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Conepatus chinga

Adult, Extant, Skeleton, Postcranium

Alt Name:
Molina’s hog-nosed skunk
Location:
Mammifères et Oiseaux, Museum National d'Histoire Naturelle
Specimen ID:
CG 1897-432
Additional Media:
This is a scan of Conepatus chinga. Wild caught. If you use this scan in a study, paper: do not forget to acknowledge the collection (Mammifères et Oiseaux, Museum National d'Histoire Naturelle), the curator (Géraldine Véron), and the ‘plate-forme de morphométrie’ of the UMS 2700 (CNRS, MNHN) for access to the surface scanner as well as myself for scanning (A.-C. Fabre). Furthermore, a final version of the publication using this scan must be send to Géraldine Véron (veron@mnhn.fr).
Year:
2013
Authors:
Fabre A.-C., R. Cornette, S. Peigné and A. Goswami
Journal:
Biological Journal of the Linnean Society 110(1):91-103
In the majority of mammals, the limbs are positioned under the body and play an important role in gravitational support, allowing the transfer of the load and providing stability to the animal. For this reason, an animal’s body mass likely has a significant effect on the shape of its limb bones. In the present study, we investigate the influence of body mass variation on the shape of the three long bones of the forelimb in a group of closely-related species of mammals: the musteloid carnivorans. We use geometric morphometric techniques to quantify forelimb shape; then estimate phylogenetic signal in the shape of each long bone; and, finally, we apply an independent contrasts approach to assess evolutionary associations between forelimb shape and body mass. The results obtained show that body mass evolution is tightly coordinated with the evolution of forelimb shape, although not equally in all elements. In particular, the humeral and radial shapes of heavier species appear better suited for load bearing and load transmission than the ulna. Nevertheless, our results also show that body mass influences only part of forelimb long bone shape and that other factors, such as locomotor ecology, must be considered to fully understand forelimb evolution.

Link:
http://onlinelibrary.wiley.com/doi/10.1111/bij.12103/abstract

Year:
2013
Authors:
Polly P.D., A.M. Lawing, A.-C. Fabre and A. Goswami
Journal:
Hystrix 24(1):1-9
Phylogenetic Principal Components Analysis (pPCA) is a recently proposed method for ordinating multivariate data in a way that takes into account the phylogenetic non-independence among species means. We review this method in terms of geometric morphometric shape analysis and compare its properties to ordinary principal components analysis (PCA). We find that pPCA produces a shape space that preserves the Procrustes distances between objects, that allows shape models to be constructed, and that produces scores that can be used as shape variables for most purposes. Unlike ordinary PCA scores, however, the scores on pPC axes are correlated with one another and their variances do not correspond to the eigenvalues of the phylogenetically corrected axes. The pPC axes are oriented by the non-phylogenetic component of shape variation, but the positioning of the scores in the space retains phylogenetic covariance making the visual information presented in plots a hybrid of non-phylogenetic and phylogenetic. Presuming that all pPCA scores are used as shape variables, there is no difference between them and PCA scores for the construction of distance-based trees (such as UPGMA), for morphological disparity, or for ordinary multivariate statistical analyses (so long as the algorithms are suitable for correlated variables). pPCA scores yield different trait-based trees (such as maximum likelihood trees for continuous traits) because the scores are correlated and because the pPC axes differ from PC axes. pPCA eigenvalues represent the residual shape variance once the phylogenetic covariance has been removed (though there are scaling issues), and as such they provide information on covariance that is independent of phylogeny. Tests for modularity on pPCA eigenvalues will therefore yield different results than ordinary PCA eigenvalues. pPCA can be considered another tool in the kit of geometric morphometrics, but one whose properties are more difficult to interpret than ordinary PCA

Link:
http://www.italian-journal-of-mammalogy.it/article/view/6383

Year:
2014
Authors:
Fabre A.-C., A. Goswami, S. Peigné, and R. Cornette
Journal:
Journal of Anatomy 225(1):19-30
The forelimb forms a functional unit that allows a variety of behaviours and needs to be mobile, yet at the
same time stable. Both mobility and stability are controlled, amongst others, at the level of the elbow joint.
This joint is composed of the humero-ulnar articulation, mainly involved during parasagittal movements; and
the radio-ulnar articulation, mainly allowing rotation. In contrast, the humero-radial articulation allows both
movements of flexion

extension and rotation. Here, we study the morphological integration between each
bone of the forelimb at the level of the entire arm, as well as at the elbow joint, in musteloid carnivorans. To
do so, we quantitatively test shape co-variation using surface 3D geometric morphometric data. Our results show that morphological integration is stronger for bones that form functional units. Different results are obtained depending on the level of investigation: for the entire arm, results show a greater degree of shape co-variation between long bones of the lower arm than between the humerus and either bone of the lower arm. Thus, at this level the functional unit of the lower arm is comprised of the radius and ulna, permitting rotational movements of the lower arm. At the level of the elbow, results display a stronger shape co-variation between bones allowing flexion and stability (humerus and ulna) than between bones allowing mobility (ulna and radius and humerus and radius). Thus, the critical functional unit appears to be the articulation between the humerus and ulna providing the stability of the joint

Link:
http://www.ncbi.nlm.nih.gov/pubmed/24836555

Year:
2015
Authors:
Fabre A.-C., M. J. Salesa, R. Cornette, M. Antón. J. Morales and S. Peigné
Journal:
The Science of Nature 102:30
Inferences of function and ecology in extinct taxa have long been a subject of interest because it is fundamental to understand the evolutionary history of species. In this study, we use a quantitative approach to investigate the locomotor behaviour of Simocyon batalleri, a key taxon related to the ailurid family. To do so, we use 3D surface geometric morphometric approaches on the three long bones of the forelimb of an extant reference sample. Next, we test the locomotor strategy of S. batalleri using a leave-one-out cross-validated linear discriminant analysis. Our results show that S. batalleri is included in the morphospace of the living species of musteloids. However, each bone of the forelimb appears to show a different functional signal suggesting that inferring the lifestyle or locomotor behaviour of fossils can be difficult and dependent on the bone investigated. This highlights the importance of studying, where possible, a maximum of skeletal elements to be able to make robust inferences on the lifestyle of extinct species. Finally, our results suggest that S. batalleri may be more arboreal than previously suggested.

Link:
http://link.springer.com/article/10.1007%2Fs00114-015-1280-9

Year:
2015
Authors:
Fabre A.-C., R. Cornette, A. Goswami and S. Peigné
Journal:
Journal of Anatomy 226:596-610
Convergence in morphology can result from evolutionary adaptations in species living in environments with similar selective pressures. Here, we investigate whether the shape of the forelimb long bones has converged in environments imposing similar functional constraints, using musteloid carnivores as a model. The limbs of quadrupeds are subjected to many factors that may influence their shape. They need to support body mass without collapsing or breaking, yet at the same time resist the stresses and strains induced by locomotion. This likely imposes strong constraints on their morphology. Our geometric morphometric analyses show that locomotion, body mass and phylogeny all influence the shape of the forelimb. Furthermore, we find a remarkable convergence between: (i) aquatic and semi-fossorial species, both displaying a robust forelimb, with a shape that improves stability and load transfer in response to the physical resistance imposed by the locomotor environment; and (ii) aquatic and arboreal/semi-arboreal species, with both groups displaying a broad capitulum. This augments the degree of pronation/supination, an important feature for climbing as well as grasping and manipulation ability, behaviors common to aquatic and arboreal species. In summary, our results highlight how musteloids with different locomotor ecologies show differences in the anatomy of their forelimb bones. Yet, functional demands for limb movement through dense media also result in convergence in forelimb long-bone shape between diverse groups, for example, otters and badgers.

Link:
http://onlinelibrary.wiley.com/doi/10.1111/joa.12315/abstract

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