SOCIETAS PRO FAUNA ET FLORA FE.NNICA SOCIETAS PRO FAUNA ET FLORA FENNICA ACTA ZOOLOGICA FENNICA 108 Bjom Kurten: The evolution of the Polar Bear, U rsus maritimus Phipps p- ) A. ~NA ET • .P A .fJl!N'NICA_ HELSINKI-HELSINGFORS 1964 ACTA ZOOLOGICA FENNICA 1-45 vide Acta Zoologica Fennica 45-50. 46-59 vide Acta Zoologica Fennica 60-93. 60. Alex. Luther: Untersuchungen an rhahdocoelen Turbellarien. IX. Zur Kenntnis einiger Typhloplaniden. X. "Ober Astrotorhynchus bifidus (M'Int). 42 S. (1950). 61. T. H. Jilrri: Die Kleinmarlinenbestiinde in ihren Beziehungen zu der Umwelt (Coregonus albula L.). 116 S. (1950). 62. Pontus Palmgren: Die Spinnenfauna Finnlands und Ostfennoskandiens. Ill. Xysticidae und Philodromidae. 43 S. (1950). 63. Sven Nordberg: Researches on the bird fauna of the marine zone in the Aland Archipelago. 62 pp. (1950). 64. Floriano Papil "Ober einige Typhloplaninen (Turbellaria neorhabdocoela). 20 S. (1951). 65. Einari Merikallio: On the numbers of land-birds in Finland. 16 pp. (1951). 66. K. 0. Donner: The visual acuity of some Passerine birds. 40 pp. (1951). 67. Lars von Haartman: Der Trauerfliegenschniipper. II. Populationsprobleme. 60S. (1951). 68. Erie Fabrieius: Zur Ethologie junger Anatiden. 178 S. (1951). 69. Tor G. Karling: Studien iiber Kalyptorhynchien (Turbellaria). IV. Einige Euka­ lyptorhynchia. 49 S. (1952). 70. L. Benick t: Pilzkiifer und Kliferpilze. Okologische und statistische Untersuchun­ gen. 250 S. (1952). 71. Bo-Jungar Wikgren: Osmotic regulation in some aquatic animals with special reference to the influence of temperature. 102 pp. (1953). 72. Wollram Noodt: Entromostracen aus dem Litoral und dem Kiistengrundwasser des Finnischen Meerbusens. 12 S. (1953). 73. Sebastian A. Gerlach: Die Nematodenfauna der Uferzonen und des Kiistengrund­ wassers am Finnischen Meerbusen. 32 S. (1953). 74. T. H. Jiirvi: "Ober den Marlinenbestand irn Pyhiijiini (SW-Finnland). Zweiter Beitrag: Die Jahre 1940-1945. 47 S. (1953). 75. T. H. Jirvi: "Ober die Coregonen s.str. irn Piiijiinne und in einigen anderen Gewlis­ sern Mittelfinnlands. 33 S. (1953). 76. Bjorn Kurten: On the variation and population dynamics of fossil and recent mammal populations. 122 pp. (1953). 77. Goran Bergman: Verhalten und Biologic der Raubseeschwalbe (Hydroprogne tschegrava). 50 S. (1953). 78. Floriano Papi: Beitriige zur Kenntnis der Macrostomiden (Turbellarien). 32 S. (1953). 79. Waiter Hackman: The spiders of Newfoundland. 99 pp. (1954). 80. Karl Schmolzer: Beitrag zur Kenntnis der Gattung Armadillidium Latr. 1804 (Isopoda terrestria). 63 S. (1954). 81. Peter Ax: Die Turbellarienfauna des Kiistengrundwassers am Finnischen 1\Ieer­ busen. 54 S. (1954). 82. Harry Krogerus: Investigations on the Lepidoptera of Newfoundland. I. Macro­ lepidoptera. 80 pp. (1954). 83. Lars von Haartman: Der Trauerfliegenschniipper. Ill. Die 1'\ahrungsbiologie. 96 S. (1954). ACTA ZOOLOGICA FE ICA 108 EDIDIT SOCIETAS PRO FA A ET FLORA FE ICA THE EVOLUTION OF THE POLAR BEAR, URSUS MARITIMUS PHIPPS BY BJORN KURTEN I NSTITUTE OF ZOOLOGY A ' D 1:'\STITUTE OF GEOLOGY A D PALEONTOLOGY OF THE UNIVERSITY, IIELSI NGFORS SO~TAS PRO f'AT. A ET FLO! A FENN:CI\. HEL I r KI-HEL I GFOR 1964 Acta zool. fenn. 108. 30 pp. Dec. 1964 HELSINKI- HELSINGFORS PRINTED BY TILGMANN 1964 Contents Xntroduction 3 Abbreviations.. ........ .... ....... ...... ........ ....... .. ....... .......................... .. .......... .... 4 Subfossil finds of the Polar Bear (Ursus maritimus maritimus Phipps) ..... ........... .. 5 Two sub fossil Polar Bear skulls from Sweden . 6 Subfossil Polar Bear remains from Uddevalla . 9 Pleistocene finds of the Polar Bear (Ursus maritimus tyrannus, new subspecies) .. 9 Description . 9 :vrorphological comparison . ........ ...... ... 11 Numerical comparison . ............ ....... ... .... .................... .... ...... .. ... .... 11 Differentiation in size . 1 r, Geological age of the Polar Bear from Kew . 16 The Ancestry of the Polar Bear . .......... ... ... 16 Reduction of the second upper molar . .. .. .. 16 Allometric growth patterns in the Polar Bear skull . 1 8 Allometry comparisons and the age of the Polar Bear... ... .......... .................... 24. Summary ............... .... ......................... ............ ... ....... .............................. 25 References . ... .. .......................... 26 Plates .. .. .... .. ... ....... ... ...... .. .. .. ... ...... .. .. ..... ... ...... ....... 27 Introduction Fossil remains of the Polar Bear, Ursus maritimus Phipps, are very scarce. Why this should be so is not altogether clear. I n the beach deposits within its present range, for instance at Spitzbergen, Polar Bear bones of recent or sub­ recent age are certainly quite common. There is now good evidence that the Polar Bear existed in Europe during the last glaciation; of course, the beach deposits from that stage are now located below sea level in most areas. Re­ corded finds come mostly from regions of postglacial uplift, and date from the glacial retreat stages. The purpose of the present paper is to add some new information on the fossil occurrence of the species. One of the specimens described is a fossil of undoubted Pleistocene age, typifying a new subspecies of Ursus maritimus. This shows that the Polar Bear, like many other mammals, has decreased in size since Pleistocene times. Apart from this, the fossil and subfossil finds give little information on the descent of the species, although there is a suggestion that some of the maritimus characters in the dentition may be of rather recent origin. 4 Bjorn f(Ltrten: The evolution of the Polar Bear, Ursus m aritimus Phipp:; The dentition of the Polar Bear reflects the carniyorous habits of the species and diverges from the omnivorous dentition of most other ursids. If this is regarded as a primitive character, a long independent history of the species must be postulated. However, the study by T!rnr-.-rus (1953) suggesst that the dental characters of the Polar Bear were acquired at a relatively late date, and that a descent from the Brown Bear stock is probable. Biometric comparison of growth patterns in the Polar Bear skull appear to corroborate this conclusion, as shown in the present paper, and may suggest that Ursus maritimus branched off from the evolving Brown Bear phylum at a fairly late date, perhaps during the Middle Pleistocene. I wish to record my sincere gratitude to Dr. JoHAJ.";.."ES LEPIKSAAR, Gote­ borg, who kindly and generously supplied help and information, and per­ mitted me to place on record a number of subfossil Polar Bear finds. I also gratefully acknowledge the invaluable aid and information given by Dr. A. J. SuTCLIFFE, London. The most important recent comparative material available to me has been the large collection of Ursus maritimus from Greenland in the Zoological Museum of the University of Copenhagen, in the care of Dr. BRAESTRUP. Additional specimens have been studied at the Vertebrate Department of Naturhistoriska Riksmuseet, Stockholm, headed by Dr. A. JOHNELS, and the Zoological Institute of Uppsala University, Custodian Dr. A. HOLM. The help and many courtesies extended to me in this connexion 1s hereby gratefully acknowledged. Abbreviations The following abbreviations have been Abbreviations used in t ables of used to identify collections: measurements: B.M., British Museum (Natural History), a, approximate. London. d, a difference. C.N., Copenhagen Museum of Zoology e, estimated. H.G.M., Geological Museum, Univer ity k, coefficient of allometry. of Helsinki/Helsingfors. 1\I, mean. H.Z.M., Zoological Museum, University , number of specimens. of Helsinki/Helsingfors. O.R., obsen-ed range of variation. L.A.C.M., Los Angeles County Museum. P, probability. N.H.M.G., Natural History Museum, r, coefficient of correlation. G1iteborg. S.D., standard deviation. N .R .M., Naturhistoriska Riksmuseet, Syx. standard deviation of regression Stockholm. of y on x. U.C. , University of California. t, tudent's t . U.Z.I., Zoological Institute, University V, coefficient of variation. of Uppsala. ACTA ZOOLOGICA FE).""NICA 108 5 Subfossil finds of the P ol ar Bear ( U rsus maritim us maritim us Phipps) At least t wo subfossil finds of the Polar Bear have been described pre­ viously, one from Denmark and one from southern Sweden. 1. The Danish specimen (NORDMANN and DEGERB0L, 1930) is from Asdal, north of Hjeming, on the northern tip of Jutland. It was found in a secondary deposit, but may apparently be referred to the Late-Glacial. It is a left ramus of large dimensions, matched only by the largest recent specimens. The cheek teeth are also large, though not outside the observed range of variation of the living form. 2. The Swedish specimen (HOLST, 1902) comes from varved clay under­ lying peat at Kullaberg, Scania, and thus is of approximately the same age as the Danish one. It is a right femur. The dimensions of this specimen (mea­ sured from a cast in the Zoological Institute of Uppsala University) are given in table 1. Except for some wear of the greater trochanter, the specimen appears to be well preserved. It was found as early as 1852, but was not correctly TABLE 1. J"H easurements of bear femora. H ead Shaft I,ength Distal Diameter Width Wirlth Ursus maritimus Subfossil, Kullaberg 496 61 44.7 109 U.Z.I. 3 er 507 65 42 107 N.R.M. Novaya Zembla er 477 60.6 44.2 109 .R .M. tPolar Exp.t er 476 58 41.9 99 C.N. 1465 Greenland er 44 1 6 1 37.7 104 C.N. 2613 Scoresby Sound er 4 18 53.4 33.0 91 C.N. 580 Greenland er 405 59 3lt.l 103 N.R.:\L ~ 403 52.1 33.2 90 c. 1 965 Scoresby Sound ~ 385 50.6 29.6 85 .R . M. kansen Zoo ~ 379 50.0 31.5 84 U rsus spelaetts N.R.M: Jerzmanovice er 466 62.5 48.3 11 3 Coli. Koby St -Brais II er t 443 59.5 52.4 109 Ursus arctos U.Z.I. Lapland 1859 383 45.2 29.2 78 Subfos il, Kams Mose, Denmark1 450 56 38.0 93 1 Private collection of Dr. F.-En. KOBY, Base!. 2 From DEGERBOL, 1933. 6 Bjorn K urfht : The evolution of the Polar Bear, Ursus maritimus Phipps identified until H OLST made his study (op.cit .) of the Swedish subfossil bears.