A validated method for modeling anthropoid hip abduction in silico

Abstract

Our models broadly correspond to in vivo data on hip abduction, although the relationship between the models and live animal data is less straightforward than hypothesized. The models can predict acrobatic or stereotyped locomotor adaptation for taxa with values near the extremes of the range of abduction ability. Our findings underscore the difficulties associated with modeling complex systems and the importance of validating in silico models. They suggest that models of joint mobility can offer additional insight into the functional abilities of extinct primates when done in consideration of how joints move and function in vivo. Am J Phys Anthropol 160:529-548, 2016. © 2016 Wiley Periodicals, Inc.

Hip joint mobility in free‐ranging rhesus macaques

“…Simulations based on long-tailed ( M. fascicularis ) and pig-tailed ( M. nemestrina ) macaques predicted that hip abduction should be about 47° (range of 39–57°) (Hammond et al, 2016), which is significantly higher than that observed in captive rhesus (mean 25°, range 10–37°) and long-tailed macaques (mean 26°, range 20–36°) (Hammond, 2014a). The range of abduction (i.e., 20–62°) in the free-ranging rhesus macaques measured here overlaps with the simulation data, suggesting that the Hammond et al (2016) model of hip abduction predicts joint excursions in Macaca better than previously realized. This study highlights the discrepancy between measures of hip abduction in captive and free-ranging rhesus macaques and underscores the need for caution when selecting in vivo samples for locomotor studies, as small cage-confinement can impact joint mobility in monkeys.…”

“…A larger span at the knee should reflect a greater hindlimb envelope (i.e., a greater reach of the hindlimb), allowing an animal to reach further for more distantly placed arboreal supports (see also Hammond, 2014a; b; Hammond et al, 2016; Preuschoft et al, 2016). Because an increased limb envelope increases arboreal competency, and is also increased by higher levels of abduction, this suggests to us that the observed increase in hip abduction in free-ranging animals is likely to be biologically meaningful.…”

“…A comparative digital model of hip abduction based on bony morphology (Hammond et al, 2016) indicates that macaque bony hip morphology predicts a larger range of hip abduction than is found empirically (i.e., when measured in vivo ; Hammond, 2013; Hammond, 2014a). One possible explanation for this is that prior measurements of macaques were made on captive individuals, who might exhibit a reduced range of hip abduction due to long-term caging, whereas model predictions are based on wild-shot animals.…”

“…One possible explanation for this is that prior measurements of macaques were made on captive individuals, who might exhibit a reduced range of hip abduction due to long-term caging, whereas model predictions are based on wild-shot animals. The laboratory macaques (Macaca mulatta and Macaca fascicularis) tested against the Hammond et al (2016) model of hip abduction lacked access to climbing structures in their enclosures and lived in cages that limited the range of limb movements (see Section 2.1 Study sample and environment). The caged macaques differed from the other live animals in the study, which were primates living in larger and/or more naturalistic enclosures with access to climbing structures.…”

A methodology of theropod print replication utilising the pedal reconstruction of Australovenator and a simulated paleo-sediment

“…The 3-D Dromaius meshes were scaled to the same proportional size as the Australovenator bone meshes. This provided a guide to digitally articulate the Australovenator bones in the same weight-bearing position as the Dromaius specimen which enabled an ‘ in silico’ (Hammond, Plavcan & Ward, 2016) restoration of the Australovenator pes considering both soft tissue attachment points and proportions (See Fig. 11 in White et al, 2016).…”