Kinematics and morphological correlates of descent strategies in arboreal mammals suggest early upright postures in euprimates
- Center for Research on Paleontology-Paris, France
- Laboratory of Comparative Zoology, Institute of Biology, Humboldt University of Berlin, Germany
- Department of Zoology, School of Biology, Aristotle University of Thessaloniki, Greece
Figures
Figure 1
Strategies of descent on vertical supports of various diameters by species.
(A) Photographs illustrating the three different strategies of descent identified in this study. Black arrows represent the axis of the body regarding the support and the direction of the movement, and gray arrows represent the direction of the gaze. (B) Proportions (in %) of each descent type (yellow = head-first descent, light green = side descent, and dark green = tail-first descent) occurring on each support category (vertical branches of large, medium, and small diameters represented by brown icons at the top of the graph), by species. Proportions of all individuals of the same species (n) were averaged. See Supplementary file 1 for details on the individuals studied, and Supplementary file 2 for the mean body masses (BM) references. NA = no data for the given condition. Results of statistical tests between support diameters (ANOVAs or MANOVAs on bootstrapped samples, confirmed by post hoc tests) are represented with annotations defined as NS (non-significant): p>0.05, *p<0.05, **p<0.01, and ***p<0.001. See Supplementary file 5A for associated p-values. (C) Associated phylogeny of the species studied with branch length obtained from http://timetree.org/; Kumar et al., 2017. (D) Photographs of individuals of various species descending vertical supports of different diameters.
Figure 2
Kinematics of locomotion during ascents and descents on vertical supports of varying diameters.
(A) Mean absolute speeds by species during ascents and each descent strategy on the vertical supports of large, medium, and small diameters (represented by brown icons on the top left of the plots), with box plot representations of the medians for all species combined in ascents and each descent strategy. (B) Mean relative speeds (based on individuals’ body length) by species during ascents and each descent strategy on each support type, with box plot representations of the medians for all species combined in ascents and each descent strategy. (C) Mean duty factors by species, differentiating forelimbs (left box plots) and hindlimbs (right box plots), during ascents and each descent strategy on each support type, with box plot representations of the medians for all species combined in ascents and each descent strategy. Results of statistical tests between ascents and each descent strategy (two-sided Mann-Whitney U tests) are represented with annotations defined as NS: p>0.05, *p<0.05, **p<0.01, and ***p<0.001. See Supplementary file 5B–D for associated p-values. Percentages correspond to the relative variation of each kinematic variable mean in each descent condition compared to ascents.
Figure 3 with 1 supplement
Proportions (in %) of gait types by support diameters for ascents and each descent strategy, for all phylogenetic groups.
Results of statistical tests on the fraction of symmetrical versus asymmetrical gaits by group between ascents and descents on each support (two-sided Wilcoxon signed rank tests) are represented with annotations defined as NS: p>0.05, *p<0.05, **p<0.01, and ***p<0.001. NA = not applicable. DSDC: Diagonal sequence - diagonal couplet, LSDC: Lateral sequence – diagonal couplet, LSLC: Lateral sequence – lateral couplet. See Supplementary file 5F for associated post hoc corrected p-values. See Figure 3—figure supplement 1 for detailed proportions of gait types by species and support diameters.
Figure 3—figure supplement 1
Mean proportions of gait types (in %) by support diameter and by ascent and descent conditions, for each species.
DSDC: diagonal sequence – diagonal couplet, LSDC: lateral sequence – diagonal couplet, LSLC: lateral sequence – lateral couplet.
Figure 4 with 2 supplements
Morphological correlates with vertical descents and prediction of descent strategy in extinct species.
Spearman correlations and associated corrected p-values between the proportion of head descents by extant species and (A) the logarithm of mean body mass, (B) the mean encephalization quotient (EQ), (C) the hindlimb to body length ratio (in %), and (D) between the proportion of side descent in extant primate species only and the hallux to foot length ratio (in %). Each plot also includes the head descent proportion (A–C) and side descent proportion (D) of fossils predicted with the Schafer’s multiple imputation procedure. See (Table 1) for body measurements definitions and (Supplementary files 2 and 3) for mean body masses, endocranial volume (ECV), and calculated EQ by species. See (Figure 4—figure supplement 2) for the plots of the percentage of head descent against the six other morphological variables analyzed by species, and (Supplementary file 5H and I) for Spearman rhos and associated corrected p-values between each morphological variable and the proportion of, respectively, head (Supplementary file 5H) and side descents (Supplementary file 5I) on vertical supports. See Supplementary file 4 for calculated morphological proportions of extinct species and Supplementary file 5J for the resulting predictions of their descent behavior.
Figure 4—figure supplement 1
Major axis orthogonal regressions on the log-transformed mean brain and mean body masses for all species (in black with the gray area representing the associated confidence interval) and by phylogenetic groups color coded as defined in Figure 1C.
Brain masses were calculated from ECV using a reference brain volumic mass of 1.036 g.cm3 (Ebinger, 1974). See Supplementary file 2 for associated mean body masses and mean endocranial volumes (ECV) by species.
Figure 4—figure supplement 2
Spearman correlations and associated corrected p-values between the proportion of head-first descents by species on vertical supports (all diameters combined) and the relative: (A) forelimb length, (B) intermembral index, (C) tail length, (D) thumb length, (E) hand length, and (F) foot length.
See (Figure 4) for the correlations on other variables, (Table 1) for the variables list and descriptions, and (Supplementary file 5H and I) for Spearman rhos and associated corrected p-values of all variables.
Figure 5
Phylogeny of studied species, including extant and extinct taxa, and representation of the best evolutionary model of head-first descent proportion.
We calculated a consensus tree for extant species based on 1000 trees from https://vertlife.org/, to which we added extinct taxa using age and phylogenetic topology from literature. See (Supplementary file 2) for estimated age of extinct species and associated references. The best evolutionary model of head-first descent proportion is an Ornstein-Uhlenbeck evolutionary model with two optimums (OUM) with a peak shift occurring at the node ‘plesiadapiformes + euprimates.’ The associated theta peaks of head-first descent proportions of the two subgroups ‘plesidapiforms + euprimates’ vs ‘others’ are represented in red and black, respectively.
Tables
Table 1
Definitions of body measurements performed on extant and extinct individuals and calculation of limb proportions.
| Length measured | Description |
|---|---|
| Body length | Total body length without tail (from nose to rump) |
| Tail length | Total tail length |
| Forelimb length | Total length of the forelimb (stylopod + zeugopod + autopod) |
| Hindlimb length | Total length of the hindlimb (stylopod + zeugopod + autopod) |
| Hand length | Maximal length from the tip of the third digit to the proximal carpus |
| Foot length | Maximal length from the tip of the third digit to the proximal tarsus |
| Pollex length | Maximal length from the tip of the distal phalanx to the proximal part of the metacarpus |
| Hallux length | Maximal length from the tip of the distal phalanx to the proximal part of the metatarsus |
| Proportion calculated | Description |
| % Tail to body length | |
| % Forelimb to body length | |
| % Hindlimb to body length | |
| Intermembral index | |
| % Hand to forelimb length | |
| % Foot to hindlimb length | |
| % Pollex to hand length | |
| % Hallux to foot length |
Additional files
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Supplementary file 1
List of animals studied.
Species with an* are nocturnal. PZP = Parc Zoologique de Paris, France. PZBM=Parc Zoologique et Botanique de Mulhouse, France.
- https://cdn.elifesciences.org/articles/108268/elife-108268-supp1-v1.xlsx
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Supplementary file 2
Mean body mass, endocranial volume (ECV), and encephalization quotient (EQ) used for each extant and extinct species studied and their associated references.
See Supplementary file 3 for the details of ECV measurement conducted in this study.
- https://cdn.elifesciences.org/articles/108268/elife-108268-supp2-v1.xlsx
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Supplementary file 3
Endocranial volume (ECV) measured on specimens of various extant species.
Specimens are from the anatomical collections of the Museum für Naturkunde of Berlin, Germany. We used Chia seeds, with a calculated reference of 1g=1.22 ml. We calculated the encephalization quotient (EQ) using a reference brain volumic mass of 1.036 g.cm-3 (Ebinger, 1974) and the following formula (Boddy et al., 2012): EQ=(1.036×ECV)/(0.056×(BodyMass)^0.746)
- https://cdn.elifesciences.org/articles/108268/elife-108268-supp3-v1.xlsx
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Supplementary file 4
Calculated limbs proportions for the studied extinct species.
See Supplementary file 2 for the associated mean body masses, mean encephalization quotient (EQ), and references from where we extracted the photographs used to measure the postcranial lengths. NA = not applicable
- https://cdn.elifesciences.org/articles/108268/elife-108268-supp4-v1.xlsx
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Supplementary file 5
Complete results of statistical analysis.
- https://cdn.elifesciences.org/articles/108268/elife-108268-supp5-v1.xlsx
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MDAR checklist
- https://cdn.elifesciences.org/articles/108268/elife-108268-mdarchecklist1-v1.docx
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Source data 1
Raw behavioral and kinematic data, including the absolute speed, touchdowns and lift-offs used to quantify the duty factors and gait types, and body lengths measurements used to quantify the relative speed, by individual.
- https://cdn.elifesciences.org/articles/108268/elife-108268-data1-v1.xlsx
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Kinematics and morphological correlates of descent strategies in arboreal mammals suggest early upright postures in euprimates
eLife 14:RP108268.
https://doi.org/10.7554/eLife.108268.3
