Morphological and functional adaptations in the handof terrestrial macaques and arboreal gibbons

marie.vanhoof@kuleuven.be

ACKNOWLEDGEMENTSWe would like to thank the zoos and institutions that contributed by providing the primate cadaverand skeletal specimens, and AZ Groeninge (Kortrijk, Belgium) for CT-scanning. The research is fundedby KU Leuven.

REFERENCESSarmiento, 1988, International Journal of Primatology 9(4), 281-345.Fleagle, 1976, Folia Primatology 26(4), 245-269.Almécija et al., 2015, The Anatomical Record 298, 212-229.

Quantify (1) wrist mobility during radioulnar deviation, (2) wrist morphology, and (3) hand musculaturein terrestrial macaques and arboreal gibbons,

to elucidate the precise contribution of muscle anatomy and 3D bone geometry to overall wrist mobility

GOAL

CONCLUSIONFuture work will include (I) investigation of more carpal bones, (II) more species (e.g. chimpanzee and gorilla), and (III) covariation analyses to

investigate specific relationships between wrist mobility, wrist morphology, and hand musculature.

Marie Vanhoof

Evie Vereecke, Isabelle De Groote, Koen NelissenJan Palfijn Anatomy Lab, Dept. Development & Regeneration, KU Leuven Campus Kulak Kortrijk, Belgium

Hand interacts with the substrate environment hand morphology will show adaptations to loading

ARBOREAL PRIMATESTERRESTRIAL PRIMATES

Number of specimens6 (morphology)

7 (mobility + musculature)

Number of specimens6 (mobility)

19 (morphology)

13 (musculature)

(1) Hand of each specimen is CT-scanned in neutral, and maximal radial and ulnar deviationusing a self-developed rig to standardize wrist positions

(2) 3D bone models of carpal bones, third metacarpal, ulna and radius are created,which are used for kinematic and morphometric (3DGM) analyses

(3) All specimens are dissected using a dedicated photography setup for a full documentation and quantification of the forearm and hand muscles

Fig. 1 – Maximal range of motion (ROM) during radioulnardeviation in macaques (Macaca), humans (Homo) andgibbons (Symphalangus, Hylobates). The ROM is highest inHylobates gibbons (77.32˚ ± 6.29˚) and lowest in macaques(42.2˚ ± 5.2˚) , while humans (62.7˚ ± 9.1˚) overlap withthe hylobatid range.

(36%)

Fig. 2 – Scatterplot of PC1 and PC2 scores for the ulna of macaques and hylobatids, asa result of a principal component analysis (PCA) to quantify shape variation.Macaques (pink) and Hylobates lar (blue) are separated along axis PC2 based on theirulnar morphology. Gibbons show an increase in curvature of the ulnar head and aninclination of the styloid process. These morphologies have been linked to an increaseof wrist mobility ( = Fig. 1), which is important during brachiation.

(27%)

(1) WRIST MOBILITY (2) WRIST MORPHOLOGY (3) HAND MUSCULATURE

Fig. 3 – (A) In macaques, the fingers arecontrolled in pairs, which might aid in efficientpositioning of the hand/fingers to uneventerrain; (B) in gibbons, extension of the littlefinger is separate from extension of digits 2-4,which might be important when reaching orgrasping a support.

ULNA

(A) (B)

Hand interacts with the superstrate environment hand morphology will show adaptations for a higher mobility

Example: Macaques Example: Gibbons