Morphological Integration of Native South American Ungulate Mandibles. A Tribute to D’arcy Thompson in the Centennial of “On Growth and Form

Cassini, Guillermo Hernán; Muñoz, Nahuel Antu; Vizcaı́no, Sergio F.

doi:10.5710/peapa.07.12.2017.253

Cited by 4 publications

(4 citation statements)

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“…Much of the ecomorphological literature about bovid diets have used linear measurements of craniomandibular features (e.g., Solounias et al 1995 ; Spencer 1995 ; Mendoza and Palmqvist 2006 ). More recently, several studies have utilized landmark-based, geometric-morphometric analyses to study ungulate jaw shape in relation to diet and function ( Raia et al 2010 ; Cassini 2013 ; Cassini et al 2017 ; Forrest et al 2018 ; Cassini and Toledo 2020 ). Results of these analyses show that mandibular shape is useful for reconstructing the ecology of extinct taxa.…”

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confidence: 99%

Geometric morphometrics of mandibles for dietary differentiation of Bovidae (Mammalia: Artiodactyla)

2021

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The mammalian family Bovidae has been widely studied in ecomorphological research, with important applications to paleoecological and paleohabitat reconstructions. Most studies of bovid craniomandibular features in relation to diet have used linear measurements. In this study, we conduct landmark-based geometric-morphometric analyses to evaluate whether different dietary groups can be distinguished by mandibular morphology. Our analysis includes data for 100 species of extant bovids, covering all bovid tribes and two dietary classifications. For the first classification with three feeding categories, we found that browsers (including frugivores), mixed feeders, and grazers are moderately well separated using mandibular shape. A finer dietary classification (frugivore, browser, browser-grazer intermediate, generalist, variable grazer, obligate grazer) proved to be more useful for differentiating dietary extremes (frugivores and obligate grazers) but performed equally or less well for other groups. Notably, frugivorous bovids, which belong in tribe Cephalophini, have a distinct mandibular shape that is readily distinguished from all other dietary groups, yielding a 100% correct classification rate from jackknife cross-validation. The main differences in mandibular shape found among dietary groups are related to the functional needs of species during forage prehension and mastication. Compared to browsers, both frugivores and grazers have mandibles that are adapted for higher biomechanical demand of chewing. Additionally, frugivore mandibles are adapted for selective cropping. Our results call for more work on the feeding ecology and functional morphology of frugivores and offer an approach for reconstructing the diet of extinct bovids.

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confidence: 99%

Geometric morphometrics of mandibles for dietary differentiation of Bovidae (Mammalia: Artiodactyla)

2021

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“…The angles between these vectors were compared under the null hypothesis of orthogonality (Drake & Klingenberg, ; Klingenberg & Marugán‐Lobón, ). When these angles are close to zero, the shape change vectors are similar and consequently explain a similar shape variation (see Cassini, Muñoz, & Vizcaino, ; Segura, Cassini, & Prevosti, and references therein).…”

Section: Methodsmentioning

confidence: 96%

A geometric morphometric approach to the analysis of skull shape in Triassic dicynodonts (Therapsida, Anomodontia) from South America

Ordóñez

Cassini

Vizcaı́no

et al. 2019

Journal of Morphology

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Dicynodont therapsids were a major component of the Permo-Triassic terrestrial ecosystems across Pangea and have been regarded as specialized herbivores. In South America, the group was represented by several taxa of the clade Kannemeyeriiformes spanning from the Middle to the Late Triassic. In order to evaluate if cranial differences among taxa are potentially related to differences in feeding function, we performed a geometric morphometric analysis on 28 South American dicynodont crania.We digitized 19 cranial landmarks and conducted generalized Procrustes analysis, principal component analysis (PCA), principal component analysis between groups (bg-PCA), and a branch weighted squared-change parsimony approach. Phylogenetic inertia was not a significant driver of cranial shape evolution in the group, whereas PCA and bg-PCA support that major morphological shape differences are concentrated in the preorbital region (relative length of the snout and width of the caniniform process), in the position of quadrate condyle in relation to the caniniform process, and in the increase in the intertemporal surface area. In this context, tusked Dinodontosaurus, "Kannemeyeria," and Vinceria have relatively smaller adductor attachment areas and input moment arm than younger taxa lacking tusks, such as Ischigualastia, Stahleckeria, and Jachaleria. Differences in cranial morphology in later dicynodonts reflect modifications in feeding mechanics, probably due to changes in food resources (vegetation) in their habitats toward the end of the Triassic.

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“…We defined Block-1 as mandibular shape ( i.e ., landmark configurations) and Block-2 as continuous diet characters ( i.e ., the logit transformed diet proportions matrix; see Olsen, 2017 ; Fernandez Blanco, Cassini & Bona, 2018 ; Cassini & Toledo, 2021 ). PCA, PLS and Regressions produce vectors in shape space in different directions which were compared (angular comparison; see Segura, Prevosti & Cassini, 2013 ; Cassini, Muñoz & Vizcaino, 2017 ; Segura et al, 2017 ). The angles between these vectors were computed and compared using the angleTest function of Morpho package (see Li, 2011 ).…”

Section: Methodsmentioning

confidence: 99%

A three-dimensional geometric morphometric analysis of the morphological transformation of Caiman lower jaw during post-hatching ontogeny

Blanco

Cassini

Bona

2023

PeerJ

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Shape ontogenetic changes of the lower jaw in crocodylians are poorly understood. In order to answer some questions related to the inter- and intraspecific morphological variation of the mandible of two extant Caiman species, we performed a three-dimensional geometric morphometric approach. For this purpose, we used landmarks and semilandmarks on two ontogenetic mandibular series of 48 and 15 post-hatching specimens of C. yacare and C. latirostris, respectively. We have also examined the relationship between these anatomical transformations and ontogenetic shifts in diet. We performed a principal component analysis (PCA) for the two species, and regression and partial least squares (PLS) analyses for each species, separately. As a result, species were segregated along the PC1 with specimens of C. yacare showing more gracile mandibles, and specimens of C. latirostris more robust ones. The PC2 and regression analyses showed an age gradient and represented ontogenetic shape changes. Adult caiman mandibles are higher and wider than juvenile ones, and shape changes are more conspicuous in C. latirostris. The PLS analyses showed a significant relationship between shape and diet. Morphological changes of the PLS1 of block-1 match with those of the regression analysis for both species. We have detected morphological transformations in areas where the musculature in charge of mandibular movements is attached. Common morphological changes occurring during ontogeny seem to reflect the same mechanical properties required for crushing and killing in both species, driven by an ontogenetic shift in the diet from invertebrates to vertebrates. Additionally, interspecific differences were also found to be correlated to ontogenetic changes in diet and could be related to dissimilar feeding mechanical requirements (e.g., stiffness and toughness of the item consumed), and to different habitat preferences. Robust mandibles would be more suitable for shallow and fully vegetated environments, as it can be seen in C. latirostris, whereas slender jaws seem to be more suitable for more aquatic species such as C. yacare.

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Morphological Integration of Native South American Ungulate Mandibles. A Tribute to D’arcy Thompson in the Centennial of “On Growth and Form

Cited by 4 publications

References 53 publications

Geometric morphometrics of mandibles for dietary differentiation of Bovidae (Mammalia: Artiodactyla)

Geometric morphometrics of mandibles for dietary differentiation of Bovidae (Mammalia: Artiodactyla)

A geometric morphometric approach to the analysis of skull shape in Triassic dicynodonts (Therapsida, Anomodontia) from South America

A three-dimensional geometric morphometric analysis of the morphological transformation of Caiman lower jaw during post-hatching ontogeny

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