Estimating body mass in New World “monkeys” (Platyrrhini, Primates), with a consideration of the Miocene platyrrhine, Chilecebus carrascoensis

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Estimating body mass in New World “monkeys” (Platyrrhini,Primates), with a consideration of the Miocene platyrrhine,Chilecebus carrascoensisAuthor(s): Karen E. Sears, John A. Finarelli, John J. Flynn, and André r WyssSource: American Museum Novitates, Number 3617:1-29. 2008.Published By: American Museum of Natural HistoryDOI: http://dx.doi.org/10.1206/627.1URL: http://www.bioone.org/doi/full/10.1206/627.1

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PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY

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Number 3617, 29 pp., 1 figure, 6 tables June 16, 2008

Estimating body mass in New World ‘‘monkeys’’(Platyrrhini, Primates), with a consideration of the

Miocene platyrrhine, Chilecebus carrascoensis

KAREN E. SEARS,1 JOHN A. FINARELLI,2,3 JOHN J. FLYNN,4 AND

ANDRE R. WYSS5

ABSTRACT

Well-constrained estimates of adult body mass for species of fossil platyrrhines (New World‘‘monkeys’’) are essential for resolving numerous paleobiological questions. However, noconsensus exists as to which craniodental measures best correlate with body mass among extanttaxa in this clade. In this analysis, we analyze 80 craniodental variables and generate predictiveequations applicable to fossil taxa, including the early platyrrhine Chilecebus carrascoensis.

We find mandibular length to be the best craniodental predictor of body mass. There is nosignificant difference in predictive value between osteological and dental measures. Variablesassociated with the mandible and lower dentition do significantly outperform the cranium andupper dentition. Additionally, we demonstrate that modern platyrrhines differ, morphometrically,from early fossil forms. Chilecebus possesses unusual cranial proportions in several key features, aswell as proportionally narrow upper incisors and wide upper cheek teeth. These variables yieldwidely divergent body mass estimates for Chilecebus, implying that the correlations observed in acrown group cannot be assumed a priori for early diverging fossils. Variables allometricallyconsistent with those in extant forms yield a body mass estimate of slightly less than 600 grams forChilecebus, nearly a factor of two smaller than prior preliminary estimates.

Scaled to body mass, the brain of Chilecebus is markedly smaller than those of modernanthropoids, despite its lowered body mass estimate advocated here. This finding, in conjunctionwith a similar pattern exhibited by fossil catarrhines, suggests that increased encephalization aroseindependently in the two extant subgroups of anthropoids (platyrrhines and catarrhines).

Copyright E American Museum of Natural History 2008 ISSN 0003-0082

1 Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801.2 Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109.3 University of Michigan Museum of Paleontology, Ann Arbor, MI 48109.4 Division of Paleontology, American Museum of Natural History, New York, NY 10024.5 Department of Geological Sciences, University of California- Santa Barbara, Santa Barbara, CA 93106.

INTRODUCTION

Motivated by the discovery of the well-preserved cranium of the early, fossil platyr-rhine (New World ‘‘monkey’’) Chilecebuscarrascoensis (Flynn et al., 1995), we exploremethods for estimating body mass in fossilplatyrrhine species from cranial morphomet-rics. Adult body mass is highly correlated witha diverse suite of ecological, macroevolution-ary, physiological, and life history variablesamong living mammals (Gittleman andHarvey, 1982; Schmidt-Nielsen, 1984; Gittle-man, 1986; Damuth, 1987; McNab and Eisen-berg, 1989; Gittleman, 1991, 1993; Gillooly etal., 2005). It follows that improved estimatorsof body mass for fossil taxa are essential tounderstanding the biology of extinct species(Gingerich and Smith, 1984; Martin, 1984;Damuth and MacFadden, 1990; Eisenberg,1990; Jungers, 1990). However, it remainsunclear which morphometric variables corre-late best with body mass among living mam-mals, let alone among fossil taxa. Previousattempts to estimate body mass from variousskeletal and dental proxies in anthropoidshave emphasized the Catarrhini (Old World‘‘monkeys’’ and hominoids) (e.g., Delson etal., 2000), rather than platyrrhines (Hills andWood, 1984; Conroy, 1987; Martin, 1990).Since the most reliable morphometric corre-lates of body mass are identified in the contextof comparisons to phylogenetically closelyrelated taxa (Eaglen, 1984; Conroy, 1987;Damuth and MacFadden, 1990; Dagostoand Terranova, 1992), we investigate theseassociations in platyrrhine primates.

There has been considerable research intovarious cranial, postcranial, and dental vari-ables as body mass estimators for extinctprimates (e.g., Gingerich, 1974; Gingerich etal., 1982; Gingerich and Smith, 1984; Bouvier,1986; Gingerich, 1990; Martin, 1990; Ruff,1990; Dagosto and Terranova, 1992; Spocterand Manger, 2007). While a particular vari-able’s reliability as an estimator of body massfor a fossil taxon depends on the strength ofthe correlation with body mass among extanttaxa, those variables that tend to performbetter in a statistical sense are not typically themost useful to paleobiologists. Limb bonemeasures generally correlate better with body

mass than do cranial or dental variables.These elements are rare as fossils, however,and when found as isolated elements can bedifficult to identify to low taxonomic levels(Damuth and MacFadden, 1990). The mostcommon primate fossils by far are isolatedteeth or jaws, elements that typically correlatewith body mass more poorly (Gingerich et al.,1982; but also see Dagosto and Terranova,1992).

Using morphometric proxies to estimatebody mass in fossil taxa requires the poten-tially problematic assumption that the allo-metric relationship between a given variableand body mass observed among living formsalso applies to fossil taxa. As an example,estimates of body mass from different mor-phometric variables for the early catarrhineAegyptopithecus yield widely varying results(Radinsky, 1977; Martin, 1990; Dagosto andTerranova, 1992; Simons, 1993). Thus, fossiltaxa might be characterized by fundamentallydifferent allometries of the skull and dentition;the more unusual these morphometries are,the more uncertain body size estimates (andderived indices such as encephalization quo-tients) become. In practice, such deviations aredifficult to identify because they require arobust and well-resolved phylogeny (of livingand fossil forms) and well-preserved andrelatively complete fossil material. To mini-mize these potential problems with a singleestimator, body mass estimates from severalproxies often are averaged (e.g., Radinsky,1971; Martin, 1990). This approach makes theoptimistic assumption that inaccuracies amongvariables offset one another, such that variablesyielding overestimates counterbalance thoseunderestimating mass.

To elucidate the pattern of increased en-cephalization (brain volume scaled to bodymass) among platyrrhines, we apply a suite ofcraniodental body mass estimators to the20.1 Ma fossil Chilecebus carrascoensis fromthe Abanico Formation of central Chile(Flynn et al., 1995). Represented by the best-preserved and -dated early primate skull fromSouth America, Chilecebus provides an excel-lent test case for application of these methods.The completeness and exceptional preserva-tion allow many of the proxy variables to be

2 AMERICAN MUSEUM NOVITATES NO. 3617

applied. Moreover, the antiquity of this fossilallows methods of estimating body mass inextinct taxa to be judged against the backdropof potentially significant evolutionary changein allometry.

METHODS

Variables, Specimens, and Body Mass Data

We assembled a suite of 80 morphometricvariables from the literature (Gingerich andSchoeninger, 1979; Radinsky, 1981a, 1981b,1982; Gingerich et al., 1982; Anthony andKay, 1993; Hartwig, 1993; Kobayashi, 1995).Appendix 1 lists measurement variables andtheir descriptions. Of these potential body massproxies, 32 were measurements of osteologicalfeatures on the cranium and mandible, while 48were measurements of the dentition. All teethexcept the third molars (which do not occur incallitrichines) were measured. Specimens ofextant taxa examined were from the collectionsof the Mammalogy Division, Zoology Depart-ment of the Field Museum of Natural History,and the Mammalogy Collections, Division ofVertebrate Zoology of the American Museumof Natural History. In total, 157 specimensrepresenting 17 platyrrhine species were mea-sured. Specimen numbers are given in appen-dix 2. Extant taxa were chosen to ensure asample containing at least one species from eachof the 15 platyrrhine genera and the full range ofbody sizes (from 13.5 kg for Brachyteles ara-chnoides to 125 grams for Callithrix pygmaea).Body mass data were obtained from the Massesof Mammals Database (v. 3.03: Smith et al.,2003). Average body masses used in theregression analysis are listed by species intable 1. In addition, we measured preservedmorphometric variables for the fossil taxonChilecebus carrascoensis (SGOPV 3213, MuseoNacional de Historia Nacional, Santiago,Chile). Mean measurement values for extanttaxa are given by species in appendix 3.

Allometric Regression Analyses

Morphometric variables and body masses forthe living platyrrhines were log-transformed(base 10) to determine allometric relationshipsbetween the variables and body mass. Speciesaverage masses were fit to species-average log-

variables using ordinary (Model 1) least-squaresregression (Sokal and Rohlf, 1995). Becausesimilarity in morphometry may arise from closephylogenetic relationship (Felsenstein, 1985),we performed phylogenetically corrected re-gressions (Garland and Ives, 2000), which wereexecuted in the PDAP (Midford et al., 2003)module for the Mesquite software package(Maddison et al., 2002, 2004). Phylogeneticrelationships among extant taxa were obtainedfrom molecular phylogenies of the Platyrrhini(Canavez et al., 1999; von Dornum and Ruvolo,1999) (figure 1). Slopes and intercepts describ-ing the relationship between the morphologicpredictor and body mass were calculated foreach variable.

To assess a variable’s efficacy in predictingbody mass, we quantified the relative perfor-mance among estimators using the log-likeli-hood fit of each regression model to the data:

LnL ! {1

2nLn

ESS

n

� �

Burnham and Anderson, 2002ð Þ:

In the equation, n is the sample size, and ESSis the error sum of squares of the regression;therefore, the regression likelihood is propor-tional to its ability to minimize residualvariance. Model log-likelihoods were rescaled

TABLE 1

Body mass for measured extant platyrrhine speciesMasses given in grams, from Smith et al. 2003.

Genus Species Mass [g]

Alouatta caraya 5862.5

Aotus vociferans 873.0

Ateles geoffroyi 5284.9

Brachyteles arachnoides 13499.9

Cacajao melanocephalus 3800.0

Cacajao calvus 5796.0

Callicebus moloch 854.7

Callimico goeldii 480.0

Callithrix pygmaea 125.0

Callithrix jacchus 292.0

Cebus apella 2500.0

Chiropotes satanas 3000.0

Lagothrix lagotricha 6300.0

Leontopithecus rosalia 535.5

Pithecia pithecia 1375.5

Saguinus mystax 618.0

Saimiri sciureus 743.2

2008 SEARS ET AL.: ESTIMATING BODY MASS IN NEW WORLD ‘MONKEYS’ 3

such that the maximum value across allvariables was 0, with poorer predictors havingprogressively more negative log-likelihoods(Edwards, 1992). We employed a log-likeli-

hood difference of 2 (Edwards, 1992; Royall,1997; Wagner, 2000a, 2000b) as the cutoff foridentifying one variable as a significantlybetter predictor of body mass than another.

Fig. 1. Cladogram from molecular phylogenies (Canavez et al., 1999; von Dornum and Ruvolo, 1999) ofplatyrrhine primates used in the phylogenetically corrected regressions of body mass on morphometricvariables. This cladogram is a synthetic topology of these two phylogenetic analyses. The topologies for thetwo analyses were congruent for overlapping taxa, with two exceptions. First the Callicebus/Cacjao/Chiropotes/Pitehca clade was basal to all other Platyrrhini in von Dornum and Ruvolo (1999), but was alliedwith the Ateles/Bachyteles/Lagothrix/Allouata clade in Canavez et al. (1999). Second, Aotus was allied withSaimiri and Cebus in Canvez et al. (1999), but left in an unresolved polytomy in von Dornum and Ruvolo(1999). Therefore both nodes are conservatively left in polytomies here.


Body Mass Estimation in Chilecebus

The body mass of the fossil platyrrhineChilecebus carrascoensis was estimated from46 measurements preserved in SGOPV 3213,the holotype cranium, using the regressionequations generated above from living taxa.We calculated a weighted average of theseestimates using the proportional likelihoods foreach regression model over the set of all models(Burnham and Anderson, 2002). Model aver-aging is appropriate when there is no clearlyidentifiable ‘‘correct’’ model. This method hasbeen employed to a limited extent in previouswork (e.g., Radinsky, 1971; Martin, 1990),where the mass estimates from several proxieswere averaged to reduce errors associated withany single predictor. However, simply calculat-ing the mean of the individual variableestimates implicitly assumes that all of thevariables perform equally well in predictingbody mass. Since regression model likelihoodsquantify an individual variable’s relative pre-dictive ability, a more appropriate averagingtechnique takes advantage of this information.Using proportional likelihoods, poorly per-forming models influence the final body massestimate less, whereas better fitting modelsmore strongly influence the final estimate.

Estimating Relative Brain Size in Chilecebus

X-ray computed tomographic scans of theChilecebus carrascoensis cranium were per-formed on the medical scanner at Children’sHospital of San Diego (CT HiSpeed AdvSYS#HSA1; 140 Kv, 170 mA) to estimateendocranial volume (Flynn et al., 1995). Theskull and surrounding matrix were embedded inmodeling clay to better mimic the density of thehuman body, and scanned at 1.0 mm resolution.The series of individual axial and transverse scanslices were composited into 3-D images usingCemax VIP softwareE (Freemont, CA). Theresulting brain volume measure was used inconjunction with body mass estimates to deter-mine the relative brain volume in Chilecebus.

To determine whether increased encephali-zation observed in extant anthropoids wasinherited from their last common ancestor, orwhether New and Old World anthropoidprimates evolved this trait independently,log-encephalization quotients (logEQs) were

calculated for the extant catarrhine andplatyrrhine taxa considered in Martin (1990).The encephalization quotient (EQ) is the ratioof observed brain volume to expected brainvolume for a given body mass (Jerison, 1970;Radinsky, 1971). The metric of interest,however, is not relative volume but deviationof observed volume from the allometricregression of brain volume on body mass,i.e., the natural logarithm of the EQ (logEQ)(Marino et al., 2004; Finarelli and Flynn,2007; Finarelli, 2008). Positive logEQs implylarger than expected brain volumes for a givenbody mass, and negative values the opposite.To assess the relative brain volume for extantplatyrrhines and the extinct taxon Chilecebus,we used the allometry relating body mass tobrain volume for strepsirrhine primates (as anoutgroup to anthropoids) given in Martin(1990) as a frame of reference.

RESULTS AND DISCUSSION

Body Mass Estimators

We performed phylogenetically correctedregression of body mass on each of the 80morphometric variables for the extant taxa.Slopes and intercepts for the predictive equa-tions and the corresponding log-likelihoodsfor the phylogenetically corrected regressionsare given for each variable in table 2; scatter-plots for the regressions are given in appen-dix 4. The relative ability of the morphometricvariables surveyed in this analysis to accurate-ly predict body mass, as measured by the log-likelihood fits for the regressions, is highlyuneven. The maximum likelihood observedamong the variables is for mandibular length,indicating that this variable is the single bestpredictor of body mass among the 80 variablessurveyed. Only one variable (pterygoid-zygo-matic length) had a log-likelihood fit within2LnL units of mandibular length, and there-fore, there is no significant difference in theability of those two variables to predict bodymass among extant platyrrhine species.

The two optimal predictors are both cra-niomandibular, osteological measurements,not dental variables. Teeth are frequentlyemployed as body mass predictors for fossilmammals (Gingerich, 1974; Legendre, 1986;Legendre and Roth, 1988) because of their


TABLE 2

Regressions of body mass on morphometric variables for extant taxaSlopes and intercepts of predictive equations for phylogenetically corrected regressions for each measurementvariable (appendix 1) in living platyrrhines sampled (table 1). Also given are R2, error sum of squares (ESS)and the log-likelihood (LnL), rescaled such that the maximum likelihood observed among models (mandibularlength) is 0. Measurement regressions are ordered in decreasing LnL. Teeth are upper (U) or lower (L) lengths,

widths (anterior or posterior for molars), and areas.

Measurement Slope Intercept R2 ESS LnL

Mandibular length 2.689 21.349 0.636 0.117 0.000

Pterygoid-zygomatic length 2.268 0.210 0.592 0.135 21.136

Bizygomatic width 2.828 21.616 0.626 0.166 22.783

Moment arm of the masseter 1.672 0.916 0.510 0.175 23.225

LM1L 2.205 1.822 0.449 0.195 24.077

Skull length 3.123 22.720 0.537 0.196 24.105

Temporal fossa length 3.202 22.233 0.374 0.198 24.193

LM1A 1.136 1.856 0.431 0.202 24.371

Moment arm of the temporalis 1.760 1.434 0.434 0.213 24.786

Mandibular height 2.016 1.010 0.516 0.215 24.841

LM2A 1.056 1.942 0.375 0.232 25.470

Foramen magnum width 3.339 20.253 0.387 0.232 25.474

LP3L 1.767 2.419 0.374 0.234 25.535

LM1WPos 2.187 1.955 0.350 0.239 25.716

Bulla width 2.939 0.302 0.327 0.241 25.781

Occipital width 2.488 20.525 0.315 0.242 25.803

LM1WAnt 2.269 1.968 0.353 0.244 25.864

Condyle Width 2.614 2.008 0.447 0.244 25.879

Cheek tooth row, upper 1.982 0.653 0.273 0.244 25.880

Cheek tooth row, lower 2.054 0.471 0.359 0.245 25.885

Facial height (length) 2.299 20.075 0.532 0.248 26.003

Foramen magnum area 1.483 0.199 0.277 0.249 26.015

LP3A 0.893 2.340 0.323 0.249 26.018

Braincase width 3.086 21.814 0.551 0.250 26.070

LP4L 1.935 2.265 0.325 0.251 26.083

LP4A 0.980 2.192 0.303 0.251 26.099

LP2L 1.760 2.395 0.506 0.252 26.118

LM2WPos 1.952 2.109 0.356 0.252 26.134

LM2WAnt 2.259 1.952 0.419 0.253 26.169

Temporal chord 3.246 21.778 0.183 0.255 26.229

UP3L 1.866 2.326 0.306 0.261 26.396

UP4L 2.028 2.220 0.313 0.262 26.438

LM2L 1.957 1.960 0.496 0.263 26.452

Braincase length 2.792 21.345 0.288 0.270 26.678

LP2A 0.844 2.355 0.456 0.272 26.724

UP3A 0.932 2.138 0.275 0.273 26.764

UP2W 1.752 2.117 0.384 0.274 26.783

UP4A 1.015 2.009 0.267 0.277 26.893

Palate length 2.025 0.388 0.394 0.281 26.985

UP2A 0.877 2.254 0.422 0.287 27.170

LP3W 1.704 2.316 0.412 0.296 27.408

LP4W 1.830 2.205 0.209 0.297 27.450

Foramen magnum height 2.476 0.754 0.264 0.303 27.598

UM1A 1.080 1.747 0.399 0.309 27.743

UP3W 1.782 2.006 0.383 0.309 27.758

UM1L 2.078 1.875 0.393 0.310 27.793

UM2WAnt 2.212 1.674 0.398 0.311 27.813

UP4W 1.964 1.847 0.199 0.311 27.813

UM2WPos 2.046 1.799 0.397 0.312 27.826


higher preservation potential. However, den-tal measurements are generally considered tobe less reliable estimators than osteologicalvariables (including measurements of thepostcranium) (Gingerich et al., 1982; Dagostoand Terranova, 1992), potentially reflectingspecialized adaptations to unusual diets/fooditems or unusual food-processing methods(Gingerich and Smith, 1984). To test this as-sumption, we partitioned the data into osteo-logical (both cranium and mandible), anddental (both upper and lower) splits.

Eight of the 10 best predictors in thisanalysis are osteological (table 2): mandibularlength, pterygoid-zygomatic length, bizygo-matic width, moment arm of the masseter,skull length, temporal fossa length, momentarm of the temporalis, and mandibular height.Among these, both mandibular length andpterygoid-zygomatic length exceed the best

dental variable by at least 2 LnL units. Whileosteological features include the best predic-tors of body mass, they also include the threeworst predictors: vault height, orbital width,and pterygoid length. Further, a Mann-Whitney test (Sokal and Rohlf, 1995) recoversno significant difference in the median ranklog-likelihood scores across osteological anddental partitions (U 5 656, p . 0.05). Thus,while median log-likelihood for the osteolog-ical variables is slightly higher than that ofdental variables (26.45 versus 27.60), thevariance of log-likelihoods for osteologicalvariables also is higher. Thus, while the bestpredictors are osteological, among platyrrhineprimates osteological characters do not uni-versally outperform dental ones.

Among dental variables, the best predictorof body mass is lower M1 length (table 2), acommonly used proxy for body mass in

Measurement Slope Intercept R2 ESS LnL

UM2A 0.955 1.965 0.395 0.313 27.858

Palate width 1.830 1.034 0.400 0.315 27.908

UM1WAnt 2.157 1.676 0.378 0.318 27.998

Masseteric fossa length 1.778 0.544 0.291 0.320 28.027

Maxillary incisor size 2.476 0.525 0.286 0.322 28.086

LP2W 1.527 2.373 0.350 0.323 28.102

UP2L 1.683 2.427 0.353 0.323 28.118

UM2L 1.677 2.186 0.353 0.331 28.315

UC1L 1.497 2.293 0.459 0.333 28.355

UM1WPos 2.130 1.695 0.326 0.344 28.624

LC1L 1.403 2.527 0.328 0.349 28.728

UC1W 1.310 2.351 0.296 0.366 29.116

UI2L 1.900 2.341 0.240 0.381 29.432

Postorbital constriction 3.056 21.526 0.234 0.395 29.720

UI2W 1.584 2.394 0.293 0.418 210.176

Bulla length 2.383 0.061 0.181 0.425 210.308

Condyle length 2.493 0.950 0.094 0.430 210.398

Frontal chord 2.163 20.202 0.446 0.431 210.409

LC1W 1.178 2.436 0.188 0.434 210.469

Vertical face height 1.808 0.683 0.357 0.440 210.585

Occipital chord 2.033 0.687 0.111 0.456 210.877

LI2W 1.569 2.340 0.111 0.480 211.284

UI1L 1.660 2.295 0.059 0.488 211.407

Parietal chord 2.852 21.035 0.089 0.499 211.591

LI1L 1.670 2.692 0.230 0.500 211.601

LI1W 1.427 2.489 0.141 0.515 211.847

UI1W 1.417 2.391 0.243 0.535 212.150

LI2L 1.511 2.663 0.025 0.540 212.216

Skull vault height 1.723 0.573 0.006 0.558 212.479

Orbit width 1.791 0.885 0.003 0.610 213.192

Basal length of pterygoid fossa 0.928 2.093 0.092 0.646 213.655

TABLE 2

(Continued )


mammals (Van Valkenburgh, 1990; Janis etal., 1998a, 1998b). Lower M1 area, anothercommonly used proxy (Gingerich, 1974;Legendre, 1986; Legendre and Roth, 1988;Finarelli and Flynn, 2006), was the next bestestimator and was not significantly differentthan lower M1 length (LnL difference 50.298). As noted above, the distribution oflog-likelihoods for dental variables was lessdispersed than the distribution for osteologicalvariables. Eight dental measures (as opposedto two osteological) were within 2 LnL unitsof the optimal dental score. However, amongthese, only upper cheek tooth row length wasfrom the upper dentition. A Wilcoxon signed-rank test performed on 24 upper/lower pairsof dental measurements demonstrates thatvariables from the lower dentition significant-ly outperform their upper dentition counter-parts as predictors of body mass (W 5 160, p, 0.05).

Thus, regression model likelihoods demon-strate: 1) that the single best predictor ismandibular length, and 2) that the lowerdentition significantly outperforms the upperdentition in predicting body mass. Thus, itappears that predictors associated with themandible may outperform those of the crani-um among extant platyrrhines. To test this,log-likelihoods were separated into mandibu-lar and cranial partitions, rather than osteo-logical (including the mandible) and dental(including both upper and lower) partitions.Median mandibular log-likelihoods were high-er than cranial log-likelihoods (26.12 versus27.81), a significant difference (Mann-Whitney test, U 5 519, p , 0.05).

Intraspecific variability must be a concernwhen evaluating evolutionary allometriesthrough species mean values. Platyrrhines,and primates in general, are sexually dimorphic(Martin et al., 1994), a feature that leads to arange of variance that is discounted whenaveraging over species. When estimating bodymass for fossil taxa allometries must use speciesaverages. Sex identification for fossil mammalsgenerally is not possible, except in rareinstances (e.g., Coombs, 1975; Fleagle et al.,1980; Krishtalka et al., 1990; Van Valkenburghand Sacco, 2002). This is due to the fact thatfossil taxa are often known from a limitednumber of specimens and rarely represent a

population sample for a species. It is thereforedifficult to rigorously evaluate sexual dimor-phism or other forms of intraspecific variation.However, large degrees of within-species vari-ation can negatively impact the precision ofprediction allometries.

More troublesome would be if there were atendency for the range of variation to increaseor decrease as a function of body mass (e.g.,Rensch’s rule: Rensch, 1950). To assess thispotential impact of intraspecific variation onmodel estimates for extant Platyrrhini, wecalculated the difference between log-trans-formed maximum and minimum values for the17 species, yielding an observed proportionalrange (table 3). This range was not calculatedfor Brachyteles due to its low sample size. Theobserved intraspecific proportional rangesaverage approximately 14% of the totalobserved variation across all taxa. In addition,there is no association between the percentageof total range that the proportional rangerepresents, and the major variable partitions.Mann-Whitney tests (Sokal and Rohlf, 1995)comparing osteological/dental splits (U 5 641,p . 0.05) and mandibular/cranial splits (U 5818.5, p . 0.05) were not significant. We alsoregressed observed proportional range againstthe species average body mass for each taxon.For each measurement variable, a t-test forthe slope of the regression (Sokal and Rohlf,1995) was not significant; regression slopesranged from 20.073 to 0.066 with a medianvalue of 0.013. Therefore, proportional rangesdo not vary as a function of species body size.

Body Mass Estimates for Chilecebus

One of the main objectives in derivingmorphometric proxies for body mass amongextant taxa is to apply the predictive equationsto fossil taxa. Here we apply the body massproxies derived above to the fossil platyrrhineChilecebus carrascoensis (Flynn et al., 1995).The only known specimen of this taxon (a skull,SGOPV 3213) lacks the mandible, and ptery-goid-zygomatic length (the second best predic-tor variable) could not be measured. There are,however, 46 measurements that can be evaluat-ed on this nearly complete skull. Of these, 24variables are osteological and 22 dental. Bodymass estimates derived from these variables


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cep

ha

lus;

Ci_

mo

lo,

Ca

llic

ebu

sm

olo

ch;

Cl_

go

el,

Ca

llim

ico

go

eld

ii;

Cx

_ja

cc,

Ca

llit

hri

xja

cch

us;

Cx

_p

yg

,C

all

ith

rix

py

gm

aea

;C

e_ap

el,

Ceb

us

ap

ella

;C

h_

sata

,C

hir

op

ote

ssa

tan

as;

La

_la

go

,L

ag

oth

rix

lag

otr

ich

a;

Le_

rosa

,L

eon

top

ith

ecu

sro

sali

a;

Pi_

pit

h,

Pit

hec

iap

ith

ecia

;S

g_

my

st,

Sa

gu

ina

sm

yst

ax

;S

m_

sciu

,S

aim

iri

sciu

reu

s.

Sp

ecie

sA

l_ca

raA

o_v

oci

At_

geo

fC

a_

calv

Ca

_m

ela

Ci_

mo

loC

l_g

oel

Cx

_ja

ccC

x_

py

gC

e_ap

elC

h_

sata

La

_la

go

Le_

rosa

Pi_

pit

hS

g_

myst

Sm

_sc

iu

Sk

ull

L0

.18

00

.03

60

.07

80

.04

50

.05

10

.05

40

.08

70

.04

80

.04

30

.05

00

.03

70

.03

70

.04

20

.09

90

.02

40

.05

1

Occ

W0

.13

90

.13

30

.09

60

.05

80

.04

10

.05

80

.10

20

.08

90

.04

20

.13

70

.12

30

.080

0.0

73

0.0

69

0.0

70

0.0

46

Co

nd

L0

.17

80

.11

10

.24

90

.10

90

.08

80

.12

10

.14

60

.11

40

.14

40

.08

60

.20

40

.14

00

.10

50

.08

60

.07

00

.09

6

Co

nd

W0

.24

90

.13

10

.17

40

.23

20

.18

40

.23

00

.24

40

.20

10

.17

20

.21

30

.16

10

.19

70

.10

70

.15

90

.33

60

.22

1

Fo

rH

0.1

81

0.1

04

0.0

85

0.1

80

0.0

70

0.0

92

0.1

59

0.1

21

0.1

40

0.1

41

0.0

58

0.1

60

0.1

15

0.1

09

0.0

74

0.1

51

Fo

rW

0.2

13

0.0

85

0.0

92

0.0

90

0.0

46

0.0

40

0.0

72

0.1

12

0.1

05

0.1

35

0.0

88

0.0

88

0.0

62

0.0

92

0.1

04

0.0

82

Fo

rP

0.3

69

0.1

62

0.1

32

0.1

91

0.0

70

0.1

09

0.2

09

0.1

86

0.2

23

0.2

48

0.1

08

0.2

24

0.1

35

0.1

34

0.1

65

0.1

59

Pte

ryL

0.3

28

0.3

44

0.3

39

0.1

26

0.0

34

0.3

42

0.1

12

0.0

89

0.1

64

0.2

68

0.0

87

0.0

98

0.0

95

0.1

72

0.1

16

0.1

21

Pte

r-zy

0.2

36

0.1

23

0.2

18

0.0

73

0.0

83

0.1

57

0.0

92

0.1

50

0.0

78

0.1

32

0.0

98

0.1

64

0.1

23

0.1

73

0.1

02

0.1

04

Bu

lL

0.1

74

0.0

80

0.1

15

0.1

13

0.1

01

0.0

96

0.1

89

0.0

65

0.1

26

0.0

79

0.1

28

0.2

09

0.0

67

0.0

71

0.0

87

0.0

69

Bu

lW

0.1

69

0.1

38

0.1

72

0.0

55

0.0

80

0.1

61

0.0

93

0.1

01

0.1

05

0.0

94

0.0

75

0.1

20

0.0

55

0.0

78

0.1

18

0.1

09

OC

ho

rd0

.17

80

.18

60

.16

10

.12

40

.10

60

.15

20

.12

60

.21

70

.14

00

.12

50

.12

60

.10

20

.19

80

.12

40

.04

10

.10

8

Ca

seW

0.1

96

0.0

25

0.0

65

0.0

24

0.0

24

0.0

42

0.0

59

0.0

59

0.0

31

0.0

54

0.0

40

0.0

44

0.0

22

0.0

52

0.0

30

0.0

27

Tem

pL

0.1

91

0.0

66

0.0

95

0.0

55

0.0

67

0.0

91

0.0

67

0.0

46

0.0

45

0.0

59

0.0

39

0.0

36

0.0

44

0.0

58

0.0

73

0.0

61

PO

Co

n0

.21

70

.05

10

.07

40

.04

60

.02

70

.06

20

.07

40

.05

50

.03

40

.07

40

.05

20

.06

10

.03

80

.02

90

.04

00

.03

3

Zy

go

W0

.22

80

.03

20

.07

90

.05

60

.05

70

.04

60

.07

20

.04

00

.07

00

.11

20

.02

60

.06

40

.06

80

.14

50

.05

30

.09

1

Ca

seL

0.2

36

0.0

82

0.0

67

0.0

44

0.0

38

0.0

69

0.0

83

0.0

52

0.0

60

0.0

46

0.0

31

0.0

43

0.0

34

0.0

69

0.0

59

0.0

68

FC

ho

rd0

.21

10

.05

10

.24

90

.09

00

.05

60

.09

00

.16

20

.06

90

.06

50

.13

30

.12

80

.06

50

.12

80

.09

10

.08

40

.10

4

PC

ho

rd0

.28

10

.13

30

.19

40

.10

20

.08

70

.09

90

.20

90

.04

00

.06

70

.21

40

.11

70

.09

80

.07

20

.11

10

.09

00

.03

0

Va

ult

H0

.22

30

.25

50

.05

50

.03

50

.06

30

.07

60

.10

50

.11

60

.03

80

.07

50

.06

20

.04

30

.08

50

.07

30

.08

10

.07

6

Orb

W0

.50

50

.02

70

.06

60

.06

70

.04

90

.06

30

.08

80

.02

80

.06

90

.07

20

.05

80

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0.0

43

0.0

69

0.0

64

0.0

74

Fa

cH

0.2

94

0.1

32

0.1

21

0.1

34

0.0

83

0.0

97

0.1

57

0.0

85

0.1

43

0.0

78

0.1

09

0.1

92

0.0

79

0.1

66

0.0

78

0.0

55

Ver

tH

0.2

19

0.1

40

0.0

88

0.2

19

0.0

62

0.0

87

0.1

46

0.0

89

0.1

05

0.1

11

0.0

98

0.1

28

0.0

74

0.1

73

0.1

00

0.0

75

TC

ho

rd0

.22

40

.12

00

.05

60

.08

90

.03

30

.09

60

.09

80

.05

70

.06

30

.10

60

.05

90

.06

30

.06

00

.08

30

.05

50

.05

6

Jaw

L0

.17

70

.02

80

.06

00

.05

30

.07

70

.05

10

.08

20

.05

60

.09

80

.07

60

.06

40

.073

0.1

01

0.1

51

0.0

39

0.0

78

Jaw

H0

.53

90

.14

70

.07

60

.17

10

.09

10

.16

50

.12

90

.12

20

.17

20

.17

20

.11

80

.149

0.1

37

0.1

38

0.0

60

0.1

90

MA

rmM

0.2

86

0.1

73

0.2

30

0.1

26

0.1

55

0.0

87

0.1

11

0.2

19

0.1

07

0.0

84

0.1

12

0.1

20

0.0

86

0.1

71

0.0

51

0.2

21

MA

rmT

0.4

94

0.1

80

0.1

74

0.1

08

0.1

05

0.1

25

0.1

23

0.1

93

0.1

52

0.0

86

0.2

60

0.1

71

0.1

41

0.2

34

0.1

34

0.1

00

Ma

ssL

0.2

36

0.1

46

0.1

44

0.1

14

0.0

62

0.1

31

0.1

27

0.0

82

0.1

11

0.1

28

0.0

61

0.1

04

0.1

27

0.1

66

0.0

73

0.1

20

UR

ow

L0

.16

80

.07

30

.06

40

.05

00

.02

20

.20

70

.17

20

.06

80

.04

30

.19

30

.08

90

.04

60

.09

90

.07

00

.08

10

.07

8

LR

ow

L0

.09

80

.06

10

.06

60

.05

50

.01

00

.15

60

.16

10

.05

70

.03

60

.04

10

.07

20

.06

40

.07

50

.05

70

.04

10

.10

8


TA

BL

E3

(Co

nti

nu

ed)

Sp

ecie

sA

l_ca

raA

o_

vo

ciA

t_g

eof

Ca

_ca

lvC

a_

mel

aC

i_m

olo

Cl_

go

elC

x_

jacc

Cx

_p

yg

Ce_

ap

elC

h_

sata

La_

lag

oL

e_ro

saP

i_p

ith

Sg

_m

yst

Sm

_sc

iu

Pa

lL

0.1

05

0.0

62

0.1

33

0.0

94

0.0

89

0.0

53

0.0

64

0.0

81

0.0

36

0.0

85

0.2

78

0.1

26

0.0

90

0.1

19

0.0

61

0.0

60

M1

Pa

lW

0.1

05

0.0

68

0.0

89

0.0

62

0.0

45

0.0

70

0.1

27

0.0

55

0.0

27

0.1

13

0.0

94

0.0

89

0.1

53

0.1

39

0.0

90

0.0

91

MIn

c0

.01

50

.07

50

.08

00

.09

40

.05

90

.09

00

.09

30

.08

60

.06

10

.04

70

.10

50

.085

0.0

68

0.0

74

0.0

69

0.0

84

UI1

W0

.18

40

.14

90

.10

40

.16

90

.06

10

.28

70

.16

10

.12

50

.18

00

.11

10

.11

00

.343

0.1

62

0.1

28

0.1

98

0.1

32

UI2

W0

.25

10

.06

00

.10

90

.10

90

.10

40

.17

30

.21

30

.14

90

.15

20

.13

50

.16

60

.421

0.1

35

0.2

19

0.0

68

0.1

07

UC

1W

0.2

85

0.0

62

0.3

40

0.1

48

0.0

71

0.1

36

0.1

89

0.1

45

0.1

46

0.0

98

0.0

86

0.2

21

0.4

10

0.2

72

0.0

82

0.2

66

UP

2W

0.1

17

0.0

75

0.2

72

0.0

85

0.1

43

0.0

56

0.2

00

0.0

93

0.1

05

0.0

71

0.0

91

0.1

12

0.1

71

0.2

58

0.0

70

0.0

63

UP

3W

0.0

96

0.0

39

0.2

47

0.1

22

0.0

86

0.0

88

0.2

23

0.0

71

0.1

06

0.0

54

0.1

46

0.0

68

0.1

39

0.1

38

0.0

75

0.0

51

UP

4W

0.1

45

0.0

55

0.2

30

0.0

50

0.1

19

0.0

94

0.2

29

0.0

84

0.0

55

0.0

55

0.1

66

0.0

71

0.1

35

0.1

16

0.0

44

0.0

62

UM

1W

10

.08

50

.08

70

.17

90

.04

50

.05

20

.08

20

.18

80

.09

20

.07

60

.06

50

.06

60

.11

20

.09

50

.11

10

.04

00

.13

1

UM

1W

20

.31

90

.08

50

.19

00

.03

80

.03

20

.09

00

.18

10

.10

10

.05

70

.06

50

.08

80

.08

50

.09

90

.14

00

.05

30

.07

5

UM

2W

10

.33

10

.11

30

.15

90

.04

70

.02

60

.07

30

.20

90

.06

60

.07

20

.03

60

.08

80

.08

00

.09

40

.07

50

.12

50

.06

0

UM

2W

20

.34

50

.13

70

.16

60

.06

60

.05

40

.07

60

.14

90

.09

90

.06

40

.05

00

.08

10

.10

90

.17

10

.06

60

.17

50

.09

9

UP

2L

0.1

38

0.1

14

0.1

53

0.0

80

0.0

98

0.2

45

0.1

24

0.0

84

0.2

05

0.1

24

0.1

15

0.0

97

0.0

92

0.1

21

0.1

90

0.1

07

UP

3L

0.2

36

0.0

71

0.1

34

0.0

87

0.0

43

0.1

37

0.1

80

0.0

71

0.1

14

0.0

72

0.1

01

0.0

96

0.0

86

0.1

20

0.1

10

0.0

66

UP

4L

0.2

68

0.1

04

0.1

03

0.1

10

0.0

36

0.1

37

0.1

11

0.0

76

0.2

21

0.0

42

0.0

62

0.0

61

0.1

53

0.0

99

0.0

68

0.0

72

UM

1L

0.1

91

0.0

79

0.1

16

0.0

97

0.0

47

0.1

04

0.0

73

0.0

36

0.1

06

0.0

64

0.0

57

0.0

66

0.0

49

0.0

69

0.0

53

0.0

35

UM

2L

0.0

79

0.0

62

0.1

44

0.1

13

0.0

73

0.0

59

0.0

97

0.0

58

0.1

20

0.0

58

0.0

74

0.0

59

0.2

08

0.0

64

0.1

48

0.0

59

UI1

L0

.10

20

.17

50

.12

60

.07

90

.08

10

.08

90

.16

10

.12

60

.15

70

.06

50

.09

40

.241

0.0

60

0.1

22

0.0

94

0.0

58

UI2

L0

.09

60

.07

60

.11

50

.20

40

.13

30

.16

60

.09

70

.10

50

.16

50

.14

80

.18

90

.175

0.0

83

0.2

02

0.0

78

0.0

69

UC

1L

0.2

22

0.1

74

0.2

68

0.1

54

0.0

97

0.1

56

0.1

65

0.1

24

0.1

74

0.0

79

0.1

69

0.1

56

0.1

90

0.2

11

0.1

22

0.1

08

LI1

W0

.10

20

.10

80

.16

60

.13

70

.17

00

.27

20

.24

30

.17

80

.11

50

.13

10

.25

20

.181

0.1

32

0.1

97

0.0

93

0.0

69

LI2

W0

.22

80

.11

80

.17

50

.06

30

.08

40

.26

50

.15

10

.18

50

.09

60

.06

40

.24

60

.221

0.1

16

0.2

18

0.0

90

0.1

29

LC

1W

0.2

27

0.0

79

0.2

98

0.1

45

0.1

64

0.1

04

0.2

12

0.1

68

0.2

39

0.1

53

0.0

97

0.1

39

0.2

87

0.3

12

0.1

58

0.1

19

LP

2W

0.2

02

0.0

55

0.2

92

0.1

60

0.1

13

0.1

19

0.0

88

0.0

76

0.1

37

0.0

89

0.1

51

0.0

92

0.1

44

0.2

28

0.0

97

0.1

20

LP

3W

0.1

23

0.0

70

0.3

36

0.0

51

0.0

65

0.1

40

0.0

70

0.0

84

0.1

59

0.0

59

0.0

95

0.0

94

0.0

80

0.2

32

0.1

70

0.0

72

LP

4W

0.1

31

0.0

64

0.3

52

0.0

48

0.0

72

0.0

53

0.1

56

0.0

63

0.1

59

0.0

64

0.0

85

0.0

84

0.0

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range widely, from about 85 grams (temporalislength) to approximately 1.7 kg (upper P4width), a greater than 20-fold difference inmaximum and minimum estimates (table 4).The arithmetic mean of these estimates is589 grams (table 4). Within the range ofestimates, osteological variables generally pro-duce lower estimates than do the dentalvariables; body mass estimates derived fromosteological variables range from 85 to1137 grams, with a mean of 494 grams, whereasdental variables yield a range from 374 to1725 grams, with a mean of 997 grams. Incontrast, the weighted average, which incorpo-rates the proportional likelihoods of the regres-sions to weight individual measurement esti-mates, yields an estimated body mass of319 grams (table 4), considerably lower thanthe simple mean. Notably the weighted averageis also lower than the minimum mass estimategenerated from the dental variables. Thus, whilethere is considerable overlap in body massestimates between the osteological and dentalpartitions, the weighted-average model demon-strates that the lower estimates are derived fromthe variables known to be more reliable bodymass indicators among extant taxa.

This broad range of body mass estimates forChilecebus is worrisome with regard to esti-mating body mass for fossil platyrrhines ingeneral. If these variables conform to the sameallometries in Chilecebus as are observedamong extant taxa, then all should yieldsimilar mass estimates. To the contrary, ourresults prove that at least some of thesevariables must scale differently in Chilecebusthan in modern platyrrhines. While this mightbe interpreted as hindering reliable body massestimation for Chilecebus, the allometric scal-ings observed among extant taxa must beassumed to hold for the fossil members of thegroup in any analysis of this kind. The largerange of estimated body masses for Chilecebusis by no means unique among extinct pri-mates; for example, body mass estimates forthe basal catarrhine Aegyptopithecus (Kay andSimons, 1980) also vary widely depending onthe morphometric proxy employed.

Flynn et al. (1995) originally estimated thebody mass of Chilecebus at 1.0–1.2 kg, basedon upper cheek tooth regressions across allprimates. They noted, however, an unusualS

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TABLE 4

Estimated body mass for Chilecebus carrascoensisEstimates based on morphometric proxies preserved in the holotype cranium. The first set of estimates are basedon all of the preserved measurements. The second set relates only the 20 measurements for which Chilecebusconforms to the extant allometry (see text). Individual measurement estimates are given, and their arithmetic mean ispresented at the bottom. Weighted estimates refer to a weighted average model using proportional likelihoods asmodel weights (see text). The sum of these represents the weighted average model and this is also given at the bottom.

Measurement LogL Weights

All Measurements Reduced Measurement Set

Body Mass

Estimate

Weighted

Estimate

Body Mass

Estimate

Weighted

Estimate

Skull length 1.046E-02 429.949 53.699 429.949 218.554

Occipital width 1.916E-03 1136.862 26.012 1136.862 105.869

Condyle length 1.934E-05 206.305 0.048 . .

Condyle width 1.775E-03 1007.406 21.355 . .

Foramen magnum height 3.183E-04 336.396 1.278 . .

Foramen magnum width 2.661E-03 865.273 27.492 . .

Foramen magnum area 1.549E-03 476.250 8.811 . .

Basal length of pterygoid fossa 7.447E-07 1040.611 0.009 1040.611 0.038

Bulla length 2.037E-01 317.039 0.080 . .

Bulla width 2.116E-05 100.113 2.341 . .

Occipital chord 1.959E-03 628.653 0.090 628.653 0.366

Braincase width 1.199E-05 444.242 7.782 444.242 31.672

Temporal fossa length 1.467E-03 84.945 9.721 . .

Postorbital constriction 9.584E-03 326.561 0.149 . .

Zygomatic arch width 3.812E-05 85.852 40.250 . .

Braincase length 3.926E-02 546.801 5.212 546.801 21.212

Frontal chord 7.982E-04 424.186 0.097 . .

Parietal chord 1.913E-05 729.496 0.051 729.496 0.208

Skull vault height 5.868E-06 882.893 0.025 882.893 0.104

Orbital width 2.415E-06 155.830 0.002 . .

Facial height (length) 1.184E-06 194.083 3.635 . .

Vertical face height 1.568E-03 455.752 0.087 455.752 0.356

Temporal chord 1.606E-05 564.098 8.423 564.098 34.281

Cheek tooth row, upper 1.250E-03 862.867 18.268 862.867 74.351

Palate width 6.346E-01 408.763 1.139 . .

UI1W 5.013E-03 975.584 0.039 975.584 0.159

UI2W 2.523E-02 1205.903 0.348 1205.903 1.416

UC1W 5.299E-03 1039.983 0.224 1039.983 0.911

UP2W 2.072E-04 1295.374 11.123 . .

UP3W 1.773E-03 1697.284 5.497 . .

UP4W 1.764E-03 1725.191 5.286 . .

UM1WAnt 5.876E-04 1566.878 3.991 . .

UM2WAnt 2.334E-04 1516.114 4.647 . .

UP2L 1.954E-04 650.189 1.469 650.189 5.977

UP3L 3.356E-06 681.960 8.620 681.960 35.084

UP4L 2.416E-05 665.608 8.069 665.608 32.840

UM1L 1.803E-05 554.851 1.736 554.851 7.064

UM2L 7.192E-04 866.640 1.607 866.640 6.540

UI1L 2.712E-04 374.210 0.032 . .

UI2L 2.566E-04 430.239 0.261 . .

UC1L 2.133E-04 774.311 1.380 774.311 5.617

UP2A 1.140E-04 897.992 5.234 . .

UP3A 2.567E-04 1075.035 9.403 . .

UP4A 2.532E-04 1070.204 8.231 . .

UM1A 1.892E-04 910.563 2.993 . .

UM2A 1.059E-03 1106.215 3.241 . .

Averaged Estimates 589.559 319.486 722.252 582.619


combination of morphological features inChilecebus, including a relatively small brain-case and the proportions of the upperdentition. Cranial osteological measures tendto produce lower body mass estimates than dodental variables for Chilecebus. However, doesthis imply that dental variables generallyoverestimate mass, or that the cranial osteo-logical metrics consistently underestimate it?To determine which measures scale uniquelyin Chilecebus relative to extant platyrrhines,we regressed all other variables preserved inChilecebus against skull length for the set ofextant platyrrhine species. This offers a way todescribe allometric differences between Chilecebusand the suite of extant platyrrhines. Regressionresiduals were calculated for Chilecebus andextant taxa relative to each variable’s allome-try; variables in which the Chilecebus residualwas greater than two standard deviations ofthat observed among the extant taxa wereconsidered variables in which Chilecebus devi-ates significantly from extant platyrrhine al-lometry for that variable.

The results of this analysis demonstrate thata unique morphometry relative to livingplatyrrhines explains the much heavier bodymass proposed in the initial description ofChilecebus. Flynn et al. (1995) noted thatChilecebus has proportionally wider upperpremolars and molars than extant primatesof the same skull length. Here, residuals for allupper cheek tooth widths in Chilecebus doexceed those in extant platyrrhines by morethan two standard deviations (table 5). Thus,upper cheek tooth widths (and areas derivedfrom them) will lead to overestimates of bodymass. Mesiodistal lengths of both upperincisors of Chilecebus are significantly lessthan in the extant regression, meaning thatthese variables produce underestimates ofbody mass (table 5). Several osteologicalcharacters in Chilecebus also deviate signifi-cantly from the modern allometries, including:foramen magnum height and width (and thearea derived from them), occipital condylelength and width, length and width of theauditory bullae, temporalis length, postorbitalconstriction, bizygomatic width, length of thefrontal chord, orbital width, facial height, andthe palatal width at M1 (table 5). All of theseare significantly shorter in Chilecebus than

predicted by modern allometries, and there-fore would yield underestimates of body mass.Thus, no simple pattern accounts for thediscrepancy between dental and cranial oste-ological variable-derived estimates of bodymass in Chilecebus, rather various individualvariables deviate from the modern allometries,and point to a fundamentally different skullform in Chilecebus relative to extant platyr-rhines (Flynn et al., 1995).

Even so, 20 variables from both theosteological and dental partitions do conformto modern allometries, and should, therefore,provide reliable estimates of body mass.Limiting estimates to those variables greatlynarrows the range of estimates: 430 to1206 grams, with an average value of722 grams (table 4). Excluding those measuresnot conforming to extant allometries elimi-nates both the extreme high and low bodymass estimates for Chilecebus (e.g., upper P3,upper P4 width, and anterior widths of theupper M1 and upper M2, all of which predictmasses . 1.5 kg; temporalis length, bizygo-matic width, and width of the auditory bullaepredicting masses # 100 grams). The reducedset of 20 measurements produces a weighted-average estimate of 583 grams (table 4). Weconsider this constrained weighted-average tobe the most reliable estimate of the body massfor Chilecebus, as this estimate is based onthose metrics that can be shown to conform tothe extant allometries and utilizes the relativereliabilities of predicting body mass in theextant taxa in weighting the impact of eachvariable upon the final estimate.

Relative Brain Size in Chilecebus

Flynn et al. (1995) noted the small braincaseof Chilecebus (7.46 cc, based on CT data), andsuggested that a low level of encephalizationmay characterize platyrrhines ancestrally.However, the initial body mass estimate forChilecebus based on upper cheek teeth (1.0–1.2 kg) is approximately double the 583 gramestimate from this analysis. We have shownthat upper cheek tooth widths overestimatebody mass in Chilecebus, and therefore theoriginal hypothesis of a relatively small brainin Chilecebus might simply reflect an inflatedbody mass estimate.


LogEQs for extant anthropoids, relative toa baseline allometry for strepsirrhine primates,show that extant catarrhines and platyrrhineshave relatively large brains. Both clades havesimilar distributions of logEQs; catarrhinelogEQs range from 1.39 to 2.25 (table 6:including hominoids, but not Homo sapiens),

extant platyrrhines from 1.54 to 2.44 (table 6),and they are indistinguishable with a Mann-Whitney test (U 5 47, p . 0.05). Althoughmodern anthropoids possess large brainsrelative to body mass compared to othermammals (Radinsky, 1973, 1977; Martin,1990), it is unclear whether this condition

TABLE 5

Measurements taken on the Chilecebus carrascoensis cranium, and their deviation from the extant allometries foreach measurement

Two standard deviations of the residuals of extant taxa around each allometry are given. Values in bold indicatemeasurements where Chilecebus falls more than two standard deviations from the regression line. Sign indicateswhether the measurement is anomalously large (+) or small (2) on Chilecebus, and therefore will over- or

underestimate body mass, respectively.

Measurement Chilecebus Residual 2 Standard Deviations Sign

Occipital width 0.065 0.147

Condyle length 20.231 0.080 2

Condyle width 0.100 0.090 +Foramen magnum height 20.125 0.112 2

Foramen magnum width 0.080 0.040 +Basal length of pterygoid fossa 0.026 0.171

Bulla length 20.120 0.095 2

Bulla width 20.233 0.079 2

Occipital chord 20.036 0.100

Braincase width 20.016 0.046

Temporal fossa length 20.255 0.068 2

Postorbital constriction 20.077 0.067 2

Zygomatic arch width 20.263 0.039 2

Braincase length 20.047 0.110

Frontal chord 20.117 0.088 2

Parietal chord 20.017 0.114

Skull vault height 20.038 0.139

Orbital width 20.170 0.116 2

Facial height (length) 20.172 0.044 2

Vertical face height 20.085 0.086

Temporal chord 0.005 0.066

Cheek tooth row, upper 0.104 0.141

Palate width 20.217 0.216 2

UI1W 0.023 0.145

UI2W 0.112 0.125

UC1W 0.077 0.175

UP2W 0.172 0.133 +UP3W 0.226 0.116 +UP4W 0.214 0.108 +UM1WAnt 0.177 0.117 +UM2WAnt 0.211 0.110 +UP2L 20.032 0.126

UP3L 0.010 0.109

UP4L 0.008 0.097

UM1L 20.022 0.143

UM2L 0.115 0.173

UI1L 20.215 0.128 2

UI2L 20.133 0.110 2

UC1L 20.006 0.148


typifies Anthropoidea ancestrally, or whether,as Kay et al. (1997) have suggested, Catarrhiniand Platyrrhini each evolved relatively largebrains in parallel. Martin (1990) analyzed 25living haplorhines (Anthropoidea plus tarsi-ers), demonstrating that living anthropoids arelarge-brained compared to strepsirrhine pri-mates relative to a ‘‘basal insectivores’’ refer-ence frame.

Tejedor et al. (2006) noted that the,16.4 Ma cebine platyrrhine Killikaike blakeipossesses a strongly vaulted frontal and largeanterior cranial fossa, suggesting an expandedforebrain early in cebine evolutionary history.Only the anterior portion of the skull ispreserved, thus a total brain volume cannotbe estimated, although enlarged forebrains docorrelate with relatively larger brains in ce-bines, suggesting that the brain of Killikaikewas likely quite large. Contemporaneous Euro-pean hominoids, however, lacked significantlyexpanded brains (Begun, 2002). Martin (1990)noted that several fossil haplorhines also hadmuch smaller brains than their extant relatives,including early ‘‘tarsioids’’ and the early catar-rhine Aegyptopithecus zeuxis (logEQs: 0.90–1.06, table 6). These fossil haplorhines havelarger brains than expected relative to thestrepsirrhine allometry, yet are below thesmallest calculated logEQ value for extantanthropoids. The constrained weighted-aver-age body mass model for Chilecebus (583grams) yields a logEQ of 1.11 (table 6), whichis comparable to encephalization values ob-served among contemporaneous haplorhines,but is lower than observed values in all extantanthropoids. The largest and smallest bodymass estimates for Chilecebus from the reducedset of measurements, 1206 grams and 430grams, yield logEQs of 0.62 and 1.32, respec-tively. Thus, only if the sole smallest reliablemorphometric proxy (of 20 estimators) iscorrect for Chilecebus would its estimatedencephalization even begin to approach thelower bound of observed logEQs among extantanthropoid species (table 6).

The logEQ estimates for Chilecebus andMartin’s (1990) data for Aegyptopithecus,imply that early taxa basal to Platyrrhini andCatarrhini (but postdating the divergencebetween these two clades) had smaller relativebrain volumes than extant members of either

clade, suggesting that the elevated encephali-zations of crown-clade platyrrhines and crown-clade catarrhines have been achieved conver-gently, pointing to a complex transformationin relative brain size within Anthropoidea.Martin’s (1990) suggestion that tarsiers andtheir fossil allies may exhibit an independentevolutionary trend of increasing encephaliza-tion emphasizes this pattern of multiple inde-pendent acquisitions of large relative brainvolume in Primates. If confirmed, this evolu-tionary pattern in Primates would mirrorindependent increases in encephalization ob-served across mammalian lineages (Jerison,1970; Radinsky, 1971; Martin, 1984), andwithin subclades of Carnivora (Finarelli andFlynn, 2007; Finarelli, 2008) and the Cetacea(Marino et al., 2004). The convergent acquisi-tion of higher degrees of encephalization inplatyrrhines and catarrhines may yield insightsinto the evolutionary history of these featuresin other clades.

CONCLUSIONS

Morphometric body mass estimation meth-ods were evaluated using a suite of 80 cranial,mandibular, and dental variables for 17 speciesof extant platyrrhine primates, spanning therange of body masses within this group. Theaccuracy with which each morphological var-iable predicts body mass was quantified usingthe likelihood fit of the regression to theobserved body mass data, with a log-likelihooddifference of 2 indicating significantly betterpredictive power of one variable over anotherwith respect to the observed data.

The best cranial morphometric predictor ofbody mass in platyrrhines is mandibularlength. Only one variable, pterygoid-zygomat-ic length, fell within 2 LnL units of mandib-ular length, indicating no significant differencein the predictive power of these variables withrespect to the body mass data. While the bestpredictors were osteological measurements,the distribution of rank fits between osteolog-ical and dental variables does not differsignificantly, and, contrary to the conclusionsof some previous studies, there was noconsistent difference between the relativepredictive ability of dental versus cranialosteological variables. Mandibular and lower


dental measurements do correlate significantlybetter with body mass than those from thecranium and upper teeth.

Applying the 46 measurable body massproxies to the cranium and upper dentitionof the 20 Ma platyrrhine Chilecebus yields awide range of body mass estimates (85 gramsto ,1.7 kg). An initial weighted-averagemodel, applying the likelihood fits of eachvariable, produced a body mass estimate of319 grams, considerably less than a previouspreliminary report (1.0–1.2 kg: Flynn et al.,1995). The wide range of body mass estimatesfor Chilecebus underscores the hazards ofapplying body mass proxies to early divergingfossil taxa with potentially novel morphome-tries. Compared to the extant platyrrhine

regression, 26 proxies in Chilecebus differsignificantly from the allometry observedamong extant taxa. Importantly, variablesthat both significantly underestimate andoverestimate body mass are among the proxiesthat are inconsistent with modern allometries.Applying the weighted-average model tech-nique to a constrained set of only the 20proxies that follow extant allometries yieldsthe most reliable body mass estimate forChilecebus: 583 grams.

Based on this 583 gram body mass estimate,the encephalization of Chilecebus (logEQ 51.11) was found to be lower than that of allliving anthropoid primates. This EQ is com-parable to that of the early catarrhineAegyptopithecus, indicating that the high

TABLE 6

Mass, brain volumes, and calculated logEQ valuesValues relative to Martin’s 1990 regression for strepsirrhine primates as a frame of reference. Fossil ‘‘tarsioids’’and the fossil catarrhine Aegyptopithecus from Martin, 1990. Data for Chilecebus are from this study.Minimum, maximum, and median logEQs for the extant Platyrrhini and Catarrhini are given to the right.

Species Body Mass [g] Brain Volume [mL] Ref logEQ Min Median Max

Aegyptopithecus zeuxis 6710.00 34.40 Martin 1990, p 388 0.98

Necrolemur antiquus 233.00 3.80 Martin 1990, p 388 1.06

Tetonius homonculus 74.00 1.50 Martin 1990, p 388 0.91

Rooneyia viejaensis 782.00 7.40 Martin 1990, p 388 0.90

Chilecebus carrascoensis 582.62 7.46 1.11

Platyrrhini (extant) 1.54 1.96 2.44

Aotus trivigatus 535.50 16.90 Martin 1990, p 362 1.99

Callicebus moloch 854.70 18.30 Martin 1990, p 362 1.75

Saimiri sciureus 743.20 23.60 Martin 1990, p 362 2.10

Cebus appella 2500.00 76.20 Martin 1990, p 362 2.44

Lagothrix lagotricha 6300.00 97.20 Martin 1990, p 362 2.06

Allouatta seniculus 6145.50 60.30 Martin 1990, p 362 1.60

Callimico goeldii 480.00 11.10 Martin 1990, p 362 1.64

Cebuella pygmaea 125.00 6.10 Martin 1990, p 362 1.96

Callithrix jacchus 292.00 7.20 Martin 1990, p 362 1.54

Catarrhini (extant) 1.39 2.00 2.25

Miopithecus talapoin 1250.00 39.00 Martin 1990, p 362 2.25

Cercopithecus ascanius 3605.00 63.40 Martin 1990, p 362 2.01

Cercocebus albigena 7758.00 96.90 Martin 1990, p 362 1.91

Macaca mulatta 4600.00 83.00 Martin 1990, p 362 2.11

Papio anubis 16650.00 177.00 Martin 1990, p 362 2.00

Theropithecus gelada 21500.00 133.00 Martin 1990, p 362 1.54

Colobus badius 8617.00 61.60 Martin 1990, p 362 1.39

Hylobates lar 5422.00 99.90 Martin 1990, p 362 2.19

Symphalanges syndactylus 10725.00 123.70 Martin 1990, p 362 1.94

Pongo pygmaeus 55000.00 418.00 Martin 1990, p 362 2.04

Pan troglodytes 45290.00 393.00 Martin 1990, p 362 2.11

Gorilla gorilla 114450.00 465.00 Martin 1990, p 362 1.65


degree of encephalization observed amongmodern anthropoids likely was attained inde-pendently in both the platyrrhine and catar-rhine clades.

ACKNOWLEDGMENTS

This research was supported by our homeinstitutions, research grants from the U.S.National Science Foundation (DEB-9317943,DEB-0317014 and DEB-0513476 to JJF;DEB-9020213 and DEB-9318126 to ARW),a John S. Guggenheim Memorial FoundationFellowship (JJF), fellowships from the Uni-versity of Chicago and Field Museum (KES,JAF), and by the University of Michigan,Society of Fellows (JAF). We thank the staffof the Field Museum Division of Mammalogyand the Mammalogy Collections of theAmerican Museum of Natural History foraccess to extant primate specimens. We aregrateful for the long-term support of theMuseo Nacional de Historia Natural (Santiago,Chile) and the Consejo Nacional de Monu-mentos Naturales de Chile. We especially ac-knowledge the exceptional preparation talentsand efforts of our deceased friend and colleague,Steven McCarroll, who painstakingly removedthe skull of Chilecebus from its extremely hardvolcaniclastic matrix.

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Location Measurement Name Description

Cranial/ventral Skull length from the back of the occiput to the anterior tip of the premaxilla

Occipital width across the mastoids at the widest part of the occiput

Condyle length at the longest part of the condyle, from the most posterior to the

most anterior point along the condyle plane

Condyle width at the widest part of the condyle, along the lateral axis,

perpendicular to measurement condyle length

Foramen magnum height along the anterior-posterior axis of the skull

Foramen magnum width measured perpendicular to measurement foramen magnum height

Foramen magnum area product of length and width measurements

Basal length of pterygoid fossa distance between sphenobasin and the base, or upper part of

contact, of the vomer

Pterygoid-zygomatic length from the posterior base of the pterygoid plate to the most

posterior point of zygomatic skull attachment

Bulla length at longest part of bulla, at oblique angle to the midline of the skull

Bulla width at widest part of bulla

Occipital chord chord from the lambda to the opisthion

Cranial/dorsal Braincase width at widest part of braincase

Temporal fossa length from the most posterior point of the lamboidal crest to the back

of the supraorbital process

Postorbital constriction at narrowest point posterior to orbits

Bizygomatic across the widest portion of the zygomatic arches

Braincase length from the postorbital constriction to the occipital condyles

Width of infratemporal fossa from parietal-sphenoid-temporal junction to anterosuperior

zygomatic-temporal suture

Frontal chord from bregma to nasion

Parietal chord from bregma to lambda

Cranial/posterior Skull vault height from top of skull (highest point) to condyles

Cranial/anterior Orbit width at widest part of the orbit

Facial height (length) along bony midline from nasion to acanthion, or uppermost

midline point of the premaxilla

Vertical face height from the line between nasion and intersection of the

intermaxillary and interpalatine sutures on the hard palate

Cranial/lateral Temporal chord from the bregma on top of the skull to the asterion

Mandibular Mandibular length from the back of the condyle to the front of the median incisor

alveolus

Mandibular height from ventral base of the ramus to the base of the tooth

Moment arm of the masseter from dorsal surface of the condyle to central border of the angular

process

Moment arm of the temporalis from posterior point to most anterior point of masseteric fossa

Masseteric fossa length from back of the condyle to most anterior point of the masseteric

fossa

Palate Palate length from most posterior point of tooth row to most anterior point of

maxilla

Palate width chord across palate at M1

Dental Cheek tooth row

(upper and lower)

length of all premolars and molars

Width of all teeth

(upper and lower)

at the widest part of tooth: I1,I2,C1, P2,P3,P4

width of anterior and posterior lophs: M1,M2

Length of all teeth

(upper and lower)

mesiodistal length of: I1,I2,C1,P2,P3,P4,M1,M2

Area of cheek teeth

(upper and lower)

product of length and width: P2,P3,P4

average of width measurements for: M1,M2

Maxillary incisor size chord between the distal cemento-enamel junction of the left and

right lateral incisors

APPENDIX 1

MEASUREMENT VARIABLES


APPENDIX 2

PLATYRRHINE SPECIMENS EXAMINED

Species n Specimen Sex Species n Specimen Sex

Alouatta caraya 8 FMNH 96012 M Callithrix pygmaea 10 AMNH 76327 M

FMNH 96013 M AMNH 239605 M

FMNH 26560 M AMNH 182942 M

FMNH 26568 M AMNH 182943 M

FMNH 96011 F AMNH 75280 M

FMNH 26555 F AMNH 74056 F



AMNH 74369 F

Aotus vociferans 10 FMNH 70682 M AMNH 182944 F

FMNH 70685 M

FMNH 70688 M Cebus apella 10 FMNH 92111 M

FMNH 70690 M FMNH 92114 M


FMNH 70681 F FMNH 92116 M


FMNH 70684 F FMNH 92112 F



FMNH 92118 F

Ateles geoffroyi 10 FMNH 41584 M FMNH 92119 F

FMNH 13896 M

FMNH 13897 M Chiropotes satanas 10 FMNH 95518 M








FMNH 95515 F

Brachyteles arachnoides 2 AMNH 80405 F FMNH 95516 F

AMNH 128 ?

Lagothrix lagotricha 10 FMNH 70574 M

Cacajao calvus 10 AMNH 70191 M FMNH 70575 M

AMNH 73717 M FMNH 70576 M



AMNH 98316 M FMNH 70581 F

AMNH 76392 M FMNH 70582 F

AMNH73719 F FMNH 70583 F

AMNH 98397 F FMNH 70584 F

AMMH 76390 F FMNH 70589 F

AMNH 76649 F

Leontopithecus

rosalia

10 FMNH 122012 M

Cacajao melanocephalus 6 AMNH 78562 M FMNH 57150 M



AMNH 78569 F FMNH 57839 M




Species n Specimen Sex Species n Specimen Sex

FMNH 57152 F

Callimico goeldii 11 FMNH 148062 M FMNH 57998 F

FMNH 148065 M FMNH 134505 F

FMNH 145462 M

FMNH 153715 M Pithecia pithecia 10 FMNH 93251 M

AMNH 183290 F FMNH 93252 M

FMNH 153712 F FMNH 95508 M

FMNH 159976 F FMNH 95509 M

FMNH 159975 F FMNH 95504 M

FMNH 150674 F FMNH 93250 F

AMNH 239601 ? FMNH 93253 F

AMNH 176602 ? FMNH 95510 F

FMNH 95511 F

Callithrix jacchus 10 FMNH 20420 M FMNH 95506 F

FMNH 20228 M

FMNH 20229 M Saguinas mystax 10 FMNH 86951 M








FMNH 87138 F

Callicebus moloch 10 FMNH 92100 M FMNH 87139 F

FMNH 92101 M

FMNH 92102 M Saimiri sciureus 10 FMNH 70647 M








FMNH 70646 F

FMNH 70648 F

Specimen numbers are for Field Museum of Natural History (FMNH) and American Museum of Natural History

(AMNH) mammalogy collections.

APPENDIX 2

(Continued)


AP

PE

ND

IX3

SP

EC

IES

ME

AN

SF

OR

EX

TA

NT

PL

AT

YR

RH

INE

TA

XA

Sp

ecie

sA

l_ca

raA

o_v

oci

At_

geo

fB

r_a

rac

Ca

_ca

lvC

a_

mel

aC

i_m

olo

Cl_

go

elC

x_

jacc

Cx

_p

yg

Ce_

ap

elC

h_

sata

La

_la

go

Le_

rosa

Pi_

pit

hS

g_m

yst

Sm

_sc

iu

Sk

ull

L1

05

.38

65

.28

11

1.7

01

11

.51

96

.36

91

.59

69

.77

51

.94

49

.01

34

.44

10

4.7

29

6.1

61

16

.33

59

.21

84

.31

58

.41

69

.94

Occ

W4

3.4

82

4.2

05

2.2

35

9.1

95

1.1

14

9.7

82

5.9

13

0.5

62

1.6

72

1.0

14

4.5

04

4.9

24

9.4

32

1.3

73

2.3

32

1.7

82

8.7

7

Co

nd

L8

.53

8.4

31

3.0

31

0.6

31

0.6

49

.70

7.0

95

.84

6.1

74

.33

10

.72

9.9

51

2.0

66

.63

8.3

96

.49

6.8

0

Co

nd

W3

.66

2.4

45

.47

4.8

33

.61

3.4

42

.50

2.0

01

.95

1.3

63

.77

3.4

44

.96

2.1

62

.72

2.1

02

.24

Fo

rH

12

.27

9.1

61

8.1

51

6.6

31

2.9

01

2.4

77

.43

7.1

26

.41

6.0

11

5.0

01

2.2

01

5.3

56

.55

9.7

87

.42

8.4

9

Fo

rW

13

.47

9.4

31

6.2

91

4.9

41

3.2

81

2.2

99

.67

7.6

86

.95

5.6

21

4.5

41

3.0

41

4.6

57

.82

11

.99

7.9

29

.47

Fo

rP

16

5.1

78

6.3

62

95

.55

24

8.4

61

71

.35

15

3.1

97

1.9

05

4.6

74

4.5

73

3.7

52

18

.16

159

.10

22

4.8

85

1.2

21

17

.24

58

.77

80

.42

Pte

ryL

27

.70

12

.54

24

.86

14

.66

15

.37

15

.67

16

.37

9.0

41

0.2

54

.44

21

.89

20

.32

32

.08

12

.71

18

.62

11

.82

12

.34

Pte

r-zy

35

.16

15

.89

29

.80

37

.38

27

.55

24

.56

17

.24

15

.84

12

.65

9.2

23

2.5

12

5.3

13

2.9

31

4.7

32

1.3

41

3.7

21

5.1

8

Bu

lL

23

.51

22

.79

36

.34

28

.80

25

.93

21

.90

18

.46

12

.91

13

.89

9.6

12

6.6

32

4.0

62

9.2

31

3.8

72

1.2

11

5.2

81

7.9

9

Bu

lW

12

.18

9.9

31

2.0

31

4.4

21

2.0

71

0.8

09

.30

6.1

66

.33

4.5

51

1.6

11

1.5

01

2.8

26

.84

10

.48

6.6

47

.08

OC

ho

rd1

9.7

31

4.5

52

9.1

12

2.3

62

4.2

42

3.4

11

5.8

01

2.7

41

1.1

26

.82

24

.99

22

.79

24

.33

14

.56

20

.16

12

.34

20

.71

Ca

seW

50

.21

37

.02

64

.23

62

.91

53

.60

51

.10

37

.58

29

.76

27

.24

20

.80

58

.49

55

.80

65

.57

30

.26

45

.50

30

.75

39

.08

Tem

pL

59

.97

40

.38

79

.35

81

.32

67

.54

60

.96

43

.86

40

.26

32

.35

27

.03

70

.26

58

.21

75

.38

39

.08

52

.19

38

.51

47

.99

PO

Co

n3

7.7

63

4.7

35

2.0

64

7.1

44

2.8

84

0.4

63

3.8

72

7.2

32

2.4

61

8.0

04

4.3

24

4.6

45

1.2

82

5.1

23

7.9

82

5.9

23

2.1

7

Zy

go

W7

1.7

84

2.4

07

0.4

87

1.8

56

6.6

56

0.2

54

3.6

83

5.2

93

0.5

12

2.4

97

1.4

56

3.7

47

3.6

33

6.5

15

4.1

23

6.4

64

0.1

3

Ca

seL

49

.00

33

.90

68

.92

75

.62

64

.77

65

.73

37

.43

37

.37

28

.00

26

.38

62

.37

53

.73

65

.38

34

.05

45

.85

33

.13

41

.35

FC

ho

rd4

4.3

43

3.1

16

5.9

95

3.0

04

4.0

94

4.5

93

2.4

92

8.3

82

6.1

31

9.6

26

1.5

04

0.9

46

0.5

12

8.6

94

3.6

82

6.2

23

6.1

5

PC

ho

rd3

2.2

32

9.6

44

7.4

14

5.2

94

2.3

84

1.8

63

0.1

92

6.7

12

0.5

61

7.4

93

0.2

73

9.1

83

8.4

02

6.6

12

7.2

32

7.7

93

1.5

4

Va

ult

H2

8.8

52

9.5

66

0.7

45

6.3

45

0.3

64

4.5

53

4.1

32

7.3

52

1.8

31

9.3

95

8.1

54

9.6

75

4.5

12

8.2

14

0.1

12

8.5

83

7.5

7

Orb

W2

5.1

72

3.3

42

7.3

82

1.5

31

8.9

21

8.7

91

8.3

11

2.5

21

1.1

69

.06

24

.63

24

.56

29

.05

12

.94

20

.09

13

.15

17

.00

Fa

cH

39

.03

22

.52

40

.98

37

.32

32

.62

28

.89

23

.17

15

.24

15

.45

9.5

83

8.6

03

4.4

03

8.3

51

8.8

62

8.9

91

7.7

12

1.0

4

Ver

tH

34

.10

22

.54

41

.31

31

.23

26

.41

24

.39

21

.43

13

.72

15

.47

8.6

33

6.2

02

9.9

23

8.6

01

9.3

12

8.8

51

7.3

62

0.6

7

TC

ho

rd3

7.7

83

0.9

35

1.3

65

3.3

24

6.9

24

3.7

42

9.9

02

5.1

72

2.4

41

7.5

04

6.4

54

6.3

35

2.6

82

7.4

03

5.9

12

6.6

33

5.2

3

Ja

wL

79

.00

37

.48

69

.91

78

.54

65

.34

58

.88

43

.38

33

.83

28

.28

20

.29

62

.95

60

.01

74

.46

36

.92

51

.17

34

.90

34

.84

Ja

wH

21

.50

8.4

01

6.3

41

8.4

41

8.5

41

6.6

01

2.6

06

.99

5.2

43

.83

15

.65

18

.63

18

.72

7.5

51

3.8

57

.15

7.2

2

MA

rmM

57

.32

16

.41

31

.66

52

.05

39

.56

36

.96

21

.33

16

.37

10

.60

8.1

42

4.8

62

8.5

13

3.2

81

3.0

02

1.6

21

2.5

21

1.2

8

MA

rmT

20

.44

6.4

91

6.4

22

4.8

22

0.9

31

6.5

16

.40

9.8

18

.49

7.1

91

5.8

81

1.9

81

9.4

07

.94

10

.77

8.5

88

.09

Ma

ssL

54

.35

23

.10

43

.07

47

.74

36

.09

31

.18

31

.16

17

.67

15

.23

9.8

84

1.8

54

3.3

85

6.8

92

1.2

83

4.8

01

9.5

81

8.2

7

UR

ow

L3

7.8

91

5.7

02

6.9

03

1.9

62

1.3

01

9.2

31

6.2

71

6.2

29

.29

6.8

82

5.4

61

9.7

62

8.3

11

2.9

71

9.2

21

0.4

61

4.7

3

LR

ow

L4

1.5

91

7.4

62

8.3

53

2.9

82

4.1

42

2.0

01

7.9

01

6.9

71

0.1

57

.84

27

.83

23

.13

32

.03

14

.48

21

.81

12

.31

15

.37

Pa

lL

42

.04

18

.76

34

.83

36

.65

24

.54

22

.33

21

.00

15

.20

15

.49

8.7

03

5.1

62

8.4

43

3.8

41

9.2

22

7.2

91

8.1

21

8.3

8

M1

Pal

W2

4.5

21

3.2

42

1.2

43

6.3

02

6.9

32

4.7

31

2.6

51

8.7

39

.12

10

.95

20

.39

16

.48

21

.76

12

.03

13

.18

11

.70

11

.70

MIn

c1

5.7

61

1.8

71

6.9

11

5.4

51

4.6

01

2.9

61

0.6

86

.98

7.4

24

.99

18

.05

12

.37

17

.70

9.0

91

1.6

99

.24

10

.18

UI1

W5

.67

3.1

05

.49

4.1

74

.08

3.6

73

.31

1.9

72

.79

1.5

75

.72

6.2

04

.55

3.5

04

.93

2.7

53

.13

UI2

W5

.15

2.5

84

.80

4.4

33

.66

3.3

02

.70

1.7

32

.40

1.4

05

.83

5.2

44

.41

2.7

43

.84

2.0

72

.82


AP

PE

ND

IX3

(Co

nti

nu

ed)

Sp

ecie

sA

l_ca

raA

o_v

oci

At_

geo

fB

r_a

rac

Ca

_ca

lvC

a_

mel

aC

i_m

olo

Cl_

go

elC

x_

jacc

Cx

_p

yg

Ce_

ap

elC

h_

sata

La_

lag

oL

e_ro

saP

i_p

ith

Sg

_m

yst

Sm

_sc

iu

UC

1W

8.9

53

.32

6.3

94

.79

6.7

65

.55

3.2

12

.40

2.7

71

.27

8.6

38

.90

7.2

83

.83

5.6

03

.29

3.8

5

UP

2W

7.4

63

.52

4.9

25

.36

5.0

84

.52

3.3

12

.80

2.3

01

.29

8.0

15

.10

5.7

83

.40

3.8

62

.96

3.8

4

UP

3W

8.4

73

.69

5.8

06

.12

5.4

24

.88

3.7

53

.11

2.6

51

.69

8.5

56

.12

6.6

84

.05

4.9

13

.13

4.1

8

UP

4W

8.3

83

.93

6.1

16

.81

5.2

64

.75

4.1

23

.07

2.8

92

.07

8.4

26

.24

6.8

14

.36

4.9

03

.30

4.1

4

UM

1W

18

.50

4.0

75

.93

7.2

14

.78

4.5

34

.73

3.8

43

.24

2.1

87

.68

5.4

66

.89

4.3

55

.14

3.4

24

.20

UM

1W

28

.25

4.1

16

.43

6.7

14

.96

4.4

24

.89

3.6

63

.35

2.1

77

.44

5.4

66

.64

4.4

05

.21

3.3

04

.04

UM

2W

18

.26

4.0

86

.02

7.0

54

.71

4.3

44

.53

3.3

02

.60

1.9

57

.00

5.1

96

.93

3.4

95

.25

2.9

03

.90

UM

2W

29

.04

3.9

26

.22

6.9

84

.59

4.1

84

.45

3.1

62

.77

1.8

96

.51

5.0

06

.37

3.5

95

.09

2.8

03

.49

UP

2L

5.3

82

.24

3.6

53

.86

3.4

43

.09

2.3

11

.80

1.9

70

.97

4.6

33

.51

3.9

92

.88

3.0

82

.16

2.3

6

UP

3L

5.1

32

.44

4.0

34

.55

3.3

52

.97

2.4

31

.90

1.9

51

.05

4.6

13

.48

4.0

32

.71

3.1

21

.88

2.2

0

UP

4L

5.0

82

.57

4.1

74

.66

3.4

23

.27

2.4

92

.00

1.9

61

.23

4.5

23

.78

4.3

22

.83

3.3

52

.03

2.1

6

UM

1L

7.9

43

.70

5.6

86

.77

3.9

63

.64

3.7

42

.70

2.8

31

.85

5.8

54

.12

6.0

23

.92

4.2

42

.88

3.0

9

UM

2L

9.0

23

.40

5.7

36

.73

3.8

33

.64

3.4

72

.29

2.0

01

.43

5.1

14

.09

5.9

52

.89

4.1

41

.83

2.5

1

UI1

L4

.43

4.1

65

.24

3.6

84

.60

4.1

82

.92

2.1

12

.68

1.3

65

.51

4.0

64

.58

2.9

03

.61

2.8

73

.01

UI2

L4

.06

2.6

13

.95

3.5

33

.48

3.0

42

.38

1.6

72

.13

1.1

54

.66

2.9

13

.95

2.7

42

.85

2.4

82

.40

UC

1L

7.1

03

.24

5.8

14

.61

7.0

66

.04

2.9

52

.83

2.4

71

.38

7.8

56

.85

6.5

13

.40

4.5

32

.89

3.3

6

LI1

W4

.36

3.2

44

.08

4.2

63

.72

3.7

42

.49

1.7

72

.41

1.4

74

.62

6.5

03

.92

3.1

04

.64

2.4

42

.35

LI2

W4

.90

3.5

34

.55

5.0

64

.42

3.8

72

.84

2.0

92

.55

1.7

44

.96

7.5

34

.40

3.3

05

.04

2.5

72

.63

LC

1W

9.1

43

.39

5.5

85

.35

7.1

96

.03

2.9

32

.58

2.7

11

.42

8.5

79

.09

6.4

24

.24

5.5

03

.76

3.7

6

LP

2W

6.8

02

.68

4.4

94

.93

4.0

33

.89

2.6

22

.36

2.2

91

.01

6.1

14

.66

5.5

33

.03

3.8

42

.38

3.1

6

LP

3W

5.6

92

.67

4.3

34

.84

4.1

53

.76

2.7

02

.21

2.1

11

.04

5.5

34

.51

5.0

13

.01

3.6

91

.99

2.9

0

LP

4W

5.6

83

.01

4.5

55

.10

4.3

03

.87

3.0

32

.27

2.0

61

.17

5.6

74

.42

5.0

63

.34

3.7

02

.01

2.9

6

LM

1W

15

.08

3.0

54

.93

5.2

44

.10

3.8

72

.99

2.4

22

.14

1.4

55

.56

4.2

34

.80

3.1

03

.72

2.2

12

.88

LM

1W

26

.29

3.2

95

.13

5.4

34

.14

3.8

53

.07

2.4

92

.21

1.4

65

.36

4.2

25

.12

2.9

93

.87

2.2

22

.78

LM

2W

15

.20

3.1

65

.52

5.3

84

.26

3.8

13

.23

2.1

71

.78

1.3

25

.40

4.1

75

.27

2.4

43

.86

2.0

02

.80

LM

2W

26

.85

3.2

35

.48

5.6

24

.22

3.8

32

.92

2.1

71

.94

1.3

14

.99

4.0

15

.29

2.5

33

.88

1.8

32

.46

LP

2L

5.8

92

.14

3.9

53

.91

4.2

73

.70

1.9

72

.19

1.6

31

.06

4.5

43

.66

4.3

32

.69

3.1

52

.23

2.2

4

LP

3L

5.6

22

.12

3.5

44

.26

3.5

83

.36

2.0

61

.92

1.5

61

.00

4.3

73

.64

4.0

52

.48

3.1

61

.92

1.9

1

LP

4L

5.8

42

.49

3.7

75

.04

3.6

73

.29

2.2

62

.03

1.8

61

.33

4.4

83

.65

4.4

22

.83

3.5

62

.09

2.1

0

LM

1L

7.8

13

.53

5.3

37

.03

4.4

94

.19

3.5

62

.81

2.5

91

.70

5.9

24

.42

5.8

13

.51

3.9

02

.78

3.0

2

LM

2L

8.7

43

.69

5.4

16

.98

4.1

64

.09

3.7

32

.67

2.2

81

.48

5.3

84

.31

5.8

03

.14

4.3

42

.53

2.7

5

LI1

L2

.83

2.4

43

.12

2.4

41

.92

1.9

41

.53

1.3

71

.44

0.8

43

.02

1.7

53

.29

1.8

31

.92

1.7

91

.59

LI2

L3

.41

2.0

83

.68

2.3

22

.64

2.4

41

.95

1.3

81

.48

1.0

03

.71

2.2

53

.84

1.9

32

.35

1.8

81

.84

LC

1L

5.7

32

.27

3.9

73

.96

5.8

34

.87

2.0

02

.26

1.7

41

.39

6.3

65

.96

5.3

82

.80

3.5

22

.48

2.4

0

UP

2A

40

.16

7.8

91

7.9

72

0.7

21

7.5

11

3.9

47

.65

5.0

44

.53

1.2

53

7.0

61

7.9

22

3.0

69

.80

11

.89

6.3

99

.07

UP

3A

43

.41

8.9

82

3.3

52

7.8

31

8.1

91

4.4

89

.12

5.8

95

.17

1.7

83

9.3

82

1.2

82

6.9

21

0.9

61

5.3

25

.90

9.2

2

UP

4A

42

.58

10

.08

25

.51

31

.74

18

.02

15

.52

10

.27

6.1

45

.65

2.5

43

8.0

82

3.5

92

9.3

912

.34

16

.39

6.6

98

.95


Sp

ecie

sA

l_ca

raA

o_v

oci

At_

geo

fB

r_a

rac

Ca

_ca

lvC

a_

mel

aC

i_m

olo

Cl_

go

elC

x_

jacc

Cx

_p

yg

Ce_

ap

elC

h_

sata

La

_la

go

Le_

rosa

Pi_

pit

hS

g_m

yst

Sm

_sc

iu

UM

1A

66

.49

15

.14

35

.08

47

.06

19

.31

16

.29

17

.99

10

.11

9.3

14

.03

44

.18

22

.46

40

.72

17

.16

21

.93

9.6

91

2.7

4

UM

2A

77

.98

13

.58

35

.05

47

.22

17

.79

15

.50

15

.61

7.4

05

.37

2.7

43

4.4

72

0.8

33

9.5

610

.25

21

.39

5.2

29

.24

LP

2A

40

.07

5.7

21

7.7

31

9.2

81

7.2

11

4.3

95

.16

5.1

73

.72

1.0

72

7.7

41

7.0

52

3.9

88

.14

12

.11

5.2

97

.09

LP

3A

32

.00

5.6

61

5.3

32

0.6

21

4.8

31

2.6

45

.55

4.2

63

.29

1.0

42

4.1

71

6.4

52

0.2

87

.48

11

.65

3.8

25

.54

LP

4A

33

.20

7.5

01

7.1

42

5.7

31

5.7

71

2.7

46

.85

4.6

03

.83

1.5

72

5.3

71

6.1

52

2.3

69

.44

13

.19

4.2

06

.20

LM

1A

44

.14

11

.17

26

.82

37

.51

18

.49

16

.17

10

.79

6.9

05

.64

2.4

83

2.3

31

8.7

02

8.8

010

.68

14

.80

6.1

78

.55

LM

2A

52

.15

11

.80

29

.72

38

.38

17

.64

15

.64

11

.46

5.8

04

.23

1.9

52

7.9

61

7.6

23

0.6

47.8

01

6.8

04

.82

7.2

1

Sp

ecie

sA

bb

rev

iati

on

s:A

l_ca

ra,

Alo

ua

tta

cara

ya;

Ao

_v

oci

,A

otu

svo

cife

ran

s;A

t_g

eof,

Ate

les

geo

ffro

yi;

Br_

ara

c,B

rach

yte

les

ara

chn

oid

s;C

a_

calv

,C

aca

jao

calv

us;

Ca

_m

ela,

Ca

caja

om

elan

oce

pha

lus;

Ci_

mo

lo,

Ca

llic

ebu

sm

olo

ch;

Cl_

go

el,

Ca

llim

ico

go

eld

ii;

Cx

_ja

cc,

Ca

llit

hri

xja

cch

us;

Cx

_p

yg

,C

all

ith

rix

py

gm

aea

;C

e_ap

el,

Ceb

us

ap

ella

;C

h_

sata

,

Ch

iro

po

tes

sata

nas;

La

_la

go

,L

ag

oth

rix

lag

otr

ich

a;

Le_

rosa

,L

eon

topit

hec

us

rosa

lia;

Pi_

pit

h,

Pit

hec

iap

ith

ecia

;S

g_m

yst

,S

ag

uin

as

my

sta

x;

Sm

_sc

iu,

Sa

imir

isc

iure

us.

AP

PE

ND

IX3

(Co

nti

nu

ed)


APPENDIX 4

SCATTERPLOTS OF REGRESSIONS OF BODY MASS ON MEASUREMENT VARIABLES

Y-axis is body mass in all plots, X-axis variable indicated in each plot. Plots are phylogenetically

independent contrasts.





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Documents

Estimating body mass in New World “monkeys” (Platyrrhini, Primates), with a consideration of the Miocene platyrrhine, Chilecebus carrascoensis