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Body size and scaling of the hands and feet of prosimian primates.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 133:828–840 (2007)
Body Size and Scaling of the Hands and Feet
of Prosimian Primates
Pierre Lemelin1* and William L. Jungers2
1
2
Division of Anatomy, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada T6G 2H7
Department of Anatomical Sciences, School of Medicine, Stony Brook University, Stony Brook, NY 11794-8081
KEY WORDS
allometry; body mass; cheiridia; strepsirrhines; lemurs; galagos; lorises; tarsiers
ABSTRACT
The hands and feet of primates fulfill a
variety of biological roles linked with food acquisition
and positional behavior. Current explanations of shape
differences in cheiridial morphology among prosimians
are closely tied to body size differences. Although numerous studies have examined the relationships between
body mass and limb morphology in prosimians, no scaling analysis has specifically considered hand and foot
dimensions and intrinsic proportions. In this study, we
present such an analysis for a sample of 270 skeletal
specimens distributed over eight prosimian families. The
degree of association between size and shape was
assessed using nonparametric correlational techniques,
while the relationship between each ray element length
and body mass (from published data and a body mass
surrogate) was tested for allometric scaling. Since tarsiers and strepsirrhines encompass many taxa of varying
degrees of phylogenetic relatedness, effective degrees of
freedom were calculated, and comparisons between families were performed to partially address the problem of
statistical nonindependence and ‘‘phylogenetic inertia.’’
Correlational analyses indicate negative allometry
between relative phalangeal length (as reflected by phalangeal indices) and body mass, except for the pollex and
hallux. Thus, as size increases, there is a significant
decrease in the relative length of the digits when considering all prosimian taxa sampled. Regression analyses
show that while the digital portion of the rays scales isometrically with body mass, the palmar/plantar portion of
the rays often scales with positive allometry. Some but
not all of these broadly interspecific allometric patterns
remain statistically significant when effective degrees of
freedom are taken into account. As is often the case in
interspecific scaling, comparisons within families show
different scaling trends in the cheiridia than those seen
across families (i.e., lorisids, indriids, and lemurids exhibit rather different allometries). The interspecific pattern of positive allometry that appears to best characterize the metapodials of prosimians, especially those of the
foot, parallels differences found in the morphology of the
volar skin. Indeed, relatively longer metapodials appear
to covary with flatter and more coalesced volar pads,
which in turn slightly improve frictional force for animals that are at a comparative disadvantage while
climbing because of their larger mass. Despite the essentially isometric relationship found between digit length
and body mass across prosimians, examination of the residual variation reveals that tarsiers and Daubentonia
possess, relative to their body sizes, remarkably long fingers. Such marked departures between body size and finger length observed in these particular primates are
closely linked with specialized modes of prey acquisition
and manipulation involving the hands. Am J Phys
Anthropol 133:828–840, 2007. V 2007 Wiley-Liss, Inc.
Body size is among the most fundamental variables
influencing diversity of design in primates (Fleagle, 1985,
1999). The size of a primate species not only dictates what
it can afford to eat in order to survive (Kay, 1975, 1984),
but it also imposes mechanical challenges to its positional
abilities in an arboreal environment (Napier, 1967;
Cartmill, 1974, 1979, 1985; Jungers, 1977, 1978, 1979,
1984, 1985). Extant prosimians (i.e., strepsirrhines and
tarsiers) are no exception to these size constraints; the
largest taxa are roughly 100 times larger than the smallest (Smith and Jungers, 1997; Table 1).
Prosimian primates show very diverse dietary adaptations. The nature of this diversity is intimately linked
with body size, with smaller taxa feeding primarily on
insects and other prey, and the larger taxa feeding primarily on fruits, leaves, and other plant matter (Hladik,
1979; Kay, 1984; Oxnard et al., 1990; Fleagle, 1999).
Charles-Dominique (1975, 1990) suggested that these dietary differences had a profound impact on variation in
hand shape among prosimians. He argued that small-bodied, insectivorous prosimians have relatively longer and
more divergent fingers compared with larger, more vegetarian taxa, in order to increase the likelihood of catching
a moving prey when striking it with the hands.
Likewise, the positional repertoire of prosimian primates is also very diverse and includes spectacular locomotor behaviors such as ‘‘vertical clinging and leaping’’
(VCL) (Napier and Walker, 1967; Walker, 1974, 1979;
Gebo, 1987; Anemone, 1990; Oxnard et al., 1990; Fleagle,
1999). At least four different prosimian families with widely
different body masses (e.g., galagids vs. indriids) have been
categorized as vertical clingers and leapers (Napier and
Walker, 1967; Fleagle and Anapol, 1992; Demes et al.,
1996). Although smaller and larger VCL prosimians
This article has been modified since its original publication on 5 March 2007.
WILEY-LISS, INC.
C 2007
V
C
Grant sponsor: National Science Foundation; Grant number:
SBR-9318750.
*Correspondence to: Dr. Pierre Lemelin, Division of Anatomy, 505A Medical Sciences Building, Faculty of Medicine and Dentistry,
University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
E-mail: plemelin@med.ualberta.ca
Received 18 July 2006; accepted 15 December 2006
DOI 10.1002/ajpa.20586
Published online 5 March 2007 in Wiley InterScience
(www.interscience.wiley.com).
829
SCALING OF PROSIMIAN HANDS AND FEET
TABLE 1. Body mass data for extant prosimians and study sample
Taxon
Galagidae
Galago senegalensis
Galago moholi
Galagoides demidoff
Galagoides alleni
Euoticus elegantulus
Otolemur crassicaudatus
Otolemur garnettii
Lorisidae
Arctocebus calabarensis
Perodicticus potto
Loris tardigradus
Nycticebus coucang
Daubentoniidae
Daubentonia madagascariensis
Cheirogaleidae
Microcebus murinus
Cheirogaleus medius
Cheirogaleus major
Lepilemuridae
Lepilemur leucopus
Lepilemur mustelinus
Indriidae
Avahi laniger
Propithecus verreauxi
Propithecus diadema
Indri indri
Lemuridae
Eulemur mongoz
Eulemur macaco
Eulemur fulvus
Varecia variegata
Lemur catta
Hapalemur griseus
Tarsiidae
Tarsius spectrum
Tarsius syrichta
Tarsius bancanus
Body massa (g)
GM mean
Sample size
213
180
61
273
274
1,150
764
3.07
2.93
2.06
3.34
3.51
4.96
5.13
(0.33)b
(0.20)
(0.16)
(0.10)
(0.19)
(0.48)
(0.34)
13
7
10
3
10
9
7
309
1,030
230
857
3.13
5.84
2.78
4.70
(0.30)
(0.65)
(0.33)
(0.40)
10
13
11
14
2,555
7.32 (0.41)
9
61
180
400
1.72 (0.15)
2.49 (0.15)
3.58 (0.41)
14
6
7
605
777
4.26 (0.17)
5.36 (0.20)
7
5
1,025
3,550
6,100
6,335
5.56
8.00
9.80
10.13
(0.38)
(0.77)
(0.36)
(0.40)
10
12
6
7
1,485
1,820
2,040
3,575
2,210
710
6.30
7.08
6.54
8.25
6.77
4.92
(0.67)
(0.52)
(0.64)
(0.46)
(0.64)
(0.19)
7
7
12
10
12
10
2.59 (0.19)
2.39 (0.12)
2.46 (0.17)
2
10
10
116
126
122
GM, geometric mean of four midshaft diameters of long bones used as a body mass surrogate (see text for further details).
a
All body mass data are from Smith and Jungers (1997).
b
Values in parentheses indicate SDs.
all exhibit a relatively high percentage of leaping from
vertical supports, they vary substantially in their take-off
and landing styles, flight postures, kinetics, as well as
limb kinematics during leaping (Hall-Craggs, 1965; Jouffroy and Gasc, 1974; Peters and Preuschoft, 1984; Jouffroy and Günther, 1985; Dunbar, 1988; Demes and
Günther, 1989; Günther et al., 1991; Crompton et al.,
1993; Demes et al., 1995, 1996, 1999). From a morphological standpoint, it has been suggested that larger VCL
taxa have relatively shorter digits and well-differentiated
thumbs compared with smaller ones, because of sizerelated constraints (Napier and Walker, 1967; Walker,
1974).
Several functional hypotheses based on covariation patterns between body size, lifestyle, and cheiridial proportions have been proposed for promisian primates.
Although differences in cheiridial shape and proportions
are well documented for prosimians (Lessertisseur and
Jouffroy, 1973; Jouffroy and Lessertisseur, 1978, 1979;
Jouffroy et al., 1991), these differences remain difficult to
interpret functionally, mainly because the scaling basis of
such proportions (indices) are unknown. Despite the number of studies on the relationship between body size and
limb proportions or long bone geometry in prosimian
primates (Jungers, 1977, 1978, 1979, 1980, 1985; Demes
and Günther, 1989; Demes and Jungers, 1989, 1993;
Demes et al., 1991; Ravosa et al., 1993; Runestad, 1994;
Terranova, 1995; Runestad Connour et al., 2000), none has
focused specifically on the scaling trends in the hands and
feet in this group (however, see Lawler (2006) for a recent
ontogenetic study in Propithecus verreauxi). The objective
of this study is twofold: first, we examine the association
between body mass (BM) and cheiridial proportions for a
large sample of extant prosimians. We then investigate
scaling relationships between body mass and each ray element (i.e., metacarpals, metatarsals, and digits) for the
same prosimian sample, in order to ‘‘dissect’’ our indices
and, thereby, better understand how proportions change
within each ray. These data are critical for assessing the
mechanical benefits of certain cheiridial proportions that
have been linked with specific food acquisition strategies or
locomotor modes. This is especially important in the context
of reconstructing the mode of life of extinct primates.
MATERIALS AND METHODS
Sample
Ray elements of both hands and feet, as well as associated humeri and femora, were measured on 270 skeletal
American Journal of Physical Anthropology—DOI 10.1002/ajpa
830
P. LEMELIN AND W.L. JUNGERS
specimens housed in various American and European
institutions, totaling 30 species from all strepsirrhine
families and tarsiers (Table 1). All specimens measured
were adults, and most were wild-shot (>95%). Ray measurements consisted of lengths of the metapodials (i.e.,
metacarpals and metatarsals) and digits (proximal and
middle phalanges). Pollical and hallucal digits included
lengths of both proximal and distal phalanges. Herein,
the term ‘‘ray’’ refers to any given metapodial plus associated digit of the hand or foot.
Body mass variable and scaling model
Body mass is the obvious variable of choice for studying
scaling effects on postcranial features, because of its
direct relationship with gravitational forces and other factors affecting the locomotor system (Cartmill, 1974, 1979;
McMahon, 1975; Schmidt-Nielsen, 1975, 1984; Pedley,
1977; Alexander et al., 1979; Biewener, 1983, 1990, 2003;
Jungers, 1984, 1985, 1988, 1991a,b; Schaffler et al., 1985;
Bou et al., 1987; Ruff, 1987; Bertram and Biewener, 1990;
Demes et al., 1991; Jouffroy et al., 1990; Demes and
Jungers, 1993; Jungers and Burr, 1994; Christiansen,
1999a,b, 2002; Andersson, 2004; Garcia and da Silva,
2004). Unfortunately, body mass is rarely available for museum specimens, and surrogate measures can complicate
any analysis of allometry: ‘‘Substitute measures for body
weight . . . often scale nongeometrically with body weight
and can lead, therefore, to erroneous interpretations of
skeletal allometry and proportionality’’ (Jungers, 1985, p
351). We used body mass averages from the literature
(Smith and Jungers, 1997).
Recently, Demes et al. (1991) and Demes and Jungers
(1993) reported that body mass is highly correlated with
midshaft diameters of the humerus and femur in prosimians. In our study here, anteroposterior and mediolateral diameters at midshaft were measured on the humerus
and femur; the geometric mean (GM) of all four measurements was computed to obtain a body mass surrogate for
each specimen. Using species averages from Table 1, it was
found that the GM scales with slight but statistically significant positive allometry (slope ¼ 0.366; r ¼ 0.99; Fig. 1).
Accordingly, slope values presented here relative to the GM
are necessarily conservative estimates (i.e., they should be
slightly lower than they would be relative to body mass).
The selection of a size variable is also a very important
step, because the null hypothesis of isometry (or geometric similarity) is always tested with reference to a specified size variable (Mosimann and James, 1979; Jungers,
1985). If geometric similarity obtains, then for objects of
different volume (i.e., *body mass), length is proportional
to the volume following a 1:3 ratio and area follows a 2:3
ratio. Maintenance of these proportions with size changes
is referred to as isometric scaling, whereas a departure
(either negative or positive) from these isometric proportional changes is termed allometric scaling (SchmidtNielsen, 1984; Jungers, 1985; LaBarbera, 1989; Biewener,
2003). In simpler terms, isometric scaling indicates that
there is no significant change in shape; allometry implies
that shape changes in concert with size changes. Shape
change can be diagnosed with either log-log regressions
or by correlations between size and shape (cf. Mosimann
and James, 1979).
Indices and statistical methods
A phalangeal index similar to that used by Napier
(1993) was computed to obtain an estimate of the degree
Fig. 1. Log-log bivariate plot of body mass (g) (data from
Smith and Jungers, 1997) and GM (geometric mean of four midshaft diameters used as a body mass surrogate) (mm) for 30
prosimian species. Each symbol represents species mean values.
of prehensility for each ray of the hand and foot. The phalangeal index has been proven useful to differentiate
ground-dwelling taxa from fine-branch specialists with
greater grasping abilities among closely related mammal
groups like didelphid marsupials and raccoons (Lemelin,
1996b, 1999; Lemelin and Grafton, 1998; Lemelin and
Schmitt, 2007), and has been used to reconstruct grasping
and prehensile capabilities in Archaeolemur, a subfossil
lemur from Madagascar (Jungers et al., 2005). Longer
proximal and middle phalanges relative to the metapodials enable the digital portion of the ray to encircle a
branch or a food object following muscle contraction, thus
providing a firm, prehensile grip (Lemelin, 1996b, 1999;
Lemelin and Grafton, 1998; Lemelin and Schmitt, 2007).
For the pollex and hallux, the indices correspond to the
sum of the length of proximal and distal phalanges divided by the corresponding metapodial (3100). For the
other rays, the indices correspond to the sum of the length
of proximal and middle phalanges divided by the corresponding metapodial (3100). The distal phalanges could
not be included, because they were often missing or disarticulated from museum specimens.
Species means were computed for all indices, and these
were log-transformed (ln) to produce log shape variables
(Mosimann, 1970). Then, the degree of association
between size and shape was evaluated using correlation
methods (Mosimann and James, 1979). Under such methodology, a coefficient of correlation (r) equal to 0 indicates
isometry, one significantly less than 0 indicates negative
() allometry, and one significantly greater than 0 indicates positive (+) allometry. Kendall’s (s) and Spearman’s
(rs) coefficients of rank correlation were used to test the
null hypothesis of isometry between each phalangeal
index and body mass (BM) and the aforementioned GM.
American Journal of Physical Anthropology—DOI 10.1002/ajpa
SCALING OF PROSIMIAN HANDS AND FEET
Fig. 2. Log-log bivariate plots of phalangeal indices (%) for
manual (a) and pedal (b) rays I and GM (geometric mean of four
midshaft diameters used as a body mass surrogate) (mm) in prosimians. Each symbol represents species mean values.
Following correlational analyses of the phalangeal indices, each index was ‘‘dissected’’ by examining the relationship between the species mean of a ray element length
(i.e., metapodial and digit lengths) and the size variables
(BM and GM species means). Scaling was evaluated
within a geometric similarity model with the following
null hypotheses:
(1) length of a ray element a BM0.33
(2) length of a ray element a GM1.0
Following transformation of the raw data into natural logarithms (ln) after computation of species means for all ray
elements, model II regressions using reduced-major axis
(RMA) techniques were performed for each ray element and
the size variable. For each regression, 95% confidence intervals were calculated following Jolicoeur and Mosimann
(1968). Positive or negative allometry was observed if the isometric expectation (slope ¼ 0.33 for body mass; slope ¼ 1.0
for GM) was not included in these 95% confidence intervals.
In addition, using 3,000 bootstraps with replacement, 95%
confidence intervals were again calculated for comparison to
those computed by parametric algorithms.
Phylogenetic constraints and correction methods
Consideration of the phylogenetic relationships among
the species under investigation must be an integral part
831
Fig. 3. Log-log bivariate plots of phalangeal indices (%) for
manual ray III (a) and pedal ray IV (b) and GM (geometric mean
of four midshaft diameters used as a body mass surrogate) (mm)
in prosimians. Each symbol represents species mean values.
to any analysis of comparative data (Felsenstein, 1985;
Harvey and Pagel, 1991; Nunn and Barton, 2000, 2001).
The method of independent contrasts is the most commonly used, and many recent studies in primate morphology have incorporated it (Ross et al., 2004; Heesy, 2005;
Vinyard and Hanna, 2005). However, such an analysis
requires well-sorted phylogenetic relationships and a realistic topology. Although significant progress has been
made in establishing phylogenetic relationships among
strepsirrhine primates (DelPero et al., 1995, 2000, 2001;
Yoder et al., 1996; Yoder, 1997; Yoder and Irwin, 1999;
Pastorini et al., 2001a,b, 2002, 2003; Masters and Brothers, 2002; Masters et al., 2005), reliable branch lengths
remain insecure or unknown in many cases; we prefer not
to set them arbitrarily as ‘‘equal’’ throughout the phylogeny. Moreover, the outgroups for strepsirrhines (i.e., tarsiers) and for Malagasy lemurs (i.e., ayes-ayes) have
among the most derived and specialized hands in terms of
morphology and use, and this produced enormous contrasts in our initial exploratory analyses. These had profound leverages on all regressions, and it seemed too
ad hoc to us to simply discard them. For these reasons,
we elected instead to carry out comparisons within each
one of five strepsirrhine families having more than two
genera and showing differences in body mass (i.e., Galagidae,
Lorisidae, Cheirogaleidae, Indriidae, and Lemuridae).
RMA regression slopes and correlations were calculated
American Journal of Physical Anthropology—DOI 10.1002/ajpa
832
P. LEMELIN AND W.L. JUNGERS
TABLE 2. Values for the Kendall’s (s) and Spearman’s (rs)
coefficients of rank correlation between ln phalangeal indices (%)
and ln BM (g), and type of scaling for each bivariate comparison
Phalangeal
index
Hand
Ray
Ray
Ray
Ray
Ray
Foot
Ray
Ray
Ray
Ray
Ray
Rho, (rs)
(Nspecies ¼ 30;
Neff ¼ 13)
Tau, (s)
(Nspecies ¼ 30;
Neff ¼ 13)
Scaling
Ia
II
III
IV
V
0.072ns
0.601**;*
0.669**;*
0.659**;*
0.653**;*
0.049ns
0.454**;ns
0.505**;*
0.532**;*
0.495**;*
Isometry
–
–
–
–
I
II
III
IV
V
0.357*;ns
0.487**;ns
0.538**;ns
0.625**;*
0.613**;*
0.233ns
0.325*;ns
0.371**;ns
0.412**;ns
0.417**;ns
Isometry
–
–
–
–
Neff, sample size adjusted for phylogenetic effects (Smith, 1994;
see text).
–, negative allometry.
ns, not significant; *P 0.05; **P 0.01.
a
Comparison excludes Daubentonia (see text).
in log space (ln) between mean ray element lengths and
the size variables (BM and GM means) for each one of the
five families, to assess whether the scaling trends were
similar to those observed when the entire prosimian sample was considered. We also calculated ‘‘effective’’ sample
sizes (Neff) to estimate degrees of freedom and confidence
intervals following Smith (1994), by using variance components at different taxonomic levels (i.e., infraorder,
superfamily, family, genus, and species).
RESULTS
Rank-order correlations
When manual and pedal phalangeal indices and size
variables were compared, an inverse or negative association was observed for most of these indices (Figs. 2 and 3;
Tables 2 and 3). The association was stronger when mean
body mass was considered instead of the size surrogate
(GM). Most of the coefficients of rank-order correlation
(rs) were significantly different from zero (P < 0.05), even
when degrees of freedom based on Neff were considered,
indicating negative allometry for some of the ray indices
(Tables 2 and 3). Thus, as size increases, it appears that
there is a proportional decrease in most of the manual
and pedal phalangeal indices (Figs. 2 and 3; Tables 2 and
3). In contrast, as size increases, phalangeal indices for
the pollex and hallux clearly do not change very much or
predictably (i.e., isometry obtains) (Figs. 2 and 3; Tables 2
and 3).
Regressions
Most metapodials are characterized by similar scaling
patterns. In four metacarpals and all metatarsals, the
lower bound of the 95% confidence intervals of the RMA
slopes (both analytical and bootstrapped) does not include
the 1.0 value of isometry when mean body mass and the
size surrogate are considered (Figs. 4 and 5; Tables 4 and
5). This pattern of positive allometry is sustained for two
metacarpals and four metatarsals when 95% confidence
intervals based on Neff for mean body mass are considered
(Table 4). Thus, as body increases, the length of the meta-
TABLE 3. Values for the Kendall’s (s) and Spearman’s (rs)
coefficients of rank correlation between ln phalangeal indices (%)
and ln GM (mm), and type of scaling for each bivariate comparison
Rho, (rs)
(Nspecies ¼ 30;
Neff ¼ 13)
Tau, (s)
(Nspecies ¼ 30;
Neff ¼ 13)
Scaling
Ia
II
III
IV
V
0.060ns
0.580**;*
0.641**;*
0.635**;*
0.621**;*
0.039ns
0.421**;ns
0.485**;ns
0.476**;ns
0.458**;ns
Isometry
–
–
–
–
I
II
III
IV
V
0.374ns
0.477**;ns
0.553**;*
0.632**;*
0.623**;*
0.232ns
0.297*;ns
0.388**;ns
0.421**;ns
0.434**;ns
Isometry
–
–
–
–
Phalangeal
index
Hand
Ray
Ray
Ray
Ray
Ray
Foot
Ray
Ray
Ray
Ray
Ray
Neff, sample size adjusted for phylogenetic effects (Smith, 1994;
see text).
–, negative allometry.
ns, not significant; *P 0.05; **P 0.01.
a
Comparison excludes Daubentonia (see text).
carpals and metatarsals increase faster than predicted on
the basis of geometric similarity alone.
Manual and pedal digits are characterized by similar
scaling patterns that are different from those reported for
the metapodials (Figs. 4 and 5; Tables 4 and 5). The values of the 95% confidence limits of the RMA slopes for
most digits include the isometric value of 1.0 (Tables 4
and 5), and without exception are isometric when Neff is
used in the calculation of the 95% confidence intervals. In
other words, as body size increases, the length of these
digits increases absolutely but not relatively.
As might be expected, comparisons at the family level
show scaling trends that are not uniform across groups and
which depart from those observed when the entire prosimian sample is considered. However, because species
means are used, and due to the small number of species
within each family, confidence intervals are necessarily
huge and essentially meaningless in attempt to determine
whether slope values are isometric or allometric. As a
result, slope values for each ray element of each one of five
prosimian families (i.e., galagids, lorisids, cheirogaleids,
indriids, and lemurids) are reported without confidence
intervals (Tables 6 and 7), and only broad scaling trends are
highlighted. The ray elements of galagids and cheirogaleids
scale in a manner similar to that we reported for all prosimians: the values of the slopes for most of the metapodials
are higher than those of the corresponding digits. Also,
slope values for most ray elements are lower than those
reported for the whole prosimian sample. Lorisids show
reverse scaling trends for both hands and feet; slope coefficients are higher for the digits than the metapodials. Slope
values for most digits of lorisids are considerably higher
than those found for the whole prosimian sample. All pedal
digits of indriids and selected manual and pedal digits of
lemurids show a similar scaling pattern to that of lorisids;
higher slope coefficients for the digital portion of the ray
than the metapodial portion. All digits of indriids have
higher slope values when compared to those of the whole
prosimian sample. Finally, it is worth mentioning the much
higher slope coefficients for the first metacapal and associated digit of indriids compared to other prosimians.
American Journal of Physical Anthropology—DOI 10.1002/ajpa
SCALING OF PROSIMIAN HANDS AND FEET
Fig. 4. Log-log bivariate plots of metacarpal III (a) and manual digit III (b) lengths (mm) and GM (geometric mean of four
midshaft diameters used as a body mass surrogate) (mm) in prosimians. Each symbol represents species mean values.
DISCUSSION
Both hands and feet appear to display similar trends as
body size increases across all prosimian primates. Manual
and pedal rays II through V are characterized by similar
scaling patterns. For most of these rays, there is an
inverse association between their degree of prehensility
(as reflected by the phalangeal indices) and body size.
Thus, as size increases, there is a predictable decrease in
the phalangeal index for each ray that probably translates
into different grasping abilities. In contrast, there is no
predictable association between the degree of prehensility
of the pollex and hallux and changes in body size. In other
words, as size increases, the prehensile capabilities of the
manual and pedal first ray remain more or less the same.
Lemelin (1996b) examined associations between variation in manual phalangeal indices and specific ranks
according to dietary differences (i.e., degree of faunivory
vs. frugivory/folivory) and locomotion (i.e., preference for
quadrupedalism vs. VCL). Within-family comparisons
revealed that small-bodied strepsirrhines like Microcebus
murinus and Galagoides demidoff are characterized by
hands with longer fingers relative to the palm compared
to their larger, more frugivorous relatives (Lemelin,
1996a,b). Behaviorally, these smaller and more faunivorous prosimians catch prey with rapid strikes from one or
both hands (Bishop, 1964; Charles-Dominique, 1990;
833
Fig. 5. Log-log bivariate plots of metatarsal IV (a) and pedal
digit IV (b) lengths (mm) and GM (geometric mean of four midshaft diameters used as a body mass surrogate) (mm) in prosimians. Each symbol represents species mean values.
Lemelin, 1996a,b). In contrast to the overall proportional
trends, comparisons within families and between taxa of
similar body size showed little or no association between
manual phalangeal indices and the proportion of quadrupedalism vs. VCL adopted in the positional repertoire.
Two different scaling patterns underlie the observed
variation in cheiridial proportions among prosimians of
various body sizes. Several metacarpals and most metatarsals display positive allometry, whereas the corresponding digits scale isometrically. Thus, as size increases,
the phalangeal indices decrease in value because of this
proportional decoupling between the palmar/plantar and
digital portions of the rays. Although the precise interpretation of scaling patterns (i.e., dissection of indices) and
their statistical significance vary depending on whether
or not effective sample size is used, one important finding
holds up: across prosimians as a group, the values of the
RMA slopes for metacarpals and metatarsals are always
noticeably higher than those of associated digits. Disproportional scaling between the palmar/plantar and digital
elements of the rays is apparent and pervasive.
These broad interspecific scaling trends did not obtain
within lorisids, and were mixed in indriids and lemurids.
In lorises, the digital portion of each manual and pedal
ray scales with a greater slope than that of the corresponding metapodials. Thus, as body size increases, the
digits get relatively longer compared to the palm and sole.
The pollex and hallux of lorises are widely divergent from
American Journal of Physical Anthropology—DOI 10.1002/ajpa
834
P. LEMELIN AND W.L. JUNGERS
TABLE 4. Reduced major axis scaling of ln ray element
lengths (mm) to ln BM (g)
TABLE 5. Reduced major axis scaling of ln ray
element lengths (mm) to ln GM (mm)
95% CIs include
isometry?
95% CIs include
isometry?
Ray element
Slope
Intercept
r
Nspecies ¼ 30
Neff ¼ 13
Ray element
Slope
Intercept
r
Nspecies ¼ 30
Neff ¼ 13
HM1
HD1a
HM2
HD2
HM3
HD3
HM4
HD4
HM5
HD5
FM1
FD1
FM2
FD2
FM3
FD3
FM4
FD4
FM5
FD5
0.359
0.358
0.415
0.421
0.425
0.388
0.433
0.392
0.473
0.407
0.395
0.371
0.432
0.387
0.423
0.348
0.439
0.326
0.449
0.354
0.096
0.240
0.128
0.143
0.056
0.638
0.164
0.706
0.550
0.364
0.256
0.374
0.048
0.372
0.144
0.854
0.023
1.148
0.120
0.761
0.91
0.92
0.89
0.78
0.92
0.85
0.94
0.90
0.96
0.93
0.94
0.96
0.94
0.94
0.94
0.95
0.94
0.93
0.95
0.94
Yes
Yes
No
Yes
No
Yes
No
Yes
No
No
No
Yes
No
No
No
Yes
No
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
No
Yes
Yes
Yes
No
Yes
No
Yes
No
Yes
No
Yes
HM1
HD1a
HM2
HD2
HM3
HD3
HM4
HD4
HM5
HD5
FM1
FD1
FM2
FD2
FM3
FD3
FM4
FD4
FM5
FD5
0.980
0.977
1.133
1.148
1.159
1.060
1.182
1.071
1.291
1.110
1.078
1.012
1.180
1.056
1.155
0.951
1.198
0.890
1.228
0.967
0.765
1.098
0.867
1.152
0.962
1.568
0.874
1.646
0.584
1.339
1.202
1.263
1.084
1.300
1.159
1.689
1.076
1.930
0.958
1.610
0.92
0.94
0.91
0.80
0.93
0.88
0.95
0.93
0.97
0.95
0.95
0.97
0.95
0.95
0.95
0.97
0.95
0.95
0.96
0.96
Yes
Yes
Yes
Yes
No
Yes
No
Yes
No
Yes
Yes
Yes
No
Yes
No
Yes
No
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
H, hand; F, foot; M, metapodial; D, digit; r, correlation coefficient; 95% CIs, 95% confidence intervals on the slope value.
Neff, sample size adjusted for phylogenetic effects (Smith, 1994;
see text).
a
Comparison excludes Daubentonia (see text).
the lateral digits, and the second manual digit is reduced,
thereby contributing to the pincer-like, ‘‘hyperectaxonic’’
appearance of their cheiridia (Forster, 1933, 1934; Biegert,
1961; Jouffroy and Lessertisseur, 1977, 1979; Jouffroy
et al., 1991; Lemelin, 1996b; Fig. 6a). The largest lorisid,
Perodicticus potto, has pushed this morphological condition to an extreme by having the highest manual and
pedal phalangeal indices for rays I, IV, and V and the
smallest for ray II (Lemelin, 1996b). Relatively longer digits may contribute to gripping power and competence in
heavier prosimians. Interestingly, naturalistic data indicate that pottos can climb and grip relatively large supports for their body size (Charles-Dominique, 1971, 1974,
1977; Fig. 6a). With their relatively longer digits, the feet
of larger indriids appear to have evolved similar functional trends. Indeed, the foot of indriids is characterized
by a widely divergent hallux separated from the lateral
digits by a deep cleft, allowing it to span widely and grasp
larger diameter supports compared to a lemurid foot of
similar size (Gebo and Dagosto, 1988). Similarly, the hand
of larger indriids is characterized by a wide span between
the pollex and lateral digits, allowing grasping of large diameter supports (Jouffroy et al., 1991; Lemelin, 1996b;
Fig. 6b). In all our comparisons, we found the highest
scaling coefficient in the first metacarpal of indriids, probably underlying very strong positive allometry of the pollex as a whole. This disproportion in relative length of the
pollex is obvious when comparing the hand of the smaller
Avahi to the larger Propithecus and Indri (see Jouffroy
et al., 1991, p 290).
Scaling of metapodials and
functional implications
When all prosimians are considered as a group, it
appears that most metapodials scale allometrically with
H, hand; F, foot; M, metapodial; D, digit; r, correlation coefficient; 95% CIs, 95% confidence intervals on the slope value.
Neff, sample size adjusted for phylogenetic effects (Smith, 1994;
see text).
a
Comparison excludes Daubentonia (see text).
body size. The observation that large-bodied prosimians
appear to have absolutely and relatively longer palms and
soles compared to small-bodied taxa appears to have a
functional corollary. One potential explanation can be
found in the differences that characterize the volar skin
of primates of varying body size. Small-bodied prosimians
possess more convex, discrete, and protuberant volar
pads, whereas large-bodied taxa have flatter and coalesced pads (Whipple, 1904; Biegert, 1961; Cartmill, 1979;
Fig. 7). Among closely related groups, such as cheirogaleids, galagids, and lorisids, a similar trend can be found as
well (Biegert, 1961; Cartmill, 1979; personal observations).
Most primates rely on the frictional force of the volar
skin of their prehensile extremities to keep from slipping
when climbing (Cartmill, 1974, 1979, 1985; Lemelin,
2000; Hamrick, 2003). However, because the volar skin
behaves like a soft viscoelastic polymer, the force of friction is not directly proportional to the normal load, but
rather to a fractional exponent less than 1.0 (Cartmill,
1974, 1979, 1985). Smaller primates can cling to a planar
surface oriented at steeper angles than can larger primates for this very reason (Cartmill, 1974, 1979, 1985).
Larger primates get less frictional force per unit load.
More convex and discrete volar pads that characterized
the cheiridia of small-bodied primates are also found in
other small mammals, such as didelphid marsupials,
rodents, and tree shrews, and probably represent primitive mammalian retentions (Whipple, 1904; Biegert, 1961;
Cartmill, 1974, 1985; Lemelin, 2000; Hamrick, 2003). In
contrast, large-bodied primates need flatter and more continuous volar pads in order to provide a broader and more
uniform traction surface. Friction is no longer independent of contact surface in elastic bodies, and the exponent
relating friction to force can be increased by decreasing
curvature of the surface (i.e., by transforming discrete
pads into larger coalesced surfaces) (Cartmill, 1979,
American Journal of Physical Anthropology—DOI 10.1002/ajpa
835
SCALING OF PROSIMIAN HANDS AND FEET
TABLE 6. Reduced major axis slopes and correlation coefficients (r) for ln ray element lengths (mm)
and ln BM (g) in five strepsirrhine families
Ray element
HM1
HD1
HM2
HD2
HM3
HD3
HM4
HD4
HM5
HD5
FM1
FD1
FM2
FD2
FM3
FD3
FM4
FD4
FM5
FD5
Galagidae
0.304
0.320
0.305
0.305
0.302
0.286
0.315
0.280
0.346
0.317
0.275
0.293
0.290
0.275
0.302
0.271
0.316
0.249
0.329
0.283
(0.93)
(0.87)
(0.95)
(0.94)
(0.95)
(0.94)
(0.94)
(0.90)
(0.93)
(0.92)
(0.97)
(0.95)
(0.98)
(0.95)
(0.98)
(0.95)
(0.98)
(0.92)
(0.98)
(0.93)
Lorisidae
0.255
0.335
0.402
0.475
0.414
0.491
0.414
0.443
0.450
0.547
0.183
0.334
0.293
0.452
0.345
0.473
0.338
0.374
0.345
0.416
Cheirogaleidae
(0.97)
(0.90)
(0.93)
(0.65)
(0.98)
(0.90)
(0.98)
(0.98)
(0.98)
(0.96)
(0.94)
(0.92)
(0.80)
(0.93)
(0.90)
(0.89)
(0.94)
(0.95)
(0.93)
(0.92)
0.406
0.365
0.371
0.331
0.364
0.308
0.362
0.307
0.389
0.338
0.377
0.377
0.392
0.359
0.353
0.314
0.361
0.275
0.366
0.335
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.98)
(0.99)
(0.98)
(0.99)
(0.98)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.97)
(0.99)
(0.96)
(0.99)
(0.98)
Indriidae
0.611
0.553
0.459
0.446
0.435
0.430
0.426
0.415
0.457
0.456
0.397
0.434
0.399
0.451
0.391
0.427
0.392
0.407
0.413
0.448
(0.98)
(0.97)
(0.92)
(0.96)
(0.94)
(0.96)
(0.94)
(0.96)
(0.94)
(0.97)
(0.98)
(0.99)
(0.97)
(0.99)
(0.97)
(0.98)
(0.97)
(0.99)
(0.97)
(0.99)
Lemuridae
0.415
0.381
0.470
0.529
0.409
0.393
0.401
0.361
0.385
0.472
0.236
0.220
0.307
0.362
0.281
0.319
0.247
0.287
0.242
0.365
(0.86)
(0.85)
(0.91)
(0.89)
(0.91)
(0.89)
(0.91)
(0.87)
(0.91)
(0.90)
(0.78)
(0.80)
(0.80)
(0.86)
(0.81)
(0.84)
(0.80)
(0.85)
(0.81)
(0.90)
H, hand; F, foot; M, metapodial; D, digit.
TABLE 7. Reduced major axis slopes and correlation coefficients (r) for ln ray element lengths (mm)
and ln GM (mm) in five strepsirrhine families
Ray element
HM1
HD1
HM2
HD2
HM3
HD3
HM4
HD4
HM5
HD5
FM1
FD1
FM2
FD2
FM3
FD3
FM4
FD4
FM5
FD5
Galagidae
0.929
0.981
0.933
0.935
0.924
0.877
0.965
0.857
1.060
0.970
0.842
0.898
0.886
0.840
0.923
0.832
0.967
0.763
1.007
0.867
(0.96)
(0.90)
(0.97)
(0.96)
(0.97)
(0.96)
(0.97)
(0.93)
(0.96)
(0.95)
(0.98)
(0.97)
(0.99)
(0.97)
(0.99)
(0.97)
(0.99)
(0.94)
(0.99)
(0.96)
Lorisidae
0.546
0.918
0.862
1.018
0.886
1.053
0.886
0.950
0.964
1.171
0.391
0.717
0.628
0.969
0.739
1.014
0.724
0.802
0.740
0.892
Cheirogaleidae
(0.99)
(0.94)
(0.92)
(0.61)
(0.99)
(0.92)
(0.99)
(0.99)
(0.99)
(0.98)
(0.95)
(0.96)
(0.81)
(0.90)
(0.90)
(0.88)
(0.95)
(0.96)
(0.94)
(0.92)
1.051
0.945
0.961
0.858
0.943
0.800
0.939
0.796
1.007
0.876
0.976
0.977
1.017
0.929
0.915
0.812
0.936
0.713
0.947
0.868
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.98)
(0.99)
(0.98)
(0.99)
(0.99)
Indriidae
1.698
1.220
1.370
1.225
1.320
1.202
1.276
1.205
1.403
1.270
1.220
1.334
1.225
1.370
1.202
1.312
1.205
1.250
1.270
1.376
(0.99)
(0.99)
(0.97)
(0.99)
(0.98)
(0.99)
(0.98)
(0.99)
(0.98)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
(0.99)
Lemuridae
1.085
0.996
1.227
1.382
1.069
1.028
1.046
0.942
1.005
1.223
0.616
0.575
0.802
0.947
0.748
0.834
0.646
0.751
0.633
0.954
(0.97)
(0.98)
(0.99)
(0.98)
(0.98)
(0.97)
(0.98)
(0.97)
(0.98)
(0.99)
(0.91)
(0.97)
(0.89)
(0.94)
(0.90)
(0.90)
(0.91)
(0.94)
(0.90)
(0.94)
H, hand; F, foot; M, metapodial; D, digit.
1985). It follows that size-related morphological changes
should be expected in the proportions of the hands and
feet. The interspecific results clearly indicate positive allometry for some of the metacarpals (IV–V) and all metatarsals (except metatarsal I). In other words, large-bodied
prosimians such as P. verreauxi possess absolutely and
relatively longer palms and soles than small-bodied prosimians like Cheirogaleus medius (Fig. 7). These allometric
differences appear to be linked with the flattening of the
volar pads in large-bodied prosimians. Relatively longer
metacarpals and metatarsals allow large-bodied prosimians to sport flatter and more coalesced volar pads,
which in turn allow them to compensate for frictional differences in comparison to smaller taxa when subtending
vertical supports with similar central angles (Cartmill,
1974, 1979, 1985). Although prosimians show strong differentiation in horizontal vs. vertical substrate preferen-
ces, climbing on vertical supports is a critical component
of the locomotor repertoire of most prosimians (Jungers,
1985). In this regard, the maintenance of gripping and
friction efficiency among climbing, clawless animals of different masses—independently of locomotor and postural
preferences (i.e., quadrupedalism vs. VCL)—was probably
a critical factor underlying the evolution of hand and foot
proportions among prosimian primates. More modest size
differences within families apparently do not require comparable changes in hand and foot morphology.
Scaling of digits and functional implications
When all prosimians are considered as a group, it
appears that the digits scale isometrically with body size.
However, when examining the residual scatter for manual
digits, two groups of prosimians form very distinctive
American Journal of Physical Anthropology—DOI 10.1002/ajpa
836
P. LEMELIN AND W.L. JUNGERS
Fig. 6. Video images of the hand of Perodicticus potto (a)
and Propithecus verreauxi (b) gripping a large vertical trunk.
Note the extreme degree of divergence between the pollex and
lateral digits in both primates, and dramatic reduction of the
second digit in the potto. Animals are not to scale.
clusters well above the regression line: tarsiers and
Daubentonia. The fact that tarsiers possess very long
fingers for their body size compared to strepsirrhines
agrees well that these nocturnal animals, unlike almost
any other primate, devote their entire feeding budget to
the capture of prey with their hands (Niemitz, 1979,
1984; MacKinnon and MacKinnon, 1980; Bearder, 1986;
Gursky, 2000). Naturalistic and laboratory studies have
shown that tarsiers strike prey swiftly with their hands
(Polyak, 1957; Niemitz, 1979, 1984; Lemelin, 1996a,b). A
substantial portion of the prey captured by tarsiers can
move quickly if chased (i.e., flying or hopping insects)
(Davis, 1962; Niemitz, 1984). Not surprisingly, an entire
sequence—when catching a moving cricket with the
hands—usually lasts between 0.03 and 0.1 s, from the
moment the hands begin to move from a retracted position on each side of the head to the point of contact with
the prey (Lemelin, 1996b). When striking a prey, one or
both hands are used with the fingers extended and
abducted at the metacarpophalangeal joints, thus maximizing the area covered by a hand at contact (Niemitz,
1984; Lemelin, 1996b). Using the analogy of a butterfly
net, one can easily conceive a close relationship between
digit elongation and hand area. In this regard, an argument can be made that the relatively longer fingers
Fig. 7. Volar skin morphology of the hand of Cheirogaleus
medius (a) and Propithecus verreauxi (b). Note the differences
in pad topography and body size between the two taxa. Scale
bars are 1 cm.
observed in tarsiers increase the area of the hand, thus
probably increasing the likelihood of catching an elusive
prey (Fig. 8a). As pointed by Niemitz (1979, 1984), this is
especially important for a nocturnal animal like Tarsius
bancanus that ambushes its victim by leaping onto it
from greater distances.
If tarsiers have disproportionally long manual digits,
then one might ask why other highly faunivorous prosimians such as small-bodied lorises do not show a similar
deviation from the regression line? Indeed, animal matter
makes up between 85 and 100% of the total diet of
Arctocebus and Loris (Petter and Hladik, 1970; CharlesDominique, 1971, 1974, 1977; Hladik, 1975, 1979;
Bearder, 1986; Nekaris and Rasmussen, 2003; Nekaris,
2005). However, the bulk of that faunivorous diet is made
of slow-moving prey such as caterpillars, beetles, ants,
and termites (Charles-Dominique, 1971, 1974, 1977;
American Journal of Physical Anthropology—DOI 10.1002/ajpa
SCALING OF PROSIMIAN HANDS AND FEET
837
Fig. 8. Video images of hand use during feeding behavior in Tarsius syrichta (a) and Daubentonia madagascariensis (b). Note
the very long fingers of the Philippine tarsier holding a prey (left) and the extremely long third digit of the aye-aye being used to
probe a mealworm out a tree trunk (right). Animals are not to scale.
Nekaris and Rasmussen, 2003; Nekaris, 2005). Recently,
Nekaris and Rasmussen (2003) and Nekaris (2005)
reported that Loris lydekkerianus prefers to catch prey
using single-handed grabs. Under laboratory conditions,
Lemelin (1996a,b) found that Loris tardigradus uses similar single-handed grips when grabbing live crickets.
Unlike Tarsius, Galago, and Microcebus, slender lorises
adopt a more deliberate stance when catching crickets,
with the entire striking event lasting between 0.3 and
several seconds from the moment the hand is retracted
next to the head to contact with the prey (Lemelin,
1996a,b). From these behavioral data, it is quite clear
that at least two different patterns of prey catching styles
and techniques exist among small-bodied prosimians: a
pattern typical of tarsiers, some galagos and Microcebus,
which involves faster strikes with both hands, and a
slower pattern found in Loris. These differences in prey
capture styles and techniques, combined with the degree
of faunivory, covary with relative length of the manual
digits (Lemelin, 1996a,b). Indeed, some of the longest
manual digits (and highest manual phalangeal indices)
are found in tarsiers, which use faster strikes with both
hands to capture prey and are entirely faunivorous.
Like tarsiers, the values for manual digits II through V
of Daubentonia also cluster very distinctly well above the
regression line. The fingers of the aye-aye are relatively
very long compared to other strepsirrhines. Unlike tarsiers, aye-ayes do not strike fast-moving prey with the
hands. Instead, Daubentonia probes and extracts grubs
from crevasses or holes using the third digit, which is
slender, very flexible, and capable of independent movement at the metacarpophalangeal joint (Erickson, 1991,
1994; Milliken et al., 1991; Lemelin, 1996b; Fig. 8b).
When searching for wood-boring insects, the aye-aye
relies on a very peculiar mechanism of finger percussion
involving digit III (Erickson, 1991, 1994; Milliken et al.,
1991; Lemelin, 1996b). This behavior, which involves
rapid tapping of the tip of digit III on the surface of a tree
trunk, has been linked to a specialized tactile/auditory
mechanism to locate grubs, as well as the channels created by these wood-boring invertebrates (Erickson, 1991,
1994). Although the exceptional length and shape of digit
III has been emphasized in many behavioral studies, it is
noteworthy to mention that the same elongation pattern
applies for all other digits, especially manual digit IV. As
observed in captive ayes-ayes, digit IV of the hand is used
often to scrape pulp and juice out of a fruit (Winn, 1989;
Goix, 1993; Lemelin, 1996b). Despite their extraordinary
length, the manual digits of the aye-aye do not hinder
quadrupedal locomotion, and grips vary depending on the
orientation of the substrate, and whether animals are
ascending or descending (Krakauer et al., 2002).
CONCLUSIONS
The hands and feet of prosimian primates as a group
are characterized by similar scaling patterns. For all rays,
with the exception of the pollex and hallux, there is an
inverse association between relative digit length (as
expressed by the phalangeal index) and body mass. This
pattern of negative allometry, which translates into relatively shorter fingers and toes as body mass increases, can
be explained by two different scaling patterns that appear
to typify different portions of the rays: (1) positive allometry of the length of several metacarpals and most metatarsals, and (2) isometry of digit length. Within family, trends
are different; one observes higher scaling coefficients for
the digits relative to the corresponding metapodials in lorises (all rays of the hand and foot), indriids (all rays of the
foot), and lemurids (selected rays of the hand and foot).
The pattern of positive allometry observed in the metapodials of prosimians closely matches morphological differences in volar skin. In effect, relatively longer metacarpals and metatarsals may allow large-bodied prosimians
to accommodate flatter and more coalesced volar pads,
which in turn, slightly increase the coefficient of static
friction while climbing a vertical support. The relatively
long manual digits of tarsiers and Daubentonia also
reflect the importance of dietary factors in the evolution
of hand proportions of some prosimian primates, as suggested by Charles-Dominique (1975, 1990). Relatively longer manual and pedal digits in larger lorises and indriids
appear to be functionally linked with the ability to grip
large vertical supports.
ACKNOWLEDGMENTS
The curators and staffs of the American Museum of
Natural History, Anthropologisches Institut und Museum
der Universität Zürich-Irchel, British Museum of Natural
History, Cleveland Museum of Natural History, Duke
University Primate Center, Field Museum of Natural History, Museum of Comparative Zoology, Harvard, Muséum
National d’Histoire Naturelle, Museum für Naturkunde
American Journal of Physical Anthropology—DOI 10.1002/ajpa
838
P. LEMELIN AND W.L. JUNGERS
der Humboldt Universität, National Museum of Natural
History, and Nationaal Natuurhistorisch Museum gave
much appreciated help and access to skeletal collections.
The Duke University Primate Center and its staff provided free access and invaluable help when filming prosimians under their care. PL thanks Brigitte Demes,
John Fleagle, and Susan Larson for their invaluable support and advice throughout all stages of this study, Carsten Niemitz for his hospitality in Berlin, access to several
rare tarsier specimens, and sharing his insights on tarsier
ecology and behavior, and Françoise Jouffroy for her
advice, extensive expertise of the primate hand, hospitality in Paris and access to extensive prosimian skeletal
collections. Judith Masters, Chris Vinyard, and Chris
Wall shared their wisdom on scaling, strepsirrhine phylogeny, and/or correction methods, and Tim Cole wrote
the program allowing the computation of RMA slopes and
confidence intervals. Three anonymous reviewers offered
very helpful comments on a previous draft of this paper.
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