘ Thus we shall see in past times the Nearctic and Palearctic now blend into the Holarctic, and again separate more widely than at present. Again, we shall see the Ethiopian, Holarctic, and Neotropical blending far more closely than they do at present. In truth, there can be no uniform system of past and present distribution, as the present writer once fondly hoped. Every geologic Era, every Epoch, and even every Period has its own laws of distribution. Migration Routes and Barriers Checking the tendencies of mammals to migrate are inconspicuous barriers of many kinds in the living world and in animals themselves, as well as the more obvious and conspicuous physiographic and climatic barriers. Mountain chains, broad rivers, stretches of sea, of desert, or of forest, which freely facilitate the migration of some kinds of mammals and form absolute checks to the migration of other kinds, present barriers no more formidable than those indirectly brought about by certain degrees of moisture and of heat or cold. Thus ‘temperature zones”’ form barriers wherever they control the periods of reproduction.’ Moisture may infest a country with insect pests, such as flies, ticks, and mosquitoes, which form as absolute a boundary to migration as a broad mass of water. Animals which are so specialized as to be restricted or confined to certain habitats may be said to impose their own barriers upon themselves. | Most barriers are ultimately traceable to changes in the greater and lesser land masses and their connections, caused by the elevation or sub- sidence of various parts of the earth. These changes both:make and destroy land routes, and cause a series of changes in all physical conditions of climate, moisture or desiccation, of temperature, or heat and cold. The succession of faunas during the Miocene and Pliocene periods in Europe is positive proof of a succession of environments. In this connection it is highly interesting to compare the stable con- tinents of North America and Africa, which show relatively slight fluctua- tions of land and sea level during the Age of Mammals, with the highly unstable continent of Europe. During a considerable part of the Age of 1 Merriam, C. H., The Geographical Distribution of Life in North America with Special Reference to the Mammalia. Proc. Biol. Soc. Washington, Vol. VII, April 13, 1892. INTRODUCTION 39 Mammals Europe is like a peninsula budding off from the western side of Asia or at times almost like an archipelago, so largely does the sea trans- gress its northern and southern borders. Its varying coastlines, its insular conditions, its archipelagic surfaces are to be followed in imagination in connection with the evolution of its mammalian fauna. Nevertheless the main trend of evolution and extinction in unstable Europe coincides with that in relatively stable North America. IV. Gerouoagic or TIME DISTRIBUTION OF MAMMALS Time divisions. — A host of questions turn upon the geologic, or time distribution of mammals, which is to be studied hand in hand with their geographic, or space distribution, as above described. The precise solu- tion of all problems of origin and dispersal, or travel and migration of the different kinds of mammals, concluding finally with the most absorbing question of the center of origin and dispersal of the human race, turns upon the question of geologic time. At present, from astronomical reckoning, we may all ascertain the time and readily fit all that is occurring in different parts of the world into the days, weeks, and months. In the past, however, in the geologic time divisions! which are known as Sracems (Htages), Pertops, and Epocus, we directly invert our present order of procedure, because we must first discover what is occurring in the different parts of the world, and from these occurrences we must deduce, estimate, and establish geologic time. If the question is asked when did the Age of Reptiles close and the Age of Mammals begin, in France, in the Rocky Mountains, or in South Amer- ica, the answer is sought not through the rocks, but through the fossils which they contain, or through a process of observation and reasoning which is known technically as paleontological correlation. When we com- pare all the fossil mammals which are known in the dawn of the Eocene in Europe, in North America, and South America, we are able to establish a homotaxis or general similitude in the life of these widely separated regions, and a synchronism, or general similitude in the time of these different re- gions. An exact synchronism is practically impossible of attainment, but approximate synchronism, or-time correlation, is by no means beyond our reach, although often a vastly long and difficult undertaking. The very title of this volume, ‘‘The Age of Mammals,’ "implies the 1Comptes Rendus de la VIII® Session, en France, Congrés Géologique International, Paris, 1900 (1901). This International Geological Congress ruled the following use of terms: 1. Hras=Palseozoic, Mesozoic, Czenozoic. (Csenozoic = Tertiary + Quaternary.) 2. Periods as Cambrian, Silurian, Cretaceous, ete. 3. Epochs=Eo ..., Meso ..., Neo..., as Eodevonian, Mesodevonian, Neode- vonian, ete. 4, Ages = Etages = (Ages or Stages), as Astian, Bartonian, ete. 5. Phases=Life Zones, such as ‘‘zone A Cardiola,” ete. 40 THE AGE OF MAMMALS question of time, and it is 6ne of our chief objects in this review of the his- tory of the fossil mammals of the Old and New Worlds to use this history as a means of closely establishing similar divisions of past time in these two widely separated geographic regions. Employing the suggestive terms of Louis Agassiz, the whole life history of the earth may be divided into Ages of Invertebrates, of Fishes, of Rep- tiles, of Mammals; the latter Age comes as the last episode before the final Age of Man. The Age of Mammals is technically known as the Cenozoic Era (Age of Recent Life), a term which is partly equivalent to but has generally replaced the older term Tertiary, which signifies the third period in the history of life. The Cenozoic is subdivided into two Periods and six Epochs, as follows: Epochs (Hoxrocens, (from oAss, entire, caves, recent), or recent time, characterized ‘= | by the world-wide destruction and elimination of mammals through a the agency of man. = \ PLEISTOCENE (from zAeioros, most, Kavos, recent), a life period in which = the majority of the recent forms of mammals appear and in which 3 there occurs the last glacial period and a great natural extinction of © earlier forms in all parts of the world. & PLIOCENE (from 7Aeiwv, more, Kavos, recent), a vast modernization of 2 the mammals in which all the existing orders and families are known, S as well as many of the existing genera, but few or no existing species. & & | Miocene (from petwv, less, Katvos, recent), an earlier stage of moderniza- O 5 tion, in which lived many mammals closely similar to existing forms. a OLIGOCENE (from 6ACyos, little, kaos, recent), characterized by the ap- EB pearance of many existing types of mammals and the gradual dis- £ appearance of many of the older types. & | Eocene (from 4s, dawn, xavvés, recent), characterized by the first ap- pearance of many of the ancestors of the modernized mammals and the gradual disappearance of many of the archaic types characteristic of the Age of Reptiles. These grand time divisions of the Czenozoic are the work of the nine- teenth century, and the incessant trend of discovery is to multiply time divisions and make them more minute. The work of the twentieth cen- tury is precise correlation. The ardent studies of the great French natural- ists Lamarck, Alexandre Brongniart (1770-1847), Cuvier, and Deshayes in the early part of the nineteenth century, the golden age of palzeontol- ogy in France, were accompanied by a growing realization of the vast stretches of geologic time as witnessed in the vast changes which have taken place in the animal life of the globe and in the enormous thickness of some of the sedimentary rocks which had been deposited even during this later or Tertiary Period. It became absolutely necessary to make divi- sions of the Tertiary; the threefold division was in the first instance due INTRODUCTION 41 to the monumental researches of Gérard Paul Deshayes (1795-1875) on the succession of the shells in the Paris Basin; he perceived that as we pass from the older and lower to the higher and more recent geological levels there is an increasing percentage of living types or species. To the threefold division discovered by Deshayes, Charles Lyell in 1833 applied the names Hocene, Miocene, and Pliocene. In 1854 Heinrich Ernst Beyrich (1815-1896) perceived that in many parts of Europe a fourth grand divi- sion existed between Eocene and Miocene times, for which he proposed the term Oligocene. Another step in this naming of the periods or sys- témes was in 1839 when Lyell’ proposed the term “ Pleistocene’’ for the period succeeding the Pliocene and preceding the Recent or Holocene. Students of fossil shells also took the leadership in further dividing the Age of Mammals into time periods by demonstrating that the epochs can be subdivided into stages, or étages. Thus the French invertebrate paleontologist, Alcide Dessalines d’Orbigny (1802-1857), divided the Eocene of France into a lower stage, or Suessonian, named from the deposits chiefly north of Paris, and an upper stage, or Parisian, named from the deposits around Paris. Successive proposals of D’Orbigny, Duméril, Mayer-Eymar, Suess, Depéret have finally led (1889) to the subdivision of all the Czeno- zoic periods into a large number of Staces which receive their names from the geographical localities in which they are most typically represented in various parts of France, Belgium, Italy, and Sicily. It is now recognized that each of these stages represents a long period of time. These stages and their approximate parallels in North America are exhibited in the accom- panying table. Preliminary Correlation EvROPE ASIA NortH AMERICA Upper SICILIAN Siwaliks ‘Loup River’ PLIOcENE Middle ASTIAN Siwaliks Blanco Lower PLAISANCIAN Siwaliks {Thousand Creek | Rattlesnake and Republican River ‘Loup Fork’ Upper PONTIAN Manchhar Madison Valley Clarendon Deep River MI0cENE Middle VINDOBONIAN Manchhar | Pawnee Buttes Maseall Arikaree Lower BURDIGALIAN — | ‘Upper Harrison’ Upper Rosebud 1 Charles Lyell, Antiquity of Man, 1839, p. 6. 42 Upper OxicocENE } Middle Lower f Upper Middle EocENE Lower {Basal CRETACEOUS UPPERMOST THE AGE OF MAMMALS AFRICA AQUITANIAN STAMPIAN SANNOISIAN Fayim LuDIAN Fayim BaARTONIAN LUTETIAN Uprer YPRESIAN LOWER YPRESIAN SPARNACIAN (Upper Landenian of Bel- gium) UprpER THANETIAN (=Cer- naysian) (Lower Landenian of Bel- gium) Lower THANETIAN DANIAN = MAESTRICHTIAN (Terrestrial) (Marine) Importance of Time Correlation Harrison (Lower) John Day White River (Upper) White River (Middle) Brule Clays White River(Base) Cypress Hills Pipestone Creek Chadron Uinta (Upper and | Middle) Washakie (Upper) Uinta (Lower) {Wasa (Lower) Bridger (Upper) | Bridger (Lower) Huerfano (Upper) Bridger (Lower) Huerfano (Upper) Green River Huerfano (Lower) [vi River Wasatch (Upper) Wasatch (Lower) | Torrejon Fort Union Puerco Fort Union Hell Creek If we are eager to solve the great number and variety of most inter- esting questions still unsolved as to the source, origin, affiliation, migra- tion, and extinction of the noble races of animals which passed across the stage of the northern hemisphere, or ancient Holarctic Region, during the Cenozoic Period, we must endeavor to use very exact methods of com- INTRODUCTION 43 parison, to establish so far as possible the homotaxis or the synchronism of the geological subdivisions of the Czenozoic in the New and Old Worlds, and to agree upon the limits which shall be assigned to the Eocene, Oligo- cene, Miocene, Pliocene, and Pleistocene Epochs and their stages. It will certainly prove best that the grandly successive series of Ter- tiary horizons in France should be adopted as the chief bases of time divi- sion, partly because of their priority of description and definition, but chiefly because in France, owing to the instability of the continent above referred to, there is a remarkable alternation of fresh-water deposits con- taining remains of mammals and of marine deposits containing fossilized shells, the shells serving as time-keepers of the evolution going on in other parts of the world. Thus in France the evolution of mammals, or the vertebrate time scale, is checked off by the invertebrate time scale. As we shall see, the Lower Ceenozoic of America from the base of the Eocene to the summit of the Oligocene offers us a much more complete life story than that of France; in fact, it is an unbroken historic chapter. The same is true of our Oligocene and to a somewhat less extent of our Miocene. But the mammal-bearing series is entirely fresh-water. Only during the late Miocene and Pliocene of Florida and in the little known Oligocene of New Jersey, do we discover an alternation of marine and fresh-water con- ditions such as occurs throughout the entire Cenozoic in France. In the Pliocene our country affords only a series of vistas of what was happening, while Europe offers a more commanding view. If, therefore, France, Germany, Switzerland, and Italy furnish the ini- tial basis for time standards, comparison with America will serve to check and amplify. Thus the final basis for time divisions of the Cenozoic will be international. There is every reason for the international usage of similar terms, both as to life forms and as to time stages. In these matters patriotism and provincialism naturally should have no weight; palzon- tology knows nothing of the divisions formed by the English Channel, the Rhine, nor the Atlantic; it does not recognize the superiority of an Eng- lish system, a French, a German, or an American system, but like all its sister branches of science, in these times of absolute scientific good will, demands an international system. If approximate synchronism in the Epochs and Stages can be established, and the present volume is designed to bring together all the facts that can be assembled toward such syn- chronism, it will be very desirable to adopt uniform descriptive terms for the European and American geologic divisions. Our first object is to show how far the Epochs or Systémes of Americ: and Europe can be synchronized and similar permanent limits be placed between them; our second object is to establish Stages as convenient divisions of each, in addition to the descriptive terms Upper, Middle, Lower, and Basal, which are respectively marked off in the natural geo- logic boundaries of the two continents. Of course the synchronizing of the stages and substages throughout will present greater difficulties and 44 THE AGE OF MAMMALS may in some instances prove impossible, owing to the absolute independ- ence of the movements of the earth and of the other physical phenomena which caused these stages in the Old and New Worlds. It is obvious that the overlapping in time of these minor periods of deposition would be the rule and that exact synchronism would be largely coincidence and there- fore highly improbable; all that we can reasonably hope to establish in the near future is approximate synchronism of the stages. Ultimately the lines of time overlap may be determined. Time Value of Fossils During the Age of Mammals we should endeavor to establish absolute time in different parts of the world, like Greenwich standard time of to-day, not through measuring the thickness of the rocks but through using as our chronometers all the known forms that lived, plants, and vertebrate and invertebrate animals. The thickness of the rocks varies enormously, and is correspondingly deceptive. The fresh-water Oligocene rocks of the western plains, for example, are only 400 to 800 feet in thickness, while on the Pacific coast and in Italy marine rocks of the same age are 10 to 12,000 feet in thickness. The thickness of rocks is one of the means of estimating the total duration of the Age of Mammals, while the stages of evolution in animals and plants give us the punctuation points, as it were, or the means of keeping geologic time. It is true that during the Cano- zoic Era the plants are comparatively stationary, and so are the amphibians, fishes, and reptiles, but the mammals are in a state of continuous and in- cessant change, and what gives them especial chronometric value is that the rate of change or of evolution is the same in many parts of the world at the same time. Even during the Age of Reptiles we may take advan- tage of the remarkably constant evolution of the herbivorous multituber- culate gnawing mammals known as Plagiaulacidee, surviving members of which are found in the Basal Eocene (Fig. 28). The grooves on the sides of the large cutting teeth of Plagiaulax and the cusps, or tubercles, on the grinding teeth are successively added with the precision of clock-work, while the number of premolars is diminishing. If we suppose the rate of evolution has been about the same, we can approximately calculate the intervals of deposition.’ AGE OF REPTILES AcE oF MAMMALS : Stonesfield Purbeck Laramie Puerco Cernaysian Diminishing number of pre- MOLARS Ace eek dnt ot ? 4-3 2 2-1 1 Increasing grooves on pre- MOAT S Oat tae hh ve Nek ? 7-9 11-14 12-15 14 Increasing number of molar tubercles: outer; imner . ? 4:2 6:4 6:4 OG 1 See Osborn, H. F., The Rise of the Mammalia in North America. Proc. Amer. Ass. Ad. Sci., 1894, pp. 188-227; and Amer. Jour. Sci., Nov. and Dec., 1898. INTRODUCTION 45 Similarly the slow stages in the attainment of perfection in the grind- ing teeth of the Eocene horses are of great value as time-keepers; for example, in the molars of Hohippus and Orohippus we observe that in the lower levels a certain cusp is adumbrated in shadowy form; on a slightly higher level it is distinctly visible; on a still higher level it is fully grown. We do not observe any sudden breaks, but a series of minute gradations, always in the direction of adaptation, because it appears that these changes in the teeth, which Osborn has called “rectigradations,’? may be of the same kind as those to which Waagen applied the term ‘‘mutations’”’ in observing shells of successive geological levels. Whenever a new character is thus gradually brought to perfection, the animal is assigned a new spe- cific name; Hohippus validus becomes Hohippus venticolus, or Orohippus ballardi passes into Orohippus progressus. When a number of these new characters thus gradually assemble in different parts of the tooth series, or in the feet, we assign a new generic name: Hohippus becomes Orohippus, or Orohippus becomes Epihippus. The specific and generic names which were applied both in Europe and America to the Eocene horses by Owen, Cope, and Marsh were in every case defined by the presence of such slowly evolving new characters or groups of characters. Now the time-keeping value of mammals lies in the fact that in Great Britain, in France, in Switzerland, in the Rocky Mountains, in short, wherever these inconspicuous but important ‘rectigradations’ are appear- ing, they arise at approximately the same rate and approximately in the same order even among animals which are widely separated geographically. Close geologic synchronism, moreover, requires a comparison of the entire fauna and entire flora. The survival of a few primitive or arrested types may mislead, as in Australia, for example. Huxley ' was somewhat doubtful of the time-keeping value of fossils; at least he thought the ap- plication might be overdone. He went so far as to say, ‘“‘It is possible that similar, or even identical, faunze and florze in two different localities may be of extremely different ages, if the term ‘age’ is used in its proper chron- ological sense.”’ Such a possibility as Huxley imagined has never been more than partly realized. Among the mammals as well as among the plants there is a constant progression which is, on the whole, a guide or index to synchroneity. This does not preclude such broad statements as the following: that the general aspect of modern Africa resembles that of Pliocene Europe. Various Evidences of Synchronism and Homotaxis When we attempt to compare what is going on in the Old and New Worlds during the enormously long time which is called the Age of Mam- ‘Huxley, The Anniversary Address of the President. Quart. Jour. Geol. Soc. London, Vol. XXVI, 1870, pp. 29-64; Scientific Memoirs, Vol. III, p. 526. 46 THE AGE OF MAMMALS mals we should not limit ourselves to mammals, but should appeal to as many classes of facts as possible, facts of climate, of geology, of physiog- raphy, of migration and colonization, and the rise, dominance, and decline of certain kinds of animals and plants. In comparing the mammals of the two regions we look for the following tests: 1. Presence of similar species. — Those classic or time-honored bases of comparison in establishing percentages through the presence or absence of similar genera and species lead us to most interesting results, because they prove that the mammals of the Old and New Worlds were alter- nately brought together and separated. In other words, there was an alternating convergence and divergence of the faunas. The resemblances will first be very numerous and close, then there will come an estrangement when they will be very few, then the resemblances will suddenly increase again. It is obvious that only during the periods of faunal resemblance are we able to use the following or second method of comparison. 2. Similar stages of evolution. — This second method of comparison is based upon the similarity in the stages of development of like phyla of the mammals on the two continents, as expressed in the detailed changes in the grinding teeth (molars and premolars), in the numerical reduction of the digits, ete. For example, the different transformations of the pre- molars, or anterior grinding teeth in the horses, rhinoceroses, and tapirs during the Eocene and Oligocene Epochs afford very exact data for corre- lation purposes. 3. Simultaneous appearance or introduction of new mammals. —'The sudden appearance both in the Old and New Worlds of mammals which have no known ancestors in lower horizons and have apparently originated elsewhere is of great value in correlation. These coincident immigrations from unknown northern regions (Eurasia) or from southern regions (Africa) in several cases give us very exact datum points; for example, certain kinds of modernized mammals simultaneously appear in Europe and in North America in Lower Eocene and again in Oligocene times. 4. Intermigration periods. —'These periods are those in which con- spicuous interchanges of mammals took place, as between North and South America in the Pliocene. The horse (Hquus) being unquestionably derived from North America, its earliest appearance in North America must antedate its first appearance in South America. 5. Predominance of certain kinds of mammals. — Many related families of mammals seem to go through a cycle of gradual ascent until they attain a stage of world-wide predominance at about the same periods. For example, the climax of the odd-toed ungulates (Perissodactyla) is in the Middle and Upper Eocene of Europe and North America, while the oe of the even-toed ungulates (Artiodactyla) comes at a later period. , ae ee INTRODUCTION 47 6. Extinction periods of certain mammals. — World-wide predominance has its counterpart in the world-wide disappearance or extinction of cer- tain forms, correlated with grand geologic and physiographic changes. An example of this kind is the very general extinction of browsing types of Herbivora during the Oligocene. Among rodents, the beaver-like Steneo- fiber disappears at the same time both in Europe and North America, or is replaced by modified forms. This general comparison of the evolution stages of the Old World and the New World will naturally become precise and final only after the time in the Old-World stages and in the New has been separately established and defined. Thus there are correlation problems, as follows: European or Eurasiatic Correlation. American Correlation. American and Eurasiatic Correlation. North and South American Correlation. When these four broad problems of American-Asiatic-European-African correlation and of the broader New and Old World correlation are worked out we shall be able to establish a complete and very accurate geologic time scale for the entire Age of Mammals, and to speak with precision re- garding the time of successive migrations, appearances, and extinctions. It is even possible that we shall be able in the New and Old World to em- ploy the same stages or subdivisions of the Epochs of time. Geologic Formations and Life Zones The earth’s crust is made up of a vast series of separate deposits which are technically known as ‘formations.’ The formation is the geologic unit. It may vary in thickness or in extent of geographic distribution; it may be laid down in many ways, such as by the transporting power of water or of wind or through falls of volcanic ash, but it is of the essence of a ‘forma- tion’ that the conditions of deposition remain more or less uniform; when the conditions change, as from fresh-water to marine, for example, we pass into a new formation. If animal remains are varied in the formation, we may select among the number a very conspicuous or abundant or unique mammal as especially distinctive of the whole formation or of a certain level in the formation as marking off a life zone. The word ‘beds’ previously used in a similar sense is liable to cause confusion because it has also been applied to geologic formations. It is clear that while the geologic formation may be limited in extent, the life zone, owing to the wider geographic range of the mam- mal from which it takes its name, is not limited, but may be found else- where. For example, in southwestern Wyoming there is a very thick, more or less uniform deposit of voleanic ash, or tuff, which has been named the 48 THE AGE OF MAMMALS ’ BripGER ForMATION, from its proximity to the famous old Fort Bridger.* The entire formation is 1800 feet in thickness. The upper half of it is distinguished by the sudden appearance of a very large and distine- tive quadruped, Uvintatheriwm, named after the adjoining range of Uintah Mountains, which are on the boundary between Wyoming and Utah. This animal is so very distinctive that we may speak of the Upper half of the Bridger formation as the UrnraTHERIUM ZONE. One hundred miles east of the Bridger is a deposit known as the Washakie, and in the lower half of this we find the same quadruped, Uintatherium, very abun- dant and characteristic. Thus the Lower Washakie is also inthe Uinta- therium Zone. From the presence not only of Uintatherium but many other animals in common we are able to correlate these two formations, as follows: FORMATIONS ZONES Rare | os Eobasileus zone ee | Jet | Eee = Uintatherium zone ee ue Orohippus zone This single example illustrates how all fossil-bearing formations may be correlated with each other where they contain similar life zones. This furnishes a simple key to the elaborate correlations which the reader will find in the later pages of this work. The above is a striking example of an overlapping in time; that is, while the upper half of the Bridger Forma- tion was being deposited, the deposition of its more or less distant neigh- bor, the Washakie Formation, began. In this case the two formations happened to be somewhat similar in their rock composition, both being composed of voleanic ash; but another Uintatherium life zone might be found in a formation of river sand or clay. Thus the life zone enables us to synchronize geological formations of many different kinds which may be widely distributed geographically, and may vary greatly in thickness. It is obvious that the correlation of innumerable fossil-bearing formations of the Old and New World respectively can be made much closer and more exact than the correlation of the Old and New World combined; yet the method of investigation is in each case the same. It should be based on: 1. Comparisons of animals of similar mutative, specific, and generic stages. 2. Evidences of similar local evolution. 3. Dominance or scarcity of similar animals in the fauna as a whole. 4. Diminution, disappearance, or apparent extinction of similar forms. 5. First appearance of similar forms, apparently by migration or invasion from some other region. ' See Osborn, H. F., pp. 50 ff., Cenozoic Mammal Horizons of Western North America. U.S. Geol. Surv., Bull. 361, 1909. ROCKY MOUNTAIN BASIN GREAT PLAINS ZONES DEPOSITS. DEPOSITS OREGON Glyptotherium RATTLESNAKE Ticholeptus ae 300" MIOCENE Pets MIOCENE la] On OLIGOCENE a Merycocheerus eae aa eae Fe eh ei G PEUCOCT UCTS NES) Pronierycochoerus Diceratherium Leptauchenia OLIGOCENE BRIDGER BASIN (wyo.) UPPER 3¢Faunal Period HUERFANO PARK (COLO.) MIDDLE HUERFANO Lotitanops = (EVANSTON, , us SAN JUAN PARK ° (NEW MEXICO) Lambdotherium ac y 3 =i Lower | 2506] < plies es, uv be aA $ I 2 Coryp: = ‘orvphodorn z 1500 = and wae Eohippus roxy union INTRODUCTION OF ANCESTORS (OFMODERN MAMMALS 2¢ Faunal Period rood KS BASAL ez ——— ONLY WY), Pantolambda FORT UNION Polymastodon CLOSE OF THE AGE OF REPTILES EXTINCTION OF DINOSAURS By permission of the U.S. Geological Survey. Fig. 10.—Suecessive and overlapping Formations of the Rocky Mountain Region in Eocene and Oligocene times. Key to the series of scale sections in the subsequent pages ; all the sections are drawn to same scale. The horizontal dotted lines indicate the boundaries of similar Life Zones. E 50 THE AGE OF MAMMALS Sources of error in correlation. — Evidence of these five kinds as the basis of the correlation of formations contains several sources of error. First, we should always be on our guard against imperfections in records and should keep in mind the possible presence, while a given formation was being deposited, of mammals which perhaps escaped fossilization or whose fossil remains have not yet been discovered. We must not too hurriedly assume the absence of a mammal from an entire continent or even from the geographic region of a certain formation simply because it has not yet been discovered in that formation. Many mammals long con- sidered absent from the entire American Eocene, for example, the peculiar armadillo-like forms of South America, have recently been discovered in the Bridger Formation above mentioned. Again, some mammals living near the larger streams or along the shore lines are much more apt to be caught and entombed in certain formations than others living at a dis- tance, in the forests or out on the uplands, for example. Most formations are limited in geographic extent, and we must always keep in our imagination the life of the vast outside areas which were also thickly populated, with their differences of habitat, of longitude, or eastern and western distribution, of latitude, or northern and southern distribu- tion, of altitude, or vertical distribution, such as on mountain ranges and in the valleys; in short, there were always in past times such differences of distribution as exist among mammals to-day, which render it improb- able that the restricted area of a given ‘formation’ will give us an ade- quate picture of the entire contemporary life of a continent. Progressive Correlation European Correlations. —The foundation for the correlation of Euro- pean formations with each other naturally began with the early work of Cuvier and advanced with the progress of mammalian paleontology on the continent. In France, Gervais (’59, ’69), Gaudry (’62, 773, ’78, ’86, ’88, etc.), Filhol (’77, ’79, ’81, ’88, ’91), Lemoine (’78, ’80, ’82, ’85, ’87, ’88), Boule (’83, ’88, 93, ’96, ete.), and especially Depéret (’87, ’90, 92, ’93, ’00, 05, 06) have successively described typical horizons or formations and the mammals characteristic of them. Parallels between the formations of England and France were early set forth by Owen (’60), followed by Sir Joseph Prestwich (’88), and William Boyd Dawkins (’80, 94). Par- allels with Germany have been especially treated by Von Zittel, Schlosser (88, ’83-’97, 790, ’95, 02), and Depéret (’85, ’87, ’90, 92, 93, ’05, ’06, ete.).’ The first step in correlation through faunal parallelism, or similar life zones, is naturally to assemble as full a list as possible of the character- istic species and genera of mammals. Valuable tables of such European faunal parallels are those given by Von Zittel in his great Handbuch der 1 Principal titles are given in the Bibliography. ~ INTRODUCTION aid Paleontologie (1876-1893). Full and more precise lists of the European mammals characteristic of different formations or horizons are those as- sembled by Schlosser (1887-1890). The Literaturbericht (1883-1897) of the same author, a complete review of the literature of mammalian palzontology for the fourteen years indicated, is a mine of wealth for an investigation of this kind. Up to 1896, however, there still existed no satisfactory correlation of all the Old World horizons with each other, and it was obvious that a unified Old World system was absolutely necessary as a starting-point for exact comparison with the formations of the New World. Realizing that an acceptable working basis could only be secured by codperation, Osborn drew up in 1897 a Trial Sheet of the Typical and Homotaxial Tertiary Horizons of Europe and circulated it for criticism and suggestion. Invaluable corrections were received, especially from the author’s friends Gaudry, Von Zittel, Schlosser, Pavlow, Boule, Lydekker, and Depéret. The corrections were embodied in a Second Trial Sheet (April 15, 1898), which was used for further personal investigation and dis- cussion with the above-named palzontologists, also with Lepsius of Darm- stadt and Forsyth Major of the British Museum. A Third Trial Sheet, issued in 1900, was more accurate than its predecessors, but still lacked the desired exactness and fullness. The general state of knowledge in 1900 was brought together in the author’s paper, ‘‘Correlation between Tertiary Mammal Horizons of Europe and America.”?' In June, 1905, there began in the Comptes Rendus de l’ Académie des Sciences the epochal series of papers by Depéret entitled L’évolution des Mammiferes tertiaires ; im- portance des migrations. These papers covered with the desired fullness and precision the subject of the correlation of all the mammal-bearing formations of Europe, and moreover treated briefly and with great preci- sion the succession of mammalian life in Europe, and the supposed migra- tions between the continents of the main land masses of Europe, Asia, Africa, and North America. Depéret’s life zones and faunistic subdivisions of the Old World are adopted throughout the present volume as the stand- ard for comparison with the New World. His correlation of formations is graphically expressed in a full series of maps. (See Figs. 26, 50, etc.) American Correlation. —The chronological correlation of American mammal-bearing formations with each other opened in a very promising way through the exact methods which characterized even the early ob- servations of the geologist Hayden and the paleontologist Leidy on the geologic formations of our Great Plains. Naturally errors crept into such a rich and new field, where many formations were so similar to each other in external appearance, and in a period of geologic thought which preceded 1 Osborn, H. F., Correlation between Tertiary Mammal Horizons of Europe and Amer- ica; An Introduction to the more Exact Investigation of Tertiary Zoégeography; Prelimi- nary Study with Third Trial Sheet. Ann. New York Acad. Sci., Vol. XIII, no. 1, July 21, 1900, pp. 1-64; and, Corrélation des horizons de mammiféres tertiaires en Europe et en Amérique. C. R. 8° Cong. géol. intern., 1900, pp. 357-363. 52 THE AGE OF MAMMALS a clear separation of the Oligocene, Miocene, and Pliocene faunas, but we cannot repress our admiration for the admirable attempts at precision on the part of Hayden and Leidy whereby Oligocene and Miocene mamma- lian faunas were separated off into six successive faunistic stages indicated by the letters A, B, C, D, EH, and F. Unfortunately this standard was not followed, and slow progress was made for many years, owing to very loose methods of collecting fossils for purely anatomical and descriptive purposes without closely recording geo- logic levels and life zones. Nevertheless considerable advance was made in the successive writings ' of Cope (1879, 1884), Marsh (1877), Scott (1887, 1893), W. B. Clark (1891, 1896), Dall, (1896, 1897), Wortman (1893), Os- born (1897, 1898, 1900). In the survey (1898) of the Middle Eocene Washakie Basin, Osborn and MeMaster prepared the first geologic section which recorded the ‘levels’ on which different species of mammals were found.* The starting-point of the admirable precision of recent work was Hatcher’s survey between 1886 and 1888 of the Lower Oligocene of the Great Plains, summed up in his paper, ‘‘The Titanotherium Beds,” * in which he exactly described the stratigraphy, the geographic distribution, and the division of the T7tano- therium Zone into Lower, Middle, and Upper levels. This was followed in 1893 by Wortman’s paper “On the Divisions of the White River or Lower Miocene of Dakota,” * which treated precisely the succession of mammals in the entire White River formation, now considered of Oligocene Age. In 1899 all the formations both of the mountain region and of the Great Plains of the West were for the first time accurately reviewed and compared by Matthew in his important paper, ‘A Provisional Classification of the Fresh-Water Tertiary of the West.’’* This paper was accompanied by a discussion of all the preceding work of correlation, by a review of all the principal formations then known, and by a complete faunal list of the spe- cies of mammals hitherto described, the first which had appeared subsequent to Leidy’s great list published in 1869, thirty years previously. The next review of the American life succession during the Age of Mammals is that of Osborn (09), entitled ‘‘Cenozoic Mammal Horizons of Western North America.” * This comprehensive paper, accompanied by “Faunal Lists of the Tertiary Mammalia of the West,” by W. D. Matthew, forms the American basis of the present volume. American and European Correlation. —This broader study has also advanced step by step, beginning with the comparisons made by Leidy, 1 Principal titles are given in the Bibliography. * McMaster, J. B., Stratigraphical Report upon the Bridger Beds in the Washakie Basin, Wyoming Territory, accompanied by profiles of three sections. In Osborn, H. F., A Memoir upon Loxolophodon and Uintatherium, two Genera of the Suborder Dinocerata. Contrib. E. M. Mus. Geol. Arch., College of New Jersey [Princeton], Vol. I, 1881, pp. 1-54. * Hatcher, J. B., The Titanotherium Beds. Amer. Natural., March 1, 1893. pp. 204-221. 4 For reference see Bibliography. INTRODUCTION 53 and has aroused the interest of all mammalian paleontologists in turn, including especially ' Cope (1879, 1884), Filhol (1885), Marsh (1891), Scott (1888, 1889, 1894), and Osborn (1900, 1909). Especially interesting historically are Cope’s first comprehensive papers, “‘The Relations of the Horizons of Extinct Vertebrata of Europe and North America’’ (1879), “The Horizontal Relations of the North American Tertiaries with those of Europe”’ (1883),* compared with Filhol’s Critique of these papers (1885). The most comprehensive recent paper is W. H. Dall’s “A Table of the North American Tertiary Horizons correlated with one another and with those of Western Europe; with Annotations” (1898). Dall’s attention is especially directed to the southeastern portions of the United States, particularly Florida, where an alternation of marine and fresh-water forma- tions with vertebrate and invertebrate life zones affords a very direct method of correlation with the European geological stages, which are nota- bly distinguished by the alternation of marine and fresh-water conditions.’ Geological Formations as a Record of Environments Our knowledge of what may be called the procession of environments in different parts of the world during the Age of Mammals is derived from three sources. First and foremost, from the structure of the animals themselves, which fairly mirrors the habitat in which they lived; second, from the impressions of plants which the rocks may contain; third, from the nature of the rocks in which the fossil remains are found entombed. These three kinds of evidence give us as complete a picture of the environ- ment as we can ever hope to obtain, and they must be studied together. They give us a vista of the succession of the meteorologic or climatic phases of the period, of the general passage from warmer to cooler temperatures, from moister to drier conditions. We are enabled to restore physiographic conditions by separating the animals which naturally inhabit well-watered forests, lowlands, and rivers from those naturally frequenting plains and uplands, by separating those adapted to softer ground from those adapted to dry, partially arid plains, and by adding to this information that de- rived from evidences of successive fluviatile, flood plain, and aerial or zeolian deposits. Therefore the examination of the rocks in which mammals are contained is little less important and interesting than the examination of the fossils themselves; the two studies should go hand in hand. Beside the examination of the rocks another feature of geologic study which dovetails with the palzontologic is the exact and precise record- 1 Principal titles are given in Bibliography. 2 U.S. Geol. and Geog. Surv. Terr. Bull., Vol. V, no. 1, 1879. 3 Cope, E. D., Section 2 of The Vertebrata of the Tertiary Formations of the West, Book I, 1883, pp. 21-45. 4U.S. Geol. Surv., 18th Ann. Rept., 1896-1897. 5 See Dall, Geological Results of the Study of the Tertiary Fauna of Florida, 1886-1903. Trans. Wagner Free Inst. Sci. Phila., Vol. III, Pt. 6, 1903, pp. 1541-1620. 54 THE AGE OF MAMMALS ing of levels. In strata like those of our American Oligocene, where depo- sition has been extremely slow, every foot of level may mark a long period of time; fifteen or twenty feet, or even less, may mark a time during which one species passed by mutation into another. PaE I if x | | i 5098s A carig ’ | | bY k : | - : : eH | [Ss no o= ee} aa > =, = Fic. 11.— Chief areas of deposition in the Cenozoic of North America: black = littoral depositions of the Atlantic-and the Pacific coasts; dotted = ‘coutinental’ formations of the Great Plains and of the Mountain Regions. After W. B. Scott. INTRODUCTION vo This naturally introduces us to a closer examination of geologic forma- tions of various kinds. As shown above, while the geologic unit is the “formation,” “life zones’ may occur in formations totally differing in thickness, in the kind of rock, in geographic extent, in mode of deposition. These largely geologic data are, however, of constant service to the paleontologist as part of the record of the past conditions under which the animals lived. The map of North America on page 54 illustrates clearly the two great divisions in the kinds of formations, namely, the border areas of marine, estuarine, and fluvio-marine deposition of formations (indicated in black) and the central areas of continental deposition (indicated in dots). Connected with this distribution is naturally the power which transported the sediments, whether of the sea or in inlets of the sea, whether of streams or rivers, or even of the wind. Sorted as to the transporting power, the various kinds of formations in which fossil remains of mammals occur are as follows: ) 1. Marine. Beneath the ocean or along its margins. Such formations ocea- sionally contain the remains of land and freshwater mammals, mingled with those of marine mammals and shells. 2. Hstwarine. Brackish water deposits along the inlets of seas and at river mouths; also indicated by the remains of animals. 3. Flu- viatile. Freshwater sediments deposited in river channels or bays, at the mouths of streams, or in torrent fans. 4. Lacustrine. Freshwater deposits borne into lakes by rivers or streams, which beyond the coarser entrance areas may be of the finest grain and become evenly stratified through periodic sedimentation. 5. Flood plain or overflow deposits. Through periodic overflow, as of the Mississippi or the Nile. Vast stretches of country flooded with muddy water, which subsiding may also leave a stratified sedimentation. Very characteristic of the Middle Tertiary of North America. 6. Lagoon deposits. In abandoned river channels and shallow lakes which through evaporation may collect gypsum and other salts. Very fre- quent in the Cenozoic of France. 7. Molian or aerial deposits. Transported by the wind on dryland surfaces, usually fine non-stratified sands and dust, always lacking the regular horizontal lines which may characterize lacustrine and flood- plain deposits. Frequent in the later Cenozoic of North America. 8. Cave deposits. Bones of animals living in caves, fallen or dragged into them, inclosed with other fine sediments. Where over-abundant they may consolidate into a “phosphorite” or phosphate deposit. Frequent in the Pleistocene of North America and Europe. 9. Fissure deposits. Bones accumulated in the same manner as in caves, or by wind or water action, in fissures of the rock, more or less consolidated, also sometimes forming “phosphorites.” Frequent in the Cenozoic of Europe, as the famous fissure deposits of Egerkingen, of Lissieu, of Quercy. The remains of fossil mammals may be deposited under any of the above conditions and thus occur in formations of many kinds. The least perfectly preserved are those washed along with coarse pebbles and gravels, while the most perfect as a rule are those found in the fine sediments of still water, of zolian dust, of asphaltum, or of volcanic ash. 56 THE AGE OF MAMMALS Fic. 12. — The imbedding of skeletons in eeolian, or wind-drift deposits. Above: Recent times. Partially imbedded skeleton of an ox on the plains of South Dakota. Below: Miocene times.- Partially exhumed skeleton of the fossil forest horse, Hypohippus, on the plains of Colorado. The chief kinds of mammal-bearing rocks, that is, sorted as to mineral composition, are as follows: 1. Conglomerates (“Conglomérats,” ‘“ Konglomerate’”’). Composed of weather- worn pebbles, gravels, and sands. They are evidence either of advancing or re- treating shore lines of the sea or of river channels, or mountain streams where they spread upon the plains. ‘Mud-ball’ conglomerates are rather common in the western tertiaries. On the old sea borders of Eocene France we find the Gravier INTRODUCTION 57 marin de Cernay, de Meudon. In the great Oligocene Bad Lands of South Dakota it is most interesting to find the coarser sediments of a ‘river channel’ traversing a fine ‘overflow’ deposit, each containing its characteristic forms of mammalian life. Both in the deposits of the mountain regions and plains regions of the western United States great and small areas of these sediments occur containing either weatherworn or often battered fossils. 2. Sandstones (“Grés,” ‘“ Sandsteine’’). Composed chiefly of quartz sand or sometimes of feldspar grains (arkose sand- stones), associated with deposits of volcanic origin, as in the Bridger Formation. Sandstones, due to sea and river action, naturally cover wider areas than the coarser conglomerates, which they often adjoin, because they display the transporting power of slower water action or higher wind action, as in deserts. Characteristic of late Pleistocene and Glacial times. 3. Shales (‘“Argile schisteuse,” “ Schiefer- thon”). Chiefly fine mud sediments, deposited in still or comparatively still water and exhibiting more or less perfect horizontal or oblique cleavage or lamination. Often contain beautifully preserved leaves and remains of fossil fishes, as the Green River Shales. Rarely contain remains of mammals. 4. Clays (“Argile,”’ “limon,” “Thon”). Due to river, flood plain, or deep water action, these are uniformly fine sediments, typically of continental origin, in large part a consolidated loess. The true “plastic clay” or argile plastique is mostly of marine origin and results from the final decomposition of feldspar. The famous London Clay, containing Hyraco- theritum, 1s an estuarine formation. 5. Loess (‘“‘Loess”’ in French and German). Characteristic of late Pleistocene and Glacial times. An unconsolidated, fine, porous, silicious silt, deposited on river flood plains, in back waters, and by the agency of the wind on dryland surfaces and (according to some authors) as glacial mud. Water-borne and wind-borne loess are hard to distinguish; some loess is of joint origin. In some regions loess is composed of volcanic ash more or less altered by weather and river erosion. Where of flood plain origin it may show horizontal color banding, due to seasonal floods, or in wolian loess to the direction of preva- lent winds. A partially consolidated loess would be commonly called a clay; when further consolidated, a shale. The most famous loess deposit is the Pampean formation of Argentina, rich in mammals. 6. Volcanic ash and tuff (“Tufs,” “Tuff’). The great constituent of the Mountain Basin formations of North America. Composed of volcanic ejecta, containing many feldspathic particles. Where wind-borne, the ash resembles loess; where water-borne, volcanic ash forms tuffs. Examples are large parts of the Bridger, Wind River, and other mountain basin formations of North America. 7. Lignites (“‘Lignites,” ‘“ Braunkohle’’). Rare as a Cxenozoic formation in America, common in the Eocene of Europe, as the Lignites du Soissonais, de la Débruge, de Cadibona. 8. Gypsum (“Gypse,” “yps”). Formed by evaporation of lagoons. Afford an invaluable indication of climatic conditions. The most famous deposit of the kind is the Upper Eocene Gypse de Montmartre, near Paris. 9. Limestones (‘‘Calcaire,”’ “ Kalk’’). Limestones, as the Calcaire grossier of the Upper Eocene of France, are chiefly calcareous (car- bonate of lime), sometimes of organic origin, or formed by the accumulation of shells; sometimes by deposition from water holding lime in solution. Traver- tines are calcareous deposits formed from hot springs. 10. Marls (‘‘ Marnes,” “ Mergel”). Loose or unconsolidated deposits of earth, of lime, of shells, ete., rich in organic matter. Phosphate Beds are marls or other formations rich in phos- phate of lime, such as those of South Carolina; they are littoral and estuarine in 58 THE AGE OF MAMMALS origin and may contain the intermingled remains of land and seaanimals. 11. Phos- phorites (phosphate of lime) (‘‘Phosphorites,” “Phosphorit”). Also of organic origin, directly or indirectly derived from the hard parts of animals, or from the excrements of animals. 12. Asphalt or asphaltum (“ Asphalte,” “ Asphalt.) The residuum of pitch lakes left by the evaporation of petroleum springs. A remark- able asphaltum deposit (Rancho La Brea, see Fig. 205) has recently been found in the Pleistocene of southern California, containing a rich variety of mammals in remarkable preservation. 13. Breccias (“Bréche,”’ “ Breccia’). Formed by the filling in of bones and gravels cemented together by calcareous waters. V. DuRaATION oF THE AGE OF MAMMALS How long was the Age of Mammals? How many years ago did it begin? How may we find out? If we remark, for example, that Hohippus, the first stage in the development of the horse, was an animal which lived about three millions of years ago, our hearer looks incredulous and has a perfect right to ask, What are your grounds for assigning such an enormously long period of time? There are a great many ways of estimating geologic time, all of which either depend on the comparison of past processes with present processes of earth formation, or make an appeal to astronomic data, such as the procession of the eclipses, the eccentricity of the earth’s orbit, or the consolidation of the earth’s crust and the period necessary for cooling sufficiently to admit of life. A vast period. — Whatever method of calculation we adopt, a glance at the accompanying diagram shows that the Age of Mammals, while vastly long in itself, was relatively short as compared with all the life periods which preceded it; it was estimated by Dana in 1874 as occupying only one-sixteenth of the whole life period, by Wallace in 1895 as occupying one- twentieth of the whole life period. Each of these Ages represents a vast interval, as attested both by the great geographic changes which occurred in them, by the great mountain chains which were thrown up and then com- pletely reduced to the general level, by the enormous thickness of the sedi- mentary deposits which were laid down on land and sea, recently estimated at a total of 265,000 feet or upwards of 50 miles (Sollas, 1900), or 335,800 feet (Sollas, 1909), and still more perhaps by the great changes in the ani- mal and plant life which are recorded in the fossils." Mountain births. — Biologists from Darwin to the present time have demanded long periods for these evolutionary changes and for the Age of Mammals itself. As a measure of the lapse of time the comparison of the great advance in size and structure between the Eocene Hohippus and the existing horse (Equus) (Fig. 14) is perhaps less impressive than a review of the great mountain births which occurred during the Age of Mammals. The Rocky Mountains, it is true, began their elevation during the close 1 See Poulton, 1896, A Contribution to the Discussion of the Age of the Earth, Essays on Evolution, 1908, p. 15. ‘ = ee ee Oe PERIODS HIMALAYAS ce) SWISS ALPS 8 Sens, Zz MOUNTAIN PYRENEES iy EASTERN ALPS (LARAMIE) (Partly) Q fe} N | eS SIERRA NEVADA = PALISADE APPALACHIAN ‘HE HERCYNIAN BELT OF CENTRAL EUROPE ? ACADIAN 2) [e) N [e) x SCOTTISH HIGHLANDS Z SILURIAN a SILURIAN TACONIC ORDOVICIAN ORDOVICIAN 17000 CAMBRIAN CAMBRIAN 16000 ? PRE-CAMBRIAN ALGONKIAN 1 ' | ALGONKIAN FINLAND SBOHEMIA ~ x _ 2? ARCHAEAN ARCHAEAN ARCHAEAN Fic. 13.— A diagram showing what the total thickness of the earth’s crust would be if all the surface deposits since the time of the first appearance of life had accumulated on top of each other. Age of Mammals = dots. Age of Reptiles = vertical lines. Age of Amphibians and Fishes = oblique lines. The births of American and Eurasiatic mountain systems are indicated by incisions of the right and left hand columns respectively. 60 THE AGE OF MAMMALS of the Age of Reptiles; they had only attained a height of four or five thousand feet when the Age of Mammals commenced; they continued to rise during the entire period. But consider the map of Europe and Asia at the beginning of Eocene time and realize that the great mountain systems of the Pyrenees, the Alps, and the Himalayas were still unborn, level surfaces in fact, partly washed by the sea. As shown in the dia- gram, the birth of the Pyrenees was at the beginning of the Oligocene. At this time Switzerland was still a comparatively level plain, and not until Fic. 14.— Duration of the Age of Mammals as measured by the evolution of the horse. Skeleton of the Eocene four-toed horse, Hohippus, and of the Texas Lower Pleistocene horses, Equus scotti. In the American Museum of Natural History. the close of the Oligocene did the mighty system of the Swiss Alps begin to rise. Central Asia was even yet a plain and upland, and only during the Miocene did the Himalayas, the noblest existing mountain chain, begin to rise to their present fellowship with the sky. In North America again, since the close of the Eocene the region of the present Grand Cafion of the Colorado has been elevated 11,000 feet and the river has carved its mighty cafion through the rock to its present maximum depth of 6500 feet. Those who have been impressed with a sense of the antiquity of these wonders of the world and will imagine the vast changes in the history of continental geography and continental life which were involved, will be ready to concede that the Age of Mammals alone represents an almost inconceivable period of time. INTRODUCTION Modes of Estimating Cenozoic Time 61 From the rocks themselves there are several modes of calculation: 1. Total thickness of the formations composing the so-called sedimentary rocks, compared with the average rate of accumulation, deposition, and sedimentation observable to-day. 2. Denudation and erosion, the counter processes, or the wearing away of elevated surfaces by the action of water and wind, snow, ice, and frost. Estimates of former heights of mountains, ete., and of the length of time during which these erosive agencies have been at work. 3. Chemical content of the sea, based on the assump- tion that all the salts and mineral elements of the sea are derived by solution from the soil. 4. Procession and recession of the glaciers as a means of estimating Pleistocene or Quaternary time by comparison of past with present advances and retreats of glacial masses. Obstacles confront every mode of making these comparisons of past and present processes. In estimat- ing past rates of accumulation by those observed in the deltas or mouths of existing rivers, the disturbing and unnatural influence of man must be considered. The modern delta accumulations of the Mississippi, the Po, the Danube, the Tigris, the Euphrates, and the Ganges are probably unnaturally rapid because the soil of the drainage basins from which these deltas are formed has been disturbed by the unnatural erosion hastened by human cultivation. In the case of the Tigris and Euphrates, the making of from forty to fifty miles of new land in the Persian Gulf, so that ancient seaports of four or five thousand years ago are now far inland, is very largely due indirectly to human agency, namely, to the destruction of the forests, the unrestricted brows- ing of sheep and goats, and the consequent rapid de- nudation of the soil. Deposition or accumulation. — An outline of the methods employed to calculate rates of deposition may be found in Williams’s “Geological Biology” (1895). according to the calculations of Humphreys and Abbot, A wo Fie. 15.— Duration of the Age of Mam- mals as measured by the evolution of the teeth of the horse. Su- perior grinding teeth of Hohippus (below), and of Equus (above), drawn to scale and showing the great in- crease in complexity as well as in length (A) and width (2B). The Mississippi, brings down every year sediment equivalent in amount to a mass 268 feet deep and one square mile in extent. Assuming the area of distribution to be 50,000 square miles, the deposit would reach a depth of 50 feet in about 10,000 years, or one foot in 200 years. Forshay estimated the Mississippi ac- cumulation as four times as rapid, or at the rate of one foot in 50 years. The most precisely measured flood plain in the world is that on either 62 THE AGE OF MAMMALS side of the River Nile. It is found that by the annual overflow the sediments accumulate at the rate of two feet and ten inches in 100 years.! Again, illustrating the difficulty of forming estimates from present rates of accumulation or deposition, the estimates given by Geikie in 1892 may be cited, which show'that the sedimentary deposits at the mouth of the Po are much more rapid than those at the mouth of the Danube. Denudation or erosion. — Estimates based on denudation confront similar difficulties. Haughton’ in 1878 found the mean rate of denuda- tion of the surface in the several great river basins of the world to be one foot in 3090 years. A most ingenious method of measuring the rate of erosion is the ‘cedar-root chronology,’ which appears to have been invented by James Hall * in 1871. He made an elaborate study of the rate of ero- sion along the valley of the Mohawk River in New York, based upon the estimated age of nineteen cedar trees, the length of the exposed root, and the recession of the cliff per century. From this he calculated that 35,000 years was the minimum of time since the Cohoes Falls were opposite the pothole in which the famous ‘Cohoes mastodon’ skeleton was deposited. The same method was used by Knight * in 1899, of especial interest be- cause the observations were made in a well-known fossiliferous area, at Bates-Hole, Wyoming, where there is a vast depression produced by the erosion of the Tertiary beds of Oligocene Age. On its slopes grow pine trees (Pinus murrayana Eng.) that have recorded the rate of erosion here for about 300 years. As the material was worn away their roots became more and more exposed. The oldest of the trees stand on slopes, their trunks elevated three or four feet above the slopes. On the average it was found that the trees 300 years old had about three feet of rock removed from their roots. According to this 100 years are required to remove one foot of surface. Three miles have been eroded on either side, and at the rate of one foot per century, 1,584,000 years must have elapsed since the process began. The process began not earlier than the close of the Miocene, when the highest beds of Bates-Hole were deposited. Thus the erosion must have occurred during the subsequent Pliocene and Pleistocene periods, which estimated in this way represent a duration of 1,584,000 years. On this basis it would not be out of the way to estimate the Age of Mammals at 4,000,000. Helium content.—The most recent method is that of Strutt, based upon the amount of helium found in different rocks. Helium, like the radioactive elements, accumulates in minerals, and hence if we measure i Lyons, H. G., The Physiography of the River Nile and its Basin. Surv. Dep’t. Egypt, Cairo, 1906. ? Haughton, Physical Geology. Nature, Vol. 18, 1878, pp. 266-268. 3 Hall, J., Notes and Observations on the Cohoes Mastodon. Rept. N. Y. State Cab. Nat. Hist., Vol. 21, 1871, pp. 99-148. 4 Knight, W. C., Some New Data for Converting Geological Time into Years. Science, n.s. Vol. X, 1899, pp. 607-608. INTRODUCTION 63 the amount of helium in a sample rock and the amount produced in the sample in one year, we can reckon the length of time the helium has been accumulating, and hence the age of the rock. This method may lead to determinations not merely of the average age of the crust of the rock, but of the ages of particular rocks and the date at which the various strata were deposited.! A very rough estimate of the accumulation or thickness of the Eocene and Oligocene sediments in the Rocky Mountain basins is seven thousand feet. This is an approximate figure which will in time be made exact. These sediments, however, consist largely of tuffs or partly worked over voleanic materials deposited in water. We certainly have no means of comparison with similar processes going on to-day which will enable us to estimate the time occupied in the accumulation of these rocks. Thus difficulties confront us on every side, and the most careful of our computations are mere approximations. Since, however, it is desirable to give some idea of the scientific opinion on the duration of the Age of Mammals, the following table is of interest. LencTH oF C#nozoic ErRA oR AGE oF MAMMALS Estimated by Comparison with Present Rates of Deposition and Denudation Dana 1874 3,000,000 years Based on the estimated thickness of the total series of stratified rocks and the estimated rate of accumulation of de- posits along the shores of continents at the present time. Wallace 1881 4,200,000 years Based on the rate of denudation with the (Tertiary = estimated thickness of sedimentary 4,000,000 rocks (which is probably less than Quaternary = 177,200 feet, as given by Haughton 200,000 + ) °78); and further on the dates of Walcott 1893 2,900,000 years Upham 1893 3,100,000 years (mean) (Tertiary = 2 — 4,000,000 Quaternary = 100,000) phases of high eccentricity of the earth’s orbit. Based on the total thickness of sedi- mentary rocks of North America (100,000 feet), compared with present rates of accumulation. Based on estimates of the length of the glacial stages. ‘ Thomson, J. J., Address of the President of the British Association for the Advancement of Science [Winnipeg, 1909]. Science, n.s. Vol. XXX, no. 765, Aug. 27, 1909, pp. 257-279. 64 THE AGE OF MAMMALS Knight 1899 4,000,000 years Based on the rate of denudation or erosion (Eocene-Miocene = as measured by the amount of ex- 2,500,000 app. posure of roots of pine trees of known Plio.-Pleistocene = age (1 foot in 100 years). 1,584,000) Sollas 1900 4,200,000 years Based on the rate of accumulation esti- (Tertiary = mated at 1 foot in 100 years. The 3,800,000 estimated thickness of sedimentary Quaternary = rocks (Eocene to Recent) is 42,000 400,000) feet. 1909 6,380,000 years The thickness of sedimentary rocks (Eocene to Recent) estimated at 63,800 feet. Penck 1908 Quaternary=500,000 Based on the average rate of denudation to 1,000,000 years of the present land surface (s2;5 foot in 1 year). VI. Tue Wortp Suprpity or MAMMALS The source of the world’s supply of mammals, the great homes, centers, or continents from which the orders evolved and took on their distinctive Fic. 16.— Late Cretaceous and Basal Eocene. Period of extinction of the great Reptilia. A time of elevation, favoring an interchange of archaic life between South and North America, also between North America and Europe. South America probably united with Australia via Antarctica, allowing an interchange of carnivorous and herbivorous marsupials. } “Amblypoda, Condylarthra nm oars xX Ferissodactyla, Ancylopoda Fic. 17.— Chief centers of the adaptive radiation of the orders of mammals so far as known at the present time. Atlantic land connection during a considerable part of the Age of Mammals is neither supported nor disproved by such negative evidence. Other authors‘ believe that the connections and migration routes be- tween Europe and North America were chiefly North Pacifie or via Asia and the region of Behring Straits. ; Even if the north polar center theory of Haacke be extreme and the evidence for a north Atlantic land mass is less strong than that for North Pacific land connection between the New and Old worlds, the fact remains undisputed somewhat in the form stated by Wortman, that the northern portions of Europe, Asia, and North America formed the greatest creative center, probably during the Age of Reptiles and certainly during the Age of Mammals. Striking evidence for this is found in the great number and variety of the orders of mammals which have been discovered early in Eocene and Lower Oligocene times in Europe and North America, which with Asia constitute the region Holarctica. These orders of mammals (compare p. 73) are as follows: 1See Matthew, W. D., Hypothetical Outlines of the Continents in Tertiary Times. Bull. Amer. Mus. Nat. Hist., Vol. XXII, Art. X XI, Oct. 25, 1906. 68 THE AGE OF MAMMALS Marsupialia Pholidota Insectivora Tubulidentata Chiroptera Lemuroidea Carnivora-Creodonta Condylarthra Carvornia-Fissipedia Amblypoda Rodentia Artiodactyla Tillodontia Perissodactyla Teniodonta or Ganodonta Ancylopoda Edentata-Xenarthra Zeuglodontia This imposing array may, it is true, be partially swollen by inclusion of orders of mammals which were probably indigenous to South America (Edentata) and possibly to Africa (Pholidota, Tubulidentata, Zeuglodontia), but even taking out these possibly or probably foreign members of northern society, a large residuum of mammals which probably originated in the north- ern hemisphere still remains and firmly establishes this as the dominant hemisphere in the evolution of the Mammalia. Africa, Ethiopian Region, also an Important Center of Mammalian Evolution Regarding Africa as a theater of mammalian evolution there have been two views. First, the older view that Africa derived its original primitive stock of mammals from the north and then remained passive until it received a new wave of highly specialized mammals. Second, the newer view that Africa was throughout the Age of Mammals a great center of mammalian evolution and contributed its full quota to the world stock of modernized mammals. In general it may be said that prior to 1900 the African conti- nent as a great theater of adaptive radiation of the Mammalia had not been sufficiently considered. This was chiefly because it had practically no dis- covered fossil mammal history. It was the fashion with most writers on geo- graphic distribution to speak mainly and exclusively of the invasion of Africa by European types rather than of the possible invasion of Europe by African types. Hypothesis of northern invasion of Africa. —In 1867 Riitimeyer ! expressed the opinion that at a very early period Europe sent into Africa its wealth of tropical forms. The ancient population of this continent was first fully discussed by Alfred Russel Wallace,” who also set forth the hypothesis of northern invasion, namely: that before Pliocene times Africa was occupied only by a small primitive fauna, lemurs, insectivores, edentates, and rodents, and that early in Pliocene times the large mammalian fauna of Europe and southern Asia (Pikermi and Siwalik Hills) were ‘“‘poured into Africa and, finding there a new and favorable country almost wholly unoccupied by large mammalia, increased to an enormous extent, developed into new forms, and finally overran the whole continent.” 1 Riitimeyer, Uber die Herkunft unserer Thierwelt, 1867, pp. 42-43. ? Wallace, The Geographical Distribution of Animals, 1876, p. 288. OE —- INTRODUCTION 69 In his notable paper of 1876 Blanford ! clearly implied the existence of an African element in the fauna of India, but he referred to mammals rather of recent than of early evolution in Africa. He believed ? that an Indo-African land connection (the Lemuria of other authors) across the Indian Ocean, per- sisted through the Age of Reptiles and probably lasted into early Czenozoic times, vestiges of this connection being indicated by Madagascar, the Sey- chelles, and other islands and coral reefs. Madagascar continued to form a part of the African mainland throughout the first half of the Age of Mam- mals, but was severed from it before Africa was invaded from the north, in older Pliocene and glacial times. Madagascar possesses among its fauna (Insectivora, Lemuroidea) the older mammals of the African continent which have become little modified since. Blanford also believed ? (1890, p. 73) in a connection between Africa and South America, in order to explain certain supposed alliances between some South American and African and even Madagascan types. ; Similarly Lydekker * (1896) believed that the ancestral types of the existing mammals of Madagascar entered the African continent some time during the Oligocene period and soon after ranged over the whole of the Ethio- pian and Malagasy (Madagascar, Mascarene Islands) regions, which were then broadly united and possessed a common mammalian fauna. In Lydek- ker’s opinion, Africa was peopled only with these primitive forms and not until the Pliocene Age, when Madagascar became isolated as an island, did there occur the great invasion from the north of the higher and larger mam- mals such as apes, monkeys, and the great quadrupeds which were then flourishing all along southern Europe and Asia. This migration took place (p. 256) along the eastern side of the continent and the existence of certain species of mammals which are still common to India and Africa, or were so during the Pleistocene epoch, lends support to this view. Similar theories were expressed in 1888 by Schlosser,’ namely, that the mammals of Africa seem to be partly (1) a continuation of the primitive ani- mal life found in the North American Eocene, and partly (2) a continuation of the European and Asiatic life of the Upper Eocene. Thus the present mammalian fauna of Africa seems to point to two migrations: (1) the first oceurred very early, including the primitive Insectivora, closely related to forms found early in the Age of Mammals in North America; (2) the second migration into Africa occurred in the Pliocene, bringing in the apes, cats, hyzenas, civet cats, rhinoceroses, horses, elephants, pigs, hippopotami, ante- lopes, etc. Up to this time these mammals had lived in Europe or in Asia. 1 Blanford, W. T., The African Element in the Fauna of India. Ann. Mag. Nat. Hist., Ser. 4, Vol. XVIII, 1876, pp. 277-294. 2 Td., Address Delivered at the Anniversary Meeting of the Geological Society of London, Feb. 21, 1890, p. 68 (Proc. Geol. Soc., 1890, pp. 43-110). 8’ Lydekker, A Geographical History of Mammals, Cambridge, 1896, p. 255. 4 Schlosser, M., Uber die Beziehungen der ausgestorbenen Siiugethierfaunen und ihr Verhiltniss zur Siiugethierfauna der Gegenwart. Biol. Centralbl., 1888, Vol. VIII, pp. 582-650. 70 THE AGE OF MAMMALS Hypothesis of Africa as an evolution center. — The opposing view of the invasion of Europe from Africa was independently thought out and set forth by three authors in 1899-1900, namely, by Tullberg in his monograph on the rodents, by Stehlin in his monograph on the teeth of the pig family,” and by Osborn.* Tullberg, as directly opposed to Haacke, is a strong believer in a great southerly center of distribution, and stands, like Riitimeyer, as an advocate of the bipolar theory. Thus he remarks (pp. 490-491): “In the Miocene the great African region sent its heterogeneous fauna into Asia by way of Syria or Arabia. In this way Eurasia received together with typical (southwest) African types, others of Asiatic origin that had become differentiated from their ancestral forms, in the Madagascar-East-African region. Among the latter may be counted the Cavicornia, which, though a product of Africa, were most likely originally derived from northern Artiodactyla. The Simiz, Proboscidea, and the rodent Hystricognathi are probably purely African types whose first ap- pearance in Eurasia followed the Miocene migration.”” When the Placentalia first appear they have already undergone a considerable differentiation, and since they sprang neither from the Marsupialia nor from the Monotremata, we must assume that they went through the early undiscovered stages of their evolution in some great geographic region (other than Australia); this region is presumably the great southerly continent embracing South America and Africa and reaching over to India by way of Madagascar with a broad tongue of land (the Lemuria and Gond- wana Land of other authors). Three great mammalian groups had already evolved: (1) the ancestors of the Lemuroidea and Anthropoidea; (2) the ancestors of the Ungulata; (3) the ancestors of the Rodentia-Simplicidentata. These stocks segre- gated off into two great divisions: one, East-Africa-Madagascar-Europe-Asia-N orth- America, the other Southwest-Africa-South-America. In the beginning of the Age of Mammals, Africa became separated from South America; in the Lower Oligo- cene (p. 488) Madagascar separated both from Asia (India) and from Africa. At the same time, however, the east African region joined with the southwest African region and an interchange of mammals took place. Stehlin’s views (p. 478) are still more closely parallel to those independ- ently developed by Osborn, as the following citation from his monograph 2 shows: “Africa’s part in the evolution of the animal life of the globe (p. 478) has generally been represented as very passive, but the mere fact that Africa was a large continental landmass during the entire Tertiary makes this view seem unten- able. Among the living mammals of Africa there are a number of types such as the coney (Hyrax), the aardvark (Orycteropus), and the pangolin (Manis), which differ so widely from any Tertiary Asiatic or European forms, that-the conclusion 1 Tullberg, T., Uber das System der Nagethiere, 1899, pp. 485-495. 2 Stehlin, H. G., Uber die Geschichte des Suiden-Gebisses, 1899-1900, pp. 478-488. % Osborn, H. F., Faunal Relations of Europe and America during the Tertiary Period and Theory of the Successive Invasions of an African Fauna into Europe, 1900, pp. 56-59. INTRODUCTION rai seems not far to seek that they represent the last remnants of an ancient African fauna. This hypothetical (p. 479) primitive fauna was clearly analogous to that of South America, and it seems probable that there existed a means of communica- tion between the two continents either by way of Antarctica or a trans-Atlantic landmass. It is possible that both had received their fauna from the north in pre- tertiary times. Certain it is, however, that both were later connected with the northern continents, communication in the eastern hemisphere being established much earlier than in the western, probably before the Miocene. Africa is now inhabited by mammalian types of various orders, which have become differentiated into genera and even families, and which are practically unknown among the fossil as well as the living fauna of Europe and Asia. When we consider how large a space of time is required for the development of even slight modifications, the con- clusion seems forced upon us that a large proportion of the present faunal types of Africa existed there throughout the Tertiary. The antelopes (p. 480), then as now, seem to have had their chief centre of evolution in Africa, and perhaps the giraffes likewise. Whether the horses, rhinoceroses and even the enigmatical proboscideans were native to the same continent in early Tertiary times, must remain an open question. It is very probable (p. 488) that the Pikermi fauna [a rich Upper Miocene fauna of Greece, see map, p. 267], save for the forms that can be referred back to the European middle Miocene, is derived from Africa. The way into Asia seems to have been less open at this time, no African forms having been found east of Maragha (Persia). In the Pliocene, on the other hand, communication with Asia seems to have been more intimate than with Europe. It is a remarkable fact (p. 488) that Cheropsis (the pigmy hippopotamus), and Phacocherus (the wart- hog) at no time migrated out of Africa. Perhaps Ethiopia was better able to maintain its inhabitants uninterruptedly than any part of Asia or Europe because it remained for the most part unaffected by the great marine and orogenic move- ments, and by the great lowering of temperature at the close of the Tertiary.” In 1899-1900 Osborn developed and published his ‘‘ Theory of Successive Invasions of an African Fauna into Europe.’’ He observes (p. 56): “Let us therefore clearly set forth the hypothesis of the Ethiopian region or South Africa as a great center of independent evolution and as the source of succes- sive northward migrations of animals, some of which ultimately reached even the extremity of South America — I refer to the Mastodons. “The first of these migrations we may suppose brought in certain highly special- ized ruminants of the Upper Eocene, the anomalures or peculiar flying rodents of Africa; with this invasion may have come the pangolins [Pholidota] and aardvarks [Tubulidentata], and possibly certain armadillos, Dasypodide, if M. Finnouw’s iden- tification of Necrodasypus is correct. A second invasion of great distinctness may be that which marks the beginning of the Miocene when the mastodons and dino- theres first appear in Europe, also the earliest of the antelopes. ) found in the whole Cenozoic of Europe is comparatively small, and it is difh- 1 Scharff, R. F., On an Early Tertiary Land-Connection between North and South Amer- ica. Amer. Natural., Vol. XLIII, Sept., 1909, pp. 513-531. 94. THE AGE OF MAMMALS cult to draw conclusions from fossil plant remains alone as to their relative or absolute importance. At what period grasses began to assume anything like their present dominance it is impossible to determine. The absence of native grasses in Australia is indirect evidence of their late geological devel- opment. According to Schimper and Schenck? the first record of grasses. is in the Cretaceous Age, the cane (Arundo), and the reed (Phragmites) being found in North America. According to Gardner * the determination of the meadow grass (Poacites) from the Komé beds of Greenland is very doubtful. There can be little doubt, according to Hollick, that grasses arose at an early period in the Cenozoic, perhaps even in the lowest Eocene. While Gardner (1886, p. 454) considers that they attained prominence in both hemispheres only toward the close of the Eocene, he believes it to be not im- probable that they were established in the north (Spitzbergen) at an early period. The indirect evidence derived from the adaptations of the teeth of mammals disposes us to adopt the opinion of Gardner (1886, p. 441) that grasses attained wide distribution in both hemispheres only toward the close of the Eocene. Their evolution on favorable forestless regions was certainly a very prolonged one, beginning in Mesozoic times. A southern flora. — The Tertiary flora in general* represents not only every one of the great types of vegetation but also a large number of the orders and genera of the present plant world. Passing over from the Creta- ceous into the early Tertiary, the horsetails (Equisetacez) are represented by reduced forms. Among the gymnosperms, the cyecads were waning while the Conifer, or true gymnosperms, were represented by forms closely allied to the sequoias, widely distributed and in great abundance. The true conifers or pines were of more modern origin. The palms were a dominant type which flourished in great luxuriance during the Eocene and Miocene. The dicotyledonous angiosperms which had appeared suddenly in the Upper Cre- taceous began to gain complete ascendancy, and in this group were several types which seem to be waning at the present time: for example, the sassa- fras (Sassafras), tulip tree (Liriodendron), and the sweet gum (Liquidambar). In the Eocene a luxuriant vegetation covered the northern hemisphere as far north as Grinnell Land (81° 45’’), the Arctic flora alone comprising 400 species of arborescent type. In North America the deciduous flora of the older Czenozoic was very similar to the modern flora. The processes of modification and evolution of plants were far slower than the evolution of mammals. In connection with what has been said above regarding grasses, it is important to note that the deciduous plants which we know are mainly those which grow in the lowlands. In Cenozoic times, as now, there was a great difference in the vegetation of different 1 Schimper und Schenk, Handbuch der Paliontologie (Zittel), II Abth., Paliophytologie, 1890, p. 385. 2 Gardner, J. S., Fossil Grasses. Proc. Geol. Assoc., Vol. IX, 1886, p. 441. 3 Ward, L., Plants, Fossil, in Johnson’s Universal Encyclopedia, 1895, p. 329. THE EOCENE OF EUROPE AND NORTH AMERICA 95 levels. Temperature and humidity are the most important factors govern- ing plant distribution, but we must also take into consideration the nature of the soil and other conditions of environment. Since there are so many factors governing plant distribution, it is difficult to use plants as thermom- eters of the past except in a general way, and this difficulty is increased by the fact that Czenozoic species are only related to and not identical with present species; also that many nearly related species can live under very different conditions. The most memorable fact about the flora is one recently insisted upon by Knowlton (1909),’ namely, that as we pass from the Cretaceous into the Eocene there is no appreciable change in the flora. From this it would ap- pear that there was no secular change of climate; that the temperature re- mained the same. So impressed is this palzeobotanist with these facts that he places within the Cretaceous the Fort Union Beds, which are here re- garded as Basal Eocene. ALTERNATE UNION AND DISUNION OF EUROPEAN AND NORTH AMERICAN LIFE Europe and North America to-day are on the whole closely united in their mammalian life, and were it not for the profound changes and extinctions which have been caused by man, these widely separated countries would at once be recognized as constituting one great zodlogical region, occupied by similar forms of mammalian life. The beaver, bear, wolf, stag, moose, rein- deer, bison, are some of the many connecting forms which, as Allen pointed out, constitute this a single zoélogical region, HOLARCTICA. It is astriking fact that at the beginning of Eocene times we find a similar- ity which is nearly if not quite as close as that which prevails to-day. This similarity of Basal Eocene times is intensified in Lower Eocene times. Then, however, follows a long period of disunion in the forms and evolution of mam- malian life, extending through the Middle and Upper Eocene, in course of which the mammals become so different on the two continents that a zodlogist would certainly mark them off into two entirely distinct zodlogical regions, namely, the Old World or PAL@#arRctTIcA, and the New World or NEearctica. But just when the divergence seems most extreme, there comes at the beginning of the Oligocene a fresh faunal reunion, perhaps even more close than the first. These periods of union and separation again recur. We thus have good ground for dividing the whole Cznozoic Period into a series of grand FauNAL PHASES. a. Faunal. phases. — Another means of distinguishing these faunal phases, in addition to the continental separation and reunion of the mammals, 1 Knowlton, F. H., The Stratigraphic Relations and Palseontology of the ‘Hell Creek Beds,” ‘‘Ceratops Beds’? and Equivalents, and their Reference to the Fort Union Forma- tion. Proc. Wash. Acad. Sci., Vol. XI, no. 3, 1909, pp. 179-238. 96 THE AGE OF MAMMALS is in the struggle or competition which we observe between two great divisions of mammals, which are so distinct in their affinities and evolutionary stages that they may almost be set apart as two groups. These are: I. Archaic primitive mammals, partly descended from ancestors of great antiquity in the Age of Reptiles; mostly without modern descendants. II. Mammals with modern descendants and relationships, chiefly compris- ing ancestors of existing families. The gradual dying out, or extinction, of the archaic in competition with the modern types thus affords a second important means of dividing the Ceenozoic into faunal phases. A third means of distinguishing the faunal phases, and one which lends variety to the subject, is that, especially during periods of separation, several families independently evolve in Europe and North America respectively, without interchange by migration. Through these three means we may clearly divide the Czenozoic into seven great faunal phases, as follows: I. First Faunal Phase, Basal Eocene, archaic mammals only are known. (p. 102). II. Second Faunal Phase, Lower Eocene, archaic and modern mammals intermingled (p. 112). III. Third Faunal Phase, Lower to Upper Eocene. Europe and North America separated (p. 138). IV. Fourth Faunal Phase, Oligocene. Archaic mammals extinct. Europe and North America reunited (p. 178). V. Fifth Faunal Phase, Miocene. African mammals reach Europe and North America. Europe invaded from Asia (p. 242). VI. Sixth Faunal Phase, Middle Pliocene. North and South America reunited (p. 304). VII. Seventh Faunal Phase, Pleistocene. Widespread extinction. Fresh invasion of America by European mammals (p. 374). b. The archaic mammals. — Nature deals in transitions rather than in sharp lines. We cannot cireumscribe the archaic mammals sharply, nor be sure as yet that some of them did not give direct descent to certain of the modernized mammals. Yet the mammals of the Basal Eocene of both Eu- rope and North America are altogether of very ancient type; they exhibit many primitive characters, such as extremely small brains, simple, triangular teeth, five digits on the hands and feet, prevailing plantigradism. They are to be collectively regarded as the first grand attempts of nature to estab- lish insectivorous, carnivorous, and herbivorous groups, or unguiculates and ungulates. The ancestors or centers of these adaptive radiations date far back in the Age of Reptiles. At the beginning of the Eocene we find the lines all separated from each other but not as yet very highly special- ized. The specialization and divergence of these archaic mammals con- ———_——- THE EOCENE OF EUROPE AND NORTH AMERICA 97 tinue through the Eocene Period and reach a climax near the top, although many branches of this archaic stock become extinct in the Lower Eocene. The orders which may be provisionally placed in this archaic group are the following: Marsupialia. Multituberculata, Plagiaulacide. Placentalia. Insectivora. Insectivores not as yet positively identified in the Basal Eocene. Teniodonta. Edentates with enamel teeth. Creodonta. Archaic families of carnivores. Condylarthra. Primitive light-limbed cursorial ungulates. Amblypoda. Archaic, typically heavy-limbed, slow-moving ungulates. This group is full of analogies, but is without ancestral affinities to the higher placentals and marsupials. There are forms imitating in one or more features the modern Tasmanian ‘ wolf’ (Thylacinus), the bears, cats, hyzenas, civets, and rodents of to-day, but no true members of the orders Primates, Rodentia, Carnivora, Perissodactyla, Artiodactyla have been discovered. A remarkably interesting paleeogeographic fact is the presence of many similar if not actually related mammals in South America in the Upper Cretaceous or Basal Eocene Notostylops Zone of Patagonia. Since other members of this archaic fauna of North America are positively and widely represented in the Basal Eocene of Europe, we have abundant proof of that striking faunal community or widespread distribution of similar forms of mammalian life in the latter part of the Age of Reptiles which has already been referred to (p. 95). I. THE BASAL EOCENE LIFE OF EUROPE AND AMERICA There is little doubt that the extinction of the large terrestrial and aquatic reptiles, which survived to the very close of the Cretaceous, pre- pared the way for the evolution of the mammals. Nature began afresh with the small, unspecialized members of the warm-blooded quadrupedal Class to slowly build up out of the mammal stock the great animals which were again to dominate land and sea. One of the most dramatic moments in the life history of the world is the extinction of the reptilian dynasties, which occurred with apparent suddenness at the close of the Cretaceous, the very last chapter in the “Age of Reptiles.” Close of the Age of Reptiles and Beginning of the Age of Mammals We are fortunate witnesses of these great events as they followed each other at two widely distant points, namely on the northern coast of France and Belgium, and in the heart of the Rocky Mountain region in Wyoming and northern Montana. H 98 THE AGE OF MAMMALS Toward the close of the Age of Reptiles, in late Cretaceous times, sea and land still possessed a large reptilian fauna; the great marine ich- thyosaurs and plesiosaurs had previously become extinct, but the giant sea lizards, or mosasaurs, still survived. In Belgium, the very summit of the Cretaceous, the Danian or Me- strichtian Stage,’ a name given to the exposures around Mestricht, records the existence in the seas of several mosasaurs, namely, the huge Mosa- saurus giganteus and the lesser Platecarpus, as well as of great marine turtles. On land there wandered the tall herbivorous dinosaurs known as Iguano- dontia (Orthomerus dolloi Seeley) and their enemies, the carnivorous dinosaurs (Megalosaurus bredai Seeley). At the same time in the Rocky Mountain region, where the land ani- mals only are known, there existed several kinds of dinosaurs. Chief among the herbivorous forms were the giant Iguanodontia (T'vrachodon) or “duckbill”’ dinosaurs, the great paired-horned Ceratopsia (Triceratops), and the armored ankylosaurs (Ankylosaurus). All these herbivorous forms were subject to attack by the giant carnivorous megalosaurs of the genus Tyrannosaurus. 'There were also smaller dinosaurs (Ornithomimus), cur- sorial, or of swift-running habit. These reptiles were in the climax of specialization and grandeur; they moved amidst a stately flora of palms and sequoias interspersed with bananas and fig trees, and a very rich de- ciduous tree flora of modern south temperate type. A great many species of small mammals are known in these Upper Cretaceous dinosaur beds of the Rocky Mountain region. They are with- out exception of small size, and as compared with the reptiles, they are humble and inconspicuous forms. We have no conception as to what worldwide cause occurred, whether there was a sudden or a gradual change of conditions at the close of the Cretaceous; we can only observe that the worldwide effect was the same: the giant reptiles both of sea and land disappeared. Reptiles are so sen- sitive to temperature that it is natural to attribute this extinction to a general lowering of temperature, or refrigeration, but the flora shows no evidence of this either in Europe or America; nor is there evidence of any great geographic cataclysm on the surface of the earth, for the plant life transition from one Age to the other in the Rocky Mountain region is alto- gether gradual and gentle. Among the successive stages and formations in which this momentous change from Age to Age is recorded are the following: 1 According to De Lapparent, Danian and Meestrichtian are not synonymous; the Mse- strichtian, forming a part of the Aturian (or Upper Senonian), is earlier than the Danian. THE EOCENE OF EUROPE AND NORTH AMERICA 99 Rocky Mountains Belgium. France 3. Lower Eocene, = 3. Upper Landenian = 3. Sparnacian WASATCH Age of Mammals; 2. Basal Eocene, = 2. Lower Landenian = 2. Upper Thanetian TORREJON (Cernaysian) 1. Lower Thanetian 1. Basal Eocene, Fort UNIon, PurERCO Age of Reptiles 1. Upper Creta- = Danian, Mestrich- ceous, LARAMIE tian First, it will be observed that the Upper Cretaceous LARAMIE of America is broadly regarded as of age equivalent with the DANIAN or MasTRICHTIAN of Europe, also that both are characterized by a rich reptilian fauna, mark- ing the close of the Age of Reptiles. Lying at the base of the Eocene or dawn of the Age of Mammals in America are the Fort Union or great lignitic formation of Wyoming and Montana, and the Puerco of New Mexico; the latter is partly a tuff for- mation. These are both continental deposits which are regarded as of the same age as those sea border, or fluvio-marine deposits in northern Europe, which are placed in the Lower Thanetian stage. We thus enjoy a contemporaneous picture of mammalian life as it existed along the northern coasts of France and Belgium and in the river valleys, flood plains, and lake borders of the newly born Rocky Moun- tain region of New Mexico and Montana. For it must be remembered (p. 93) that this region too had not long previously been on the borders of an inland sea. Seashore transition beds in Europe. — The very ancient Basal Eocene formations of Europe are along the sea borders and are thus not favor- able to the preservation of mammalian life; yet the rocks are full of interest as serving to illustrate how an ancient encroaching seashore may record both its own life and that of the land near by. An especially clear sequence of these transition deposits is that recently de- scribed by Depéret ! in northern France near Rheims. (1) Immediately overlying the Cretaceous are the Sables blancs siliceux de Rilly, white seashore sands of variable thickness containing many marine molluses which are similar to those in the Sables de Bracheux, another Basal Eocene formation. (2) The overlying Gravier marin de Cernay, or seashore gravels of Cernay (erroneously called ‘Conglomérat’ de Cernay by Lemoine), containing species of typical marine molluses characteristic of the Upper Thanetian (Pectwnculus, Ostrea, Lucina), is also a marine or shore formation, rich in the teeth of sharks. The remains of mammals represent those carried into the borders of a shallow sea through river currents; they are iden- 1 Depéret, Relations stratigraphiques des Faunes des Cernay et de Meudon au Mont de Berru. Soc. Géol. France, Ser. 4, Vol. VI, 1906, pp. 442-443. 100 THE AGE OF MAMMALS tical in age with the mammals of the celebrated fauna of Cernay, which contains the marsupial multituberculate, Neoplagiaulax. As the coast was rising, this deposit was overlaid by (3) a bed of coarse sands, clays, and lignites, which represents the beginning of the Sparnacian, of a thickness of 17 m.; near this level were found the bones of the giant bird Gastornis, described by Lemoine. The coast was still rising, so that superposed (4) is a lagoon or lacustrine formation of marls and lime- stones without fossils. Superposed again are the (5) Sables et argiles ligniteuses with a brackish water molluscan fauna of Sparnacian age; in these sands and clay- lignites (21 m. above the Gravier marin de Cernay), have been found limb bones of Coryphodon identical in size with the typical specimen found at Meudon (Marnes de Meudon). These records of a sinking and rising Basal Eocene shore line near Rheims are paralleled by the Lower Landenian, a Basal Eocene marine phase of Belgium, probably of the same age as the Cernaysian of Rheims. (1) This marine littoral formation contains no mammals, but a number of very characteristic reptiles, as follows: the large lizard Champsosaurus lemoinei, of the same species as that found near Rheims in the typical Cernaysian, abundantly represented and beautifully preserved; Lytoloma, a marine, shore-living turtle with a very powerful mandib- ular symphysis, evidently adapted to crushing the littoral molluses; the giant bird Gastornis has also been found here. (2) Surely resting on the Lower Landenian is a fluviatile formation attributed to the Upper Landenian stage, and represented at Orsmael and Erquelinnes, localities in Belgium widely separated geographically but containing the same fauna, the genera being provisionally identified as follows: Coryphodon, Phenacodus, Dissacus, Hyenodictis, Decticadapis, Plesiadapis, also a most important member of the Perissodactyla-Equidx, provisionally identified as Pachynolophus maldani. It appears from this evidence that the Upper Landenian of Orsmael and Erquelinnes, containing Coryphodon and a true perissodactyl, is of more recent age than the Upper Thanetian or Cernaysian, and should be correlated with the lower Sparnacian of France, or the Wasatch of North America. Continental transition beds in America. — The gentle transition from the reptilian to the mammalian Age is far more simply shown in the suc- cession of continental depositions in northern Montana. The passage from the Laramie (Hell Creek beds) to the Fort Union, or Lignitic beds, is apparently continuous. The indications are that the late Cretaceous Laramie was a period of open country traversed by sand-bearing rivers. In the succeeding Basal Eocene, or Fort Union, there is evidence that large parts of Montana, Wyoming, Colorado, and the Dakotas were covered with dense coal- or lignite-forming forests. Vast stretches of subtropical and more hardy trees were interspersed with swamps where the vegeta- tion was rank and accumulated rapidly enough to form great beds of lignite. Here were bogs in which bog iron was formed. Amid the glades of these forests there wandered swamp turtles, alligators, and large lizards of the characteristic genus Champsosaurus. Plant remains in the Laramie Hell Creek beds have also been found in the Fort Union at various locali- ties; types common to the Upper Cretaceous and Basal Eocene formations are the fig (Ficus), banana (Musophyllwm), palms similar to the sabal of THE EOCENE OF EUROPE AND NORTH AMERICA 101 Florida (Flabellaria sabalites), horse-tail rushes (Hquisetum), the soapberry (Sapindus), the hardy sequoias (Sequoia) and gingkos (Gingko), also the oak (Quercus), and sycamore (Platanus). The existence of this continuous similar flora, as determined by Knowlton,’ through the transition from the MAMMALS 7 / Ww : fort Union molluscs, plants Eoatolarede 2 z Claenodon Oo = ° Zz <—fort Union plants ul S) ; mit a a Mamma! Quarry Ptilodus < Gils : LG OSes © ra Claenodon <——fort Union plants Mioc/senus ai <—‘Ceratops Beds” molluscs ia : Cw 5 Fort Union plants om “wo E — Fort Unior plants sO 2p ax a ks < a 5 ~\<- Ceratops Beds’ molluscs DINOSAURS aij : 2 L Triceratops j ey ivingston" plants Trachodon <— Marine and brackish invertebrates CRETACEOUS A ? FOX HILLS “ ; 7 Ft. Prerre’ invertebrate fauna Fic. 25.— Age of Mammals succeeding the Age of Reptiles. Columnar section to the northeast of the Crazy Mountains, Montana, showing the Fort Union mammal beds (Basal Eocene), overlying the ‘“‘ Ceratops Beds’ (Upper Cretaceous). Data of Stone and Stanton, 1910. Age of Reptiles into the Age of Mammals, is strong evidence that the cause of the extinction of the Reptilia is not to be sought in a change of flora or in a lowering of temperature. A typical Basal Eocene mammalian fauna containing the marsupial Plagiaulacide is found as described below (p. 111). ' Knowlton, F. H., Notes on a Few Fossil Plants from the Fort Union Group of Mon- tana, with Description of One New Species. Proc. U.S. Nat. Mus., Vol. XVI, 1893, pp. 33-36; also, The Tertiary Floras of the Yellowstone National Park. Amer. Jour. Sci., Vol. II, 1896, pp. 51-58. Knowlton and Stanton, Stratigraphy and Paleontology of the Laramie and Related Formations in Wyoming. Bull. Geol. Soc. Amer., Vol. VIII, 1897, pp. 127-156. ‘ 102 THE AGE OF MAMMALS I. BASAL EOCENE, FIRST FAUNAL PHASE—MAMMALS SOLELY OF THE ARCHAIC TYPE COMMON TO THE NEW AND OLD WORLDS Animals of the First Faunal Zone. —The Basal Eocene life zones in both countries are sharply characterized by the extinction or absence of the giant reptiles, by the survival from the Cretaceous of the large swamp Fic. 26.— Basal and Lower Eocene. Thanetian, Cernaysian, Lower Landenian. FRANCE. — Glauconie de 1 la Fére (Aisne), fluvio-marine deposits (6 meters). Gravier marin de 2 Cernay, near Reims (.5-7 meters). Sables et calcaires de 3 Rilly, near Reims, lacustrine. Sables de 4 Chdlons-sur-Marne (Marne). Sparnacian, Upper Landenian. BELGIUM. 5 Erquelinnes, near French boundary. FRANCE. — Argile plastique et lignites de 6 Soissons (Aisne), 7 Guny, 8 Muirancourt, near Paris. 9 Saron, near Ste. Maxence. 10 Laon (Aisne). 11 Upper Cernay, near Reims. Conglomérat de 12 Meudon, near Paris. Lignites de. 18 Vaugirard, near Paris. Travertin de 14 Sézanne (Marne), a calcareous tuff rich in plants. ENGLAND.— Woolwich and Reading Beds, “ plastic clay,” of 15 Dulwich, 16 Croyden, near London, marine and estuarine (4-28 meters) sands and clays. Lower Ypresian. ENGLAND.—17 London clay of 18 Herne Bay (Kent), 19 Kyson, north of Har- wich, 20 Harwich (Essex), 21 Isle of Sheppey, mouth of the Thames, marine and estuarine deposit (over 500 feet maximum). _FRANCE.— Marine deposits of 22 Pourcy, near Reims. Upper Ypresian. FRANCE.—In Marne, near Epernay : 22 Chavot, sables 4 terédines d’ Ay, marine (3-4 meters), marnes de Cuis. Correlation of Depéret. or fluviatile lizard Champsosaurus (of the order Choristodera or long- snouted Rhynchocephalia). In the Rocky Mountain region this animal is also found in the underlying Laramie formation. Its survival both in the Rocky Mountain region, in Belgium, and in France is one of the most distinctive features of the Basal Eocene, because it is apparently on the verge of extinction and does not reappear in higher levels. THE EOCENE OF EUROPE AND NORTH AMERICA 103 This Basal Eocene stage is further distinguished by the presence of numerous diprotodont marsupial multituberculates of the family Plagiaula- cide, and by many other very primitive mammals. It is also distinguished by the absence of any mammals belonging to modernized families. These first make their appearance on both con- tinents in the Lower Eocene (Wasatch) in what is known as the Coryphodon Zone, probably equivalent to the Upper Landenian of Belgium or the Sparnacian of France. The chief distinction of this mammal fauna is that it represents a survival of the mammalian life of the Age of Reptiles, and so far as we know it now this life is all of the archaic type. We are, in fact, witnessing the close of a faunal phase which opened well back in Cretaceous times. BasaLt Eocene or EuROPE Thanetian Formation. — The Basal Eocene of Europe is known as the Thanetian Stage; it is named after the Isle, or promontory, of ‘Thanet, at the mouth of the Thames. As above described on p. 99, it is divided into inferior and superior levels. In France it is typified by the fluvio-marine glau- conie de la Feére, from which the single famous bear-like creodont Arctocyon primevus was described in 1841. With the superior level (Upper Thane- tian) is paralleled the fluvio-marine gravel deposit of Cernay, near Rheims, from which the famous ‘‘fauna of Cernay”’ was described by Lemoine.! CHARACTERISTIC _ This very rich Cernaysian or Upper Thanetian Mammats- —_ fauna is nearly of the same age as the Torrejon fauna Plagiaulacids of northern New Mexico; that is, its age is a little Adapisoricids more recent than the underlying true Puerco fauna of Lemuroids (?) New Mexico. It contains small insectivores, lemur- Insectivores, (?) like mammals, a few hoofed mammals, and many car- or Condylarths (?) nivores. It is especially interesting to compare the Arctocyonids teeth of Neoplagiaulax (Cernaysian) with those of Oxycleenids Ptilodus (Torrejon) as in a similar stage of evolution; Triisodonts these are small, gnawing, diprotodont marsupials, which may be descended from Plagiaulax of the Upper Jurassic. The Insectivora are represented by members of the family Adapisoricidz, somewhat analogous to the tree shrews (T'upaia). Primitive monkeys, possibly lemuroids, are represented by small animals referred to the Plesiadapidee. More doubtful is the identification of the teeth of the herbivorous tuberculate pattern with that of one of the primitive cursorial ungulates (Huprotogonia) of the hoofed order Con- dylarthra of the Torrejon. Pleuraspidotheriwm somewhat resembles Meniscotherium, the primitive ungulate or condylarth of more recent 1See Lemoine, various papers listed in Bibliography. 104 THE AGE OF MAMMALS geological age in the Rocky Mountains; it may as well be an insectivore. The comparison of the primitive carnivores or Creodonta in the two countries is closer, namely, of the Thanetian species of Arctocyon, with its omnivorous, bear- or raccoon-like teeth, with those of Clenodon of northern New Mexico. Similarly the Thanetian Procynictis parallels Chriacus of the American family Oxyclenide, and Hyenodictis is similar to the American Dissacus of the Mesonychide. Contrary to the recent opinion of Depéret, it does not appear probable that the presence is demonstrated of any of the modernized animals, e.g. artiodactyl or perissodactyl un- gulates, in this imperfectly known fauna. Similarly we note the absence of, or have thus far failed to discover in this fauna any relatives of the Edentata (Tzeniodonta) or Amblypoda,’ both characteristic of the Torrejon. Of course the Cernaysian river deposit presents a very incomplete picture of the mammalian life of France during this period, for as observed by Lemoine and Depéret these mammal remains were only those which were washed into streams and carried to the sea near by. The associated freshwater fishes of northern France and Belgium are related to the garpikes (Lepidosteus) and bow-fins (Amia), now met with only in the great rivers of North America. There are many turtles, all marsh and river varieties, Crocodilia, both of the crocodile, or Nile type, and the long-snouted, gavial type, of the Ganges. Extremely adapted to aquatic life is the rhynchocephalian lizard Simedosaurus, related to the Champsosaurus of the Basal Eocene of North America. The flightless bird Gastornis, belonging to the order of Chenomorphe, according to von Zittel,’ is remarkable for its huge proportions and its powerful legs in con- trast with its feeble wings. The flora of this Basal Eocene period indicates a moderately warm and temperate climate free from great extremes, including palms (Flabellaria), laurels (Laurus), cinnamons (Cinnamomum), and a doubtfully referred grass (Poacites).2 In the extreme north the Basal Eocene flora’ of Greenland, Iceland, and Spitzbergen included lindens, alders, magnolias, poplars, and birches, indicating a temperature similar to that of south temperate France or California at the present time. BasAL EocENE OF NortH AMERICA Puerco and Torrejon Formations. —In northwestern New Mexico, at the head of the Puerco River on the divide between the Rio Grande and San Juan rivers, are the Basal Eocene, post-Cretaceous beds which Pro- 1 As above noted (p. 100), the inclusion in this stage of mammals found in the Upper Landenian of Orsmael and Erquelinnes, namely, Amblypoda (Coryphodon) and _ Perisso- dactyla (primitive Equidz) is extremely doubtful. °Von Zittel, Text-Book of Paleontology, transl. by Eastman, Vol. II, 1902. 3 De Lapparent, Traité de Géologie, 1906, p. 1492. 4 Tbid., p. 1504, citation from Heer’s Flora fossilis arctica. eee eEEEeeEEeEEEEeEeEeEEEeEeeEeEeEeEEeEeEeE—EE——E THE EOCENE OF EUROPE AND NORTH AMERICA 105 fessor Cope described as ‘Puerco marls” in 1875, and from which he listed the first mammalian fauna in 1881.* The formation overlies the Upper Cretaceous (Laramie) and underlies the Wasatch (Sparnacian, Ypresian). In 1895 Wortman observed a natural subdivision of the formation into Lower or Puerco proper, and Upper or Torrejon, estimating the combined thickness at 800 to 1,000 feet.* In 1897 Matthew * separated the fauna of PROBABLY WASATCH TORREJON BEDS Fic. 27.— Badlands of northern New Mexico, head of Torrejon River. Basal Eocene, Torrejon-Pantolambda Zone below. Lower Eocene, Wasatch-Coryphodon Zone above. From photograph by American Museum of Natural History, 1896. the two levels, adopting Wortman’s proposed designation Torrejon for the upper beds, which are nearly of Upper Thanetian or Cernaysian age. As distinguished by its mammalian life this division is as follows: Uprrer: Torreson Formation (300 feet), zone of Pantolambda, the earliest known member of the Ungulata-Amblypoda, with crescentic teeth, ancestral to Coryphodon. Lower: Puerco Formation (500 feet), zone of Polymastodon. In 1901 Douglass discovered in the Fort Union or great lignite forma- tion of the upper Missouri River in northern Montana, a bed of shale con- 1 Cope, E. D., Report on the Geology of Northwestern New Mexico, Examined During 1874, Append. LL, Ann. Rept. Chief Eng., Washington, 1875. 2 Cope, E. D., On Some Mammalia of the Lowest Eocene Beds of New Mexico. Proc. Amer. Philos. Soc., Vol. XIX, 1881, pp. 484-495. 3 Osborn, H. F., and Earle, Chas., Fossil Mammals of the Puerco Beds. Collection of 1892. Bull. Amer. Mus. Nat. Hist., Vol. VII, Art. i, Feb., 1895. 4 Matthew, W. D., A Revision of the Puerco Fauna. Bull. Amer. Mus. Nat. Hist., Vol. LX, 1897, pp. 259-323. 106 THE AGE OF MAMMALS taining a mammalian fauna of Torrejon age, including especially the con- dylarth Huprotogonia and the amblypod Pantolambda.' Reptilian fauna.— Abundant remains of three different species of Champsosaurus, the large, aquatic lizard with a gavial-like snout, have been found in the Puerco. This animal (p. 100) occurs also in the Lower Eocene of France (vicinity of Rheims) and of Belgium. From the Puerco has been obtained also the earliest known North American serpent (Hela- gris prisciformis), un- specialized in character and of about the size oi the common black snake (Bascanium con- strictor). Puerco Life of the New Mexico Region Neoplagiaulax or Polymastodon Zone. — This is the earliest known of the Eocene mammal groups, im- mediately succeeding the Cretaceous, and preceding in age the Torrejon and Cernay- sian. In New Mexico and Montana are found these small archaic mammals evolving from ancestors of the Age of Reptiles. Two of the genera date, in family ancestry (Plagi- aulacide), as far back Fic. 28.—Skull of the Basal Eocene plagiaulacid Ptilodus aS the Upper Triassic oe: In the U.S. National Museum, Washington. After op Rheetic, namely: of ey. the diminutive multi- tuberculates, (1) Neoplagiaulax, which represents a decided advance upon Ptilodus of the Upper Cretaceous (Laramie), and (2) Polymastodon, which similarly is much more modern than Meniscoéssus of the Laramie. The latter animal is as large as a beaver (Castor). In general these mammals were the marsupial rodents of the Mesozoic period. 1 Douglass, E., The Discovery of Torrejon Mammals in Montana. Science, n.s., Vol. XV, 1902, pp. 272-273. THE EOCENE OF EUROPE AND NORTH AMERICA 107 Two orders of archaic hoofed mammals, or ungulates, are known here, namely: (1) the Amblypoda, or short-footed forms, represented by the bunodont Periptychidee, which receive their name from the sculptured sides of the grinding teeth of the type genus Periptychus. This family embraces a number of large and small herbivorous mammals, all with a peculiar triangular asymmetry in their superior molar teeth, of consider- able range in size, probably in part arboreal in habit. (2) The light-limbed ungulates, or Condylarthra, are doubtfully represented by one genus (Protogonodon) of the family Phenacodontidee. The gnawing or leaf-eating Herbivora of the order Tzeniodonta are represented by two families, Sty- linodontidze and Conoryctide. This order is also known as Ganodonta (yavos, enamel, ddovs, tooth), a name assigned by Wortman when he demonstrated that certain descendants of these mammals present many resemblances to the gravigrade South American edentates, although dis- tinguished by the persistence of dental enamel, which has disappeared in all the true Edentata. Of doubtful affinity to the Insectivora are the two genera Mioclenus and Oxyacodon. The primitive carnivores, or Creodonta, of this phase have been discovered only in part. They include two families (Triisodontidie, Oxyclenide), represented by five genera. By Wortman the Oxycleenidze were regarded as Insectivora. It is noteworthy that not a single representative ancestor of any exist- ang order of mammals is certainly recognized in this assemblage. The possible exceptions are the supposed representatives of the Edentata and Insectivora, beth very ancient orders. The opinion of Cope that the an- cestry of modernized mammals was to be sought in these Puerco forms therefore lacks direct confirmation. The opposite opinion that the Puerco- Torrejon mammals are not ancestral to the modern mammals was developed by Osborn (1893-1904),! when he applied to them the name Meseutheria, indicative of their archaic or Mesozoic character. Negatively, therefore, the Puerco is distinguished by the absence of recognizable primates, rodents, carnivores, and of any modern families of insectivores, artiodactyls, and perissodactyls. A summary of the Puerco mammalian fauna is as follows: Genera Species Archaic mammals of Triassic ancestry, Marsupialia Dipro- todontia 4 5 Archaic mammals of Cretaceous ancestry 15 24 Mammals of modern affinity 0 0 Torrejon Life of the New Mexico and Montana Regions Pantolambda Zone. — All the Mammalia of the Torrejon phase, or Pan- tolambda zone were found about three hundred feet above those of the 1 Osborn, Rise of the Mammalia in North America, 1893; and Ten Years’ Progress in Mammalian Paleontology, 1904. See Bibliography. 108 THE AGE OF MAMMALS Puerco phase, and thus represent a very long interval of geologic time. They are of somewhat larger size, considerably more varied, and in the presence of one new family (Miacidve, genus Didymictis) more modern. The diprotodont multituberculates, including the diminutive Neoplagiaulax and Ptilodus, and the much larger Polymastodon, still occur in this zone. Gidley ' has recently made the most important discovery that the animal called Chirox by Cope? is actually the same as Ptilodus or Neoplagiaulax; that is, it represents the superior dentition; a beautifully preserved skull Fig. 29. — Archaic hoofed mammals of the Pantolambda Zone. Outline restorations to same scale (X 73). A. Meniscotherium, a condylarth. (See also Fig. 39.) B. Pantolambda, an amblypod, short-footed, semi-plantigrade. C. Huprotogonia, a condylarth, long- and slender-limbed. and part of the skeleton of Ptilodus found in the Fort Union of Montana demonstrates beyond question that this animal, and consequently all the multituberculates, are true marsupials, aberrant diprotodonts, as was originally surmised by Owen®* in describing Plagiaulax from the Upper Jurassic. The chief peculiarity is that (Fig. 28) the upper and lower teeth are fundamentally different in numbers and in arrangement and do not oppose each other. Gidley is inclined to consider these animals as frugivorous, the incisors being well fitted for picking small fruits or berries. The previous view has been that they were gnawing types analogous to the rodents. It is important to note that these are the very last survivors of this very ancient family of plagiaulacids (Plagiaulacide). As compared with the Puerco, the faunal summary is as follows: Genera Species Archaic multituberculates, Marsupialia Diprotodontia ZI 4 Archaic or primitive mammals of Cretaceous ancestry 20 37 Modern, or possibly related to the modern Carnivora 1 1 1 Gidley, J. W. Notes on the Fossil Mammalian Genus Ptilodus, with Descriptions of New Species. Proc. U.S. Nat. Mus., Vol. XXXVI, June 19, 1909, pp. 611-626, Pl. 70. 2 Cope, E. D., Proc. Amer. Philos. Soc., Vol. X XI, 1883, p. 321. 3 Owen, R., Monograph of the Fossil Mammalia of the Mesozoic Formations. Mon. Pal. Soc., 1871. EE oer THE EOCENE OF EUROPE AND NORTH AMERICA 109 Thus the archaic forms predominate in the ratio of forty-one species of archaic to one species of modern affinities. This rich fauna is believed to be of the same age as that of a portion of the Fort Union of Montana, as described by Douglass’ (1902) and Farr. Its approximate parallels in Europe (Upper Thanetian or Cernaysian) are indicated by the common presence in France and North America of somewhat similar stages of evolu- tion among the representatives of three or four families, namely: (1) Pla- giaulacide, (2) Arctocyonide, (3) Mesonychide-Triisodontine, (4) Oxy- clenide. As noted above, other identifications of the Torrejon and Cernaysian faunas are somewhat uncertain. As in the Puerco, these Torrejon mammals belong almost exclusively to an older radiation, destined to become extinct during the Eocene. This elimination, in fact, begins at once, because five out of the fourteen families of mammals discovered in the Torrejon make their last appearance at this stage. The remark applied by Dr. Lemoine to the Cernaysian fauna, “Comme c’est dréle, ce monde la,” certainly applies with equal force to the Torrejon world; it was certainly strange and bizarre, none the less ex- tremely interesting and fortunately much more completely known than the Puerco assemblage, because the limbs and feet of several of its mem- bers have been discovered. It was the happy finding of the fore foot of Psittacotherium which led Wortman * to the demonstration that this member of the family Stylinodon- tide, as well as the animal known as Conoryctes of the order Tzeniodonta (Ganodonta), are strongly analogous if not actually related to the South American gravigrade Edentata, such as Megalonyx, and the armadillos, respectively. These browsing or leaf-eating tzeniodonts now attain a considerable size, and present a direct passage between the Wortmania (‘“Hemiganus’’) of the Puerco and the Calamodon of the Wasatch or Sparnacian. There are still no true rodents. Beside the Mioclznidse (Mioclenus) and Panto- lestidze (Pentacodon) there are the Mixodectide, making their first appearance with a pair of greatly enlarged incisor teeth, which suggested to Cope their affinity with the Chiromys, or Aye-Aye, of Madagascar, and to Osborn their possible relationship to the Rodentia (Order Proglires). These small insectivore, rodent, or lemur-like forms are destined to survive to the summit of the Eocene. It is noteworthy how frequently diprotodonty, or the enlargement of a front pair of incisor teeth, appears not only in the marsupial suborder ‘ Diproto- dontia,’ but as a parallel or analogous adaptation in these Basal Eocene mam- mals of Europe and America, and in the several families of other orders. 1 Douglass, E., A Cretaceous and Lower Tertiary Section in South-Central Montana. Proc. Amer. Philos. Soc., Vol. LXI, 1902, pp. 207-224. *Wortman, J. L., The Ganodonta and their Relationship to the Edentata. Bull. Amer. Mus. Nat. Hist., Vol. LX, 1897, pp. 59-110. 110 THE AGE OF MAMMALS Of the archaic ungulates, the light-limbed Condylarthra are now cer- tainly represented by two genera of Phenacodontidse (Tetraclenodon, Eu- protogonia), the former reported both from New Mexico and Montana. Of the slow-moving Amblypoda the bunodont Periptychide are still repre- sented by four genera, and the selenodont Pantolambdide, which are con- sidered more nearly ancestral to the coryphodonts of the Wasatch, make their first appearance. The genus Pantolambda, including animals rang- Fic. 30.— Basal and Lower Eocene stages in the evolution of the heavy-limbed Ambly- poda. Above: Skeletons of the small Pantolambda and its large successor Coryphodon. Below: Restorations of the same by Charles R. Knight. Both in the American Museum of Natural History. ing in size from that of a large beaver to that of a sheep, receives its name from the lambda shape of the cusps of its superior grinding teeth; out of these simple cusps were destined to arise the extraordinary yoke- shaped teeth of Coryphodon and the still stranger crested teeth of Uinta- therium. The primitive skull, short limbs with everted elbows, the short, spreading feet and long tail of this animal, all point toward ancestry from an unguiculate or clawed animal of the primitive carnivore-creodont build. THE EOCENE OF EUROPE AND NORTH AMERICA BBs It should be noted that there are no lemurs or other primates certainly recognized in this fauna. Several of the animals which were regarded as lemuroid by Cepe are now placed near the insectivores (Matthew, 1909). PREVAILING The ancient Carnivora (Creodonta) are either richer MAMMALS or more fully known in this phase than in the Puerco, Plagiaulacids since they are represented by four families, Arcto- Periptychids eyonide (Clanodon), Mesonychide (Dissacus), Triiso- Pantolambdids dontidee (Sarcothraustes), Oxyclenide (Chriacus, Tri- Phenacodonts centes, Deltatherium). These creodonts are partly Teeniodonts provided with tubercular teeth, partly with sub- Mixodectids trenchant or cutting teeth. It is important to observe Insectivores (?) Pro-Carnivores (or Creodonts) * that no well-developed sectorial teeth have as yet evolved in this phase; in other words, the Creodonta are not yet perfected as flesh eaters. Triisodonts The first rudiments of modernism are seen in the Oxycleenids genus Didymictis, a member of the family Miacide, Arctocyonids which may be considered one of the true pro-Carnivora because in the disposition of its carnassial or sectorial teeth it agrees with dog-like and civet-like forms of the higher Wasatch and Bridger Formations. II. THE LOWER EOCENE LIFE OF EUROPE AND AMERICA We now enter the life or faunal zone of Coryphodon, the bulky succes- sor of Pantolambda, an animal known both in Europe and North America; also of Hyracotherium and Eohippus, the first representatives of the horses (Equide). Depéret (see p. 100) was of the opinion (1905) that Cory- phodon and Hyracotherium appear earlier in Europe than in America, namely, in the Lower Landenian of Belgium, which he synchronizes with the Cernaysian' or Thanetian; the evidence for this correlation does not appear conclusive. It is quite possible, however, that both Coryphodon and the primitive horses may be found at an earlier geological phase in the Old than in the New World. In whichever continent the coryphodons and horses did originate, there is no doubt as to the occurrence of a sudden modernization, through the appearance both in Europe and North America of an assemblage of mammals, unheralded by ancestral forms, which in- cludes ancestors of four or five modern orders and embraces eleven new families, two of which persist to the present time and none of which have been observed in the Torrejon or Puerco phases. We are thus in another of the great successive faunal phases, namely, the Second, as follows: 1 Depéret, C., L’évolution des Mammiféres tertiaires; importance des migrations (Kocéne). C. R. Acad. Sci. Paris, Vol. CXLI, séa. Nov. 6, 1905, p. 702. 112 THE AGE OF MAMMALS IT. LOWER EOCENE, SECOND FAUNAL PHASE — FIRST MODERNI- ZATION IN EUROPE AND AMERICA, OR INVASION OF ANCESTORS OF MODERN MAMMALS WHICH MINGLE AND COMPETE WITH ARCHAIC. CLOSE FAUNAL CONNECTION BETWEEN WESTERN EUROPE AND WESTERN NORTH AMERICA. APPARENT BREAK BETWEEN NORTH AND SOUTH AMERICA. INITIAL ELIMINATION OF ARCHAIC IN COMPETITION WITH MODERN MAMMALS. European paleontologists have usually attributed the source of the modern families of the Second Faunal Phase to North America; while this theory is without evidence, it is certain that this fauna originated neither in South America nor in Africa. There remain four possible centers of Fic. 31.— Coryphodonts, typical, large mammals of the Lower Eocene. To the left a coryphodon bull with large tusks ; to the right a cow, with small tusks. After the original by Charles R. Knight in the American Museum of Natural History. * origin, namely: (1) the Great Plains and Atlantic Border region of North America; (2) the more northerly American Mountain Region, that is, British Columbia; (3) the northerly American-Asiatic land mass or northern Holarctica; (4) the northerly Eurasiatic region or northern Palzearctica. Each of these regions was sufficiently large and varied to give origin to a diversified modern fauna, but in the writer’s judgment the nearly simul- taneous appearance in western Europe (latitude 50°), and in North America (latitude 40°), favors the fourth hypothesis, namely, that these mammals had been previously developing in the northerly portion of Holarctica, or in the North-American-Asiatic land mass. There was certainly such a THE EOCENE OF EUROPE AND NORTH AMERICA rs great land mass to the north, of warm to temperate climate favorable to the evolution of these higher forms of mammalian life; in fact, there is every reason to believe that this northerly region was throughout the whole pre-Pleistocene Cenozoic period highly favorable to the evolution and migration of the higher forms of the Mammalia. This, as seen in a north-polar view of the earth, was the area of the great migrating routes and must have enjoyed a favorable climate, otherwise the faunal con- tinuity between Europe and western America could not have been so fre- quently renewed or sustained by intermigration. As detailed on p. 66, this hypothesis of a northerly or circumpolar center has been advocated by. Wortman and others. It must be remembered, however, that the actual center from which these modernized mammals suddenly spread into Europe and North America is still hypothetical and will not be determined until the Basal Eocene fossil mammal beds in the unknown portions of America and Asia shall have been discovered. Placing in contrast the archaic and modern orders in North America during the Second Faunal Phase, they appear somewhat as follows: Archaic Orders Modern Orders Creodonta, creodonts Carnivora, fissipede carnivores Insectivora, insectivores Rodentia, rodents Tillodontia, tillodonts Perissodactyla, odd-toed ungulates Teeniodonta, ganodonts Artiodactyla, even-toed ungulates Condylarthra, phenacodonts Primates, lemuroids or monkeys Amblypoda, coryphodonts As noted above, the division is very arbitrary; the archaic or modern columns will be swollen or diminished by the respective transfer of the primitive Insectivora to the modern column, or of the primitive Lemuroidea to the archaic column. Lower Eocene LIFE oF EUROPE As compared with that of America the Lower Eocene of Europe is more precisely subdivided at the present time by Depéret'! and others through the alternation of marine and terrestrial formations, upon which the European paleontologist relies, while his American confréres are de- pendent entirely upon the freshwater phases of the Rocky Mountain basins. After it has been possible to make very close comparisons between the evolution stages of a large number of related mammals on the two continents, closer correlations may be made than are at present prac- ticable. It is therefore best to treat Europe and America separately, first noting the broad parallelism of stages, as follows: 1 Depéret, L’évolution des Mammiféres tertiaires, etc. (Eocéne), 1905. I 114 THE AGE OF MAMMALS Europe North America Upper Ypresian Lower Bridger Huerfano (Upper) Lower Ypresian Wind River, Coryphodon Zone Upper Wasatch ” “4 Huerfano (Lower) ” 4s Sparnacian Lower Wasatch, Coryphodon Zone Sparnacian Life, Coryphodon Zone Sparnacian formations. — The Sparnacian Stage is broadly parallel with the Lower Wasatch of America; it receives its name from Epernay (Latin, Sparnacum). As shown in localities 6-16 of the accom- panying map (Fig. 26), the chief formations representing this stage are along the old Suessonian coastline of northern France and southeastern Eng- land, formerly near the shore- line of the ancient North Sea, which is known geologically as the Suessonian Sea. The open Thanetian sea of the preceding phase is now succeeded by lagoons and estuaries, favor- able to the formation of plastic clays and lignites. The typical Fic, 32.— France in Lower Eocene, or Ypresian F ; ‘ times. After de Lapparent, 1906. -White =land. deposits, argiles plastiques et Ruled lines = sea. The modern river courses, as Le ae : 1 indicated, differ totally from those of Eocene times. lignites de Sotssons* of lacus trine origin (6), are paralleled by the fluviatile Conglomérat de Meudon (12), near Paris, by the Sables et argiles ligniteuses, near Cernay (described above on p. 100), and by the Travertin de Sézanne (14) and the Woolwich and Reading Beds. The last two (15) apparently both yield a rich representation of the flora of the period. De Lapparent describes the Sparnacian as a period of fluvio- marine deposition, the region of Paris being occupied by a lagoon, while farther south were lakes. The lacustrine Travertin de Sézanne (a calcareous tuff), near the present site of Paris, includes the sassafras and other large trees of the laurel family, lindens and magnolias.” Similarly in the Woolwich Beds of southeastern 1The town, Sozssons, is in Dept. Aisne, northeast of Paris. 2 De Lapparent, Traité de Géologie, 1906, p. 1495. THE EOCENE OF EUROPE AND NORTH AMERICA ila es) England are found locusts (Fobinia), figs (Ficus), tulip trees (Liriodendron), and Grevillea, a proteaceous plant now confined to Australia.' The marine and estuarine plastic clays of this formation also contain remains of Cro- codilus and of the giant bird Gastornis. PREVAILING The remains of mammals are very scarce. In the MAMMALS Soissons deposits (6) are found three very important and Coryphodonts distinctive forms, namely, the two heavy-bodied ungulate Hyracotheres coryphodons C. eocenus, C. oweni, the former described in (Horses) 1846 by Owen, the latter by Hébert ten years later. An Lophiodonts — equally significant form from the Lignites de Soissons is Palzonictids the odd-toed or perissodactyl ungulate Lophiodon larteti, which Filhol regarded as the ancestor of the true heavy- bodied lophiodonts.2, Among the carnivorous mammals is the creodont Paleonictis gigantea (from Muirancourt, Oise, 8), a member of the Pale- onictide, a family of cat-like, short-faced creodonts, which also appear for the first time in the Wasatch of the Rocky Mountains (Palwonictis occiden- talis). In the Soissonais of Europe has also been found a large mesonychid creodont, Pachyena boulei. Both at Meudon and in the upper deposits near Cernay are found the bones of Coryphodon oweni. This sparsely known mammalian fauna of Europe has its complete counterpart in the Rocky Mountain region. From the Upper Cernay deposits near Rheims (see p. 100) (sables et argiles ligniteuses) is also recorded a femur (length .390) of Coryphodon oweni Hébert identical in size with the typical specimen found at Meudon. Ypresian Life Lower Ypresian formations. —The Ypresian stage is named from Ypres, Flanders. It is typified by the famous estuarine formation of the London Clay (166 m.), which is also the type of the Etage Londinien of Mayer- Eymar, a formation containing several important primitive mammals and marine molluscs, which prove that this is on a higher level than the Sparna- cian. Exposures are at Herne Bay, Kent (18), Kyson (19), Harwich, Essex (20). Of the same age are the plant deposits of the Isle of Sheppey (21), near the mouth of the Thames, and the marine deposits of Pourey (22) near Rheims. (See map, p. 102). The mammals of the London Clay include the amblypod Coryphodon eocenus, also a small mammal Platycherops (= Miolophus), an animal often compared with but certainly not related to the tillodont Hsthonyx of the Rocky Mountain region; it is of the size of the marten (Mustela) and of ‘Gardner, British Eocene Flora, Palwont. Soc., p. 29, quoted by A. Geikie in A Text- Book of Geology, London, 1893. ? Depéret, C., Les Transformations du Monde animal (Paris, 1907), traces the evolu- tion of the four phyla of lophiodonts from the Upper Ypresian stage (pp. 206-208). 116 THE AGE OF MAMMALS uncertain relationships. The carnivore Argillotherium (Davies, 1884) is also indeterminate. Horses. — Fortunately the primitive four-toed horses (Equid) are represented by several highly characteristic specimens of the genus Hyra- cotherium (=Plolophus). The great English anatomist Owen! described 7 these specimens (H. PRL, Srr—apeen leporinum and H. cuni- culus), but quite natu- rally failed to recognize their ancestral relation- ships to the horses. The type (1. leporinum) exhibits simple grinding teeth (Fig. 2) which are similar to those of Eohippus borealis of the Fie. 33.— Skull of the primitive Eocene horse Hyracothe- Wasatch and Wind rium (Pliolophus) vulpiceps of the London Clay (X 3). After Owen. River Formations of the Rocky Mountains, but the second superior premolar tooth is a very simple, two-rooted, single- cusped tooth, whereas in all the American equines the same tooth is more complex, namely, invariably three-rooted and three-cusped, or with two external cusps and an internal ledge. This London Clay type of Fia. 34.— Models of the Lower Eocene, primitive horse of North America, Hohippus. After originals by Charles R. Knight in the American Museum of Natural History. Hyracotherium, therefore, is the most primitive horse certainly known, and bespeaks the very early entrance of the horses into Europe. #H. vul- piceps, or the ‘fox-headed’ hyracothere, also from the London Clay (see 1 Owen, R., Trans. Geol. Soc., Vol. VI, 1839 (1841), p. 203, and Ann. Nat. Hist., Vol. VIII (1841), 1842, p. 1. THE EOCENE OF EUROPE AND NORTH AMERICA 1h Fig. 33), is a somewhat more progressive horse, and is similar in its stage of evolution to the Hohippus validus of the Rocky Mountain region, which has the simplest fourth superior premolar of any of the American hyracotheres. We note especially the swelling brain case of these little horses (Fig. 33), indicative of a comparatively well-developed cerebrum. This London Clay phase is evidently of the Coryphodon Zone, broadly corresponding with the Wasatch, but possibly a shade older. Fortunately our knowledge of the contemporary fish, reptile, and bird life is quite extensive. The fishes of the London Clay include rays (Mylio- batis), sharks (Odontaspis, Lamna), sun-fishes (Tetrapterus), and saw- fishes (Pristis). Among the reptiles are marine and freshwater turtles and tortoises (Chelone, Trionyx, Platemys), two species of crocodile, and a sea-snake (Palwophis) of large size. Among the birds are Steganopodes, allies of the pelicans and cormorants; Dasyornis, also, a giant bird pos- sibly allied to Gastornis, has been discovered.! Of still greater interest is the rich land flora preserved in the Isle of Sheppey deposits near the mouth of the Thames.* This gives by far the best picture we have both of the environment and temperature of the most remote period of the horse. We find palms (Nipa, Sabal, Chame- rops), conifers (Sequoia, Pinus, Callitris, now of Africa), the plantain (Musa), now confined to eastern Asia, the eucalyptus (Hucalyptus), now characteristic of Australia, the tupelo (Nyssa) now exclusively North American. There are also oaks, laurels, sweet gums (Liquidambar), mag- nolias, almonds (Amygdalus), and soapberries (Sapindus), altogether a flora south temperate rather than subtropical. CHARACTERISTIC Upper Ypresian Formations. — While the Lower MAMMALS Ypresian is in the Coryphodon Zone and_ corresponds in age with the American Wasatch and Lower Wind Dichobunids River depositions or close of the Lower Eocene, the (Artiodactyls) | Upper Ypresian lacks Coryphodon and contains a more Hyracotheres recent fauna which, as Depéret observes, approximates (Horses) it more closely to the Middle Eocene. It thus perhaps Lophiodonts corresponds to the Upper Huerfano and base of the Insectivores Bridger Formations of the Rocky Mountain region. The (?) Lemurs typical stage is locally known as the Sables a Teredina (?) Mesonychids _personata, especially exposed in northern France near Epernay, at Chavot (22), a marine formation, at Ay (22), and at Cuis. These are the Sables agéiens of Lemoine. These Teredo sands contain the faune agéienne of Lemoine, which partly 'Geikie, A., Text-Book of Geology, 1893, p. 973; and Boyd Dawkins, Early Man in Britain, 1880, p. 19. 2 J. S. Gardner’s British Eocene Flora (Paleont. Soc., p. 12), as quoted by A. Geikie, 1893, p. 973. 118 THE AGE OF MAMMALS includes a continuation of the old mammals of the Upper Thanetian (Cer- naysian), and partly a number of mammals now recorded or observed for the first time. Among the former is the insectivore Adapisoriculus, pos- sibly related to Adapisorex of the Cernaysian, Plesiadapis, which resembles Mivxodectes of the American Torrejon in its diprotodont dentition. The skull and skeletal characters do not agree well with those of modern insec- tivores, nor are they distinctively primate (Matthew). Protoadapis also appears, and like Plesiadapis is of doubtful primate reference; it has been classed with the Rodentia, or may be placed with Mixodectes among the Proglires. Creodonts are represented by Hycnodictis, allied to the mesony- chids in tooth structure; the rodents by Decticadapis and Plesiarctomys. The odd-toed Ungulata are represented by two out of four great branches or phyla of the Lophiodontide which are destined to play a great part in the Eocene mammal life, namely, by the more robust form Lophiodon remense (of about the size of a tapir and ancestral to the great L. lautricense of the Upper Eocene) and by Chasmotherium, a small lophiodont lacking the third lobe of the last lower molar (ancestral to the C. cartieri of the Upper Eocene). These chasmotheres are of small size, the premolar teeth rapidly complicating; they tend to be short-headed, or brachycephalic, the teeth finally forming a closed series. The other phylum parallels the more robust lophiodons and survives until the close of the Middle Eocene. Depéret considers the ‘ Propachynolophus’ gaudryi (Lemoine) of these beds as a member of the Equide, but in the present writer’s opinion the ad- vanced condition of its grinding teeth, its considerable size, the presence of a mesostyle in the grinding teeth above and of a metastylid below ap- péar to liken it rather to a primitive palothere (?Plagiolophus). The smaller Propachynolophus maldani (the type of this species and genus), however, may be truly a hyracothere, or primitive horse. The Artio- dactyla are now for the first time represented by the small pro-ruminant form Protodichobune. Altogether the affinities of these animals await solution by much further study and comparison. In deposits alleged to be of Upper Ypresian age in southeastern Europe (Transylvania) are found the remains of a large quadruped (Brachydias- tematherium) related to the American family of titanotheres (see p. 556). This animal is in an Upper Eocene stage of evolution comparable to that of the American Protitanotheriu:n (p. 169). It thus appears probable that these deposits are much more recent than Lower Eocene. Lower Eocenr, WasAtcH AND WIND River Lire or NortH AMERICA The Lower Eocene of North America is the great Coryphodon Zone ; it is represented by a grand fauna known from thirty-eight years of exploration in formations which are broadly known as “Wasatch,” this THE EOCENE OF EUROPE AND NORTH AMERICA 119 being the name first applied by Hayden’ to a group of beds of this age near Evanston, western Wyoming. This Evanston ‘Wasatch’ represents the earliest phase (corresponding with the Sparnacian and Lower Ypresian of Europe), a more recent phase of the same fauna being contained in the Wind River Formation of central Wyoming. The animals which tie these vastly extended deposits together are Coryphodon, Eohippus (the earliest type of American horse), Phenacodus, and Palwonictis. In the Wind River (corresponding with the Upper Ypresian of Europe), Bathyopsis, a new member of the Order Amblypoda appears. The contrast which the life of the Coryphodon Zone of the Wasatch and Wind River exhibits to the very archaic and chiefly Mesozoic fauna of the underlying and:-earliest Torrejon and Puerco formations (p. 111) ren- ders this one of the most striking of modernizations in the whole American Cenozoic. The archaic and modern mammals are in these North American Spar- nacian and Lower Ypresian beds thoroughly mingled; the former still pre- dominate in the number of genera and species; they also predominate in size, Coryphodon and Phenacodus and the carnivorous creodonts being the largest mammals of the period. The mammals belonging to the modernized orders are inferior in size and in number of species, but prove to be mechanically superior both in their foot and tooth structure, and of higher intelligence. The summary of this mingled fauna is as follows: Summary of Wasatch Genera and Species Genera Species Multituberculate marsupials (Plagiaulacide) 0 0 Placental mammals of archaic type 18 48 Placental mammals with modern affinities | 33 In this calculation the Insectivora are included among the archaic forms, the Primates, or Lemuroidea, among the modern. Naturally a sharp line cannot be drawn between orders, and the above table only repre- sents the momentous change in a broad way. As compared with the summaries on pp. 107-8, the contrast is sufficiently striking. Formations of the Coryphodon Zone. — Phase I. As shown in the accom- panying map, the chief exposures in the central Rocky Mountain region are as follows: (1) the typical ‘Wasatch’ group of Hayden, or more re- strictedly the ‘Knight Formation’ of Veatch, 1,750 feet; (2) the Wasatch of the Black Buttes (= Bitter Creek of Powell, = Vermillion Creek of King, 1878), in the Washakie Basin, Wyoming; (8) the ‘Wasatch’ of the 1 Hayden, F. V., Geological Report of the Exploration of the Yellowstone and Missouri Rivers, by KF. V. Hayden, assistant to Col. William F. Raynolds, U.S. Engineers, Washing- ton, 1869. 120 THE AGE OF MAMMALS ss, = Yj Uy WYfy us ty Uy ’ ss wre bole By permission of the U.S. Geological Survey. Fic. 35.— Heart of the ancient Eocene flood plain and lake region of Wyoming, showing the areas of Eocene deposition which have resisted erosion. Lower Eocene: Wasatch (oblique lines); Wind River (horizontal lines); Green River (vertical lines). Middle Eocene: Bridger and Washakie (horizontal lines). Upper Eocene: Uinta (horizontal lines). THE EOCENE OF EUROPE AND NORTH AMERICA 12 Fe] Zz uJ 1S) [2) iw WwW aay] Qa 2 = LJ vod rf) ee === Oo SK NIG hapa Types of Eohippus index ° 5 ee Cope, OME 4 ~vassaciensis = uw 4 Phenacodus primaevus ee eS ee w = Coryphodon radians uJ Ue 4 ~~ semicinctus z red. begs Nght » laticeps eS UNCONFORMITY=——— Voleanic ash or SS white beds GROUP OF HAYDEN p= — FOWKES= == == H —— TYPICAL WASATC id red.and yellow.= andy-< ed ° oy ore - - ° je ‘oe CASe atte OG O's 6.97 OOO. - Oe BASAL EOCENE ? ee = Plants characteristic F of Denver formation 79) a = eat =) > 2 rg a = Oo ‘ < c ul Plants and Ls a = invertebrates af & of Montana 5) (Oh < =a = age By permission of the U.S. Geological Survey. Fig. 36.— Scale section of the Lower and Middle Eocene of southwestern Wyoming, showing the relations of the “typical Wasatch group” of Hayden (4); Modified from Veatch, 1907. 22 THE AGE OF MAMMALS San Juan Basin of northern New Mexico, 1,500 feet, overlying the Torrejon and Puerco series; (4) the ‘Wasatch’ of the Big Horn of Wyoming, 2,391 feet (Loomis). Phase II. (1) The lower portion of the Huerfano Formation near Spanish Peaks, Colorado. The Wind River Formation (Hayden) of northern Wyoming, 500 feet. These formations all contain Coryphodon and Eohippus, and may be‘ col- lectively known as Lowrr Eocene. Below them were either mammalif- Fic. 37.—In the heart of the Lower Eocene badlands on Gray Bull River, Big Horn Basin, Wyo. Wasatch Formation. Zone of Coryphodon, primitive horses, tapirs, etc. Photo- graph by American Museum of Natural History, 1896. erous beds of undoubted Basal Eocene age (Puerco and Torrejon) or de- posits of equivalent age (e.g. Fowkes, Almy, Fig. 36, p. 119) resting on the Upper Cretaceous. The fact of paramount interest is the great thickness of these Lower Eocene depositions, amounting in western Wyoming to 4,000 or 5,000 feet. For the beds which intervene between this Coryph- odon Zone and the summit of the Cretaceous, the thickness indicates an enormous period of time, ample even for the transformation of the diminutive ancestors of Pantolambda into the bulky Coryphodon (Figs. 30 and 31). The materials of which these various deposits of the Coryphodon Zone a ee SS eee THE EOCENE OF EUROPE AND NORTH AMERICA L235 were composed are partly indicated in the petrographic analysis of Johann- sen.’ 0 Ip | B) Ib fe) fay °. | WI est Ne | S| All sai O| ! | | Hl Faramys Coryphodon (rare) Lambdotherium primaevum Phenacodus Eohippus cristatus Heptodon —-— Lambdothertum “WIND RIVER’ J 335 SUPPER TATMAN MOUNTAIN LEVE! Coryphodon zore Pelycodus Oxyaena Anacoadon Eohippus (very abundant) Systemodon Coryphodon (veryabunaant) Sinopa Trigono/estes Hyopsodus Al We a Sarco/emur : Esthonyx Falaeictops Faramys LOWER TATMAN MOUNTAIN LEVEL— LOWER EOCENE OF THE BIG HORN BASIN "WASATCH’ Fic. 38.— Composite columnar section of the Wasatch and Wind River formations of Big om Pee compiled from sections by F. B. Loomis. See section A, Fig. 35. Total thickness ; eet. Wyoming in Wasatch times. — A glance at Fig. 35 enables us to restore two of these great basins, the Wasatch lying south of parallel 42° 1 Johannsen, Albert, Petrographic Report on Rocks Collected by Professor H. F. Osborn, U.S. Geol. Surv. In Ms. 124 THE AGE OF MAMMALS and the Big Horn traversed by parallel 44°, east of the Wasatch and west of the Big Horn ranges respectively, both vast flood plain and lacustrine basins surrounded by low mountain ranges. It is significant that at Evan- ston in the Big Horn (Fig. 36) and in the Wind River (Fig. 38) the mammals are found chiefly in or near the so-called “Red Beds.” These beds may be an indication of the prolonged exposure of these sediments to the air, or of erosion from the reddish rocks of the Trias. The basins were formerly considered great lake-basins, but the river, flood plain, and lagoon theory now prevails. Loomis (1907)! carefully analyzed the entire mammalian fauna of the Coryphodon Zone with reference to its bearing on the physio- graphic conditions in these old mountain ranges. He shows that, judging by the apparent adaptations to various modes of life, the total known species of the vertebrate fauna are divided as follows: aerial 3 per cent, cursorial, terrestrial, and arboreal 75 per cent, amphibious 12 per cent, aquatic 10 per cent. We may imagine that this small percentage of species of truly aquatic animals, such as crocodiles, fishes, and turtles, mingled their remains with those of the prevailing land animals by becoming stranded or inclosed in lagoons far from the rivers. The bones of terrestrial animals may have been exposed on the sunny flats. The light-limbed horse Kohippus, probably typical of a plains or partly open country, alone makes up 32 per cent of the total collections. All the other perissodactyl or odd-toed ungulates were light-limbed, including the lophiodonts (Heptodon), primi- tive titanotheres (Lambdotherium), the surviving archaic condylarths (Phe- nacodus). The feet of all these animals indicate dry rather than swampy ground conditions, because they are more slender than those of the modern tapir. On the other hand, the coryphodons were certainly marshy-land dwellers, and perhaps partly amphibious, or stream dwellers, although this is far from demonstrated. The presence of rivers of considerable size is indicated by the large lepidostean fishes, or garpikes (Clastes), and by the river-living turtles (Trionyz). Wasatch Life of the Wyoming and New Mexico Region Surviving archaic mammals. — Taken altogether, the prevailing resem- blances of this older fauna of the Coryphodon Zone are with the mammals found in the Sparnacian and Lower Ypresian of Europe, but far closer com- parisons are necessary than any which have been made hitherto. Of the smaller Herbivora, no signs of the Plagiaulacidze or any other marsupials have been discovered; opossums (Didelphyidse) were probably living in the forests of this region, however. Of the condylarth ungulates, Phenacodus is the most famous. The discovery by Wortman?’ of the ' Loomis, Origin of the Wasatch Deposits. Amer. Jour. Sci., May, 1907, Ser. 4, Vol. XXIII, pp. 356-364. 2See Cope, E. D., The Vertebrata of the Tertiary Formations of the West. Rept. U.S. Geol. Surv. Terr., Vol. III, 1883 (1884), Pl. LVII and text. = * — THE EOCENE OF EUROPE AND NORTH AMERICA ies, complete skeleton of P. primevus with its five digits on the fore and hind feet and its primitive bunodont teeth was welcomed as realizing the proto- type or atavus of the Ungulata; but more profound study has revealed that this extremely small-brained (Fig. 40), long-tailed animal, replete with archaic unguiculate characters, is not the ancestor of a new and vigorous stock, but the survivor of a dying-out stock. Like its am- blypod contemporaries, the Wind River species, P. wortmanit was less abundant and of dimin- ished size. A contem- porary condylarth of Fic. 39. —Skeleton of the Lower Eocene coudylarth Men i- th ti f scotherium terrerubre. In the American Museum of Natural € proportions of a History. (N.B. The scapula is only partially restored.) modern hyrax is Menis- cotherium (Fig. 39), with its very complex bunolopho-selenodont grinding teeth and reduced cropping teeth. The heavy-limbed Amblypoda of the period include several species of Coryphodon, attaining the proportions of small rhinoceroses, with crested grinding teeth and defensive canine tusks. These animals were termed Pantodonta by Cope, in reference to the complete series of upper and lower incisors. They have a rather feebly developed chest and musculature of the lumbar region, abbreviated tail, short, clumsy feet, and may have been partly amphibious in habit. The skull marks a great advance upon that of the ancestral Pantolambda, and rudiments of the posterior pair of osseous horns, characteristic of the succeeding genus Uintatherium, are observed. Anew order (Tillodontia) of gnawing diprotodont phytophagous placentals is heralded in species of Esthonyx, in which one pair of the incisor teeth is beginning to enlarge at the expense of the others, prophetic of the fully di- protodont Tvllotherium of the Middle Eocene. The supposed aberrant Edentata of the order Tzeniodonta, or Ganodonta, succeeding the Torrejon Stylinodontide, are now represented by the still more progressive Cala- modon, with a deep-set pair of anterior teeth and still more reduced enamel on the grinding teeth. The tendency of these herbivorous forms to become diprotodont, or enlarge a pair of front teeth, is thus manifested independently in two orders. The Insectivora are now represented by three and perhaps four families, namely, the pantolestids (Palwosinopa), believed to be long- tailed aquatic forms analogous to the potamogalids of modern Africa; the leptictids (Palwictops), probably terrestrial forms of the size of the hedgehog (Hrinaceus); the hyopsodontids (Hyopsodus), with teeth like those of Hohippus on a miniature scale, animals which were long regarded 126 THE AGE OF MAMMALS as Lemuroidea, but are now transferred to the Insectivora on skeletal char- acters. There are other small forms (Diacodon, Didelphodus) which are of uncertain affinity. Preying upon these insectivorous and herbivorous forms are members of five families of the carnivorous Creodonta, including Fig. 40.— Lower Eocene light-limbed condylarths, or phenacodonts, showing arched back and long tail. Above: The skeleton of Phenacodus primevus (Cope’s famous type). Below: Restoration by Charles R. Knight. Both in the American Museum of Natural History. specialized Arctocyonide with flattened tubercular teeth (Anacodon), which make their last appearance. The giant carnivores or omnivores of the period are the mesonychids of the genus Pachyena, descended from the Torrejon Dissacus, with blunt, rounded cusps adapted to devouring decaying flesh. In wide contrast are the palzonictids (or oxyzenids) represented by Pale- THE EOCENE OF EUROPE AND NORTH AMERICA 127 onictis, of the size of a puma (Felis concolor), with sectorial teeth, short face and jaws. Another branch of oxyzenids includes animals of smaller size (Oxyena) with sharp and effective sectorials. Of the CHARACTERISTIC size of the modern civets (Viverra) are several species MaMMALs of Sinopa, adapted to the quest of birds and small Coryphodonts mammals. Of great zodgeographic interest is the sim- Phenacodonts ultaneous distribution of three of these families (Palz- Meniscotheres onictide, Mesonychide, Hyzenodontidz) in the Lower Tillodonts Eocene of France. Teniodonts Progressive or modernized mammals. — Contrasting with Insectivores these archaic, smali, aberrant carnivores, are the mem- Arctocyonids bers of the family Miacide, including Didymictis, sur- Mesonychids viving from the Torrejon, besides a great variety of small Palseonictids related carnivores (Viverravus, Miacis, Uintacyon, Vul- Oxyeenids pavus), all distinguished by the fact that the carnassial Hyzenodontids teeth are the same as those in the modern Carnivora, Lemuroids namely, the fourth upper premolar and first lower molar. Rodents Evidently these small true pro-carnivores were begin- Dichobunoids ning to sharply compete for their prey with the small (Artiodactyls) | creodonts, although the larger creodonts (Paleonictis, Lophiodonts Pachyena) were alone capable of attacking animals of -Hyracotheres the size of Coryphodon and Phenacodus. The primates are now certainly recognized for the first time. Sur- prisingly modern is the Tarsius-like Anaptomorphus, a short-faced, large- eyed, aberrant form, with teeth analogous to those in the existing tarsier (Tarsius) of Madagascar, that is, not distinctly lemuroid. An insectivore of the diprotedont type or with an enlarged pair of lower front teeth is Cynodontomys, ancestral to the Microsyopide of the Bridger, and with some analogies to the Mixodectide of the Torrejon and the Plesiadapide of the Cernaysian. Among the herbivorous ungulates the greatest interest centers in the appearance of two families of even-toed or artiodactyl forms, the Trigonolestide, diminutive forms (Trigonolestes) with a typical artiodactyl astragalus, perhaps related to the Dichobunidse (Protodicho- bune) of the Upper Ypresian. Of more doubtful affinity are the sup- posedly pig-like achsenodonts, represented by Parahyus, quite an un- certain reference. Of equal moment is the sudden appearance of three families of Ungulata-Perissodactyla, namely, the horses (Equidz), tapirs (Tapiridz), lophiodonts (Lophiodontidz). The lophiodonts are represented by the excessively slender-limbed and narrow-footed Heptodon, analogous in size only to the Chasmotherium of the Ypresian of France, but distin- guished by dolichocephaly. Known in America only, at this stage, are the tapirs (Systemodon), animals somewhat exceeding the modern foxes (Vulpes) in size. Still more numerous and characteristic, as well as diversified, are the horses, including eleven species which have been discovered in the 128 THE AGE OF MAMMALS different exposures of the Wasatch, all animals of the size of small foxes, eraceful, light-limbed, and like their European contemporaries (Hyraco- therium), large-brained. Close comparison (cf. p. 116) of these hyracotheres with those of the Lower Ypresian (London Clay) of the northern coast of Europe shows that the grinding teeth are in a very similar stage of evolution. The species Hohippus validus, on the whole the most ancient in type of the American hyracotheres, is in exactly the same state of evolu- tion as the H. vulpiceps of the London Clay; but nothing in America is known quite so ancient as the H. leporinum of the London Clay in respect to the simplicity of the anterior premolar teeth. A modern aspect is also given to this fauna by the appearance of the Rodentia (Paramys, Sciuravus) of the family Ischyromyide, embracing a number of species sug- gesting in their tooth structure the sciuro- morphs, or squirrel eroup of rodents. It appears probable that some of these ischy- romyids were destined to give rise to the true sciurids or squirrels. Wind River Life of Wyoming and Colorado Geological conditions and distribution. — In their grand sequence the Wind River sedi- ments and their geologic parallels in Wyoming and Colorado take up the life story of the i] Wasatch and continue = ef kee) it into the beginning of the Bridger deposition, which we regard as Fic. 41.— Map showing location of the Wasatch (oblique lines) and Wind River (horizontal lines) of the Big Horn region true Middle Eocene. of Wyoming. The typical forma- tion lies at the head waters of the Big Horn River (Fig. 41), northeast of the Wind River Mountains, 400 to 500 feet in thickness, irregularly disposed with an east and west extent of 100 miles and north and south extent of forty miles. By permission of the U.S. Geological Survey. ES THE EOCENE OF EUROPE AND NORTH AMERICA 129 It is readily distinguished geologically (Fig. 43) by horizontal alternating bands of gray and bright red fossil-bearing rocks. These red bands contain most of the fossils, and some are of considerable horizontal extent. The basin has been explored successively by Hayden (1859, 1869), by Wortman for Cope (1880) and the American Museum of Natural History (1891, 1896), by Loomis for Amherst College (1904), and by Granger (1905, 1909) for the American Museum. To the latter we are indebted for the first accurate survey of the geology and of the life succession in this basin as here set forth. All previous accounts are incorrect, first, in attributing too great thickness to the Wind River deposits, second, in failure to connect them properly with the underlying Wasatch. The sequence of the Wind River life zone to that of the Wasatch is clearly indicated in the Tatman Mountain section (Fig. 38) at the summit of the Big Horn Wasatch deposition (Fig. 41) to the north; here we clearly pass from the Wasatch into Wind River times. While these formations were being deposited in Wyoming there was accu- mulating in southeastern Colorado the base of the Huerfano Formation, discovered by Hills? in 1888 and explored by Osborn*® and Wortman in 1896. The basin lies immediately north of the famous twin volcanoes known as Spanish Peaks, and the Huerfano deposits are most probably tuffs, or of volcanic dust origin. The fossils apparently occur in a single stratum not exceeding ten or fifteen feet in thickness and not more than thirty or forty feet from the base of the formation. They include the remains of ten genera and of several species characteristic of the Wind River deposits. While the lower Huerfano levels are of Wind River age, the upper levels are dis- tinctively of Middle Eocene, or Bridger age. The Wind River life has thus been found in three chief localities: Wind River of Wyoming, 500 feet. Tatman Mountain, upper levels of ‘Big Horn Wasatch’ of Wy O- ming, 300 feet. Huerfano of southeastern Colorado, 800 feet, including ‘Bridger’ levels. Geographic conditions. — Loomis (1907) has rightly regarded the Wind River Formation as of fluviatile and flood plain origin. The wide horizontal extent of the red bands is attributable to prolonged or repeated periods of flooding; the red color is less probably due to aridity or other atmos- pheric causes than to erosion from the Triassic rocks. Besides a great variety of mammals, the ‘red beds’ contain turtles (Trionyx), crocodiles (Crocodilus), and lizards of the family of Anguide (Glyptosaurus). The 1See also forthcoming Bull. Amer. Mus. Nat. Hist., by Walter Granger. 2 Hills, R. C., Recently Discovered Tertiary Beds of the Huerfano Basin, Denver, 1888. 3 Osborn, The Huerfano Lake Basin, Southern Colorado, and its Wind River and Bridger Fauna. Bull. Amer. Mus. Nat. Hist., Vol. LX, 1897, pp. 247-258. K 130 THE AGE OF MAMMALS intermediate grayish ‘shales,’ as well as the coarse conglomerate beds formed by rapid stream action of river invasions, are barren. Even in the ‘red beds’ fossils are scarce except in one or two very limited areas, and as a rule fragmentary and imperfectly preserved. The only complete skeleton recorded is the type of the famous Hohippus venticolus, Fic. 42.— The Lower Eocene banded layers of the Wind River Badlands, basin of the Wind River, Wyo. Zone of Lambdotherium and of the last stages of Coryphodon. Photo- graph by American Museum of Natural History, 1896. found by Wortman in 1880. It has required years of the most arduous search, concluding with the ‘microscoping’ of the beds by the American Museum party of 1909, to round out materials for our knowledge of this, including the discovery of the skulls of two of the most characteristic forms. Faunal life. —With the Wind River we enter a NEWLY new life zone, signalized by the earliest record of a ARRIVING new and very important family of perissodactyls, the MAMMALS titanotheres, which is represented by the genus Lamb- Titanotheres dotherium from which the zone takes its name. Lambdotherium Accompanying this small, light-limbed and very Eotitanops abundant titanothere is the larger titanothere known Hyracodonts as Hotitanops, a form truly ancestral to the great Hyrachyus titanotheres of Eocene and Oligocene times. There Uintatheres are many other newly arriving mammals, including Bathyopsis twelve new genera and fifty-five species, which have Primates not been found in the Wasatch. Nine of these new Notharctus genera of mammals are also found in the Bridger. Washakius Wind River life is thus transitional and prophetic of Microsyops Bridger life. The Wind River, however, represents THE EOCENE OF EUROPE AND NORTH AMERICA 131 Carnivores truly the closing chapter of the Lower Eocene, because Oéddectes there is remarkably little extinction, there being Patriofelis rather a numerical diminution of the mammals so Limnocyon highly characteristic of the Lower Eocene. In all, Tritemnodon the Wind River possesses twenty-five genera in com- Edentates mon with the Wasatch. It possesses eleven Wasatch Stylinodon species. It is doubtful whether a single family of mammals becomes extinct. Lambdotherium fotitanops Coryphodon Bathyopsis Lambdo- Phenacodus thertum Meniscotherium Zore Ww a Lohippus a é = Heptodon 5) Sees = SSS Hyrachyus = = Red stratum Pelycodus a S ALKALI= CREEK (Fossils most x = numerous) Notharctus a ———— = 5 ee ———— Patriorelis af uw a £sthonyx [e) . EK | 400’ = to 600) >| ———_ ee n 1 ~ | © === eee ae W) a —— = |e x} s a ita Zz (e) wl =| - ates =) ie) a 6, Ww ; ale a | w O| > Oreodon | Cylindrodon WW Caénopus i= Ischyromys a Poébrotherium S Volcanic ash 5 “ Titanotherium zone is UNCONFORMITY : = << ———_—_—_———._. Diplacodor zone us Amynodon ° Frotoreodon 5 Camelid ?M. EOCENE BRIDGER e 5 L. EOCENE fe WAS. W. RIVER Coryphodon, Phenacodus, Lohippus of ? Coryphodon zone CRET. By permission of the American Museum of Natural History. Fic. 55.— Lower Eocene to Oligocene. A composite, continuous section in the Wind River Basin, Wyoming. After Granger, 1910. Compare Fig. 38. As above noted, the chief distinction from Europe is in the large pro- portion of surviving archaic Mammalia. Very noteworthy is the presence of an opossum (Peratherium) as indicating the continued residence of THE EOCENE OF EUROPE AND NORTH AMERICA 155 polyprotodont marsupials in this country. Among the Carnivora-Creo- donta, we find three families, the oxyzenids, hyzenodontids, and mesonychids, the last developing into animals of formidable size. The Insectivora are highly varied, including six families, four of which are now extinct, while two are doubtfully compared with the modern moles (Talpidze) and tenrecs (Centetide) as well as with the tupaiids or | ce 5 Anderson = Phetotso9, Fic. 56.—Skeleton of Uintatherium (mirabile), the amblypod successor of Pantolambda and Coryphodon. Uintatherium Zone, Upper Bridger. (See Fig. 58.) In the American Museum of Natural History. After Osborn. tree shrews. The peculiar herbivorous Tillodontia apparently become ex- tinct in Tillotherium of the Bridger. The archaic edentates with enameled teeth (Tzeniodonta) survive into the Lower Bridger only (Stylinodon). Of the archaic Ungulata the phenacodonts have all disappeared, but the amblypod stock is apparently flourishing and reappears in the imposing Uintatherium of the Middle Bridger. In the Middle Eocene the ratio of archaic and modernized genera and species of mammals is as follows: Grenera Species Archaic mammals 15 35 Modernized mammals 57 146 72 181 Thus there is for the first time a decided predominance of the modern- ized over the archaic forms. Among what we have been regarding as the more modern types, the arboreal primates now include two families (Anap- 156 THE AGE OF MAMMALS tomorphide, Notharctide), both surviving from the Lower Eocene. The pro-Carnivora (Miacidz) also survive from the Lower Eocene, and _ be- (CHARACTERISTIC MAMMALS Uintatheres Horses Tapirs Rhinoceroses Titanotheres Lophiodonts Entelodonts Homacodonts Oreodonts Camelids Teeniodonts Tillodonts Insectivores Lemuroids Armadillos come more diversified than in the Wind River, although most of the genera are modified Lower Eocene forms. The Rodentia still are limited to the rather generalized Ischyromyide, also surviving from the Lower Eocene and becoming diversified into six genera, which may prove to represent more than one family. At the very summit of the Eocene the American rodents known as jumping mice, or Dipodide, are doubtfully represented in the genus Protoptychus. Among the modern ungu- lates, as in Europe, this is ‘the grand epoch of the Peris- sodactyla. Of these, two families only (Equide and Lophiodontidz) have relatives in Europe. Of the re- maining families, the tapirs (Tapiride), titanotheres (Titanotheriidz), two families of rhinoceroses (Hyraco- dontide, Amynodontidz), cursorial, aquatic, or amphib- ious respectively, appear to be peculiar to North America. The even-toed ungulates, or Artiodactyla, are far less diversified than in Europe. They include the bunodont and omnivorous Achzenodontine (Achawnodon), related to the entelodonts Fic. 57. — In the heart of the Middle Eocene, Bridger Badlands of Wyoming, in the famous locality known as Grizzly Buttes. Zone of Orohippus and Paleosyops. Photograph by American Museum of Natural History, 1903. THE EOCENE OF EUROPE AND NORTH AMERICA 1b7 (see p. 217) or ‘giant pigs,’ which are destined to play a very imposing part in the Oligocene of North America and Europe. The diminutive selenodonts (Homacodon), provisionally referred to the European family of Dichobunide, may represent an independent family (Homacodontide). The most novel American forms, also destined to be conspicuous in the F 200’ |= ; ax 500 = NONFOSSILIFEROUS Very barren (a) x o x Wd UPPER WHITE LAVER oO Prato fk ee ee oH aa Uintatherium : (very abundant) if 375 Z ; 5 Mesatirhinus ts Uintathertum Manteoceras {e) uJ uJ =| fa) Cc F 2) 350 Bs = ale w E Of: Q pe a ee ee ee ee et a= ao}: Aye, Ie lae0syo, B ,| Fe Gayatinaa) 450 | wW oO a A 200’ By permission of the U.S. Geological Survey. Fic. 58.— Typical Middle Eocene of western Wyoming. Scale section of the Lower and Upper Bridger Formation. Prepared by Matthew and Granger, 1903. future history of the continent, are the oreodonts (Oreodontide) and the pro-camels (Camelidze or Hypertragulide). Geology of the Middle Eocene Bridger, Lower Washakie, and Lower Uinta _ Bridger. — These noble exposures in southwest Wyoming, discovered in 1869, are the classic hunting grounds of Leidy, Marsh, and Cope, famous 158 THE AGE OF MAMMALS for a rich fauna, and of late most accurately surveyed by the American Museum parties. Clarence King * believed that the Bridger and Washakie deposits (Fig. 35, p. 118) were formed in a great single or partly divided ‘Washakie Lake.’ This long accepted lacustrine theory has gradually given way before the arguments of Matthew’ and Davis* for the flood plain and fluviatile theory. It is definitely shown (Osborn, Granger) that the Washa- kie Formation began during the Upper Bridger, but continued on after the Bridger ceased. In both formations, as shown by the studies of Sinclair ‘ Fic. 59.— Middle Eocene of the Washakie Basin, Wyo., Haystack Mountain or ‘Mam- moth Buttes.’ Lower: top of Middle Eocene or Uintatherium Zone. Upper: base of Upper Eocene or Eobasileus Zone. Photograph by American Museum of Natural History, 1906. and the analyses of Johannsen, volcanic ash, ejecta, and erosion materials are important ingredients, so that we may imagine that in Bridger times this basin was surrounded by active volcanoes, as represented in Fig. 23, . which lent grandeur to the landscape. From his observations while col- lecting fossil turtles in the Bridger in 1903, Hay ° concluded that the Bridger deposits were almost solely the result of fluviatile and flood plain action, that this basin was a nearly level country, probably covered with vegeta- tion and well forested. The occurrence of fossil remains in all portions of the Bridger beds indicates that there existed no permanent sheet of 1 Clarence King, Systematic Geology, Washington, 1878, p. 458. 2 Matthew, W. D., Is the White River Tertiary an Eolian Formation? Amer. Natural., Vol. XX XIII, 1899, pp. 403-408. 3 Davis, W. M., The Fresh-water Tertiary Formations of the Rocky Mountain Region. Amer. Acad. Arts and Sci., Proc., Vol. XX XV, 1900, pp. 346-373. * Sinclair, W. J., Voleanic Ash in the Bridger Beds of Wyoming. Bull. Amer. Mus. Nat. Hist., no. 22, 1906, pp. 273-280. 5 Hay, O. P., The Fossil Turtles of the Bridger Basin. Amer. Geol., Vol. XXXV, June, 1905, pp. 327-329. : Ce ——— THE EOCENE OF EUROPE AND NORTH AMERICA 159 water. There can be little doubt that most of the animals lived near the places where they were buried. They are such forms as would be found in a well-wooded region. In the channel beds, composed of SUMMIT OF HAYSTACK MT £obasileus cornutus (Type skull) B EOBASILEUS ZONE Dolichorhinus hyognatnus (Skull Am. Mus. coll. 1906) Fobasileus Achaenodon Amynodon Dolichorhinus Es HEAD ee Metarhinus LEVEL OF ADOBE TOWN UPPERS EOCENE UPPER WASHAKIE Manteoceras washakiensis - (Type skull) ?U(Loxolophodon) speirianum (Type skull) UINTATHERIUM ZONE Uintatherium Manteoceras FT Mesatirhinus , fees SSE aa Notharctus = Hyrachyus = A Th died ee MIDDLE EOCENE LOWER BROWN SANDSTONE LOWER WASHAKIE NO FOSSILS SS Fic. 60.— Section (not in scale series) of Lower and Upper Washakie of central Wyoming, showing distribution of the principal types of mammals. Prepared by Granger, 1907. coarse materials, there is proof of streams with rapid currents traversing the basin, bordered by swamps in which were formed beds of lignite, or by freshwater bays in which the Unionide, or freshwater mussels, accu- mulated. While the coarse deposits indicate streams, finer deposits indi- 160 THE AGE OF MAMMALS cate mud beds, or shallow water conditions, in which the remains of uinta- theres and rhinoceroses are occasionally found as if they had been mired in a standing position (Hyrachyus has been found in this way). Occasion- ally, however, the entire region must have been flooded for long periods, because the careful researches of Granger and Matthew reveal the existence of successive ‘white layers’ (Fig. 58) of great horizontal extent, largely calcareous, or composed of shallow limestone containing shells (Goniobasis, Planorbis), as well as weatherworn jaws of small mammals. In their harder constituency these layers form the caps of the great benches or steppes which subdivide the grand Bridger Formation into successive layers, A—F. These hard layers also serve to mark off the Bridger into faunal levels. In general on the lower levels we find smaller mammals in lower stages of evolution, while on the higher levels we find larger mammals in a more advanced stage. There is thus a general progression and ad- vance of mammalian life from below upward, and secondly a gradual change in the character of the fauna, partly due to extinction and partly to invasion of the Bridger from the surrounding country. Washakie. —'The Washakie lies fifty miles east of the Bridger, a for- mation occupying an area of over 300 square miles, chiefly composed of volcanic material and subdivided into the Lower Washakie (Brown Beds, Uintatherium Zone, 260 feet in thickness) and Upper Washakie (Green and Gray Beds, Eobasileus Zone, 380 feet in thickness). First men- tioned by Hayden in 1869,! it is famous through the successive explora- tions of Cope, Marsh, Scott, Osborn, and finally of Granger,? who has solved its geologic and faunal characters. Fish and Reptile Fauna In the stream channels of the Bridger have been found remains of several species of bowfins (Amiidz) and garpikes (Lepidosteidz) as well as of catfishes or siluroids (hineastes). From the Lower Bridger are also described three species of snakes. The crocodiles were numerous and diversified, including Crocodilus as well as the diminutive Limnosaurus with laterally compressed teeth. Several species of Lacertilia (Glypto- saurus) have been described. All these partially known reptiles give us hints as to the Floridian or south temperate conditions of climate, and the great abundance of aquatic life. We may picture partly open, partly forested country, somewhat similar to the bayou region of the Mississippi Delta. More direct information is afforded from Dr. Hay’s monographic studies on the Testudinata.? We might expect to find here representa- ' Hayden, op. cit., 1869. ? Granger, W., Faunal Horizons of the Washakie Formation of Southern Wyoming. Bull. Amer. Mus. Nat. Hist., Vol. X XVI, no. 3, Jan. 19, 1909, pp. 13-23. 3 Hay, O. P., The Fossil Turtles of North America. Publ. Carnegie Inst., Washington, no. 75, 4to, 1908. THE EOCENE OF EUROPE AND NORTH AMERICA 161 tives of the characteristically South American order of side-necked or pleurodiran turtles, but such have not been found. The soft-shelled river turtles (Trionychoidea) were represented by at least two species, whereas there are at present in the whole world only twenty-six; the Bridger rivers and brooks fairly swarmed with these creatures, some of them equal in size to the largest existing Asiatic species. They are indicative of flowing waters. Swampy conditions are indicated by the presence of fourteen species of the family Emydide (order Cryptodira), as compared with the twelve species living in the Mississippi valley to-day. The genus Baptemys of the same order has its nearest relatives at present in Central America, while a third genus (Anosteira) is reported by Lydekker in the Upper Eocene of England. The presence of extensive stretches of land is indi- cated by the true land tortoises (Testudinide) of the genus Hadrianus, including giant tortoises nearly three feet in length, which probably lived on dry lands bordering the Bridger Basin. The ancient, Lower Cretaceous order Amphichelydia is also represented here by four species belonging to two genera. The Succession of Middle Eocene Mammals Lower Bridger or Orohippus Zone. —'The Lower Bridger includes levels A, B, C, of the section Fig. 58. It is characterized by the absence of the Amblypoda. It may be distinguished as the Orohippus Zone from the presence of these characteristic little ‘mountain horses.’ Many older Wasatch and Wind River species are found on this level which do not survive into the Upper Bridger. All the creodonts and pro- Carnivora are of older type. The Insectivora, Primates, and smaller Car- nivora are richly represented in the locality known as Grizzly Buttes. Here have been found among the monkeys, or lemurs, the Tarsius-like anaptomorphids, the notharctids, resembling some of the South Ameri- can monkeys, as well as remains of Microsyops with its rodent-like incisors, analogous to those of the aye-aye of Madagascar. There is also the long- tailed and probably aquatic insectivore Pantolestes, and numerous minute, shrew-like insectivores. Opossums (Peratherium) also occur. The primi- tive hyzenodonts Sinopa and Tritemnodon abound in these lower beds. Mesonyx is a Lower Bridger animal. Among the hoofed mammals or ungulates the delicate lophiodont Helaletes is most common, analogous to the Chasmotherium of France. Among the horses five species of Orohippus occur, all animals of small size and still possessing four digits on the fore feet. Among titanotheres principally the broad-headed Palewosyops and Limnohyops occur in rela- tively early stages of evolution. It is noteworthy that no traces of horns are found upon the heads of the titanotheres on this level. The pro- rhinoceroses, or hyracodonts, are represented only by the light-limbed M 162 THE AGE OF MAMMALS Hyrachyus. The tapirs have not as yet been discovered in the Lower Bridger. The mammal of most exceptional interest is the armadillo Fie. 61.— Outline restorations to same scale (X 3/5) of contemporary Middle Eocene mammals. By Charles R. Knight. A. Notharctus, a primate, arboreal. B. Orohippus, a primitive horse, cursorial. C. Hyrachyus, a primitive rhinoceros. D. Tillotherium, a tillo- dont. EH. Dromocyon, a creodont, cursorial. F. Palewosyops, a titanothere. G. Metachei- romys, an armadillo, ambulatory. H. Patriofelis, a creodont. Metacheiromys, similar in many respects to the smaller existing armadillos, but apparently possessing a leathery instead of a bony shield, the jaws lacking the columnar enamelless teeth of the existing Dasypus, but defended THE EOCENE OF EUROPE AND NORTH AMERICA 163 in front by a pair of sharp caniniform teeth coated with enamel. The ar- chaic edentate Stylinodon is doubtfully represented in this level. The tillodont stage is T’rogosus. Fic. 62.— A destroyer of Middle Eocene smaller mammals and birds. Skeleton of the slender-limbed creodont T'ritemnodon agilis. In the American Museum of Natural History. Upper Bridger Levels C and D, Lower Washakie and Lower Uinta. —'The geographic distribution of these contemporaneous depositions is displayed on the map on p. 120. Fic. 63. Skeleton of the Middle Eocene tapir-like titanothere Palwosyops leidyi. One of the large mammals of the Orohippus zone. In the American Museum of Natural History. (1) Upper Bridger: Uintatherium Zone. — This level is marked by the introduction of a number of new forms, including especially the great amblypod Dinocerata, which are represented by species of Uintatheriwm in various stages of evolution. These animals differ from Coryphodon in 164 THE AGE OF MAMMALS the absence of upper cropping teeth, and in the presence of spear-like tusks and two pairs of prominent osseous horns. The body is intermediate in proportion between those of the elephant and rhinoceros. The feet are extremely short and broad. The brain (Fig. 71) is no larger than that of a dog, out of all proportion to the body, and essentially of the archaic type. These animals are very abundant both in the Upper Bridger and Lower Washakie, and serve to tie these formations into a single life-zone. Of the creodont Carnivora the small hyzenodont Sinopa is becoming somewhat more rare. The large, powerful creodont Patriofelis of the family Oxyzenide, analogous in its proportions on a powerful scale to the modern wolverine (Gulo), and in its dentition to Hyena and Synoplotherium, was capable of attacking the largest contemporary mammals. Here also the skulking and swift-footed Mesonyx (or Dromocyon, Mesonychide) is represented by species of intermediate size (Fig. 52). Of the modernized Fic. 64.— The armadillo in North America. Skeleton of the Middle Eocene Metacheiromys tatusia of the Bridger formation. In the American Museum of Natural History. ungulates the tapirs ([sectolophus) occur, but are rare. The horses (Oro- hippus) as well as the primates (Notharctidz) are in a somewhat more advanced stage of dental evolution than in the Lower Bridger levels. The titanotheres now become polyphyletic through the appearance of three additional phyla (T'elmatherium, Manteoceras and Mesatirhinus) in ad- dition to the extremely broad-headed Palwosyops Thus indications of at least five phyla of titanotheres now occur, including long-headed forms with more hypsodont teeth, and short-headed forms with more brachyo- dont teeth. Of great interest is the development of rudimentary horns on the forehead above the orbits, which appear as ‘rectigradations,’ in all of these phyla. (2) Lower Washakie: Uintatherium Zone. — The Lower Brown Beds of the Washakie contain a fauna identical with that of the Upper Bridger C and D, namely, Uintatherium, Palewosyops, Manteoceras, Mesatirhinus, Notharctus, Hyrachyus, and Sinopa, in fact, the genera of the Lower Washa- kie are almost without exception found in the Bridger and are represented THE EOCENE OF EUROPE AND NORTH AMERICA 165 by species closely allied to those of the Upper Bridger and in some cases identical with them. None of these genera, however, excepting the insec- tivore Hyopsodus and the rodent Paramys survive into the Upper Uinta. A similar fauna is contained in the little-known Lower Uinta beds, south of the Uinta Mountains. These three levels (Upper Bridger, Lower Washa- kie, Lower Uinta) may all be regarded as marking the close of the Fic. 65. — Patriofelis, a powerful, jaguar-like creodont of the Middle Eocene. Above: Skeleton of Patriofelix vorax from the Bridger. Below: Restoration of the same by Charles R. Knight. Both in the American Museum of Natural History. Middle Eocene, although the distinction between Middle and Upper is naturally a somewhat artificial one and employed for purposes of con- venience. (3) Lower Uinta: Uintatheriwm Zone. — While the Upper Bridger and Lower Washakie deposits were accumulating north of the Uinta Mountains, the base of the Uinta series began to form south of this range, in north- eastern Utah. The lowermost beds (Uinta A) are composed largely of 166 THE AGE OF MAMMALS coarse, fluviatile materials and contain but few fossils, including Dino- cerata, the rhinoceroses (Amynodon), and Triplopus (an excessively light- limbed hyracodont), the aberrant titanotheres Sphenocelus and Metarhinus. The latter titanothere appears to be a dwarf and possibly aquatic or river- frequenting form, hence the specific name, M. fluviatilis. Upper Eocene, as Represented in the Upper Washakie and Middle and Upper Uinta. The Ludian Stage Upper Washakie : Eobasileus Zone. — In these famous beds, constitut- ing the Haystack Mountain, or Mammoth Buttes (Fig. 59) of Cope’s Fia. 66.— The Upper Eocene Eobasileus, the four-horned amblypod, last representative of its race. To the left a female, with small horns and tusks; to the right a male with large horns and tusks. After original by Charles R. Knight in the American Museum of Natural History. descriptions, the archaic fauna is distinguished by the final evolution of the Amblypoda into giant specialized Dinocerata, including the extremely long-headed form, Hobasileus ( = ‘Loxolophodon’) of Cope.’ Hobasileus (Fig. 66) represents a distinct phylum of amblypods, as shown by the more posterior position of the front pair of horns and the consequent great elon- gation of the snout; in Tinoceras the front horns are more anterior in position, and the snout is thus relatively shorter, the proportions of the 1 The type of the genus Tinoceras, namely, the species 7. anceps is from the Upper Bridger, Sage Creek, Horizon C. The type of the species 7’. ingens is probably from the Lower Washakie. (W. D. M. 1909). . whole being less dolichocephalic. Another feature of the archaic fauna is the giant size attained by members of the creodont mesonychids, the skulls of which equal those of the large modern brown bears of Alaska. The oxyenids are represented by much larger and more specialized forms of Limnocyon than those from the Upper Bridger. In regard to the modernized fauna the most conspicuous fact is the first appearance among the Perissodactyla of a new family of rhinoceroses, destined to become amphibious (Amynodontide). Among titanotheres the extremely brachycephalic Palwosyops, belonging to a phylum already dwarfed (P. copez) in the lower stage, is now apparently extinct. The , THE EOCENE OF EUROPE AND NORTH AMERICA 167 ; ; ; ——— Fic. 67.— Heart of the Washakie Badlands in the Eobasileus Zone, “ Adobe Town,”’ five miles east of Kinney Ranch, Wyoming. Photograph by American Museum of Natural History, 1895. : . most signal advance in this titanothere family is the appearance of the extremely long-headed Dolichorhinus (Fig. 49) with incipient horns, an extreme type also destined to become extinct, while the less extreme prophet- horned titanothere Manteoceras (Fig. 49) apparently survives and gives rise to certain of the giant quadrupeds of the Lower Oligocene. Among Artiodactyla of the entelodont family the robust ‘giant pig’ or omnivore Achenodon is also distinctive of this level. The other mammals represent a continuation of the Bridger fauna. All the small mammals are com- paratively rare, probably because the coarse conditions of deposition were unfavorable for their preservation. Thus the Equide and the Artiodactyla of this stage are still unknown. The mammals characteristic of this deposit 168° THE AGE OF MAMMALS (Dolichorhinus, Amynodon, and ?Eobasileus) are also found in the Middle Uinta, south of the Uinta Mountains; several other genera are common to these two formations. Middle Uinta: ?Eobasileus Zone. — This level is believed to be of the same age as the Upper Washakie because of the presence of a great abun- dance of the long-skulled titanothere Dolichorhinus of the species D. hyogna- thus. Other titanotheres abundant here are of the supposed fluviatile or Metarhinustype. Among rhinoceroses, two phyla, namely, the light-limbed Fria. 68.— Upper Eocene Uinta Formation, near the mouth of White River, Utah. Base of Uinta, Horizon C. The true Diplacodon Zone. Wortman and Peterson prospecting. Photograph by American Museum of Natural History, 1895. hyracodonts (Triplopus) and the amynodonts (Fig. 75) occur. These amynodont rhinoceroses are distinguished by powerfully developed upper and lower canine teeth; they now considerably exceed the existing tapirs in size. This geological level is also distinguished as containing limb bones of the last known survivors of the great Amblypoda, but these animals have not as yet been specifically determined. Another distinguishing feature is that the Artiodactyla are more numerous and varied because it is at this stage that we first know of the existence in America of the very important family of Hypertragulidee (Leptotragulus, Leptoreodon), small selenodont ruminants which were at one time believed to be ancestral to the camels and oreodonts, but are now considered (Matthew) distinct. The entelodonts are represented by Protelotherium, a successor of Achano- don. Among the unguiculates, two families of rodents are recorded: (1) Is- chyromyide (Paramys), and (2) Heteromyidee (Protoptychus). Of the archaic Carnivora the oxyznids and mesonychids still survive, the latter family being represented by the giant form Harpagolestes, which is also THE EOCENE OF EUROPE AND NORTH AMERICA 169 recorded in the Upper Washakie. Among the modernized or progressive Carnivora the first true dogs (Canidz) are reported here (Procynodictis). Altogether these beds closely agree with the Upper Washakie, and together may be considered as constituting the base of the Upper Eocene. Upper Uinta: Diplacodon Zone.— These upper or true Uinta beds were named by Marsh‘ in 1877 as the site of an important stage in the UPPER EOCENE ~<— Dolichorhinus cornutus, chief fossiliferous level Amynodon Metarhinus ees zone )<— Chief fossiliferous level Metarhinus MIDDLE EOCENE (SUMMIT) LATER EOCENE OF UINTA BAS! By permission of the U.S. Geological Survey. Fie. 69.— Scale section of the Middle and Upper Eocene of the Uinta Basin. After Peterson. evolution of the titanotheres, the genus Diplacodon. Here too is found a robust titanothere known as Protitanotherium, which is intermediate be- tween Manteoceras and the horned titanotheres of the Lower Oligocene; in this animal the horns are prominent, oval, osseous projections at the junc- tion of the frontal and nasal bones. Altogether three or four phyla of titanotheres occur here, including animals equal in size to the largest exist- ing rhinoceroses. Thus it would appear that after the extinction of the Dinocerata the titanotheres at once became the dominant quadrupeds of ‘Marsh, Introduction and Succession of Vertebrate Life in America. Amer. Jour. Sci., ser. 3, Vol. IX, 1877, pp. 337-378. 170 THE AGE OF MAMMALS western America. The Equide are represented by Epihippus, the very diminutive horse in a stage of evolution which is not quite so advanced as that of Lophiotherium cervulum of the gypse, or Ludian, stage of France. The tapirs (Isectolophus) and rhinoceroses (Amynodon) occur, but in general we observe that forest and fluviatile, or river-frequenting, forms are rare in this formation. This explains perhaps why the bunodont or omnivorous entelodonts, or elotheres, have not been found. The conclusion is that the conditions of deposition and fossilization at this time were less favor- able to the collection of river and swamp dwellers, and more favorable to the preservation of the upland and meadow or field Herbivora. For the first time in North American history the Artiodactyla of the ruminant division, or Pecora, begin to abound, herbivores of diminutive and intermediate size, with short-crowned molar teeth of the crescentic or selenodont pattern. The Dichobunide, or Homacodontide, are represented by Bunomeryx. Most interesting is the rise of the camel family. Thus the Camelide, or Hypertragulide, are represented by four genera, Lepto- tragulus, Protylopus, Camelomeryx, Oromeryx. Of these, the diminutive Protylopus has been selected as the possible ancestor of the grand phylum of American camels. The polyphyletic tendency in this family is already displayed, and undoubtedly more than one line is represented here. The Oreodontidse are similarly abundant, embracing ancestors both of the typical oreodonts (Protoreodon) and of the aberrant agriochcerids (Pro- tagriocherus). Among the carnivorous enemies of these Herbivora were the smaller creodont oxyzenids and the giant Mesonyx, as well as the smaller fox-like canids or pro-Carnivora, Miacis and Procynodictis. This is the last ap- pearance in North America of these two creodont families (Oxyzenide and Mesonychidee), and there is some reason for thinking that the American Hyzenodontide (Sinopa) had already become extinct and that the hyzeno- donts which we shall find appearing in the Lower Oligocene were invading forms from the Old World or from the north. If this proves to be the case, it may be said that the Upper Eocene of America is marked by the final disappearance of all the archaic herbivorous and carnivorous mammals of American residence as well as by the incipient extension of the great order Artiodactyla. Tue ATLANTIC Coast REGION The Zeuglodon Zone. — The Zeuglodon Beds of the southeastern states are referred to the Jackson! Formation, which is regarded as the middle 1 Lyell, 1847, was the first to assign the Zeuglodon beds to the Jackson Formation below the Vicksburg; this was recognized by Hale, and strongly insisted on by Hilgard (1867). The Jack- son was regarded by Dana (1895) as Middle Eocene, approximately equivalent to the Bridger Formation in the Rocky Mountain region. ——_——— hee i, THE EOCENE OF EUROPE AND NORTH AMERICA Let or the summit of the Eocene. As described by Schuchert and Lucas,! the beds vary in thickness from five to ten feet, but are of great geographic extent, since bones are recorded from Florida to Arkansas. In Choctaw County, Alabama, the strata are buff or whitish marl with some green glauconitic sand. They thus belong to an old soft seabottom, in which the bones are either isolated, or more or less of a skeleton may be found in position and undisturbed. The great marine mammal known as Zeuglodon undoubtedly lived in large numbers in the ancient Gulf of Mexico, as well as in the seas of south- ern Europe and northern Africa. Its proportions were not like those of Fic. 70.— The primitive whale Zeuglodon cetoides from the Eocene of Alabama. Drawn by Charles R. Knight under the direction of F. A. Lucas. Original in the American Museum of Natural History. the existing whales, because the diameter was not more than six or eight feet through the thickest part of the body, while the length reached fifty or even seventy feet, about forty feet of which constituted the long and freely movable tail. This tail, in the opinion of Lucas,’ ended in a fluke, which would indicate that the mammal was a constant diver. The head was relatively small, but the jaws were provided with great grasping and cutting teeth. There was a pair of short fore paddles just behind the head, but the hind limbs were vestigial and retained within the skin. The shoulder blades were like those of a whale, but the extremely elongate 1 Lucas, F. A., The Pelvic Girdle of Zeuglodon, Basilosaurus Cetoides (Owen), with Notes on Other Portions of the Skeleton. Proc. U.S. Nat. Mus., Vol. XXIII, pp. 327-331, 1900. 2 Lucas, Animals of the Past. New York, 1901. 1 i THE AGE OF MAMMALS vertebree differ from those of any other known animal. The ancestral zeuglodonts are known in the Eocene of Africa. It appears possible that these great American forms are migrants from the Mediterranean seas of the Old World ( see p. 73). CAUSES OF EXTINCTION OF THE ARCHAIC ORDERS OF EOCENE MAMMALIA! Extinction is not on the same scale nor due to the same causes through- out the successive geologic epochs. The great law of mammalian improve- ment through the elimination of the least fitted becomes less sweeping in its effects as time goes on and the Mammalia become perfected. Eocene extinction is chiefly that of whole orders of archaic mammals. Late Eocene and Oligocene extinction is preéminently that of inadaptive families. Miocene times complete the elimination of families and are characterized by the extinction of inadaptive genera. This is also true of Pliocene times. The especial feature of Pleistocene times is the ruthless and world-wide extinction of highly adaptive kinds of mammals in certain parts of the world, both of genera and of species. Competition of lower and higher types. — It is a very striking fact that not only the archaic but a very large proportion of what we may term the prophetic, modernized, Kocene mammals became extinct at or before the close of this period. The causes of extinction were probably not the same in the two groups. The archaic mammals are very generally dis- tinguished by extremely small brains. This is certainly true of many of the creodonts, of Phenacodus, Coryphodon, and the Dinocerata. This limited brain power placed these quadrupeds at a disadvantage in com- petition with the higher placentals. Under contemporary or prevailing conditions of life, intelligence and instinct are matters of first importance in relation to quickness, alertness, adaptability to new conditions. Modern quadrupeds differ widely in this regard; on the western plains of North America, for example, the horses by their resourcefulness save their lives where cattle perish. The cursorial Phenacodontidze measured their psychic powers with the cursorial Equide; the tooth structure in the two families was substantially the same, but the phenacodonts were handicapped by a lower brain organization and by an inferior foot mechanism. The long survival and steady increase in size of the clumsy Amblypoda is one of the most astonishing phenomena of Eocene mammal life. The extinction of these mammals may be attributed to two causes: the low brain power, which may have inhibited the proper defense and care of the young, and the arrested evolution of the grinding teeth, which are actually no larger and little more effective for the comminution of food in the giant Uinta- therium than in the smaller Coryphodon. It is noteworthy that where the 1QOsborn, H. F., The Causes of Extinction of Mammalia. Amer. Natural., Vol. XL, no. 479, Nov. 1906, no. 480, Dec. 1906. See especially pp. 856-857, 850-854, 842. and mode es (oblique lines) I Corypho 1 @ 174 THE AGE OF MAMMALS evolution of an animal runs to the development of tusks and horns, prob- ably favored by sexual selection, the grinding teeth are apparently neg- lected and are apt to show arrested development. The widespread belief that bulky animals tend to disappear first is inconsistent with the fact that the small phenacodonts became extinct long before the large Amblypoda. Among the modernized Eocene Herbivora of Europe, several of the small Artiodactyla became extinct very soon after the period which marked the extinction of the bulky lophiodonts. Thus bulk is chiefly fatal where Li] UPPER = Lu MIDDLE Fic. 72.— Evolution of mammals in North America. (In solid black) Archaic mammals which became extinct in the Eocene and (creodonts) Oligocene Epochs, namely : multituber- culates, creodonts, tillodonts, teeniodonts, condylarths, and amblypods. (In hollow lines) Ap- pearance and extinction of archaic and modernized mammals which survive to Pleistocene or recent time, namely : marsupials, insectivores, carnivores, rodents, edentates, primates, peris- sodactyls, proboscideans. correlated with inadequate feeding mechanism, with brain power not adequate to enabling the females to defend and care for the young as well as to meet new conditions of life, and with inadequate defensive organs. The competition of the archaic Creodonta with the diminutive pro- Carnivora in Eocene times may be only remotely compared to the extinc- tion of the Tasmanian wolf (Thylacinus) and Tasmanian devil (Sar- cophilus) through the introduction of the true dog (Canis dingo) on the Australian main land. The steady increase in size of the creodonts as displayed in Patriofelis and in the enormously powerful Harpagolestes is a fact which may be placed parallel with the increasing size of the Amblypoda. It is noteworthy that the only archaic Carnivora which persisted into the Lower Oligocene are the hyzenodonts, in which the brain actually in- THE EOCENE OF EUROPE AND NORTH AMERICA 175 creased in size. Marsh’s laws‘ of the relations of brain growth to survival are apparently borne out by these comparisons, namely, that the brains of surviving races are upon the average larger than those of declining races. On the other hand in following the many causes of extinction through the entire Czenozoic we shall find that even large cerebral develop- ment, as in certain rhinoceroses (Teleoceras) and elephants (Mastodon), may fail to preserve a race. Diminished or contracted land areas. —In Europe especially the vary- ing coast lines, the insular conditions, the archipelagic surfaces, are to be seriously studied in connection with the extinction which overtook so many characteristic EKocene mammals before the opening of the Oligocene, so that the general aspect of the fauna is altogether different when the Oligo- cene fairly opens. Changes of land caused by elevation or subsidence operate indirectly through causing changes in all the physical conditions of climate, moisture, desiccation, temperature, and so forth; also more directly in facilitating the cutting off of migrations and introducing new competitions. North America and Africa were the stable continents of Tertiary times, which underwent slight fluctuations of land area as com- pared with the highly unstable continents of Europe and the southern half of South America. It must be stated, however, that the main phe- nomena of extinction in unstable Europe coincide with those in stable America. We have seen in group after group that the Upper Eocene mam- mals of peninsular Europe are not those which in the main give rise to the Oligocene fauna. A glance at western North America in Tertiary times as studied by J. Perrin Smith’ displays the important influence which must have been exerted by the relations of the Arctic, Pacific, and Atlantic oceans as affected by continental elevation and depression. During part of the Cretaceous, Smith believes that Asia and the Alaskan peninsula were con- nected across Behring Straits. Whenever the cold currents of the Arctic Ocean were cut off, the western coast of America enjoyed a warm, probably a subtropical climate (see p. 93). The same author believes that during early Tertiary times a connection existed between the Eocene seas of the Atlantic and Pacific to the south of California. By Miocene times this passage appears to have been closed. The opinion of this author is based upon the marine fauna. That based upon the land fauna is cited elsewhere (p. 81). In the north the land appears to have risen again toward the end of the Miocene, cutting off the Arctic Ocean, and giving a temperate though not tropical climate to the entire North Pacific. Insular conditions. — The substitution of insular for continental condi- 1 Marsh, Small Size of the Brain in Tertiary Mammals. Amer. Jour. Sci., Vol. VIII, 1874, pp. 66-67; also, On the Size of the Brain in Extinct Animals, Abstr. Nature, Vol. XXXII, London, 1885, p. 562. 2 Smith, J. P., Periodic Migrations between the Asiatic and the American Coasts of the Pacific Ocean. Amer. Jour. Sci., Vol. XVII, Mar. 1904, pp. 217-233. 176 THE AGE OF MAMMALS tions by subsidence has undoubtedly been a potent cause both of exter- mination in certain localities and of the survival of very primitive forms. It may be said at once that most of the causes both of survival and of extinction which prevail upon continents are intensified on islands.' Wal- lace attributed the widespread extinction which occurred in Australia in early Pleistocene times partly to the increased competition and struggle for existence caused by the progressively contracted land area due to sub- sidence.?. Wallace also rightly attributed the survival of certain primitive mammals among the monotremes and marsupials to the practically in- sular condition of the Australian region. On the other hand, there is reason to believe that the introduction of new forms of life on islands causes more rapid and profound modifications in the fauna than similar introductions on continents. 1 Osborn, H. F., The Causes of Extinction of Mammalia, Amer. Natural., Vol. XL, no. 479, Nov., 1906, pp. 769-795; no. 480, Dec., 1906, pp. 829-859. (See especially pp. 773-774.) 2 Wallace, A. R., The Geographical Distribution of Animals (1876). Vol. I, pp. 158-159. CHAPTER III THE OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA Tus period is sharply defined by great geographic revolutions as well as great transformations in its animal and plant life. In Europe it opens with the main elevation of the Pyrenees and is marked toward the close by the initial elevation of the Alps (Fig. 13, p. 59). We are able to study the Mammalia over a still wider geographic range. In America the principal ‘ . v Ps a we rt i ’ Promerycochoe ame. Ee oe - Lower 4 OSEOWE es ‘ ~~" ‘A tite me Fic. 73. —Summit of the Oligocene or transition to the Miocene. Lower: Brule Clays, or Leptauchenia Zone. Upper: Lower Rosebud, or Promerycochcoerus Zone. Exposures on the south side of the White River, near Porcupine Creek. Photograph by American Museum of Natural History, 1906. interest centers around our first knowledge of the life of the Great Plains region, a vista we have not enjoyed previously because all our former studies have been confined to the mammals of the mountain region. In Europe the plains fauna still remains unknown. The most remarkable fact is the remingling by intermigration and by fresh invasions of similar types from the north of the mammals of the New and Old Worlds, so that Europe and western America again constitute a single zodlogical region, or Holarctica. We thus enter the FourrH FaAuNAL PHASE. N 177 178 THE AGE OF MAMMALS IV. LOWER OLIGOCENE, FOURTH FAUNAL PHASE—THE SECOND MODERNIZATION. SUDDEN APPEARANCE IN _ EUROPE AND NORTH AMERICA OF NUMEROUS EXISTING FAMILIES OF MAMMALS. REUNION OF THE NEW AND OLD WORLD INTO A SINGLE ZOOLOGICAL REGION, FOLLOWED BY ANOTHER LONG PERIOD OF INDEPENDENT EVOLUTION AND PARTIAL EXTINCTION. The first impression of this phase is our sudden introduction to a large number of modernized types which had been slowly evolving elsewhere, probably in the plains of America and Eurasia. In North America this second modernization is shown to be still more remarkable than the first Fic. 74.— Lower Oligocene horizons resting upon the Upper, Middle, and Lower Eocene. Titanotherium Zone = Lower Oligocene. “ Bridger’? and ‘Uinta’? = Middle and Upper Eocene. Lambdotherium Zone = Lower Eocene. Escarpment of the Beaver Divide, near Hailey, Wyoming. Photograph by American Museum of Natural History, expedition of 1909. Compare Fig. 95. or Wasatch modernization, which was one of appearance of existing orders, because this is one of existing families, not as yet recognized in the mountain basins. The Oligocene fauna thus is far more familiar in aspect than the known Eocene. This new list in America includes six existing families of rodents, four existing families of carnivores, one existing family of peris- OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 179 sodactyls. A very similar modernization occurs in western Europe, many familiar modern families appearing for the first time. Several of these new families appear simultaneously in Europe and North America. Thus the two countries which were separated most widely at the close of the Eocene are again brought together in the Lower Oligocene, as shown in the accompanying table. MAMMALS OF THE LOWER OLIGOCENE Peculiar to Common to Europe and Peculiar to North Europe North America America Palzeotheres Titanotheres Horses Anoplotheres Chalicotheres Hyracodonts (rhinoceroses) Cenotheres Rhinoceroses (aceratheres Oreodonts Gelocids and diceratheres) Camelids Amphicyonids Amynodonts Hypertragulids Viverrids Anthracotheres Leptictids Cricetines (ham- Suillines Chrysochlorids? (insecti- sters) Entelodonts vores) Theridomyids Opossums Ischyromids ! (rodents) Sirenians (Hali- Hyzenodonts Leporids or hares theriwm) Canids (dogs) Mustelids (martens) Macherodonts (saber-tooth cats) The closest correspondence of the Old and New Worlds is seen to be among the perissodactyl ungulates and the carnivores; the least community is among the artiodactyl ungulates, which exhibit fewer families in common. It is a very striking fact that there was little interchange of the artio- dactyls of the New and Old Worlds until the Pleistocene. We note that forest and browsing quadrupeds prevail in both countries. A contrast is the apparent disappearance of the horses ‘in western Europe, and the rapid evolution of these animals in western North America. The continental influence of North America is still displayed in the presence of giant quadrupeds, especially the titanotheres and entelodonts, which greatly surpass in proportions the largest of European mammals of the time, which are of intermediate and smaller size; there is also, on the whole, a greater diversity in the American life. In the two countries six of the great families of perissodactyls and artiodactyls of Eocene origin die out. The last of the archaic carnivores (hyzenodonts) survive only to the Middle Oligocene. 1 The Ischyromyide, the American Eocene Rodentia par excellence, are regarded by Matthew as a primitive Eocene and Early Oligocene (Ischyromys, Prosciurus, Cylindrodon) group of squirrel-like or sciuromorph rodents. The great masseter muscle of the jaw lies entirely behind the infraorbital foramen, as it does in the existing sewellels (Haplodontide), also peculiarly American rodents, first observed in the Upper Oligocene, or John Day, and in the specialized Mylagaulids, a peculiar family of horned rodents of the Upper Miocene, both Sciuromorpha. 180 _ THE AGE OF MAMMALS Fic. 75.— Amynodonts, aquatic rhinoceroses of Europe and America. The Lower Oligo- cene Metamynodon of South Dakota. After original by Charles R. Knight in the American Museum of Natural History. The especially characteristic hoofed mammals, common to this great holarctic region and dominating in the two countries, which attain their maximum evolution and then disappear, are the following: TYPES SupPoseD ORIGIN Diceratheres, pair-horned rhinoceroses. ~ North America Amynodonts, amphibious rhinoceroses with canine tusks i ¢ Entelodonts, giant pigs with elongate skulls and stilted limbs Eurasia Anthracotheres, buno-selenodont artiodactyls, varied and attain- ss ing giant size in Europe only. These animals are all descendants of Upper Eocene ancestors. Among artiodactyl ungulates we discover partly descendants of Eocene families, partly new invading forms, the latter especially seen in Europe. The pre- vailing artiodactyls common to both countries exhibit five-cusped, brachy- odont, buno-selenodont molar teeth (anthracotheres); bunodont teeth are more rare (suillines and entelodonts). True four-cusped selenodont molars of modern type are observed in the oreodonts and hypertragulids and, in more specialized form, in the smaller pro-ruminants, or gelocids, newly arriving; also in the true ruminants, or cervulines, arriving in Europe in the Middle Oligocene, both probably of south Asiatic origin. It is noteworthy that all these primitive Oligocene ruminants of Europe, like their selenodont contemporaries, the hypertragulids in America, are hornless but usually provided with defensive tusks. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 181 The cenotheres are especially characteristic of the European Oligocene, although a few traces of the family appear as early as the Ludian (Upper Eocene). The cenotheres and surviving dichobunes of Europe, in spite of certain resemblances in their tooth structure, are very remote from one another; in fact, the ceenotheres form a somewhat isolated group (see p. 548). These peculiarly European forms reached their culmination in the Middle Oligocene, declined before the Oligocene ended, and seem to have become entirely extinct soon after the appearance of the invaders of the Miocene.' Fic. 76.— Entelodonts, giant pigs of Europe and America. A Middle Oligocene stage. (The position of the ears in this restoration is erroneous; they are placed too high. See Fig. 83.) After original by Charles R. Knight in the American Museum of Natural History. In America the majority of the Oligocene mammals have been discovered in the single geographic region of Dakota and in a continuous series of dep- ositions not exceeding 600 feet in thickness, which are known as the White River Group. Similar forms have been found in Wyoming, Montana, Colorado, and British Columbia. In Europe we find an analogous fauna in beds of very different geologic origin, and interspersed with rich records of plant life which are practically wanting in America. This is one of the most conspicuous instances of the advantages of correlation. Were it not for the convincing evidence to the contrary af- forded by the Old World, we should be inclined to regard the American Oligocene as a period marked by few geographic changes, but by certain 1 Stehlin, H. G., Die Siugetiere des schweizerischen Eoczens, 1903-1906, pp. 675, 687, 690. 182 THE AGE OF MAMMALS grand evolutionary changes in mammalian life; in other words, it is chiefly the vast evolutionary changes in the American mammals (horses, titano- theres, and rhinoceroses) which enable us to realize the enormous duration and grandeur of Oligocene times in America. As the Oligocene advances, the countries again diverge and become dis- similar in their faunal aspect. The correlation of the great time divisions and depositions in which these changes occur are as follows: Life Zones European Stages American Formations Diceratherium Zone Aquitanian Harrison John Day Formations White River (Upper) Metamynodon ( = Cadurcotherium) Stampian White River (Middle) Zone Ancodus (Titanotherium) Zone Sannoisian White River (Base) Paleogeography Continental connections. — With the Oligocene began an emergence of the continents from their prolonged Eocene submergence. The land masses of Europe, Asia, and North America became connected.' This is the theoret- ical explanation of the intermigrations which followed and of the invasion of a new fauna into North America and Europe, coming presumably from the circumpolar region. Whether the connection between the Old and New Worlds was by way of Alaska or across the whole breadth of the great polar continent is uncertain. In the accompanying map by Matthew the connection is indicated by way of Alaska and eastern Asia. In general the southern continental masses (South America and Australia) appear to have been disconnected. Of the great Lower Oligocene fauna now known in northern Africa, the larger part is exclusively African in type, but a smaller part includes a few mammals, such as the hyzenodonts, anthracotheres, certain suillines, and smaller rodents, which are also known in the Upper Eocene and Lower Oligocene of France. _ The fluviatile and estuarine sea-cows, or sirenians, were probably common to all the Mediterranean borders, African, Asiatic, European, and even the western Atlantic in Oligocene times. The Eocene Egyptian types (Ho- therium, Eosiren, Protosiren) are more primitive in the possession of hind limbs. The earliest of the European forms is Halitherium (H. veronense) from Middle Eocene limestones of northern Italy (Monte Zuello). The most primitive form in skull and tooth structure is Prorastomus from the (?) Eocene of the island of Jamaica, West Indies: The Oligocene stage is Halitheriwm schinzt from marine sands near Basel, Paris, Bordeaux, and Belgium.? The fact 1 De Lapparent, A., Traité de Géologie, 1906, p. 1547. 2 Abel, O., Die Sirenen der mediterranen Tertiirbildungen Osterreichs. Abh. K. K. Geol. Reichsanst., Vol. XIX, no. 2, Vienna, 1904. See especially pp. 214-223. ee ee ee a OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 183 that the Middle Eocene sirenians of Europe are more specialized than the Upper Eocene sirenians of Africa might be cited as evidence that the sire- nian center of diffusion was likewise to the northward. Geographic changes in Europe. — The early earth movements of the Oligocene caused an invasion of the sea in the north of France, and in Ger- many as far south as Leipzig. This vast northern ocean of Tongrian and Stampian age is believed to have made the northern climate of Europe more SS === = — = zB —a 4 fe ——s | 8 fA iz == > aS ¢ = 2 ca qa Le = oo Z = peeL lll oral Fic. 77.— Oligocene. A period of continental elevation and reunion followed by the reéstablishment of connections between the life of the New and Old Worlds. Central Europe submerged or partly archipelagic, African mammals and birds partly similar to those of Europe. Madagascar united with Africa. South America entirely separated, its mammals developing independently. Australia entirely separated. Closing the Oligocene, another long interval of separation between North America and Europe. Rearranged after W. D. Matthew, 1908. temperate. The lignitic flora of south central Germany now includes sequoias, birches (Betula), and palms (Palmacites).'. Southern Europe through the rise of the Pyrenees and Swiss Alps was elevated, and conditions were favorable for continental depositions rich in mammalian life both in southern France and in the south of Germany, as shown in Fig. 79. In the Aquitanian, or Upper Oligocene stage almost all of Europe had again emerged from the sea; great shallow lakes were scattered over France, Switzerland, Germany, Austria, Italy, and Greece. In southwestern France or Aquitania, from which the stage derives its name, there is a renewed advance of the sea over the land. The freshwater lakes are varied by 1 De Lapparent, A., Traité de Géologie, 1906, pp. 1547-1549. 184 THE AGE OF MAMMALS lagoons and swamps, with lignitic deposits. The flora indicates an increasing humidity, with moderate and equable warmth. The bird life of central France (Allier) is similar to that bordering certain lakes of the interior of Africa to-day.! According to De Lapparent,’ the Oligocene terminated LOWER_OLIGOCENE Fic. 78.— Europe in Lower Oligocene or Sannoisian times. White =land. Ruled = sea. Dotted areas = lagoons. After de Lapparent, 1906. by the drying up of the lakes, deepening of the valleys, and beginning of the river or fluviatile régime of the Lower Miocene. Thus the Oligocene of Europe is physiographically subdivided as follows: 3. Upper Oligocene. Aquitanian. Extensive freshwater lakes and lagoons. Recession of sea. | -2 12. Middle Oligocene. Stampian. Advance of sea in Paris Basin. a 1. Lower Oligocene. Sannoisian. Marine and_ brackish deposits H ———a lacustrine and marine marls. Flora and Climate Europe. — A new character is given to the Oligocene flora by the disap- pearance of many tropical forms, and the appearance of a great many |. non-tropical forms; with few exceptions this flora has its modern repre- sentatives north of the Equator.* The temperature fell somewhat, and 1 Milne Edwards, A., Recherches Anatomiques et Paléontologiques pour servir 4 1|’Histoire des Oiseaux Fossiles de la France. Paris, 1869-1871, p. 570. 2 De Lapparent, A., Traité de Géologie, 1906, p. 1598. 3 Schimper und Schenk, Handbuch der Palzeontologie, ed. by von Zittel, Pt. II, 1, Pal- seophytologie, 1890, p. 802. Ss OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 185 there was a lessening of humidity. The occurrence of palms (Sabal, Cha- merops) in the Baltic region indicates a mean annual temperature of at least 18° C. or 64° F., the existing isotherm of southern Spain and Italy. The prevailing forest flora includes palms, sequoias, and numerous other conifers, figs, cinnamons, magnolias, and trees of south temperate forest type. African, Indian, and Australian types become more rare.' Cooler Lower Oligocene conditions of the northern coast of Europe are indicated in the rich flora of the amber beds of K6nigsberg (55° north), which include pines, spruces, sequolas, cypresses, oaks, chestnuts, beeches, maples, and also the cinnamon; in the main a north temperate flora.? The period in general is marked by the increase of conifers and the spread of decid- uous trees. Along certain lake borders (Aix, Gargas) of southern France the heat and drought during the latter part of the summer were extreme (de Saporta). The climate of the Oligocene was thus less uniform; the dif- ference in seasons became more marked. We know nothing of the grasses. The structure of the teeth of the mammals indicates the continued preva- lence of browsing types, and a very small percentage of grazing and grass- eating types. Forest and swamp-living types are still very numerous. In the Middle Oligocene of central France (Aix) are found conifers, palms (Flabellaria), and cinnamons.* North America. —Unfortunately there are no leaf-bearing beds of cer- tain Oligocene age; in fact, we know nothing of the flora of the region of the great plains in Oligocene times. A hint as to the temperature of Dakota is afforded by the discovery by Loomis * of crocodiles in the old river deposits of the Lower White River group, sure indication of south temperate or Floridian conditions of climate. The Kenai beds of Alaska, formerly con- sidered Oligocene, are now referred to the Eocene’ and possibly Upper Cretaceous.° Thus we must depend upon Europe for our knowledge of the North American climate, and the presence in the two countries of so many similar forms of mammals indicates a uniformity of temperature. Physiographic Conditions Europe. — The abundant localities where Oligocene mammals are found in Europe indicate an undulating country, thickly forested in places, with still-water predominating over fluviatile depositions. In contrast with the Eocene, fluvio-marine deposits are rare. Most localities are ‘continen- tal,’ or in the interior. Exceptions are the fluvio-marine sands of the Faytm ' Geikie, A., Textbook of Geology. London, 1893, p. 991. 2 Goeppert, Flora des Bernsteins, Vol. I, 1883, Vol. II (Goeppert, Menge, Conwentz), 1886. 3 Geikie, A., Textbook of Geology, 1893, p. 990. 4 Loomis, F. B., Two New River Reptiles from the Titanothere Beds. Amer. Jour. Sci., Dec., 1904, Ser. 4, Vol. XVIII, pp. 427-432. 5 Knowlton, F. H., Fossil Flora of Alaska. Bull. Geol. Soc. Amer., Vol. V, 1893, p. 587. * © Note by Dr. Hollick, March, 1909. 186 THE AGE OF MAMMALS (Fig. 79, 28), on the northern shore of the African continent, and of Hemp- stead (24). The Upper Oligocene sands of Pyrimont in Savoy (Fig. 84, 4) are of fluviatile origm. The Oligocene opens with the still-water marls and limestones of Ronzon (Fig. 79, 13) in southern France, and closes with the extensive lacustrine or freshwater limestones of St. Gérand-le-Puy (Fig. 84, 2) in the Bourbonnais. Lignites or deposits of thick swamp vegetation are abundant, as at Calaf (Fig. 79, 25) and Tarrega (26), Spain, at Célas (3) (Gard) in France, and Cadibona (Liguria) (Fig. 82, 46) in Italy. Of this period are the fissure deposits or Bohnerze of the Jura (Swabia), Frohn- stetten (Fig. 79, 17), and other localities. The most famous fissure deposits are those of Quercy (Fig. 79,12) which, we may recall (p. 151), begin in the Upper Eocene and continue into Middle Oligocene times. Fic. 79.—Lower Oligocene. Sannoisian, or Lower Tongrian. FRANCE.— Lagoon deposits near Paris: marnes blanches de 1 Pantin, 2 Romainville. Lignites de 3 Célas, 4 Avé- jan, 5 Vermeil (Gard). 6 Fronsac (Gironde). Caleaire grossier de % La Grave (Gironde) dis- tinct from that of Paris. Gypse de 8 Sainte-Sabine (Dordogne). Argiles de 9 Duras (Dor- ° dogne). Calcaire d’ 10 Issigeac (Dordogne). 11 Saint-Cernin (Dordogne). Phosphorites du 12 Quercy, south central France, in part. Marnes et calcaires (100 meters) de 18 Ronzon, near Lyons. Calcaire de 14 Brie, north of Paris. GERMANY. — Fluviatile, Melanienkalke von 15 Brunnstatt, 16 Rixheim (Alsatia). Bohnerz von 17 Frohnstetten (Suabia) ; Asphaltkalk von 18 Lobsann (Alsatia) ; Bohnerz von 19 Vehringerdorf, 20 Vehringen, 21 Eselsberg, near Ulm, 22 Hochberg in Suabian Jura; Bohnerz von 23 Oerlingerthal, near Ulm. ENGLAND.— Fluvio-marine clay and marl (140 ft.) of 24 Hempstead on Isle of Wight. SPAIN.— Lignites of 25 Calaf, 26 Tarrega near Barcelona. AUSTRIA-HUNGARY. — Flysch, freshwater and marine of 27 Monte-Promina (Dalmatia). EGYPT,—Sand and clay, fluvio-marine, of 28 the Fayam. Correlation of Depéret. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 187 I. OLIGOCENE LIFE OF EUROPE Lower OLIGOCENE, SANNOISIAN, OR LowER TONGRIAN This stage takes its name from the marnes de Sannois in France and from Tongres in Belgium. According to Depéret ' the early fauna of the lignites de Célas, Avéjan, Vermeil (Fig. 79, 3-5), as well as several deposits in the south of France (6-11), part of Querey (12), and Frohnstetten in Swabia (17) are of this age. The mammals of these deposits do not present any Oligo- Fic. 80.— Entelodonts of the New and Old Worlds. Skeleton of the giant Upper Oligocene entelodont Dinohyus hollandi. Inthe Carnegie Museum, Pittsburg. After Peterson. cene characters; they are simply a continuation of the paleotheres, anop- lotheres, and last of the xiphodonts of the Upper Eocene or Ludian. The first real Oligocene fauna is that of the marls of Ronzon (13) in the Rhone valley near Lyons, which succeeds the fauna of the gypse or Ludian, and contains the new Oligocene mammals. Of the same age are the mam- mals of Hempstead (24) (Isle of Wight), of Lobsann (18) (Alsace), Calaf and Tarrega (25, 26) (Spain) numerous deposits in Swabia (19-23), and possibly of Monte Promina in Dalmatia (27). The mammals of this stage are of three kinds: (1) those descended from the Upper Eocene fauna of Europe; (2) those of fresh north or south Asiatic origin or previously undiscovered; (3) those apparently from 1 Depéret, L’évolution des Mammiféres tertiaires; l’importance des migrations (Oligo- céne). C.R. Acad. Sci. Paris, Vol. CXLII, séa. March 12, 1906, pp. 618 seq. 188 THE AGE OF MAMMALS North America or first known in the Upper Eocene of that region. The conspectus of this fauna is as follows: Among the odd-toed ungulates of this as- LOWER OLIGOCENE semblage the horses (Equidse) are conspicu- GRouP ous by their absence. The palotheres (Pa- a. (Continued from Eocene) leotherium, Plagiolophus) are entering on their Palzeotheres decline. The rhinoceroses are represented Anthracotheres by a small form (Ronzotherium) with sub- Anoplotheres hypsodont molar teeth which appears to be Ceenotheres of the river-frequenting, amynodont type Canids (dogs) rather than a true rhinoceros. Tapirs have Erinaceids not appeared in Europe at this stage. . Opossums The last of the anoplotheres occur at this Hyzenodonts level. Among the even-toed ungulates the b. (New Arrivals) entelodonts, supposed migrants from America, Rhinoceroses are still rare. The anthracotheres are begin- Entelodonts ning their dominant reign. These animals are Gelocids purely European in origin, hardy travelers Mustelids and versatile feeders; they are very widely dis- Amphicyonids tributed geographically and form valuable means Cricetines for time correlation. They are polyphyletic and (hamsters) include hypsodont and brachyodont branches as follows: (1) The typical Ancodus (Hyo- potamus) velaunus of Ronzon, with its long-crowned molar teeth, is of the same evolution stage as the animals (A. bovinus) found at Hempstead on the Isle of Wight; it is a bit more hypsodont or modern than our Ancodus (A. americanus, A. brachyrhynchus, A. rostratus) of the great plains of ancient Dakota. (2) The short-crowned anthracothere Brachyodus also occurs in the Fayim of northern Egypt (B. goringii), in Dakota (B. brachyrhynchus), and at Hempstead. It is descended from the Catadon- therium of the Lutetian. (3) Anthracotherium also occurs, an ancestor of the giant Middle Oligocene forms. The anthracotheres' also exhibit a divergence into dolichocephalic and brachycephalic forms. There is a wide geographic distribution of the ancodons in Europe, Africa, Asia, and North America. No ancestral forms have been discovered in the Amer- ican Eocene, and their abundance in the Upper Eocene of Europe and Africa points to migration from the Old World; it would appear that from a north Asiatic center these animals may have migrated independently to Europe, southern Asia, and to North America. The American species occur in four successive levels, and parallel those of Europe in their evolution. Whereas in Europe they disappeared at the close of the Middle Oligocene, in North America they survived to the Lower Miocene, represented by an ‘Matthew, W. D., Observations upon the Genus Ancodon, Bull. Amer. Mus. Nat. Hist., Vol. XXVI, Art. i, Jan. 5, 1909, pp. 1-7. OLIGOCENE OF EHUROPE, NORTH AFRICA, AND NORTH AMERICA 189 animal (Arretotherium) more or less similar to the last survivor (Merycopot- amus) in the Miocene of India. Most interesting among artiodactyls is the newly arriving, small, and primitive ruminant Gelocus, which appears in the midst of this varied browsing fauna, a representative of the family Gelocidxe, analogous to the existing chevrotains, and a harbinger rather than ancestor of the varied artiodactyl groups of later periods. The remainder of the mammal fauna of Ronzon may be partly described, in the language of Filhol (1881) as revealing to us an aquatic and riparian Fic. 81.— Hyzenodonts, common to Europe, Africa, and America. Skeleton of the Middle Oligocene creodont Hyenodon horridus of South Dakota. In the American Museum of Natu- ral History. fauna with a few truly terrestrial animals, including also remains of birds, reptiles, fish, insects, crustaceans, and molluses. The insectivores are repre- sented by primitive hedgehogs, the rodents by chinchilla-like Therido- myide, and the hamsters (Cricetodon). The opossums (Didelphyid) were very small, and for the most part belonged to the Peratherium group, which persists with little change from the Upper Eocene. The carnivores are all small forms, excepting the creodont Hyanodon. No machzerodont cats, or felids, have been discovered at this stage. The canid family is raried, including Cynodon, Cynodictis, and Amphicynodon; the former, in its rather spreading feet, long tail, and shape of the head, suggesting the otter. We wonder at the absence of larger carnivores, for the ungulates are worthy of stronger hunters than those which are known. The Mus- telide, or marten family, is represented by Proplesictis; the otter has not been. observed. 190 THE AGE OF MAMMALS Milne Edwards! has described the birds of Ronzon as including the Accipitres (Teracus), Grallz, allied to the plovers, also phcenicopterids, including birds allied to the flamingoes but of more slender build and with shorter feet. The gannets are also represented. Mippie OLIGOCENE, STAMPIAN Upper Tongrian Our knowledge of the European mammals of this stage extends still more widely, especially to the east of the Adriatic, including a marl deposit as far east as Styria (Austria) (Fig. 82, 48). The rich final deposits of the phosphorites de Quercy are of this age. In this age, too, are the lignites of Cadibona (Liguria) (46), the deposits of Moissac (85) in southwestern France, containing the first undoubted paired-horned rhinoceros (D. minutum),’ also of Céreste (22) and Manosque (23) in southeastern France; to the north are the lacustrine sands of Ferté Alais (Seine-et-Oise) (1). In the summit of the Stampian are the lacustrine deposits of Gannat (16) in central France (Allier), which have yielded the large hornless tetradactyl rhinoceros (A. gannatense). Altogether Depéret has listed fifty localities, as shown in Fig. 82. At this time the tree flora was one of sequoias and cinnamons. In northern Italy flourished palms that require an even temperature of 25°C. (77° F.) similar to that of Brazil. Characteristic mammalian life. —The affinity to America is strength- ened by the arrival of fresh perissodactyls, including the first appearance in Europe of the tapirs (Protapirus, Paratapirus), of the true hornless rhinoceroses (aceratheres), remarkably similar to those of the Middle Beds of the White River group, Dakota, also of undoubted diceratheres, or pair-horned rhinoceroses. The amphibious rhinoceroses, or amynodonts, are represented by Cadurcotherium with hypsodont teeth, in a state of evolution closely similar to that of Metamynodon of our western plains. An entire lower jaw of Cadurcotherium* was found at Bournoncle St. Pierre; there is little doubt that this highly specialized amynodont belongs to the age of Moissac in France. These similarities tend to establish a parallel with the Oreodon and Metamynodon Zones (Fig. 101) of the White River group of South Dakota, which are accordingly regarded as of Middle Oligocene age. The artiodactyl ruminants increase. — Fresh Asiatic elements make their first appearance; e.g. the cervuline deer (Dremotherium) which, although hornless, is compared with the existing muntjacs (Cervulus) of the southern 1 Milne Edwards, A., Oiseaux Fossiles de la France, 1869-1871, p. 552. 2 This dicerathere of Moissac is more progressive in its horn development than any of the ancestral diceratheres of the Oreodon Zones. * Boule, M., Le Cadurcotherium. C. R. Acad. Sct. Paris, 1896, Vol. CX XII, pp. 1150-1152. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 191 and eastern parts of Asia, animals which are fond of hilly ground covered with forests, and related to the true deer, or Cervine. At the same time the gelocids (Gelocus) make their last appearance in western Europe. Arrivals from the northerly regions are the beavers, or castorids (Steneo- Fic. 82.— Middle Oligocene. Stampian or Upper Tongrian. FRANCE.—Sables de 1 la Ferté-Alais, in Paris basin, lacustrine. In the basin of the Allier and the upper Loire: 2 Bournoncle-Saint-Pierre, 3 Bons, 4 Perrier, Autrac, Solignat, Orsonnette, Malhat, Les Pra- deaux, Les Chauffours, Bansat, Chibrac, Jussat, Romagnat, Pérignat, Lemdes, Cournon, 5 Montaigut-le-Blanc, 6 Champeix, 7 Saint-Germain-Lembron, Boudes, 8 Antoingt, 9 Vodable, 10 Lamontgie, 11 Nonette, 12 La Sauvetat, 13 Gergovia, 14 Marcoin, 15 Chaptuzat; lacustrine deposits of 16 Gannat; 17% Saint-Menoux, 18 Vaumas, 19 Saint-Pourcain-sur-Bebre, 20 Bri- ennon, 21 Digoin. Schistes de 22 Céreste, near Aix. Gypse et marnes, lignites de 23 Ma- nosque, near Aix (600 meters). Argiles de 24 Saint-Henri, near Marseilles. Calcaires gypsiféres de 25 les Milles, near Aix. 26 Auzon (Gard). 2% Perne (Vaucluse). In the Garonne basin: 28 Cestayrol, 29 Saint-Sulpice, 830 Rabastens, hill of Saint-Martin, l’Isle d’ Albi, 31 Montans; mollasse de 32 Salvagnac, 38 Villebramar; Pont-Sainte-Marie, Ca- pellier, Les Péries, la Milloque, Comberatiére, Itier, Bourg de Visa, 84 Tournon; mollasse de 35 Moissac; 36 Beawville, 3% Montségur; phosphorites de 38 Quercy (greater part). GERMANY. ~— Meeressande von 89 Ufhofen, in central Germany. Septarienthon von 40 Flonheim, near Mayence. Cyrenen-Mergel von 41 Miesbach (Bavaria). Braunkohlenla- gerung von 42 Schliichtern, 42a Gusternhain, 43 Westerwald, in southwestern Prussia. SWITZERLAND. —44 Blauen, near Basel. 45 La Conversion, near Lausanne. ITALY.— Lignitic deposits of 46 Cadibona (Liguria), 47 Monteviale, Zovencedo (Vicenza). AUSTRIA.— 48 Trifail (Styria). 49 marls in Dalmatia. ISLAND OF MAJORCA. — Lignites of 50 Inca. Correlation of Depéret. fiber). Among insectivores appear the water voles, desmans or myogalids, also the shrews or soricids (Amphisorex). Among rodents there also ap- pear the lagomorph picas or tailless hares (Lagomyide, Titanomys), animals which are at present distributed in the mountainous parts of Asia, eastern Europe (one species), and North America (one species). 192 THE AGE OF MAMMALS Among animals of prey, representatives of the true cats (Felidae, Pseu- delurus) first appear, and in the streams for the first time the otters (Pota- motherium) occur. Probably also from northern Eurasia or from America arrived the first of the saber-tooth cats (Felide-Machzrodontinie); it is noteworthy that machzrodonts (Dinictis) are also first known in the Lower Oligocene of our western plains. Still greater variety is lent to the mammalian fauna by the entrance either from southern Asia or from Africa of representatives of two of the Fic. 83.— Entelodonts of the New and Old Worlds. Model of the giant Upper Oligo- cene entelodont Dinohyus hollandi of western Nebraska. From original by Theodore A. Mills, executed under the direction of O. A. Peterson, in the Carnegie Museum, Pittsburg. edentate orders, the aardvarks (Tubulidentata), which are represented by the archaic Archworycteropus, and the pangolins, or scaly anteaters, repre- sented by Leptomanis. Since these animals have not as yet been found in the Lower Oligocene of Africa, it is uncertain whether they are of African or of Asiatic origin; on the whole, the evidence favors their northerly or Asiatic origin; the pangolins are widely distributed in the later Caenozoic of Asia. Altogether this assemblage, as listed by Depéret, is a most imposing one. As shown in the accompanying conspectus, mingled with these new migrant or foreign forms we find the continuation of the greater part of the Lower Oligocene mammals as listed on p. 188. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 193 The members of this fauna that are dying out are the hyzenodonts, paleotheres, and entelodonts. The apparent extinction of these giant pigs (entelodonts) in Europe is note- CHARACTERISTIC MAMMALS worthy, because in America they sur- Amynodonts vive to the summit of the Oligocene (Cadurcotherium) or Lower Miocene and attain an enor- Paleotheres, last appearance mous size. They also are recorded Chalicotheres (Tetraconodon) in Miocene or Pliocene Entelodonts, last appearance deposits of India. Hyzenodonts, last appearance The Oligocene faunal approxima- Anthracotheres of large size tion to America is the closest at this Rodents of many existing families stage. The continued absence of Insectivores of many existing families horses is very remarkable; it is doubt- Amphicyonids less due to the prevalence of forests Macherodonts and the absence of open plains. The Lutrines, or otters anthracotheres attain a large size. Viverrids The aceratheres, hornless rhinoceroses, Pangolins, scaly anteaters are very similar in their dental evolu- Aardvarks, orycteropids tion to those of Dakota. The pair- horned rhinoceroses (Diceratherium minutum) are more advanced in the development of their horns than those of the White River Group of Dakota. The chalicotheres are repre- sented by Schizotherium, a more advanced stage than the Pernatherium of the Upper Eocene of France. On the whole, the fauna is still that of river and lake borders, of forests, streams, and small meadows and glades. UppeR OLIGOCENE, AQUITANIAN This is the age typified by the mammals of the famous lacustrine beds of St. Gérand-le-Puy (Allier) (Fig. 84, 2) in the heart of France. Of nearly identical age in America are the Middle and Upper beds of the John Day Formation in Oregon, as indicated by similar stages in the evolution of the mammals. In the Old World, while the localities as listed by Depéret ' are only eighteen in number, they may be traced as far east as Hungary. In Germany are the rich deposits of Eggingen (11) near Ulm. In Savoy, on the borders of Switzerland, Depéret has unearthed at Pyrimont (4) a fauna which promises to be richer and more complete even than that of St. Gérand-le-Puy. As noted on p. 183, Europe has now taken on its modern outlines. This is a period of great bodies of freshwater, partly bordered with decidu- ous trees of modern type. The deposits of St. Gérand-le-Puy, of Pyrimont (Savoy), of Weisenau near Mayence, and of Ulm in the basin of the Upper 1 Depéret, L’évolution des Mammiféres tertiaires; l’importance des migrations (Oligo- céne). CC. R. Acad. Sci. Paris, Vol. CXLII, séa. March 12, 1906, p. 618. Oo 194 THE AGE OF MAMMALS Danube mark a long band across western and central Europe over which ranged a very typical and very homogeneous mammalian fauna. Declining groups. — There are marked extinctions or emigrations. The absentees among the recorded mammals of this Aquitanian stage are the palzotheres, amynodonts or cadurcotheres, the entelodonts or giant pigs, the gelocids (Gelocus), as well as their enemies the carnivorous hynodonts. With these exceptions the Middle Oligocene or Stampian mammals (p. 193) probably all continue at this time. Yet it is certain that we have here Agujtanian Stage UPPER ce Fia. 84.— Upper Oligocene. Aquitanian. FRANCE.— Calcaire de 1 Celles-sur-Cher, 2 Saint-Gérand-le-Puy, in the Bourbonnais, lacustrine formation. 8 Chaveroche, in the Bour- bonnais. Conglomérat et sables de 4 Pyrimont, marnes de Challonges, in Savoy. 5 Varages, in Provence. Grés mollassique de 6 Boujac, near Alais (70-80 meters). Mollasse d’ 7 Avignon, in Rhone valley. GERMANY.— Kalke von 8 Weisenau, 9 Mombach, near Mainz. 10 Has- lach, in southwestern Germany. Kalk und Mergelbiinke von 11 Eggingen, near Ulm. SWITZERLAND. — Mollasse grise de 12 Lausanne, on Lake Geneva, fresh water with a marine band (300 meters). 18 Othmarsingen, near Zurich. Mollasse A lignites de 14 Hohe Rhonen, near Basel. SPAIN.— Marls and limestones of 15 Rubi, near Barcelona. AUSTRIA- HUNGARY. —16 Tuchorschitz (Bohemia). 17 Keutchach (Karinthia). 18 Waitzen (Hun- gary). Correlation of Depéret. only a partial picture of the Old World life of the times, because the only mammals known are those adapted to lowlands and lake and river borders. Highly distinctive are the giant anthracotheres (A. magnum), the last of this large phylum, although the smaller, short-crowned anthracotheres (Brachyodus) survive into the Miocene. Among diminutive forms the opossums or didelphids make their last recorded appearance (Amphipera- thervum) in the Old World. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 195 Mammals and birds. —The mammalian group was picturesquely de- seribed by Filhol* in 1880 in his memoir on St. Gérand-le-Puy, and other scenes in central France at this Middle Oligocene time may be imagined from Milne Edwards’ description’ of the birds of St. Gérand-le-Puy and other localities in the Allier basin. The lakes were small and shallow, sur- rounded by broad belts of marsh with characteristic vegetation. Turtles of various kinds lived in the waters, and crocodiles almost as large as the living Nile: types were a constant menace to the aquatic birds. The varied bird popula- tion finds its parallel to-day on certain lakes in the interior of Africa. Unlike the avifauna of the Upper Eocene, it begins to include a number of existing genera. The pelican, ibis, marabou, flamingo, sand- grouse, and above all the cour- oucou (trogon), the parrots, and secretary birds lent to this fauna an unmistakable African aspect. Ducks were common, cormorants (Graculus) and grebes (Colymboides) were less Fic. 85.— France in Upper Oligocene or Aquita- nian times. Dotted areas = lagoons. White = land. abundant than the gulls(Larus), Ruled = sea. After de Lapparent, 1906. which are to be seen every- where. Considering this abundant community of bird life with that of modern Africa, it is very noteworthy that no African mammals whatever have been found in any deposits of this period. The birds are forms which could more readily migrate. Probably the modern African avifauna is largely derived from that of Oligocene Europe and Asia. As noted above, the mammal fauna preserved probably presents a very incomplete picture of the manifold animal life of France at this time. Thus it seems likely that monkeys and lemurs inhabited the forests, and that bats were much more numerous than the one genus found would indicate. Horses may have existed on the northeastern plains; but no proofs have been found that they existed in Europe. Rodents were common, repre- sented by six families, namely, the now extinct theridomyids (Theridomys) and eomyids (Rhodanomys), also the squirrels (Sciwrus), beavers (Steneo- fiber), the tailless hares or picas (Titanomys). We especially note the ' Filhol, H., Etude des Mammiféres fossiles de Saint-Gérand le Puy (Allier). Bzbl. Ecole Hautes Etudes, Sect. Sci. Nat., Vol. XIX, Art. 1., 1880. 2 Milne Edwards, A., Oiseaux fossiles de la France, 1869-1871, pp. 562-570. 196 THE AGE OF MAMMALS ak Fic. 86. Diceratheres, common to the New and Old Worlds. Above: Skeleton of the Oligocene rhinoceros Cenopus occidentalis of South Dakota. Below: Restoration of the same by Charles R. Knight. Both in the American Museum of Natural History. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 197 absence of the true rabbits and hares (Leporidz), which at this time were abundant in America. The carnivores have undergone great PREVAILING MAMMALS changes _ since the Lower Oligocene. The Suillines civet-like dog Cynodictis has disappeared. Ceenotheres The canids are now represented by two more Cervuline Deer (hornless) | modern genera (Amphicynodon, Cephalogale). Giant Anthracotheres The largest dog-like forms are the amphicyons, Aceratheres now equaling the wolf or hunting dog in size, Diceratheres but not in speed; the typical members of this Tapirs race were heavier and more thickset than the Chalicotheres dogs, but more slender than the bears, with Opossums clumsy legs and a long tail. Of the smaller Amphicyonids Carnivora, the mustelid family is represented Civets by Plesictis, a small, long-bodied carnivore of Castorids (Steneofiber) the size of a marten, as well as by the otters. The mustelines are also represented by Pro- elurus. Still more striking is the presence of the fierce viverrid carnivores (Amphictis, Herpestes) of the modern civet and mongoose types. Ungu- lates were numerous, including the tapirs as well as rhinoceroses and chalicotheres. The horses are still absent. The rhinoceroses now embrace the dicera- theres and the larger aceratheres (A. leman- ense). The chalico- theres have now at- tained a larger size . Fig. 87.— Ancestral saber-tooth tigers common to the (Macrotherium). Also New and Old Worlds. Skeleton of the Middle Oligocene , : carnivore Hoplophoneus primevus of South Dakota, a fore- ic > og Ne TASU = 5 5 J fre que nting the vast runner of the great saber-tooth tiger of the Pleistocene. In swamps surrounding the American Museum of Natural History. the lake were the horn- less cervuline deer (Dremotherium and Amphitragulus); it is noteworthy that this is the last record of this hornless race in Europe. The little cenotheres, the last survivors of the anoplothere family, lived in large herds around the lake, and are found in great abundance. The suillines are represented by the aberrant pigs (Palwocherus). At Pyrimont! we obtain an imperfect picture of the animal life of the swampy Rhone valley of Savoy toward the close of the Oligocene period. 1 Depéret and Douxami, Les Vertébrés Oligocénes de Pyrimont-Challonges (Savoie). Mém. Soc. Paléont. Suisse, Geneva, Vol. X XIX, 1902, pp. 84-87. 198 THE AGE OF MAMMALS The insectivores are represented by large numbers of a small aquatic animal (Hchinogale) allied to the desmans. The beavers are also abundant here (Steneofiber eseri), animals about one-third smaller than the existing beavers. The Herbivora are the preponderating element of the fauna. Both the two-horned (Diceratherium) and the small hornless (A ceratheriwm) rhinoceroses occur. The tapirs (Paratapirus) were somewhat larger ani- mals than the Middle Oligocene Protapirus. Of the suoids Palao- cherus is the precursor of the Miocene Hyotherium; the very primitive, long-headed pig Doliocherus also occurs. The small and graceful mem- Fic. 88.— Lower Oligocene fluvio-marine formation, north of Lake Qfirun, Fayim, Egypt. Lower and upper horizons of the Arsinoitherium zone. Photograph by American Museum of Natural History, expedition of 1907. bers of the genus Ceanotherium lived in large troops in the region of Pyrimont. Oligocene suillines. — Stehlin inclines to the belief‘ that both kinds of true pigs (Propaleocherus, Doliocherus) which appear at the beginning of Oligocene times in Europe are new immigrants and not descendants of Cheromorus or of any other Eocene suillines of Europe (see p. 148). Of these Oligocene pigs Propalwocherus is regarded as the starting point of the Old World main group of true pigs with all its branches, while Dolio- cherus exhibits such striking resemblances to the peccaries (Dicotylids) of North America that Stehlin considers it very near the stem form if not the actual stem form of our Oligocene group of primitive peccaries. The 1 Stehlin, H. G., Die Siugetiere des schweizerischen Eocens, 1903-1906, p. 749. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 199 Old World Miocene pigs (Listriodon, Cherotherium, see p. 253) are at best regarded as aberrant branches of the main Old World (i.e. Propalwocherus) stem. Il. UPPER EOCENE AND OLIGOCENE LIFE OF AFRICA The epoch-making discoveries of recent years in Egypt have already been briefly referred to (p. 72), and now deserve a fuller treatment. On LEVEL OF LIBYAN DESERT BASALT FLO ARSINOITHERIUM ZONE Arsinoitherium Rhagathertum Palaeomastodon Meeritherium . Megalohyrax QUARRIE ome fragt) Mammal bone: . 1 1 J Lu Megalohyrax |— Apterodon al Ancodon . O Arsinoitherium Metaphiomys Apidium Upper bone bearing levelamd ow Li Ancodon. Ptolemaia oO Saghnatherium Phiomys hs = Pterodon Apterodon ($e AS BARYTHERIUM ZONE Barytherium Moeritherium £osiren b Zeuglodon S={Marine and €stuarine)= ZEUGLODON ZONE Zeuglodon Focetus Prozeuglodon T-EL- QURUN BEDS (Marine) —SS >= means) ie Present Surface of Lake Qirun ofa m= ad al Es ed ee ee icy RAVINE BEDS (Marine) Fic. 89.—Section through the Eocene and Oligocene formations north of Lake Qfrun, Fayim, Egypt. Arrows indicate levels richest in remains of mammals. After Beadnell, Andrews, Granger, Osborn. the southern borders of the Libyan Desert, sixty miles southwest of Cairo, lies a series of bluffs of Upper Eocene and Oligocene age, overlying the fertile basin of the Fayfim. As early as 1879, Schweinfurth discovered some bones of the great Kocene whales among the lower westerly bluffs of what may be known as the Zeuglodon Zone (Fig. 89). In 1898 came the 200 THE AGE OF MAMMALS first evidence of the existence of extinct land animals in this region, and in 1901-1905 explorations under Beadnell and Andrews of the Egyptian Survey and British Museum resulted in a series of remarkable discoveries, which were ably set forth in Andrews’ fine memoir of 1906." Supplementary explorations by the author, and Mr. Granger of the American Museum,” in 1907, and by other institutions, promise to round out our knowledge of this newly found world of African life in early Tertiary times. As shown in the accompanying section, the bluffs are sixteen hundred feet in thickness. The lower level, or ‘Zeuglodon Zone’ (200 feet) is a purely marine formation rich in remains of the primitive Eocene Cetacea (Zeuglodon and Prozeuglodon). Above these (500 feet) are marine and estuarine beds in which remains of Zeuglodon are mingled with those of fluviatile and shore-living mammals, including sea-cows (Hosiren), am- phibious animals (Meritheriwm) related to the proboscidean stock, and still larger quadrupeds (Barytherium) of unknown affinity; this may be termed the ‘Barytherium Zone’ and is believed to be of Upper Eocene age from evidence afforded partly by the animals, partly by richly fossiliferous shell layers. Above this are fluvio-marine beds (900 feet), designated as the ‘Arsinoitherium Zone,’ which yield a splendid representation of the land fauna of northern Africa in Lower Oligocene times. Beside the mammals we here discover giant land tortoises (Testudo ammon) resembling those of modern Madagascar, giant pythons (Gigantophis), ostrich-like birds (Ere- mopezus), broad-snouted crocodiles (Crocodilus megarhinus) similar to those now found in African rivers, as well as the slender-snouted gavial- like forms (Tomistoma) similar to those now found in Borneo. In the rivers beside the numerous sirenians and zeuglodont-whales there swam river turtles (Podocnemis) related to those found to-day only in South America; there were also large sea snakes (Pterosphenus), and in the Mediter- ranean Sea near by were found great floating leather-back turtles (Thalas- sochelys) closely similar to modern forms. So far as the mammals mirror their surroundings, Eocene Libya was a savannah country, partly open, partly thicketed or jungled, partly forested, of about the same temperature as to-day, fairly well watered, and subject to occasional freshets and floodings from sand-bearing rivers to the south. These old river beds of loosely compacted sand have yielded the greater part of the thousands of isolated specimens which have been taken from this region, including forty-five species of mammals, twenty-one of reptiles, and twenty-three species of fishes. The fauna as a whole shows affinities to that of the modern life of 1 Andrews, C. W., A Descriptive Catalogue of the Tertiary Vertebrata of the Faytim, Egypt. 4to, London, 1906. 2 Osborn, H. F., Hunting the Ancestral Elephant in the Fayfim Desert. Century Maga-_ zine, Vol. LX XIV, no. 6, October, 1907, pp. 815-835. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 201 Africa, Asia, and South America, also to the life of Hocene-Oligocene Europe. This assemblage, however, presents more contrasts than resem- blances to the mammalian life which existed in Lower Oligocene times on the north shores of the Mediterranean, as displayed in the phos- phorites of Quercy. The resemblances consist in the presence of small myomorph rodents (Phiomys, Metaphiomys),' and a great variety of car- nivorous creodonts be- longing exclusively to the family Hyzenodon- tide, including the three principal genera Hyenodon, Pterodon, Apterodon, also found in France. Among the even-toed ungulates, or artiodactyls, we find in northern Africa, as in Europe, several ancodonts or hyopo- tamids (Ancodus, Brachyodus) ; the aber- rant Rhagatherium of North Africa is also found in Switzerland ; there are large mam- Fic. 90.— The aberrant rhinoceros-like ungulate Arsinoi- mals (Geniohyus) re- __therium attacked by the carnivorous creodont Pterodon. 3 (Oligocene of the Fayfim, Egypt.) After original by Charles sembling the European R. Knight in the American Museum of Natural History. suillines in their denti- tion, and very diminutive forms (A pidium) resembling remotely A cotherulwm and Cebocherus of France. The very striking point of contrast with the neighboring peninsula of Europe is the absence of perissodactyls, of tapirs, horses, and rhinoce- roses of all kinds. Neither are there any higher types of selenodont artiodactyls such as we might consider as ancestral forms of the great ruminant fauna of modern Africa. This would appear to strengthen the 1 Osborn, H. F., New Fossil Mammals from the Faytim Oligocene, Egypt. Bull. Amer. Mus. Nat. Hist., Vol. XXIV, Art. xvi, Mar. 25, 1908, pp. 265-272. 202 THE AGE OF MAMMALS hypothesis that both the Perissodactyla and Artiodactyla are natives of Holarctica, or the northern hemisphere. CHARACTERISTIC MAMMALS Creodont-carnivores 5) genera Ptolemaiids Relationships unknown Myomorph rodents Anthrocotheroid artiodactyls 2 genera Suoid artiodactyls 2 genera Hyracoids, or hyraces Primitive proboscideans sub-aquatic and terrestrial Barytheres Arsinoitheres Sirenians Zeuglodonts The great arsinoitheres played the part in Oligocene Africa which is now performed by the rhinoceroses in the dark continent: they were the giant mammals of the period. The dominant feature of the head is a pair of enormous forwardly-projecting bony horn-cores over the snout, which in life were sheathed with horn, sharply pointed in the old bulls, and blunted or rounded in the calves. A smaller pair of horns are also seen to rise above the eyes. As re- stored by Andrews, a moderate-sized bull (Arsinoitherium zitteli) stands five feet nine inches at the withers. The neck is short, the limbs long, the feet short and spread- ing, terminating in five short toes adapted, like the crested grinders, to grazing. These remarkable mammals, the affinities of which are entirely unknown, were apparently con- fined to Africa. Remains of hyracoids are very numerous, indicating that they ran in herds composed either of large varieties (Megalohyrax) equaling the smaller ———— By permission of the Century Company. ——a . Fic. 91.— The extinct giant coney Megalohyrax of the Lower Oligo- cene of North Africa, together with its small successor, Hyrax, of recent times. After a drawing by Charles R. Knight. tapirs in size, or of the smaller but still more abundant Saghatheriwm. All these animals have an enlarged pair of fighting tusks, and the denti- tion throughout is remarkably similar to that of the existing hyraces, or ee eS a ee eee eee ee eee OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 203 coneys of the Sinaitic Peninsula and of Africa. The living hyraces are relatively of diminutive size. It would appear from the varied nature and abundance of these ani- mals that Africa was the chief center of their adaptive radia- tion. Still more important are the two primitive members of the order Proboscidea, Mari- therium and Palawomastodon. The former is a sub-aquatic mammal which presents its chief resemblances to the Pro- boscidea in the enlargement. of the same pair of front teeth as those which constitute the tusks g.2#, 0 Retoation ofthe ad of the prin of elephants; also in the struc- Eocene of the Fayfim, Egypt. (The eyes are rela- ture of the erinding teeth, tively too conspicuous.) After original, modeled : ; under the author’s direction, by Erwin 8S. Christman which are essentially ancestral in the American Museum of Natural History. to those of Palewomastodon. Other parts of the animal exhibit analogies to the primitive sea-cows or sirenians. The other type, Paleomastodon, appears to be directly ancestral to the Lower Miocene mastodons of Europe; in contrast with Meritherium, it probably possessed a long prehensile upper lip, a pair of spoon-shaped lower incisor teeth which opposed this lip, a pair of upper incisor tusks well developed as fighting weapons, with an enamel band on the outer = sides. * The grinding teeth are more complex than those of Meritherium and directly ancestral in form to those of Trilophodon — angusti- dens of the Lower Miocene of Europe. The accompanying Fie. 93.— Restoration of the head of the primitive pro- boscidean Palwomastodon of the Lower Oligocene of the Fayfim, models of the heads Egypt. After original, modeled under the author’s direction, (Figs. 92. 93) exhibit by Erwin 8. Christman in the American Museum of Natural = ‘ies History. the profound differ- 204 THE AGE OF MAMMALS ences between these two proboscideans, and indicate that we may look for other radiations of the proboscidean stock in Africa; possibly the river-living sirenians may prove to be one of these radiations. Certain of the paleomastodons attained an imposing size, but none of them rivaled the arsinoitheres. III. OLIGOCENE LIFE OF AMERICA Geologic conditions. — Widely contrasting with the limited and scattered deposits of Europe are the vast Badlands, or Mauvaises Terres, of the z 120 115 110 5 a ee ON Ln ea y / ° / 7 X y j / ne Ee Aes 1 ° iG Tr 5 VEX Fees No \ oe 1¢ Pp ) OLIGOCENE DEPOSITS Fre. 94.— Chief Oligocene deposits of fossil mammals in the Mountain Region of North America. 1. John Day, Oreg. 2. White River, 8. Dak., Neb., Wyo. 8. Horsetail Creek and Cedar Creek, Col. 4. Pipestone Creek and Threeforks, Mont. 5. White Buttes, N. Dak. 6. Swift Current Creek, Assiniboia. '7. Bate’s Hole, Wyo. western plains region which, as we now believe, represent the vestiges of extensive flood plains similar to those of many existing rivers in India and South America. Scattered over the surface at different points from British Columbia on the north to the Mexican plateau on the south are areas from é two to three hundred miles east of the Rocky Mountains. For the most part they overlie not the Eocene, but the worn upper surfaces of the Cre- taceous (Fort Pierre), proving that while the Rocky Mountain basin de- posits were forming, the region of the Great Plains was an open, slightly undulating country, traversed by rivers and streams. a eae ee ee ee 2. ee OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 205 The earlier theory as to the origin of these vast deposits was that they were due to great lakes whose borders were frequented by rich mammalian life. As early as 1869 Leidy' raised a doubt as to this lacustrine theory in the following words: ‘‘While the geological formation makes it appear that the fossils were deposited in ancient lakes, or in estuaries or streams connected with the latter, it is strange that they exhibit no traces of fishes or of aquatic molluscs intermingled with the multitude of relics of terres- trial animals. The single mollusc known is terrestrial, and the turtles are mostly land forms. Even mammals of decided aquatic habitat are absent. With the exception of the shore-living rhinoceros and the beaver, no am- phibious mammals have been discovered. While the fossil bones are in perfect preservation, their original sharpness of outline without the slightest trace of erosion indicates quiet water with a soft muddy bottom. . The few turtles appear to be related to the swamp-living emydians. It is remarkable that there are no crocodile remains.” Where were these creatures when the shores of the ancient waters of Nebraska and Dakota teemed with such an abundant profusion of ruminating hogs and oreodons?”’ Despite this sagacious suggestion by Leidy that the mode of preserva- tion of the animal remains did not support the lake theory, this theory was generally maintained by all geologists and paleontologists up to a comparatively recent time. Finally a number of geologists, Gilbert * (1896), Haworth * (1897), Davis’ (1900), Johnson ® (1902) began to throw more. and more serious doubts on this theory. Thus Davis observed (1900, p. 372): “Geologists have been too ready to explain the freshwater Tertiary formations of the Rocky Mountain region as lacustrine in origin. The large share of these deposits are probably due to fluviatile or other sub-aerial agencies.”’ The same author drew comparisons with the pied- mont, or flood plains of the Ganges, the Po, and the Hwangho. The cowp de grace to the lake theory was, however, given by the paleontologists, Matthew 7 (1899, 1901), Fraas * (1901) and Hatcher ° (1902), who set forth convincing reasons for the theory of fluviatile or river channel and flood 1 Leidy, J., The Extinct Mammalian Fauna of Dakota and Nebraska, Philadelphia, 1869. 2 Crocodile remains have since been discovered; see p. 185, Loomis, 1904. 3 Gilbert, G. K., The Underground Waters of the Arkansas Valley in Eastern Colorado. U.S. Geol. Surv., 17th Ann. Rept., Pt. 2, 1896, p. 576. 4 Haworth, E., Physical Properties of the Tertiary (of Kansas). Univ. Geol. Surv. Kansas, Vol. II, 1896, p. 281. 5 Davis, W. M., The Freshwater Tertiary Formations of the Rocky Mountain Region. Proc. Amer. Acad. Arts Sci., Vol. XX XV, no. 17, March, 1900, p. 372. ® Johnson, W. D., The High Plains and their Utilization. U.S. Geol. Surv., 22d Ann. Rept., Pt. 4, 1902, p. 638. 7 Matthew, Is the White River Tertiary an Eolian Formation? Amer. Natural., Vol. XXXIII, 1899, pp. 403-408; and, Fossil Mammals of the Tertiary of Northeastern Colorado. Amer. Mus. Nat. Hist., Mem. 1, Pt. 7, Nov., 1901. 8 Fraas (ed. by Osborn) on the aqueous vs. eolian deposition of the White River Oligo- cene of South Dakota. Science, n.s., Vol. XIV, 1901, pp. 210-212. ® Hatcher, J. B., Origin of the Oligocene and Miocene Deposits of the Great Plains. Proc. Amer. Philos. Soc., Vol. XLI, 1902, pp. 113-131. 206 THE AGE OF MAMMALS plain origin, with periods of backwater, lagoon, and shallow lake conditions, and even of eolian conditions. Matthew and Hatcher pointed out that the great Badlands are composed partly of coarse sandstones and con- glomerates, indicating river formations, and partly of so-called clays, indi- cating still water or xolian conditions in which horizontal banded deposits were laid down. Especially interesting is the demonstration by Matthew that the river channel sandstones contain chiefly the remains of forest- and Fic. 95.— Lower Oligocene overlying Upper Eocene horizons on the Beaver Divide at Wagon-bed Spring, near Hailey, Wyo. Diplacodon Zone (Eocene) below; Titanotherium Zone (Oligocene) above. Photograph by American Museum of Natural History, expedition of 1909. river-living animals, while the fine clays contain the remains of plains- living or cursorial animals. The accompanying panorama prepared by Osborn after a personal survey of this wonderful region in 1907 is designed to indicate how the fluviatile ‘Titanotherium,’ ‘Metamynodon,’ and ‘Protoceras’ sandstones traverse the outlying fine deposits or clays and prove the existence of great river channels from seven hundred feet to a mile in width. These rivers flowed eastward, and bore down from the mountains coarse ma- terials; they occasionally overflowed in broad shallow sheets of water, too transitory to support any of the aquatic animals. They caused such dep- ositions as are left by the annual overflows of the Nile. A picture of the plains region in Oligocene times is that of broad, gentle eastward slopes from the Rocky Mountains, plane or gently undulating OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 207 F<“ Porcupine Butte f VOLCANIC ASH LAYER 2) presi / Merycocherus LOWER MIOCENE ROSEBUD RIVER-CHANNEL CONGLOMERATES ages Promerycach Zope ~~ Steneofiber Promerycocharus Leptauchenta ld Protoceras Zz uJ oO fe) es) = ° Oreodon =~ (upper) {e) Zz UPPER NODULAR LAY 75- a ae Oreodon 1007 Le (middle) oI nN [o} a Oreodon ( lower) << TITANOT HE Titanotherium (upper) , = —— ; : Ais’ erium Titanotherium (middle) CHADRON Titanotherium ( lower) OF; 100 200 300 400 FEET a : ~ = By permission of the American Museum of Natural History. Fic. 96.— Panoramic view of the Oligocene and Miocene exposures on the south side of the White River, South Dakota. After Osborn. 208 THE AGE OF MAMMALS and not mountainous, bearing broad streams with varying channels, some- times spreading into shallow lakes, but never into vast freshwater sheets. Savannahs were interspersed with grass-covered pampas traversed by broad, meandering rivers. This land was dry in dry seasons, but was flooded in very high water periods. The materials were partly erosion products of the Rocky Mountains and Black Hills, such as true sandstones ang conglomerates, but they included also fine layers of volcanic dust, wind-borne from distant craters in the mountains, far out on the plains of Nebraska and Kansas. Scattered through these Titanotherium and Oreodon beds! are numer- ous thin layers of limestone, always of limited areal extent, rich in remains of freshwater plants (Chara) and molluses (Limnea, Physa, Planorbis), of species inhabiting swamps and small ponds. Remains of forests are found at different horizons throughout these beds, including silicified trunks of trees and seeds belonging especially to forest types (Hickoria, Celtis). Nothing like complete trunks are observed, and the impression was that of burial on stream margins where only the less destructible parts of trees would endure sufficiently long to be covered up and preserved. (Hatcher.) Prevailing mammal. types. — It will be observed that in the above de- scribed Oligocene mammals of western and central Europe, there are no plains- or upland-living types; horses are absent, the hornless deer-like forms are the gelocids and cervulines, analogous to those now frequenting swampy or forested regions. The dry ground or upland fauna, if it existed, has not been discovered. In America, on the other hand (see p. 220), both the low ground and the high ground mammals of the Oligocene are known, the former broadly agreeing in foot and tooth structure with those of Europe; the latter, in- cluding the horses and camels, are fleet, cursorial types. Thus the physiog- raphy of the plains country was varied. As this is the first glimpse of the life of the great plains of America, it is probable that many of the mammals which are found here were not new to North America, but had been resident on the Great Plains for a considerable period. Oligocene lizards. — Indications of dry land conditions in the Titano- therium and Oreodon zones of Montana are found in the presence of numer- ous lizards of a type (Glyptosaurus) which has the skull covered with tuber- culated bony plates. These animals are referred to the burrowing, nearly limbless family of Anguide, and are related to forms also found in the Eocene of the Bridger Formation of Wyoming. In the Oligocene of Ne- braska the worm-like, amphisbeenian lizards (Rhineura, Hyporhina) occur, animals now inhabiting the tropical regions of America and Africa. In addition to the evidence drawn from geology and the mammals, the 1 Hatcher, J. B., Origin of the Oligocene and Miocene Deposits of the Great Plains. Proc. Amer. Philos. Soc., Vol. XLI, 1902, pp. 113-131. 2 Douglass, E., Some Oligocene Lizards. Ann. Carneg. Mus., Vol. IV, nos. 3 and 4, 1908, pp. 278-285. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 209 Fig. 97.— Type of the Titanotherium Zone, Lower Oligocene. Above: Herd of titano- theres of the genus Brontotherium on an ancient flood plain in the South Dakota region. After original by Charles R. Knight. Below: Skeleton of the giant titanothere Brontotheriwm gigas (female). Both in the American Museum of Natural History. 210 THE AGE OF MAMMALS tortoises (Testudinata), as analyzed by Hay,' furnish important proof of prevailing dry land conditions on the great plains. How long previously such conditions had set in it is impossible to say. In the entire Oligocene and Miocene beds of the great plains only six species of water-living turtles have thus far (1907) been recorded, and these are probably from river channel sandstones, as contrasted with a very much larger number of land-living tortoises, chiefly from fine clay deposits. The upland testudi- nates include in the White River group (Lower to Upper Oligocene) eight species of land tortoises (Stylemys, Testudo). Remains of crocodiles have been recorded (Loomis) ? in river channel beds of Lower Oligocene age. Physiographic conditions. — The general conditions of Oligocene life in the plains region have already been pictured in the early part of this chap- ter (p. 179), and we may now review the characters of each subdivision of the Oligocene more in detail. LOWER OLIGOCENE, LowrR WHITE RIVER, OR CHADRON FORMATION, TITANOTHERIUM ZONE This takes us at once into one of the grandest and most famous of mammal-bearing horizons, the ‘Titanotherium Beds’ of Leidy and Hayden, e ton . FO Minato fC ae Pe: LEMANS J ee n. J ~ es 4 Fic. 98.— In the ‘ Big Badlands’ of South Dakota; Lower and Middle Oligocene. Lower : Titanotherium Zone including channel beds, a river formation. Upper: Oreodon Zone, a flood-plain. Photograph by American Museum of Natural History, 1907. 1 Hay, O. P., The Fossil Turtles of North America. Publ. Carneg. Inst., Washington, no. 75. 4to, 1908. 2 Loomis, 1904, op. cit OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 211 . OLIGOCENE Brule formation RESERVATION = = =a SEN MIOCENE OLIGOCENE —LOWER Arikaree formation / =R Of &B-U-D PLEISTOCENE \ Gee pW s\ i in] IG int erin “RW \\\ 9 ‘ \ \\\ Y : A we iN & Im FR By permission of the U.S. Geological Survey. Fria. 99.— Oligocene, Lower Miocene and Pleistocene exposures of South Dakota, Nebraska, and eastern Wyoming. After Darton and Thomson. Oblique lines = Titanotherium Zone, Chadron Formation. Dots = Oreodon and Leptauchenia Zones, Brule Formation. Horizontal lines = Prome- rycochcerus and Merycochcerus Zones, Arikaree Formation. Vertical lines = Pleistocene. Exten- sive Upper Miocene and Pliocene exposures omitted. PA We THE AGE OF MAMMALS at the very base of the Oligocene, which rest directly upon the irregularly eroded surfaces of the Upper Cretaceous. As shown in the accompanying map, this Chadron Formation (black lines) was widely distributed in South Dakota, Nebraska, and Wyoming, and extends up into British Columbia to the Swift Current Creek Formation. Again in Montana we find the Pipestone Creek, first explored by Douglass,’ which yields the mammals of smaller size, or microfauna.” Since the Titanotherium beds of the Big Badlands are mostly coarse and largely fluviatile, our knowledge of the American mammals of this stage is still rather limited except as regards the titanotheres, which are magnificently represented and undergo their entire final evolution and extinction in this short period of two hun- dred feet of deposition. The first to thoroughly explore this zone was Hatcher,* while searching for titanothere skulls and skeletons. In 1893 he divided the zone into Fic. 100.— Heads of Lower Oligocene titanotheres. Representing four contemporaneous phyla, or lines of descent of (A) Megacerops, (B) Titanotherium, (C) Symborodon, (D) Bron- totherium. After originals by Charles R. Knight in the American Museum of Natural History. three levels: a lower, characterized by titanotheres of very small size, with small horns; a middle, by titanotheres with horns of intermediate size; and an upper, by giant titanotheres, some of which exhibit magnificent horns. Osborn * subsequently showed that these dominant mammals rep- resent four phyla or grand divisions, namely: ( Titanotherium, long-headed, slender-limbed, lacking incisor teeth. Short-horned ; ; ee eae | Megacerops, short-headed, stout-limbed, with incisor teeth. ( Symborodon, smaller, lacking incisor teeth. Long-horned { : up eae | Brontotherium, larger, with incisor teeth. This polyphyletic character, or adaptive radiation of the titanotheres, affords us a hint as to varied local conditions which are also reflected in 1 Douglass, Fossil Mammalia of the White River beds of Montana. Trans. Amer. Philos. Soc., n.s., Vol. CC, 1901, pp. 1—42. 2 ITbid., New Vertebrates from the Montana Tertiary. Ann. Carneg. Mus., Pittsburg, Vol. II, no. 2, 1903, pp. 145-200. 3 Hatcher, J. B., The Titanotherium Beds. Amer. Natural., March 1, 1893, pp. 204-221. 4 Osborn, H. F., The Four Phyla of Oligocene Titanotheres. Bull. Amer. Mus. Nat. Hist., Vol. XVI, Art vii, Feb. 18, 1902, pp. 91-109. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 213 the varied structure of the horses. Titanotherium, for example, being a slender-limbed, and swift-moving animal, may have cultivated a grazing habit, while Brontotherium (Fig. 97) was a heavy-limbed, slow-moving quadruped armed with gigantic horns and teeth of a relatively short- crowned, browsing type. The titano- theres now reach the climax of their evolution and become extinct with apparent suddenness. Two members of this-family have been discovered in Europe. They are (1) Brachydiastematherium trans- sylvanicum from the vicinity of Andra- shaza Klausenburg, Transsylvania, in Hungary, comparable to our Proti- tanotherium; (2) ‘Titanotherium’ ru- melicum Toula, from Bulgaria. Titanotheriine (?Megacerops). “ FS Leptauchenia ,’ «a clays Yenita zone Protoceras sandstones” “« Oreodon clays” 7 Metamynodon sandstones” WHITE RIVER GROUP 73 be Titanotherium Clays and sandstones’ 7 CHADRON By permission of the U.S. Geological Survey. Fic. 101.—Sceale section of the Oligocene White River Group, ‘ Big Badlands’ of South Dakota. After Wortman. Probably a member of the sub-family The faunal group as a whole is exhibited in the following conspectus: CHARACTERISTIC MAMMALS Opossums Leptictids Hyznodonts True canids Mustelids Macherodont cats Surviving Eocene rodents (ischyromyids) Heteromyids Leporids (hares) Hyracodonts Amynodonts Aceratheres Diceratheres Lophiodonts Horses Chalicotheres Titanotheres Entelodonts Dicotylids Leptochcerids Anthracotheres Camels Hypertragulids (hornless) This group seems to be much richer in peris- sodactyls than that of the Lower Oligocene of western Europe, especially in the presence of the cursorial rhinoceroses or hyracodonts, of the horses, of surviving slender-limbed lophiodonts (Colodon), as well as of the great titanotheres. Beside the hyracodont and amynodont rhinoc- eroses the true rhinoceroses appear, probably both the acerathere and dicerathere ancestors, distinguished (Trigonias) by the presence of small upper canine teeth. Canopus is a still more common form. We note that the artio- dactyls are freshly allied to those of Europe through the widespread anthracotheres (A ncodus ? Anthracotherium), probably recent arrivals from the Old World. The primitive peccaries (Dico- tylide), the primitive ruminants (Hypertra- gulide), and the small camels (Camelide) are peculiarly American. Primitive insectivores (lep- tictids and chrysochlorids) occur. The opos- sums (Peratherium) survive. The Carnivora- Creodonta now include a variety of hyzenodonts, among which are forms of really gigantic size. The true Carnivora include varied canids (Daphenus and Cynodictis), the latter similar 214 THE AGE OF MAMMALS to the Old World form. The light-limbed macherodont, or saber-tooth cats (Dinictis) are characteristic, as well as the first mustelids (Bunelurus) known in this country. Every division of the mammals seems to have differentiated into its plains-living and open country types and forest- and river-living types. Fic. 102.— The Lower Oligocene cursorial rhinoceros Hyracodon. After original by Charles R. Knight in the American Museum of Natural History. Of the former, we observe, among the rodents, the leporids or hares; among rhinoceroses, the light-limbed hyracodonts; among the lophiodonts, -Colodon. The horses of the period are still polyphyletic, — small, exces- sively’ light-limbed, swift animals, models of grace and beauty. Among carnivores, both the canids and machzrodont cats are partly cursorial. The scarcely known camels were also plains-living types, although still brachyodont. The peccaries (Dicotylid) first appear here. Of the contrasting forest and lowland fauna, among _perissodactyls may be cited the titanotheres, found in the Swift Current Creek deposits of British Columbia. The forest-living tapirs are not known. Among artiodactyls, Agriocherus, a genus of oreodont, also the anthracothere Ancodus are probably river-border or forest animals. The amynodont rhinoceroses now take on a distinctly fluviatile, or river-living type; their remains are found only in the river-channel sandstones. Most of the titanotheres were browsers and frequented river borders in the lower plains. =e 7 TT a OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 215 It is striking that no trace of monkeys has been found; in fact, there is every evidence that these animals disappeared from America at or before the close of the Eocene. The small, triangular teeth of Lepto- cherus, formerly referred to the primates by Marsh and Cope, now prove to belong to a primitive surviving artio- dactyl family (Leptochoeride). Beside the leptochcerids the artiodactyls include the giant pigs or entelodonts, and pec- caries or dicotylids, the foreign anthracotheres, and the much more numerous and_ varied : 1 Fic. 103. — Skull of the Lower Oligocene titano- native oreodonts. there Brontotherium gigas (male). In the American Most important of all, the Museum of Natural History. After Osborn. hypertragulids appear, typified by the diminutive Hypertragulus and Leptomeryx. The former (Hypertra- gulus) bears some resemblance to the chevrotains (Tragulus) of southern Asia. Matthew’s recent restudy * of Leptomeryx, a member of this family, brings Fria. 104.— Contemporary Lower Oligocene mammals of South Dakota to same scale (X 75). By Charles R. Knight. A. Leptomeryx, ancestral hornless deer. B. Oreodon, a primitive browser or grazer. C. Hyanodon, the last of the creodonts. out the very important fact that it has numerous indications of remote relationship to the true ruminants and especially to the American deer 1 Matthew, W. D., Osteology of Blastomeryx and Phylogeny of the American Cervide. Bull Amer. Mus. Nat. Hist., Vol. XXIV, Art. xxvii, 1908, p. 552. 216 THE AGE OF MAMMALS (Cervidee) rather than to the Old World chevrotains (Tragulus) or New World camels (Camelidee) as had formerly been supposed. Thus in America, as in Europe, there appear in the Lower Oligocene for the first time mammals with a kinship to the cervine or deer division of the ruminants. In the Pipestone Creek beds of Montana our faunal knowledge has been especially enriched by the discovery and description of the hitherto unknown microfauna of the Titanotherium beds,! which includes archaic, tenrec-like forms, as well as erinaceids among Insectivora. These beds belong near the base of the Oligocene (Matthew, p. 201). They contain very primitive insectivores (Apternodus) with teeth of ancient type; also a diminutive opossum (Peratherium titanelix). All the rodents belong to the ischyromyid and hare divisions. None of the mice or squirrel groups are found here. Cypress Hills, Saskatchewan. — In 1883 McConnell of the Canadian Survey discovered Tertiary beds in the Cypress Hills, the northernmost mammal-bearing horizons of Tertiary times. As described by Cope? (1891) and more fully by Lambe * (1908), the fauna is of Lower Oligocene age, corresponding chiefly to that of the Lower Titanotherium beds of Montana, although the upper members may be synchronous with the Oreo- don Zone. The formation is fluviatile, or fluvio-lacustrine, and is widely scattered from the Cypress Hills to the Swift Current Creek region. Its fluviatile origin is attested by the presence of abundant remains of fishes, including the bowfins (Ama), garpikes (Lepidosteus), siluroids (/2hineastes). There are also numerous aquatic (Anosteira, Trionyx) as well as terrestrial (Stylemys, Testudo) chelonians, lizards, snakes, and crocodiles. The mammalian fauna includes opossums (Didelphys) and several species of hyzenodonts, including one animal of gigantic size (Hemipsalodon grandis), also the true canids and machzrodonts (Dinictis) characteristic of the Lower Oligocene. The mammalian fauna in general is similar to that of the Titanotherium Zone of Nebraska, South Dakota, and Montana. All the titanotheres and several of the equines as well as rhinoceroses belong to very primitive species. Of somewhat doubtful inclusion within this fauna is the supposed ancylopod (Chalicotherium bilobatum) which rests upon very uncertain evidence. White River beds of Montana and North Dakota.*— The tertiaries of 1 Douglass, E., New Vertebrates from the Montana Tertiary. Ann. Carneg. Mus., Vol. II, no. 2, 1903, pp. 145-200. 1 Matthew, W. D., The Fauna of the Titanotherium Beds at Pipestone Springs, Mont. Bull. Amer. Mus. Nat. Hist., Vol. XIX, 1903, pp. 197-226. * Cope, E. D., On Vertebrata from the Tertiary and Cretaceous Rocks of the North West Territory. Geol. Surv. Canada, Contrib. to Canad. Paleont., Vol. III, Montreal, 1891, pp. 1-25. 3’ Lambe, L. M., The Vertebrata of the Oligocene of the Cypress Hills, Saskatchewan. Canada Dept. Mines, Contrib. to Canad. Paleont., Vol. III, Ottawa, 1908, pp. 1-65. 4 Douglass, E., A Geological Reconnaissance in North Dakota, Montana, and Idaho; with Notes on Mesozoic and Cenozoic Geology. Ann. Carneg. Mus., Vol. V, nos. 2 and 3, 1909, pp. 211-288. al leita eel OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 217 Montana will be more fully described in the Miocene section (p. 279). The Lower Oligocene beds of White River age overlie the Basal Eocene or Fort Union. They were apparently deposited in streams, lakes, and marshes in ancient river valleys, cut into the Fort Union. Douglass deter- mines beds of both Titanothertum and Oreodon Zones. The Pipestone Creek beds, discovered in 1899, belong in the Titanotherium level, and have yielded a rich fauna of small mammals. Similarly, in North Dakota there are restricted areas of Lower Oligo- cene overlying the Fort Union, especially at White Butte, throughout a Protoceras Sandstones (Cc. virtel) Meétafnynodon Tartdstones ~( (e han nel) Fra. 105.—‘ Big Badlands,’ head of Corral Draw, South Dakota. Lower Oreodon Zone, and river channel beds of Metamynodon sandstones in the foreground, overlaid by the Upper Oreodon Zone and capped by the Leptauchenia Zone and river channel beds of the Protoceras sandstones. Photograph by American Museum of Natural History, 1906. section two hundred and ten feet in thickness, apparently including the Titanotherium Zone below and Oreodon Zone above. Another section affords a thickness of three hundred and twenty feet, which, however, includes the Oreodon and overlying Protoceras and Leptauchenia Zones. These White River formations in North Dakota are believed to represent deposits made in the old river valley traversed by streams originating in the Black Hills. The giant pigs, or entelodonts.— The family tree of the giant pigs has recently been studied by Peterson,’ who traces these animals from lower Oligocene ancestors (Hntelodon in Europe, Archwotherium in North America), which may have sprung alike from an unknown northern or Holarctic form. Related, are the Eocene giant pigs (Achenodon) of the Washakie and Uinta (Upper Eocene of the Rocky Mountains), too special- ' Peterson, O. A., A Revision of the Entelodontide. Mem. Carneg. Mus., Vol. IV, no. 3, May, 1909, pp. 41-158, Pls. liv—Ixii. 218 THE AGE OF MAMMALS ized in their teeth to be regarded as directly ancestral. The European Entelodon of Eymar (1847) or Elotheriwm of Pomel (1847, indet.) is re- garded as generically different from the American forms. Of the latter, Archeotherium of the Lower Oligocene, Titanotherium Zone, is believed to be distinguished from EHntelodon by its elongate snout; in brief, its greater dolichocephaly; the earliest phase (A. mortoni) gives rise to a series of species, and already in the Upper Titanotherium Zone attains an impos- ing size (A. ingens). The tuberosities of the lower jaw are strongly de- veloped in Pelonax bathrodon of the Protoceras Zone, Upper Oligocene. In the Upper Oligocene of the John Day, a massive form, Bodcherus hu- merosus, appears, distinguished by a long humerus and short feet, a slow- moving type, while the gigantic Dinohyus hollandi of the Harrison beds of Fic. 106. — Type of the Oreodon Zone. Skeleton of the Middle Oligocene oreodont Merycoi- dodon (‘‘ Oreodon”’) culbertsoni. In the American Museum of Natural History. Nebraska is more cursorial. The close of the Oligocene, or beginning of the Miocene witnessed the evolution of four great phyla of entelodonts (Pelonax, Dinohyus, Deodon, Boécherus). The distinctions of these phyla require further discrimination. The geographic range was as far east as New Jersey (Ammodon Marsh), while the geologic range is to the summit of the Arikaree beds, which are here regarded as Lower Miocene. It has been suggested by Schlosser and Winge that these animals were omnivorous or even carnivorous, which is highly improbable. The extraordinary appearance, as sketched some years ago under the direction of the present author (Fig. 76), is probably less accurate than the more recent restoration by Mills under the direction of Peterson (Fig. 83), in which the ears are placed lower down and are more drooping, in keeping with the inferior position of the external audi- OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 219 tory meatus, which is placed much lower on the sides of the head than in the pigs or peccaries. In Mills’ restoration the tuberosities on the lower surface of the jaw represent a mechanism for muscular attachment. MIDDLE OLIGOCENE, OREODON ZONE OR BRULE CLays, STAMPIAN STAGE Geology. — Immediately overlying the Titanotherium Zone in the White River Group of the Great Badlands is the Oreodon Zone, or Brule Clays, about 270 feet in thickness, and broadly distinguished as of Middle Oligo- cene age. While the Titano- therium beds are of colder, grayish tint, these Oreodon layers are warmer buffs and pinks, and, as shown in Fig. 98, are generally distinguished by long, horizontal lines or bands of similar color, which indicate the frequent recurrence of over- flow or stillwater conditions. These horizontal bands are an indication of aqueous rather than eolian deposition. Such bands are seldom seen in the Titanotherium Zone of South Dakota, although observed in Titanotherium beds elsewhere. The Oreodon beds are divided by the so-called ‘ nodular layers’ (Fig. 96) into ‘Lower,’ ‘Middle,’ and ‘ Upper,’ each Fic. 107. — Metamynodon sandstones, river with a more or less specific channel beds in the Upper Oreodon layers of South f atkordi 5 f Dakota. Photograph by American Museum of auna, and affording a series of Natural History, 1894. transitions, including arrivals and departures of animals of different kinds, similar to those which are recorded in the Eocene levels of the Bridger. Thus the Oreodon Zone alone represents a vast interval of geologic time. The lower Oreodon Zone is abruptly traversed by the ‘Metamynodon Sandstones’ (Fig. 105), coarse river channel deposits, cross-bedded sand- stones of greenish and brownish color, full of pebbles, containing especially the amphibious rhinoceroses (Metamynodon) and other lowland forms. In general, as first observed by Matthew, there is a sharp distinction be- tween the fluviatile and river-border fauna contained in these sandstones 220 THE AGE OF MAMMALS and the plains fauna contained in the clays of the Oreodon Zone.' The only explanation is that the clay and sandstone fossils represent two co- existent faunas of different local habitat.’ (i wi Fic. 108. — Skeleton of the Oligocene aquatic rhinoceros Metamynodon planifrons. (See Res- toration, page 180). In the American Museum of Natural History. After Osborn. Contrasting Plains and River-Border Mammals Chiefly Plains Perissodactyla Mesohippus bairdi, meteulo- phus, ete. Hyracodon Colodon Artiodactyla Leptauchenia Oreodon Eporeodon Poébrotherium Leptomeryx Hypertragulus Hypisodus Chiefly Riverside Mesohippus intermedius and Mio- hippus Metamynodon Cenopus Protapirus Titanotherium Agriocherus Percherus Entelodon Ancodus Anthracotherium Protoceras 1 Matthew, A Provisional Classification of the Fresh-Water Tertiary of the West. Bull. Amer. Mus. Nat. Hist., Vol. XII, 1899, pp. 19-75. > Matthew, Fossil Mammals of the Tertiary of Northeastern Colorado. Mem. Amer. Mus. Nat. Hist., no. 1, Pt. 7, Nov., 1901. : | : ed ee OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 221 Chiefly Plains Chiefly Riverside Carnivora Hyenodon Dinictis Cynodictis Hoplophoneus Hoplophoneus Daphenus Daphenus Rodentia Ischyromys Paleolagus Steneofiber Eumys Gymnoptychus Insectivora Leptictidee Of the same age are the ‘Cedar Creek’ beds of northeastern Colorado and widespread similar exposures in southeastern Wyoming, South Dakota, northwestern Nebraska, and far north in western Montana. These ex- posures are renewed proofs of the existence of vast fertile and nearly level flood plains, east of the Rockies, gently sloping eastward and traversed by stream channels or rivers which are narrower than those of Titano- therium times. The plain is chiefly forested along the river borders; but the flora is entirely unknown. Approximate homotaxis with the Stampian or Middle Oligocene of Europe is indicated by similar stages in the evolution of the anthracotheres (Ancodus), of the amynodont rhinoceroses (Metamynodon, Cadurcotherium), of the true rhinoceroses, or aceratheres and diceratheres. In both countries the Middle Oligocene is the disappearing point both of the amynodonts and of the archaic carnivores (hyzenodonts). The Oreodon beds are the favorite fossil hunting grounds of the West, because the fossils are or were extremely abundant. The mammalian fauna is also very rich, more than 150 species of mammals having been found in the Big Badlands of South Dakota alone. Since this level is much more favorable for the smaller forms of life than the Titanotherium Zone, the considerable number of new forms is partly attributable to this fact. Large herds of the small browsing oreodonts took the place of the czenotheres in Europe, and other ruminants abound in this level. The observer readily distinguishes the Oreodon stage not only by its geologic differences, but by the abundance of oreodonts and the absence of all traces of titanotheres. The Rodentia include the tree-living squirrels (Prosciurus), the ground-squirrel or semi-cursorial type (Hutypomys), and the hares, or leporids (Palwolagus); the mice, or Muride, now make their first appearance (Humys), while the peculiarly Eocene ischyromyids make their last appearance. Among Insectivora the erinaceids appear for the first time (Proterix), and the talpids or moles (Domnina), are represented. The opossums appear in numerous species (Peratherium). eet THE AGE OF MAMMALS Among carnivores the archaic hyznodonts also appear for the last time, and are represented by rather highly varied forms, animals dis- similar in size, speed, and in the proportions of the skull, ranging from the diminutive H. mustelinus to the powerful H. horridus (Fig. 81), and including also species (H. leptocephalus) which exhibit in the closure of the posterior palate a backward extension of the respiratory tract which has been regarded (Scott) as evidence of aquatic adaptation,’ but may be correlated with the extreme posterior position of the cutting or sectorial molars. At the same time the macherodont cats specialized into the fleet and slender-limbed, swift-moving Dinictis and the heavy-limbed Hoplophoneus (Fig. 87), which is transitional to the Husmilus of the Upper Fic. 109. —Skeleton of the Oligocene wolf, Daphenus. In the Carnegie Museum, Pittsburg. After Peterson. Oligocene. The canids * also vary widely from the small civet-like Cyno- dictis to powerful forms such as Daphenus nebrascensis, which equaled the wolf (Canis lupus) in size. The Herbivora which formed the prey of these carnivores are included in six families of artiodactyls and six families of perissodactyls, these two orders at the time being nearly balanced both in numbers and differentia- tion. Of the artiodactyls the camelids (Poébrotherium), which are now of slender form, begin to take a prominent part in the Plains fauna. The hypertragulids, or primitive ruminants and deer, are still diminutive and hornless forms. The oreodonts are of intermediate size and now more sharply differentiated into three phyla, (1) the small brachycephalic Lep- tauchenia being added to (2) the typical cropping or grazing oreodonts and to (8) the forest-living Agriocherus. Diminutive also are the leptocheerids. Of intermediate size are the anthracotheres, which include both the An- ‘ Scott, W. B., and Osborn, H. F., Preliminary Account of the Fossil Mammals from the White River Formation, contained in the Mus. Comp. Zoél. Bull. Mus. Comp. Zoél., Harvard Coll., Vol. XIII, 1887, pp. 152 fol. * Hatcher, J. B., Oligocene Canidae. Mem. Carnegie Mus., Vol. I, Sept., 1902. ith emer” eee see OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 223 codus and Anthracotherium of European origin; the anthracotheres exhibit no tendency to attain the great proportions displayed in the European and Asiatic forms. Of the pig-like forms the peccaries (Percherus) are less numerous than the entelodonts; the latter now begin to attain giant size (Z. ingens), thus assuming a rank similar to that of the anthracotheres in Europe. The perissodactyls are similarly differentiated into the massive river- frequenting amynodonts (Metamynodon) with hypsodont molars and power- Fic. 110.— The Lower Oligocene three-toed horse Mesohippus, a swift, light-limbed animal. To the right Dinictis, the light-limbed saber-tooth cat. After original by Charles R. Knight in the American Museum of Natural History. ful canine tusks, and the extremely long-limbed, long-footed, but still tri- dactyl lophiodonts (Colodon); these lophiodonts are of considerably larger size than the contemporary horses. From the Oreodon Zone comes the typical Mesohippus bairdi of Leidy, an extremely light-limbed equine, and there now is becoming more apparent the incipient adaptive radiation of the horses into forest-living and browsing types (Mesohippus eulophus, remotely related to the forest-living horse, Hypohippus, of the Miocene), and plains or grazing types (M. obliquidens). Some of these horses are chiefly found in the ‘Clays’ (M. ewlophus, M. bairdi, M. obliquidens), others chiefly oceur in the ‘sandstones’ of this and higher levels (M/. intermedius, M. validus, M. gidleyi). The tapirs (Protapirus) are rare. The fleet-footed cursorial rhinoceroses, or hyracodonts, are numerous and characteristic of this horizon. As in Europe the true rhinoceroses are clearly divided into the dicerathere, or two-horned, and the acerathere, or hornless, series. 224 THE AGE OF MAMMALS UprerR OLIGOCENE OF THE WESTERN PLAINS AND OF THE MOUNTAIN REGION OF OREGON The Upper Oligocene of America broadly corresponds to the close of the Stampian and the Aquitanian stages of Europe. In both countries it is characterized negatively by the absence of the hyzenodonts, the last of the archaic Mammalia, as well as of the amynodonts or amphibious rhi- noceroses. Especially characteristic are various evolution stages of the pair- horned rhinoceroses (Diceratherium), which are now armed with a trans- versely placed pair of horns on the ends of the nasal bones. Another common form which makes its first appearance in both the New and Old Worlds at this time is the primitive beaver or castorid (Steneofiber). It is difficult, however, to draw close time parallels between Europe and America because of new and plainly evident faunal divergence. Of the six families of American artiodactyls only the anthracotheres are rep- resented in Europe, and that by very different forms from those in America. Of the four families of American perissodactyls both the hyracodonts and the horses are absent in Europe, although the rhinoceroses and tapirs are represented by somewhat similar evolution stages. Of the ancylopods, or chalicotheres, the Moropus of Oregon still awaits close comparison with the Macrotherium of France; the wrist, or carpus, of Moropus is the more primitive. The Upper Oligocene of western America is clearly divided into Early, Middle, and Later, or first, second, and third faunal phases, the former being seen in the upper levels of the White River group of Dakota, which contain a continuation of the Plains fauna, while the second, as displayed in the John Day Valley of Oregon, gives us a renewed glimpse of the mountain fauna and corresponds most closely with the true Aquitanian of France. The third is again observed on the Great Plains of Dakota, is slightly sub- sequent to St. Gérand-le-Puy in age, and is by many regarded as the base of the Miocene. Turrp PuHase.— Upper John Day of Diceratheres very numerous. Promery-_ Oregon. Lower Harrison, Rosebud, and cocherus appearing. Arikaree of the Great Plains of Dakota. Seconp Puase.— Middle levels (Di- Diceratheres with well-developed horns. ceratherium Zone) of the John Day For- Chalicotheres in the Moropus stage. mation of Oregon. First Puase. — Upper part of White Diceratheres with very rudimentary River Group of South Dakota, Leptau- horns. Cynodictis and Hyracodon chenia and Protoceras Zones. still surviving. Leptauchenia. OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA Zao First Phase of the Upper Oligocene, Leptaucheniva—Protoceras Zone Geologic conditions. — The upper part of the Brule Clays of the White River Group in the Great Badlands immediately and conformably overlie the Oreodon Zone. Correlated with these are widespread deposits in northeastern Colorado and in North Dakota, indicating a continuation of Fic. 111.— The Upper Oligocene four-horned ruminant type of the Protoceras Zone. Above: Protoceras chased by the light-limbed saber-tooth Dinictis. After original by Charles R. Knight. Below: Skeleton of Protoceras celer. Both inthe American Museum of Natural History. 226 THE AGE OF MAMMALS the wide flood plain conditions. atentuay 159. — Chief Pliocene and Upper Miocene fossil mammal deposits of western North 8. Ogallala, Kan., Nebr. 4. Snake Creek, (See text for horizons.) With these doubts in mind as stimulating to further research, the follow- ing ascending arrangement of the best known formations is set forth provisionally : Peace Creek Formation of southern Florida, Loup River, of eastern Ne- braska Blanco Upper Pliocene, or | Lower Pleistocene Formation, Staked Middle Pliocene | Plains, or Llano Estacado, of Texas Virgin Valley and Thousand Creek of Nevada Snake Creek beds, Nebraska ) Rattlesnake Formation, John Day Valley, Oregon Alachua Clays, northern Flor- ida. Republican River Formation, | northern Kansas and Ne- braska. western Lower Pliocene Lower Pliocene, or Upper Miocene Elephas? columbi and Equus Zone Elephas imperator and Equus Zone Glyptotherium Zone, Rhinoceros extinct or undiscovered Ilingoceros Rhinoceros surviving Neotragocerus Zone, Rhinoceros surviving Alticamelus surviving Peraceras Zone, Rhinoceros very abundant Peraceras Zone Zone, Zone, Rhinoceros 342 THE AGE OF MAMMALS It is important to note that Matthew and Merriam have compared tie ‘Snake Creek’ and ‘Virgin Valley’ faunas with that of Pikermi, or the Upper Miocene of Greece (p. 267). It is obviously premature to attempt to correlate these subdivisions with the Pliocene stages of Europe, yet there seems to be a broad correspondence in America with the divisions of the ‘Older Pliocene Fauna’ and ‘Newer Pliocene Fauna’ of the Old World. As in all other epochs, subdivisions will be finally made with clearness and exactness through the successive extinctions of older forms and the successive arrivals of newer forms. Pending this more exact research of the future, the following provisional subdivision may be offered: Provisional Subdivision of American Pliocene Life Lower Pliocene Rhinoceroses aceratherine, teleocerine ‘Giraffe’ or browsing camels True or grazing camels Earliest Cavicornia Browsing horses Grazing horses Long-jawed mastodons Tapirs Middle Pliocene Rhinoceroses extinct Browsing horses extinct Grazing horses of Proto- hippus, Pliohippus, and Hipparion type Gigantic browsing camels Grazing camels Short-jawed mastodons Upper Pliocene Elephants (Elephas) Grazing and monodactyl horses (Hquus) Browsing camels extinct True grazing camels and llamas only Mastodons disappear in the western plains re- gion Tapirs disappear in the western plains region Climatic and Physiographic Conditions Great Plains. — There is evidence, both in the sandy nature of the deposits in the Great Plains region, in the extinction of browsing types of horses and camels, and in the survival of grazing types in the same fam- ilies, of increasing aridity in the Western plains and mountain region. This was probably accompanied by more widely prevailing summer droughts and by the contraction of the streams during the dry season. It is cer- tainly significant that the rhinoceroses, brachyodont or browsing horses, and giraffe or browsing camels successively disappear. In the early Pliocene or in the close of the Miocene we find proofs (Sternberg!) of the existence of great herds of large land tortoises moving slowly across the plains. Their presence in such large numbers is in itself proof of arid conditions, and it is an interesting bit of collateral testimony from palseobotany that seeds, found within a fossil skull of one of these animals, belong to a species of plant (Tithymalus willistoni) which, according to Cockerell,? indicates an open, relatively arid, although not strictly desert country. 1 Sternberg, C., Letter. 2 Cockerell, T. D. A., Letter to the author, April, 1909. —————————- = THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 343 California. —In the Pliocene of the Pacific coast! a change to colder conditions is indicated both by the disappearance of warm-temperate types of plants and by the colder character of the salt water fauna, as well as of that found in the freshwater Pliocene lake beds. The whole west coast of North America was rising and the shore receding westward; the waters of the Pacific no longer reached the foot of the Sierra Nevadas, nor even the great central valley between the Sierra Nevadas and the Coast Range; but elevation was not uniform, for valleys of the coast ranges that had been eroded during the Miocene were filled with sediments during the Pliocene; the enormous deposits to a depth of 3,000 feet of the Great Valley be- tween the Sierras and the Coast Range belong partly to the Pliocene and partly to the Quaternary, an area wholly of fluviatile origin. Thus during the Pliocene the Sierra Nevadas were elevated, and California at that time was very much like the California of to-day; with the great moun- tain ranges of the Sierras on the east, the long, broad valley — in many cases covered by freshwater lakes —in the center, and on the west the long, low Coast Range. The Pliocene Flora The eastward trend of the deciduous tree flora of Europe is a most significant fact. It has been pointed out above that the Miocene and Pliocene forest trees of Europe become the modern forest trees of our Cen- tral and South Atlantic states. With the flora in late Tertiary times there came certain faunal waves. Unfortunately nothing is known of the flora of the Great Plains region nor of the central mountain region, and we must rely upon observations made in California, from which only indirect conclusions can be drawn. Flora of California. — Here we must rely upon the earlier notes of Lesquereux (1859-1888) and of Turner (1891). Plants of the auriferous gravels of the Sierra Nevada? collected in Nevada County, California, on the thirty-ninth parallel indicate a temperature a few degrees higher on the average than that of middle California of the present day; in other words, they represent a latitude a few degrees farther south. Thus in Nevada County on the thirty-ninth parallel in Pliocene times there lived palms similar to those which now flourish in California on the thirty-fourth parallel. Pliocene palms are, however, very rare, only a single specimen of a sabal being found in the whole collection from Nevada County. The prevalence of a warmer climate than the present in Pliocene times seems to be indicated by oaks of Mexican type and by species of figs (Ficus), but this is counterbalanced by the presence of the birch (Betula), 1 Smith, J. P., Salient Events in the Geologie History of California. Science, n.s., Vol. XXX, no. 767, 1909, pp. 346-351. 2 Lesquereux, L., Report on the Fossil Plants of the Auriferous Gravel Deposits of the Sierra Nevada. Mem. Mus. Comp. Zoél. Cambridge, Mass., Vol. II, 1882. 344 THE AGE OF MAMMALS the beech (Fagus), the elm (Ulmus), which are all characteristic northerly types. We conclude that the Pliocene climate in this region was like that of the Gulf of Mexico, or zone of the live oak, at the present time. It is likely that the region of Chalk Bluffs, Nevada County, in Pliocene times was sheltered by western ranges of mountains against the influence of Pacific fogs; at all events, the absence of conifers seems to indicate a drier climate. A very striking feature of this flora is that which it possesses in common with the Pliocene flora of central Europe, namely, that it contains alarge number of trees which no longer grow on the Pacific slope of North America but are now confined to the Atlantic slope. Among these are species of the sweet gum (Liquidambar), of the magnolia, of the prickly ash (Zanthoxylum), and of the holly (lez). Some indication of the general age of this flora is found in the fact that out of forty-two species, twelve are closely allied to Miocene types, while thirty are more closely related to the present flora, especially of the Eastern or Atlantic States. The conifers, including the sequoias, which are now the most conspicuous element of the Sierras, did not exist, or at best were very rare, in Pliocene times in California (Lesquereux, 1882). The most recent contribution to the Plocene flora of California is that of Turner,’ who records the following plants of Kirker Pass, California, latitude 38°, as of Pliocene age: the date plum (Diospyros), the magnolia (Magnolia), the laurel (Laurus), and the viburnum (Viburnum). The same author notes that the flora from Corral Hollow, California (latitude 38°), referred by Lesquereux to the Miocene, is, however, probably of Pliocene age, as it is found associated with Pliocene shells. This flora includes horse- tails (Hquisetum), sequoias (Sequoia), yews (Tazites), alders, chestnuts, willows, poplars, planes, laurels, cinnamons (Cinnamomum), myrtles (Myr- tus), red bays (Persea), and sumac (hus). Sirenians on the Pacific coast.*— Other indications of mild climatic conditions are found in the presence of mammals remotely allied to the manatees and dugongs of the present equatorial belt. The remarkable littoral or marine mammal known as Desmostylus derives its name from the clusters of rounded and heavily enameled columns which constitute its grinding teeth. The muzzle is slender and tapering, and armed with one pair of incisors in the upper jaw and two pair in the lower. It is a large animal, the skull being eighteen inches to two feet in length. According to Merriam it is found only in marine formations of Pliocene age. It cer- tainly inhabited both the eastern and western shores of the Pacific coast; remains have been found in California, Oregon, and Japan. 1 Turner, H. W., 1891. Geology of Mount Diablo. Bull. Geol. Soc. Amer., Vol. II, 1891, pp. 396-397. 2 Marsh, O. C., Notice of a New Fossil Sirenian, from California. Amer. Jour. Sct., Vol. XX XV, 1888, pp. 94-96. THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 345 Flora of the Eastern states. — Lesquereux! also described a flora from Graves County, Kentucky (latitude 37°), which he believed to be of Pliocene age, including the fig (Ficus), laurel (Lawrus), soapberry (Sapindus), and the oak (Quercus). In the Pliocene of Bridgetown, New Jersey, the following plants have been found: the sweet gum (Liquidambar), laurel, and poplar. One of the earliest of the numerous contributions of the same author is that on the supposed Pliocene flora collected near Somerville, Tennessee.’ This flora finds its relatives at the present time on the southern shores of Florida and islands of the Gulf of Mexico; there are only four plants refer- able to existing species. It includes the laurel, the wild orange tree (Pru- nus) now found in the Bahamas and near the coast of the Carolinas, the oak of a species now found along the coast of Florida, the beech, a species of more northern range, and the willow. Late MIocENE oR EARLY PLIOCENE In every branch of life the fauna from northwestern Kansas to Florida is a continuation and evolution of the typical Miocene fauna of North Amer- ica. Perhaps it is Miocene, for there are no new elements. The clawed perissodactyls or chalicotheres are absent or undiscovered, while the oreo- donts (Merycocherus, Merychyus) are becoming rare; conditions were either becoming unfavorable for these forms in this region or the entire phylum was dying out. The rarity of the browsing horses is an indication of con- ditions unfavorable to the older brachyodont browsing types; a few remains - of these animals are, however, still found. It is important to grasp clearly the fact that the grazing horses are now in a highly polyphyletic condition. The chief formations in which these late Miocene or early Pliocene early types of mammals occur are the following: 4. Rattlesnake Formation of John Day Valley, Oregon. 3. Republican River Formation of northwestern Kansas. 2. Alachua Clays or Archer Formation of northern Florida. 1. Ogallala Formation (typical) Darton, of southwestern Nebraska. Late Miocene or early Pliocene times in North America were character- ized by the survival of the last members of the great family of oreodonts, which are thus far represented only by fragmentary specimens of the char- acteristic Miocene genera Werycocherus and Merychyus. Among the peris- sodactyls the browsing or forest horses (Hypohippus) still survive but are also becoming rare; they are represented by forms with somewhat longer teeth than those of the Middle Miocene. Of the grazing horses the char- ! Lesquereux, L., Recent Determinations of Fossil Plants from Kentucky, Louisiana, Oregon, California, Alaska, Greenland, etc., with Descriptions of New Species. Compiled and prepared for publication by F. H. Knowlton. Proc. U.S. Nat. Mus., 1888, pp. 11-38. 2 Lesquereux, L., On Some Fossil Plants of Recent Formations. Avner. Jour. Sci. and Arts., 2d Ser., Vol. X XVII, May, 1859, pp. 359-366. 346 THE AGE OF MAMMALS acteristic horses of the Miocene Merychippus stage, with grinding teeth of intermediate length, still survive in almost equal numbers with the more progressive grazing horses, Protohippus, Pliohippus, and Neohipparion. The rhinoceroses are represented by the teleocerine and aceratherine phyla, both of which reach a high degree of specialization. Of these the aceratheres or hornless rhinoceroses are represented by species of Aphelops comparable in evolution to the Aceratherium blanfordi of the Pliocene of Asia as well as by the short-headed Peraceras. The teleocerine rhinoceroses, which are also believed to survive in the Pliocene of Asia, although extinct in Europe, attain their maximum evolution and size, and are present in great number and variety. The aberrant perissodactyl chalicotheres have apparently disappeared in North America, though it is possible that some of these animals will be unearthed by future exploration, since they are believed to have survived in Asia in Pliocene times. Indicative of the Upper Miocene rather than of the Lower Pliocene age of this fauna is the fact that the trilophodont and tetralophodont mastodons still retain the long lower jaws or longirostral character of the Miocene mastodons of Europe and America, whereas the Lower Pliocene mastodons of Europe are referred to the short-jawed species M. arvernensis; this specific reference, however, may not be correct, so that too much stress should not be laid upon this single feature. Among the camels Pliauchenia is now the characteristic genus; this is a typical grazing camel with affinities to the llamas of South America, as the name indicates. We also find surviving the short-limbed or grazing camel Procamelus. The browsing or giraffe camel (Alticamelus) still occurs. In the earliest of these supposed Pliocene formations, namely, the ‘Re- publican River’ of Kansas and ‘Alachua Clays’ of Florida, we have dis- covered no evidence of the existence of the Cavicornia or hollow-horned ruminants of the Old World type. The older formations, therefore, contain rhinoceroses, but do not contain, apparently, the antelopes or Bovide. The Alachua Clays or ‘Archer Beds’ of Florida These clays were so named by Dall in 1885.1. They had been referred by some authorities to Upper Miocene, by others they had been regarded as late as Phocene or even Pleistocene. They appear on the western anti- cline of the higher portions of Alachua County (Fig. 160), along the banks of many rivers and streams, occurring in sinks, gullies, and other depres- sions, in rocks of successive age. The clays are of a bluish or grayish color, and extremely tenacious. The deposits were believed by Dr. J. C. Neal (1883) to have occurred along the margins of an ancient lake, which he named Lake De Soto. The existence of such a Pliocene lake or series of 1 Dall, W. H., and Harris, G. D., The Neocene of North America. Bull. U.S. Geol. Surv., no. 84, 1892. -— THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 347 lakes is indicated by such scanty evidence as is here afforded. Whether such a lake existed or not is less important than the conclusion reached by Dall in his report of 1892' that the beds underlying the Alachua Clays at certain points are not of Miocene but of early Pliocene age. The same author (op. cit., p. 130) con- cludes, ‘“‘ While the determination of the precise epoch of the deposition of Fic. 160.— Geological map of Florida showing the area of distribution of the principal Czenozoic exposures and the location of the Alachua Clays (Lower Pliocene) and Peace Creek beds (Upper Pliocene or Pleistocene). Solid black = Eocene; ruled = Miocene; dotted = Pliocene ; white = Pleistocene. After Dall, 1890. these remains in the clays may be regarded as still a desideratum, we may be permitted to conclude with some confidence that at least they are not Miocene.” Among the first to notice the mammalian remains in these clays was Dr. Neal. They were first thoroughly examined by Dr. Joseph Leidy, who concluded that there were no species identical with those of the so-called ‘Loup Fork’ horizon of the West. But the more exact studies published in the names of Leidy and Lucas in 1896? led to the contrary opinion that these animals are in part specifically identical with those of the Republican River Formation of western Kansas. While this conclusion is based upon 1 Op. cit. pp. 93, 133. 2 Leidy, J. (Lucas, F. A. ed.), Fossil Vertebrates from the Alachua Clays of Florida. Trans. Wagner Free Inst. Sci. Phila., Vol. IV, Jan., 1896. 348 THE AGE OF MAMMALS rather imperfect specimens, very little doubt remains of the substantial similarity in the age of these faunas. We discover here especially the short- footed or teleocerine rhinoceroses of the species 7’. fossiger. There are also remains of a long-limbed, hornless rhinoceros (Aphelops malacorhinus). Mingled with these are found hipparions (H.ingenuum). The proboscideans, or mastodons, are.represented by M. (?Trilophodon) floridanus, a species with long, narrow grinding teeth, somewhat akin in their proportions to those of M. angustidens of Europe. There are also remains of a number of camels, including a giant form provisionally referred to Procamelus, but possibly representing the giraffe camel Aliicamelus. The deer family is rep- resented by teeth provisionally referred to the Virginia deer Odocoileus, but probably representing an ancestral stage of this animal. The remains of a tapir and of a Megatheriwm are also attributed to this same zone (op. cit. p. x), but are probably of more recent age. The above list of mammals is that recorded from a point ten miles east of Archer, hence these are also known as the ‘Archer Beds.’ The appear- ance of the bones suggests that the animals were mired and then scattered by predatory Carnivora. Ashes and burnt clay were found beneath some of the bones, but there is no sufficient evidence of human agency in this; the fire may have been due to lightning, a frequent occurrence in Florida at the present time. The longitudinal splitting of the long bones, sometimes observed, may be due to the penetration and growth of roots in the hollows of the bones rather than to the agency of man. These details have been dwelt upon at some length because it seems that here we have a source of positive evidence as to the survival of the teleocerine rhinoceros fauna in the southern United States into Pliocene times. A much newer or Upper Pliocene fauna is that mistakenly attributed to the Alachua Clays from Ocala, Marion County, Florida, a fauna containing Elephas (E. ?columbi), horses (E. fraternus), llamas (Auchenia), and saber- tooth tigers (Macherodus). This ‘Ocala’ fauna corresponds rather with that of the Upper Pliocene or Lower Pleistocene Peace Creek Formation of south central Florida. It may prove that this Florida fauna is ‘homo- taxial’ rather than ‘synchronous’ with the Republican River and succes- sive faunas of the Western plains region, which we shall now examine. The ‘Republican River’ of Kansas. Peraceras Zone Here we discover a very rich mammalian fauna resembling that of the Alachua Clays in the presence of the rhinoceroses Teleoceras fossiger and Aphelops malacorhinus, and also containing the very characteristic rhi- noceros Peraceras, which is believed to be an acerathere, or hornless. The typical deposits "are 100 feet in thickness and extend along the Republican River of northwestern Kansas; they are part of the ‘Loup Fork’ as described by Cope and other authors. THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 349 The famous ‘ Long Island Quarry’ of Phillips County, Kansas, belongs in the Republican River phase, and is said to be a river channel formation cut through the mass of the flood plain Republican River deposits. It was Fie. 161.— Old and New World short-limbed or teleocerine rhinoceroses of the Upper Miocene or Lower Pliocene. Above: Restoration of Teleoceras, represented in a Florida envi- ronment, from the original by Charles R. Knight. Below: Skeleton of Teleoceras fossiger from the ‘ Long Island Quarry,’ Kansas. Both in the American Museum of Natural History. discovered by Charles H. Sternberg as long ago as 1882, and has yielded remains of hundreds of teleocerine rhinoceroses of the species T'eleoceras fossiger. It also contains species of Alurodon, of Pliohippus (large), Pli- auchenia vera (a small animal), of Merycodus, all animals characteristic of 350 THE AGE OF MAMMALS the main mass of the ‘Republican River’ Formation. Several museums have secured materials of T’eleoceras from this quarry sufficient to assemble the scattered bones into complete skeletons. The skeleton mounted in the American Museum of Natural History is shown in Fig. 161. The rhinoceros bones lie on the bottom layer of the ‘Quarry,’ mingled with sand about two feet in thickness; the heavy short bones of the feet and limbs lie at the — very bottom; the skulls, arch bones, and vertebre lie higher up. For this reason Sternberg is convinced that this was a quicksand deposit. Some miles to the east is another locality in which remains of rhinoceroses and mastodons were found associated with those of large land tortoises (p. 342). As described by the last-named explorer, these tortoises were em- bedded together in a space 150 feet in length and some four feet in thick- ness; they were all found in normal position with plastron down, the heads and limbs attached. There is thus considerable evidence that this was part of a great assemblage of tortoises which had been overwhelmed by a sandstorm and died where they were entombed.! Another interpretation, by Hay, is that these reptiles had burrowed into the sand to hibernate; but this would hardly account for their facing in the same direction. Characteristic Lower Pliocene Mammals Multiple phyla of horses. — The Great Plains at this time were covered with great herds of horses of many different kinds. The browsing section is represented by Hypohippus, the last representative of the ancient anchi- therine phylum of horses, with three toes and short-crowned teeth adapted to browsing. It is distinguished by nearly perfect transverse crests on the grinders, somewhat like those of early paleotheres. The protohippine section as distinguished by Gidley? includes horses with three toes and long-crowned teeth, adapted to grazing; it subdivides into more primitive forms with subhypsodont teeth, such as Merychippus, and more progressive forms with long-crowned, well-cemented teeth, such as Protohippus and Pliohippus. The two latter animals are distinguished by the diverse characters of the preorbital fossee on the sides of the face. In Protohippus these two fossze are shallow, without sharply defined bor- ders, while in Piiohippus there are two large and partly confluent fosse, or depressions in front of the orbits, with sharply defined posterior borders. It is generally believed that the true horse (Hquus) has descended from some more conservative or central forms, like Protohippus, but the species bridg- ing the transition between Protohippus and Equus still await discovery. A fourth and distinct line of Pliocene horses is that which contains the hipparions (Neohipparion), in which the antero-internal pillar of the pre- molars (protocone) is completely separated from the transverse crests. 1 Sternberg, C. H., Letter. 2 Gidley, J. W., Revision of the Miocene and Pliocene Equide of North America. Bull. Amer. Mus. Nat. Hist., Vol. XXIII, Art. xxxv, Nov. 26, 1907, pp. 865-934.. THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 351 These hipparions, in America at least, include the extreme desert-living types. The American group of hipparions, or Neohipparion, differ from the hipparions of Europe and Asia in several characters: (1) the anterior pillar of the upper grinders is relatively larger and elliptical in cross section; (2) the enamel foldings are comparatively simple; (3) the limbs and feet, so far as known, indicate a more slender construction of the long bones and especially longer proportions of the metapodials. The skeleton of N. whit- ney (Fig. 123) was discovered by Mr. H. F. Wells of the American Museum expedition of 1902 in the Upper Miocene or Lower Pliocene deposits on Little White River near Rosebud Agency, South Dakota; the little cluster of animals was huddled together as if they had perished in a desert storm. It consisted of the superbly complete skeleton of an adult mare associated with incomplete skeletons of five other younger individuals undoubtedly of the same species. The age of this type (NV. whitney?) is quite probably Lower Pliocene.* The increasingly arid conditions of climate were probably accompanied by an extension of the areas of the dry grassy plains and uplands over which these quadrupeds roamed, the hard conditions of the soil hastening the transformation from the tridactyl into the monodactyl condition. Multiple phyla of rhinoceroses. — We have evidence also of the existence of four and possibly of five contemporary phyla of rhinoceroses.?. As among the horses, surprisingly primitive persistent forms mingled with the most highly specialized. The polyphyletic character is also attributable to the intermingling of American and Eurasiatic strains. (1) The first phylum found among the aceratheres began with Cenopus persistens in the Middle Miocene and is continued into the C. brachyodus of the Upper Mio- cene; the former species is slender, long-headed, with short-crowned teeth and primitive feet; the skull proportions are little changed from the Oligo- cene type; all these animals are small. (2) A second phylum includes a number of large, long-headed, long-limbed aceratheres with brachyodont teeth; these animals are closest to the Miocene aceratheres of Europe; they include the A. ceratorhinus and A. montanus found by Douglass in the Upper Miocene of Montana; the nasals are long and tapering and exhibit in the males a diminutive terminal horn. (3) A third phylum apparently, introduced by the Aphelops megalodus of the Middle Miocene, is mesati- cephalic, with smooth nasals, with a high occiput inclined forward; it per- haps runs into the long-limbed A. malacorhinus of the Lower Pliocene. (4) Then comes a phylum of extremely broad-headed aceratheres, perhaps 1 Gidley, J. W., A New Three-toed Horse. Bull. Amer. Mus. Nat. Hist., Vol. XIX. Art. xiii, July 24, 1903, pp. 465-476. * Osborn, H. F., New Miocene Rhinoceroses with Revision of Known Species. Bull. Amer. Mus. Nat. Hist., Vol. XX, Art. xxvii, Sept. 24, 1904, pp. 307-326: also, Douglass, E., Rhinoceroses from the Oligocene and Miocene Deposits of North Dakota, and Montana. Ann. Carnegie Mus., Vol. IV, nos. 2 and 3, 1908, pp. 256-266. 302 THE AGE OF MAMMALS introduced by A. planiceps of the Middle Miocene, and extending into the brachycephalie Peraceras superciliosus of the Lower Pliocene; in the latter animal the premaxillaries are weak and there are no superior canines; the hornless and pointed nasals resemble those of the aceratheres of Europe. (5) The most distinctively Old World form constitutes a fifth phylum; this is composed of the short-footed ‘Teleocerine’ (Teleoceras) rhinoceroses which now attain very large dimensions; the males are armed with horns placed at the very tip of the nasals; there is no evidence of the further evolution of the second or median frontal horn, which is observed in the Middle Miocene ancestor, 7’. medicornutus; although distributed over the entire northern hemisphere, these animals were clumsy, slow-moving, and resembled the hippopotamus in their proportions; it is not improbable that they largely frequented the sluggish rivers of the period. Tapirs. — Tapirs still survive, but are very little known, being repre- sented by the single species Tapiravus rarus. Even-toed mammals. — The artiodactyls of the period include the sur- viving oreodonts, the browsing and grazing camels, the ancestral American cervids, the merycodonts, and the peccaries. Among the camels, Pliauchenia, an animal characterized by the presence of only three premolars in the lower jaw, but in other respects showing much resemblance to Procamelus, is the most typical form. The Upper Miocene Procamelus is still present and abundant, and there are evidences in this formation of the existence of the giraffe or browsing camels (Alticamelus). The merycodonts are still represented by Merycodus, which, it will be re- called, is a delicately formed grazing type, with a skeleton analogous to that of the pronghorn antelopes, but with deciduous antlers of the American deer type. The true American procervids are represented by Blastomeryx, an animal little known at this stage, but probably provided with simple, branched antlers. The peccaries are represented by Prosthennops. Rodents. — Among the rodent fauna it is interesting to note the presence of Hucastor, closely related to if not identical with Dipoides, a rodent also ob- served in the Phocene of Asia; it is possibly ancestral to the Castoroides of our Pleistocene, and it should be compared with the Sigmogomphius of the Pliocene of California. The peculiarly American family of Mylagaulide is now represented by Mylagaulus, a remarkable horned gopher (as discovered by Matthew), and by the still more specialized Epigaulus. These animals as a whole! seem to have been especially adapted to digging, for which habit they were far better equipped than any of the existing gophers. The highly modified feet and unusually small orbits suggest that they may have lived almost exclusively underground. Of what use could the horns have been to a burrowing rodent? They may prove to be sexual characters. 1 Gidley, J. W., A New Horned Rodent from the Miocene of Kansas. Proc. U.S. Nat. Mus., Vol. XXXII, June 29, 1907, pp. 627-636. THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 353 If not, it seems not improbable that they served as accessories to the great claws to assist in rapid digging. The duplicidentate rodents are represented by the true hare (Lepus). Lower Pliocene mastodons. — 'The giant forms of the period are the long- jawed, tetralophodont mastodons of the species Tetralophodon campester and T. euhypodon, both described by Cope. In the second species, T. euhypodon,' the symphysis of the jaw is abbreviated when we consider it in relation to the large size of the inferior tusks, yet it cannot properly be called ‘brevirostral’; the superior tusks are compressed distally; the in- ferior tusks are large, cylindrical, and retain the enamel band. The other species, 7’. campester, embraces animals of larger size, with a very long symphysis in the lower jaw, t.e. of more primitive ‘longirostral’ propor- tions; the intermediate molars are tetralophodont, and the sixth molar has Six cross rows of tubercles, and a heel. Attention has been called above to the fact that the Lower Pliocene mastodons of Europe embrace both the trilophodont and tetralophodont types, and are believed to be short-jawed, or brevirostral, although this is not to the present writer’s knowledge certainly known. Carnivores. — The carnivorous enemies of this large herbivorous fauna are still very imperfectly known. Among the canids there are two species of Ailurodon. The Alurodon was as large as the modern wolf, but had a short, heavy, mastiff-like head, and was distinguished from any living canids by the cat-like construction of the carnassial teeth. There is some, although not conclusive, evidence of the existence of an animal related to the bear-dog (Dinocyon) and known as Borophagus. The survival of these animals throughout the Pliocene of America as well as of Asia is rendered probable by the occurrence of Dinocyon limb fragments in the Middle Pliocene deposits (Blanco) of Texas. There is also some evidence of the existence of true dogs of the genus Canis from rare and fragmentary material. LoweER PLIOCENE, LATE PHASE Snake Creek Formation (Ogallala) of Western Nebraska, Neotragocerus Zone A more recent phase of the Lower Pliocene mammalian life of the region of western Nebraska has recently been revealed in the discovery by an American Museum party under Matthew and Cook?’ of the remains of a large and varied fauna, including no less than fifty species of mammals which are In many respects intermediate in evolution between those of the 1 Cope, E. D., The Proboscidia. Amer. Natural., Vol. XXIII, no. 268, April, 1889, pp. 191-211. 2 Matthew, W. D., and Cook, H. J., Pliocene Fauna of Western Nebraska. Bull. Amer. Mus. Nat. Hist., Vol. X XVI, no. 27, Sept., 1909, pp. 361-414. 2A 354 THE AGE OF MAMMALS ‘Republican River’ stage above described and of the Middle Pliocene, ‘Blanco’ stage, of Texas. The exposures in which this rich fauna occurs lie along a sand hill region, or crest of the divide between the Niobrara and Platte rivers in Nebraska, near the headwaters of Snake Creek, which gives the name to this formation. It is an outlyer of the ‘Ogallala’ of Darton, a formation which is typically composed of clean sand with a considerable amount of gravel; the Snake Creek is to be regarded as a local facies of the Ogallala. The bones occur , +, eee ava ke ge Fia. 162.— On the plains of western Nebraska. Miocene (Sheep Creek beds) overlaid by a Pliocene (Snake Creek) formation. Photograph by American Museum of Natural History expedition of 1908. apparently in an old river channel, in such vast numbers as in places to form a veritable bone bed several feet thick, in which, owing to the scatter- ing influence of river action, complete skulls and skeletons are very rare. All the species and mutations are more advanced than those of the Re- publican River, or Peraceras Zone. Among the hoofed Herbivora all the Lower Pliocene types of rhinoceroses, however, still occur, including remains which are attributed to Teleoceras, Aphelops, and to a still simpler brachyo- dont rhinoceros probably belonging to the persistent brachyodont phylum mentioned under the Republican River (p. 348). Among the dying-out members of the fauna are rare examples of the Miocene oreodont Mastodons, longirostral Merychyus. Tetralophodon The most important and unexpected fea- ?Trilophodon (Florida) ture of this assemblage is the evidence of the Horses, several phyla presence of the bovid division of the Cavicornia. PREVAILING MAMMALS THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 300 Rhinoceroses, 3-4 phyla Teleocerine For the first time in the history of the North American continent true antelopes are positively Aceratherine recognized, which appear to be related to the Peraceras tragocerine, or flat-horned group,! characteris- Aphelops tic of the European Miocene and Pliocene; Aceratherium hence the animal is named Neotragocerus and Tapirs the zone in which it occurs the Neotragocerus Taptravus Zone. The horn cores are perfectly straight, Gravigrade edentates and of a round-oval section; they approach ? Megalonychids those of the existing mountain sheep (Oream- Last oreodonts, 2 phyla nos) but lack the curvature. The teeth and Merycocherus jaw of species of Bison also occur in this forma- Merychyus tion, but there is some doubt as to whether they Camels, llamas Browsing camels are properly associated with this geological level, because the specimens may be intruders Alticamelus from a more recent formation. Grazing camels Another possible newcomer is indicated by Procamelus the presence of gravigrade edentates represented Pliauchenia by an undetermined member of the Megalonyx Cavicornia family. It will be recalled, however, that the Neotragocerus claw of a gravigrade edentate has been found Merycodonts in the Middle Miocene (Mascall) of Oregon, Merycodus and there is a possibility that these giant sloths Pro-Cervids may have been resident in the forests of North Blastomeryx America throughout the Cenozoic period, while Peccaries not finding their way into the river and flood Prosthennops plain areas. Carnivores By far the most astonishing feature of the Rodents fauna is the extraordinary richness and variety Mylagaulids of the horses; these are the most abundant (Horned gophers) Primitive beavers (Eucastor, Dipoides?) animals in this formation. The four or five main phyla are the same as those in the Upper Miocene (p. 297), that is, we find remains of the conservative and presumably tridactyl browsing or forest horses (Hypohippus and Parahippus) intermingled with those of the intermediate stage in the evolution of the true horses (Mery- chippus). There are also several species belonging to the Protohippus and Pliohippus phyla, as well as several species of the desert-living horses (Neohipparion). This assemblage of conservative and progressive types of horses was certainly one of the most distinctive features of Lower Plio- 1 Tn the tragocerine group the horn cores are laterally compressed, as in the goats (caprine section), but the grinders are short-crowned, resembling those in the brachyodont antelopes. (Flower and Lydekker, An Introduction to the Study of Mammals Living and Extinct, Lon- don, 1891, p. 349.) 356 THE AGE OF MAMMALS cene times in North America. These animals must have swarmed in great herds over the prairies, the conservative or browsing types dwelling in the woodlands and copses. A marked approximation to the dental type of Equus is seen in certain varieties of Neohipparion found in this deposit, while certain varieties of Pliohtppus approximate the South American Pleistocene horse Hippidion. There is no conclusive evidence that any of these horses were monodactyl, nor among the thousands of teeth pre- served can a single one be referred to the genus Equus. Among the camels the typical camel of the Upper Miocene (Procamelus) is well represented, as well as the giraffe camel (Alticamelus). Mingled with them are remains of gigantic pliauchenias, equaling in size and robustness those of the Middle Pliocene (Blanco Formation). The peccaries belong to the Upper Miocene genus Prosthennops, although the teeth begin to approach those of the Lower Pleistocene Platygonus. The remains of the American Cervicornia and of the merycodonts also present a mixture of Upper Miocene and of more recent character. The rodents are again represented by the mylagaulids, or horned go- phers, by the pocket gophers and primitive beavers. Among the latter we find Dipoides, an animal also observed in the Pliocene of China (Schlosser) and regarded by Matthew as possibly related to the Castoroides of the Pleistocene. Among the carnivores are lions and saber-tooth tigers, amphicyons and cyons, elurodons and true wolves (Tephrocyon), cacomistles (Bassariscus), and mustelids of several genera. (W. D. Matthew.) Virgin Valley and Thousand Creek of Nevada Reference has been made above (p. 338) to the astonishing discovery of strepsicerine antelopes or kudus in northwestern Nevada.' The sequence of the Tertiary formations in this region is as follows : Terrace formations Quaternary, late Epoch of cahon-cutting (and of extensive faulting) Quaternary, early Deposition of Mesa Dolorite Quaternary to Pliocene Thousand Creek section Pliocene to late Miocene Virgin Valley Formation Pliocene to early Miocene Epoch of erosion and faulting Miocene Puebla Range series (=?Columbia Lava) Miocene to Oligocene The Virgin Valley Formation proper as explored by Merriam probably exceeds 1,500 feet in thickness; it is composed chiefly of voleanic ash and tuffs, the included gravels, sands, clays, lignitic and diatomaceous deposits being of much smaller volume than those of purely volcanic origin. 1 Merriam, J. C., The Occurrence of Strepsicerine Antelopes in the Tertiary of North- western Nevada. Univ. Cal. Pubdl., Bull. Dept. Geol., Vol. V, no. 22, pp. 319-330. THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 397 The mammal-bearing beds of the ‘Thousand Creek’ section seem to correspond mainly with the upper levels of the Virgin Valley. The frag- mentary fossils found here are of extraordinary interest. The two large antelopes ([lingoceros, Sphenophalos) exhibit close affinities to those of the tragelaphines of the Siwaliks of Asia, including the recent nilgai (Bosela- phus), which in turn are related to the recent kudu (Strepsiceros), eland (Oreas), etc., of Africa. The kudu (Strepsiceros) and eland (Oreas) occur in the Siwaliks of southern Asia, as well as the nilgai. Sphenophalos presents a near resemblance to the Neotragocerus discovered in the Snake Creek beds, Nebraska (p. 355), except in the comparative smooth- ness and denseness of the surface of the horn core, which suggests affinity to the recent prong-horn antelope (Antilocapra) of the Western plains. If this animal (Sphenophalos) proves to be intermediate between the bovine antelopes of Asia and our prong-horn antelopes, or antilocaprids, it will go to confirm the theory advocated by Matthew! that the American prong- horns are, after all, aberrant antelopes, that is, with affinities to the Bovide. The true antelopes are represented by Neotragocerus, as well as by three species of the two Asiatic genera above mentioned. A rich fauna of typical American mammals was contemporaneous with these antelopes in Nevada, and points to their Lower Pliocene age, espe- cially in the survival of several species of rhinoceroses and the stage of horse evolution known as Merychippus and Parahippus. The forest-living horse (Hypohippus) and the desert-living type (Neohipparion) are somewhat doubtfully recorded. Among the aberrant Perissodactyla is a form at- tributed to Chalicotherium. The peccaries are represented by Prosthennops; the cameloids by Procamelus and Alticamelus. There is a species of Palco- meryx near P. borealis, as well as the deer-like antelope Merycodus. The small fauna includes the sewellels (Haplodontia), marmots, hares, mylagaulids, castoroids (Dipoides), and gophers (Geomys); beside several kinds of canids there is a felid of gigantic size. The Edentata are represented by remains of very large claws resembling those of the megalonychids except for a narrow median fissure. Rattlesnake Formation of the John Day Valley, Oregon As shown in the diagram (Fig. 164), this is the uppermost of the series of Cenozoic formations in the John Day region, overlying the Middle Miocene Mascall Formation and the Upper Oligocene John Day.” The type 1 Matthew, W. D., A Complete Skeleton of Merycodus. Bull. Amer. Mus. Nat. Hist., Vol. XX, 1904, pp. 101-129. 2 Merriam, J. C., and Sinclair, W. J., Tertiary Faunas of the John Day Region. Univ. Cal. Publ., Bull. Dept. Geol., Vol. V, no. 11, Oct., 1907, pp. 171-205. 358 THE AGE OF MAMMALS specimens of the following species of Pliocene mammals are supposed to have been derived from the Rattlesnake beds: Neohipparion occidentalis Leidy. Neohipparion sinclair Wortman. ?Platygonus rec Marsh. To these should be added, from specimens in the University of California collection, a horse referred to Pliohippus supremus Leidy, also some remains of rhinoceroses which are specifically indeterminate, a large suilline form, ¢ Rattles hie : cai Mascall am contact ——_ & Fic. 163. — Miocene exposures near mouth of Rattlesnake Creek, John Day Basin, Oregon. Mascall formation (Middle Miocene) below. Rattlesnake formation (Lower Pliocene) above, separated by an unconformity. Photograph by J. C. Merriam. fragmentary remains of a camel smaller than Alticamelus, and portions of a carapace and plastron of a land tortoise (Clemmys hesperia, Hay). The Rattlesnake beds are composed of loose gravels, probably repre- senting a fluviatile or flood plain deposition. These gravels, associated with tuffs and rhyolitic lavas, lie upon the up-tilted and eroded edges of the Middle Miocene Mascall Formation (see p. 288). The mammal remains have been obtained both from the tuffs and the gravels. The scattered and broken condition of the bones of one of the horses found in these beds also seems to indicate a long exposure of the remains on a land surface which was being rapidly worked over. The close of the Rattlesnake deposition marks the beginning of a long interval of erosion which may be regarded as the open- ing event of the Quaternary. (Merriam and Sinclair, op. cit., p. 175.) THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 309 CHARACTER «. q a Few Fossils : = musa eravels” and 5g Pliohippus supremus (Leidy) O jl , | 500’ us nodules : Abundant mammals a el Local rhyolite flows | Silicified tree trunks, standing erect, oO 1000 |O, toward the top locally present Oo = = and bottom of this ro i division ia Ne (rls i h LO 8 aS Re PN tN RS io) > - : 250’ ts Red, green, and | Hlotheriwm (large species) Wes white tuffs and | Rhinoceros (gen. ? sp. ?) “300 ae tuff-shales Merycoidodont = J 2 25 / mo ? lw ab /O G3 vA Lavas, tuffs, tuff-shales and agglomerates 2 a= Plant fossils exclusively S) Ww ra REMARKS Fie. 164.— Columnar section of the John Day Formation of Oregon, and superposed strata, Eocene to Pliocene. After Sinclair, 1909. 360 THE AGE OF MAMMALS MiIppLE PLIOCENE Blanco Formation of Texas, Glyptotherium Zone The Blanco Formation of Texas is decidedly distinct and more recent in its mammalian life than that of the Republican River, of the Rattlesnake, or of the Snake Creek beds, just described. It is provisionally regarded as of Middle Pliocene age. Its most distinctive characters are the appearance of short-jawed masto- dons with few grinding teeth approaching the Stegodon type, and of South American armored edentates, or glyptodons. Cenozoic beds of Texas. — Before de- scribing the fauna of this very important formation, it is desir- able to outline the characters of the Fia. 165.— Upper view of the shield and armored tail of Crenozoie deposits of Glyptotherium as exposed in the Blanco horizon of Texas. Photograph by American Museum of Natural History, 1900. northwestern Texas as successively — studied by Cummins (1891) and Gidley (1899, 1900, 1901). As in Nebraska, South Dakota, Montana, and Oregon, we obtain vistas of the Cenozoic depositions in this southwestern portion of the United States which afford vivid pictures of the life succession. The credit for prior exploration belongs to Mr. W. F. Cummins of the Texas Geological Survey, whose early collections were submitted to Cope for determination. Credit for the more mature determination of the age of these beds and the fauna which they contain belongs to the American Museum expeditions conducted by Mr. Gidley. The following is a summary of the conclusions reached by the latter author.! Since the close of the Triassic there has been no great disturbance or change of level in the region of the Staked Plains (see map), hence the strata of the Triassic which underly this hilly region are for the most part nearly horizontal, and the country at the beginning of the Miocene epoch was comparatively level. After a long period of erosion in which the Cretaceous deposits were removed during Lower or Middle Miocene times, flood plain and lacustrine conditions prevailed and the ‘Panhandle Formation’ (Fig. 167) was widely spread over the vast area now occupied by the Staked 1 Gidley, J. W., The Freshwater Tertiary of Northwestern Texas. American Museum Expeditions, 1899-1901. Bull. Amer. Mus. Nat. Hist. Vol. XIX, Nov. 21, 1903, pp. 617-635. a THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 361 Plains, extending westward to the Rocky Mountains of New Mexico, and spreading eastward over a much greater territory than they now occupy. All the formations succeeding the ‘Panhandle’ or of more recent date are oR (1) Dinocyon gidl yl Maisto 1 proemetus Fee ee pomliae a H 5 - * PleisfocenezRecenr |} Pes Dee : I 3 a as Sa Pliocene (Blanco) Miocene (Loup Fork) | Miocehe MI Triassic aa l=lacustrine, r=fluviatile, e=eolian. a todon @ 2 . Ae See t ee ee eee f et Explorations of the Biatel> 4 ; e is 3 ; American Museum ee BB aes 1899-1901, under ------------- Expedition of 1899. 42 7 JW. Grdley. Fic. 166.— Map of a section of northern Texas showing location of important fossil mammal finds and geologic horizons. After Gidley, Amer. Mus. Exped., 1902. represented by comparatively small areas of fluviatile, flood plain or eeolian origin. The earliest of these more restricted formations are known as the ‘Claren- don,’ and are of Upper Miocene or Lower Pliocene age, containing such characteristic forms as Procamelus, Protohippus, Pliohippus, Hipparion, and T'rilophodon. The main body of the Clarendon beds consists for the most part of cross-bedded sands and sandstones, intermixing more or less 362 THE AGE OF MAMMALS and cross-bedding with the clays; these indicate the existence of old river channels taking a nearly east and west direction, or approximately the same as that of the streams draining the country at the present time. Some of them are traceable for long distances. It is in these peculiar beds of sandy clays that all the fossils of this region occur. Still more recent than these are new and fresh river channel forma- tions (Fig. 167) which also cut their way into the Middle and Lower Mio- cene and constitute the famous ‘Blanco Formation’ of Cummins and Cope. These beds occupy a comparatively narrow valley or basin formed for their deposition by ancient erosion of the older Lower Miocene (Panhandle beds); they are traceable southeastward for fifteen or twenty miles to the edge of the plains; there is total absence of any proof for the theory “Rock CREEK” “CLARENDON” BLANCO 1 (middle Pliocene) (Equus zone, lower Pleistocene) (upper Miocene) eG egal : aay “PANHANDLE, 1). li, a) SSeemeueeyy* fn edo (y) 0) eke Sete (middle Miocene) “Jurassic sandstone®. 22.2) Triassic shales By permission of the American Museum of Natural History Fie. 167.— Diagrammatic section of the Llano Estacado region of Texas, showing the intrusion of Miocene, Pliocene, and Pleistocene river channels in an older Middle Miocene Formation. After J. W. Gidley. of lake origin of these beds, and many evidences of river or stream deposi- tion. Occasional deposits of Fuller’s or diatomaceous earth are accounted for by the supposition that there were in this ancient valley occasional pools filled with clear water partially isolated from the main stream. The ani- mals which were preserved here include the armored and gravigrade eden- tates, the short-jawed mastodons, and advanced types of horses and camels. A third period of river or flood-plain formation traversing the same Lower Miocene substratum occurred during the Pleistocene epoch, laying down the broad bands of the ‘Rock Creek Formation,’ also of fluviatile, alluvial, and xolian origin, composed of cross-bedded sands, gravels, and clays. The wind, carrying large quantities of fine dust and sand on the surrounding plains, may have played an important part in forming these deposits. The mammals represented consist wholly of land forms, and some of the bones show weather-checking; they contain the characteristic Lower Pleistocene forms, Hquus, Elephas imperator, and Platygonus. This geologic succession in Texas may be summarized as follows: Lower Pleistocene, Rock Creek Formation Equus and Elephas imperator Zone Middle Pliocene, Blanco Formation Glyptotheriwm Zone Upper Miocene or Lower Pliocene, Clarendon Procamelus Zone Formation Middle and Lower Miocene, Panhandle For- Merycochaerus Zone mation —— - THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 363 Mammals of the Blanco Formation. — The ‘ Blanco’ of Texas takes its name from the little mountain of white sand near the edge of the Llano Estacado on Catfish Creek, which as a prominent landmark has been digni- fied by the name of Mt. Blanco. (Fig. 168). The life phase of the Blanco is distinguished: (1) negatively by the undoubted extinction of the Oreodontidie, a phylum which we have ob- served in its last stages in the Lower Pliocene; (2) by the apparent extinction of the rhi- noceroses; in all the ex- plorations which have been carried on in these beds no traces of these animals have been found; (8) by the apparent but not yet fully demonstrated absence of the forest or browsing horses of Fic. 168.— American Museum camp below Mt. Blanco, the Hypohippus type. Crosby County, Texas. ‘Mt. Blanco’ is the white hill in the NEL yP distance. Glyptotherium Zone. Photograph by American No traces have been Museum of Natural History expedition of 1900. found either of the grazing horses with short-crowned teeth, or of the Merychippus type. An- other browsing mammal which has not yet been found in this zone is the giraffe camel, or Alticamelus. . Although the fauna is still imperfectly known, Mastodons, brevirostral every branch of the mammals shows disappear- ?Tetralophodont ances as well as certain new arrivals which are ?Trilophodont decidedly indicative of a new faunistic stage. Stegodons Of marked zoégeographic interest is the first S. mirificus appearance here of the giant glyptodonts, or Grazing horses, 3 phyla armored edentates of South American type; it is Protohippus of course impossible to determine whether these Pliohippus animals eytered the country about this time or Neohipparion whether they had found their way there in the Edentates Lower Pliocene, because at no period do the glyp- Gravigrades todonts extend very far north. Accompanying Megalonychids ? these armored edentates were the great hairy Glyptotherium gravigrade sloths related to the genera Megalonyx Peccaries and Mylodon, evidences of the existence of which Platygonus we have already found in the Lower Pliocene and Felide possibly in the Middle Miocene of North America. Felis In Texas and Nebraska, and probably in some 364 THE AGE OF MAMMALS Mustelidee outlyers of the ‘Ogallala Formation,’ we find the Canimartes first proofs of the existence in America of short- Canidee jawed or brevirostral Proboscidea. These masto- Canis dons as a rule have lower incisor teeth, and were Amphicyonids hence termed Dibelodon by Cope; they possess many-crested molar teeth, in some respects resem- bling those of the Stegodon type. Among the camels occur pliauchenias of very large size. The peccaries or dicotylids now pass from the Miocene Prosthennops stage into the Upper B Fie. 169.— Middle Pliocene mammals of Texas (X 345). Outline restorations by Charles R. Knight. A. The glyptodon Glyptotherium texanum. B. The giraffe-camel Alticamelus. Pliocene and Lower Pleistocene Platygonus stage. This animal is a large, fleet-footed, or cursorial peccary, including two species,! the more primitive 1 Gidley, J. W., On Two Species of Platygonus from the Pliocene of Texas. Bull. Amer. Mus. Nat. Hist., Vol. XIX, July 24, 1903, pp. 477-481. THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 365 of which (P. texanus), it is interesting to note, presents a close relationship to the P. rex from the Rattlesnake Formation of Oregon. The horses are imperfectly known, but it is certain that they still be- longed to the three great grazing phyla Pliohippus, Protohippus, and Neo- hipparion, the browsing Hypohippus phylum having apparently disap- peared, as well as the intermediate Merychippus phylum. One of the species of Protohippus (P. cumminsii) was so progressive in character as to have been referred by Cope to the genus Hquus, but according to Gidley Fig. 170.— Carapace and tail of the Pliocene glyptodont Glyptotheriwm and skeleton of the recent armadillo Xenuwrus. In the American Museum of Natural History. it shows a much closer relationship to the three-toed horse of the Miocene, though it is more advanced than any true Miocene species of this genus. The Pliohippus of this stage was also mistakenly referred by Cope to Equus, but its principal characters point to a more primitive phase than any true species of this genus. Glyptodonts. — Among the edentates, Glyptotherium is the only one fully known. The existence of glyptodonts in Texas (1888) and Florida (1889) was first made known by Cope and Leidy. Cf., however, Penck’s later views, as expressed in the table (p. 379). PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 381 Human culture stages. — Our review of the time divisions of the Quater- nary naturally closes with that of the human culture periods, which are most clearly presented in the accompanying table by de Mortillet,! and below will be found brief outlines of the history of Paleolithic man and the appearance of man in North America (p. 494). G. pE MORTILLET’S CLASSIFICATION OF 1898-1908, BASED ON THE EVOLU-— TION OF HUMAN IMPLEMENTS? Gerotocicat | Hisroric MATERIALS AND TYPES OF CutTurE STAGES Periops | Divisions IMPLEMENTS Pye eeee . Merovingian XV — Wabenian o s 2 XIV —Champdolian a Roman on Tron NUIT — Lugdunian HOLO- Gane A XII — Marnian 2 Gallic RECENT 5 z : XI — Hallstattian = S < — Larnaudian 3 Bronze Tziganian ie IX —Morgian Neolithic VIII — Robenhausian VII —Magdalenian oi mG A VI —Solutrian < ro) vita Zz OC fe Paleolithic ; faa 3 2 ° Stone V — Mousterian =< (ea) a i — *heuliar Se 8 IV Acheulian Go my Ay III —Chellean es. II — Puycournian THR- Eolithie TIARY an a I — Thenaysian The Eolithic Stage.* — The rude flints known as eoliths, which precede the earliest palseoliths of the Chellean Stage, have been the subject of much 1De Mortillet, A., La Classification Palethnologique. Paris, 1908. 2From A. de Mortillet’s La Classification Palethnologique, Paris, 1898-1908. This classification is that of the elder de Mortillet, and it is considerably modified by more recent discoveries. 3 MacCurdy, G. G., The Eolithic Problem, Evidences of a Rude Industry Antedating the Paleolithic. Amer. Anthrop., Vol. VII, no. 3, July—Sept., 1905, pp. 425-479. 382 THE AGE OF MAMMALS controversy.!. Flints thought by some to be the work of man were discovered by l’Abbé Bourgeois in 1867 in the Miocene of Thenay, Loire-et-Cher, and in 1877 Rames brought to notice flints from the Upper Miocene volcanic ash beds of Puy-Courny, Cantal, in central France, a formation of the same age as the Pikermi fauna. In 1892 Brown proposed the term ‘eoliths,’ to dis- tinguish these supposed very primitive artifacts from the ‘paloliths’ and ‘neoliths’ of Lubbock (Fig. 174). These flints are very rough, but rude as they are, they generally show one part shaped as if to hold in the hand, while the other part appears to be Fic. 174.— A. Eolith, Mafflean Epoch, Belgium. 8B. Palsolith, Chellean Epoch, Milton Street, Kent, England. ©. Neolith, Upper Robenhausian Epoch, Gille Leie, Denmark. Photograph by MacCurdy, 1909. ; edged or pointed for cutting? It is a puzzling fact that the earliest eoliths resemble the later ones, there being, therefore, little development or im- provement in form for hundreds of thousands of years. Eoliths have been discovered not only in Upper Miocene deposits of central France, but in early Pleistocene gravels of France (St. Prest) and Belgium, in southern England (possibly Kent), and in Upper Oligocene beds of Belgium. The Belgian geologist Rutot has devoted his life to the Eolithic period and proved that, like the Paleolithic, it is capable of sub- division into a number of stages or industries, which are geologically demon- strable (see Table by MacCurdy). Perhaps the most convincing discovery 1 Wilson, J. H., Recent Journeys among Localities noted for the Discovery of Remains of Prehistoric Man. Ann. N.Y. Acad. Sci., Vol. XVI, no. 2,-Mar. 17, 1905 (read Jan. 18, 1904), pp. 65-74. 2 Penck, A., The Antiquity of Man. Lecture before Washington Acad. Sci., Feb. 1, 1909. Abstr. Science, n.s., Vol. X XIX, no. 739, Feb. 26, 1909, pp. 359-360. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 383 RELATIVE CHRONOLOGY OF THE EOLITHIC AND PALEOLITHIC OF THE GEOLOGICAL PERIODS Flan- drian me s & ~ ae Ste! Braban- tian Hes- a bayan alban ala 2|8 nw ale g 5 Cam- ce pinian a ; Z | Mosean 4 Upper a Z <3) 5 | Middle a Ay Lower ie < | q | Upper Ble a 71 a a 3 Middle is) a Lower Upper Q Zz 5 | Middle S =} e) Lower STONE AGE (after MacCurpy) GLACIAL AND INTERGLACIAL FAuNA Eprocus Daun Stage Gschnitz Stage ; Buhl Stage Reindeer (Wisconsin) Bison Wirm Glacial Equus ca- ballus Riss-Wiirm Ursus spe- Interglacial leus Elephas Riss Glacial primige- (Ilinolsan) nius Rhinoceros tichorhi- Mindel-Riss on Interglacial Rhinoceros merckit Elephas antiquus Mindel Glacial (Kansan) eee Giinz-Mindel Elephas Interglacial meridio- nalis Giinz Glacial (Pre-Kansan) Hipparion . Dinothe- rium HuMAN CULTURAL |, Type STATIONS REMAINS Epocus Cro-Magnon,| Magdale- | La Madeleine Grimaldi nian (Dordogne) Solutréan | Solutré (Sadne-et- Loire) Grimaldi Aurigna- | Aurignac (Negroid), cian (Haute-Ga- R Combe-Ca- ronne) iS pelle zi La Chapelle- f 5 aux-Saints, : | | H. Mouste-| Mouste- Le Moustier = riensis, Spy rian (Dordogne) ra Krapina, Neandertal Acheulian | Saint-Acheul (Somme) Chellean Chelles (Seine- et-Marne) Strépyan Strépy (Bel- gium) Mesvinian | Mesvin (Bel- gium) Homo hei- Peta ® | iiatteaa | «| Mamie (Bele. sis : gium) Reutelian | Reutel (Bel- gium) Saint- Saint-Prest Prestian (Eure-et- Loire) Kentian Kent (Eng- o land) = eo) & Lown 4 ie) & Cantalian | Puy-Courny (Cantal) , Fagnian Hautes- Fagnes Bon- celles (Bel- gium) 384 THE AGE OF MAMMALS of all is that recently reported of the presence of eoliths in the same depos- its with a jaw of very low type (Homo heidelbergensis). If they are to be regarded as human artifacts, the antiquity of man or of a pre-human type given to shaping stone implements is greatly increased: three or four times for the Pliocene, and six or eight times for those found in the Lower Miocene (Cantal). If, as claimed by Rutot, eoliths occur under strata of Upper Oligocene age, the length of time is still further Flinty layer (ca//loutis) with Neolithic industry. FLANDRIAN WURM. —— ————= SS Flinty layer without industry. pei er STRATIFIED ppp ae ma YI Sc industry. RISS. === | Flinty layer with Chellean SS = industry. MINDEL-RISS 2ZZZEISSSSSWNSSK INTERGLACIAL. | eee SS | Flinty layer with transition CAMPINIAN LZ” SSS 8 fon Eolithic to Paleolithic (Strepyan industry). MIN— DEL-RISS INTERGLA- = CIAL. SSF LUMIAL SANDS DSSS AE St == “ Flinty layer with Mesvinian =AN =POTTER industry. MINDEL-RISS MOSEAN:------- 2 eee INTERGLACIAL. SS Flinty layer with Mafflean industry. MINDEL-RISS INTERGLACIAL. "4 Fia. 175.—Section of the Exploitation Helin, near Spiennes, Belgium, showing the super- position of the Quaternary deposits; lower terrace of the valley of the Trouille. After MacCurdy, adapted from Rutot. multiplied. The presence in the Miocene of France of extinet phyla of anthropomorphous primates offers one possible explanation of the origin of eoliths; it seems very unlikely, in view of their great antiquity, that any being at all closely resembling man (genus Homo) could have remained through such long ages while all other genera of mammals became trans- formed. The only known Miocene and Pliocene primate which might be considered as an ‘eolith’ maker is Dryopithecus; all others belong to existing phyla of monkeys, baboons, and apes. (Penck, 1909.) The intermediate anthropoid, Pithecanthropus, attributed to the Pliocene by its discoverer Dubois in 1893, is now by Volz referred to the Pleistocene. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 389 It is regarded by Schwalbe! either as a direct or indirect ancestor of the human phylum, standing intermediate between the apes and man in respect to its high brain capacity and the structure of its femur. It thus probably belongs in the family Hominide, and if so it had a grasping thumb. Duration of the Pleistocene The Pleistocene was estimated by Dana (1874) to be equal to one- fourth of the entire Cenozoic Era; by Ward (1885) and Williams (1895) it has been estimated at one-third of the entire Canozoic Era. The tend- ency of more recent thought has been altogether in the direction of length- ening the duration of Pleistocene time. If with Wallace we accept Croll’s theory and estimate, the last glacial advance would date back to the last period of great eccentricity, namely 200,000 years. The other figures show the variations of opinion on this subject and the increasing tendency to prolong the estimates of time. Upham 1893 100,000 years Sollas 1900 400,000 years Penck 1908 500,000 to 1,000,000 years The more recent estimates, although made by very high and usually conservative authorities, appear excessive unless we are to extend our estimates of Tertiary time (see p. 63) to twenty million years, and of pre- Tertiary time into hundreds of millions. _ Penck has recently? (1908) pointed out the vast interest which attaches to this duration problem in connection with the antiquity of man. He believes that the whole Ice Age lasted somewhere between 500,000 and 1,000,000 years. The second, very long and warm interglacial epoch, known as the Helvetian or Mindel-Riss, is alone reckoned by him at several hundred thousand years, and the final short, or Riss-Wiirm, Interglacial Stage is reckoned at nearly 100,000 years. Since the climax of the final, or Wiirm, Glaciation he believes that from 30,000 to 50,000 years have elapsed. As regards the duration of palseolithic culture periods, the older paleolithic, or Chellean and Mousterian culture periods are of much longer duration than the newer palolithic, or Solutrian and Magdalenian. Since the beginning of the latter, or Magdalenian, perhaps 24,000 years have elapsed; since its end perhaps 16,000. Compared with the Paleolithic divisions, the Neo- lithie stone and metal periods have occupied an almost unappreciable length of time; if the beginning of the age of metals dates back 3,000 to 3,500 years, that of the Neolithic lake dwellings began about 5,000 to 7,000 years ago. 1 Schwalbe, G., Ueber fossile Primaten und ihre Bedeutung fiir die Vorgeschichte des Menschen. Mitteil. Philomat. Ges. Elsass-Lothringen, Vol. IV, no. 1, Decade -16 (1908), Strassburg, 1909. * Penck, A., Das Alter des Menschengeschlechtes. Zeitschr. Ethnol., no. 3, 1908, pp. 390- 407. 2c 386 THE AGE OF MAMMALS Geologic deposits. —'The chief geologic formations or deposits of glacial times are the following: Glacial boulders, boulder clays, and drift. Lignitic and swamp deposits. Fluviatile gravels, till, and river terraces. Lacustrine and marine terraces. Loess, fine, calcareous, fluviatile and zeolian loam. Volcanic travertines and tufas. Phosphorites and other fissure deposits. Cave deposits. Loess, found in the Pleistocene of Europe, northern Asia, North America, and in the pampean regions of South America, is the most distinctive of all glacial deposits, next to the boulder clay and drift. It consists of a fine, porous, silicious and calcareous silt, usually of a light brown color, charac- terized by a peculiar competency to stand in vertical walls during erosion. Its distribution is quite independent of altitude, occurring in Europe from sea level to a height of 1,500 meters. Its origin is partly fluviatile, partly eolian. Thus it is believed that the fine mud carried by rivers becomes desiccated and is retransported by the wind. Penck (1904) describes loess as formed in districts traversed periodically by great streams, leaving dry mud which is redistributed by the wind. In Europe it is one of the most characteristic formations of the interglacial epochs; some loess de- posits belong to the Riss-Wiirm Interglacial, others are known from the older Mindel-Riss Epoch, and some very rare deposits probably date back to the Giimnz-Mindel Interglacial epoch.!. Another theory of formation is that the snow driven by the wind carried earthy material with it. Thus the loess remained as a residue after the melting of the snow.” The plateau between Uzés and Avignon® contains numerous’ fissures filled with phosphorites which can scarcely be distinguished from those of Quercy but contain the remains of mammals of mid-Pleistocene age. I. PLEISTOCENE LIFE OF EUROPE Flora and Climate It is clear from the great fluctuations of temperature and moisture which occurred during Pleistocene times that the flora cannot be treated as a unit nor as progressing in a single direction like the flora of the preceding 1 Penck, A., Die alpinen Eiszeitbildungen und der prihistorische Mensch. Arch. Anthro- pol., n.s., Vol. I, no. 8, 1904. 2 Davidson, Charles, On Deposits from Snow Drifts with Especial Reference to the Origin of the Loess and the Preservation of Mammoth Remains. Quart. Jour. Geol. Soc. London, 1894, p. 472. 3 Depéret, Sur les phosphorites quaternaires de la region de Uzés. C. R. Acad. Sci. Paris, Tome 120, 1895. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 387 epochs. It presents alternations of arctic, boreal, and temperate species, which migrated southward and northward following the advances or re- treats of the glacial cap. The broad divisions of the climate are as follows: First cold phase, connected with the first glacial period. The fairly warm climates of the interglacial periods. The damp and cold climates of the last glacial advances. The dry and cold climate of the period of the last glacial retreat in the age of the reindeer. aioe abot There is evidence both in Europe and North America that especially in certain of the long, warm interglacial intervals the climate in the northern hemisphere was somewhat more equable and milder than at present, with a higher mean temperature and at certain intervals a greater precipitation of moisture. There was perhaps more sunshine than now. As a result of such favorable conditions arboreal vegetation flourished to the far north. The present tundras of Siberia and British America then supported forests which have long since been extirpated, the northern limit of similar living trees now lying far to the south.? A picture of the flora of the very long and warm Mindel-Riss’ interval of the Second Interglacial epoch, the Chellean Stage of human culture according to Penck, in which the hippopotamus appears for the last time in northern Europe, is preserved in the tuf de la Celle, which contains remains of the syeamore maple (Acer pseudoplatanus), willows (Salix), the Austrian pine (Pinus laricia). Higher up in the same deposits we find the box tree (Buxus), not uncommonly the fig (Ficus); the sweet bay (Laurus nobilis) appears less frequently. In the upper part of the tuf de la Celle where Chel- lean pal:eoliths have been found, the fig and sweet bay are absent.* The cli- mate was more damp and certainly milder than that of the present time in this region, the mean annual temperature being eight to nine degrees higher. In Lorraine below the level of the third Pleistocene fauna there occurs a flora in which the most northerly varieties of the larch (Larix) and the mountain pine (Pinus lambertiana) predominate. In still higher plant beds, the tufs de Pont-d-Mousson in eastern France, there are remains of forests composed of deciduous trees some of which have since migrated farther south. These are a few of the many instances showing the southward and northward migration of the flora in Pleistocene times, similar to those to be mentioned as occurring in the Toronto Formation of Canada (p. 448). There is strong ground for the belief‘ that there were cycles of climatic change beginning in earlier interglacial and succeeding glacial 1Croll, J., On Arctic Interglacial Periods. Philos. Mag., Ser. 5, Vol. XIX, 1885, p. 36. 2 Nathorst. Engler’s Bot. Jahrb., 1881, p. 431; also Schréter, C., Die Flora der Eiszeit. Zurich, 1883. ' 3 De Lapparent, A., Traité de Géologie. Paris, 1906, p. 1703. 4 Penck, A., Die alpinen Hiszeitbildungen und der prihistorische Mensch. Archiv. An- thropol., n.s., Vol. I, no. 8; 1904. 388 THE AGE OF MAMMALS epochs. Since the mammalian life of the third and fourth glaciations (Riss, Wiirm), according to Penck, is identical in Switzerland at least, we may ascribe tundra, or barren ground conditions, both to the fauna and flora of these final glacial epochs. From the beginning of the last interglacial interval to the present time the vegetation of the region near the Alps has apparently gone through a cycle of changes such as the following: VEGETATION CLIMATE PERIOD 4th. Forest West-European, oceanic Modern 3d. Steppe Southeast-European, continental Post glacial 2d. Tundra — Northeast-European, sub-Arctic Glacial Ist Forest West-European, oceanic Interglacial The steppe and tundra biotic period, according to all authorities, was the great feature of the last glacial phases. Neumayr estimated that the general lowering of temperature of Europe had not amounted to more than 6° C., and believes that even during the Ice Age a comparatively mild climate prevailed in Great Britain. Martins esti- mated that a lowering to the extent of 4° C. would bring the glaciers of Chamounix down to the level of the plain of Geneva. Penck estimates that, all other atmospheric conditions remaining the same as now, a fall of tem- perature to the extent of 4 to 5° C. would be sufficient to give us back the Glacial Period. s Secular Northward and Southward Migrations of Faunas The passing from the Pliocene to the Pleistocene is clearly outlined on the east coast of England in Norfolk. After the first great cold wave the life of Great Britain is considerably altered; it constitutes the first fauna, as briefly defined above. This is followed in Europe by the second, by the third, and by the fourth faunas, as more clearly distinguished in the accompanying table, and explained above, p. 375. The principal contributors to the theory of northward and southward migrations and to the succession of faunas are Nehring, Woldrich (1882), and more recently Penck. In considering the distribution and migration of the mammals throughout the Glacial Period, we must constantly keep in mind the differences of latitude. Italy had a more moderate climate than central Europe; the reindeer seems never to have found its way there, yet a lowering of temperature in Italy is indicated by the fact that the alpine mammals, such as the marmot (Marmota), chamois (Rupicapra), and steinbok (Ibex) came down to the plains.1. The hippopotamus undoubtedly remained in Italy longer than it did in northern Europe, so it is not surpris- ing to find its remains associated with those of the big-nosed rhinoceros (D. merckit) 1 a cave near Mentone in the French Riviera, which belongs in 1 Tssel, A., Liguria geologie e preistorica. Ref. by Boule in L’ Anthropol., 1893, pp. 602-604. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 389 the period of Aurignacian culture, corresponding with the last glacial ad- . -— . . f vance, according to Penck (see page 379). The same writer considers that at the time central Europe was tundra-like and Italy was a forested country. I. FAuNA. MAMMALS OF THE First, or Nor- FOLK INTERGLACIAL PERIOD Climate temperate _ The faunal zone of the last saber-tooths (Ma- cherodus) First appearance of the giant deer (Megaceros), of the musk ox, and of the bison South of the Alps the straight - tusked ele- II. Fauna. MAmMALs OF THE SECOND AND Turd INTERGLA- cIAL PERIODS Climate temperate to warm-temperate Hardy northern forms of African and south Asiatic mammals North of the Alps the straight - tusked ele- phant and the hippo- potamus, the ances- tor of the mammoth (BE. trogontherii), and III. Fauna. MammMats OF THE Last INTER- GLACIAL, GLACIAL, AND GLACIAL RE- TREAT Climate cold and dry First invasion of the arc- tic, tundra and steppe types, including nu- merous reindeer and musk oxen The true mammoth, the woolly rhinoceros and the reindeer wide- spread in Europe IV. Fauna. MaAmmMALs, OF THE PREHISTORIC Forest, Merapow, AND River FAUNA or EvRopE Climate similar to recent Absence of rhinoceros and elephant, and ex- tinction of the ‘cave’ animals Rarity of reindeer phant and the hippo- the broad-nosed rhi- potamus noceros (D. merckii) are abundant. The musk ox does not ap- pear. Reindeer, if present, are rare. Eolithic implements The cave and loess pe- Neolithic man riods of human culture Late Paleolithic man Eolithie and early Palsze- olithic man Penck?! also observes that we cannot hope to trace a continuous evolu- tion of forms during Pleistocene times, because we are not dealing with a development of one successive series in one locality, but with the cyclical alternation of a number of different faunas compelled to migrate through the alternations in the temperature and in the floras, the mammals disap- pearing and returning at intervals too brief to allow of any marked evolu- tionary changes. Herein lies our difficulty when we attempt to distinguish between the tundra faunas of the late glaciations and the forest faunas of the late interglacial epochs, because the faunas return not only with the same generic but the same specific types, as especially illustrated in the case of the mammoth (LH. primigenius) and the giant deer (Cervus megaceros). Implements of human manufacture, however, mark the progress of time because in the evolution of human culture the glacial epochs are separated by the successive advances in the fashioning of stone implements and in the primitive arts. This ‘alternate migration’ theory is presented in the following table: ? 1See Penck, A., Die alpinen Ejiszeitbildungen und der priihistorische Mensch. Arch. Anthropol., n.s., Vol. I, no. 8, 1904, p. 89, ’04 in Bibliography. 2 After Penck, 1904. The reader will observe some discrepancies between this table and that on p. 397. 390 THE AGE OF MAMMALS Epoch Fauna Vegetation (Nehring) (G. de Mortillet) Present Cervus elaphus Forest Forest NEOLITHIC ( Elephas primigenius PALAOLITHIC 4th, Wiirm, Glacial Epoch } Rhinoceros tichorhinus Tundra Magdalenian Culture Rangifer tarandus ‘ : a i Elephas primigenius | Riss-Wiirm Interglacial / Rpinoceros tichorhinus + Grassy steppes Steppe Solutrian Culture (later part) | \ | Equus caballus J - : =i : Elephas antiquus ) eee neurbag | Rhinoceros merckii { Forest Sarees Cervus elaphus | 3d, Riss, Glacial Epoch Elephas primigenius ] KC Maximum Rhinoceros tichorhinus + Tundra , Tundra Mousterian Culture Glaciation Rangifer tarandus J Rhinoceroses. — The three great rhinoceroses characteristic of the Eu- ropean Pleistocene, which probably belonged to two separate phyla, Asiatic, or Sumatran, and African, are of distinct geologic value. Of the former phylum, D. etruscus of the Val d’Arno! is a small animal of Pliocene and early Pleistocene times, distinguished by brachyodont or short-crowned grinding teeth, and long, slender limbs, two horns, the larger of which is posterior, and the absence of cutting, or front teeth; it is remotely related to the Dicerorhinus, or Sumatran phylum, but differs in the absence of cutting teeth. It belongs with the First Fauna, and does not survive into mid- Pleistocene times. Succeeding this animal in early Pleistocene times both in Great Britain, France, and Italy, also surviving with the Second Fauna of the mid-Pleis- tocene of all Europe, is the broad-nosed rhinoceros, known as D. megarhinus, or D. merckii. It is distinguished from D. etruscus by long-crowned, or hypsodont grinding teeth; it resembles it in the smaller anterior and larger posterior horn, and in the elongation of its limbs and feet. In mid-Pleisto- cene times it became covered with hair, attained a great size, and was very abundant and characteristic. The third species, the woolly rhinoceros (D. antiquitatis, D. tichorhinus), is, however, the distinctively cold weather, steppe, and tundra form, and belongs with the Third Fauna. Like the foregoing species, it has no front teeth, hence has been improperly considered as related to them, but it really belongs to the modern African group of Atelodus (Diceros), distin- guished by a very large front horn and small posterior horn as in the exist- ing “white rhinoceros” (2. stmus). The names of these three rhinoceroses are almost hopelessly confused in the early literature, though the characters were very clearly defined by Dawkins.?. Both in the megarhine and tichorhine rhinoceroses and in old individuals of the Etruscan, the septum supporting the nasal bones becomes more or less fully ossified, to support the stout anterior horns. 1 Dawkins, W. Boyd, On the Dentition of Rhinoceros etruscus Fale. Quart. Journ. Geol. Soc., Vol. XXIV, 1868, pp. 207-218. : 2 Dawkins, W. Boyd, The British Pleistocene Mammalia, Pt. I, Introduction, 1866. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 391 1. Tue Frrst, on Earty PLEISTOCENE FAUNA As a whole the fauna of Europe is now distinguished from that of the Upper Pliocene by the absence of primates, mastodons, antelopes and ga- zelles, and tapirs. This is the fauna of the first interglacial period, known as the Norfolk- Interglacial. It is typified in the Forest Bed of Cromer, Norfolk (Fig. 176, Fic. 176.—Pleistocene. HUROPE.—1 Forest Bed of Cromer (Norfolk). Sables de 2 St. Prest near Chartres (Eure-et-Loire). 8 Malbattu (Puy-de-Déme). 4 Peyrolles (Bouches- du-Rhone). 5 Solhilac near Puy. Clay deposits of 6 Durfort (Gard). 7% Cajare (Lot-et-Ga- ronne). 8 Val d’Arno (Tuscany). 9 Leffe near Bergamo (Lombardy). 10 Rixdorf near Pots- dam (Brandenburg). Gravels of 11 Siissenborn near Weimar. Sands of 12 Mosbach in northern Baden. Freshwater deposits of 18 Clacton (Essex). Sands of Mauer near 14 Hei- delberg (western Germany). 15 Chelles on the Marne, near Paris. 16 St. Acheul (Somme). 17 Ilford and Grays Thurrock (Essex). Lignites of 18 Diirnten and of Utznach, near Ziirich. 19 Taubach near Weimar. 20 Wildkirchli cave on Mont Sdntis (eastern Switzerland). Tuffs of 21 the Tiber Valley, near Rome. Caves of 22 Neandertal, near Diisseldorf (western Ger- many), 28 Spy, near Amur (Belgium), 23a Krapina (Croatia), 24 Chapelle-aux-Saints (Cor- réze). Caves and alluvial deposits of 25 Ternifine (or Palikao) near Oran (Algeria), 26 Pointe Pescade, near Algiers (Algeria). .27 Prince’s Cave (Monaco). Sandy clays of 28 Vdéklinshofen (Alsace). 29 Saalfeld (Saxe-Meiningen). Travertines, etc., of 30 Gera, Jena (Saxe-Weimar). 31 Leipzig (Saxony). 82 Solutré, north of Lyons. Loess of 38 Wiirzburg (Bavaria). 34 Thiede near Braunschweig (Prussia). Cave of 835 Montmaurin (Haute-Garonne). 86 Chdateawneuf- sur-Charente (Charente). Caves of 37% Schweizersbild near Schaffhausen, and Kesslerloch near Thayngen (northern Switzerland). Remains of lake dwellings at 38 Wawwyl (Lucerne), 39 Ro- benhausen, south of Lake Pfiffikon, 40 Concise on Lake Neuchatel (Switzerland). Peatbogs of 41 Hassleben, near Weimar. Travertines of 42 Langensalza (Erfurt) in central Germany. Caves of the 43 Island of Malta, 44 Island of Crete, 45 Island of Cyprus. 1), in which certain mammals, such as the musk ox (Ovibos), are said (Daw- kins) to occur, which are net found in more southerly localities. This 392 THE AGE OF MAMMALS fauna has been treated as of Upper Pliocene age by some writers (Boule !) ; but since in the remarkably rich deposits of the Forest Bed of Norfolk, England, it sweceeds a molluscan fauna of arctic affinity, there is little doubt that we are witnessing the mammalian life of the first temperate interglacial period. The chief localities in which this fauna occurs are the following: Forrest Bep or Cromer, Norfolk, England (Fig. 176, 1), typical of the northern life SABLES DE Sr. Prest (Eure-et-Loir), France, (2) typical of the cen- tral life Marsatru (Puy-de-Déme), France, (3) typical of the central life PEYROLLES (Bouches-du-Rhone), France, (4) typical of the central life SOLHILAC, near Puy, southern France, (5) typical of the central life Durrort (Gard), southern France, (6) typical of the central life VaL p’ARNO (upper deposits), northern Italy, (8) typical of the southern life While many Pliocene animals have disappeared, the fauna still includes a number of forms surviving from the Pliocene, such as the saber-tooth cats (Macherodus), the roe deer (Capreolus), the polycladine deer (C. sedgwicki), the more primitive dicerorhine rhinoceroses (D. etruscus), the horses (Hquus), and especially the southern mammoths (H. meridionalis), and hippopotami. It is noteworthy that the saber-tooth cats and the polycladine deer do not reappear in the later Pleistocene formations of Europe, although the saber- tooths survive to a much later period both in Asia and in North America. No traces of the larger true, or leonine, cats (Felis leo spelea) are recorded at this stage. Among the new arrivals are the earliest and very numerous members of the giant fallow deer race, which terminate in the Upper Pleistocene in the giant deer Megaceros. The bison (Bison) certainly makes its first appear- ance in Europe, and according to some authors the true cattle (Bos) also appear at this stage. It is also important to note here the presence of a form (Caprovis) intermediate between the goat and the sheep, as the name indi- cates, most nearly resembling the mouflon of Sardinia. Among the rodents the large beaver (Trogontherium) succeeds the smaller species, first observed in the Pliocene of the Red Crag. South of the Alps the earliest of the straight-tusked elephants (#. antiquus) occurs. A giant hippopotamus (/7. major) is certainly recorded, both south of the Alps and to the north in Great Britain. The greatest stranger among the new arrivals is the musk-ox (Ovibos), attributed by Dawkins? to the Forest Bed deposits. Geologic proofs of the first glacial advance. — James Geikie* (p. 335) 1Cf., however, Boule, 1890, p. 945. 2 Dawkins, W. Boyd, On the Alleged Existence of Ovibos moschatus in the Forest-bed, and on its Range in Space and Time. Quart. Jour. Geol. Soc. London, 1883, pp. 576-579. 3 Geikie, J., The Great Ice Age and Its Relation to the Antiquity of Man, 3d ed., Lon- don, 1894. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 393 favors the theory that the Forest Bed deposits were accumulated during an epoch of genial conditions which succeeded a colder glacial period in which the Chillesford and Weybourn Crags were deposited; these ‘crags’ mark the culmination of the cold conditions which began to manifest them- selves as early as the Red Crag (p. 317) of Upper Pliocene times; at this culminating time the sea abounded in arctic molluscs. Even in the Red Crag, northern forms of molluses begin to appear, and when we reach the Chillesford and Weybourn crags the marine molluscs present a decidedly arctic aspect. Immediately above the Weybourn Crag there is evidence of a climatic reaction, because the estuarine and fluviatile deposits of the Forest Bed contain a flora and a mammalian fauna of temperate type which contrast strongly with the assemblage of northern and arctic shells in the subjacent crag deposits. Flora of the Norfolk Interglacial. — All the plants composing the Norfolk Interglacial flora belong to living species, and with a few exceptions are still indigenous to Norfolk, including such forms as the maple, hawthorn, elm, birch, alder, hornbeam, beech, pine, and spruce. The arrival of the spruce (Abies) is especially noteworthy because, although known in Miocene times in the arctic region of Grinnell Land, this is its first appearance in central Europe ; it is also found in the interglacial lignites of Switzerland. It has since constituted an important member of the European forests. From this tree flora Reid concludes! that the climate was nearly the same as the climate of present times, but slightly warmer. This is in latitude 52° 40’? Contemporaneous with this temperate flora there flourished the remark- ably rich mammalian fauna of the Forest Bed; the mammals also indicate conditions of climate somewhat warmer than those prevailing in the south of England to-day. Mammals of the Norfolk Interglacial Epoch For our knowledge of the mammalian life of the Forest Bed and contem- poraneous fauna in France we are principally indebted to Dawkins (1880, 1883), to Newton (1880), to Gaudry (1893), to Boule (1902), and Pohlig (1907). Dawkins many years ago (1883, p. 579) gave the ratio of living, extinct, resident, and newly arriving mammals as follows: Survivals from the Pliocene . . . . . 11 species INewcomers:extinct formsii a. vice los Fae ee 6 i living sf 2 Ser Hew gate Lacke CppeetSD Ae The specific determinations of many of these animals, especially of the horses and the deer, await revision, and upon this closer study depend many ! Reid, C., and Reid, E. M., The Pre-Glacial Flora of Britain. Jour. Linn. Soc., Botany, Vol. XX XVIII, Jan., 1908, pp. 206-227. * A list of these plants is given in Dawson’s The Geological History of Plants, 1896, pp. 218-271. 394 THE AGE OF MAMMALS interesting questions. The true red deer, or stag of Europe (C. elaphus), for example, was listed in this fauna by Dawkins, but Newton regarded it as very uncertain, and other authors consider that it first appears only in later Pleistocene times. are as follows: Eolithic Man (indicated by implements only) Southern mammoths E. meridionalis, (2?) E. trogontherii Straight-tusked mammoths (in Italy only) E. antiquus Dicerorhine rhinoceroses D. etruscus Primitive horses E. caballus fossilis E. stenonis Hippopotami H. major Polycladine deer C. sedqwicki Roe deer C. capreolus Axis deer (in Italy or southern Europe only) Giant fallow deer C. dawkinsi, C. verticornis (?) Musk oxen, or musk sheep (in Great Britain) (?) Ovibos moschatus Bison Bison bonasus (?) Primitive true cattle (?) Bos primigenius Large beavers Trogontherium Saber-tooth cats Macherodus (?) cultridens Wolverines, or gluttons (in Great Britain) Gulo luscus The chief members of this mammalian assemblage Forest Bed Fauna. — The authen- tic occurrence in the Forest Bed de- posits of anumber of mammals which are commonly attributed to this fauna was questioned by Newton! after very careful study of all the records and materials. It is cer- tainly very important, now that we recognize a series of glacial and interglacial epochs, that mammals belonging to late Pleistocene times should not be attributed to the For- est Bed Interglacial Epoch without very conclusive testimony. Among , the records which Newton considered doubtful are the hyzena, the broad- nosed rhinoceros (D. megarhinus), the true cattle (Bos primigenius), the red deer (Cervus elaphus), the moose (Alces latifrons), and the giant deer (Megaceros). 'The reference of the musk ox (O. moschatus) by Dawkins must also be considered somewhat doubtful. ; Deer. — The presence of deer in great numbers and representing many different phyla is one of the most distinctive features of the times; it is certain that during the Norfolk Interglacial period there existed nu- merous and varied forms of deer life both in Great Britain and southern and western Europe. They belong to several, probably to as many as five, distinct phyla. The first of these, the polycladine, or ‘many- branched’ deer, so distinctive of the 1 Newton, E. T., Notes on the Vertebrata of the Pre-Glacial Forest Bed Series of the East of England. Geol. Mag., Vol. VII, Pl. XV, 1880, Pt. I, Carnivora, pp. 152-155, Pt. II, Carnivora, pp. 424-427, Pt. III, Ungulata, pp. 447-452. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 395 Bear of the ‘brown’ and of the ‘cave’ type Ursus ferox, U. spelaeus Otters and martens Wolves and foxes re Walrus (in Great Britain) Trichecodon huxleyi Upper Pliocene of the Val d’Arno, now make their last appearance in Europe as Sedgwick’s deer (C. sedg- wickt) of the Forest Bed, with won- derfully complex antlers, and closely related to the C. dicranios of the Val d’Arno. r Si | Eg! a ’ ; Q ‘ oy ; ; i) ' ' ' Fi ‘ f] A & if shows a large proportion of forest and mountain types and no aquatic mam- mals. Hay Springs, Nebraska. — The Hay Springs (Fig. 194, 24) fauna, as explored by the American Museum expeditions of 1893 and 1897, is a very rich one and may be taken as typical of the early phase of the Equus Zone. It includes the llama-like cameloids (Camelops) and a true camel (C. americanus). The true prong-horn antelopes (An- tilocapra) make their first appearance here, and with them are associated the smaller Capromeryx (C. furcifer), an animal inter- mediate between the mery- codonts (see pp. 294-5, 357) and the true American prong-horns. The most abundant species of horse is EE. complicatus, while E. fraternus, a smaller ani- mal, is also found. The sloth which appears here is distinct from the mid- Pleistocene M ylodon harlant of the East, and according to the determination of Brown belongs to a dis- tinct genus, Paramylodon.' 1Matthew, W. D., List of the Pleistocene Fauna from Hay Springs, Nebraska. Bull Amer. Mus. Nat. Hist., Vol. XVI, 1902, pp. 317-322. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 457 Paramylodon is described! as in some features more, in others less specialized than Mylodon and retaining features of the older, more prim- itive sloths. It differs from Mylodon in having but four upper teeth, the hindermost of which is tri-lobed instead of bi-lobed. The limbs are more slender and the ankles more flexible than in Mylodon. A second specimen has recently been found * near Walsenburg, Colorado, which contains five upper teeth, and while exhibiting the elongate skull and inflated muzzle of the type of Paramylodon, it indicates that the generic distinction between these two forms may be insecurely founded. A fine specimen of a Mylodon, Fic. 198.— Quarry in which six skeletons of the Lower Pleistocene horse Equus scotti were found. Head of Rock Creek, Texas. Lower Pleistocene or Equus Zone. Photograph by American Museum, 1900. not distinguishable from the Walsenburg specimen, comprising most of the skeleton, was found in 1880 by Mr. 8. Garman of a Harvard University expedition at Hay Springs. A description of this specimen, now preserved in the Museum of Comparative Zodlogy, has not been published. Prairie wolves (C. latrans) have been found, but few if any true felids. The peccaries (Platygonus) are much more swift-footed and advanced in dentition than the modern peccary, and may be-supposed to have lived more in the open. The prairie dogs (Cynomys), gophers (Thomomys), and field mice (Microtus) are even now characteristic of the plains of this same Nebraska region, while muskrats (Fiber zibethicus) occurred then as now along the streams. Remains of a small species of Castoroides are occasional. This fauna is, on the whole, similar to that of Silver Lake, which differs 1 Brown, Barnum, A New Genus of Ground Sloth from the Pleistocene of Nebraska. Bull. Amer. Mus. Nat. Hist., Vol. XIX, Art. xxii, Oct. 28, 1903, pp. 569-583. * Cockerell, T. D. A., A Fossil Ground-Sloth in Colorado. Univ. Col. Studies, Vol. VI, no. 4, Boulder, Col., June, 1909, pp. 309-312. 458 THE AGE OF MAMMALS from it in the presence of the beaver (Castor) and the otter (Lutra), which are not found at Hay Springs. Rock Creek, Texas. — (Fig. 194, 16.) These beds are extensively ex- posed in the Staked Plains of Texas (Fig. 166) along the south side of Tule Cafion. As described above (p. 362), they represent a Lower Pleis- tocene river channel cutting its way into an older Miocene horizon. They are especially famous for the magnificent series of six skeletons of horses discovered by Gidley ! in 1900 and referred to Equus scotti. (See Figs. 197 and 198.) In these beds are also found a peccary (Platygonus) and the Fic. 199.— The Lower Pleistocene true horse of Texas, Equus scott?. After original by Charles R. Knight in the American Museum of Natural History. imperial mammoth (E. imperator). Cope? had previously reported from Rock Creek asloth (Mylodon sodalis), several species of horses, and two cameloids (Holomeniscus sulcatus, H. macrocephalus), as well as two large land tortoises. Silver Lake of the Oregon Desert. — (Fig. 194, 31.) One hundred and fifty miles northwest of the old Lahontan shore lines in the heart of the Oregon desert of the Great Basin, and twenty miles northeast of Silver Lake there is a slight depression in the desert perhaps twenty acres in extent marked Christmas Lake on the maps, to which Cope gave the name “ Fos- sil Lake.” This ‘Silver,’ ‘Christmas,’ or ‘Fossil’ lake region was succes- 1 Gidley, J. W., A New Species of Pleistocene Horse from the Staked Plains of Texas. Bull. Amer. Mus. Nat. Hist., Vol. XIII, no. 13, pp. 114-116; also Tooth Characters and Revision of the North American Species of the Genus Equus. Bull. Amer. Mus. Nat. Hist., Vol. XIV, Art. ix, 1901, pp. 134-137. 2 Cope, E. D., Report of the Geological Survey of Texas, 1892, 18938, p. 87. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 459 sively explored by Condon, Cope, Sternberg (who made the chief collec- tions), and Russel (1882). It now presents a perfectly dry surface con- sisting of a light-colored mixture of sand and clay or dried mud of voleanic origin; all the fossils lie in this last friable deposit of volcanic dust. Though actually twenty miles distant from Silver Lake, the rich fauna of mammals and birds found has been described by Cope! and Shufeldt, and referred to by Gilbert, as the fauna of the Silver Lake Equus beds. It is obvious that we have no means of correlating it in time with the lacustral move- ments either of Lake Bonneville or of Lake Lahontan, and that at present the correla- tion of this fauna with either of the phases of the Glacial Epoch will be impossible un- less shore lines of the Silver or Christmas Lake region admit of investigation similar to that which has 2 Fia. 200.— The famous Hay Springs Quarry of western been so successful i Nebraska in the Equus Zone, Lower Pleistocene. Photograph the great ancient lakes by American Museum of Natural History expedition of 1897. to the south. The Silver Lake mammal fauna appears to be slightly younger or more recent than that of the Hay Springs Equus beds above described; both the camels and horses are somewhat more progressive in type. It is note- worthy that the bison does not occur in this rich fauna. We owe to Cope! (1889) and Shufeldt? (1892) peculiarly pictur- esque descriptions of this region as it may have been in Pleistocene times. Proof that the country was partly fluviatile and partly wooded is afforded by the presence of the muskrat (Fiber), the otter (Lutra), the beaver (Castor fiber), and the giant beaver (Castoroides). The supposed great mylodont sloth (Mylodon sodalis), an animal as large as the existing grizzly bear, also affords evidence of forested conditions and probably of abundant moisture; it is possible that this animal may prove to be a Mega- lonyx. The mammoth (? HE. columbi) frequented the forests of the river or lake borders. There were several varieties of horses, including especially 1Cope, E. D., The Silver Lake of Oregon and its Region. Amer. Natural., Vol. XXIII, 1889, pp. 970-982. 2 Shufeldt, R. W., A Study of the Fossil Avifauna of the Equus beds of the Oregon desert. Jour. Acad. Nat. Sci. Phila., Vol. IX, 1892, pp. 389-425. 460 THE AGE OF MAMMALS the types EZ. pacificus and E. occidentalis. The most numerous forms next to the horses were the cameloids, animals identical neither with the existing camel nor llama, referred by Cope to the genera Eschatius and Camelops, and distinguished from recent llamas (Auchenia) by the greater reduction of the premolar teeth, a feature which is especially marked in the genus Eschatius. This animal is also found in the valley of Mexico. Among the burrowing forms were the pocket gophers (Thomomys bulbivorus, T. clusius). Geomys also occurs. Hares (Lepus campestris) are very abundant. The peccaries are represented by two species of Platygonus. There are also prong-horn antelopes (Antilocapra). The only carnivore recorded by Cope is the prairie wolf, or coyote (C. latrans), but Matthew has added the gray wolf (C. ef. occidentalis) 1 an animal of the size of the timber wolf. The record of a bear (Ursus) by Cope is not confirmed. The arrowheads and flints found on the surface of these deposits are probably of recent age. Silver Lake avifauna and climate. — It is a very fortunate circumstance that the contemporaneous bird life of Silver Lake is fully known through the rich deposits investigated by Shufeldt* (1892). The bird life was very abundant and not very dissimilar from what we might observe at any of the alkaline lakes of the West, resorted to at the present day by the wild fowl during their migrations. Great flocks of swans (Cygnus paloregonus), geese (Anser condoni), and ducks were there; a cormorant (Phalacrocoraz) was among the rarities; among the species of grebe is one (Podiceps occi- dentalis) still frequenting this region. There were also coots (Fulica minor) and herons (Ardea paloccidentalis). Other forms of birds include two species of grouse, crows, and eagles. The strangest figure upon the scene among the birds was a true flamingo (Phenicopterus copei). The north- ernmost distribution of the flamingoes at present is southern Florida and the Bahama Islands (lat. 27° N.). Shufeldt concludes that the climate might well be compared with that of Florida or the lower part of Louisiana, that the vegetation was fully as luxuriant as it now is in those parts, and that the palms were abundantly represented. This conclusion as to a Floridian climate and the existence of palms is, however, very questionable. Brown ® observes that the South American flamingoes (Phenicopterus chilen- sis) migrate as far south as the lakes in central eastern Tierra del Fuego, lat. 53° S., where they are said to breed, and certainly spend a part of the season. This region corresponds in temperature to the climate of central Alberta, Canada, 400 miles north of Silver Lake. Thus it appears’ that the presence of Phanicopterus copei at Silver Lake has little weight in the determination of climate. It is more probable that the northern lakes of that period contained molluses on which the flamingoes fed. 1 Matthew, W. D., List of the Pleistocene Fauna from Hay Springs. Bull. Amer. Mus. Nat. Hist., Vol. XVI, Sept. 25, 1902, pp. 317-322. * Shufeldt, R. W., A Study of the Fossil Avifauna of the Equus beds of the Oregon Desert. Jour. Acad. Nat. Sci. Phila., Vol. IX, 1892, pp. 389-425. 3’ Mr. Barnum Brown in a note to the author. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 461 Gilbert’s ' review (pp. 303-305) of the total fauna of the Bonneville and Lahontan basins led him to the conclusion that the life throws little light on the question of climate; in other words, it is inconclusive. He pointed out that the testimony of the freshwater molluscs, which are similar in the Bonneville, Lahontan, and Christmas Lake basins, so far as it goes, points to the conclusion that the lacustral epochs were epochs of relative cold, and favors the correlation of the high-water periods with the periods of largest glaciers. (2.) Late Phases of the Equus Zone These late phases of the Equus Zone are apparently distinguished by the absence of true camels and the presence of bison. At several points there is evidence of the existence of man in the presence of palolithic spear or arrowheads. The fauna is imperfectly known, and the above distinction between ‘early’ and ‘late’ is rather arbitrary at present. Early and late Pleistocene life of Kansas. — The geologic age of the widely scattered Pleistocene deposits of Kansas still awaits determination through the careful examination and comparison of the species. Williston, Haworth, Hay, and Darton agree in a broad way on the following geologic succession : Plains mar] = loess = Pleistocene. Mortar beds=Ogallala Formation = Pliocene ++ Upper Miocene. The uppermost Miocene and Pliocene is dominantly sandy, gravelly, and clayey, the consolidation into the so-called ‘mortar beds’ being due to the penetration of water and presenting no test of geologic age. The plains loess, or ‘marl’ (Hay) is a very irregular mantle; in places it is still in process of formation as an xolian accumulation over sodded surfaces. Near the base Matthew has collected well-petrified bones of Hquus; near the top one finds unfossilized bones of the recent bison. Some of the principal localities are as follows: TWELVE-MILE CREEK near Russell Springs, Logan County, Kansas (Fig. 194, 20). ‘STERNBERG’S ELEPHANT Ben,’ Logan County, Kansas (Fig. 194, 20). GoopLAND, Sherman County, Kansas (Fig. 194, 20, approximately). Harper Townsuip, McPherson County, Kansas (Fig. 194, 19). McPherson County, Kansas.2— The watershed between the Kansas and Arkansas river systems crosses at right angles a shallow trough about ten miles wide in McPherson County. This trough contains sediments con- sisting of: 1 Gilbert, G. K., Lake Bonneville. Monogr. U.S. Geol. Surv., Vol. I. Washington, 1890. 2 Lindahl, J., Description of a Skull of Megalonyzx leidyi, n. sp. Trans. Amer. Philos. Soc., n.s., Vol. XVII, Jan. 2, 1891, pp. 1-10. 462 THE AGE OF MAMMALS 4. Fine dull-orange colored loam, upward of seventy-five feet in thickness, occasionally resembling loess. 3. Stratum of voleanic dust several feet in thickness, also seen at other localities, extending twelve miles across the trough. 2. Stratum of clay, not of great horizontal extent. 1. Gravel and sand containing boulders, clay, fragments of Cretaceous shales. Remains of Megalonyx, Equus. In the bottom of these fluviatile gravels a skull of Megalonyx leidyi was discovered by Lindahl, as well as remains of Equus. If Megalonyx was a Fic. 201.— Skeleton of the Lower Pleistocene peccary Platygonus leptorhinus. In the American Museum of Natural History. forest-dweller, this discovery affords some evidence that it followed the river-border forest lines into Kansas in early Pleistocene times, also that it was capable of withstanding considerable cold. The study of the region and the deposits shows that the making of the gravel and sand was coin- cident with a period of increasing humidity; also that ice-flooding may have been present as an effective transporting agency. Goodland, Sherman County, Kansas.— In 1894 a most interesting discov- ery was recorded by Williston at Goodland, north of Fort Wallace, in the extreme western part of the state.' Nine specimens of the large peccary 1 Williston, S. W., Restoration of Platygonus. Kansas Univ. Quart., Vol. III, 1894, pp. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 463 Platygonus (compressus) leptorhinus were found lying close together as though a herd of the animals had been overcome by some sudden catastrophe. They lay about nine feet below the surface, with heads directed toward the southwest, the heads of the hinder lying upon the posterior parts of the more anterior ones, and the bones all or nearly all in the position they had been at the time of the animals’ death. This crowding together would in- dicate that the animals were overtaken either by a dust storm, a snowstorm, or a blizzard, just as herds of sheep are found at the present time. ‘Sternberg’s elephant bed,’ also in Logan County, Kansas, contains numerous remains of the Columbian mammoth (£. colwmb7), a large species of wolf (Canis), as well as a smaller canid of about the size of a coyote. Fic. 202.— The Lower Pleistocene peccaries of North America of the genus Platygonus. After original by Charles R. Knight in the American Museum of Natural History. Twelve-mile Creek, Kansas (Fig. 194, 20).— On this tributary of the Smoky Hill River has been discovered the richest deposit of the Pleistocene of Kansas. In the blue-gray layers directly underlying the recent plains layers are recorded remains of several species of mammals, including Elephas columbi, Platygonus compressus, Bison occidentalis. The stratum contain- ing the bison was about two feet in thickness and composed of fine silty material of bluish-gray color. The bone bed when cleared off was about ten feet square, and contained the skeletons of five or six adult bison, of two or three younger ones, together with a foetal skeleton within the pelvis of one of the adults.'. The animals evidently all perished together. In 1 Williston, S. W., On the Occurrence of an Arrow-Head with Bones of an Extinct Bison. Trans. Internat. Congr. Americanists, 1902, pp. 335-337. 464 THE AGE OF MAMMALS removing the bones of the largest of these skeletons an arrowhead was discovered underneath the right scapula, imbedded in the matrix, but touching the bone itself. Williston is entirely satisfied of the authenticity of this discovery. The evidence that man was contemporaneous with the extinct species of bison (see p. 497) is of the greatest importance. The fauna of the Kansas Pleistocene as summed up by Williston (1897) * was in part as follows: Mastodon americanus Platygonus compressus Elephas columbi Camelops kansanus Elephas (?) imperator Megalonyzx leidyi Bison occidentalis Mylodon Bison alleni Canis lupus Bison bison Canis (?) latrans Alces (?) sp. Geomys bursarius Equus, several species The simultaneous death of small herds of peccaries as well as of bison points to the existence of these animals during severe conditions of climate subject either to violent winter storms, or to the prevalence of great dust clouds. A high, cold wind storm, at very low temperatures, carrying with it great volumes of dust (loess), would account for the death and rapid burial of small herds of animals seeking shelter in some gully. 2. Mip-PLEIstocENE MAMMALS OF THE ForRESTED REGIONS. THE SECOND FAUNA This is a temperate and south temperate, chiefly forest and meadow fauna, indicating very favorable conditions of life. Herbivorous and car- nivorous mammals. This fauna is chiefly known in mid-Pleistocene times. The second great faunal group of North America is the Megalonyx Fauna, named by Cope after the great sloth which predominated and was widely distributed from the Atlantic to the Pacific. The most important question is that discussed above (pp. 453, 454), whether this is a forest fauna contemporaneous with the distinctive plains fauna of the Equus Zone. The forest types and plains types of North America are very different to-day and were undoubtedly very different in Pleistocene times. Our present con- clusion is that there are indications that the Megalonyx fauna is partly contemporaneous with, partly successive to, the plains fauna of the Equus Zone in the localities above described. This is a rich and magnificent fauna, by no means dwarfed or impov- erished. It is everywhere distinguished by the presence of Megalonyx, by the absence of arctic, tundra, and steppe types. It is distinctively the 1 Williston, S. W., The Pleistocene of Kansas. Univ. Geol. Surv. Kansas, Vol. II, 1897, pp. 299-308. —— PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 465 fauna of a temperate climate, becoming north-temperate. Associated with Megalonyx, at least in the earlier periods of this great life zone, we find the true, or typical Mylodon of the East. According to the locality, whether forest, meadow, or plain, we find also the American mastodons, the Colum- bian mammoth, tapirs, horses, camels, peccaries, bison, and moose. The enemies of this herbivorous fauna are North and South American types of By permission of C. S. Prosser. Fic. 203.— The giant ground sloth, megalonyx, an immigrant from South America. Skele- ton of the North American Pleistocene Megalonyx jeffersoni. In the Ohio State University Museum, Columbus, Ohio. bear, very widely distributed, saber-tooth tigers, as well as large lion-like cats, and all the modern types of American canids and felids. The American deer (Odocoileus) was very abundant in the forests, but it is noteworthy that the large European deer or American wapiti (Cervus) is nowhere recorded. We note everywhere the absence of the true musk ox (Ovibos), although certain of its relatives or precursors are recorded in late phases of this zone, and are actually found in certain of the same de- posits, such as the Big Bone Lick, Kentucky. It is probable, however, that such mingled deposits are successive rather than contemporaneous. Geological conditions. — Few sections are available to show the geologic conditions under which this fauna occurred. Such sections should now be taken and published from many different points. 24H 466 THE AGE OF MAMMALS Characteristic mammals. — In the various grand deposits of the forested regions of the Hast and far West in which the mammalian life is recorded, successive phases of this great period of time, which will undoubtedly be divided into sub-zones, are indicated in the very gradual extinction of the older forms and the appearance of newer forms, including modern species. In a broad way this fauna seems to correspond with the second faunal zone of Europe, 7.e. it contains the animal life of a temperate climate; in other words, it does not embrace any mammals of the northern tundras or steppes; neither the typical musk ox (Ovibos), the reindeer (Rangifer), nor the true northern mammoth (EL. primigenius) are within it. In addition to what is noted above, the prevailing mammals of this fauna appear to be as follows: Columbian mammoth (H. columbi), in the west and southeast. Mastodon (M. americanus), very abundant in the east, rare in the west. Horses, fairly abundant in all parts of the United States. Tapirs, fairly abundant in the forested regions of the east and southeast, not recorded in the west. Llamas, no longer found in the east and southeast, but surviving in the west, perhaps in Oregon, and certainly in California until near the close of this life zone. Mylodon, sometimes associated in earlier deposits with Megalonyz, disappearing in the more recent deposits. Megalonyx, surviving throughout, abundant in the east and on the Pacific slope. Megatherium, recorded in association with this fauna at Skidaway Island in Georgia and in South Carolina. Bison (B. latifrons, B. antiquus), widely distributed in the east and west. Moose (Alces), appearing in the west, doubtfully recorded in the east. Virginia deer (Odocoileus), abundant. The peccary (Mylohyus) replaces Platygonus, or represents it in the forest fauna. Relatives of the great musk sheep, or musk ox (Huceratherium, Preptoceras), appearing in late deposits in the west. Mountain goat (Oreamnos) of the rupicaprine family, appearing in late deposits in the west. The marmot (Marmota), appearing in late deposits in the west. Tree porcupines (Hrethizon), widely distributed throughout the United States. Castoroides, a giant beaver-like rodent, widely distributed in the eastern and middle states, but apparently not extending to the south. i : : PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 467 Saber-tooth tigers (Smilodon), surviving throughout. Large lions (Felis atrox), in the southwest and west. Bear, of the North American black bear type (U. americanus), also a giant bear allied to the South American cave bear (Arcto- therium),! widely distributed throughout the United States. Old World deer (Cervus), not recorded. Some of the great deposits in which the more or less successive phases of this fauna have been discovered are placed in the accompanying column in ascending chronologic order so far as their relative age can be determined at present: More recent 9. Bia Bonr Lick, Boone County, Kentucky (Fig. 194, 8). Intermediate 8. SAMWEL Cave, Shasta County, California (Fig. 194, 30). a 7. Porrer CREEK Cave, Shasta County, California (Fig. 194, 30). 6. Wasutucna Laks, Franklin County, Washington (Fig. 194, 32). i 5. Rancuo La Brea, the asphalt beds of southern California (Fig. 194, 28). ob 4. AsHuEy River, South Carolina (Fig. 194, 11). 3. FRANKSTOWN Cave, Blair County, Pennsylvania (Fig. 194, 3): Earlier 2. Tue Port KENNEDY Cave, Schuylkill River, Pennsylvania (Fig. 194, 4). 1. Arron Junction, Iowa, belonging to the first or Aftonian Interglacial epoch (Fig. 194, 23). Aftonian Interglacial stage. —One of the most fortunate discoveries in recent years is that of a rich deposit of mammalian remains in gravels of the Aftonian Interglacial period, which lie clearly between the drifts of the pre-Kansan and Kansan Glacial epochs.2, These mammals apparently be- longed to the early part of the Mylodon or Megalonyx life zone, and are of exceptional importance in enabling us to correlate this zone with the first Interglacial epoch in North America. The specific determinations have not yet been made positive, but there is little doubt that we have here association of sloths, camels, bison, horses, Columbian and possibly im- perial mammoths, as well as mastodons. There are also foot bones of dwarf horses which resemble those of the protohippine section. An anomalous feature is the presence of a large antler which suggests that of the wapiti, or true Cervus. The teeth of the horses agree in size with those of EL. paci- * 1The name Arctodus (Leidy) is in a sense preoccupied by Arctodon, and should not be re- vived, because based upon an indeterminate type. 2 Calvin, Samuel, Present Phase of the Pleistocene Problem in Iowa. Bull. Geol. Soc. Amer., Vol. XX, Mar. 18, 1909, pp. 133-152. 468 THE AGE OF MAMMALS ficus and E. occidentalis. Among the equine remains are hock bones, or calcanea, of exceptional size, indicating the presence of a horse of large dimensions; and there were also small, fine-limbed types of horses. The elephant teeth chiefly belong to the Columbian mammoth, presenting about twenty enamel folds in a space of ten inches. One molar approaches the true northern mammoth (#. primigenius) in the possession of twenty-five folds in a space of ten inches. At the opposite extreme is a tooth which exhibits folds varying from thirteen to fifteen in ten inches, which appears to indicate the presence of the imperial mammoth (EH. imperator). (See Fig. 190.) The identifications of LE. primigenius and E. imperator in this fauna, however, await final confirmation. This would be the first positive association of these species with the Megalonyx, or Mylodon fauna in early mid-Pleistocene times. Upper Lake Lahontan beds. — The special importance of the few mam- malian remains found in the Lake Lahontan deposits is that they are definitely recorded geologically. Proboscidean bones are found in the ‘in- termediate gravels’ in the Lahontan basins (equivalent to the gravels of the inter-Bonneville epoch), also in the ‘Upper Lahontan beds’ (equivalent to the ‘white marl’ of the Bonneville). There is no doubt that the fossils were all derived from the ‘upper lacustral beds’! ; they include an elephant (? FE. columbi), a horse, a bison, and a llama, none of which has been iden- tified specifically. In the same ‘upper lacustral clays’ an obsidian spear- head was obtained (see p. 448), positively associated with proboscidean remains; there is no doubt that the mammalian remains all belong to the time of the last great rise of the lake (op. cit. p. 273). The pres- ence of bison would appear to indicate that these ‘upper lacustral clays’ and the fauna which they contain are of more recent date than the Silver 7 Lake Equus beds, with which they were correlated on insufficient grounds by Gilbert in his Bonneville memoir.? Port Kennedy Cave of Pennsylvania is situated on the right bank of the Schuylkill River, two miles below Valley Forge, Pennsylvania (Fig. 194, 4). As studied by Cope* and Mercer? this locality has yielded sixty-four species of mammals, of which twelve are known to be still in existence and forty to be extinct; the ratio of recent to extinct forms would, however, be greatly increased by more careful comparison and more conservative deter- mination. The animals were apparently collected here by a series of fresh- water inundations, carrying with them the clay, stones, and earth of neigh- boring levels, and the bones of mammals separated and scattered by 1 Russell, I. C., Geological History of Lake Lahontan, a Quaternary Lake of North- western Nevada. Monogr. U.S. Geol. Surv., Vol. XI, 1885, p. 238. ? Gilbert, G. K., Lake Bonneville. Monogr. U.S. Geol. Surv., Vol. I, Washington, 1890. ® Cope, E. D., Description of Some Vertebrate Remains from the Port Kennedy Bone Deposit. Proc. Acad. Nat. Sci. Phila., Vol. XI, 1876, Pt. 2, pp. 193-267. 4 Mercer, H. C., The Bone Cave at Port Kennedy, Pennsylvania, and its Partial Exca- vation in 1894, 1895, and 1896. Jour. Acad. Nat. Sci. Phila., Vol. XI, Pt. 2, 1899, pp. 269-288. Se ee PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 469 decomposition. The chasm into which these remains were swept is from sixty to seventy feet deep, and twenty to thirty feet in diameter at the mouth, with descending walls sloping inward and forming a well-like hole. It is evident that the cave was not fitted for human habitation, even if man had existed in America at the time. The remains were swept in by floods and not drawn in by animals, as in the case of many of the European caves. Fortunately a portion of the flora is preserved, consisting entirely of modern species of temperate type, such as the pin-oak (Q. palustris), white oak (Q. alba), bur-oak (Q. macrocarpa), the beech (F. ferruginea), the hazel- nut (Corylus), the pitch pine (Pinus rigida), the plum (Prunus), the pig nut hickory (Carya porcina), the shell-bark hickory (Carya alba), the Virginia creeper (Ampelopsis quinquefolia), and the thorn (Crataegus) (Mercer). Pennsylvania in mid-Pleistocene times must have been a land of forests, very similar to those of the present time. The tapirs and sloths are the only indications of temperate conditions of the winter climate or of the absence of extremely low temperatures. All the other mammals are of north temperate type. The remains of the giant sloths are most abundant, following which in order of frequency come those of the rabbits, tapirs, mastodons, and peccaries. Among the larger Carnivora, the bears were more numerous than the felines, such as the saber-tooth tigers and the jaguars. The identification of species is largely based upon well-preserved remains, and has passed under the critical eye of Cope and Mercer, but probably still awaits final and precise revision. Conspicuous by their absence are the elephants and the llamas, a fact attributable to local for- ested conditions because both these animals were probably living in the plains region of the West or in California at this time. One ruminant (Teleopternus orientalis) is described by Cope as an extinct ungulate, allied either to the deer or the camels. Matthew suggests its affinity to Ovibos. The fauna is distinctly divisible into forest, glade and meadow, and fluviatile types, as follows: The Forest Fauna The American mastodon (M. americanus) Two species of fox The extinct tapir (Tapirus haysit) Martens, wolverines, skunks, weasels The Virginia deer (Odocoileus) (Mustela, Gulo, Mephitis, Pelycictis) The extinct ground sloths (Megalonyx, Giant bear allied to the extinct bear of Mylodon) South America (Arctotherium haplodon) The Canadian tree porcupine (Hrethizon Black bear (Ursus americanus) dorsatum) Lynx, eyra, and (?)jaguar (Uncia inex- The squirrel (Sczurus calicinus) pectata) Rabbits and picas (Lepus, Lagomys) Voles, shrews, moles, and bats (Sycium, Blarina, Scalops, Vespertilio) 470 THE AGE OF MAMMALS To the forest fauna should be added an extinct species of turkey (Mele- agris altus), as well as the frogs (Rana) and several species of turtles allied to modern types. River Fauna Belonging to the fluviatile or river fauna were the following forms : The beaver and the otter (Castor, Lutra). Meadow Fauna To the meadow fauna may be attributed one of the sloths (Mylodon), as well as the following forms: An extinct bison (Bison) A giant coyote, or prairie wolf (Canis Two or three species of horses (EF. frater- priscolatrans) nus, E. pectinatus) Two species of saber-tooth tigers, (Smilo- An extinct species of peccary (Mylo- don merceri, S. gracilis) hyus) The American badger (7'axidea americana) Field mice, meadow voles and jumping A ruminant (Teleopternus) suggestive of mice (Hesperomys, Microtus, Zapus) affinity to Ovibos It will be observed that beside the camels and the elephants there are many other absentees, or non-arrivals, in thisfauna. There are no European deer (Cervus), no moose (Alces), and none of the gigantic sloths known as Megatherium. Giant sloths of this genus are confined to the southeastern states. The bison and the bear are the most conspicuous of the newly arriving Old World mammals which appear in this fauna. Among the surviving indigenous North American forms are the saber-tooths (Smilodon), the tapirs, horses, and peccaries. Among the latter the modern genus Mylohyus replaces Platygonus. Mylohyus is a large, long-muzzled, or doli- chocephalic’ peccary, with vestigial upper incisor teeth; it is quite distinct from Dicotyles. Among the animals of South American affinity are the porcupines, and the great sloths (Megalonyx and Mylodon). It is note- worthy that several modernized species of cats, one attaining the size of the jaguar (’. uncia), competed with the saber-tooths; also that the bear include both the typical North American and South American types. Summarizing this fauna on the basis of these determinations, there is a great predominance of extinct forms. Out of a total of thirty-six genera ten are now extinct, and out of forty-seven identified species twenty-nine are now extinct (Mercer). Frankstown Cave, Pennsylvania. — The rich deposits in the Frankstown Cave as investigated by Holland ! were apparently of somewhat more recent date than those of Port Kennedy. This is a large limestone cave which has yielded remains of thirty or forty species of mid-Pleistocene mammals. On the whole it strongly confirms the Port Kennedy fauna as an assemblage of highly characteristic life of the forested regions of Pennsylvania in mid- 1 Holland, W. J., A Preliminary Account of the Pleistocene Fauna Discovered in a Cave opened at Frankstown, Pennsylvania, in April and May, 1907. Ann. Carnegie Mus., Vol. IV, nos. 3 and 4, 1908. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 471 Pleistocene times. The absence from this cave of certain forms, such as Mylodon and Equus, may be due to local causes, since it represents a more purely forest fauna than that of Port Kennedy; it may indicate also a more recent period. The giant ground sloth (Megalonyx) is represented, though not abundantly. Mastodon remains (M. americanus) are very numerous, being represented by an adult and five or six immature specimens. The presence in this cave of these infant mastodons and of various species of artiodactyls, as- sociated with bones of a huge bear, suggest that the latter preyed upon these animals. This bear (Arcto- therium haplodon) is a huge form related to the extinct South American bear; it was somewhat larger than the modern grizzly, and capable of attacking the Fic. 204.— Group of American mastodons (M. ame- ricanus). After original by Charles R. Knight in the youn mastodons. There American Museum of Natural History. are a number of peccaries, one of which (Mylohyus pennsylvanicus) is a large animal with long tusks. Bison and three kinds of deer are found, one of the latter a large type which may represent the Cervalces of Scott, a moose. The small herbivorous and carnivorous fauna is similar to that of Port Kennedy. Again we note the absence of remains of the mammoth, reindeer, musk ox, and of the southerly Megatherium. It is a somewhat hardy temperate fauna. Ashley River, South Carolina (Fig. 194, 11). Equus fraternus — These deposits of the Ashley River Forma- Tapirus americanus tion of South Carolina attracted the attention of Mastodon americanus Gibbes and Agassiz as early as 1845, and were Megalonyx seriously examined by Leidy; but we owe Bison latifrons, chiefly to Francis 8. Holmes! the study of the species abundant in geologic conditions. The principal locality is the southeast at Ashley Ferry in a bluff about thirty feet 1 Holmes, F. S., Remarks on a Collection of Fossils from the Post-Pliocene of South Carolina. Proc. Acad. Nat. Sci., July 12, 1859, pp. 177-185; zibid., Remains of Domestic Animals among Post-Pliocene Fossils in South Carolina. Amer. Jour. Sci. (Ser. 2), Vol. XXV, 1858, pp. 442-443. 472 THE AGE OF MAMMALS Hipparion high, having at its basea Pliocene limestone Megatheriwm composed of marine shells, while the post-Plio- Mylodon harlani cene layer is a shallow river formation consist- Procyon ing of yellow sands with bands of ferruginous Didelphys clay four feet in thickness. Fiber The fossilized teeth are brown or black in Castor color. The remains of ancient or extinct species Alces of animals are mingled with those of recent spe- Dicotyles cies; thus the fossil tapir which occurs there, not distinguishable from the living T. ameri- canus, is an animal also distributed in Texas, Louisiana, Kentucky, Missis- sippi, Indiana, Ohio, and South Carolina. Again, the common gray rabbit (Lepus sylvaticus) is associated with fragments of the teeth of the great Megatherium and Mylodon. The original specific identifications are very doubtful, and are therefore omitted in the table opposite. The species of horse found here (EF. fraternus) is characteristic of the southeastern United States; it represents an animal of intermediate size with teeth scarcely larger than those of the domestic donkey (EZ. asinus), and of a very complex pattern. Rancho La Brea, southern California (Fig. 194, 28). — In southern Cali- fornia, about nine miles west of Los Angeles, is what promises to be the most remarkable deposit of Pleistocene mammals thus far discovered in America. As described by Merriam ! (1906) this deposit is fifteen feet or more in thickness and a quarter of a mile in extent. It is located im- mediately over a sharp fold of rock, heavily impregnated with petroleum, which, issuing to the surface, has evaporated, forming springs and pools of tar which have dried and hardened locally to the consistency of asphalt. It contains scattered bones in a remarkably fresh condition, and pieces of partly lignitized wood. The remains are those of mammals and birds. Among the latter are ducks, geese, pelicans, eagles, condors, and peacocks. The smaller mammals include mice, rabbits, and squirrels; the larger are represented by extinct species of coyotes, giant wolves, bear, saber-tooth tigers, horses, bison, camels, mammoths, and large ground sloths. In the early stages of the accumulation of the asphalt, the gummy surface appar- ently acted as a trap for unwary animals: where there were pools of water the water birds of all kinds were entrapped in the soft tar about the mar- gins, while the land birds and smaller mammals were ensnared in attempt- ing to reach the water. The larger percentage of the birds are water forms, and the larger herbivorous mammals are for the most part represented by young individuals. A relatively large number of carnivorous animals cor- responds with what is observed around recent asphalt pools. In attempting to estimate the age of this fauna we first observe the 1 Merriam, J. C., Recent Discoveries of Quaternary Mammals in Southern California. Science, n.s., Vol. XXIV, no. 608, Aug. 24, 1906, pp. 248-250. ee ee ee ee eee ———s ) Se PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 473 association of horses, mylodont sloths, saber-tooth cats, camels, and Colum- bian mammoths, indicating the life of mid-Pleistocene times. With these animals also occur the bison. The absence of remains of mastodons and tapirs may be due to local causes, since this fauna is chiefly that of the open plains or meadows which surrounded this ancient asphalt lake. The chief forest types thus far mentioned are the deer and the squirrrels. Among the characteristic species of mammals thus far recorded are two species of wolves, a saber-tooth (Smilodon californicus), a leonine cat (Felis Fic. 205.— Rancho La Brea, California.« Water pool with asphaltic margin and tar ooz- ing out at many points. Great numbers of animals have been entrapped at such localities in the past. Recently a barn owl was caught in the tar at the edge of the pool. Photograph by J. C. Merriam, 1909. atrox bebbi), a bison (B. antiquus), a mammoth (? E. columbi), a sloth (Paramylodon nebrascensis), and a horse (EH. pacificus). Among the birds, according to the studies of Miller,! the raptorial species predominate. No less than thirty-three individuals of the golden eagle (Aquila chrysaétos) have been recovered. Among the non-predaceous birds are the great blue heron (Ardea herodias), the American raven (Corvus corax), the Canada goose (Branta canadensis). A new form is Teratornis, a raptorial type. Especially novel is the determination of a fossil peacock,? because the 1 Miller, L. H., Teratornis, a New Avian Genus from Rancho La Brea. Univ. Cal. Publ., Bull. Dept. Geol., Vol. V, no. 21, Sept., 1909, pp. 305-317. * Miller, L. H., Pavo californicus, a Fossil Peacock from the Quaternary Asphalt Beds of Rancho La Brea. Univ. Cal. Publ., Bull. Dept. Geol., Vol. V, no. 19, 1909, pp. 285, 289, Pl. 25. 474 THE AGE OF MAMMALS Phasianinz belong to a group hitherto unrecorded in America. The present range of the sub-family of peacocks is now limited to the Oriental region of southern Asia, but fossil forms are recorded from the Miocene, Pliocene, and Pleistocene of Europe, and from the Siwalik beds of India. The occur- rence of this species (Pavo californicus) in America is therefore to be con- Fic. 206.—Skeleton of the great South American saber-tooth ‘tiger’ Smilodon neogeus of the Pampean Pleistocene. In the American Museum of Natural History. sidered in connection with the Pliocene invasion (p. 337) of the Pacific Coast by Asiatic antelopes. At Washtucna Lake, Franklin County, Washington! (Fig. 194, 32), there is a large proportion of forest and mountain types but there are no aquatic mammals.” Whether the animals found here are truly associated in the same level is not known. In the same neighborhood are boggy springs from which Elephas columbi and a species of Bison have been ob- tained, a fact which adds to the suspicion that this is a mixed fauna. This appears to belong to the latter part of the Hquus-Mylodon-Camelops Zone, and associated with these plains-living forms are remains of distinctively forest types, including two species of moose (Alces) and of Virginia deer (Odocoileus), as well as of a mountain sheep (Ovis montana). Among the felids we find the puma (Felis concolor), and a larger leonine cat (F. impe- rialis), as well as the lynx (F. canadensis). 1 Cope, E. D., The Vertebrate Fauna of the Equus Beds. Amer. Natural., Vol. X XIII, 1889, pp. 160-165. * Matthew, W. D., List of the Pleistocene Fauna from Hay Springs, Nebraska. Bull. Amer. Mus. Nat. Hist., Vol. XVI, Art. xxiv, Sept. 25, 1902, pp. 317-322. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 475 Afton, Indian Territory ! (Fig. 194, 18), is situated in the midst of a plain in the extreme northeastern part of Indian Territory, or north of the Arkansas River near its northern tributary, the Grand. In or near a spring were found one hundred mastodon teeth, twenty mammoth teeth, beside a considerable number of teeth of fossil bison and horse, as well as an entire deposit of implements and recent bones. The prevalence here of the great extinct mammals may be attributed to their frequenting the spring in wet Fig. 207. — The Lower Pleistocene saber-tooth tiger Smilodon neogeus, based on a skeleton from the Pampean Formation of South America. After original by Charles R. Knight in the American Museum of Natural History. seasons. Especially interesting is the identification of both varieties of the mammoth, the Columbian and the imperial mammoth. The human imple- ments and remains of more recent animals are matters of secondary asso- ciation (see p. 496). The Erie Clays (Fig. 194, 5) are extensive deposits on the southern shores of Lake Erie, near Cleveland, constituting a ‘forest bed’ containing mastodon, elephant, and Castoroides.* Potter Creek Cave, California’ (Fig. 194, 30).— Environmental conditions of the Pacific coast were quite different from those in the Middle and Southern 1 Holmes, W. H., Flint Implements and Fossil Remains from a Sulphur Spring at Afton, Indian Territory. Ann. Rept. U.S. Nat. Mus., 1901, pp. 233-252. * Dana, J. D., Manual of Geology. 4th edition, 1895. 3 Sinclair, W. J., A Preliminary account of the exploration of the Potter Creek cave, Shasta County, Cal. Science, n.s., Vol. XVII, no. 435, May 1, 1903, pp. 708-712; Sinclair, W. J., The Exploration of the Potter Creek Cave. Univ. Cal. Publ. Am. Arch. Ethnol., Vol. II, No. 1, 1904, pp. 1-27; Sinclair, W. J.,. New Mammalia from the Quaternary Caves of Cal- ifornia. Bull. Dept. Geol. Univ. Cal., Vol. IV, 1905, pp. 145-161; Sinclair, W. J., and Fur- long, E. L., Huceratherium, a New Ungulate from the Quaternary Caves of California. Bull. Dept. Geol. Univ. Cal., Vol. III, 1904, pp. 411-418; Merriam, J. C., Recent Cave Explora- tion in California. Amer. Anthropol., n.s., Vol. VIII, April-June, 1906, pp. 221-228. 476 THE AGE OF MAMMALS states. The glaciation on this coast occurred comparatively late in Pleistocene times, and was of the Alpine type, that is, confined to the higher mountain levels. It is quite possible, therefore, that many kinds of mammals, such as the elephants and camels, survived in the comparatively mild climate of the Pacific after they had become extinct in more easterly regions. These suggestions are made in the course of the admirable studies of Merriam, Sinclair, and Furlong (1903-1906) on the very rich fauna of Potter Creek Cave in Shasta County. The life here is quite as varied as that of Port Kennedy, but there are many more still existing species. Out of thirty- seven genera and forty-nine species of mammals, eight genera and twenty-two species are known to be extinct, while thirty of the genera and twenty- two of the species correspond with living forms. The now extinct forms found in this cave are the giant bear (Arcto- therium), peccaries, camels, ground sloths, mastodons, mammoths, and the _ horses. This includes the entire large fauna, excepting the Virginia deer. The living forms found Fic. 208.— Skulls of (A) American extinct bear in this cave embrace nearly Arathi, (B) recent black, ean. rou ameret the entire existing mammalian fauna of northern California, Oregon, and Washington, with the exception of the mountain sheep (Ovis montana) and the wapiti (Cervus), neither of which occur in the Potter Creek deposits. Conspicuous among the new arrivals is the mountain goat (Oreamnos), the first member of the rupicaprine division of the antelope family to be recorded in North America. Here also occurs an extinct ungulate (Huceratherium) with affinities to the sheep (Ovine) and to Ovibos. As compared with the Port Kennedy Cave or even with the asphaltum deposits, we observe the absence of certain very characteristic early Pleis- tocene forms, especially the saber-tooths (Smilodon) and the giant tapirs. It is of course possible that these absences are due to local causes. The saber-tooths certainly frequented the plains and pampas and survived into late Pleistocene times in North America (Conard Fissure). Similarly, Mylodon, the early Pleistocene sloth, does not occur here, while Megalonyz, a forest and foothill edentate, is abundant. It is a very striking fact that the Columbian mammoth (E. colwmbi) is found here, as well as the forest-dwelling mastodon, this being the earliest record of the mastodon on the Pacific coast. Certainly to be reckoned ————- PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 477 among the older surviving forms of California at this time are the horses of the characteristic species of the Pacific coast (2. pacificus, E. occidentalis) and a camelid. Here, too, are remains of the bison (Bison sp.). Among the smaller artiodactyls are the peccaries, doubtfully determined as Platy- gonus. It is a very striking fact that, while the American deer (Odocoileus) are abundant, there is no trace of the Old World deer (Cervus). Preying upon this herbivorous fauna is a highly varied and, on the whole, very modern group of Carnivora. As in the Port Kennedy Cave, we ob- serve among the Urside remains both of the typical black bear of North America (U. americanus) and of the giant bear of South American affinity (Arctotherium). Among the cats is a very large species resembling the puma (F. concolor), and the lynx. Among the wolves and foxes we discover the gray fox of northern California (Urocyon townsendi), the red fox of the Cascade Mountains (Vulpes cascadensis), a large extinct species of wolf (Canis indianensis), also the badger, the raccoon-fox of California (Bassa- riscus raptor), also California types of skunks and weasels. The marmot (Marmota) is among the new arrivals. A small rodent fauna, chickarees (Sciurus), flying squirrels (Sciwropterus), the spermophiles (Spermophilus), the chipmunks (Hutamias), the hares and rabbits (Lepus, 4 sp.), the wood rats (Teonoma, Neotoma), the meadow voles (Microtus), the gophers (Thomomys), are of western mountain or Pacific type. We also discover here the first of the sewellels (A plodontia), the ancestry of which has been traced in the American Oligocene (p. 229). The fauna as a whole includes a mingling of plains and forest types, such as would be fitted to the topography of this region in Quaternary times; grazing camels, bison, horses, elephants may have inhabited the broad valley, while the deer roamed over the hillsides, and the higher peaks afforded a congenial home for the Rocky Mountain goat (Oreamnos). The cave seems to have remained open for a long time, receiving bones swept in from different levels by freshets in seasons of wet weather. The fauna is not too old to preclude the idea of the contemporaneity of man. In the opinion of certain anthropologists (Putnam) the presence of Homo is indicated by the fashioning of bone implements; others (Merriam, 1906) regard this evidence as inconclusive (see p. 498). Samwel Cave. (Fig. 194, 30).—In Samwel Cave, Shasta County, California, as described by Furlong,! has been discovered a mammalian fauna of somewhat more recent origin than the Potter Creek Cave. Split bones with polished surfaces and chipped obsidian and basalt fragments have been found here which may represent the work of man; in fact, Putnam (1905) ? considers that man existed at this time in California. The 1 Furlong, E. L., The Exploration of Samwel Cave. Amer. Jour. Sci., Ser. 4, Vol. XXII, no. 129, Sept., 1906. ? Putnam, Evidence of the Work of Man on Objects from Quaternary Caves in California. Amer. Anthrop., n.s. Vol. VIII, 1905, pp. 229-235. 478 THE AGE OF MAMMALS opinions of Putnam and Merriam on this point will be cited on a later page. Of the twenty species of mammals determined here, about one quarter, or 25 per cent, are extinct. Of the characteristic animals of the mid-Pleistocene, or Megalonyx Zone, there still remain Megalonyx, the Columbian mammoth, and the western horse, which appear to be in this locality the last survivors of this great mid-Pleistocene fauna. No mylodonts, mastodons, or camels occur. The American black bear (U. americanus) is found here, but the giant South American bear (Arctotheritwm) is not recorded. Of the new- comers the sheep-like ungulate (Huceratherium), with affinities to the musk Ox, again occurs, as well asa related form (Preptoceras). The remainder of the fauna is the modern characteristic mountain fauna of North America, similar to that described above at Potter Creek, and very similar to that of the present day with the exception of the fact that the wapiti, or European deer (Cervus), is still absent. Big Bone Lick, Kentucky. (Fig. 194, 8).— One of the most famous of these deposits is that known as the Big Bone Lick, Kentucky, discovered in 1830, twenty miles southwest of Cincinnati, where remains of enormous herds of mastodons and Columbian mammoths are mingled with more sparse remains of other members of the Megalonyx fauna. From the very early account of Cooper ! we take these notes. The relative frequency is a point of especial interest, as shown in the following table: Mastodon americanus 100 individuals Elephas columbi 20 individuals Bison antiquus* 2 individuals Bison latifrons * 1 individual Odocoileus virginianus 2 individuals Cervus canadensis (?)individuals Alces americanus (?)individuals (?)Rangifer Ovibos (?) Equus Megalonyx jeffersont A feature of great interest is the occurrence here of Ovibos and Rangifer, two members of the third Pleistocene fauna. In fact, the presence of the true deer (Cervus), the musk ox (Ovibos), and the reindeer (Rangifer), if properly determined, is an indication either of the approach of the fauna of the third life zone, or that these Big Bone Lick deposits bridged over the periods of the second and third zones. 1 Cooper, W., Smith, J. A., and De Kay, J. E., Report to the Lyceum of Natural History on a collection of fossil bones disinterred at Big Bone Lick, Kentucky, in September, 1830, and recently brought to New York. Amer. Jour. Sci., Vol. XX, 1831, pp. 370-372; also, Cooper, W., Notices of Big Bone Lick. Monthly Amer. Jour. Geol. Nat. Sci., I, 1831, pp. 158-174; 205-217. 2 Authority, F. A. Lucas, The Fossil Bison of North America. Proc. U.S. Nat. Mus. Vol. X XI, no. 1172, 1899, pp. 755-771, Pll. lxv—Ixxxiv. Se EE PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 479 Fic. 209.—Skeleton of the famous ‘ Warren Mastodon’ (Mastodon americanus), found in a Pleistocene deposit of New York State. In the American Museum of Natural History. Fic. 210.— The American mastodon (M. americanus), modeled on the skeleton of the ‘Warren Mastodon.’ After original by Charles R. Knight in the American Museum of Natural History. 480 THE AGE OF MAMMALS It would be natural to suppose that these remains were of animals attracted by the salt deposits at this locality, but the waterworn and broken condition of the bones, as well as the entire scattering of the skeletons, indicates that the remains were assembled through floods. It is remarkable that no carnivorous animals were reported with the original discovery. Characteristic Mid-Pleistocene Mammals of the Second Fauna Mastodons. — The known geographic range of the American mastodon extends over the entire United States northward to Lake Winnipeg and British Columbia, with a single find reported in Alaska and two finds reported in Nova Scotia. East of the Hudson and of Lake Champlain it is rare; thus very few specimens have been found in New England. In New York the geographic and geologic distribution has been most carefully examined by Clarke;! he finds no evidence of the existence of mastodons before the Glacial period; they first appear in New York State in what is known as the pre-Wisconsin Interglacial (see p. 444). The time of their disappearance or extinction seems to have been nearly coincident with the melting and recession of the ice floes, glacial lakes, and glacial streams, in other words, post-Glacial times. Mastodon and EF. columbi remains are found in surface deposits above the latest glacial drift in Indiana and Ohio, and according to the opinion of some observers (Brown) these genera ex- isted in the Central States long after glacial influence. In the western part of New York the remains are found imbedded in old glacial lake terraces caused by the damming back of ice floes. In eastern and southern New York remains are invariably found in more or less completely drained swamps and peat bogs, separated by narrow rocky divides, which apparently formed the chief lines of north and south migration of these great quadrupeds. That these animals survived to a late stage in post-Glacial history and were con- temporaneous with man is especially indicated by the mastodon excavated at Attica, New York, by Clarke in 1887 (op. cit., p. 864); beneath the bones of this skeleton were found several pieces of charcoal. In another part of the same swamp, under four feet of muck and one foot below the level of the bones, was found a considerable quantity of charcoal with broken pottery. As compared with the mammoth, the mastodon (Figs. 209 and 210) is distinguished by its low forehead, its short, massive limbs, enormously broad pelvis, the height at the shoulders not exceeding 9 ft. (2.70 m.) to 9 ft. 6 in. It is probable that it was clothed with hair, with an undercoating of wool. In the only instance in which hair has been discovered it is described as coarse, long, and brown. The greatest length attained by the tusks is ten feet, the average in full-grown specimens being seven to eight feet. The 1 Clarke, J. M., Mastodons of New York. N. Y. State Mus., Bull. 69, Paleontol. 9, Nov., 1903, pp. 921-933. See also Lucas, Animals before Manin North America, New York, 1902. —————— PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 481 annular structure of the dentine appears to indicate (Osborn, 1908) that the growth was intermittent; an animal with tusks eight feet in length exhibits twenty-four of these growth rings, which may be interpreted as proving that it attained an age of more than twenty-four years. The in- dications are that mastodons were extraordinarily abundant; it is estimated by Clarke that they may have been at one time as numerous as the bison. At Fic. 211.— The Bison in Pleistocene times. Localities from which principal types and other specimens of fossil bison have been recorded. Authority of F. A. Lucas. 1. Bison bison. 2. Bison occidentalis. $3 Bison antiquus. 4. Bison crassicornis. 5. Bison alleni. 6. Bison ferox. 7%. Bison latifrons. Big Bone Lick, Kentucky, remains of mastodons far outnumber those of the Columbian mammoth, being five times as numerous as those of the mam- moth and a hundred times as numerous as those of the bison. If these animals were contemporaneous with man in post-Glacial times, it is possible that they may have been hunted or driven to extinction through his agency. 21 482 THE AGE OF MAMMALS Bison. — We owe to Allen (1876),! Lucas (1899),? and McClung (1908) 2 our knowledge of the skull and skeleton of the many kinds of great bison, or buffalo, which roamed over all parts of North America during Pleistocene times. As revised by Lucas, there are seven valid species of fossil bison, which had a widely extended geographical distribution from Florida to Alaska (Fig. 211). They also undoubtedly in part succeeded each other in geological time, the latest bisons culminating in the recent species, Bison bison, more or less fossilized remains of which have been discovered in Kentucky, Kan- sas, and in the loess deposits of Missouri. The early and gigantic form (B. latifrons) reflects the favor- able conditions of life during the Megalonyx Zone. In Texas, Mississippi, Georgia, Ohio, Kentucky, and Kansas remains of this species have been found. In some of! these Fic. 212.—Skulls of (A) the extinct bison of localities they are associated rac ee pete hE) ie sient ent ei ne) es a of Natural History. mastodon, the Columbian mammoth, and of the great sloths Megalonyx and Mylodon. The horn cores are so long and thick that they exceed by two feet on each side those of the existing Old and New World bison, as shown in the accompanying figure. Horns in the collection of the Cincinnati Natural History Society measure 6 ft. 6 in. (1.95 m.) along the curve from tip to tip. This measurement is exceeded by the magnificent horn cores discovered in Kansas and secured by Sternberg for the American Museum of Natural History; they measure 6 ft. across from tip to tip, and 8 ft. 6 in. (2.55m.) along the curve; this appears to be the record in size. Although the skeleton is unknown, we may judge from the size of the skull that B. latifrons far exceeded any of its living relatives. Remains of another ancient form, Bison antiquus, have been found in Kentucky and in California associated with remains of elephants, mas- todons, horses, and camels. Although a much smaller animal, it appears to have been a contemporary of B. latifrons in the Megalonyx life zone, but may have survived to a more recent date. It is considerably larger than 1 Allen, J. A., The American Bisons, Living and Extinct. Mem. Mus. Comp. Zoél. Har- vard Coll., Cambridge, Vol. IV, no. 10, 1876. 2 Lucas, F. A., The Fossil Bison of North America. Proc. U.S. Nat. Mus., Vol. X XI, no. 1172, 1899, pp. 755-771. 3 McClung, C. F., Restoration of the Skeleton of Bison occidentalis. Kansas Univ. Sct. Bull., Vol. IV, no. 10, Sept., 1908, pp. 249-254. = —_ PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 483 B. bison, and is readily distinguished by the position of the horns, which are placed almost at right angles to the long axis of the skull. The horns of another species (B. ferox), resembling those of B. latifrons, have been found in the Pleistocene of Nebraska. The Pleistocene of Idaho and Kansas has yielded the horn cores of a fifth species (B. alleni). The giant north- western bison found in Alaska, which may have existed also in eastern Siberia, is B. crassicornis. There also lived in Alaska, probably in late Pleistocene times, and ranged down into Kansas, the species B. occidentalis. This animal most closely resembled the living bison, with which it was probably contem- poraneous for a time. A complete specimen of a bull of this species was Fic. 213.— Skeleton of the extinct bison B. occidentalis. In the University of Kansas. After McClung. discovered with seven or eight other skeletons near Russell Springs, Logan County, Kansas, in association with a flint arrowhead.!. The skeleton as mounted in the Kansas Museum (Fig. 213) is considerably larger than that of the largest recent bison in length and height, and in the length of the hind limbs. The horn cores are similar in shape and proportions. Mountain antelopes. — A late arrival in the western mountain region only is the so-called ‘Rocky Mountain Goat’ (Oreamnos). This animal is the sole representative in North America of the very aberrant group of mountain antelopes known as the chamois sub-family, or Rupicaprine, a subdivision of the Bovide, comprising five widely scattered animals, which are distributed on mountain heights from the Pyrenees of Spain to the 1 McClung, Restoration of the Skeleton of Bison occidentalis. Kansas Univ. Sct. Bull., Vol. IV, no. 10, Sept., 1908, pp. 249-254. 484 THE AGE OF MAMMALS Rocky Mountains. These are the typical chamois (Rupicapra), the goral, the takin, the serow, and finally the American misnamed ‘goat.’ ! Tapirs. — The tapir of the Megalonyx Zone (T. haysii) has been dis- covered in Kentucky, Indiana, Mississippi, and South Carolina. This species is apparently more robust than the existing South American tapir. A somewhat smaller animal, referred by Leidy to 7. Americanus, is indis- tinguishable in size and form from the living 7’. terrestris of Central and South America. Its remains have been found in Texas, Louisiana, Missis- sippi, South Carolina, Virginia, Ohio, Illinois, and California. The tapir was undoubtedly one of the most characteristic animals of the Megalonyx life zone, especially in the forests of eastern North America. It apparently migrated to the South during the period of the Ovibos life zone. Horses. — As studied by Gidley? there were at least ten forms or species of horses in different parts of the United States and Mexico in Pleis- tocene times, distinguished by geographic distribution, by size, and by the proportions of the body and skull, and by the characters of the upper grinding teeth. The H. fraternus, found in the Ashley River, South Carolina, and characteristic of the southern United States, is still imperfectly known; it rep- resents a very small horse, with teeth scarcely as large as those of the Mexican donkey and of a very complex pattern. The EF. complicatus, first found near Natchez, Mississippi, belonging in the western, southern, and middle- western states, is a well-known animal characterized by teeth as large as those of the ordinary horse, but with a skeleton of intermediate size; the skull is especially distinguished by its short muzzle, in which respect it resembles that of an ass. From the Rock Creek Beds of western Texas comes the E. semiplicatus, which in certain cranial characters, as well as in the size and proportions of its teeth, seems to present a close relationship to the ass (2. asinus). On the Staked Plains of central Texas has been found £. scotti (see Fig. 14), intermediate in size between EL. complicatus and E. pacificus, with a long face, relatively large head, long body, short neck, resembling in its proportions the quagga (H. burchelli). From southwestern Texas comes also EL. giganteus, the largest species of horse hitherto recorded, the teeth exceeding those of the largest modern draught horses by more than one third of the diameter of the latter. In contrast with this is the Z. tau in the valley of Mexico, the smallest true horse known in America, more diminu- tive than any European species living or extinct. Associated with this in the valley of Mexico is EL. conversidens. The type of horse found in the Middle Pleistocene forested region of eastern Pennsylvania is H. pectinatus, from the Port Kennedy Cave. On the Pacific slope, California, has been found FZ. occidentalis, with teeth of 1Grant, Madison, The Rocky Mountain Goat. N.Y. Zodl. Soc. New York, 9th Ann. Rept., 1904, pp. 230-261. 2 Gidley, J. W., Tooth Characters and Revision of the North American Species of the Genus Equus. Bull. Amer. Mus. Nat. Hist., Vol. XIV, Art. ix, May 31, 1901, pp. 91-141. Another horse found in California is EH. pacificus, best PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 485 known, however, in Oregon; next to HL. giganteus this is the largest American Pleistocene horse; the skeleton indicates a horse of about the size of an uniformly simple pattern, a horse of about the size of FE. complicatus, i.e. ordinary draught horse; the skull is proportionately larger. about 14} hands. we ) sore a Fd 2 { rae! = circles. Cor = Cordilleran ice sheet, Agassiz, A, Lake Present distribution of musk oxen Pleistocene lakes = dotted areas. solid black. Labradorean. This was contemporaneous with the Megalonyx fauna. Its remains Lions. —It is a most interesting case of faunal parallelism that the mid-Pleistocene of America, like that of Europe, developed a leonine species Fie. 214. — The Musk Ox in glacial and recent times. Localities in which Pleistocene fossil of cat. Maximum glaciation of North America shown in oblique lines. were first found by Leidy in 1853 near Natchez, Mississippi, and described Kee = Keewacin, Lab L, Lake Lahontan, B, Lake Bonneville. musk oxen have been recorded 486 THE AGE OF MAMMALS as Felis atrox, while a larger Pleistocene form in California was named F. imperialis. Confirmation of its character has recently been obtained ! in the Asphalt Beds of Rancho La Brea. The skull (Felis atrox bebbi) is remarkably similar to that of the existing African lion and the cave lion of the European Pleistocene. This California variety approaches closely in measurements Leidy’s type jaw from Natchez, Mississippi, with some specific variations. The muzzle is very wide compared with the length of the skull. As in the European form, the superior outlines of the skull approach the lion more closely than the tiger. The related form, F’. impe- rialis, from Livermore Valley, California, associated with remains of B. latifrons, and of Elephas, Equus, and Canis indianensis, possibly occurs in the Potter Creek Cave ? and is reported at Washtuena Lake, Washington. It is undetermined whether it is really a distinct species. Summary.— The mammals which have been described above as con- temporaneous with Megalonyx in such widely scattered regions as Pennsyl- vania and California appear to constitute a great group adapted to tem- perate and north temperate conditions of climate. Except in the probably successive deposition of Big Bone Lick, not a single boreal, tundra, or steppe species occurs among them; on the other hand, there is a large element of hardy species of southern affinity, such as the sloths. 3. THE FAUNA OF THE OviBos ZONE, PERHAPS CORRESPONDING WITH THE ARCTIC AND TUNDRA PERIOD IN EUROPE This is an impoverished fauna, reduced in numbers and in variety. Full of modern or existing species, far to the south of their present range. We thus enter a new faunal zone, which may be called the zone of Ovibos, or the musk ox. The advent of this northern form in the central United States, as shown in the accompanying figure, is perhaps coincident with the period of the last great glacial advance which is recorded in the great terminal moraine. The glaciated, or partly glaciated areas of the United States at this period of maximum advance are here mapped as recorded by Dana. The known southerly distribution of the musk ox in Pleistocene times is independently plotted from various records, yet it appears to coincide in the most remarkable way with the southerly boundaries of the great ice sheet. (See Fig. 214.) The mammals of this period of maximum glaciation and of the subsequent recession of the ice may be considered together as constituting the third great life zone of the American Pleistocene, which may correspond with the third life zone in Europe. It by no means rests upon the same positive or cumulative evidence as 1 Merriam, J. C., The Skull and Dentition of an Extinct Cat Closely Allied to Felis atrox Leidy. Univ. Cal. Publ., Bull. Dept. Geol., Vol. V, no. 20, Aug., 1909, pp. 291-804. 2 Bovard, J. F., Notes on Quaternary Felide from California. Univ. Cal., Publ., Bull. Dept. Geol., Vol. V, no. 20, Sept., 1907, pp. 155-166. sa Sell PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 487 the second, or Megalonyx life zone, and cannot be described with equal certainty because only a single, rich faunal assemblage is known, namely, that of the Conard Fissure in Arkansas. It appears to be defined negatively by the absence of great sloths (Mylodon and Megalonyx) and of the tapirs. There is less certainty as to the absence or extinction of the llamas at this time. Positively, it is distinguished by the arrival of the musk ox (Ovibos), the reindeer (Rangifer), and the Old World deer or wapiti (Cervus). It is important to note that in Big Bone Lick (p. 478) these disappearing and newly arriving forms are recorded together, although they may have been successively deposited. The chief localities are: 4. Anaska, ‘ground ice,’ Kowak clays, ete., scattered deposits. 3. ConarpD Fissure, Newton County, Arkansas. (Fig. 194, 17.) 2. Scattered deposits in the Middle and Western states. 1. Bia Bone Lick, Kentucky, in part (see p. 487). If the Conard Fissure of Arkansas is rightly placed in this zone, it appears that the horses still survive, although in diminished numbers. The saber- tooth tigers also survive in modified form. It is probable, but by no means certain, that the modern mammoth (F. primigenius) reached its most south- erly distribution near the city of Washington at this time. The American mastodons certainly survived in the eastern forests. The characteristic types of this period may, therefore, be summarized as follows: Musk oxen (Symbos, Ovibos), ranging south to the central states. Reindeer or caribou (Rangifer). Old World or wapiti deer (Cervus), in the central and southern states. Bisons (? B. occidentalis, ? B. bison). Mastodons, in the eastern forests. Northern mammoths (Elephas primigenius). Last saber-tooth tigers (Smilodontopsis), in the southern states. Last horses, in the southern states. Walrus (Odobenus), along the south Atlantic coast. Conard Fissure of Arkansas (Fig. 194, 17). —It is important to note (Fig. 214) that this locality lies about one hundred and fifty miles south of the most southerly extension of the great terminal moraine. As recorded by Brown ! (1908) of the American Museum of Natural History, this fissure has yielded remains of thirty-seven genera and fifty-one species of mammals, of which only four genera and twenty-four species are now extinct; it thus presents a great contrast to the Port Kennedy assemblage. The presence of an extinct genus of musk ox (Symbos), of the wapiti (C. canadensis), and of many small rodents and carnivores which at thé present time range far 1 Brown, Barnum, The Conard Fissure, a Pleistocene Bone Deposit in Northern Arkansas: with Descriptions of Two New Genera and Twenty new Species of Mammals. Mem. Amer. Mus. Nat. Hist., Vol. IX, Pt. iv, Feb., 1908. 488 THE AGE OF MAMMALS north of Arkansas, shows that the climate was of a northerly type similar to that of the forested regions of British Columbia. With the exception of the musk ox — which, it must be remembered, formerly had a more south- erly range than at present — it is certainly in no sense a tundra or arctic fauna. The assemblage, nevertheless, indicates the crowding southward of northerly forms, such as may have occurred during the advance of the great ice sheet. There is no evidence of the existence here at this time of Mega- lonyx, or Mylodon, of the tapir, mammoth, or mastodon. It would not be safe, however, to assume from this evidence that the tapir, mammoth, and mastodon were extinct in all other parts of the American continent at the time. The only four now extinct genera which give an ancient character to this fauna are the saber-tooth tiger, above mentioned, an extinct species of horse (EH. scotti ?), an extinct genus and species of peccary (Mylohyus), and the extinct genus of skunk (Brachyprotoma), three species of which are found in the Port Kennedy Cave. The condition of the bones and the association and predominance of certain forms indicate that this fissure was the home of several contem- poraneous species which preyed on still others and brought their remains into it. Cats and bears probably inhabited parts of this cavern, dragging in peccaries and deer; weasels occupied runways in the rock, which are filled with remains of mice, rabbits, and wood rats. Shrew and mice bones were probably introduced largely by owls, which may have lived on the ledges of the fissure. The fauna is typically that of a forest region, with open glades, similar to the present conditions of the same region in Arkansas. There are five species of shrews, three of which are now extinct, a mole, two bats, one living and three extinct species of skunk. Other mustelines are the fisher marten (Mustela pennanti), the mink (Putorius vison), and the weasel. The gray wolf (C. occidentalis) was accompanied by the red fox (Vulpes fulvus ?), and the gray fox (Urocyon sp.). The raccoon (Procyon lotor) was abundant. We observe the black bear (U. americanus), but, as in the Samwel Cave of California, there is no evidence of the giant South American bear which is found in all the earlier Pleistocene deposits of the Megalonyx Zone. Among the cats are lynxes and pumas, beside two species of the extinct saber-tooth (Smilodontopsis troglodytes, S. conardi). Among the larger Herbivora both the mule deer (Odocoileus hemionus) and the white-tailed deer (O. virginianus) are recorded, as well as the wapiti (C. canadensis) and the extinct genus and species of musk ox (Symbos aus- tralis). It is noteworthy that the peccary is not of the existing southwestern type (Dicotyles torquatus), but belongs to the genus (Mylohyus) character- istic of the Megalonyx Zone. The small rodent fauna is that of the present forested regions of the Rocky Mountain area. Canadian deposits. — The Iroquois Beach deposits (Fig. 194, 2) are con- sidered by Canadian geologists of post-Glacial age. They contain numerous PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 489 horns of reindeer (R. caribou), of the mammoth (#. primigenius), of the mastodon (M. americanus), of the wapiti (C. canadensis), and of the beaver (Castor fiber).! Seventy feet above the lake (Lake Ontario), on Burlington Bay, the western part of the lake, has been recorded the mammoth (Elephas jacksoni), a type probably referable to the true mammoth. The Alaskan fauna. — Alaska was free from glaciers except in its cen- tral mountainous belt. It presents a rich life in Pleistocene times. The bones @ ELEPHAS C eEQuUS A BISON @ RANGIFER @ oviBos @ ALCE 1 ODOBENUS 2 Genera not specified Fic. 215.— Map of Alaska showing localities where Pleistocene mammalian fossils have been , discovered. After Dall and others. Quackenbush, American Museum Expedition, 1908. of mammals are found widely distributed;? their scattered remains occur throughout the unglaciated region of Alaska and adjacent Canadian terri- tory in several quite distinct deposits: first, in the black muck accumulated 1 Geology of Canada, 1863, p. 914. ? Dall, W. H., and Harris, G. D., Correlation Papers. The Neocene of North America U.S. Geol. Surv., Bull. No. 84, 1892. 490 THE AGE OF MAMMALS in gulches and valleys of the smaller streams; second, in the fine elevated clays of the ‘Yukon silts’ and ‘ Kowak clays’; and third, in the more reeent fluvial and alluvial deposits.'. Of these the most remarkable is the ‘ground ice’ formation of Dall, in which solid beds of ice of considerable thickness take the place of rock strata, and are covered by beds of blue clay containing numerous remains of Pleistocene mammals. The distribution of these ground ice formations and of the ‘ Kowak Clays’ is plotted on the accom- panying Alaskan map, which combines the results of Dall and of Quacken- bush, the symbols indicating our present knowledge of the distribution of the principal types of mammals. This distribution includes, beside the above, bones recorded in river gravel deposits. In some of the clays the parts preserved are so complete as to indicate that the animals were mired entire, one such specimen with portions of the hair and wool having been discovered by Quackenbush.” Elephas primigenius, the hairy or northern mammoth. Elephas columbi (determination somewhat uncertain). Mastodon americanus. Ovis (determination somewhat uncertain). Ovibos moschatus, the true musk ox. Ovibos yukonensis, an extinct species. Symbos tyrelli, with much smaller horns than Ovibos. Ovis montanus, the mountain sheep. Oreamnos, the mountain goat. Rangifer sp. ind., caribou, probably the ‘barren ground’ variety. Bison crassicornis, a long-horned species. Bison occidentalis, resembling the recent bison. Bison alleni, with long, slender, much curved horns. Alces, the moose (? Alces americanus). Equus, species indeterminate. Ursus, of the size of U. americanus. Canis. Castor, the beaver. Odobenus, the walrus. Judging from the number of separate bones collected or examined by Quackenbush, the mammoth was everywhere the most abundant animal, the bison followed closely, the horse and caribou existed in lesser numbers, and other mammals were comparatively scarce. That the country was forested and the climate somewhat milder than that of the present time seems to be proven by the fact that large trees have been found associated 1 Gilmore, C. W., Smithsonian Exploration in Alaska in Search of Pleistocene Fossil Vertebrates. Smiths. Miscel. Coll., part of Vol. LI, Washington, 1908. * Quackenbush, L. S., Notes on Alaskan Mammoth Expeditions of 1907 and 1908. Bull. Amer. Mus. Nat. Hist., Vol. X XVI, Art. ix, Mar. 24, 1909, pp. 87-130. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 491 with horse and mammoth remains in regions which are now barren tundras with frozen subsoil. The preservation of the flesh and hair of the mam- moth found at Elephant Point was not due originally to freezing, but to burial in soft mud which protected the parts from bacterial decay; the parts of the body above the surface were rotted away. There is some evi- dence that these mud deposits were due to river flood-plain action and that =) 2 . 2 Fic. 216.— Bluff on the south side of Eschscholtz Bay, Alaska, where remains of many Pleistocene mammals have been found (‘big bone beach’). The cross indicates the spot where part of a mammoth skeleton with some skin and hair was discovered. After Quackenbush, American Museum Expedition, 1908. a part of the deposits have since become frozen. All are now covered by the thick vegetation of the tundras except where exposed at the seashore and along river borders. The contemporaneity of these Alaskan species is by no means demon- strated. They may represent several successive periods of Pleistocene time: the moose and reindeer in the forests, the horses and bison (typical grazers) grazing on the uplands, the elephants and rare mastodons grazing and browsing in the forest borders, the beaver building their dams from the forests along the streams. The musk oxen and caribou, adapted to the mosses and shrubs of the barren grounds, are indicative of different periods. Certainly the horse, the bison, and the elephants would have been 492 THE AGE OF MAMMALS favored by a dry or arid climate, even if cold. Dall’ remarks that the eleva- tion of the continental shelf under Behring Sea about 300 feet would have laid bare an enormous level plain covering most of the present area of Behring Sea. The diminished body of water in connection with the prevalence of the northwest trade winds would have given to this region such a dry climate as characterizes much of Siberia and the Yukon Valley in Alaska to-day, which actually suffers from severe summer droughts. Vast shallow lakes of muddy water might, as now happens in the same region, freeze solidly to the bottom and be covered with deposits of clay from the spring freshets, a condition explaining the great ice lenses of the ‘oround ice’ formation. Certain mammals might have been trapped in the quagmires formed by these clays. Finally, with the subsidence of the coast and the return of a milder climate, the ice lenses in the more northern and colder regions, especially where protected by the clays, by the freezing of the soil, and by the arctic vegetation, would be conserved to the present day. Characteristic Mammals of the Third or Ovibos Zone Distribution of musk oxen. — Beside the extinct short-horned musk ox (Symbos) found in Arkansas, remains of musk oxen are recorded ? at Fort Gibson, Indian Territory, in three localities in Missouri, in Trumbull County, Ohio, at Big Bone Lick, Kentucky, in two localities in Pennsylvania, at Council Bluffs, Iowa, and near Salt Lake City, Utah. In every instance the remains have been recovered either directly from glacial deposits or from deposits that may be correlated with some stage of the Glacial Period. The skull of a musk ox (Ovibos cavifrons), discovered in part of the glacial terrace near the Ohio River in West Virginia, one mile from Steubenville, was asso- ciated with the shoulder blade of a mammoth of undetermined species. The reasonable inference seems to be that the musk oxen moved southward before the advancing ice, and then retreated northward to their present areas of distribution. (See Fig. 214.) Cervalces. — An almost complete skeleton of an extinct moose was discov- ered in 1884 in the shell-marl deposit under a bogat Mt. Hermon, New Jersey, and described by Scott in 1885.3 Its occurrence so far south of the present range of the moose points to a cold climate in New Jersey, but whether this animal belongs to the Megalonyx or to the Ovibos Zone cannot be determined at present. It is a remarkably long-limbed form, perhaps in adaptation to its habitat in snowy regions. The unusual size of the lateral digits would also favor the supposition of walking in the snow, although they may have been an adaptation to swampy conditions. The antlers are large and 1 Dall and Harris, op. cit., p. 266. 2 Hatcher, J. B., Discovery of a Musk Ox Skull (Ovibos cavifrons Leidy), in West Virginia, near Steubenville, Ohio. Science, n.s., Vol. XVI, Oct. 31, 1902, pp. 707-709. 3 Scott, W. B., Cervalces americanus, a Fossil Moose, or Elk, from the Quaternary of New Jersey. Proc. Acad. Nat. Sci. Philadelphia, 1885, pp. 181-202. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 493 palmate, and are especially distinguished by broad inferior horizontal plates.! The animal, like the moose, was undoubtedly a tree-browser; the neck is so short in comparison with the limbs that the muzzle could not have been brought within fourteen or fifteen inches of the ground. To compensate for this the animal had a prehensile upper lip, which, however, was less pronounced than that of the moose. As in the moose, the withers are higher Fic. 217.—The American deer-moose Cervalces. Restoration from a skeleton in the Museum of Princeton University. After original by Charles R. Knight in the American Museum of Natural History. than therump. Cervalces was a contemporary of the moose, which survived into recent times. Sirenians, or sea-cows. —On both the Pacific and Atlantic coasts in Pliocene and Pleistocene times the most characteristic littoral mammals were the sirenians, or sea-cows, which were either derived from the migra- tion of Old World forms from Africa by way of the north Pacific and Asia, or were descendants of a transatlantic (Atlantis) migration (p. 340) in Eocene times which found ready access to the Pacific coast through one of the great sea routes which separated North and South America as late as the Pliocene period. In favor of the theory of north Pacific migration is the striking similarity which exists between the Japanese and Californian 1 On comparing the antlers of Cervalces with those of the moose, it becomes evident that the former consist of the same parts, with something added. Just what these additional parts are is by no means easy to say. The anterior tine (of the ear-shaped process) may be the bez- antler, while the posterior one may correspond to the tine which in Megaceros, the fallow-deer, and some others, is given off from the hinder surface of the beam nearly opposite the bez- antler. (Scott, 1885.) 494 THE AGE OF MAMMALS representatives of the remarkable Phocene mammal known as Desmostylus (see p. 344). Favoring the less probable theory of transatlantic migration from the African coast is the presence in supposed Eocene deposits of _ Jamaica of one of the most primitive of sirenians, the Prorastomus of Owen.! This animal, with its comparatively straight or normal upper jaw and com- plete series of teeth, is even more primitive in structure than the Hosiren libyca of the Upper Eocene Mokattam limestones (Fig. 89) of the Cairo and Fayidm districts of Africa. The great northern sea-cow of the Pacific (Rhytina stellert), or Steller’s sea-cow, was discovered by Steller, who accompanied Behring on his last expedition of 1741 in search of the northwest passage.? It inhabited the shallow waters immediately surrounding certain of the Aleutian Islands, and moved by means of two small anterior flippers, which were covered with bristles, and by its fluked tail. The short fore leg terminated abruptly without fingers or nails, but was overgrown with a number of short, thickly placed brush hairs. It was a bulky animal, thirty or even thirty-five feet in length, and twenty feet in girth, weighing about 6,700 pounds, and covered with a very thick, much wrinkled skin of a dark brown color. Of all the Sirenia it was the only one adapted by its thick undercoating of blubber to inhabit the cold seas of the north. In Pleistocene times it probably ranged much farther south than the Aleutian Islands. It probably became extinct toward the end of the eighteenth century because it fell an easy prey to the sailors and fur traders. ANTIQUITY OF Man In NortH AMERICA The time of the first appearance of man on the North American con- tinent still remains to be determined, and is a problem of the very highest importance. Was man contemporaneous with the closing period of the second or Megalonyx fauna, or with the third, the Ovibos and late Mastodon, fauna? Did man enter this country from Asia or from South America? Are traces of human occupation found first on the Pacific or on the Atlantic coast? All these are questions which remain yet to be answered positively. In brief, it may be said certainly, so far as anatomical evidence is con- cerned, that no trace of human skeletons of the Paleolithic or Neandertal type of Europe have been found in North America, and as certainly that all skeletons which have been reported have been referred finally to the recent Indian type. Second, there is some evidence of the coexistence of man with the late stages of the Megalonyx Zone in California and in the 1 Owen, R., On Prorastomus sirenoides. Quart. Jour. Geol. Soc. London, Vol. XXXI, 1875, p. 559, Pl. 18 and 19. 2 Nordenskidéld, A. E., The Voyage of the Vega round Asia and Europe, with a Historical Review of Previous Journeys along the North Coast of the Old World. Translated by Alex- ander Leslie. New York, 1882. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 495 central states, as well as considerable evidence of the appearance of man before the disappearance of the mastodon in the eastern states. This raises the further question as to the period of the final extinction of the mastodon. It will be interesting to pass in review some of the alleged or actual cases of the association of implements of human manufacture with the remains of various extinct mammals. Man and the mastodon. — As early as 1839 flint arrowheads were reported by Koch in association with the bones of M. americanus in Missouri. Again, evidence for the contemporaneity of man and the mastodon was reported in the Pleistocene near Charleston by Holmes in 1859 and in the Pleistocene of California by Whitney (1866-1867). In 1869, however, Leidy declared ! that neither of these alleged associations established beyond doubt the coex- istence of man with any of the extinct Pleistocene mammals. In 1885, however, Putnam reported the remains of man and mastodon in Worcester, Massachusetts,’ as follows: a mastodon tooth and a human skull were found associated together in a marsh eighteen feet below the surface; the lower jaw was embedded in blue clay; both showed that they had been transported by running water, and brought to this deposit before the overlying peat formation began. Norris, of the Bureau of American Ethnology, reported some fragments of elephant or mastodon tusks exhumed from a mound in Wisconsin. In 1887 Scott summed up the evidence as follows:* “It is well known to archeologists that pipes of catlinite shaped like the elephant have been discovered in Iowa, also that a so-called ‘elephant mound’ in Wisconsin has been much debated, since it is situated in the region of the effigy mounds of the northwest. . . . The coexistence of man and the mas- todon, or mammoth, in America, as in Europe, has advanced now beyond the stage of presumption; it has been so well verified that it can hardly be excluded from the realm of science.” Still, it is necessary to exercise care in the use of facts brought to light which seem to bear on this question. In 1887 D. G. Brinton * reported human footprints in the volcanic tufa at Lake Managua, about ten feet above which were mastodon remains. A striking feature of these footprints is that the second toe is the longest of all. In 1895 Mercer’ reported at Petit Anse, Louisiana, the discovery of modern implements, fourteen feet below the surface, underlying remains of an extinct elephant. This author considers that this may be a case of 1 Leidy, J., The Extinct Mammalian Fauna of Dakota and Nebraska, Including an Ac- count of Some Allied Forms from Other Localities, together with a Synopsis of the Mammalian Remains of North America. Jour. Acad. Nat. Sci. Phila., (2) Vol. VII, 1869, pp. 1-472. ? Putnam, F. W., Man and the Mastodon. Science, Vol. VI, no. 143, 1885, pp. 375-376. 3 Scott, W. B., On American Elephant Myths. Scribner's Magazine, Vol. I, April, 1887, p. 469. 4 Brinton, D. G., On an Ancient Human Footprint from Nicaragua. Proc. Amer. Phil. Soc. Phila., Vol. XXIV, 1887, pp. 437-444. 5 Mercer, H. C., The Antiquity of Man at Petit Anse (Avery’s Island), Louisiana. Amer. Natural., Vol. X XIX, no. 340, April, 1895, pp. 393-394. 496 THE AGE OF MAMMALS ‘intrusive burial,’ in which a grave was dug down through the earth to the salt. Another case of obviously artificial or accidental association is that reported in a sulphur spring at Afton, Indian Territory, by Holmes* (1901), where flint arrowheads and other implements were found in association with teeth and other remains of mammoth (probably EL. primigenius, EF. imperator), fossil bison, and the horse. The most plausible explanation of this accumulation is that the spring was regarded as magical by the Indians, who threw into it not only such fossil bones as were exposed in the vicinity, but also their most precious possessions, including their various weapons and implements. By far the most authentic case is that reported by Clarke? in 1903. A small tusk, ribs and other bones of a young mastodon were found at Attica, Wyoming County, New York, in unlaminated clay overlaid by muck, etc., at a depth of two to three feet. Several pieces of charcoal were dis- covered under these bones, and in another part of the same swamp and one foot below the level of the bones, some bits of broken pottery and a considerable quantity of charcoal were discovered. Man and Megalonyx. — At Natchez, Mississippi, a human pubic bone was found in 1846 in association with a true Megalonyx fauna. The bones were reported to be in the same condition of preservation as the larger bones, and hence may be considered contemporary.’ Leidy considered that this pelvic bone might have fallen in from one of the Indian graves above it. Wilson,* however (1892), reported that a chemical investigation of the human bone showed it was more advanced in fossilization than that of the asso- ciated Mylodon, and hence might be considered as old or older. Cope (1895) ° rejected the previous evidence, stating that no trace of man had been found in the Megalonyx fauna. In 1896, however, Mercer ® expressed the opinion that the remains of Megalonyx found in the Big Bone Cave, Van Buren County, Tennessee (Fig. 194, 10), were not appreciably older than the associated human remains. This is by far the most significant of these associations, and is more fully described below (p. 498). The most recently discovered associations of Megalonyx with supposed artifacts of human manufacture are in the Potter Creek and Samwel caves, ' Holmes, W. H., Flint Implements and Fossil Remains from a Sulphur Spring at Afton, Indian Territory. Ann. Rept. U.S. Nat. Mus., 1901, pp. 233-252. 2 Clarke, J. M., Mastodons of New York. A List of Discoveries of their Remains, 1705- 1902. N.Y. State Mus. Bull., 69, Paleontology, 9, 1903, p. 932. 3 Leidy, 1869. 4 Wilson, T., Man and the Mylodon. Their Possible Contemporaneous Existence in the Mississippi Valley. Amer. Natural., Vol. XXVI, no. 307, July, 1892, pp. 628-631. ° Cope, E. D., The Antiquity of Man in North America. Amer. Natural., Vol. XXIX, 1895, pp. 593-599. ® Mercer, H. C., Cave Exploration by the University of Pennsylvania in Tennessee. Amer. Natural., Vol. XXX, no. 355, July, 1896, pp. 608-611; also, Cave Exploration in the Eastern United States, Preliminary Report. Dept. Amer. Prehist. Archeol. Univ. Pa., 1896. PLEISTOCENE OF EUROPE, NORTH AFRICA4 AND NORTH AMERICA 497 the fauna of which is described above (p. 476). The weight of this evidence may be estimated from the opinions of Putnam (1905) and of J.C. Merriam (1906) cited below. Human implements and extinct mammals. — None of the early reports of association afford unequivocal evidence: the arrowheads found by Koch in 1839 in association with the bones of mastodon, those reported by Mer- cer, those in the sulphur spring at Afton (Indian Territory), all appear to be cases of accidental association. The flints and obsidian artifacts found in Fossil Lake, Oregon, with the mammals of the Equus fauna are also apparently an entirely superficial association. The most important case of association of an arrowhead with an extinct species of bison is that reported by Williston. As above described (p. 464), underneath the scapula of an extinct species of bison (B. occidentalis) an arrowhead was found imbedded in the matrix, but touching the bone itself. |The arrowhead must have been within the body of the animal at the time of death or lying on the surface beneath its body. At no great distance from this point bones of the elephant (/. colwmbi) have been found in the same material, namely, in the widespread upland marl which covered Fic. 218.— Flint arrow-head these skeletons discovered under skeleton of Bison : : antiquus in the Pleistocene of Russell ? describes the discovery of a spear- Kansas. After Williston. head in the ‘upper lacustral clays’ of the Lahontan basin as follows: ‘“‘The fossil from the Lahontan Basin, which will probably be considered by both geologists and archeologists as of the greatest interest, is a spearhead of human workmanship. This was obtained by Mr. McGee,* from the upper lacustral clays exposed in the walls of Walker River Cafion, and was associated in such a manner with the bones of elephant or mastodon, as to leave no doubt as to their having been buried approximately at the same time. Both are genuine fossils of the pre-Lahontan period. The spearhead is of chipped obsidian, and is in all fespects similar to many other implements, commonly found on the surface, throughout the far West.” The most recent of these associations is the alleged evidence of man’s G yj TF I } == ey nev, i A SS ee 1 Williston, S. W., An Arrow-head found with Bones of Bison occidentalis Lucas, in western Kansas. Amer. Geol., Vol. XXX, Nov., 1902, pp. 313-315. 2 Russell, I. C., Geological History of Lake Lahontan. A Quaternary Lake of North- western Nevada. Monogr. U.S. Geol. Surv., Vol. XI, 1885. 3W J McGee, the well-known geologist and ethnologist. 2K 498 THE ‘AGE OF MAMMALS handiwork in the Shasta Caves (Potter Creek and Samwel) of California, which contain a pure though late Pleistocene fauna. Examination by Putnam! led him to the conclusion that the evidence of man’s handi- work, consisting chiefly of two perforated bones, is sufficiently important to warrant belief that man lived in the vicinity of these caves. Merriam,’ however (1906), adopted the somewhat more conservative conclusion that the “splintered, polished, perforated fragments of bone, etc., found in the Potter Creek and Samwel caves look like human artifacts, but cannot be pronounced such with certainty at present.”’ Human remains in cave deposits. —It is noteworthy that while the European cave deposits are of late Pleistocene age, frequently containing remains of man, American caves are chiefly of mid-Pleistocene age, and not until we reach, the Potter Creek (p. 475) and Samwel caves (p. 477) in California do we find any evidence, and that not conclusive, of the existence of man. In the East this has been made a subject of special invesfigation by Mercer.* His journey of six hundred miles was especially directed to those mountain passes and river ways by which early man may have first pene- trated the great forests of the Appalachians in traveling from the Pacific coast and plains region of the West. In every case investigated along the Tennessee, Ohio, and Kanawha rivers in Ohio, West Virginia, Indiana, and Kentucky, remains of man were found associated only with the recent fauna such as the deer, gray fox, raccoon, opossum, black bear, turkey, etc. The only exception was the Big Bone Cave, Van Buren County, Ten- nessee, where nine hundred feet from the entrance were found remains of the fossil sloth, megalonyx, fresh in appearance, with remains of the cartilages attached, associated with fragments of reeds which had apparently been used as torches by Indians, thus presenting evidence of the contemporaneity of the modern Indian with the extinct megalonyx. This evidence con- vinced Mercer that at least in the eastern valley of Tennessee at a height of six to seven hundred feet above sea level man coexisted with the great sloth. Again, in Zirkel’s Cave, Jefferson County, Tennessee, two faunal levels were discovered, the lower containing the tapir, peccary, and bear, the upper containing the marmot, or woodchuck (Marmota), opossum (Didelphys), rabbit, and cave rat associated with Indian remains. This appears to be the first instance thus far discovered in eastern North America of the occupation of caves by man, and of a modern fauna overlying an ancient fauna. The second instance is that of Look Out Cave on the left ' Putnam, F. W., Evidence of the Work of Man on Objects from the Quaternary Caves in California. Amer. Anthropol., n.s., Vol. VIII, 1905, pp. 229-235. * Merriam, J. C., Recent Cave Exploration in California. Amer. Anthropol., n.s., Vol. VIII, no. 2, Apr.—June, 1906, pp. 221-228. ’ Mercer, H. C., Cave Exploration in the Eastern United States. Dept. Amer. Prehist. Archeol., Univ. Penn., July 4, 1894; Cave Exploration in the Eastern United States. Dept. Amer. Prehist. Archeol., Univ. Penn., June 4, 1896. | 7 ———* PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 499 bank of the Tennessee River, containing bones of the tapir and mylodon in in the lower zone, and Indian remains in an upper zone of black earth. Skeletal Remains Attributed to Early Man We owe to Hrdlicka! a thorough comparative study of all the skeletal remains which have been discovered in North America and attributed to early man. He observes that proof of the geological antiquity of human remains demands indisputable stratigraphic evidence, some degree of fossil- ization, and marked anatomical distinctions in the more important parts of the skeleton. A skeleton which agrees with that of a recent or not very ancient race in the same locality cannot be accepted as geologically ancient unless the geological evidence be absolutely decisive. Since 1844 fourteen discoveries have been made with more or less serious claim of considerable geological antiquity. Of these the chief are the Natchez (Mississippi) pelvic bone (1846), the Calaveras (California) skull (1866), the Trenton (New Jersey) skulls (1879, 1887), the Lansing (Kansas) skeleton (1902), and the Nebraska ‘loess man’ (1894, 1906). In some instances association of the human bones with those of extinct animals is due to ‘intrusive burials,’ 7.e. burials in which the grave hap- pened to be carried below the level of a stratum contaiming a number of extinct forms. The Natchez pelvic bone may be a case of accidental association of a bone fallen from an Indian grave and mingled with older fossilized bones. The famous Calaveras skull agrees closely with the cave skulls from Calaveras County geologically of recent age. The Trenton crania found in glacial gravels along the Delaware River are of doubtful geological age, while their anatomical characters are not those of the Dela- ware Lenape Indians recently inhabiting the district, but appear of relatively modern and European origin. The Lansing skeleton found twenty feet below the surface in the loess-like silt was heralded as a find of real geologic antiquity, but proves to agree closely with the typical upper Mississippi valley Indian of the present day. Similarly, the fossil human bones from the west coast of Florida show a marked anatomical likeness to recent Indian bones. The Nebraska loess man, which was regarded by the present writer (Osborn) and others as exceptionally primitive, proves to correspond in its low forehead with certain low-type Indian crania, such as are found among the mound-builders of Arkansas and even among certain recent Indians. “Under the circumstances,” concludes Hrdliéka, it must be stated that “thus far on this continent no human bones of undisputed geologic antiquity are known,” and anatomically the remains indicate their affinity or identity with those of modern Indians. This does not mean that early man did not 1 Hrdlicka, A., Skeletal Remains Suggesting or Attributed to Early Man in North America. Smiths. Inst., Bur. Ethnol., Bull. 33, 1907. 500 THE AGE OF MAMMALS exist in North America, but that convincing proof of the fact from the standpoint of physical anthropology still remains to be produced. Auriferous gravels. — The most recent review of this question is that of Sinelair,! in which the following conclusion has been reached: “A review of the evidence favoring the presence of the remains of man in the auriferous gravels of California compels one to regard it as insufficient to establish the fact. It has been shown either that there have been abundant opportunities for the relics in question to be mixed with the gravels accidentally, or that the geological conditions at the localities are such as to render it improbable that the implements and bones have been associated in the gravels to the extent supposed.” Mercer? reached a negative conclusion in his survey of the Trenton gravels: ‘‘Nor has anything yet been found anywhere else in the valley to corroborate the alleged antiquity of the chipped blades from Trenton.” The Trenton case has been somewhat weakened by the appearance among the drift specimens of several blades of common Indian pattern. CAUSES OF PLEISTOCENE EXTINCTION ? Certainly the most direct instance of widespread extinction of quadrupeds contemporaneous with a secular change of climate was that of the Glacial Period in the entire northern hemisphere. As we have seen, the beginning of the Pleistocene found North America peopled with the following kinds of great quadrupeds, all of which disap- peared during or shortly after the Ice Age: ARTIODACTYLA Camelidee Camels Llamas PERISSODACTYLA Equidee Horses Tapiridee Tapirs PROBOSCIDEA Mastodontinee Mastodons Elephantinze Elephants EDENTATA Gravigrada Giant Sloths Megalonyx Megatherium Paramylodon Glyptodontia Glyptotherium It would be natural to assume that extinction was directly brought about by the profound changes of temperature and moisture, accompanied by 1 Sinclair, Wm. J., Recent Investigations bearing on the Question of the Occurrence of Neocene Man in the Auriferous Gravels of the Sierra Nevada. Univ. Cal. Publ., Amer. Archeol. Ethnol., Vol. VII, no. 2, 1908, pp. 107-131. 2 Mercer, H. C., The Antiquity of Man in the Delaware Valley. Repr. fr. Publ. Univ. Pa., Vol. VI, 1897, pp. 1-85. 3 Osborn, H. F., The Causes of Extinction of Mammalia. Amer. Natural., Vol. XL, no. 479, Nov., 1906, pp. 769-795, no. 480, Dec., 1906, pp. 829-859. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 501 changes in the fauna and flora consequent upon the great geologic and physiographic changes of Glacial times; but this simple explanation is beset with many difficulties and contradictions, and the results must be analyzed with some care. The extinction of the horse in North America, for example, does not admit of such a simple explanation. While in Europe the Mediterranean Sea presented a barrier to escape or migration to the south, in North America there were broad continental Fic. 219.— Holocene or Recent times. A period of continental depression. Asia and North America completely separated, preventing further intermigrations of mammals. The island systems of the New and Old Worlds and of Australia mostly separated. Africa united with Europe by a narrow desert strip, a barrier to further migration. areas and high plateaux affording easy migration routes southward, and every means of escape. It is, therefore, more in accord with the facts to say that the Glacial Period in North America originated certain new conditions of life which directly or indirectly resulted in extinction. These conditions include diminished herds, enforced migrations, the pos- sible overcrowding of certain southerly areas, changed conditions of feeding, disturbances in the period of mating and reproduction, new relations with various enemies, aridity, and deforestation; in short, a host of indirect causes. Protective adaptation to secular cold. — The resistance of mammals to cold depends upon (a) the internal heat-producing power, which is a progressive adaptation of the higher Mammalia, correlated with (b) the accession of a warm external covering in the form of hair, wool, or blubber 502 THE AGE OF MAMMALS as in the case of aquatic mammals. The well-known cases of adaptation to extreme cold among elephants (Z. primigenius, woolly mammoth), rhi- noceroses (R. antiquitatis, woolly rhinoceros), steppe camels of Asia (Ca- melus bactrianus), steppe horses (Equus przewalskiz), and steppe antelopes (Saiga tartarica) indicate that we must not assume that cold was in all cases the direct cause of extinction. Cold and the numerical diminution of herds. — As suggested by Darwin, a temporary diminution in numbers, whether caused by cold waves, long or repeated droughts, floods, epidemics, or other unfavorable conditions of life, may indirectly lead to extinction. The protection of a herd of animals from hostile Carnivora often depends on its numbers. It has been observed recently that the woodland bison (B. athabasce) of British Columbia is in danger of extinction because the bulls are not sufficiently numerous to pro- tect the young. Numerical diminution may in this way become a cause of extinction. The observations of Prichard ' in Patagonia give an interesting instance of the influence of severe winters on the very hardy guanacos and deer of that region. “Around the lake lay piled the skulls and bones of dead game, guanaco (Lama huanachus) and a few huemules (Furcifer chilensis). These animals come down to live on the lower ground and near unfrozen water during the cold season, and there, when the weather is particularly severe, they die in crowds. We saw their skeletons in one or two places literally heaped one upon the other”’ (op. cit., p. 132). “Again we came upon a second death-place of guanaco, which made a scene strange and striking enough. There cannot have been less than five hundred lying there in positions foreed and ungainly as the most ill-taken snapshot photograph could produce. Their long necks were outstretched, the rime of the weather upon their decaying hides, and their bone-joints glistening through the wounds made by the beaks of carrion-birds. They had died during the severities of the previous winter, and lay literally piled one upon another” (op. cit., p. 189). ‘‘The meaning of this I gathered from Mr. Ernest Cattle. He told me that in the winter of 1899 enor- mous numbers of guanaco sought Lake Argentino, and died of starvation upon its shores. In the severities of winter they seek drinking-places, where there are large masses of water likely to be unfrozen. The few last winters in Patagonia have been so severe as to work great havoc among the herds of guanaco”’ (op. cit., p25). Diminished herds and inbreeding. — Another danger attending dimin- ished herds in restricted regions is close inbreeding. On this familiar subject see Gerrit 8. Miller’s? paper ‘Fate of the European Bison Herd,” in which the author shows the possibly fatal influence of inbreeding on diminished herds, although it must be pointed out that these bison are protected and are thus living under unnatural conditions. 1 Prichard, H. H., Through the Heart of Patagonia. New York, 1902. 2 Miller, G.S., Jr. The Fate of the European Bison Herd. Science, n.s., Vol. IV, no. 99. Nov. 20, 1896, pp. 744-745. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 503 In a paper entitled “Das allmihliche Aussterben des Wisents (Bison bonasus, Linn.) im Forste von Bjelowjesha,” ' Mr. Eugen Biichner gives a detailed history of the bison herd in the Bieloviejsha (or Bialowitza) forest, Province of Grodno, in Lithuania, Russia, during the present century. “A careful study of the breeding habits of the bison in the Bieloviejsha forest and elsewhere leaves no room for doubt that the present slow rate of reproduction is an abnormal condition, and that to it is due the rapid approach of the extinction which is the certain fate of the herd under con- sideration. This diminished fertility the author regards as a stigma of degeneration caused by inbreeding. . . . Another indication of the degen- erate condition of the Bieloviejsha herd is seen in the great excess of bulls, which probably outnumber the cows two to one. This is doubtless a result of inbreeding, for Diising? has shown that close inbreeding, like a reduced condition of nutrition, is favorable to the production of an excess of males. . .. In conclusion, the author considers that his studies of the history of the Bieloviejsha bison leave scarcely room for doubt that inbreeding is the cause of the final extinction of most large mammals. Inbreeding must begin and lead gradually but certainly to the extinction of a species when it, through any cause, has become so reduced in numbers as to be separated into isolated colonies.”’ Influence of cold during the reproduction period. — Exceptional cold waves or unusually prolonged cold seasons may cause a temporary loss of food supply or cause the death of the young, which in northern latitudes are usually born in spring. The diminution or loss of young from this cause might act as the first of a series of destructive effects of a progressive secular change. These may be summarized as follows from the actual observa- tions * of zodlogists upon the Cervidze: (a) disturbed conditions during the conjugation (pairing, mating, rutting) period; (b) enfeebled (through hunger) condition of females during parturition period; (c) severe weather conditions, ice storms, crusted snow, prolonged wet and sleet at time of birth; (d) bulls unable to protect herds; (e) cows unable to protect young from Carnivora through starved condition, or abandoning them when attacked by wolves; (f) enfeebled and unprotected condition of quad- rupeds favorable to increased food supply and consequent multiplication of cursorial and other Carnivora, especially Canidz and Felide. These zoélogical observations are to a certain extent borne out in pale- ontology by Leith Adams’ (“‘ British Fossil Elephants,’’ 1879, Pt. 2, p. 98) observations of the exceptionally large number of milk teeth of elephants found in certain Pleistocene deposits, which appears to indicate a high mortality of the young. (See also Holland, p. 471.) 1 Biichner, Eugen, Mém. Acad. Impér. Sci. St. Pétersbourg, Vol. III, no. 2, 1895, pp. 1-30. 2 Dising, Jen. Zeitschr. Naturwiss., Vol. XVII, 1884, p. 827. * Communicated by Mr. Madison Grant, Secretary of the Zodlogical Society of New York. 504 THE AGE OF MAMMALS Temperature control of fertility and reproduction. — Merriam * has directed attention to one of the physiological effects of a lowering of temperature, namely, its influence upon diminished or increased fertility and the rate of reproduction in what he has called the ‘law of temperature control.’ This he has stated as follows: temperature by controlling reproduction prede- termines the possibilities of distribution; it fixes the limits beyond which species cannot pass; it defines broad transcontinental barriers within which certain forms may thrive if other conditions permit, but outside of which they cannot exist, be the other conditions never so favorable (because the sexes are not fertile). Temperature and geographic range. —In discussing how species are checked in their efforts to overrun the earth Merriam points out that more important than geographic barriers are the climatic barriers (as observed by Humboldt), and of these that temperature is more important than humidity. First, in 1892, this author attempted to show 2 that the distribu- tion of terrestrial animals is governed less by the yearly isotherm or mean annual temperature than by the total rather than the mean temperature during the period of reproductive activity and of growth (adolescence). This reproductive period in the tropics extends over many months or nearly the whole year, and within the Arctic Circle and summits of high moun- tains is of two months or less duration. Later, in 1894, results which Mer- riam' obtained from extensive comparison of temperatures and distribu- tion justified the belief that animals and plants (Lower Austral and tropical types coming from the South) are restricted in northward distribution by the total quantity of heat during the season of development and reproduc- tion. Conversely animals and plants (Upper Austral, Transition, and Boreal types coming from the North) are restricted in southward distribu- tion by the mean temperature of a brief period covering the hottest part of the year. Thus in the Transition Zone, Boreal and Austral types mingle in the equable climate of the Pacific coast of California, while they are sharply separated by the inequable extremes of cold and heat of the interior continental plateau. It follows from these observations that animals forced out of their natural habitat may become extinct through infertility. Influence of cold and snow on food supply and choice of food. — It is prob- able that during the Glacial Period the great winter snow blanket cover- ing the natural food supply, rather than the direct influence of the cold itself, was one of the chief causes of extinction. The death of great numbers of animals from hunger or starvation through the covering of food during the winter season under heavy layers of snow is commonly observed among ' Merriam, C. H., Laws of Temperature Control of the Geographic Distribution of Terres- trial Animals and Plants. Nat. Geogr. Mag., Vol. VI, Dec. 29, 1894. 2 Merriam, C. H., The Geographic Distribution of Life in North America with Special Reference to the Mammalia. Proc. Biol. Soc. Washington, Vol. VII, Apr. 13, 1892, pp. 45-46. Ce = ee ee PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 505 Fic. 220.— Pliocene and Pleistocene extinction. Former (ruled lines) and recent (solid black) distribution of: A. Rhinocerotide, rhinoceroses. B. Proboscidea, elephants and mastodons. C. Equids, horses, asses, and zebras. 506 THE AGE OF MAMMALS the large herds of the domesticated horses and cattle on the western plains. Under these conditions horses are driven to food, such as the branches of willows, which is very deleterious to them. Under the influence of hunger cattle will also feed eagerly and indiscriminately on plants which may be injurious to them or to their young, as recorded by Chestnut and others in the United States Agricultural Department. After heavy snowstorms, when the grass is covered with snow, it often happens that only the taller species of plants are exposed.’ In such cases the poisonous larkspurs (Delphinium glaucum) are greedily eaten by cattle which would otherwise avoid these plants. This tendency is increased by the fact that ruminants do not feel at ease so long as the stomach is not full, and are inclined to eat anything in sight after a snowfall. Similarly, enforced migrations among wild as among domesticated animals might cause them to become less fastidious about their food. It is observed ' among domesticated animals that when feeding quietly on the range they exercise considerable choice in the selection of forage plants, but when driven six or eight miles daily they are frequently forced by hunger to bite off almost all kinds of plants which grow along their course. Animals vary greatly in adaptability to new conditions caused by long cold and heavy snowfall; horses remove snow even to a depth of three or four feet, and find food sufficient to carry them through the winter, while cattle under the same conditions starve. Forestation, deforestation, and reforestation. — It is certain that the Hol- arctic region, or circumpolar belt, was forested even to the shores of the Arctic Ocean in early Pleistocene times. The remains of large extinct quadrupeds in this region are almost everywhere associated with evidences of forests, and of forest-frequenting animals, such as the beaver. The forests naturally furnished the necessary conditions of life of certain quadrupeds, especially of browsing animals, and even of Proboscidea. Among Artiodactyla the deer, among Perissodactyla the tapirs, are typical forest animals. Condi- tions, therefore, which would cause deforestation would also become the means of diminution, and finally of extinction. Such conditions are intense cold, (a) heavy snow-capping of the tundra regions of the north, (6) the dry cold and dust storms of the steppes. In Europe a period of deforesta- tion and a long unforested period of dry cold certainly succeeded each other. In North America we have evidence of similar conditions in our own loess period, and there certainly occurred a great deforestation in the regions now known as the ‘barren grounds,’ which pass into the tundras with frozen subsoil to the north. After considering the diminution of life in Alaska, Maddren? summarizes * Chestnut, V. K., The Stock Poisoning Plants of Montana. U.S. Dept. Agric., Div. Botany., Bull. 26, Washington, 1901. * Maddren, A. G., Smithsonian Exploration in Alaska in 1904, in Search of Mammoth and other Fossil Remains. Smiths. Misc. Coll., Vol. XLIX, 1905, p. 65. PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 507 his conclusions as follows: that the most rational way of explaining the extinction in Alaska is the gradual change from more temperate conditions which reduced and finally destroyed the forest vegetation, thus reducing the food supply and reducing the fauna to those forms capable of adapting themselves to the recent tundra vegetation. Extermination of horses. — Among all the problems of Pleistocene extinc- tion presented in America, that of the horses is certainly one of the most difficult. These animals are far superior to cattle in their adaptability to changed conditions of life and in resourcefulness during severe winter sea- sons. They were extraordinarily numerous in North America at the begin- ning of the Pleistocene; at the close it appears that they were entirely extinct. Similar extinction occurred both in North and South America in Pleistocene times. It is consequently impossible to connect this phenom- enon directly with the Ice Age. In Pleistocene times there was a ready escape to the high plateaux of Mexico, which must have presented all the most favorable conditions for equine life, of climate, soil, and food. The nu- merous and highly specialized horses of Mexico shared in this extinction. It has consequently been suggested by the writer and by others that the horses may have been swept out of existence by some epidemic disease or diseases. These diseases are carried by flies and are favored by moist conditions occurring chiefly during or immediately after heavy rainfalls, though in sporadic cases they may occur at other seasons of the year; such moist conditions occurred periodically in the Great Basin of Oregon and Nevada and in the valley of Mexico. The disease known in India as ‘surra’ has a widespread geographic distribution. In Africa there is a similar malady, ‘nagana,’ or tse-tse fly disease. In Algeria, France, and Spain the horse and the ass are both liable to the attacks of a trypanosome (7’. equiperdum). In South America the mal de caderas affects horses, asses, cattle, and certain other animals, and is attributed to a trypanosome; it is distinctively a wet weather disease, almost completely disappearing in the dry seasons. The tse-tse fly of Africa renders thousands of square miles uninhabitable by horses. The rapid rate at which such diseases may travel is illustrated by the spread of the rinderpest, which traversed the whole length of Africa in fifteen years. This theory of an epidemic among the American horses during the wet weather periods of Glacial times receives some support from the discovery by Cockerell in the Miocene insect fauna of Florissant, Colorado, of two species of tse-tse fly (Glossina) very similar to the African types. The application to the Pleistocene is that a moist or rainy period extending over the Southern States and down into Mexico during Pleistocene times would have favored the distribution of some flies or other parasite-bearing insects, such as ticks, and have resulted in the extinction of the horses. Influence of increased rain supply. — Dry or moderately dry conditions, if not too extreme, are generally more favorable to quadrupeds than moist 508 THE AGE OF MAMMALS conditions. The plains and forest regions most densely populated with quadruped life, such as those of the African plateaux of the present day, are regions of moderate rainfall and even of prolonged summer droughts. The regions less densely populated with quadrupeds are those of heavy rainfall, of dense forests and vegetation, such as those of the equatorial belt of South America or the Mango region of Africa. Moisture and temperature are, therefore, to be first considered in relation to forestation. Increased rainfall has many other effects: (1) it may diminish the sup- ply of harder grasses to which certain quadrupeds have become thoroughly adapted; (2) it may at the same time produce new poisonous or deleterious plants; (3) it may be the means of introducing new insects or other pests, and new insect barriers; (4) it may be the means of introducing new proto- zoan diseases and new insect carriers of disease; (5) it may be the means of erecting new forest barriers to migration, or new forest migration tracts for certain Carnivora, such as the bears. It follows that periods of secular increasing moisture, such as the early and mid-Pleistocene of the northern hemisphere is supposed to have been, may have been unfavorable to certain large quadrupeds which had become adapted to Pliocene conditions of semi-aridity, even prior to the advent of extreme cold. As regards migration, Merriam observes that humidity is a less potent factor than temperature in limiting the distribution of the Mam- malia of North America. Thus many genera adapted to certain restrictions of temperature ranged east and west completely across the American con- tinent, inhabiting alike humid and arid subdivisions, but no genus adapted to certain conditions of humidity is able to range north and south across the temperature zones. Food supply and moisture. —Sheep and cattle owners of the North- west have observed that the majority of poisonous plants are those which flourish during moist seasons, such as the death camas (Zygadenus), the larkspurs (Delphinium), the water hemlocks (Cicuta), the white loco (Aragallus). It is a matter of universal observation that in tick- or insect-infested countries dry seasons result in the reduction, moist seasons in the increase of diseases: dry localities are favorable; moist localities are unfavorable. Thus the tse-tse fly is not found in the open veldt; it must have cover. Warm, moist, steamy hollows containing water, inclosed with forest growth, are the haunts chosen. Ticks, even when non-infection-bearing, form absolutely effective bar- riers to the introduction of quadrupeds into certain regions. In certain forested portions of South and Central America they endanger human life. In certain regions of Africa ticks are practically fatal to horses. As observed by Elliot, thousands of ticks would sometimes gather on a horse as the result of a single night’s grazing. The mane especially serves to collect PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 9509 these pests; thus the falling mane of the northern horse is distinctly dis- advantageous as compared with the upright mane of the asses and zebras. Ticks abound in the southern plains region of the United States, as well as in the forests bordering the Mexican plateau, and are thus both plains and forest pests. They are certainly to be considered in connection with the extermination of horses. Tie laine OUTLINE CLASSIFICATION MAMMALIA RECENT AND EXTINCT INCLUDING ESPECIALLY THE BETTER KNOWN GENERA AND FAMILIES AND THOSE MENTIONED IN THIS BOOK This classification has been prepared under the direction of the author by W. K. Gregory and Johanna Kroeber Mosenthal. The geological range and revision of the extinct genera has been done with the codperation of W. D. Matthew. The scheme of classification under four grand divisions, and the order throughout, from the more ancient and primitive to the more specialized forms, is that of the author. 511 APPENDIX LIST OF ABBREVIATIONS AND SYMBOLS A ARAN wesc ie extinct. Miriass. 2. Lasnic: Nom. nov... . new (group) name. Jilteesiene 1 ULASSIC: Ine. Sed... . . (Jncerte Sedis), of uncertain Cret.... . Cretaceous. systematic position. Eoc. .. . . Eocene. Ami wean ok. family. Olig.. . . . Oligocene. Bass" eeeiaasccn Basal. Mioc. ... Miocene. Wise reece re betes Lower. Plioc. .. . Pliocene. Miao oikemens cen Middle. Pleist. . . . Pleistocene. | OMe eR SA dF ete Upper. ec. sta: Recent. In cases where the generally accepted name is preoccupied it is placed within quotation marks, and the technically correct name is placed after it in brackets, e.g. ‘ Echidna’ (= Tachyglossus). Following is a list of the general works consulted in drawing up the classification. below. AMEGHINO, F.. BEDDARD, F. E. . COPE EADS cami DrPuRnT O20 6. Ex.iot, D. G. . Works dealing with particular groups are cited Contribucion al Conocimiento de los Mamyferos Fosiles de la Republica Argentina. Buenos Aires. 1889. Mammalia. The Cambridge Natural History, Vol. X. Lon- don. 1902. The Vertebrata of the Tertiary Formations of the West. Rept. U.S. Geol. Surv. (Hayden). Washington. 1884. L’évolution des Mammiféres tertiaires ; importance des migra- tions. C.R. Acad. Sci. Paris, Vol. cxli, séa. Nov. 6, 1905; Vol. exlii, séa. March 12, 1906; Vol. exliii, séa. Dec. 24, 1906. Transl. by Johanna Kroeber, Amer. Natural., Vol. xlii, Nos. 494, 495, 497, Feb., March, and May, 1908, pp. 109-114, pp- 166-170, pp. 303-307. [Latest and most authoritative review of Tertiary faunas of Europe. | A Catalogue of the Collection of Mammals in the Field Colum- bian Museum. Field Columbian Museum Publ., No. 115. Chicago, 1907. The Land and Sea Mammals of Middle America and the West Indies. Field Columbian Mus. Publ., 95. Chicago, 1904. [Very numerous illustrations, including drawings of the animals, and photographs of the skulls. ] 53 514 ; & THE AGE OF MAMMALS Frower, W. H., and An Introduction to the study of Mammals Living and Extinct. LYDEKKER, R. Greaory, W. K.. EVAy:. (O-0b Se. Hornapay, W. T. KINGSLEY, J. S. LYDEKKER, R.. Ossorn, H. F. PALMER, T. S. ScLaTER, W. L., and ScLATER, P. L. SCLATER, W. L. . TROUESSART, E. L. . WEBER, M.. ZITTEL, K. A. von . London, 1891. [Excellent generic descriptions of recent mammals. ] The Orders of Mammals. Bull. Amer. Mus. Nat. Hist., Vol. XXVIII, 1910, pp. 1-524. [Part I treats history of the ordinal classification of mammals; Part II discusses the evolution and relationship of the orders. ] Bibliography and Catalogue of the Fossil Vertebrata of North America. Bull. U.S. Geol. Surv., No. 179. Washington, 1902. [A remarkably complete key to the literature of extinct mammals of America. ] The American Natural History. New York. 1904. [Useful descriptions and illustrations, especially of American rodents, carnivores, and ungulates. ] The Standard Natural History, Vol. V, Mammals. Boston. 1884. A Geographical History of Mammals. Cambridge. 1896. The New Natural History. Vols. I-III]. New York. Evolution of Mammalian Molar Teeth. New York. 1907. [Figures the teeth of many extinct and recent genera. ] Cenozoic Mammal Horizons of Western North America, with Faunal Lists of the Tertiary Mammalia of the West by W.D. Matthew. U.S. Geol. Surv., Bull. 361. Washington. 1908. [Numerous sections and maps. Faunal migrations and interchange with the Old World.] Index Generum Mammalium. Galeopithecus. _Colugo, Flying “Lemur.” Burma to Borneo, Philippines. V.. OrpveR CHIROPTERA. Bats.? 1. SusporpER ‘MEGACHIROPTERA’ (= Frugivora). Fruit-eating Bats. Fam. Pteropide. Fruit Bats. Supram. Pteropine. Common Fruit Bats. Epomophorus. Epauleted Fruit Bat. Afr. Pteropus. Flying Fox. S.E. As., E. Indies, Austral. Pteralopex. Cusped-toothed Fruit Bat. E. Indies. ‘ Cynonicteris’ (= Rousettus). Dog Bat. Afr., S. As., E. Indies, (M. Mioce., Eur.). ‘Harpyia*> (= Nyctymene). Tube-nosed Fruit Bat. E. Indies, Austral. Cynopterus. Short-nosed Fruit Bat. India, Indo-China, E. In- dies. Suspram. ‘ Macroglossine’ (= Kiodontine). Long-tongued Fruit Bats. * Macroglossus’ (= Kiodon). Long-tongued Fruit Bat. Indo- China, E. Indies, Austral. Susram. Harpyionycterine. Harpy Bats. Harpyionycteris. Harpy Bat. Philippine Islands. 2. SuBorDER ‘MICROCHIROPTERA’ (= Animalivora). Insect-eating Bats. 1 Vide Marsh, O. C., Principal Characters of the Tillodontia. Amer. Jour. Sci. (8), XI, 1876, pp- 249-252, Pl. VIII, IX. For reasons for regarding the tillodonts as an offshoot of the insectivore-creodont stock not related to the rodents, see Gregory, W. K., The Orders of Mam- mals. Bull. Amer. Mus. Nat. Hist., Vol. XXVII, 1910, pp. 292-294. 2 Vide Weber, Die Siugetiere, pp. 406-410. 3 Vide Weber. Die Saiugetiere, pp. 382-406; Elliot, D. G., The Land and Sea Mammals of Middle America and the West Indies, Pt. II, pp. 569-722; Miller, G.S., The Families and Genera of Bats. Smithsonian Institution, U.S. Nat. Mus., Bull. 57, 1907. The present arrangement by Gregory is adapted chiefly from Miller, and aims to give only the better known genera and subfamilies. on to nS THE AGE OF MAMMALS Fam. Emballonuride. Large-eared Bats. Susram. Rhinopomine. Long-tailed Bats. Rhinopoma. Long-tailed Bat. N. Afr., S. As. Supram. Emballonurine. Sheath-tailed Bat, Tomb Bat, ete. Emballonura. Sheath-tailed Bat. Madag., Indo-China, E. Indies, Polynesia. Taphozous. Tomb Bat. Afr., S. As., E. Indies, Austral. Saccopteryx. Pouch-winged Bat. S. Amer., C. Amer., Mexi. Suspram. Diclidurine. White Bats. Diclidurus. White Bat. C. Amer., S. Amer. Fam. Rhinolophidz. Noseleaf Bats. Susram. Megadermine. Hispid Bat, False Vampire, etc. Nycteris. WHispid Bat. Afr., E. Indies. Megaderma. False Vampire. Afr., India, E. Indies, Austral. Supram. Rhinolophine. Cyclops, Horseshoe Bat, etc. + Pseudorhinolophus. U. Eoc., Eur. Rhinolophus. Worseshoe Bat. Eur. (since M. Mioc.), As., E. In- dies, Austral., Afr. Supram. Hipposiderine. ‘Phyllorhina’ (= Hipposiderus). Leaf-nosed Bat, Cyclops Bat. Afr., S. As. (since Pleist.), E. Indies, Austral. Fam. Noctilionidez. Hare-lipped Bats. Noctilio. Hare-lipped Bat. S. Amer. Fam. Phyllostomida. Vampire Bats. Susram. ‘Lobostomine’ (= Chilonycterine). Cinnamon Bat Hare-lipped Bat, ete. ‘ Lobostoma’ (= Chilonycteris). Chin-leafed Bat. W. Indies, Mexi. to Brazil. Mormoéps. Cinnamon Bat. W. Indies, Mexi., C. Amer., S. Amer. Supram. Phyllostominz. American Leaf-nosed Bats. Otopterus. California Leaf-nosed Bat. W. Indies, Cal., Mexi. Lonchorhina. Tome’s Long-eared Bat. W. Indies. Vampyrus. Vampire. C. Amer. to Brazil (since Pleist.). Phyllostomus. Javelin Bat. S. Amer. (since Pleist.). Supram. Glossophagine. Long-tongued Vampire, ete. Glossophaga. Long-tongued Vampire. Mexi. to Brazil, Chili. Cheronycteris. Tres Marias Islands Bat. Mid. Am. a APPENDIX . 525 Susram. Phyllonycterine. Poey’s Bat, ete. Phyllonycteris. Poey’s Bat. W. Indies. Susram. Stenodermine. Centurion Bat, Short-nosed Vampire, ete. Brachyphylla. Cavern Nose-leaf Bat. W. Indies. Artibeus. Short-nosed Vampire. Florida, Mexi. C. Amer., S. Amer. Stenoderma. Cinereous Bat. W. Indies, Brazil. Centurio. Centurion Bat. Mexi., C. Amer., Cuba. Vampyrops. White-striped Bat. Mexi., C. Amer., S. Amer. (since Pleist.). Susram. Desmodontine. Blood Vampires. Desmodus. Common Blood-sucking Vampire. Mexi. to Para- guay (since Pleist.). Diphylla. Smaller Blood-sucking Vampire. Mexi. to Brazil. Fam. Natalidz. Funnel-eared Bats. Supram. Nataline. Tall-crowned Bat, ete. Natalus. Tall-crowned Bat. N. Amer. Nyctiellus. Graceful Bat. Cuba. Suspram. Furipterine. Fury. ‘ Furia’ (= Furipterus). Fury. §S. Amer. Susram. Thyropterine. American Sucker-footed Bats. Thyroptera. Tricolor Bat. Tropical Amer. Supram. Myzopodide. Madagascan Sucker-footed Bats. Myzopoda. Golden Bat. Madag. Fam. Vespertilionidz. Simple-faced Bats. Supram. Vespertilionine. Common Bats. t Vespertiliavus. U. Eoc., Eur. t Palwonycteris. V.. Olig., Eur. Vespertilio. Brown Bat, ete. Asia, Eur. (since M. Mioe.); N. and S. Amer. (since Pleist.) ; Afr., Austral. ‘Vesperugo’ (= Pipistrellus). Pipistrelle, Noctule, ete. OOD. Mesonychide, Torrejon, 111; Ypresian (?), 117; Wasatch, 126, 127; Wind River, 132, 133; typical genus, restored, 150; Washakie, 167; Uinta, 168; extinction, WOK 627 Mesonyzx, of third faunal phase, 139; Bridger, 161, 164; Uinta, 170; 527.* Mesopithecus, 272, 545.* Mesoreodon, 233, 550.* Mesozoic mammals, location of deposits of (map), 82. Metacheiromys, Bridger, 162, 163; outline restoration, 162; skeleton figured, 164; 541.* Metamynodon, 219, 221, 223; restoration, 180; zone, 182; sandstones (photographs), 217, 219; skeleton fig- ured, 220; 557.* Metaphiomys, 201, 534.* Metarhinus, 166, 168, 556.* Metasinopa, 527.* Metaxrytherium, 247, 248, 256, 559.* Meudon, gravier marin and conglomérat de, Wor loge: Meximieux flora, 307, 314. Miacide, Torrejon,' 111; Wasatch, 127; Wind River, 134; Middle and Upper Eocene, American, 156; 528.* Miacis, Wasatch, 127; Wind River, 134; Uinta, 170; 528.* Microbiotherium, 516.* Microcherus, 543.* Microconodon, 515.* Microlestes, 518.* Micromeryzx, Burdigalian, 253; Pontian, 269 ; 552.* Microsus, 547.* Microsyopide, ancestry, 127; Wind River, 134. Microsyops, Wind River, 522.* Microtus, Hay Springs, 457; Port Kennedy Cave, Vindobonian, 262; 130, 134; Bridger, 161; 470; Potter Creek Cave, 477 ; 537.* Migration, during glacial period, 18, 449, 450; crude theories of, 19 ; Cuvier’s views on, 21, 22; routes and barriers, 38, 39; alternate in Pleistocene, 378, 389, * Reference to classification. 624 (table) 390, 407, 419; areas of northern hemisphere in Pleistocene, 443. MItLer, G. S., inbreeding, 502. MILLER, L. H., birds of Rancho la Brea, 473, 474. MILNE Epwarps, birds of Ronzon, 190; birds of Allier Basin, 195; birds of Sansan, 257. Mindel-Riss Interglacial, 378; length, 385; flora and climate, 387, 402. Mioclenide, 109, 546.* Mioclenus, 107, 546.* Miohippus, affinities to Mesohippus, 227 ; John Day, ABIN 2 Bye Miolabis, 294, 550.* Mississippi, rate of deposition, 61. Mizxodectes, 120, 522.* Mixodectide, 109, 111, 522.* Meritherium, Faytim, 200, 203 )-eoosee Mosskirch deposit, 257, 258. Moissaec deposits, 190, 191. Molar teeth, types, 10, 11, 12; relation of to extinc- tion, in ungulates, 238, 239, 240, 241; adaptation to change of vegetation, 240, 244. Monatherium, 533.* Monroe Creek deposit, 231. Montabuzard, calcaire de, 246, 250, 251. Monte Bamboli deposit, 257, 258, 263. Monte Promina deposit, 186, 187. Mt. Léberon deposits, 269 ; correlation, 266, 267. Montmartre gypse, 144, 145; discovered by Cuvier, 22, 57; fauna, 146, 147, 152. 4 Montmaurin cavern, 396; location and correlation, 391, 413. Mt. Pelée, figure, 92. Montpellier deposit and fauna, 314, 315, 316; bird life, 307. Montredon deposit, 269. Moosseedorf lake dwellings, 428. Moret plant beds, 395, 396. Mormont deposit, 144, 148. 203; restoration (head), Moropus, John Day, 224, 230; Agate Spring Quarry, 235; Merycochcerus zone, 286 ; 558.* DE MOortTILLET, European culture stages, 378; 381. Mosbach deposit, 402 ; location, 391. Moschus, 328, 551.* Mouillacitherium, 547 .* Mousterian stage, 410, 411, 412: correlation, 378; relative length, 385. Multituberculata, evolution and extinction in North Amer- ica, diagram, 174. table, AGE OF MAMMALS Muride, first appearance (Oreodon zone), 221; John Day, 230; 536.* Mus, Astian, 316; post-Pleistocene of Eu- rope, 429; 536.* Mustela, Vindobonian, 261; Pontian, 268; Hip- parion zone, 301; mid-Pleistocene, Europe, 407; Upper Pleistocene, Eu- rope, 417; post-Pleistocene, Europe, 429; Port Kennedy Cave, 469; Conard Fissure, 488 ; 530.* Mustelide, Sannoisian, 188, 189; Aquitanian, 197 ; appear in North America, 214; John Day, 230; Burdigalian, 254; Vindo- bonian, 259, 261; Merycochcerus zone, 288; Ticholeptus zone, 296; Hipparion zone, 301; 530.* Mylagaulide, Ticholeptus zone, 289, 297; lower Pliocene, 352, 356; use of horns, 352, Shops Sst Mylagaulodon, 534.* Mylagaulus, 297, 352, 535.* Mylodon, zone, 439, 452-464; superseded by Megalonyx in North America, 440; differs from Paramylodon, 457; from Colorado and Nebraska, 457; Rock Creek, 458; Silver Lake (?), 459; Kansas Pleistocene, 464; Megalonyx zone, 465, 466; Port Kennedy Cave, 469, 470; Ashley River, 472; 541.* Mylohyus, Megalonyx zone, 440, 466; Port Ken- nedy Cave, 470; Frankstown Cave, 471 ; Conard Fissure, 488; 549.* Myodes, 415, 537.* Myogale, 259. Myolagus, Burdigalian, 254; Vindobonian, 259. Myorus, 259, 536.* Nagana, 507. Nanomeryzx, 547.* NEAL, Pliocene of Florida, 346, 347. Neandertal Cave, 410, 412. Neandertal man, see Homo neandertalensis. Nearctica, 35, 95; possible origin of Lower Eocene mammals ha Jue ‘Nebraska’ formation, 87, 297. Nebraska loess man, 499. Necrolemur, 149, 543.* Necrolestes, 520.* NEHRING, Peistocene succession of faunas, 388, 414, 415, 418; Schweizersbild, 418; cave lion, 423; Wurzburg fauna, 426. Nematherium, 541.* * Reference to classification. New Jersey - Oligecen as les Vv INDEX Neohipparion, 350, 351; skeleton and restoration, 243; Madison Valley, 281; whitneyi, discovery of, 298; Snake Creek, 355, 356; two spe- cies from Rattlesnake formation, 358 ; Blanco, 365; 556.* Neolith, Robenhausian, figured, 382. Neolithic period, 428, 429 ; transition to and from, 380; length in years, 385. Neoplagiaulax, Cernaysian, 103; zone of Puerco, 106; Torrejon and Fort Union, 108; 518.* Neoreomys, 539.* Neotoma, 477, 538.* Neotragocerus, 337, 355; zone, 353, 354, 355, (photograph) 355; aS he Nesodon, 560.* Nesokerodon, 539.* NEUMAYR, temperature of Ice Age in Europe, 388. Neurogymnurus, 520.* NEWTON, Red and Norwich Crag, 321; Bed mammals, 3938, 394. Nimravus, 230, 532.* NORDENSKIOLD, Steller’s sea cow, 494. Norfolk Interglacial, 391-399. North-American-Asiatic land connection, see Asiatic-American land connection. North and South American land connection, 93, 292, 339. North Polar theory, 65, 66. Norwich crag fauna, 318, 321. Notharctide, Wind River, 134; 543.* Notharctus, resembles Orohippus in grinding teeth, 3; Wind River, 130, 134; outline resto- ration, 162; Bridger and Washakie, 164 ; 543.* Nothocyon, John Day, 230; zone, 236; 528.* Nothrotherium, 541.* Notopithecus, 543.* Notoprotogonia, 546.* Notostylops, 560* ; zone, 97. Nototherium, 518.* NUESCH, Kesslerloch cave, 425, 426. Nummulitic limestones of Europe, 83. Nyctilestes, 521.* Nyctitherium, 521.* estimated Forest Bridger, 161, 164; Promerycochcerus Ocala fauna, 348. Ocapia, figured, 270; 551.* x Ochotona, 534.* 625 449, 487; Alaskan Pleistocene, 489, 490; 533.* Odocoileus, in Alachua Clays (?), 348; of Mega- lonyx fauna, 465, 466; Port Kennedy Cave, 469; Washtucna Lake, 474; Potter Creek Cave, 477; Big Bone Lick, 478; The Conard Fissure, 488 553.6 (Eningen deposit, 257, 258, 263. Ogallala formation, 298, 353, 354, 355; correlation, 277; overlaid by Pleisto- cene, 461. Olbodotes, 522.* OLDHAM, geology of Indian Tertiaries, 273, 323, 324, 325, 326. Oligobunis, John Day, 230; 288; 530.* Olivola deposit, 318. OLSEN, discovery of Bathyopsis skull, 132. Omomys, 543.* Onohippidion, 556.* Onychodectes, 540.* Oédectes, 131, 134, 528.* D’ORBIGNY, on geologic time divisions, 41. Oreamnos, figured, 437; arrival in North America, Merycochcerus zone, 438, 466, 476; affinities, 483, 484; Alaska, 490; 554.* Oreas, 328, 432, 554.* Oreodon, 220 ; outline restoration, 215; zone, 219, 220, 221, 222, 223, (photographs) 2 217, 226, 228, 290; 549.* Oreodontide, first appearance, 138; ancestry, 149; Uinta, 170; lower White River, 214, 215; of Oreodon zone, 220, 221, 222; John Day, 231; Promerycochoerus zone, 236; Merycochcerus zone, 286; Ticholeptus zone, 293; decline in Hip- parion zone, 299, 300; last (Snake Creek), 355; extinction, 363; 549.* Oreonagor, 432. Oreopithecus, Vindobonian, 255, 263; 545.* l’Orléanais, sables de, 246, 250, 251. Orohippus, evolution, 45; zone, 48, 49, 139, 161, 162; Bridger, 161, 164; outline restora- tion, 162; 555.* Oromeryx, 170, 550.* Orsmeel, deposit and fauna, 100. ORTMANN, on history of Antarctica theory, 76; von Ihering’s hypothesis of Tertiary water barrier in Amazon region, 339. Orycteropus, Odobenus, source, 264; Pontian, 270; 543.* southward migration in Pleistocene, ' Oryx, 432, 554.* * Reference to classification. . 626 Ovibos, Forest Bed (?), 392, 394, 397; Upper Pleistocene of Europe, 412, 413, 424; figured, 436; arrival in North America, 436, 438, 440, 487; zone, 440, 486-494 ; Big Bone Lick, 478; distribution in North America of fossil and recent (map), 485, 492; Alaska, 489, 490, 491 ; DooGs Ovis, Pleistocene North African species, 433 ; montana, 474; Alaska, 490; 554.* OWEN, classification of ungulates, 13; AHyra- cotherium ( =Pliolophus) 116; Eocene birds, 153; Chinese fossils, 333; Pro- rastomus, 494. Oxyacodon, 107. Oxyena, Wasatch, 127; restoration, 133; Wind Riverlesinwos ts Oxyzenide, Wasatch, 127; Wind River, 132, 133; Washakie, 167; Uinta, 168, 170; ex- tinction, 170; 527.* Oxyenodon, 527.* Oxyclenide, 111, 526.* Oxyclenus, 526.* Oxydactylus, Promerycochcerus zone, 236; Mery- cochcerus zone, 286; outline restora- tion, 291; 550.* Ozarkian stage, 435, 443. Pachyena, Sparnacian, 115; Wasatch, 126, 127; Wind River, 1383; 527.* Pachyrukhos, 561.* Pachynolophus, Landenian, 100; Middle and Upper Eocene of Europe, 147. Paciculus, 538.* PALACKY, Upper Miocene ungulates, 246. Palearctica, 35, 95; possible origin of Lower Eocene mam- mals in, 112; distinct from Nearctica, 143. Palearctomys, 535.* Palearctonyx, 528.* Pale@ictops, 125, 520.* Paleocherus, Aquitanian, 197, 198; descendants, 253; Burdigalian, 255; 548.* Paleoerinaceus, 520.* Paleogale, 254, 530.* Palseogeographic maps, world, late Cretaceous, 64; France, Lower Eocene, 114; world, Middle Eo- cene, 137 ; Europe, Middle Eocene, 140 ; world, Oligocene, 183; Europe, Lower Oligocene, 184; France, Upper Oligo- cene, 195; world, Miocene, 245; Eu- rope, Middle Miocene, 256; Europe, AGE OF MAMMALS Upper Miocene, 226; world, Pliocene, 303; Europe, Lower Pliocene, 312; world, Pleistocene, 373; Europe, Gla- cial, 376; northwestern Europe, late Pleistocene, 416. Paleolagus, 221, 534.* Paleolama, 550.* Palzolith, Chellean, figured, 382. Paleolithic period, culture stages, 378, (tables) 379, 381, 383; close of, 412; mammals contem- porary with man of, 427. Paleomastodon, Fayfim, 203; restoration (head), 203 ; 558.* Paleomeryx, affinities, 262; Pontian, 269; Virgin Valley, 357; 551.* Palzonictide, Sparnacian, 115; Wasatch, 126, 127; Wind River, 132; extinction, 138. Paleonictis, Sparnacian, pee tpi es Paleonycteris, 525.* Paleoreas, Pontian, 268; China, 334; 554.* Paleorycteropus, 543.* Paleoryz, Pontian, 268; of ‘older Pliocene fauna,’ S1ON S125 316en aoa Paleosinopa, 125, 519.* Paleosyops, molar figured, 11; skull figured, 17; Bridger and Washakie, 161, 164; out- line restoration, 162; skeleton figured, 163; 556.* Paleothentes, 517.* Paleotheriide, Middle and Upper Eocene of Europe, 141, 146, 147; decline in Oligocene, 188 ; extinction, 193; 555.* Paleotherium, adaptive radiation observed in gypse, 146; Sannoisian, 188; 555.* Paleotragus, 268, 551.* Palhyena, 334. PALLARY, Pleistocene, North African giraffe, 432. Palorchestes, 518.* Panhandle formation, 360, 361, 362. Panochthus, 542.* Pantolambda, zone, 107; outline restoration, 108; skeleton and restoration, 110; Torrejon, 110, 111; 546+ Pantolambdide, 110, 111, 546.* Pantolestes, 161, 519.* Pantolestide, Torrejon, 109; Wasatch, 125; 519.* Paracamelus, 333. Paradaphenus, 230. Parahippus, first appearance, 115; Wasatch, 119, 126, 233) +8) Zone Vee et ias * Reference to classification. INDEX 627 Merycochcerus zone, 287; Ticholeptus | Perissodactyla, zone, 293; Hipparion zone, 297, 298; Holarctic origin, 68, 202; growing Snake Creek, 355; Virgin Valley, 357 ; importance in Upper Eocene, 147; 555:* Parahyus, 127, 549.* Paramylodon, 457 ; Springs, 456; 541.* Paramys, Wasatch, 128; Wind River, Washakie, 165; Uinta, 168; 534.* Pararctotherium, 530.* Paratapirus, Stampian, 190; Aquitanian, 198; 556. Paratylopus, 231. Parictops, 520.* Paris basin, lagoons and gypse, 140, 141; grossier, 143, 144. Patriofelis, Wind River, 131, 133; outline restora- tion, 162; Bridger, 164; skeleton and restoration, 165; 527.* Pawnee Buttes, correlation, 41, 277; (photograph) 290. Pawnee Creek deposit, 288, 289. Peace Creek formation, 366, 367, 368; alternation of shell-bearing and mam- mal-bearing layers, 337; commingling of faunas, 453. PEALE, voleanic ash in Bozeman Lake deposit, 90. Pediomys, 515.* Pelecydon, 541.* Peltephilus, 542.* Pelycictis, 469. Pelycodus, 134, 543.* PENCK, duration of Quaternary, 64, 385; divi- sions of the Quaternary in Switzerland, 376, 377, 378, (table) 379; differs from Boule on correlation, 380, 404, 410; Dryopithecus as an eolith-maker, 384; origin of loess, 386; temperature of Glacial Period, 388; alternation of faunas in Pleistocene, 388, 389; age of Schweizersbild cave, 425; correlation of Solutrian, 427. Pentacodon, 519.* Peorian Interglacial, 444, 446. Peraceras, 348 ; zone, 348, 349, 350; swperciliosus, 352 ; 557.* Peratherium, Wind River, 133 ; Ludian, 146; Bridger, 154, 161; Lower White River, 213, 216; Oreodon zone, 221; 516.* Percherus, Oreodon zone, 220, 223; John Day, 231. Perim Island deposit and fauna, 274, 324. Perimys, 540.* Periptychide, 110, 111, 546.* Periptychus, 107, 546.* Equus zone, 454; Hay Rancho la Brea, 473; 154 ; calcaire grand epoch of, 156; evolution in North America, charted, 174; of Old and New Worlds share many families in Oligo- cene, 179; reduced to four families, 230; evolution in North America charted, 239. Pernatherium, 143, 558.* Perrier, hipparion fauna, 316, 317; Upper Pliocene fauna, 319. PETERSON, entelodonts, 217, 218; Thinohyus, 232; Demonelix, 235; exploration of Agate Spring Quarry, 235; Lower Miocene of Great Plains, 285. Phacocherus, 433, 549.* Pharsophorus, 516.* Phascolonus, 518.* Phascolotherium, 515.* Phenacocelus, Promerycochcerus zone, 233; outline restoration, 236; 550.* Phenacodontide, Torrejon, 110, 111; extinction, 138, 172; 546.* Phenacodus, considered stem form of ungulates, 7, 125; Landenian, 100; Wasatch, 119; 124, 125; skeleton and _ restoration, 126; Wind River, 132; causes of ex- tinction, 172; brain figured, 173; 546.* Philotrox, 230. Phiomys, 201, 534.* Phlaocyon, 288, 529.* Phocide, Pliocene, 317, 321; 533.* Pholidota, 68, 71, 547.* Phosphorites, 58 ; Quercy, 151; Pleistocene, 386. Physodon, 562.* Pikermi deposit, 267, 268; Wallace on, 68; correlation, 266. PILGRIM, Bugti hills Suid, 275. Pipestone Creek deposit, 212, 216, 217, 281. Pithecanthropus, 384, 385, 545.* Plagiaulacide, Thanetian, 103; -Torrejon, satch times, 119, 124; 518.* Plagiaulax, 518 ;* evolution of molars marks lapse of time, 45. Plagiolophus, Ludian, 146, 147 ; Sannoisian, 188 ; 555.* Plaisancian stage, 311, 312, 313; correlation, 41, 309; palweogeography, 305, (map) 312; localities (map), 310; fauna summarized, 310, 311. Planops, 541.* Platygonus, Rattlesnake, 358; Blanco, 364; Equus 111; Wa- * Reference to classification. 628 zone, 439, 455; Hay Springs, 457; Rock Creek, 458; Silver Lake 460; skeleton figured, 462; discovery of nine skeletons at Goodland, 463; restora- tion, 463; Twelve-mile Creek, 463 ; Potter Creek Cave (?), 477; 549.* Plesiadapis, Landenian, 100; Ypresian, 118; 543.* Plesiaddax, 334. Plesiarctomys, 118, 149, 534.* Plesictis, 197, 530.* Plesiocetus, 563.* Plesiodimylus, 521.* Plesiomeryx, 548.* Plesiometacarpal deer, 302. Plesiosorex, 522.* Pleuraspidotherium, 103, 546.* Pleurolicus, 536.* Pliauchenia, 300, 346, 352 ; Hipparion zone, 299; Long Island quarry, 349; Snake Creek, 356; 550.* Pliohippus, 350 ; early Pliocene (?), 346, 349; Snake Creek, 355; in dental type approxi- mates Hippidion, 356 ; Rattlesnake, 358 ; Blanco, 365; 556.* Pliohylobates, 271. Pliohyrax, 71; appears in Europe, 264, 271; 559.* Pliopithecus, 271, 272 ; enters Europe, 247, 254; 260, 261; 545.* Poébrotherium, 220, 550.* PouHuia, Pleistocene physiographic changes, 373, 374, 406, 410; divisions of the Pleisto- cene in northern Europe, 377; LE. trogontherii, 400, 407; EH. hemionus in European Pleistocene, 401; phylogeny of E. primigenius, 405; reindeer dis- tribution, 413; woolly rhinoceros, 421 ; fauna of Thuringian Pleistocene, 426, 428; Solutrian, 427. Polymastodon, zone, Puerco, 106; Torrejon, 108; 518. Polyphyletic law, discovered by Gaudry, 6; in Oligocene and Miocene, 30, 31; illustrated among rhinoceroses, 272. POMEL, separation of Europe and North Africa in Quaternary, 430; Pleistocene fauna of North Africa, 431, 432, 433. Pont-a-Mousson flora, 387. Pontian stage, 264-272 ; physiography, 246, 265, correlation, 249; palseogeographic maps, 266, 267. Port Kennedy Cave, 467, 468, 469, 470. Potamotherium, Stampian, 192; Ticholeptus zone, 289 ; Hipparion zone, 301; 531.* Potter Creek Cave, 467, 475, 476, 477; evidence of early man in, 477, 498. Pourcy deposits, 102, 115. Vindobonian, AGE OF MAMMALS Prepotherium, 541.* Preptoceras, of Megalonyx zone, 466; Samwel Cave, 478; 554.* PRICHARD, influence of severe winters on guanacos of Patagonia, 502. Primates, in Fayfim, 73; first appearance, 127; modernization, 134; evolution in North America charted, 174; Middle Miocene, European, 263, 264; Upper Miocene, 271, 272; Pliocene, 307, 310, 311; dis- appear from Europe, 320; Siwalik, 327. Prince’s Cave of Monaco, 410. Pristiphoca, 317, 533.* Proelurus, 197, 530.* Proboscidea, Africa as possible source of, 73, 481; evolution in North America, charted, 174; enter Europe, 242, 244, 246; Vindobonian, 262; evolution in Asia, 327, 330, 331, 332; distribution in North America (maps), 439; distribution of fossil and recent (map), 505; 558.* Procamelus, 300, 301 ; Madison Valley, 281; zone, 297-302 ; early Pliocene (?), 346, 352; Snake Creek, 356; Virgin Valley, 357; 550.* Procynictis, 104. Procynodictis, 169, 170, 528.* Procyon, Ashley River, 472 ; Conard Fissure, 488 ; 529.* Procyonide, first appearance, 288; Hipparion zone, 301; 529.* Prodremotherium, 550.* Proéctocion, 546.* Proeutatus, 542.* Progenetta, 261, 531.* Prolagostomus, 539.* Prolagus, 534.* Promeles, 530.* : Promephitis, 268, 530.* Pronomotherium, 300 ; outline restoration (head), 291; 550.* Promerycocherus, first appearance, 231; skull figured, 231 ; ZONE, Lol Zaz, 2od0s. 204, sLooymees os (photograph) 177, 232; outline restora- tion, 236; Deep River, 293; 549.* Propachynolophus, 118, 555.* Propaleocherus, stem form of Old World pigs, 198, 199 ; 548.* Propaleohoplophorus, 542.* Propaleotherium, 555.* Prophoca, 533.* Proplesictis, 189, 530.* Proputorius, 530.* Propyrotherium, 561.* Prorastomus, 182, 494, 559.* Prorosmarus, 533.* ** Reference to classification. INDEX Proscalops, 521.* Proscapanus, 521.* Prosciurus, 221, 534.* Prosqualodon, 561.* Prosthennops, Hipparion zone, 301; early Pliocene, 352; Snake Creek, 356; Virgin Valley, 357; 549.* Protagriocherus, 170, 549.* Protapirus, Stampian, 190; Oreodon zone, 223; Protoceras zone, 227; John Day, 2380; 556.* Protechimys, 538.* Protelotherium, 168. Proteodidelphys, 515.* Proteriz, 221, 520.* Proterotherium, 561.* Prothylacynus, 516.* Protitanotherium, outline restoration (head), 142: Uinta, 169; 556.* Protoadapis, 118, 543.* Protoceras, 226, 227; molar figured, 11; sandstones (photograph), 217; zone, 225, 226, 227; restoration and skeleton figured, 225; 551.* Protocetus, 561.* Protodichobune, 118. Protogonodon, 170, 546.* Protohippus, 297, 350 ; zone, 277; Madison early Pliocene (?), 346; 355; Blanco, 365; 556.* Protolabis, 299, 550.* Protomeryx, 286. Protoptychus, 168, 536,* 538.* Protoreodon, 170, 549.* Protorohippus, foot figured, 14. Protosiren, 182. Protosorex, 521.* Protragelaphus, 554.* Protragocerus, ‘ first appearance, 247, 249, 253, Vindobonian, 259, 262; 553.* Protylopus, 170, 550.* Protypotherium, 560.* Proviverra, 527.* Prozaédius, 542.* Prozeuglodon, 200, 561.* Pseudelurus, Stampian, 192; Burdigalian, 254, 255; Vindobonian, 259, 261; MHipparion zone, 301; 532.* Pseudarctos, 262, 530.* Pseudocyon, 529.* Pseudolabis, 227, 550.* Pseudotomus, 534.* Psittacotherium, 109, 540.* Pterodon, Fayim, 201; restoration, 201; 527.* Ptilodus, skull figured, 106 ; Fort Union, 108 ; 518.* Valley, 281; Snake Creek, 255); Puerco formation, location, 86, 87, 104; correlation, 99; fauna, 106, 107. PuTNnaM, man in California mid-Pleistocene, 477, 498; human and mastodon remains at Worcester, 495. Putorius, Hipparion zone, 301; Conard Fissure, 488; 530.* Puy Courny deposits, 266, 267. Pyrenees, elevation of, 59, 60, 140, 177. Pyrimont deposit, 193, 194; fauna, 197, 198. Pyrotheria, 78, 561.* Pyrotherium, 561.* QUACKENBUSH, Pleistocene of Alaska, 490, 491, 492. Quaternary, faunal periods, 375; time divisions in Switzerland, 376, 378, in Germany, 378. Quercy phosphorites, 151, 152; discovered, 5; correlation, 144, 145, 168, 187; final deposits, 190. Quercytherium, 145, 527.* Rancho la Brea, asphalt, 58, 472; correlation, 467; fauna, 472, 473, 474; photograph, 473. Rangifer, mid-Pleistocene (?) Europe, 400, 403, 407; Upper Pleistocene of Europe, 412, 413; Eurasiatic and American, 422; survival in Europe, 424; _ post- Pleistocene, Europe, 428; figured, 436; arrival in North America, 436, 438, 487 ; zone, 440; Toronto formation, 449; Pleistocene range in North America, 449; Big Bone Lick (?), 478; Iroquois Beach, 489; Alaska, 489, 490, 491; Doze Rattlesnake formation, 357, 358 ; correlation, 41, 309, 341; photograph, 358; section, 359. Rectigradations, 46 ; early titanothere horns, 164. Red Crag of Suffolk, 314, 317, 321, 393; bird life, 307. REIp, flora of Norfolk Interglacial, 393, 396; climate of Norfolk Interglacial, 396, 397. Reindeer, see Rangifer. Reindeer Period, 378, 427. Reptiles, megalosaurs of Belgium and Rocky Mountain region, 98; Landenian, 100; Basal. Eocene, 102; Thanetian, 104; Puerco, 106; Sparnacian, 115; Ypre- sian, 117; Wasatch, 124, 129: Wind River, 129; Lutetian, 140; Ludian, 147; Bridger, 160, 161; White River, 185; Faytiim, 200; Oligocene North * Reference to classification. 630 American, 208, 210; Cypress Hills, 216; John Day, 228; C£ningen, 263; Arikaree, 288; Roussillon, 316; Peace Creek, 368; Port Kennedy Cave, 470. Republican River formation, 348, 349, 350 ; correlation, 41, 309, 341. Rhagatherium, phylogeny, 148, 149; Faytim, 201. Rheims, Basal and Lower Eocene deposits near, 99, 100, 115. Rhinoceros, molar figured, 11; brain figured, 173. Rhinoceros, phylum, 272; sivalensis of Miocene of India, 275; palwindicus of Siwaliks, 327: of China, 334; 558.* Rhinocerotide, Oligocene of Europe, 190, 197; appear in North America (Lower White River), 213; increased by two new phyla, 247 ; seven Miocene phyla, 272; diminution in European Pliocene, 309 ; Siwalik, 327 ; multiple phyla in American Pliocene, 351, 352; European Pleistocene, 390; North American origin of, 431; distribu- tion of fossil and recent (map), 505. Rhinolophus, 259. Rhizomys, 327. Rhodanomys, 195, 534.* Rhynchippus, 560.* Rhytina stelleri, 494, 559.* Ricardolydekkeria, 546.* RICHTHOFEN, loess formation, 417. Riaaes, Demonelix, 235. Rilly, sables blancs siliceux de, 99. Riss Glaciation, 378 ; flora, 388. Riss-Wiirm Interglacial, 378 ; length, 385. Rixdorf deposit, 402 ; location, 391. Robenhausen lake dwellings, 428. Robiac marls, 144. Roccaneyra fauna, 316, 317. Rock Creek formation, 458 ; geology, 362; correlation, 453; quarry containing Hquus scottiskeletons (sketch), 456, (photograph) 457. Rodentia, Holarctic origin, 68; Wasatch, 128; Wind River, 134; Eocene, forest living, 149; Middle and Upper Eocene, Amer- ican, 156; evolution in North America charted, 174; Vindobonian, 261; Mery- cochcerus zone, 287; Hipparion zone, 302; Siwaliks, 327; early Pliocene, American, 352, 353; 533.* Rop.eR and WEITHOFER, Maragha, 270. RoGER, Middle Miocene of Germany, 262. foot figured, 16; AGE OF MAMMALS RomMAN, two races of Dicerorhinus, 252; and F.icue, on Horta de Tripas deposits, 255. Ronzon marls, fauna, 186, covered, 5. Ronzotherium, 188, 557.* Rorqualis, 317. Rosebud formation, 231, 234, 285; photograph, 177; correlation, 41, 277; section, 287. Roussillon deposit and fauna, 314, 315, 316; bird life, 307. RUTIMEYER, method of research, 8; bipolar theory, 65, 75; on invasion of Africa by Euro- pean mammals, 68; Middle Eocene (Egerkingen) mammals, 142, 143; source of North African fauna, 409; fauna of Swiss lake dwellings, 428; phylogeny of domestic cattle, 429. Rupicapra, 424, 428, 554.* Ruscinomys, 311, 316. RUSSELL, voleanic ash deposits, 92; spearhead in Lahontan basin, 497. Rutort, Eolithic stage, 382, 384; eoliths, 399. 187, 188, 189, 190; dis- discovery of Saber tooth tigers, see Macherodontine, Macherodus, Hoplophoneus, Dinictis, ete. Saghatherium, 202, 559.* Saiga, 417, 554.* St. Gaudens, a stage of, 263, 264. St. Gérand-le-Puy deposits, 193, 194; fauna, 195, 196. St. Ouen deposits, 144. St. Prest, 391, 395, 396, 399. SALENSKY, Beresowka mammoth, 419, 420. Samos deposit, 270 ; correlation, 266, 267. Samotherium, 270, 551.* Samwel Cave, 467, 477, 478; evidence of early man in, 477, 498. Sangamon Interglacial, 444, 445, 446 ; Toronto formation of, 447, 448, 449. San Isidro deposit, 257, 258, 263. Sanitherium, 329. Sannoisian stage, 187, 188, 189, 190; correlation, 182; palseogeographic map of Europe, 184; map of localities, 186. San Pedro stage, 444. Sansan, deposit discovered, 4; stage of, 257, 258, 259, 260. Santa Fe marls, 87, 298. DE SAPORTA, Oligocene climate of Europe, 185; Pontian flora, 266; flora of the Quater- nary tuffs of Provence, 401, 402. - * Reference to classification. INDEX Sarcolemur, 547.* Sarcothraustes, 111, 527.* Sarmatian marine stage, 257. Scalabrinitherium, 561.* Scalops, 469, 521.* Scaptonyx, 521.* Searborough beds, flora, 449. Scelidotherium, 541.* ScHARFF, northern center of evolution, 66, 67; early Cenozoic, North and South American land connection, 93, 292; steppe mammals no sure indication of steppe country, 417; migration of rein- deer, 422; origin of badger, 424. ScHIMPER and SCHENCK, fossil grasses, 94. Schismotherium, 541.* Schistomys, 540.* Schizotherium, 193, 558.* SCHLOSSER, Literaturbericht, 51; origin of African fauna, 69; theridomyids, 146; Tertiary bear, 261, 269; Samos Cavicornia, 270; ‘Anthracotherium’ fauna of India, 274; Maragha fauna, 332; Miocene and Pliocene fauna of China, 333, 334, 335; survival of chalicotheres into Pleistocene, 338. ScHOTENSACK, age of Mauer sands, 399; Homo heidel- bergensis, 403, 404. ‘ ScHUCHERT, Zeuglodon beds, 171. ScHWALBE, Middle Miocene primates, 263, 264; Upper Miocene primates, 271, 272; 4 Pliocene primates, 307; Pithecanthro- pus, 385. ScHWEINFURTH, discoveries in Fayfim, 199. Schweizersbild cave, 418, 419, 425. location and correlation, 391, 413. Sciuravus, Wasatch, 128; Wind River, 134; 534.* Sciuride, ancestry, 128; Oreodon zone, 221; Vindobonian, 259; 535.* Sciurodon, 534.* Sciuroides, 534.* Sciuropterus, Vindobonian, 259, 261, 262; of ‘older Pliocene fauna,’ 311, 316; Potter Creek Cave, 477; 535.* Sciurus, Aquitanian, 195; Vindobonian, 259; Pleistocene forest fauna of Europe, 415, 417; post-Pleistocene, Europe, 428; Port Kennedy Cave, 469; Potter Creek Cave, 477 ; 535.* ScLATER, on zoogeographic divisions, 35, 36. Sclerocalyptus, 542.* Scleromys, 539.* 631 Scorr, convergence in evolution, 32; ancestry of oreodonts, 149; Hyaenodon aquatic, 222; Middle John Day corresponds to St. Gérand-le-Puy, 229; Deep River, 281, 289; Hypohippus, 293; Miocene Canide, 296; Nebraska formation, 297; Cervalces, 492, 493; coexistence of man and mastodon in North America, 495. Scott’s Bluff (photograph), 228. SCUDDER, Florissant Lake, 283; effect of the Glacial Period on American insect life, 450, 451. Semnopithecus, of ‘older Pliocene fauna,’ 310, 312, 315, 316; Siwaliks, 327; 545.* Sézanne, travertin de, 102, 114. Sheppey, deposits on Isle of, 102, 115, 117; birds of, 152: SHUFELDT, Silver Lake, 459, 460, 461. Sicilian stage, 317, 318, 319, 320, 321; correlation, 41, 309; palseogeography, 305, 318; localities (map), 310; fauna summarized, 311. Sierran stage, 435, 443. Silver Lake deposit, 458, 459, 460; age of, 453; comparison with Hay Springs fauna, 457; flints, 497. Simia, 327, 545.* Simocyon, 269, 529.* Simorre, stage of, 260, 261, 262. SINCLAIR, Antarctica, 76; volcanic nature of Bridger and Washakie, 91, 158; eden- tates in Masceall, 289; section of John Day formation, 359 ; Potter Creek Cave, 475, 476; human remains in auriferous gravels, 500. Sinopa, Wasatch, 127; Wind River, 133; Bridger and Washakie, 161, 164; 527.* Sirenia, possible African origin, 73, 493; Eocene and Oligocene, 182, 183; possible affini- ties to Proboseidea, 204; Miocene, 247, 255, 256; Pliocene, 317, 344; source of American, 493; Pliocene and Pleisto- cene of North America, 493, 494; 559.* Sivameryx, 274. Sivatherium, 551.* Siwaliks, correlation, 41; DiA MaZomocs 332; age, 332. Skanian Interglacial fauna, 377. distribution, geology, 325, 326; fauna, 323-— Smilodon, Megalonyx zone, 467; Port Kennedy Cave, 470; Rancho la Bréa, 473; skeleton figured, 474; restoration, 475; Doves * Reference to classification. 632 Smilodontopsis, Ovibos zone, 487; Conard Fissure, 488. Smita, J. P., Tertiary physiography of western North America, 92, 93, 175, 282, 343, 443. Snake Creek formation, 353, 354, 355 ; correlation, 341. Soissons, argiles plastiques et lignites de, 102, 114, 115. Solhilac, 391, 392, 395. SOLLAS, thickness of sedimentary deposits, 58, 59: duration of Cenozoic, 64; duration of Pleistocene, 385. Solutré paleolithic encampment, 427. Solutrian stage, 427; correlation, 378. Sorex, 259, 521.* South polar theory, 65. Spalacotherium, 515.* Spaniomys, 539.* Sparnacian stage, 114, 115; correlation, 42, 83, 99, 100, 114; map of localities, 102. Spermophilus, Pleistocene Europe, 407, 417; Potter Creek Cave, 477 ; 535.* Sphenophalos, 338, 357, 554.* Spy Cave, 410. Squalodon, 251, 561.* Stitzling deposits, 258, 263. Stampian stage, 190, 191, 192, 193; corre- lation, 182; map of localities, 191; Quercy, 151. Stegodon, 330, 331; Japan, 322; Java, 323; Siwaliks, 324, 326; type in America, 360, 364, 366; 558.* Stegotherium, 542.* STEHLIN, Africa as an evolution center, 70, 71, 72 ; separation of New and Old Worlds in Middle Eocene, 137 ; Middle and Upper Eocene fauna of Europe, 141; Dicho- bunide, 147; Eocene suillines and anthracotheres, 148, 149; Oligocene suillines, 198, 199; sables de 1’Orléanais, 251; Miocene suillines, 253, 260; ancestry of hippopotami, 313; hip- parion fauna of Perrier, 317; and HARLE, Cajare, 395, 396. Steinheim deposit, 261. Steiromys, 539.* Steneofiber, Stampian, 191; Aquitanian, 195, 198; Upper Oligocene, North American, 224, 226; John Day, 228, 229; last appear- ance, 233; 535.* Stenogale, 254, 530.* Stenomylus, Promerycochcerus zone, 234, 236; quarry (photograph), 234; 550.* Stenoplesictis, 254, 530.* Stenotatus, 542.* Steppe fauna (summarized) of Pleistocene, 414, 415, 388, 416, 412; 417, AGE OF MAMMALS (Schweizersbild) 418, (Kesslerloch) 426 ; horse of, 409, 412, 417; retreat of, 428. STERNBERG, herds of tortoises on Pliocene Great Plains, 342, 350; Long Island Quarry, 349, 350. Sternberg’s elephant bed, 461, 463. Sthenurus, 518.* Stibarus, 547.* Stichomys, 539.* Stilotherium, 517.* Strepsiceros, Siwaliks, 328; Pliocene distribution of antelopes allied to (map), 336, 337, 338 ; recent, figured, 338; 554.* STRUTT, on geologic time measured by helium content of rocks, 62, 63. STUDER, Briittelen fauna, 255; crowding out of tundra fauna, 419 ; Kesslerloch horse, 426. Stylinodon, Wind River, 133; Bridger, 155; 540.* Sub-Aftonian Glacial, 435, 445. SUESS, stability of North America during Czeno- zoic, 84. Suessonian Sea, 114, 141. Suidee, Ludian, 148; three phyla in European Eocene, 148; Aquitanian, 197; phy- logeny of Oligocene, 198, 199; Miocene, 253, 260; 548.* Surra, 507. Sus, brain figured, 173; evolution of, 260; Vindobonian, 262; Miocene of India, 275; of ‘older Pliocene fauna,’ 312, 316, 317; Sicilian, 321; Siwalik, 329; mid-Pleistocene of Europe, 407; post- Pleistocene of Europe, 428; Pleistocene of North Africa, 433; 548.* Siissenborn deposit, 402, 403 ; location, 391. Swift Current Creek deposit, 212 ; ; location, 204; titanotheres, 214. Symborodon, restoration (head), 212; Symbos, Ovibos zone (Conard Fissure), 487, 488 ; Alaska, 490; 554.* Synchronism, 39, 43, 44, 45, 46, 47. Syndyoceras, 236 ; 556.* outline restoration (head), 236; skull figured, 237; 551.* Synoplotherium, 527.* Systemodon, 127, 556.* Teeniodonta, Holarctie origin, 68; Puerco, 107; Torrejon, 109, 111; Wasatch, 125; Wind River, 132; last appearance, Bridger, 155; evolution and extinction, charted, 174; 540.* * Reference to classification. INDEX Talpa, Burdigalian, 254; Astian, 316; 521.* Talpavus, 521.* Talpide, first appearance (Europe), 149; Oreo- don zone, 221; Burdigalian, 254; 521.* Tapiravus, Hipparion zone, 299; 302 > DOOss Tapiride, Wasatch, 127; Wind River (?), 135; Middle and Upper Eocene, American, 156; first appearance in Europe, 190; Aquitanian, 197; Miocene of Europe, 251, 263; of North America, 279, 293, 299, 300; Pliocene of Europe, 315, 318, 320; Siwalik, 327; American Pleisto- cene (disappearance), 438, 440, 500; undoubted existence in forests of Equus zone, 455; of Megalonyx zone, 466; Lower Pliocene, 556.* Tapirus, molar figured, 11; casino, 312; arver- nensis, 315, 318, 320; Siwalik, 327; China, 335; Port Kennedy Cave, 469; Ashley River, 471, 472; Megalonyx zone, 484; 557.* Tarrega deposit, 186, 187. Taubach, 406, 407 ; location, 391; correlation, 405. Taxidea, Equus zone, 439, 454; Cave, 470; 531.* Telemetacarpal deer, 302. Teleoceras, 252, 352; foot figured, 16; phylum enters Europe, 247, 248, 249; awrelianensis of Burdi- galian, 252; skull figured 252; medi- cornutus (skull figured), 252, (of Pawnee Creek) 292, 352; of the Tagus valley, 255; brachypus of Vindobonian, 262; perimensis of Miocene of India, 275, 327 ; crassus of Hipparion zone, 300; Chinese, 333; fossiger, 348, 349, 350, (skeleton figured) 349; restoration, 349; 557.* Teleoceratinz, 272 ; migration, 292; Hipparion zone, 300; highest development, 338, 346. Teleopternus, 469, 470. Telmatherium, 164, 556.* Temnocyon, 230, 529.* “Temperature zones,’ 38. Teonoma, 477. Tephrocyon, 296, 356, 528.* Tetracerus, 328, 553.* Tetraclenodon, 110. Tetraconodon, 326, 329. Tetracus, 520.* Tetralophodon, longirostris of Pontian, 271, 331; peri- mensis of Miocene of India, 275, 331; Siwalik species, 330, 331; campester, euhypodon, 353 ; 558.* Tetraselenodon, 548.* Port Kennedy 633 Thanetian stage, 103, 104; correlation, 42, 83, 99; map of localities, 102. Theosodon, 561.* Theridomyide, Fayim, 73; Ludian, 146; Sannoisian, 189; Aquitanian, 195; Vindobonian, 259; 538.* Theridomys, 195, 538.* Thiede deposits, 415, 418. Thinocyon, 527.* Thinohyus, Promerycocherus zone, 232; outline restoration (head), 291; 549.* Thoatherium, 561.* Thomomys, Hay Springs, 457; Potter Creek Cave, 477 ; THOMPSON-SETON, range of the wapiti, 450. THOMSON, Lower Miocene geology of Great Plains, 285, 287. Thousand Creek deposits, 356, 357 ; correlation, 41. Threeforks deposit, 204. Thuringian deposits, 413, 426. Thylacoleo, 517.* Ticholeptus, zone, 288-297, (photograph) 290; Deep River, 281; skull figured, 288 ; affinities, Silver Lake, 536.* 460 ; 293; 550.* Tillodontia, Holarctic origin, 68; Wasatch, 125; Wind ‘River, 132; last appearance, Bridger, 155; evolution and extinction charted, 174; 523.* Tillotherium, Bridger, 155 ; 523+ Time divisions of Csenozoic, 40, 41, 43. Tinoceras, 166, 547.* Titanomys, Stampian, 191; Aquitanian, 195; Pon- tian, 269; 534.* Titanotheriide, Wind River, 130, 134; peculiar to North America (?), 156,.213; become polyphyletic, 164; restoration of Lower Oligocene (heads), 212; adaptive radia- tion, 212, 213, 214; extinction, 239, 240; 556.* Titanotherium, 213 ; zone, 52, 210, 212-217, (photographs) 178, 206, 210; restoration (head), 212; Bulgaria, 213 ; Oreodon zone, 220 ; 556.* Tongrian stage, see Sannoisian and Stampian. Toronto formation, flora and insects, 447, 449. Torrejon formation, location, 86, 87, 104; correlation, 99, photograph, 105; fauna, 107, 108, 109, OST outline restoration, 162; * Reference to classification. 634 Tortonian marine stage, 257. Toussaint, Solutré camp, 427. Toxodon, 560.* Toxodontia, 78, 560.* Tragocerus, Pontian, 268, 269; China, 334; 553.* Tragulide, Miocene, 249; Burdigalian, 253; Si- waliks, 328; 551.* Tragulus, 328, 551.* Trechomys, 538.* Trenton man, 499, 500. Tricentes, 111, 526.* Trichecodon, 395. Triconadon, 515.* Triglyphus, 518.* Trigonias, 213, 557.* Trigonolestes, 127, 547.* Trigonolestide, 127, 547.* Trigonostylops, 560.* Triisodon, 527.* Trilophodon, angustidens of Burdigalian and Vindo- bonian, 253, 254, 255, 259, 262, 275, 331; pygmeus of Algerian Miocene, 254; pentelict of Pontian, 271, 331; pandionis of Miocene of India, 275; Deep River (?), Madison Valley, 281; proavus and brevidens of Ticholeptus zone, 292; productus of Clarendon, 299, 300, (skull figured) 299; Siwalik species, 331; restoration, 441; 558.* Trilophomys, 311, 316. Triplopus, 166, 168, 557.* Tritemnodon, Wind River, 131, 133; Bridger, 161; skeleton figured, 163; 527.* Tritubercular molar, of Triisodon figured 10; evolution of, 11. Trituberculy, prevalence of among primitive forms demonstrated by Cope, 10. Tritylodon, 518.* Trochictis, 530.* Trogolemur, 522.* Trogontherium, Pliocene of England, 321; Norfolk Interglacial, 392, 396; mid-Pleistocene, Europe, 401; last appearance, 403, 404; 535.* Trogosus, 523.* Tubulidentata, 68, 71. TULLBERG, on Africa as an evolution center, 70, 72. Tundra fauna, of Pleistocene, 388, 412, (summarized) 414, 415, (Schweizersbild) 418, (Kessler- loch) 426 ; crowding out of, 419, 428. TURNER, Pliocene flora of California, 344. Twelve-mile Creek deposit, 461, 463, 464. Typotherium, 561.* AGE OF MAMMALS Uinta formation, 165, 166, 167, 168, 169, 170; correlation, 42, 139, 153; location, 86, 87; sections, 155, 169 ; photograph, 168. Uintacyon, 127, 528.* Uintasorex, 522.* : Uintatheriids, 132, 547.* Uintatherium, skeleton figured, 155; Bridger and Washakie, 163, 164; zone, 163-166; brain figured, 173; 547.* Ulm deposit, 193, 194. UPHAM, duration of Cenozoic, 63; duration of Pleistocene, 385. Urmiatherium, Pontian, 270, 332; China, 334. Urocyon, Potter Creek Cave, 477; Conard Fis- sure, 488; 528.* Ursavus, 261, 529.* Urside, Vindobonian, 255; Eurasiatic origin, 431; 529.* Ursus, béckhi (Pontian), 261 ; minutus (Astian), 315; arvernensis (Sicilian), 318, 319; arctos, 400, 403, 407, 423, 429; speleus, 407, (characters) 423; Pleistocene of North Africa, 433; arrival in North America, 437, 438 ; americanus, (figured) 437, 469, (skull figured) 476, 477, 478, 488; Alaskan Pleistocene, 490; 530.* Urus, see Bos primigenius. Val d’ Arno, ; fauna, 318, 320, 321; flora, 307; upper deposits, 392; H. meridionalis of, 398. Vermeil, lignites de, 186, 187. Vespertilio, Vindobonian, 259 ; Port Kennedy Cave, 469; 525.* ’ Vindobonian stage, 255-264 ; physiography, 246, 256, 257; correla- tion, 249; palwogeographic maps, 256, 258. Virgin Valley formation, 356, 357; correla- tion, 41; antelopes, 338. Vishnutherium, 551.* Viverra, Vindobonian, 259, 261; Siwaliks, 327; 531.* Viverravus, Wasatch, 127; Wind River, 134; 528.* Viverride, Aquitanian, 261 ; 531.* Voklinshofen deposits, 426 ; location and correlation, 391, 413. Voitsberg deposits, 257, 258, 260. Volcanic materials in North American forma- tions, 90, 91. Vulpavus, Wasatch, 127; Wind River, 134; 528.* Astian, 315; 197; Vindobonian, 259, * Reference to classification. INDEX Vulpes, Astian, 316; Siwaliks, 327; China, 334; Potter Creek Cave, 477; Conard Fissure, 488; 528.* WAAGEN, methods in invertebrate paleontology, 7,9; ‘mutations’ of, 45. WaLcort, on duration of Csenozoic, 63. WALLACE, zoogeographic divisions, 35; duration of Cenozoic, 58, 63; invasion of Africa by northern mammals, 68; means of dispersal of mammals, 80; effect of insular conditions on fauna, 176; date of last glacial advance, 385. WARD, Tertiary flora, 94; duration of Pleisto- cene, 385. Wasatch formation, 118, 119, 122, 123, 124, 125 1265 L275 128 - correlation, 42, 114; location and origin, 86, 87; sections, 119, 123, 154; photo- graph, 122. Washakie formation, 158, 159, 160, 163, 164, 165, 166, 167; correlation, 42, 139; zones, location, 86, 87; sections,. 153, photographs, 158, 167. Washakius, 130, 134, 543.* Washtucna Lake deposit, 456, 467, 474. Wauwy! lake dwellings, 428. Weisenau deposit, 193, 194. : White Buttes deposit, 204, 217. White River formation, lower, 210, 212-217; upper, 219-223; correlation, 42, 182; location, 87, 204; section, 154; photograph, 177; pano- rama, 207. WHITNEY, man and the mastodon, 495. Wies deposits, 257, 258, 260. Wight, Isle of, deposits, 145. Wildkirchli cave, 410. WILLIAMS, on methods of calculating rate of deposi- tion, 61; duration of Pleistocene, 385. WILLISTON, age of Equus fauna, 453; Kansas Pleis- tocene, 454, 461; discovery of Platy- gonus at Goodland, 462; discovery of arrowhead under bison skeletons at Twelve-mile Creek, 463, 464; Twelve- mile Creek fauna, 464. 48, 49; 159; 635 Wind River formation, 128-135; correlation, 42, 114; location, 86, 87; sections, 123, 131, 154; photograph, 130. Wisconsin glacial, 435, 444, 445; European correlation, 379. WOLpDRICH, succession of faunas in Pleistocene, 388, 414, 415; herbivores reflect changes of environment, 424. Wolf, first occurrence in Europe, 317 ; Siwalik, 327; mid-Pleistocene, Europe, 407; cave, 424; post-Pleistocene, Europe, 429, Woopwarkp, A.&., deposition of Pikermi beds, 268; Con- cud, 270. Woolly rhinoceros, see Diceros antiquitatis. Woolwich Beds, 102, 114. WoORTMAN, succession of mammals in White River formation, 52; north polar origin of mammals, 66, 67 ; Ganodonta (= Tzenio- donta), 107; 109; Wind River, and Huerfano exploration, 129, 130, 134; Leptarctus, 301. Wortmania, 540.* Wirm Glaciation, 378 ; flora, 388. Wiirzburg loess deposits, 418, 426; location and correlation, 391, 413. Xenotherium, 520.* Xiphodon, 548.* Xiphodontherium, 548.* Xiphodontine, 146, 147, 548.* Yarmouth Interglacial, 444, 445, 446. Ypresian stage, 115, 116, 117, 118; correlation, 42, 83, 114; map of localities, 102. Yukon silts, 490. Zapus, 470, 538.* Zeuglodon, 171, 172, 200; zone, of United States, 170, 171, 172; of Fayfiim, 199, 200; beds, 170, 171; restoration, 171; 561.* Zeuglodontia, 73, 559.* Zoogeographic divisions, of Sclater, 35, 36; of Wallace, 35; of Huxley, 36; accepted at present, 36, 37, 38. * Reference to classification. From the Greeks to Darwin An Outline of the Development of the Evolution Idea By HENRY FAIRFIELD OSBORN, LL.D., D.Sc. Da COSTA PROFESSOR OF ZOOLOGY, COLUMBIA UNIVERSITY Second Edition Cloth Svo 250 pages $2.00 net The Initial Volume of the ‘‘ Columbia University Biological Series ”’ The Anticipation and Interpretation of Nature.— Among the Greeks. — The Theologians and the Natural Philosophers. — The Evolutionists of the Eighteenth Century. — From La- marck to St. Hilaire. — Darwin. — Index. “This is an attempt to determine the history of Evolution, its devel- opment and that of its elements, and the indebtedness of modern to earlier investigators. The book is a valuable contribution ; it will do a great deal of good in disseminating more accurate ideas of the ac- complishments of the present as compared with the past, and in broad- ening the views of such as have confined themselves too closely to the recent or to specialties. . . . Asa whole the book is admirable. 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THE MACMILLAN COMPANY Publishers, 64-66 Fifth Avenue, New York S8103—1 Evolution of Mammalian Molar Teeth To and from the Triangular Type Including collected and revised researches on trituberculy and new sections on the forms and homologies of the molar teeth in the different orders of mammals By HENRY FAIRFIELD OSBORN, Sc.D., LL.D., D.Sc. Da Costa Professor of Zoilogy in Columbia University Curator of Vertebrate Palzeontology in the American Museum of Natural Histor $) y, EDITED BY W. K. GREGORY, M.A. Lecturer in Zodlogy in Columbia University Cloth 8vo ix+250 pages Illustrated $2.00 net “The author has succeeded in placing trituberculism on a much more secure and unassailable basis than it ever previously occupied.” — Nature. “The whole book gives evidence of the most painstaking work. Perhaps its most delightful feature is the judicial fairness and frankness with which the whole evidence is reviewed and discussed.” — Sczence. 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