aquatic adaptations in desmostylians
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Aquatic adaptations in desmostyliansNorihisa Inuzuka aa Department of Cell Biology and Anatomy, Graduate School of Medicine, University ofTokyo, Hongo 7–3–1, Bunkyo‐ku, Tokyo, 113–0033, Japan Phone: 81–3–5841–3334 Fax:81–3–5841–3334Version of record first published: 10 Jan 2009.
To cite this article: Norihisa Inuzuka (2000): Aquatic adaptations in desmostylians, Historical Biology: An InternationalJournal of Paleobiology, 14:1-2, 97-113
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Aquatic Adaptations in DesmostyliansNORIHISA INUZUKA*
Department of Cell Biology and Anatomy, University of Tokyo, Graduate School of Medicine, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033,Japan
Osteological characteristics of extant, quadrupedal,aquatic or amphibious mammals are compared andused to determine the presence and state of develop-ment, or absence, of aquatic adaptations in the orderDesmostylia. The specimens compared include sev-enteen bones from in each species four higher taxa:Rodentia, Carnivora, Mustelidae and Artiodactyla.The aquatic form is compared with its terrestrialcounterpart within each group. Quantitative evi-dence of convergence is used to sort out charactersthat are adaptive in relation to aquatic habits.Aquatic conformations or tendencies are identifiedas those characters, displayed by aquatic forms indifferent taxonomic groups, that have more in com-mon with each other than with corresponding char-acters of land animals in the same taxa. About 80% ofthe 49 aquatic adaptive characters identified are alsofound in desmostylians. This analysis documents thegradual evolutionary transition of desmostylians toan aquatic mode of life. Furthermore, the results showthat the desmostylian swam better using itshind-limbs at least than the hippopotamus.
Keywords: Amphibious adaptation, Aquatic adaptation,Comparative osteology, Desmostylia, Desmostylus, Func-tional morphology, Methodology
INTRODUCTION
Members of the Desmostylia, an extinct mamma-lian order, mainly inhabited the Pacific coasts ofJapan and North America in the Oligocene andMiocene (Inuzuka et ah, 1994). Among recentmammals, the Desmostylia is closely related to
* telephone and fax: 81-3-5841-3334
the Proboscidea and Sirenia, with them compris-ing the Tethytheria (McKenna, 1975; Domning etal., 1986). The order includes six genera, amongstthem Desmostylus and Paleoparadoxia (Inuzuka,1999-b). The dentition and body form of the des-mostylians are unique, and many ecologicalquestions concerning them remain unsolved(Inuzuka, 1984,1999-a).
Until the discovery of a postcranial skeleton,desmostylians were assigned to the Sirenia. Theywere regarded as purely aquatic mammalsbecause "their remains are always found in for-mations known to be marine; certain charactersin the skull, such as the absence of a lacrymalforamen, appear to be aquatic adaptations; thestructure of the forefoot is like that of the largerpinnipeds and of the Sirenia" (VanderHoof,1937). When a postcranial skeleton was finallydiscovered in Sakhalin, it was seen to be that ofan amphibious (Nagao, 1941) or semiaquatic toaquatic animal (Reinhart, 1959), with stout limbbones similar to those of the hippopotamus.
Aquatic adaptations of vertebrates in generalhave been summarized by Abel (1912), Boker(1935), and Lessertisseur and Saban (1967), andaquatic adaptations of the cranium have beendiscussed by Hilzheimer (1913) and Matsumoto(1923). However, the morphology of each bonein postcranial skeletons has not been analyzed to
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98 NORIHISA INUZUKA
assess its aquatic or amphibious adaptation. Theobject of this study is to compare aquatic mam-mals with their terrestrial relatives, so as todetermine the presence or absence and thedegree of development of aquatic adaptations inthe order Desmostylia.
In determining the functional significance ofevolutionary changes and the modes of life ofextinct species, Radinsky (1987) notes that "theform-function correlation approach works wellas long as we have living species with the ana-tomical features in question, but many fossil spe-cies display features unknown in the modernworld." In the latter case this approach cannot beused. Because desmostylians lack modern ana-logues and have many unique anatomical fea-tures, a modified approach to form-functioncorrelation is applied in this paper (Inuzuka,1996).
As the desmostylians had stout limb bones,extant land mammals and quadrupedal aquaticmammals within each of the same four highertaxonomic groups, with known ecologies, wereselected for comparison. Aquatic mammalswithout hindlimbs, such as cetaceans and sireni-ans, were excluded from the study due to theirfully aquatic habits. Coccygeal vertebrae, thesternum, ribs, and manus, all of which areextremely specialized in these two groups, werenot considered in this study.
Results of comparative osteological studiesand analysis of sets of measurements reportedhere indicate that the desmostylians were clearlyadapted to aquatic conditions. The hind limbswere more fully adapted to life in water thanthose of the hippopotamus, and the extent ofaquatic adaptation progressed as the desmo-stylians evolved.
MATERIALS AND METHODS
Sixteen species from four orders of extant mam-mals and seven fossil specimens belonging to
four desmostylian genera were examined(Appendix 1). The Ashoro I specimen is the mostprimitive, representing an undescribed genus ofthe Desmostylia (Inuzuka, 1999-b). One hundredand eighteen osteological features of each speci-men were compared using the following seven-teen bones: scapula, humerus, radius, ulna,pelvis, femur, patella, tibia, fibula, talus, atlas,axis, cervical, thoracic and lumbar vertebrae, sac-rum and cranium. One hundred and nine pointswere measured and compared using a variety ofindices, some of which are plotted on scatter-grams. Those indices that were calculated asratios of pairs of variables are defined at the endof Appendix 2.
Because desmostylians were quadrupedalaquatic mammals, only certain aspects of aquaticadaptation are likely to occur, in contrast to themore substantial modifications of fully aquaticmammals like whales and sirenians. Hence, Isought to determine how each bone of an aquaticor amphibious quadrupedal mammal was influ-enced by the animal's lifestyle. The beaver wascompared with the squirrel in the Rodentia, theseal with the dog in the Carnivora, the river otterwith the weasel in the Mustelidae, and the hip-popotamus with the wild pig in the Artiodac-tyla. Morphological characteristics that arecommon to more than half the aquatic forms(beaver, seal, river otter, and hippopotamus) anddifferent from those of related land animals wereidentified. In addition to these features, commontendencies of morphological change related toaquatic life were included as adaptive charac-ters. For example, the indices used to comparelengths of the spinous process of the thoracicvertebra are equal in the squirrel and river otter.But, the index for the squirrel is larger than thatfor the beaver, and that for the weasel is largerthan that for the river otter. So, this index tendsto be greater in fully terrestrial than in aquaticforms. Morphological change with the same ten-dency in distantly related taxonomic groups,rodents and mustelids in this case, representsevolutionary convergence. Such directions of
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DESMOSTYLIAN AQUATIC ADAPTATIONS 99
morphological change or evolutionary tenden-cies express convergent adaptation more clearlythan the character states of individual taxa,themselves.
Eight species in four groups were used as sub-jects for comparison. Each species has somecharacteristics that are unique to that species. Toexclude contingencies due to specific charactersof this kind and to sort out those tendencies thatoccur only in adaptation for aquatic life, addi-tional animals were included in the study, thelion as another example of a land carnivore, thefur seal as another marine carnivore, and themuskrat and nutria as aquatic rodents.
Closely-related species of different sizes wereincluded in the analysis to eliminate the influ-ence of size differences among the species beingcompared. A cat and a lion, as representatives ofthe Felidae, and an Asiatic black bear and abrown bear, from the Ursidae, were used for thispurpose. Some characters show common ten-dencies in comparisons between the lion and thecat and between the brown bear and the Asiaticblack bear. As these may be related to size, theyare excluded from the list of characters supposedto be related to aquatic adaptation. Those charac-ters that are common to more than half theaquatic rodents, carnivores, mustelids, and artio-dactyls are regarded as manifestations of aquaticadaptation.
The order Desmostylia is closely related to theProboscidea and the Sirenia. However, livingelephants are highly specialized, notably in theirgraviportal adaptations, and extant sirenians arefully aquatic. Therefore, the wild pig and thetapir were selected as representative, more gen-eralized, land ungulates. Among the characterslisted above, similar changes observed from theforms of bones in the wild pig and the tapir tothose which occur in advanced desmostylians,such as Paleoparadoxia or Desmostylus, areregarded as aquatic adaptations of the desmo-stylians.
Paleoparadoxia Desmostylus
FIGURE 1 Comparison of the left femoral condyle in distalview. Left column: terrestrial forms except Paleoparadoxia.Right column: aquatic forms
In these comparisons, the numbers of charac-ters linked to an aquatic mode of life are taken toindicate the degree of aquatic adaptation, eitherof skeletal elements or of taxonomic groups.
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55-
50
45
£40-c
£35-
: 30-
25-
20-
15-
seal
river ottersquirrel
weasel
black bear A
| terrestrial
% aquatic
A size factor
+ land ungulate
•k Desmostylia
A cat
lion A • tapirhippo
wild pig— •
10 20 30 40Sacro-iliac angle
50 60
FIGURE 2 Scattergram showing the relation between the sacro-iliac angle and the index of pelvic length/pubic length
RESULTS
Among fifty-five morphological trends recog-nized in comparison with extant species, six areexcluded as changes that may be related to size:protrusion of the deltoid crest of the humerus,enlargement of capitulum to trochlea, extensionof the ischium, heightening of greater trochanterto femoral head, widening and shortening of thepatellar surface of the femur, and antero-poste-rior thickening of the patella. The remaining 49changes in form are regarded as aquatic adapta-tions (Appendix 3).
Amongst these, 25 common tendencies occurin all four groups, rodents, carnivores, mustel-ids, and artiodactyls. They include, for example,shallowing of the patellar surface of the femur(Figure 1) and reduction of the sacro-iliac angle(Figure 2). Nine items are common to all groupsexcept the artiodactyls, including extension of
the pubis (Figure 2) and flattening of the femoralshaft (Figure 3). Seven items are common to allbut the mustelids, including lowering of thecapitulum below the trochlea (Figure 4). Threeare common to all but the carnivores. Two itemsare common only to carnivores and mustelids.Finally, a trend that is observed only in rodentsand carnivores is the lateral bending of the tibialshaft (Figure 5); one that is common only torodents and mustelids is the development of arectangular outline to the sacrum (Figure 6); andone common only to carnivores and artiodactylsis the thickening of the fibula.
Generally speaking, the adaptations of quad-rupedal aquatic mammals show tendenciestoward shorter limb bones, widening of bones inproportion to their lengths (Figures 3, 7, and 9),and shallowing of bone articular surfaces (Fig-ures 1 and 8). The epiphyseal region to whichmuscle is attached lengthens (Figure 9), increas-
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DESMOSTYLIAN AQUATIC ADAPTATIONS 101
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FIGURE 3 Scattergram showing the relation between the index of femoral length/distal width and the index of femoral shaftwidth / thickness
squirrel
beaver
weasel wild pig tapir Paleoparadoxia
seal otter hippo Ashoro I Desmostylus
FIGURE 4 Comparison of right humeral condyles in cranial view. Upper row: terrestrial forms except Paleoparadoxia. Lowerrow: aquatic forms
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102 NORIHISAINUZUKA
squirrel beaver dog seal tapir Paleoparadoxia
FIGURE 5 Comparison of right tibias in cranial view
beaver seal otter Paleoparadoxia
FIGURE 6 Comparison of sacra in ventral view. Upper row: terrestrial forms. Lower row: aquatic forms
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DESMOSTYLIAN AQUATIC ADAPTATIONS 103
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10 15 20 25 30 35 40Tibial length / proximal width index
45 50
FIGURE 7 Scattergram showing the relation between the index of tibial length/proximal width and the index of tibiallength/distal width
ing the lever-arm ratio. The vertebral columntends to exhibit shortening of the vertebrae,which become wider in proportion to theirlengths (Figure 10), with shortening of thespinous process (Figure 11) and a widening ofthe range of joint movements. The length of thecranium gets shorter; the nasal bone is reducedto form a narial opening that faces upward(Figure 12); the orbit moves upward and facesmore upward; and the range of movement of theatlanto-occipital joints increases.
Of the 49 aquatic adaptations recognized inthis analysis, 39 occur in desmostylians (Appen-dix 2). Fourteen of these appear even in the mostprimitive genus, including shortening of the ver-tebral centrum, a steeper inclination of thespinous processes on the fifth to eighth thoracicvertebrae (Figure 13), and weakening of theoccipital condyle ridge. Eight items appear firstin Behemotops, including widening of the ante-
brachial epiphyses (Figure 9). Seventeen changesappear for the first time in Paleoparadoxia andDesmostylus, including lateral bending of the tib-ial shaft (Figure 5), shallowing of the trochlea taligroove (Figure 8), and enlargement of the sacralforamina (Figure 6). Since many elements of thetwo primitive genera known only from materialin the Ashoro Museum of Paleontology (Appen-dix 1) have not yet been discovered, the numberof aquatic characteristics they display will prob-ably increase with future discoveries.
The 49 aquatic characters are associated withthe following parts of the skeleton: forelimb, 11;hindlimb, 17; and axial skeleton 21 (Appendix 3).The 39 characters recognized in desmostyliansconsist of: forelimb, 7; hindlimb, 16; and axialskeleton, 16. These represent 64%, 94%, and 76%,respectively, of the character set for each skeletalpart. This indicates that in desmostylians,aquatic adaptation in the hindlimb was more
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seal
weasel otter
Itapir Behemotops
Paleoparadoxia Desmostylus
FIGURE 8 Comparison of left trochlea tali grooves in poste-rior view. Left column: terrestrial forms exceptPaleoparadoxia. Right column: aquatic forms
advanced than in the other skeletal elements.The hippopotamus lives in aquatic habitats and,besides swimming, walks in water. Characters ithas in common with rodents and carnivores butnot with artiodactyls, are noted in the pelvis,femur, and cervical vertebrae, all of which maybe related to swimming. The fact that these char-acters are more strongly developed in desmo-stylians than in the hippopotamus suggests thatthe desmostylians evolved further in the directionof swimming, using their hindlimbs, than the hip-popotamus.
CONCLUSION
Forms of the skeletons in four groups of extantquadrupedal mammals including aquatic repre-sentatives were compared by examination of 17different bony elements. In this data set, 49 char-acters were identified as aquatic adaptations.Approximately 80% of these characters were alsorecognized in desmostylians, indicating theyhad evolved numerous aquatic adaptations. Infact, the desmostylians exhibit more charactersin the pelvis and femur that are inferred to berelated to aquatic habits than are observed in thehippopotamus, today. Therefore, the desmo-stylians probably swam better using their hind-limbs than the hippopotamus, at the very least.Furthermore, among the desmostylians, theadvanced forms Paleoparadoxia and Desmostylusreveal more characters identified as aquaticadaptations than does a more primitive genus,Behemotops. Thus, a gradual adaptive transitionby desmostylians to life in the water is docu-mented and elucidated by this analysis.
Acknowledgements
For assistance in the comparative study of mam-malian skeletons, I would like to express mythanks to the National Science Museum, Tokyo,the Chiba Central Museum, and the AshoroMuseum of Paleontology.
References
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Stuttgart: E. Schweizerbart'sche Verlagsbuchhandlung.
Böker, H. (1935) Einführung in die vergleichende biologisch
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new Oligocene desmostylians and a discussion of teth-
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Hilzheimer, M. (1913) Handbuch der Biologie der Wirbeltiere.
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DESMOSTYLIAN AQUATIC ADAPTATIONS 105
40 -,
35-
; 30-£ 3c
co
I 25.
j j 20COc
15-
10-
squirrel
10
wild pig •tapir
river otter
black bear
A brown bear—i—15
Paleoparadoxia
•Desmostylus
seal
20 25 30Radial length / distal width index
hippo
terrestrial
aquatic
size factor
land ungulate
Desmostylia
35 40
FIGURE 9 Scattergram showing the relation between the index of radial length /distal width and the index of ulnar length/olecranon length
beaver
seal otterDesmostylus
FIGURE 10 Comparison of the axis in ventral view. Upper row: terrestrial forms. Lower row: aquatic forms
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106 NORIHISAINUZUKA
75n
70-
I3o 60
iO)c01
Q.45HM
•5.40HW
35-
30-
terrestrial
aquatic
size factor
land ungulate
Desmostylia
•Paleoparadoxia
•Desmostylus
seal 4
beaver
tapirsquirrel
Asiatic black bear
Ashoro specimen
45 50 55 60 65 70 75Spinous process length index of thoracic vertebrae
lion
80 85
FIGURE 11 Scattergram showing the relation between the index of spinous process length of thoracic vertebrae and of thesacrum
JPaleoparadoxiabeaver seal otter hippo
FIGURE 12 Comparison of narial openings in dorsal view. Upper row: terrestrial forms. Lower row: aquatic forms
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DESMOSTYLIAN AQUATIC ADAPTATIONS 107
squirrel beaver
weasel
seal
otter
Ashoro Itapir
FIGURE 13 Comparison of spinous processes from the fifth to eighth thoracic vertebrae. Left column: terrestrial forms. Rightcolumn: aquatic forms
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108 NORIHISA INUZUKA
Inuzuka, N. (1999-a) Research trends and scope of the orderDesmostylia. Bulletin of the Ashoro Museum of Paleontol-ogy 1, (in press).
Inuzuka, N. (1999-b) Primitive Late Oligocene desmostyliansfrom Japan and the phylogeny of the Desmostylia. Bulle-tin of the Ashoro Museum of Paleontology 1, (in press).
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Lessertisseur, J. and Saban, R. (1967) Squelette appendicu-laire. In Traité de Zoologie, edited by P. P. Grassé, pp. 961-1078. Paris: Masson.
Matsumoto, H. (1923) A contribution to the knowledge ofMoeritherium. Bulletin of the American Museum of NaturalHistory 48, 97-139.
McKenna, M. C. (1975) Toward a phylogenetic classificationof the Mammalia. In Phylogeny of the Primates, edited by
W. P. Lukkett and F. S. Szalay, pp. 21-46. New York andLondon: Plenum Publishing Corporation.
Nagao, T. (1941) On the skeleton of Desmostylus. In JubileePublication in the Commemoration of Prof. H. Yabe's 60thbirthday, [no editor designated], pp. 43-52. Sendai,Japan: Tohoku University, Chishitsugaku Koseibutsug-aku Kyoshitsu.
Radinsky, L. B. (1986) The Evolution of Vertebrate Design. Chi-cago: University of Chicago Press.
Reinhart, R. H. (1959) A review of the Sirenia and Desmo-stylia. University of California Publications in GeologicalSciences 36, 1-146.
VanderHoof, V. L. (1937) A study of the Miocene sirenianDesmostylus. University of California Publications in Geo-logical Sciences 24, 169-262.
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DESMOSTYLIAN AQUATIC ADAPTATIONS 109
APPENDIX 1Specimens of Extant and Extinct Taxa Included in this Study
Species
Tamiasciurushudsonicus
Castor canadensis
Ondatra zibethicus
Myocastor coypus
Canisfamiliaris
Seknarctosthibetanus
Ursus arctos
Mustela itatsi
Lutra canadensis
Felis catus
Panthera leo
Phoca largha
Callorhinus ursinus
Sus leucomustax
Hippopotamusamphibius
Tapirus indicus
Genus and speciesnov.
Behemotops sp. nov.
Paleoparadoxiatabatai
Paleoparadoxiatabatai
Paleoparadoxia sp. nov.
Desmostylus hesperus
Desmostylus hesperus
CommonName
American redsquirrel
American beaver
Muskrat
Nutria
Dog
Asian black bear
Brown bear
Japanese weasel
Canadian otter
Domestic cat
Lion
Spotted seal
Northern fur seal
Japanese wild pig
Hippopotamus
Malayan tapir
Ashoro specimen I
Ashoro specimen II
Izumi specimen
Tsuyama specimen
Stanford specimen
Utanobori specimen
Keton specimen
Order
Rodentia
Rodentia
Rodentia
Rodentia
Carnivora
Carnivora
Carnivora
Carnivora
Carnivora
Carnivora
Carnivora
Carnivora
Carnivora
Artiodactyla
Artiodactyla
Perissodactyla
Desmostylia
Desmostylia
Desmostylia
Desmostylia
Desmostylia
Desmostylia
Desmostylia
Family
Sciuridae
Castoridae
Muridae
Myocastoridae
Canidae
Ursidae
Ursidae
Mustelidae
Mustelidae
Felidae
Felidae
Phocidae
Otariidae
Suidae
Hippopotamidae
Tapiridae
Behemotopsidae
Behemotopsidae
Desmostylidae
Desmostylidae
Desmostylidae
Desmostylidae
Desmostylidae
Age
adult
juvenile
adult
adult
juvenile
adult
adult
adult
adult
adult
adult
juvenile
juvenile
adult
juvenile
adult
adult
adult
juvenile
adult
adult
juvenile
adult
Storage
Inuzuka
Inuzuka
Inuzuka
Inuzuka
Inuzuka
Univ. Tokyo
Inuzuka
Chiba Mus.
Chiba Mus.
Inuzuka
Univ. Tokyo
Inuzuka
Univ. Tokyo
Ashoro Mus.
NSM, Tokyo
Univ. Tokyo
Ashoro Mus.
Ashoro Mus.
NSM, Tokyo
TsuyamaMuseum
UCMP
Geol. Surv.Japan
HokkaidoUniversity
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APPENDIX 2 gMeasurements and calculated indices for each specimen
pelvic length
pubic length
femoral length
femoral distalwidth
femoral shaftwidth
femoral shaftthickness
tibial length
tibial proximalwidth
tibial distalwidth
radial length
radial distalwidth
ulnar length
olecranon length
thoracic vertebralheight
thoracic vertebralbody height
spinous processvertebral lengthon thoracic
sacral height
sacral body height
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
(mm)
squirrel
42
13
53.9
8.8
3.9
3.6
61A
9.1
5.4
39.6
4.2
47
5.2
9.6
2.4
7.2
10
3
dog
149
34
109
20.5
7.9
7.9
113
22.8
15.1
100
15.8
119
20
58
12
46
25
14
weasel
41
8.8
46.5
9
3.6
3.6
51
8.6
6.6
30
5.2
38
5.7
12.5
2.5
10
10.7
3.4
wild pig
246
41
227
50
23
24
202
54
31
153
38
212
59
103
21
82
46
17
beaver
154
55
79
35.4
16
9
100
29.8
19
66
11
85
11.5
25
9
16
31
14
seal
113
59
77
43
16.9
9
134
40.4
22.5
75
23
90
16
37
16
21
34
23
riv. otter
89
29
76
20
8.9
6.8
88
21
14.6
55
12
74
15
27.6
7
20.6
24
8.5
hippo
452
77
357
129
44
47
260
120
74
209
83
284
90
-
-
—
-
cat
83
18.7
110
19.7
9.7
8.1
115
20.2
15
94
13.7
113
13
33.8
5.3
28.5
25
7.2
lion
306
59
381
76
36
32
336
86
59
312
62
376
53
128
25
103
69
33
blkbear
227
57
267
58
28.5
21
207
63
45
219
45
250
33
77
22
55
46
24
brn bear
327
78
403
79
29
28
317
84
61
320
54
369
41
111
28
83
69
29
tapir
429
80
335
90
35
36
274
86
54
231
57
299
80
111
30
81
85
24
Ashoro I
-
-
-
-
-
-
-
-
-
81+
-
-
54
82
27
55
54
34
Behemo
-
-
450
161
77
55
377
154
103
-
-
-
-
-
-
—
-
-
Paleo
587
144
354
132
67
31
348
118
123
264
88
344
110
109
54
55
86
49
Desmo
636
210
377
134
84
32
244
99
91
187
60
241
61
109
59
50
91
45
aCdw
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spinous proc.length on sacrum
sacro-iliac angle
index of pubiclength
index of femoraldistal width
index of femoralwidth/thickness
index of tibialproximal width
index of tibialdistal width
index of radialdistal width
index of olecranonlength
index of sp. proc.of thoracic vert.
index of sp. proc.of sacral vert.
(mm)
(°)
*(D
*(2)
*(3)
*(4)
*(5)
*(6)
*(7)
*(8)
*(9)
squirrel
7
17
31
16
92
15
9
11
11
75
70
dog
11
48
23
19
100
20
13
16
17
79
44
weasel
7.3
20
21
19
100
17
13
17
15
80
68
wild pig
29
55
17
22
104
27
15
25
28
80
63
beaver
17
15
36
45
56
30
19
17
14
64
55
seal
11
20
52
56
53
30
17
31
18
57
32
riv. otter
15.5
10
33
26
76
24
17
22
20
75
65
hippo
—
35
17
36
107
46
28
40
32
-
-
cat
17.8
50
23
18
84
18
13
15
12
84
71
lion
36
30
19
20
89
26
18
20
14
80
52
blk bear
22
30
25
22
74
30
22
21
13
71
48
brn bear
40
45
24
20
97
26
19
17
11
75
58
tapir Ashoro I
61 20
40
19
27
103
31
20
25
27
73 67
72 37
Behemo
—
-
-
36
71
41
27
-
-
-
-
Paleo
37
30
25
37
46
34
35
33
32
50
43
Desmo
46
-
33
36
38
41
37
32
25
46
51
o252>
* Definitions of indices: (1) pubic length / pelvic length; (2) femoral distal width / femoral length; (3) femoral shaft thickness / femoral shaft width; (4) tibial proximalwidth / tibial length; (5) tibial distal width / tibiallength; (6) radial distal width / radial length; (7) olecranon length / ulnar length; (8) spinous process length onthoracic vertebra / thoracic vertebral height; (9) spinous process length on sacrum / sacral height; each ratio x 100.
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APPENDIX 3 5
Assessment of Characters by Taxonomic Group in Relation to Aquatic Adaptationin Mammals. O, Present; X, Absent; Dash, No Data
Advance of scapular spine
Thinning of posterior margin of scapula
Shallowing of glenoid cavity
Shortening of humerus
Widening of proximal epiphysis of humerus
Thickening of humeral shaft
Protrusion and extension of deltoid crest
Enlargement of capitulum to trochlea
Lowering of capitulum below trochlea
Shallowing of olecranon fossa
Widening of antebrachial epiphyses
Thickening of antebrachial shaft
Extension of olecranon
Reduction of sacroiliac angle
Shallowing of acetabulum
Advance of acetabulum
Extension of pubis
Extension of ischium
Reduction of ischial tuberosity
Reduction of pelvic symphyseal angle
Heightening of greater trochanter
Shortening of femur
Widening and thinning of epiphyses
Enlargement of femoral head
Flattening of femoral shaft
ROD
Rodentia
O
O
oooooooX
ooooooooooooooo
CARN
Carnivora
O
O
ooooooooooooooooooooooo
MUS
-telidae
ooX
oooooX
ooX
ooooooooX
oooo
ART
-iodactyla
O
O
oooX
oooX
ooooX
X
X
X
X
oooo0
X
DESM
-ostylia
X
X
oX
X
ooX
oooooooooX
ooX
oooo
ASH I
Ashoro I
o
oX
oX
-
o--X
-
-
o-
----
BEH
-emotops
-
O
-
-
-
o------
o-
oooo
PALEO
-paradoxia
O
O
o
ooooooooo
oo
oooo
DES SIZE
-mostylus factor
O
O
o ••
ooooo-ooo
•oo
•oooo
r-H
1
2>
ATI
n>
3
DID
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ROD CARN MUS ART DESM ASH1 BEH PALEO DES SIZE
Rodentia Carnivora -telidae -iodactyla -ostylia Ashorol -emotops -paradoxia -mostylus factor
Shallowing of patellar surface of femur O O O O O - O O O
Widening of patellar surface of femur O O O O O - O O O •
Shortening and thickening of patella O O O X X •
Widening of articular surface of patella O X O O O - O O O
Lateral bend ing of tibial shaft O O X X O - X O O
Widening of tibial ep iphyses O O O O O - O O O
Weakening of tibial crest X O O X X
Thickening of fibula X O X O O - - O
Shallowing of trochlea tali g roove O O X O O - X O O
Shortening of cervical ver tebra O O O O O O - O O
Strengthening of cervical lordosis O O O X X
Shortening of vertebral b o d y O O O O O O - O O O
Shallowing of atlantal fossa O O X O O - - O O 53
Widening of axis O O O O O - - O O >
Enlargement of dens of axis O O O O O - - O O §
Shortening of sp inous process on thoracic v. O O O O O O O O O G
Steeper inclination of spine in midthoracic v. O O O O O O - O O •**
Shortening of lumbar vertebral b o d y O O O O O O O O O
Increase of distance b e t w e e n zygapophyses O O O O O O O O O
Gentler inclination of articular surfaces O O O X X
Horizontal projection of t ransverse processes O X O O O O O O O
Enlargement of sacral foramina O O X O O X X O O
Shortening of sp inous process in sacrum O O O O O O - O O
Rectangular out l ine of sac rum O X O X X
Shortening of c ran ium O X O O X
Regression of nasal bone O O O O O - - O O
U p w a r d facing of orbita O O O O O - - O O
Advance of orbita O O X O O - - O O
Complex nasal conchae O O O X - - - -
Weakening of r idge of occipital condyles O O O O O O - O O -
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