7

PREFACE

The first International Symposium on the Biology papers were read by title and are included either in of the Seal was held at the University of Guelph, On­ full or abstract form in this volume. The 139 particip­ tario, Canada from 13 to 17 August 1972. The sym­ ants represented 16 countries, permitting scientific posium developed from discussions originating in Dub­ interchange of a truly international nature. lin in 1969 at the meeting of the Marine Mammals In his opening address, V. B. Scheffer suggested that Committee of the International Council for the Ex­ a dream was becoming a reality with a meeting of ploration of the Sea (ICES). The culmination of such a large group of pinniped biologists. This he felt three years’ organization resulted in the first interna­ was very relevant at a time when the relationship of tional meeting, and this volume. The president of ICES marine mammals and man was being closely examined Professor W. Cieglewicz, offered admirable support as on biological, political and ethical grounds. well as honouring the participants by attending the The scientific session commenced with a seven paper symposium. section on evolution chaired by E. D. Mitchell which The programme committee was composed of experts showed the origins and subsequent development of representing the major international sponsors. W. N. this amphibious group of higher vertebrates. Many of Bonner, Head, Seals Research Division, Institute for the arguments for particular evolutionary trends are Marine Environmental Research (IMER), represented speculative in nature and different interpretations can ICES; A. W. Mansfield, Director, Arctic Biological be attached to the same fossil material. Readers of this Station, Fisheries Research Board of Canada (FRB) volume should be aware of such differences when read­ represented the International Commission for North­ ing the papers in this section. The twelve papers of west Atlantic Fisheries (ICNAF); and K. S. Norris, S. H. Ridgway’s section on functional anatomy illus­ Director, Marine Mammal Council Executive Com­ trated the fundamental structure of the seal, as well mittee, represented the International Biological Pro­ as its associated control mechanisms. R. J. Schusterman gram (IBP). The Food and Agriculture Organization followed this theme by introducing ten papers on be­ of the United Nations (FAO) also offered its support haviour. He established a major focus on social or­ to the programme and ICNAF has contributed to the ganization and communication and their association financing of this volume. with the functional anatomy of the pinnipeds. D. E. Sponsors of national origin were the Fisheries Re­ Sergeant chaired the population dynamics section of search Board of Canada (FRB), the National Re­ seven papers, covering the modelling of populations search Council of Canada (NRCC), the Canadian and method of analysis of seal populations around the National Sportsmen’s Show (CNSS), the World Wild­ world. In the fifth section, J. R. Geraci, by means of life Fund (Canada) (WWF), and the University of papers and a panel discussion dealt with the care and Guelph. management of captive pinnipeds. W. N. Bonner co­ In his preliminary remarks Professor Ronald intro­ ordinated a presentation in the broad area of ecology, duced the representatives of these groups; namely J. R. and was able to bring together studies on environmen­ Weir, Chairman, Fisheries Research Board of Canada; tal factors and their associated behavioural and gene­ S. Bata, International Director and J. S. McCormack, tic control systems. The physiology section was chaired Director, World Wildlife Fund (Canada); and R. T. by H. T. Andersen, his introductory remarks forming D. Birchall, President, Canadian National Sportsmen’s the initial paper of the section. The other six papers Show and a Director of WWF (Canada). of his section emphasized the underwater responses of W. C. Winegard, President of the University of seals. The final and general section, chaired by J. E. Guelph, welcomed participants to the symposium and King, offered a broad coverage of several of the more commented particularly on how pleased he was to interesting areas in various disciplines. welcome representatives from so many countries. Later, A. W. Mansfield acted as rapporteur for the entire at a banquet sponsored by the Department of the En­ programme, and his report stressed the need for con­ vironment, Canada, he offered an invitation to the tinued cooperation by all biologists so that they might group to return in 1975 for a Second International understand seals and their importance to environmen­ Seal Symposium. tal studies. Altogether 62 papers were presented. A further 14 This volume includes with one exception, those pa- 8 K. Ronald pers either presented, read by title, or abstracted, but mammals of the world’ by D. W. Rice and V. B. the continuing discussion on the biology of the seals Scheffer (U.S. Fish and Wildlife Service, Washing­ led to one further paper that is included here. Some ton, 1968) has been used as the standard reference on of the discussion was formal and, where recordable, is nomenclature. included here, but by far the greater part of discussion The work of the chairmen of each of the seven sec­ was informal and hence must remain as extremely tions of this volume is especially recognized. As well, valuable, but merely mental recollections of the par­ the convenor wishes to thank the programme com­ ticipants in the symposium. mittee for their ability to support a somewhat unortho­ The symposium achieved its purpose of bringing dox procedural system, and particularly the sponsors together scientists interested in the Pinnipedia and it ICES, ICNAF, IBP, CNSS, FRB, NRCC, WWF (Ca­ offered leads into the international examination of nada), FAO, and the University of Guelph for their marine mammals. valuable financial assistance. The editors with little apology recognized that they The convenor is most grateful to Mr. H. Tambs- have not reached a completely uniform format in this Lyche, General Secretary of ICES, for his advice and volume since they have allowed use of both English encouragement from the embryonic stages of the sym­ and metric systems of measurement and both English posium to the publication of the proceedings; he also and North American word usage for the sake of har­ recognizes the considerable amount of expert help pro­ mony. The main editorial structure has been the con­ vided by A. W. Mansfield in co-editing this volume. sistency of usage throughout a particular paper. Finally, the effort put into both the symposium and Attempts have also been made to attain a fairly this volume by Mrs. Ginny Bandesen has been beyond uniform taxonomy for the species, but where there has measure, but I hope that she will accept the results of been any doubt caution has not overridden clarity. As the symposium recorded here as tangible proof of her in other mammalian groups, the systematics of the most valuable contribution. To the members of the Pinnipedia are still open to much interpretation. The Dean of the College of Biological Science’s office, the references are cited according to an Annotated Biblio- university support staff and our host Dr. W. C. Wine- praphy on the Pinnipedia*. The ‘List of the marine gard, I express on behalf of the participants and my­ self, our sincerest thanks. * Ronald, K., L. M. Hanly and P. J. Healey, College of Bio­ K. Ronald, logical Science, University of Guelph, Ontario, Canada. Convenor

The following have kindly acted as Discussion Care and Management Section Leaders of the different Sections and also assisted in J. R. Geraci the editing of the contributions: Department of Zoology, University of Guelph, Guelph, Ontario, Canada. Evolution Section E. D. Mitchell Ecology Section Arctic Biological Station, Fisheries Research Board W. N. Bonner of Canada, Ste. Anne de Bellevue, Quebec, Canada. Seals Research Division IMER, c/o Fisheries Labora­ tories, Lowestoft, Suffolk, England.

Functional Anatomy Section Physiology Section S. H. Ridgway H. T. Andersen School of Anatomy, University of Cambridge, Nutrition Institute, University of Oslo, Blindern, Cambridge, England. Oslo, Norway.

Behaviour Section General Session R. J. Schusterman J. E. King Department of Psychology, California State University Department of Zoology, University of New South Hayward, California 94542, U.S.A. Wales, Kensington, N.S.W., Australia.

Population Dynamics Section Summary D. E. Sergeant A. W. Mansfield (Rapporteur) Arctic Biological Station, Fisheries Research Board of Arctic Biological Station, Fisheries Research Board Canada, Ste. Anne de Bellevue, Quebec, Canada. of Canada, Ste. Anne de Bellevue, Quebec, Canada. 49

Rapp. p.-v. Réun. Cons. int. Explor. Mer, 169: 49-56. 1975.

A PHYLOGENY OF OTARIID SEALS BASED ON MORPHOLOGY OF THE BACULUM

G. V. M o r e j o h n Moss Landing Marine Laboratories, California State University, Moss Landing, California, 95039 U.S.A.

INTRODUCTION analysis (Orr et al. 1970); or cranial measurements. The importance of the baculum in demonstrating Some bacula used had no skulls available for study and species affinities among mammalian groups has been only comparisons with other bacula provided age amply documented in many studies. The diversity in estimates. size and shape as well as ornamentation of the struc­ An index of comparison was developed (H X W j L ture have been well illustrated by Burt (I960) for = index) in order to demonstrate intergeneric affin­ North American mammals. An earlier study by Chaine ities. The measurements taken were: length (L) of (1925) showed bacula of many worldwide mammalian baculum, greatest height (H) and greatest width ( W) species. The bacula of the pinnipedia in general have of bacular apex and four other areas of the shaft not been used to determine relationships within or (Fig. 18). between the two major phyletic groups, the otarioids The sources of the bacula from museums, institu­ (otariids and odobenids); and the phocoids (phocids). tions, and other agencies and their abbreviations used A study of phylogenetic relationships among the seven in this paper are as follows: Arctic Health Research living genera of otariid seals is, therefore, reported Center, College, Alaska (AHRC) ; California Academy herein based on ontogeny and morphology of the of Sciences, San Francisco, California (CAS); Ca­ baculum. nadian Wildlife Service, Ontario, Canada (CWS); In a recent discussion of the work of Hinde and Marine Mammal Biological Laboratory, Seattle, Wash­ Tinbergen (1958) concerning the phyletic method of ington (MMBL) ; Marine Science Center, Newport, inferring behavioral evolution based on morphology, Oregon (M SC); Museum of Vertebrate Zoology, Bartholomew (1970) stated that “postulation of University of California, Berkeley, California (MVZ) ; relationships based on living genera and species is rarely rewarding, and phyletic lines based on fossil pinnipeds are too limited to be of much use.” The present study, therefore, mainly concerned with bacula of extant otariids, also considers fossil bacula of otariid seals and represents a contribution that provides an adequate basis for the use of the phyletic method of Hinde and Tinbergen (1958) in comparative etholog- W ical studies of the species of Otariidae. L

MATERIALS AND METHODS A total of 78 bacula representing the genera Arctocephalus, Callorhinus, Zalophus, Neophoca, Phocarctos, and Eumetopias were examined and measured (Table 3). Most specimens were from adults, some were from subadults; for the genera Callorhinus, Zalophus, and Eumetopias a nearly comp­ lete developmental series from newborn young or pup through aged adult were studied. Approximations of Figure 18. Drawing (above) of lateral view of a typical otariid age classes were made by either one or more of three baculum showing areas of measurement. The vertical lines along the shaft represent points of measure of height and width. Drawing methods: dentinal layers (Scheffer, 1950a); sutural (below) of baculum of (top) and Eumetopias (below).

4 G. V. Morejohn

Oregon Institute of Marine Biology (OIMB) ; Natio- Table 3. A list of baculum specimens studied of 6 nal Museum of Natural History, Washington, D.C. genera of otariids (NMNH) ; and U .S. Geological Survey, Branch of Paleontology and Stratigraphy, Menlo Park, Califor­ Apex nia (USGS). Specimen Length Height Width H • W Estimated number (L) (H) (W) L age

DESCRIPTION AND RESULTS Zalophus R. Jones - 1 128-0 17-0 5-8 0-770 - The baculum of the adult California sea lion, M VZ 4124 128-0 16-0 5-0 0-624 - Zalophus californianus, was described and illustrated MVZ 89500 133-5 15-0 7-5 0-832 - by Burt ( 1960 ). The measurements given and descrip­ M VZ 112387 113-0 14-0 6-0 0-743 - tion of distal end or apex fit the measurements and M VZ 125498 115-0 14-0 4-6 0-646 - CAS 416 128-0 17-0 6-0 0-797 - description of the baculum of the adult Steller sea CAS 12865 124-0 17-0 6-0 0-823 - lion, Eumetopias jubata. Burt stated (1960) that the CAS 12876 127-0 18-0 7-0 0-999 14 .. -“distal end is expanded into a roughly circular USGS - REP 123-0 4-2 7-8 0-265 - disc.” This accurately describes the bacular apex of MSC-1 125-0 15-0 7-5 0-900 - M LM L-4 (a) 111-5 15-0 6-0 0-807 4 adult Eumetopias but not that of Zalophus. The long­ MLML-9 119-0 19-6 6-3 1-037 9 est bone specimen in our sample of adult Eumetopias MLML-12 118-0 14-2 4-2 0-505 8 is 192 mm. The longest bone specimen in our sample MLML-13 58-3 4-0 4-0 0-274 1 of adult Zalophus is 137 mm. The bone illustrated by MLML-14 118-8 16-2 4-0 0-596 5 MLML-15 108-0 16-8 5-5 0-855 3 Burt is 176 mm in length. It is thus obvious that a MLML-17 113-4 12-2 5-2 0-559 4 redescription of the baculum of Z. calif ornianus is in MLML-18 69-2 5-2 5-0 0-376 2 order. MLML-19 119-5 13-3 4-0 0-445 5 Mitchell (1966) described the baculum of the fossil MLML-23 134-0 16-5 5-2 0-640 10 MLML-24 102-5 12-0 6-0 0-702 3 otariid Allodesmus and was the first to note the mis- MLML-26 56-0 3-0 2-0 0-115 1 identification of the bone by Burt. The bone figured MLML-28 72-0 5-0 5-5 0-381 1 by Burt was received from N. H. Spalding with no GVM-6 95-0 11-0 5-0 0-578 — collection data or locality indicated (E. T. Hooper, GVM-7 126-0 15-0 9-0 1-071 - GVM-8 114-0 11-0 7-0 0-675 6 personal communication). GVM-9 136-0 17-0 5-6 0-700 - In lateral aspect the baculum of adult Zalophus GVM-10 123-0 18-0 7-0 1-024 - may be characterized by the presence of a dorsal and GVM-11 120-0 16-0 5-0 0-666 — ventral knob at the anterior end (see Fig. 18 for fol­ GVM-12 123-8 16-2 8-0 1-047 - GVM-13 120-0 16-2 7-5 1-012 8 lowing description). The ventral knob may extend GVM-14 48-0 3-0 2-0 0-125 1 forward or be even with the dorsal knob. A median GVM-15 125-5 15-0 9-0 1-076 - ridge is evident dorsally on the proximal 1/3 to 1/4 GVM-16 117-0 7-2 5-0 0-307 3 of the shaft. In this area the shaft is roughly triangular GVM-17 86-3 10-6 4-0 0-491 2 GVM-18 114-2 14-2 4-0 0-497 4 in cross section. The ridge loses its distinctness as the GVM-19 104-0 14-0 5-0 0-673 3 shaft tapers on all sides distally such that the cross GVM-20 69-0 5-0 4-0 0-289 1 sectional configuration becomes somewhat circular GVM-21 86-0 7-0 5-0 0-406 2 with a slightly flattened ventral surface. Near the apex GVM-22 125-0 17-0 5-0 0-680 8 GVM-23 108-0 9-0 4-0 0-333 3 or distal end a cross section is oval. Most specimens GVM-24 114-0 16-0 4-0 0-561 4 have a slight dorsal curvature of the shaft. In these, GVM-25 59-0 4-0 4-0 0-271 1 in ventral aspect, the urethral groove is markedly visible in the proximal end, and as indicated above, Arctocephalus 3-3 0-392 - this area is somewhat triangular in cross section. In USGS-6920 111-0 13-2 USGS-7120 90-8 10-0 5-1 0-562 - those specimens which lack the dorsal curvature (and USGS-7121 104-0 10-0 3-0 0-288 — thus have a straight shaft), the cross sectional con­ figuration of the proximal end does not have well Callorhinus 2-0 0-160 pup developed ventrolateral edges that form the distinctive MMBL-307 25-0 2-0 MMBL-22 49-0 2-0 1-5 0-061 1 urethral groove in other specimens. MMBL-A9198 57-2 4-3 2-3 0-173 2 In the developmental series of bacula of Zalophus MMBL-2821 66-8 4-5 2-2 0-148 3 from less than a year of age to animals that are sub­ MMBL-20521 98-0 8-0 2-5 0-204 4 6-5 2-2 0-151 5 adult (ca. 4 years old), but essentially fully developed, MMBL-114(a) 95-0 the ventral knob is produced first in most specimens. fa) Ventral knob broken. Measure of length of shaft and height The dorsal knob usually becomes evident in the two- of apex may be 2-3 mm off. A phylogeny of Otariid seals based on morphology of the baculum 51

Table 3 (continued) 1401

Apex 120 Zalophus - - - J 1» Specimen Length Height W idth H ■ W Estimated (5L>_- Number (£) (*0 m L age 100

Callorhinus 80 MMBL-196 107-0 9-5 3-0 0-266 6 ( 6 ) MMBL-251 113-0 13-0 4-0 0-460 7 Callorhinus MMBL-253 112-0 13-0 4-0 0-460 7 60 MMBL-303 123-0 14-0 6-0 0-680 8 Z> GVM-25 98-0 8-6 2-7 0-237 4 =) 40 Neophoca USGS-7111 61-0 5-0 1-6 0-131 _ 20 CWS-1 137-0 16-0 12-0 1-400 _ CWS-2 129-0 11-5 8-5 0-757 ' “ I 1 i f ------1 i CWS-3 114-0 11-2 6-0 0-589 CVVS-4 123-0 15-0 9-0 1-098 _ 23456789 CWS-5 124-0 16-0 10-0 1-290 _ CWS-6 108-0 12-0 6-2 0-688 _ AGE (yrs) CWS-7 131-0 16-0 9-0 1-099 _ Figure 19. Comparison in growth of baculum of two genera of CWS-8 109-0 11-5 8-5 _ 0-896 otariids. The data for Callorhinus are from Scheffer (1950b). Age CWS-9 117-0 14-0 6-0 0-717 - and growth of bacula in Callorhinus appear to be proportional. Phocarctos The bacula of 3—4 year old Zalophus are essentially fully developed. Longer bacula of Zalophus (Table 3, MVZ-89500, MLML-23, USGS-7100 170-0 15-0 12-0 1-06 - GVM-12) had no skulls for ageing or age was not determined. Eumetopias MLML-201 192-0 27-0 24-0 3-375 20 MLML-202 181-0 22-0 25-0 3-039 cephalus and Callorhinus (Scheffer, 1950b) are very7 AHRC-23803 192-0 22-0 18-5 2-119 _• similar to Zalophus. They have the dorsal and ventral MMBL-SS39 175-0 19-0 16-0 1-737 5 MMBL-SS27 169-0 22-0 17-0 2-213 8 knobs of the apex well developed and in lateral view OIMB-1 174-0 22-0 19-0 2-402 the ventral knob is also in advance of the dorsal knob- NMNH-270969 141-0 11-0 5-2 0-405 The dorsal knob does not develop as prominent a M M BL-SS13 109-0 7-5 5-0 0-344 3 projection from the apex in Arctocephalus as it does MMBL-SS2 67-0 6-2 5-3 0-490 1 in Callorhinus. The ventral knob in Callorhinus ex­ MLML-LT 115-0 11-5 6-5 0-650 - pands laterally with age, and from an anterior view of some adults an obvious “figure of eight” is visible year-old class. Height of the bacular apex grows pro­ (Fig. 20). There is some variation in the size of this portionately much faster than width. The bacula of knob in Callorhinus and Zalophus, and the small mature breeding bulls (7 years or older) are more sample size of Arctocephalus bacula studied may not massive but not necessarily longer than those of sub­ have been representative of the variation of this adult males (Table 3). The length of the baculum character. The shafts of both fur seals are slimmer, in relation to age apparently is a linear function in mostly oval in cross section throughout the length in Callorhinus (Scheffer 1950b). Rapid growth of the Arctocephalus; but markedly triangular in cross sec­ baculum is evident from one to three years of age in tion throughout most of the length in Callorhinus. Zalophus, after which time, however, the growth in The proximal end of the baculum of both fur seals length diminishes and tends to cease at about four to is not as massive as in Zalophus. The most marked five years of age (Fig. 19). difference between Zalophus and the fur seals is in With increased age, small osseous knobs may the narrowness of the bacular apex. The smaller develop along the lateral edges of the apex, along the measurement obtained for the width of the apex median dorsal ridge, and along the ventrolateral edges largely contributes to the difference in index values of the urethral groove. The proximal, or basal end, in (Table 4) between Zalophus and the two genera of the region of the tendinous attachment also becomes fur seals. Otherwise the baculum of Arctocephalus much more rugose with advanced age. The bacula of may be said to be a slimmer version of that of Phocarctos and Eumetopias both possess a keel ventral Zalophus. to the apex. Some specimens of Zalophus and Neo­ Although some authors (Sivertsen, 1954; Scheffer, phoca also possess a small keel. Keels are not found 1958) have considered Neophoca and Phocarctos in Callorhinus or Arctocephalus. In general, Arcto- congeneric, King (1960) advanced diagnostic criteria 52 G. V. Morejohn

3mm 4 mm 5m m Table 4. Bacular ratios of apex and shaft used to ------1 plot graph of Figure 25

Shaft area Genus Number Apex 1 2 3 4

Phocarctos USGS-7100 1-06 0-347 0-647 0-841 1-79

Arctocephalus USGS-7121 0-288 0-144 0-346 0-471 0-539 Arctocephalus USGS-6920 0-392 0-265 0-479 0-635 0.811 Means 0-340 0-205 0-413 0-553 0-675

Neophoca CWS-1 1-40 0-281 0-526 0-806 1-688 Neophoca CWS-4 1-098 0-264 0-455 0-636 1-215 Neophoca CWS-5 1-290 0-223 0-439 0-669 1-508 Neophoca CWS-7 1-099 0-159 0-401 0-550 1-031 Means 1-218 0-231 0-455 0-665 1-361

Eumetopias MLML-201 3-375 0-625 0-875 0-948 1-328 Eumetopias MLML-202 3-039 0-597 0-862 1-006 1-994 Means 3-207 0-611 0-868 0-977 1-661

Callorhinus MMBL-251 0-46 0-139 0-258 0-420 0-925 Callorhinus MMBL-252 0-46 0-134 0-224 0-348 0-670 Callorhinus MMBL-303 0-68 0-226 0-386 0-587 1-141 Means 0-53 0-166 0-289 0-451 0-912

Zalophus MLML-9 1-04 0-303 0-378 0-924 0-832 Zalophus GVM-22 0-605 0-294 0-548 0-927 1-677 Zalophus GVM-24 0-639 0-263 0-474 0-913 2-162 Zalophus MSC-1 0-900 0-308 0-504 0-760 1-248 Zalophus GVM-7 1-68 0-264 0-392 0-648 1-056 Zalophus GVM-8 0-819 0-294 0-571 0-924 2-000 Zalophus GVM-9 0-438 0-281 0-383 0-690 1-270 Zalophus GVM-10 0-649 0-393 0-738 1-082 1-951 Zalophus GVM-11 0-667 0-300 0-533 0-980 1-750 Zalophus GVM-12 0-996 0-180 0-403 0-511 1-273 Zalophus GVM-13 0-795 0-162 0-254 0-575 1-235 Means 0-839 0-276 0-470 0-812 1-495 lOmm 10mm Figure 20. Anterior views of apices of adult bacula : Arctocephalus, of 260 mm for a baculum of Neophoca (— Phocarc­ USGS-7121, (upper left) ; Callorhinus, MMBL-303, (upper middle) ; tos) hookeri. The original source of this datum is Zalophus, GVM-10, (upper right); Neophoca, CWS-1, (bottom left); and Phocarctos, USGS-7100, (bottom right). Compare Pho­ Chaine (1925). The measurement given by Chaine is carctos with subadult Eumetopias of Figure 22. 26. The unit of measure (in millimeters) is noted in a footnote on p. 11. Based now on the correct mea­ to maintain Neophoca and Phocarctos as separate surement of 26 mm and the morphology of the bone genera. My comparison of the skulls (Neophoca USGS as seen in the drawing (Chaine 1925), the bone must 7111; Phocarctos USGS 7100) and bacula of these have come from a young pup and not an adult as genera provide overwhelming support to King’s cont­ Scheffer and Kneyon assumed. entions. I have studied 11 bacula of Neophoca, 1 im­ The bacula of subadult Neophoca in lateral view mature (USGS 7111), 6 subadults and 4 adults and resemble Zalophus subadults. Dorsal and ventral knobs compared them with an adult baculum of Phocarctos are clearly evident. An anterior view of the apex of (USGS 7100). The adult Phocarctos is approximately an adult Neophoca (Fig. 20) resembles an immature 33 mm longer than the longest adult Neophoca (see or subadult in the developmental series of Eumetopias. measurements Table 3). The differences in details Lateral expansion on the upper edges of the apex of the apex of the baculum of Phocarctos together clearly serve to separate it from both genera of fur with the overall size of the structure merit generic seals and Zalophus. The baculum of Phocarctos is distinction solely on this basis. also more similar to a subadult Eumetopias than to Scheffer and Kenyon (1963) gave the total length Zalophus (Figs. 20, 21 and 22). Phocarctos also has A phytogeny of Otariid seals based on morphology of the baculum 53

10mm 10mm —I i------1

A B Figure 21. Anterior views of apices of Eumetopias bacula : subadult, DIMB-1 (A) and adult, MLML-201 (B). Note similarity of the subadult (A) with the adult Phocarctos in Figure 22. The ventral keel seen in A is obliterated with age in B and the apex becomes circular. Figure 23. Photo of baculum of Cedros Island fossil (UGR-1321). The ventral knob is bulbous; the dorsal knob is weakly developed. Drawing of apex shows median ridge connecting dorsal and ventral knobs. Cross sectional configuration of the shaft shows its triangular nature and a proximal end wider than high. Arrows indicate crushing of sides.

studied, the urethral groove is well marked. The vent­ rolateral edges of the shaft together with a slightly concave ventral surface are well defined. Immediately posterior to the apex, the shaft is very flat from side to side, and in cross section appears as a narrow ellipse. The index values of the bacular apex for the six genera measured were influenced primarily by the width of the bacular apex (Fig. 24) and the widths along the shaft. I have not been able to procure a baculum of Otaria. To my knowledge, the only reference to the bone is found in Murie (1874). He illustrated only an anterior view of the apex and briefly described the apex a s ...... “oval, the long diameter vertical, and the lower end the narrowest part.” He further Figure 22. Bacular apices of Phocarctos (USGS-7100) and Eume­ indicated that the bone is . . . “4 inches long . . . ” (100 topias (OIMB-1): Phocarctos adult (left upper) and Eumetopias mm) and that the proximal end is . . .“the thickest, the subadult (left lower). Note ventral apical keels in both. The keel remainder forwards . . . roundish, and about 0-2 inch of Eumetopias is pointed; that of Phocarctos is rounded. A ventral in diameter.” The animal was thought to be a young view of apex of adult Eumetopias, MLML-201, (right) shows lateral subapical swellings that develop sometime after 4 years adult. In essence, the description of the baculum of of age and are seen in no other genus. Otaria given above closely matches the appearance of the baculum of a subadult Neophoca. A study of the developmental series of Eumetopias expanded lateral edges of the apex but a median disclosed that during growth of the baculum, ventral ventral keel is more prominently demonstrated pro­ and dorsal projections of the apex develop that are portionately than in other genera. Subadult specimens homologous to the knobs of other genera. This devel­ of Eumetopias have well developed mid ventral keels opment is followed by gradual lateral expansion of as well (Fig. 21A). In the specimen of Phocarctos the apex such that in the adult, a circular apex results. 54 G. V. Morejohn

(II) Zalophus (2)------Eumetopias (3 )------Callorhinus (4)...... Neophoca (I) Phocarctos (2 ) Arctocephalus a a Fossil UCR-I32I

H < CE

I/ 5 th BACULAR LENGTH i/5th BACULAR LENGTH Figure 24 Comparative plots of bacular index for 6 genera of otariids. Only bacula from adults were used. The genera on the right were plotted separately for clarity. The horizontal axis may be considered to represent a hypothetical bacular axis. Deviations above and below the line represent specialization, especially of the apex. Compare the extremes seen for Arctocephalus and hume- topias. Data for plots are taken from Table 4.

Lateral expansion of the apex does not take place in knob is small and is connected to the ventral knob by the fur seals or Zalophus. Immature Eumetopias, how­ a thin median ridge coursing on the anterior face of ever, lacking lateral apex expansion, have index values the apex from dorsal knob to ventral knob. A shallow for the apex that fall within those values of other depression is found on each side of this median ridge. genera. Thus it appears that through ontogenetic The shaft throughout most of its length is triangular. changes of the bacular apex to produce a circular The proximal end is wider than high. form, the genera Otaria, Neophoca, Phocarctos and In several traits this fossil baculum is similar to the Eumetopias share similar ontogeny. The closest ap­ baculum of the two genera of fur seals, sharing more proximation to the circular form occurs in adult characteristics with Callorhinus, however, than with Eumetopias (Fig. 21B). Sometime after 4 years of age, Arctocephalus. An apical median ridge was noted in Eumetopias develops subapical lateral swellings found one adult Arctocephalus forsteri (USGS 7120)- The in no other genus (Fig. 22). Arranged in the order bulbous ventral knob of the apex, from anterior view, given above, Eumetopias then may be said to be more resembles a “figure of eight” as in Callorhinus. The specialized in developing a circular apex and sub- broader proximal end and the triangular shape of the apical swellings. The baculum of the adult walrus, shaft are also similar to Callorhinus. The plot of the Odobenus rosmarus, in cross sectional configuration, bacular index clearly falls within the grouping of lateral aspect, and slight expansion of the bacular Arctocephalus and Callorhinus (Fig. 24). apex to form a knob (Murie 1936) is similar to Eumetopias. With permission of C. A. Repenning, I was able to DISCUSSION study a baculum, skull and many post cranial elements Developmentally, Callorhinus and Zalophus are from an undescribed otariid of Pliocene age (UCR similar in formation of narrow, ventral and dorsal 1321) collected by R. H. Tedford from the Aemejas knobs at the apex of the baculum. They show no formation (7-9 million years old) on Cedros Island, marked specialization of the apex to the degree de­ Baja California. This baculum (Fig. 23) is fractured monstrated in Otaria, Neophoca, Phocarctos or Eume­ in several places and has been glued together. It is topias. An ontogenetic sequence of Arctocephalus slightly distorted on the proximal 1 / 8th of the bone. would doubtless resemble a series of Callorhinus, since The right lateral side is crushed in this area. The prox­ as adults they are nearly identical. The major distinc­ imal end viewed dorsally has a peculiar indentation tion between the fur seal genera is seen in lateral not seen in other otariid bacula. The ventral knob of expansion of the ventral knob of Callorhinus and in a the apex is bulbous. There are no discrete edges to the weakly developed trait of the cross sectional configur­ sides of the ventral knob; it is all rounded. The dorsal ation of the shaft, being more triangular in Callorhi- A phylogeny of Otariid seals based on morphology of the baculum 55

nus than oval as in Arctocephalus. In some Callorhinus tween Arctocephalus and Callorhinus, with a weakly bacula the proximal end is broad and flat, a charac­ developed dorsal knob at the apex. The specimen is teristic which the Cedros Island fossil (UCR 1321) obviously an adult considering the length of its bacu­ clearly possesses (Fig. 23). In Arctocephalus the prox­ lum as well as the skull and dentition. The develop­ imal end is only slightly higher than wide, mostly mental series of bacula of Callorhinus, Zalophus, and roundish. Neophoca, Phocarctos, and Zalophus are Eumetopias have clearly shown that the bacula of higher than wide, and Eumetopias is about as wide as these genera all develop from a simple rod which, high (see Table 4, shaft area 4). during growth, increase in length and girth and gradu­ The baculum of Zalophus varies in cross section in ally develops dorsal and ventral knobs as ornament­ being oval and triangular, but is more robust, and the ation of the apex. The ventral knob in subadult Eu­ apices of some individuals (0-9%) possess a weakly metopias is prominent and keel-like; the dorsal knob developed keel not seen in the fur seals. Apex traits not grows laterally and downwards, and in the adult both seen in Zalophus or the fur seals develop in Otaria, ventral and dorsal knobs are united by lateral ex­ Neophoca, and Phocarctos. Lateral expansion of the pansion of the apex to produce a circular form. The apex occurs in all three genera and reaches its greatest baculum of Eumetopias, thus, may be said to be an development in the region of the dorsal knob in Phoc­ example of ontogeny recapitulating phylogeny. Arcto­ arctos. Immature Neophoca are similar to Zalophus cephalus, Callorhinus and Zalophus may, therefore, be in apex morphology and size. Phocarctos largely differs considered closer to an ancestral type of otariid. The from Otaria, Neophoca, and Eumetopias in that in ancestral characteristics of the bacula that these genera lateral view of the apex the ventral knob does not possess, coupled with the derived characteristics of the project anteriorly beyond the dorsal knob. The anter- bacula of Otaria, Neophoca, Phocarctos and Eumeto­ odorsal inclination of the expanded apex (similar in pias, are the characters of phylogenetic importance Neophoca and Eumetopias) thus has an unpointed, which I have used in developing the hypothetical rounded keel (compare with subadult Eumetopias in phylogeny of otariid seals in Figure 25. Thus it may Fig. 22)- Eumetopias differs from all other genera in be stated that Eumetopias represents one end of an developing subapical swellings as a subadult and in evolutionary spectrum and Arctocephalus another. having a circular apex as an adult. The characteristics of the bacula of the seven Eumetopias genera of otariid seals have been shown to be distinct­ ive in several aspects of morphology. The char­ acteristics which I consider of phylogenetic importance Phocarctos are based largely on ontogenetic criteria. A premise, which in an evolutionary sense is considered valid, is to assume that the ancestral carnivore stock that gave W apex: expanded rise to the pinnipedia (as well as many other groups) above keel developed a simple stiffening rod (a baculum) lacking Otaria Neophoca distal apical ornamentation as seen in some generalized carnivores such as bears. This ancestral type of bacu­ lum would taper from a large proximal end gradually Arctocephalus towards the apex. There are few exceptions to this generality among mammals that possess a baculum Zalophus (see Burt 1960; Chaine 1925). Ornamentation of the Callorhinus tip takes place in many forms and may be three pronged in some species. The sea otter (Enhydra lutris) is a mustelid carnivore in this category (More­ john. Baltz, and Roest, 1975). The Miocene Allod- shaft: esmus kernensis, described by Mitchell (1966) pos­ triangular sessed a baculum that had an apex with weakly de­ veloped dorsal and ventral knobs and the ventral knob was wider than the dorsal knob. The point being made here is that the development of dorsal and ventral knobs of the bacular apex was well on the FUR SEAL-SEA LION way sometime during the Miocene. ANCESTOR The Pliocene fossil from Cedros Island (UCR 1321), Figure 25. A hypothetical phylogeny of otariid seals based possesses a baculum morphologically intermediate be­ principally on morphology and ontogeny of the baculum. 56 G. V. Morejohn

ACKNOWLEDGEMENTS Chaine, J. 1926. L’os penien’ étude descriptive et comparative. Actes Soc. Linn. Bordeaux, 78:12—195. I gratefully acknowledge the assistance given me Hinde, R. A. & Tinbergen, N. 1958. The comparative study by the curators, technicians and graduate students of species-specific behavior, pp. 251—268. In Behavior and associated with the mammal collections of the Cali­ Evolution. Ed. by A. Roe and G. G. Simpson. Yale Univ. Press, New Haven. fornia State University, San Jose, California; Uni­ King, J. E. 1960. Sea lions of the genera Neophoca and Phocarctos. versity of California, Museum of Vertebrate Zoology, Mammalia, 24:445-56. Berkeley, California; California Academy of Sciences, Mitchell, E. 1966. The Miocene pinniped Allodesmus. Univ. Calif., San Francisco; U. S. Geolgical Survey, Branch of Publ. Geol. Sei., 61. 105 pp. Paleontology and Stratigraphy, Menlo Park, Califor­ Mitchell, E. 1968. The Mio-Pliocene pinniped Imagotaria. J. Fish. Res. Bd Can., 25:1843-1900. nia; National Museum of Natural History, Washington, Morejohn, G. V., Baltz, D. M. & Roest, A. Growth of the bacu­ D.C.; and the Department of Public Health, Educ­ lum in the sea otter. J. M ammal., 56. (In press.) ation and Welfare, Arctic Health Research Center, Murie, J. 1874. Researches upon the anatomy of the Pinnipedia. Part III. Descriptive anatomy of the sea-lion (Otaria jubata). College, Alaska. I extend my thanks to Joel W. Hedg- Zool. Soc. Lond., Trans., 8:501-82, pi. 75-82. peth for providing a baculum from the Galapagos Is­ Murie, O. J. 1936. Notes on the mammals of St. Lawrence Island, lands Zalophus population, to Bruce Mate and Finn pp. 335-346. In Archaeological investigations at Kukulik, Sandegren for bacula of Eumetopias, and to Ian Stir­ St. Lawrence Island, Alaska. Ed. by O. W. Geist and F. G. Rainey. Univ. Alaska, Misc. Publ., 2. ling for bacula of Neophoca. Ancel Johnson provided Orr, R. T., Schonewald & Kenyon, K. W. 1970. The California specimens of Eumetopias and Callorhinus. Charles sea lion: skull growth and a comparison of two populations. Repenning has assisted me by providing specimens of Calif. Acad. Sei., Proc., Ser. 4, 37:381—94. bacula and skulls as well as helpful comments on the Scheffer, V. B. 1950a. Growth layers on the teeth of Pinnipedia as an indication of age. Science, (New York), 112:309-11. manuscript and discussions relevant to otariid phy­ Scheffer, V. B. 1950b. Growth of the testes and baculum in the logeny throughout this study, and to him I owe a fur seal, Callorhinus ursinus. J. Mammal., 31:384—94. special thanks. Scheffer, V. B. 1958. Seals, sea lions, and walruses. A review of the Pinnipedia. Stanford Univ. Press, Stanford, Calif. 179 pp. Scheffer, V. B. & Kenyon, K. W. 1963. Baculum size in pinnipeds. REFERENCES Z. Saugetierkd., 28:38-41. Bartholomew, G. A. 1970. A model for the evolution of pinniped Sivertsen, E. 1954. A survey of the eared seals (Family Otariidae) polygyny. Evolution, (Lancaster, Pa.), 24:546—59. with remarks on the antarctic seals collected by M/K “Norve­ Burt, W. H. I960. Bacula of North American mammals. Univ. gica” in 1928-1929. Norske Vidensk.-Akad., Oslo, Sei. Results Mich., Mus. Zool., Misc. Publ., 113. 76 pp. Norweg. Antarct. Exped. 1927-1928, 36:1-76.