DOI: 10.5061/dryad.r4xgxd2r0
title: Neurocranial narrowness across nonhuman anthropoid primates

description: Body size allometry has been proposed to explain neurocranial shape
 variation across platyrrhine monkeys, including the extreme neurocranial
 narrowness (NCN) of small-bodied taxa. However, catarrhine primates do not
 align with the proposed platyrrhine allometry, suggesting that body size
 alone may not explain anthropoid NCN variation. We measured NCN in
 platyrrhine and catarrhine anthropoids, and identified inter-clade
 differences in degree and allometric scaling of NCN using GLS pANCOVA, a
 method combining generalized least squares analysis and phylogenetic
 analysis of covariance. We further performed character history analysis
 using extant anthropoid data and fossil evidence to estimate neurocranial
 shape in anthropoid ancestors. We found no unified allometry of NCN across
 platyrrhines or across anthropoids as a whole, and there was no
 significant correlation between body mass and NCN across platyrrhines or
 catarrhines. At the subfamily level, callitrichine and possibly cebine
 platyrrhines differ from other anthropoids in degree and allometric
 scaling of NCN. Character history analysis suggests that higher NCN is the
 ancestral platyrrhine condition, and broader neurocranial shape evolved
 independently in catarrhines and larger-bodied platyrrhines. Our results
 support the hypothesis that body size does not explain anthropoid NCN
 variation, and provide a foundation for future research into potential
 correlates of anthropoid NCN.
description: # Neurocranial narrowness across nonhuman anthropoid primates Dataset DOI:
 [10.5061/dryad.r4xgxd2r0](10.5061/dryad.r4xgxd2r0) ## Description of the
 data and file structure The dataset contains a complete list of skeletal
 specimens with the linear measurement values used to calculate
 neurocranial narrowness (NCN), as well as annotated R code to replicate
 phylogenetic analyses of covariance and generalized least squares analyses
 (GLS pANCOVA). GLS pANCOVA identifies species or clades that deviate from
 expected neurocranial shape allometry. R code is also included for
 performing linear regression of brain weight residuals and neurocranial
 narrowness values. ### Code/software The .Rmd files were compiled in
 RStudio for R version 4.3.3, and require the **evomap** package (Smaers,
 J.B., and F.J. Rohlf. 2016. "Testing species’ deviations from
 allometric predictions using the phylogenetic
 regression." *Evolution* 70: 1145-1149). The phylogenetic tree
 referenced in the R code is available through the **10kTrees Project**
 (Arnold C., L. J. Matthews, and C. L. Nunn. 2010. "The *10kTrees
 Website*: A New Online Resource for Primate Phylogeny." *Evolutionary
 Anthropology* 19: 114-118). * To download **evomap** for R:
 [https://smaerslab.com/software/](https://smaerslab.com/software/) * The
 10kTrees Project:
 [https://10ktrees.nunn-lab.org/Primates/index.html](https://10ktrees.nunn-lab.org/Primates/index.html) ### Files and variables #### File: qualaveragesfemale.csv **Description:** Species-average neurocranial narrowness values for female specimens, formatted for use in the attached R code. These values were derived from caliper measurements of skeletal specimens from the Smithsonian National Museum of Natural History and Harvard Museum of Comparative Zoology; a complete accounting of specimens can be found in the **rawdata.csv** file. ##### Variables * **Genus.** Genus and species, formatted to match phylogenetic tree labels used in the * **Weight.** Species-average body mass in kilograms (kg), per Smith and Jungers (1997). * **NCN.** Species-average neurocranial narrowness, calculated as **NCL** divided by **NCB**. * **NCL.** Species-average neurocranial length in millimeters (mm), measured from glabella to lambda. * **NCB.** Species-average neurocranial breadth (mm), measured as biparietal breadth from euryon to euryon. #### File: pANCOVA_f.Rmd **Description:** Annotated R Markdown code for performing a phylogenetic ANCOVA to identify deviations from expected allometry of neurocranial narrowness. This analysis includes only female specimens, and requires importing the **qualaveragesfemale.csv** file. #### File: qualaveragesmale.csv **Description:** Species-average neurocranial narrowness values for male specimens, formatted for use in the attached R code. As above, these values were derived from caliper measurements of skeletal specimens from the Smithsonian National Museum of Natural History and Harvard Museum of Comparative Zoology; a complete accounting of specimens can be found in the **rawdata.csv** file. ##### Variables * **Genus.** Genus and species, formatted to match tree tip labels. * **Weight.** Species-average body mass in kilograms (kg), per Smith and Jungers (1997). * **NCN.** Species-average neurocranial narrowness, calculated as **NCL** divided by **NCB**. * **NCL.** Species-average neurocranial length in millimeters (mm), measured from glabella to lambda. * **NCB.** Species-average neurocranial breadth (mm), measured as biparietal breadth from euryon to euryon. #### File: pANCOVA_m.Rmd **Description:** Annotated R Markdown code for performing a phylogenetic ANCOVA to identify deviations from expected allometry of neurocranial narrowness. This analysis includes only male specimens, and requires importing the **qualaveragesmale.csv** file. #### File: pgls.Rmd **Description:** Annotated R Markdown code for performing a phylogenetic generalized least squares analysis of neurocranial narrowness allometry across anthropoids. Requires importing both **qualaveragesfemale.csv** and **qualaveragesmale.csv**. #### File: univariate_f.Rmd **Description:** Annotated R Markdown code for univariate phylogenetic ANCOVA of neurocranial length and breadth, where each variable is analyzed individually. Includes only female specimens, and requires importing the **qualaveragesfemale.csv** file. #### File: univariate_m.Rmd **Description:** Annotated R Markdown code for univariate phylogenetic ANCOVA of neurocranial length and breadth, where each variable is analyzed individually. Includes only male specimens, and requires importing the **qualaveragesmale.csv** file. #### File: brainweights.csv **Description:** Species-average brain weight, body weight, and neurocranial narrowness values. ##### Variables * **Species.** Genus and species. * **Brainweight.** Species-average brain weight in kilograms (kg), derived from Stephan (1981) and Boddy *et al.* (2012). * **Bodyweight.** The median value between species-average male and species-average female body mass (kg), per Smith and Jungers (1997). * **M.** Species-average male body mass (kg). * **F.** Species-average female body mass (kg). * **NCN.** Species-average neurocranial narrowness, calculated as neurocranial length divided by neurocranial breadth. * **EQ.** Encephalization quotient, calculated as per Jerison (1973). #### File: EQ_analysis.Rmd **Description:** Annotated R Markdown code for linear regressions of brain weight residuals and neurocranial narrowness. Requires importing the **brainweights.csv** file. #### File: rawdata.csv **Description:** Original list of specimens with taxonomic information and linear measurements, as well as body mass (where available) and notes on methods and preservation. ##### Variables * **Call num.** Specimen's museum call number, where "USNM" refers to the Smithsonian National Museum of Natural History and "MCZ" the Harvard Museum of Comparative Zoology. * **Sex.** Male (M), female (F), or unknown (?). * **Genus / sp.** Genus, species, and (when available) subspecies of each specimen. * **Recorded weight (kg).** Museum data for some specimens included the weight of the individual in kilograms. This column is left blank for specimens without recorded weights. * **Cranial length (mm).** Cranial length from glabella to lambda, in millimeters. * **Cranial breadth (mm).** Cranial breadth from euryon to euryon, in millimeters. * **CL/CB (NCN).** Neurocranial narrowness, calculated as cranial length divided by cranial breadth.