close

Вход

Забыли?

вход по аккаунту

?

Comparison of muscle weight and force ratios in new and old world monkeys.

код для вставкиСкачать
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 82~509-515(1990)
Comparison of Muscle Weight and Force Ratios in New and Old
World Monkeys
MARIANNE BOUVIER AND STEPHEN M. TSANG
Department of Cell Biology and Anatomy, University of Miami School of
Medicine, Miami, Florida 33101
KEY WORDS
Biomechanics, Craniofacial Skeleton, Masticatory
Muscles
ABSTRACT
Thin mandibles and small incisors found in New World
monkeys as compared with Old World monkeys suggest that there may be
differences in craniofacial loading patterns between these two groups, particularly in levels of mandibular corpus twisting (Hylander, 1975,1979a; Eaglen,
1984; Bouvier, 1986a,b). This study examined the hypothesis that changes in
the relative force contributions of the masticatory muscles were responsible for
lowering torsion on the mandibular corpus in New World monkeys, Muscle
weight and physiological cross-sections were compared using data from the
literature (Schumacher, 1960; Turnbull, 1970; Cachel, 1979) as well as new
data on adult male Cebus apella and Macaca mulatta. Both age and sex had an
effect on muscle ratios. Mixed samples such as those used by Schumacher and
Turnbull probably are not appropriate for drawing conclusions concerning
species or group differences in muscle ratios. In addition, biomechanical
conclusions based on muscle weight ratios alone to estimate muscle force may
be misleading because fiber length inversely affects the amount of force a
muscle can exert. A comparison of ratios based on physiological cross-section
as an estimator of muscle force in New and Old World monkeys does not
support the hypothesis that alterations in force contribution by individual
masticatory muscles are responsible for minimizing mandibular corpus twisting in New World monkeys. Therefore, if twisting has been minimized in New
World monkeys as suggested by their thin corpora, other changes in the
craniofacial musculoskeletal complex, such as different muscle recruitment or
pinnation patterns, may be responsible.
Considerable information on the evolution
of dietary adaptations in primates has been
obtained through studies of the masticatory
apparatus in monkeys. Such studies centering on two particular groups, the New and
Old World monkeys, have shown that distinctive atterns of craniofacial morphology
are like y related to the chewing stresses
associated with different diets (Hylander,
P
1986a,b).For
short, dee , and wide jaws of the Old World
colobines ave been related t o their characteristic diet of leaves.
R
1990 WILEY-LISS, INC.
In vivo bone strain studies have confirmed
that diet affects mandibular loading during
mastication (Hylander, 1979b, 1984). These
strain gage studies demonstrate that the Old
World monkey mandibular corpus is both
bent and twisted about its long axis during
mastication. In addition, these studies show
that differences in food consistency, such as
between hard fruits and leaves, significantly
affect levels and atterns of mandibular
bone strain. Thus, one strain studies have
strengthened the relationship between dietary adaptation and jaw morphology. Consequently, the inferring of dietary adapta-
E
Received October 10,1988; accepted October 30,1989
510
M. BOUVIER AND S.M. TSANG
tion from craniofacial skeletal morphology
continues to be a productive approach to
problems of rimate functional and evolutionary morp ology.
Unfortunately, no bone strain data are
available for New World monkeys; however,
comparisons of their mandibular morphology with that of Old World monkeys suggest
that there may be significant differences in
mandibular stresses during mastication between the two groups. Compared with Old
World monkeys, New World monkeys have
small incisors and markedly thinner mandibular corpora (Eaglen, 1984; Bouvier,
1986b). The distinctive jaw morphology of
New World monkeys, articularly the thinness of the mandibu ar corpus, indicates
that their cor us may be subjected to considerably lower oads during mastication, with
especially low levels of twisting.
In the absence of bone strain data for New
World monkeys, the size and arrangements
of the chewing muscles can elucidate loading
patterns on the mandible. Among the primary chewing muscles, temporalis, masseter, and medial pterygoid are chiefly responsible for twisting of the jaws (Fig. 1). In
Old World monkeys, the origin of the masseter muscle, on the zygomatic bone, is located more laterally than its insertion on the
angle of the mandible. Therefore, during
mastication, the masseter will tend to evert
the lower border of the Old World monkey
mandible. Conversely, the medial pterygoid
muscle produces inversion of the lower mandibular border because its origin, on the
pterygoid plates, is medial to its insertion on
the mandibular angle. Thus, because the
masseter and medial pterygoid muscles
twist in opposite directions, they can theoretically neutralize one another if their respective moments are e ual. The tem oralis
muscle contributes slig tly to man ibular
twisting. Depending on its precise orientation, the direction of twisting could be either
with masseter or with medial pterygoid.
In Old World monkeys, the masseter muscle is approximately twice as large as medial
terygoid muscle (Hylander, 1979a). Thereore, the masseter muscle in Old World monkeys, by virtue of its relatively large size,
overcomes the opposing pull of the smaller
medial pterygoid muscle. The result is a
torque on the mandible tending to evert its
lower border. H lander’s (1979b, 1984) in
vivo bone strain ata confirm that Old World
monkey mandibles are twisted in this fash-
g
P
P
a
F
i
l
B
Fig. 1. Lines of action for temporalis (TI, masseter
(Ma), and medial pterygoid iMp) muscles.
ion during mastication. The temporalis muscle in Old World monkeys probably contributes only slightly to twisting, most likely in
concert with masseter.
The degree of mandibular twisting, therefore, is determined largely by the positioning
of the origins and insertions of temporalis,
masseter, and medial pterygoid muscles and
by their respective contributions to the total
masticatory force. Mandibular twisting may
be maximized when there is a lateral positioning of the chewing muscle resultant (Hylander, 1979b),which occurs when there is a
large masseter: medial pterygoid andlor a
large temporalis: medial pterygoid muscle
force ratio.
This study compares these masticatory
muscle ratios in New and Old World monkeys, first using data available from the
literature (Schumacher, 1961; Turnbull,
1970; and Cachel, 1979). Second, these results are compared with new data presented
here for one New World monkey (Cebus
upella) and one Old World monkey (Mucaca
mulattu)in order to determine whether masticatory muscle ratios differ in a manner
consistent with the hypothesis of lower mandibular corpus twistin in New World monkeys compared with 0 d World monkeys. In
addition, this study examines the relationship between muscle weight versus muscle
force ratios (i.e., physiological cross-section)
in the chewing muscles of New and Old
World monkeys.
f
511
MUSCLE RATIOS IN MONKEYS
MATERIALS AND METHODS
Schumacher (1961) study
Schumacher’s primate sample consisted of
3 New World monkeys (Cebus uariegatus, C.
apella, Saimiri) and 7 Old World monkeys (2
Macaca mulatta, 2 M. sinica, Papio, Mandrillus, Colobus) (Table 1).This mixed sample includes both males and females, adults
and ‘uveniles. Schumacher included dry
musc e weight as well as physiological crosssection (PCS) after Weber (Carlsoo, 1952):
i
2
Dry weight ( )/fiber length (cm) muscle
specikc gravity ~ 1 . g/cm
0
1
Turnbull (1970) study
Turnbull examined relative wei hts (i.e.,
percentages) of masticatory musc es using
rimate data from two previous studies:
chumacher (1961) and Fabian (Table 2). In
addition to Schumacher’s primate specimens, Turnbull included the following specimens from Fabian’s study: 1 New World
monkey (Callithrixpennicillata) and 11 Old
World monkeys (Macaca mulatta, Papio sp.,
Theropithecus gelada; Cercopithecus diana,
Erythrocebuspatas, and 2 Colobus s 1. This
is a mixed sample consisting of bot males
and females, adults and juveniles.
F
8
R‘
Cachel (1979) study
Cachel separated her sample by age and
sex (Table 3). She included, among the
adults, 10 male New World monkeys (5
Saimiri sciureus, 4 Saguinis fuscicollis, Alouatta palliata);9 male Old World monkeys
(3 Macaca mulatta, Erythrocebus patas, 2
Cercopithecus ascanius, 2 Papio cynocephalus, Mandrillus sphinx); 13 female New
World monkeys (5 Saimiri sciureus, Saguinus fuscicollis 4 Ateles geoffroyi, 2 Alouatta
palliata, Cacajao rubicundus); and 15 female Old World monkeys ( 3 Macaca mulatta, Erythrocebus patas, 3 Cercopithecus
ascanius, 2 C. aethiops, 2 C. neglectus, C.
diana, 3 Colobus polykomos). Among the
juveniles (grade II), she included no male
New World monkeys; 8 male Old World monkeys (3 Macaca mulatta, Cercopithecus neglectus, C . albogularis, Presbytis cristatus,
Papio cynocephalus, P. hamadryas); 3 female New World monkeys (Ateles geoffroyi)
and 5 female Old World monkeys (Macaca
mulatta Erythrocebus patas, Colobuspolykomos, Papio cynocephalus, Theropithecus
gelada). In addition, Cachel included 3 infant (grade I) specimens, all males (Cercopithecus aethiops, Colobus polykomos, Papio
cynocephalus). Cachel analyzed dry weight
T A B L E 1. Analysis of Masticatory Muscle Weight and PCS Ratios i n New and Old World Mor~keys‘
GrouD
N
New World monkeys
(SD)
Old World monkeys
(SD)
P
3
7
Temporalis :
medial pterygoid
Weight
PCS
4.20
(0.29)
4.73
(1.04)
NS
3.17
(0.61)
2.66
(0.80)
NS
Masseter : medial
pterygoid
Weight
PCS
2.58
(0.28)
2.18
(0.32)
0.04
1.89
(0.19)
1.47
(0.29)
0.05
Temporalis :
masseter
Weight
PCS
1.64
(0.12)
2.18
(0.43)
0.04
1.68
(0.22)
1.80
(0.38)
NS
‘Data frum Schumacher (1961).
T A B L E 2. Analysis of Masticatory Muscle Weight-Percent Ratios in New and Old World Monkeys1
Group
N
New World monkeys
(SD)
Old World monkeys
(SD)
P
4
‘Data from Turnbull (1970)
18
Temporalis : medial
Pterygoid
Masseter : medial
Pterygoid
Temporalis : masseter
4.28
(0.61)
4.42
( 1.95)
NS
2.51
(0.28)
2.17
(0.35)
NS
1.72
(0.30)
2.00
(0.66)
NS
512
M. BOUVIER AND S.M. TSANG
T A B L E 3. Analysis
OWM
(SD)
NWM
of
Temporalis : Masseter Weight Ratios i n New and Old World Monkeys'
Infant
Males'
Juvenile
2.29'"'
(0.97)
2.75
(0.51)
-
-
(SD)
Adult
Infant
3,76!"-!;)
(0.67)
2.55"'
(0.92)
-
Females*
Juvenile
Adult
2.44(B)
(0.96)
2.11""
(0.12)
2.85
(0.67)
2.26'"'
(0.67)
*Means with the same letter are significantly different (P< 0.05).
Data from Cache1 (1979).
'
T A B L E 4. Mean Fiber Length Imml of Masticatory Muscles: New Data
Group
N
Temporalis
Masseter
Medial
pterygoid
Lateral
pterygoid
C. apella
(SD)
M. mulatta
3
17.60
(4.36)
32.60
(4.20)
0.02
15.63
(3.50)
19.97
(6.46)
NS
9.03
(2.46)
12.93
(0.55)
0.02
8.70
(2.56)
11.17
(3.99)
NS
(SD)
P
3
of only 2 masticatory muscles, temporalis
and masseter. For this study, the anterior
and posterior fibers of temporalis were considered together.
New data
A total of six adult male specimens were
included in this study: 3 New World monkeys (Cebus apella) and 3 Old World monkeys (Macaca mulatta). A cercopithecine,
Macaca mulatta, was chosen for this comparison because it represents an Old World
monkey species with a comparatively wide
mandible relative to length (Bouvier, 1986a),
which was also readily available for dissection. Because mandibular width scaling patterns are similar in colobines and cercopithecines, M. mulatta can be considered to
represent both of these subfamilies. Of the
two New World monkeys species available to
us for dissection, Cebus apella and Saimiri
sciureus, C. apella was chosen because its
mean species body weight falls within the
Old World monkey range while that of
Saimiri does not. Mandibular corpus dimensions in C. apella are not particularly narrow, but they do fall well below the Old
World regression line (Bouvier, 1986b).
Hence, Cebus apella was considered an acceptable, albeit perhaps not ideal, candidate
for this comparison.
Temporalis, masseter, medial, and lateral
pterygoid muscles were dissected out completely. Ten muscles fibers were teased from
the surface of each muscle and measured
with dial calipers accurate to 0.1 mm (Table
4). Muscles were cleaned of all connective
tissue and dried in an oven at 60°C until all
moisture was removed. Dry weight was obtained for each muscle on a balance accurate
to 0.001 g. Right and left values were averaged (Table 5 ) . Physiological cross-section
(PCS) was calculated after Weber (Carlsoo,
1952):
PCS = Dry weight (g)/mean fiber length
(cm) x specific gravity (g/cm3)
A value of 1.0 /cm3 was used for muscle
s ecific gravity ( arlsoo, 1952). When musc e architecture is not complex (e.g., pinnated), PCS is proportional to the force that a
muscle is capable of exerting (Table 6 ) .
The following ratios were calculated using
both dry weight and PCS (Table 7): (1)temporalis: medial pterygoid; (2) masseter: medial pterygoid; (3) masseter: medial and lateral pterygoid; and (4)temporalis: masseter.
Weight and PCS percentages of total were
also calculated for each muscle (Tables 5,6).
Because of the small sample sizes in all
studies examined here, data were ranked.
Schumacher, Turnbull, and new data were
then analyzed using Student's t-test to determine whether New and Old World monkey means differed significantly ( R 0 . 0 5 ) .
Because Cachel's data were separated into a
number of different agelsex groups, analysis
P
8
513
MUSCLE RATIOS IN MONKEYS
of variance with Duncan multiple range ralis : masseter and temDoralis : medial
post-tests was used to determine iignificant pterygoid PCS ratios were ;lot different.
differences among means ( R 0 . 0 5 ) .
Turnbull data
None of the weight-percent ratios was
RESULTS
different (P>0.05) (see Table 2).
Schumacher data
Cachel data
The mean muscle weight ratio for masseter : medial pterygoid was larger in New
The mean muscle weight ratio for tempoWorld monkeys, while the temporalis : mas- ralis : masseter was lar est in Old World
seter ratio was smaller compared with Old monkey adult males (see able 3). This mean
World monkeys (see Table 1).Mean differ- differed significantly from infant male and
ences were significant for both ratios juvenile female Old World monkeys
(P<0.05). The weight ratio for temporalis : (P<0.05). Old World monke adult males
medial pterygoid was not significantly dif- also differed significantly rom all New
ferent in the 2 groups.
World monkey agehex groups (P<0.05).
The mean physiological cross-section
New data
(PCS)ratio for masseter : medical pter goid
Mucaca mulatta had a greater mean fiber
was higher in New World monkeys an this
difference was significant (P<0.05). Tempo- length compared with C. apella (Table 41,
8
P
B
T A B L E 5. Mean Dry Weight (g) and Percentage of Total Dry Weight (%)
Group
N
C. apella
3
(SD)
M. mulatta
(SD)
3
P
Temporalis
Weight
%
Masseter
Weight
3.61 1
(0.950)
9.154
(3.915)
0.02
1.436
(0.407)
2.245
(1.630)
NS
64.2
76.5
0.02
1%
25.5
17.1
0.02
of
Masticatory Muscles; New Data
Medial
pterygoid
Weight
0.429
(0.050)
0.644
(0.236)
NS
%I
7.9
5.5
0.03
Lateral
pterygoid
Weight
0.130
(0.034)
0.125
(0.108)
NS
X!I
2.4
0.9
0.02
T A B L E 6. Mean Physiological Cross-section (PCS) (in cm') and Percentages of Total PCS (%) i n
Masticatory Muscles: New Data
Grow
N
C. apella
(SD)
M. mulatta
(SD)
P
3
3
Temporalis
PCS
w
1.942
(0.165)
2.601
(0.805)
57.0
NS
NS
63.0
Masseter
PCS
%
0.859
(0.061)
0.981
(0.412)
NS
25.3
23.4
NS
Medial
pterygoid
PCS
0.462
(0.080)
0.470
(0.170)
NS
Lateral
pterygoid
PCS
Yll
13.6
11.3
w
0.142
(0.010)
0.100
(0.069)
4.2
NS
NS
NS
2.3
T A B L E 7. Mean Dry Weight and PCS Ratios in Masticatory Muscles: N e w Data
Group
N
C. apella
(SD)
M. mulatta
(SD)
P
3
3
Temporalis :
medial
pterygoid
Wt.
PCS
8.36
(1.50)
14.03
(0.87)
0.02
4.25
(0.88)
5.60
(0.51)
NS
Masseter : medial
pterygoid
Wt.
PCS
3.35
(0.92)
3.20
(1.17)
NS
1.91
(0.45)
2.07
(0.19)
NS
Masseter :
medial and
lateral pterygoid
Wt.
PCS
2.61
(0.84)
2.70
(0.78)
NS
1.44
(0.25)
1.75
(0.33)
NS
Temporalis :
masseter
Wt.
PCS
2.55
(0.38)
4.68
(1.25)
0.02
2.27
(0.29)
2.74
(0.52)
NS
M. BOUVIER AND S.M. TSANG
514
and this difference was significant for temporalis and medial pterygoid but not for
masseter and lateral pterygoid ( R 0 . 0 5 ) .
Mean dry weights (Table 5) were not significantly different, except for temporalis
(P<0.05), which was greater in M. mulatta.
Mean ercents were significantly different
in all our masticatory muscles, with masseter and the pterygoids contributing a relatively large percentage in C. apella.
None of the mean physiological cross-sections or percentages of PCS differs significantly in the two groups (Table 6, P>0.05).
For weight ratios involving temporalis, C.
apella had smaller values (Table 7). Mean
weight ratios were significantly different in
C. apella and M . mulatta for temporalis :
medial pterygoid and temporalis : masseter
but not for masseter : pterygoids. Mean PCS
ratios were not significantly different in the
2 groups (l50.05).
!
DISCUSSION
Dry weights and weight ratios found here
for adults were similar to those found by
Cachel (1979) but are considerably larger
than those found in Schumacher’s and Turnbull’s data. Weight ratios from Cachel’s ‘uvenile and infant animals were more simi ar to
those from Schumacher’s and Turnbull’s
studies. The dry weights that Schumacher
reports (except for Sairnirz) are one tenth
those found here and in Cachel’s study. This
suggests that the majority of Schumacher’s
specimens were infants or juveniles. Because Turnbull relied heavily on Schumacher’s data, most of his specimens also appear
to be young.
If all masticatory muscles grow at the
same rate, weight ratios would not be affected by age; however, Cachel’s data indicate that, in males, there is a significant
growth effect for temporalis : masseter ratios
(her 1979 study did not include other muscles). Male infants had the smallest ratios,
with juveniles intermediate, and adults
greatest (see Table 3).A direct comparison of
rhesus macaque temporalis : masseter ratios
in the various studies shows a ratio for adult
males measured here of 4.68; for adult males
in Cachel’s study, 3.92; for ‘uvenile males in
Cachel’s study, 2.98; and or Schumacher’s
study, 2.17 (age and sex unknown). Comparisons for Cebus apella and for other weight
ratios give similar results.
Cachel’s(1984)study of growth and allometry in the masticatory muscles of monkeys
1
/
from her previous study provides support for
differential growth. She found that medial
pterygoid underwent earlier relative growth
than did either masseter or temporalis. A
small and heterogenous sample did not permit further conclusions concerning other
masticatory muscles; however, Cachel concluded that growth of these muscles does not
proceed at a steady rate. Skeletal studies
confirm that craniofacial bone growth in primates is not rate-constant (Oyen et al., 1979;
Oyen and Rice, 1980; Sirianni et al., 1982;
Bouvier, 1988).
Sexual dimorphism in growth allometry
may also be a compounding problem in comparing muscle ratios from mixed samples,
particularly in Old World monkeys. Old
World male monkeys had greater temporalis: masseter weight ratios compared to females (see Table 3); however, this difference
was not significant. Thus, caution should be
exercised when making biomechanical inferences from muscle data based on mixed samles for either age or sex. As a corollary,
[ecause there may be significant agetsex
differences in muscle growth and biomechanics, this should be investigated more
closely. Furthermore, regardless of how
carefully the sample is constructed with regard to age and sex, considering muscle
weight ratios alone may give misleading results. Weight ratios do not take into account
muscle length, which has a significant (inverse) effect on the force that a muscle can
exert. If one is concerned with biomechanical
loading, muscle force, or a reasonable estimate, rather than weight is the relevant
arameter. Physiological cross-section may
e used to provide an estimate of force, taking into account both muscle weight and
fiber length (Carlsoo, 1952).Table 7 shows a
direct comparison of ratios based on either
weight or physiological cross-section. Weight
ratios involving temporalis were significantly different in the New and Old World
monkey species examined here leading t o
the impression that there may have been
adaptation in the New World monkey temporalis muscle to account for lower twisting. A
small temporalis : medial pterygoid ratio
would theoretically be associated with lower
levels of mandibular corpus twisting because
of more medial-positioning of the resultant
force which could account at least partially
for thin corpora in New World monkeys.
However, when physiologic cross-section
(taking into account both muscle weight and
E
MUSCLE RATIOS IN MONKEYS
515
fiber length) is compared, significant differ- heads for dissection. In addition, we wish to
ences in ratios involvingthe temporalis mus- thank anonymous reviewers for their many
cle disappear. This indicates that greater helpful comments.
temporalis weight in M. mulatta was partially negated by increased fiber length.
LITERATURE CITED
Thus, adaptations in muscle force ratios to
M (1986a) A biomechanical analysis of mandibminimize twisting are not apparent in C. Bouvier
ular scaling in Old World monkeys. Am. J . Phys.
upellu and may not explain thinner corpora
Anthropol69:473-482.
in New World monkeys as a group. Conclu- Bouvier M (198613)Biomechanical scaling of mandibular
dimensions in New World monkeys. Int. J. Primatol.
sions to the contrary on muscle weight ratios
7:551-567.
alone would be misleading. However, beM (1988) Age estimation in rhesus macaques
cause only one New and one Old World mon- Bouvier
(Macaca mulatta) based on mandibular dimensions.
key s ecies were examined in detail here,
Am. J. Primatol. 15t129-142.
musc e ratio adaptations to minimize twist- Cachel SM (1979) A functional analysis of the primate
masticatory system and origin of the anthropoid posting may exist in some New World monkeys,
orbital septum. Am. J. Phys. Anthropol. 47:l-17.
particularly those with especially transSM (1984) Growth and allometry in primate
versely narrow mandibular corpora such as Cachel
masticatory muscles. Arch. Oral Biol. 29287-293.
Alouattu (Bouvier, 1986b).
Carlsoo S (1952) Nervous coordination and mechanical
Other possibilities could account for less
function of the mandibular elevators. An electromyographic study of the activity, and a n anatomic analysis
twisting in New World monkeys, including
of the mechanics of the muscles. Acta Odontologica
changes in the orientations for masseter,
Scand. 10(suppl.II):1-132.
medial pterygoid and/or temporalis: 1)mas- Eaglen
RH (1984) Incisor size and diet revisited: The
seter to a more vertical position (less twistview from a platyrrhine perspective. Am. J. Phys.
Anthropol. 64:263-275.
ing);2) medial pterygoid to a more horizontal
osition (more twisting); and/or 3) tempora- Hylander WL (1975)Incisor size and diet in anthropoids
with special reference to cerocopithecidae. Science
IS to a less vertical position (more twisting
189t1095-1098.
along with medial ptery oid). In addition, Hylander
WL (1979a) The functional significance of
other explanations for t in jaws in New
primate mandibular form. J. Morphol. 106:223-240.
World monkeys include, for example, differ- Hylander WL (1979b) Mandibular function in Galago
crassicaudatus and Macaca fascicularis: An in vivo
ences in muscle recruitment patterns beapproach to stress analysis of the mandible. J . Mortween masseter and medial pterygoid, alphol. 159:253-296.
tered muscle architectural adaptations Hylander
WL (1984)Stress and strain in the mandibular
affecting forces generated, or heavy reliance
symphysis of primates. A test of competing hypothesis.
Am. J. Phys. Anthropol. 64:1-46.
on foods with mechanical consistencies associated with low torsional deformation of the Oyen OJ, Walker AC, and Rice RW (1979) Craniofacial
growth in olive baboons (Pa io cynocephalus anubis):
mandible durin ingestion and mastication.
Browridge formation. growtk. 43t174-187.
Electromyograp ic and bone strain experi- Oyen OJ and Rice RW (1980) Supraorbital development
ments investigating there hypothesis would
in chimpanzees, macaques and baboons. J. Med. Primatol. 9:161-168.
contribute significantly toward resolving
Schumacher GH (1961) Funktionelle Morphologie der
this question.
P
F
a
1
ACKNOWLEDGMENTS
We are grateful to Dr. Richard Thorington
at the Mammalogy Division, Smithsonian
Institution, for providing the Cebus apella
Kaumuskulatur. Jena: VEB Gustav Fischer Verlag.
Siranni J E , Van Ness AL, and Swindler DR (1980)
Growth of the mandible in adolescent pig-tailed
macaques (Macaca nemestrina). Hum. Biol. 54:31-44.
Turnbull WD (1970) Mammalian masticatory apparatus. Fieldiana Geology 18t147-356.
Документ
Категория
Без категории
Просмотров
2
Размер файла
593 Кб
Теги
muscle, monkey, old, weight, force, ratio, world, comparison, new
1/--страниц
Пожаловаться на содержимое документа