Hind Limb Bone Proportions Reveal Unexpected Morphofunctional Diversification in Xenarthrans

Marshall, Sarah K.; Spainhower, Kyle B.; Sinn, Brandon T.; Diggins, Thomas P.; Butcher, Michael T.

doi:10.1007/s10914-021-09537-w

Cited by 11 publications

(18 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although not reaching significance, Imin 50 , Imin Aver , and CSA Aver value distributions are lower for slow arboreal xenarthrans. Conversely, the higher femoral strength (Imax and CSA) exhibited by armadillos is consistent with high stresses deriving from fossoriality and digging Milne and O'Higgins 2012;Marshall et al 2021). Thus, the hindlimb strength required by locomotor ecology drives the distribution of Imax and CSA, as suggested by intermediate values in non-slow arboreal anteaters.…”

Section: Femoral Cross-sectional Propertiesmentioning

confidence: 63%

“…3k). All these features can be associated with their strenuous digging style Milne and O'Higgins 2012;Marshall et al 2021). The proximal epiphysis of taxa with low PC1 scores is characterized by reduced trochanters (with the greater extending far laterally), a large, curved and proximally-directed head (i.e., smaller neck angle), and a shorter neck.…”

Section: Femoral External Shapementioning

confidence: 99%

“…It is also a condition associated with arboreal habits (Sargis 2002). Strong hip flexors may nevertheless be needed for suspensory locomotion in 'tree sloths' (Mendel 1985a;Spainhower et al 2021), which can be achieved through the modification of muscles not attaching on the third trochanter (Marshall et al 2021). Similar to what was found in the humerus (see above), the degree of torsion in the femur is challenging to interpret.…”

Section: Femoral External Shapementioning

confidence: 99%

“…Typical femoral morphological adaptations in xenarthrans more specialized for digging (i.e. armadillos) are mainly related to fossoriality, with hindlimbs playing a role in anchoring the posterior portion of the body to the soil, and the fossorial behaviors are obviously not present in arboreal environment (Marshall et al 2021). Although hindlimbs of Cyclopes supposedly need to be adapted to provide support for arboreal digging, pending additional experimental data at this stage we cannot frame the higher DA prox of Cyclopes in a locomotor ecological explanation.…”

Section: Femoral Trabecular Architecturementioning

confidence: 99%

“…Here, we combine the three types of variables to gain insights into functional morphological convergence driven by slow arboreal locomotor ecology. Several traits are shared by the humeri and femora of slow arboreal xenarthrans (e.g., White 1993;Straehl et al 2013;Toledo et al 2013Toledo et al , 2015Amson and Nyakatura 2018b;de Oliveira and Santos 2018;Marshall et al 2021) including features related to the anatomical scales and/or techniques employed in this work. Indeed, humeral and/or femoral features shared by slow arboreal xenarthrans have been highlighted analysing the external 3D shape (Milne and O'Higgins 2012;Mielke et al 2018a), the diaphyseal structure (Patel et al 2013;Marchi et al 2016;Amson and Nyakatura 2018a;Montañez-Rivera et al 2018;Alfieri et al 2021) Fig.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Integrative Approach Uncovers New Patterns of Ecomorphological Convergence in Slow Arboreal Xenarthrans

et al. 2021

View full text Add to dashboard Cite

Identifying ecomorphological convergence examples is a central focus in evolutionary biology. In xenarthrans, slow arboreality independently arose at least three times, in the two genera of ‘tree sloths’, Bradypus and Choloepus, and the silky anteater, Cyclopes. This specialized locomotor ecology is expectedly reflected by distinctive morpho-functional convergences. Cyclopes, although sharing several ecological features with ‘tree sloths’, do not fully mirror the latter in their outstandingly similar suspensory slow arboreal locomotion. We hypothesized that the morphology of Cyclopes is closer to ‘tree sloths’ than to anteaters, but yet distinct, entailing that slow arboreal xenarthrans evolved through ‘incomplete’ convergence. In a multivariate trait space, slow arboreal xenarthrans are hence expected to depart from their sister taxa evolving toward the same area, but not showing extensive phenotypical overlap, due to the distinct position of Cyclopes. Conversely, a pattern of ‘complete’ convergence (i.e., widely overlapping morphologies) is hypothesized for ‘tree sloths’. Through phylogenetic comparative methods, we quantified humeral and femoral convergence in slow arboreal xenarthrans, including a sample of extant and extinct non-slow arboreal xenarthrans. Through 3D geometric morphometrics, cross-sectional properties (CSP) and trabecular architecture, we integratively quantified external shape, diaphyseal anatomy and internal epiphyseal structure. Several traits converged in slow arboreal xenarthrans, especially those pertaining to CSP. Phylomorphospaces and quantitative convergence analyses substantiated the expected patterns of ‘incomplete’ and ‘complete’ convergence for slow arboreal xenarthrans and ‘tree sloths’, respectively. This work, highlighting previously unidentified convergence patterns, emphasizes the value of an integrative multi-pronged quantitative approach to cope with complex mechanisms underlying ecomorphological convergence.

show abstract

Section: Femoral Cross-sectional Propertiesmentioning

confidence: 63%

Section: Femoral External Shapementioning

confidence: 99%

Section: Femoral External Shapementioning

confidence: 99%

Section: Femoral Trabecular Architecturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Integrative Approach Uncovers New Patterns of Ecomorphological Convergence in Slow Arboreal Xenarthrans

et al. 2021

View full text Add to dashboard Cite

show abstract

Three toes and three modes: Dynamics of terrestrial, suspensory, and vertical locomotion in brown‐throated three‐toed sloths (Bradypodidae, Xenarthra)

et al. 2023

Self Cite

View full text Add to dashboard Cite

Living sloths exhibit numerous anatomical specializations towards inverted quadrupedalism, however, previous studies have noted a more varied locomotor repertoire than previously anticipated. In this study, we present spatiotemporal gait characteristics and triaxial kinetic data from the brown‐throated three‐toed sloth (Bradypus variegatus) across three locomotor modes: terrestrial quadrupedal “crawling”, suspensory walking, and vertical climbing. Compared to quadrupedal crawling and suspensory walking, B. variegatus adopted longer contact times and stride durations, larger duty factors, and greater speed during vertical climbing. Net fore‐aft impulses were significantly greater during vertical climbing in both limb pairs than in quadrupedal crawling and suspensory walking. Functionally, during quadrupedal crawling and vertical climbing, both limb pairs served propulsive roles, while differentiation between a propulsive forelimb and braking hindlimb was observed during suspension. Net tangential forces differentiated vertical climbing kinetics from the other modes of locomotion, with the introduction of bidirectional pulling and pushing forces in the forelimb and hindlimb, respectively. The net mediolateral impulses were similar in vertical climbing and quadrupedal crawling as both limb pairs directed forces in one direction, whereas during suspensory walking, the laterally dominant forelimb was opposed by the medially dominant hindlimb. In total, this study provides novel data on the diverse locomotor dynamics in a slow‐moving arboreal tetrapod and posits new testable hypotheses about the neuroplasticity and ease of transitioning between locomotor behaviors. The strikingly similar kinetic profiles of quadrupedal crawling and suspensory walking compared to vertical climbing suggest shared neuromuscular and mechanical demands between these mirrored locomotor modes.

show abstract

The carnivoran adaptive landscape reveals functional trade-offs among the skull, appendicular, and axial skeleton

Law,

Hlusko,

Tseng

2024

Preprint

View full text Add to dashboard Cite

Analyses of form-function relationships are widely used to understand links between morphology, ecology, and species fitness across macroevolutionary scales. However, few have investigated functional trade-offs and covariance among functional traits within and between the skull, limbs, and vertebral column simultaneously. In this study, we investigated the adaptive landscape of skeletal form and function in carnivorans to test how functional trade-offs between these skeletal regions contribute to ecological adaptations and the topology of the landscape. We found that functional traits derived from carnivoran skeletal regions exhibit trade-offs and covariation across their performance surfaces, particularly in the appendicular and axial skeletons. These functional trade-offs and covariation corresponded as specializations to different adaptive landscapes when optimized by locomotor mode, diet, or family. Lastly, we found that the topologies of the optimized adaptive landscapes and underlying performance surfaces are largely characterized as smooth, gradual gradients between regions of low and high adaptive zones rather than as rugged, multipeak landscapes. Our results suggest that carnivorans may already occupy a broad adaptive zone as part of a larger mammalian adaptive landscape that masks the form and function relationships of skeletal traits.

show abstract

Hind Limb Bone Proportions Reveal Unexpected Morphofunctional Diversification in Xenarthrans

Cited by 11 publications

References 65 publications

Integrative Approach Uncovers New Patterns of Ecomorphological Convergence in Slow Arboreal Xenarthrans

Integrative Approach Uncovers New Patterns of Ecomorphological Convergence in Slow Arboreal Xenarthrans

Three toes and three modes: Dynamics of terrestrial, suspensory, and vertical locomotion in brown‐throated three‐toed sloths (Bradypodidae, Xenarthra)

The carnivoran adaptive landscape reveals functional trade-offs among the skull, appendicular, and axial skeleton

Contact Info

Product

Resources

About