Sparassodonta ha sido descripto como un grupo de predadores diverso en lo que respecta a dieta, i... more Sparassodonta ha sido descripto como un grupo de predadores diverso en lo que respecta a dieta, incluyendo desde formas omnívoras a netamente carnívoras o con hábitos carroñeros-osífragos. Estudios previos se han basado en descripciones cualitativas e índices dentarios para realizar estas inferencias. En este trabajo, se estudió una muestra de 541 especímenes depredadores actuales (145 de Metatheria y 396 de Carnivora), representantes de un amplio rango de dietas (hipercarnívoros, mesocarnívoros, omnívoros, herbívoros, insectívoros) y 13 especímenes del Mioceno pertenecientes al Orden Sparassodonta. Utilizando morfometría geométrica, se analizó la variación de forma de la mandíbula y el molar "carnicero" inferior. Mediante un análisis discriminante basado en los componentes principales de forma (variables dependientes) y la dieta (variable categórica independiente), se obtuvieron las siguientes asignaciones dietarias: Arctodictis munizi (Mercerat), A. sinclairi (Marshall) y Borhyaena tuberata (Ameghino), hipercarnívoros con altas probabilidades (más de 80% por especie); Prothylacynus patagonicus (Ameghino), intermedio entre hipercarnívoro (48%) y mesocarnívoro (44%); y Cladosictis patagonica (Ameghino) y Sipalocyon gracilis (Ameghino), mesocarnívoros con altas probabilidades (más de 75%). Los clasificados como hipercarnívoros presentaron talónidos altamente reducidos, carniceros ubicados posteriormente y mandíbulas robustas; los asignados al grupo de mesocarnívoros talónidos poco reducidos y ramas horizontales más delgadas y curvas; mientras que P. patagonicus presentó una morfología intermedia, con talónido reducido y rama horizontal delgada. Los resultados son congruentes y refuerzan las inferencias obtenidas en trabajos previos; sin embargo, C. patagonica y P. patagonicus son aquí descriptos como menos hipercarnívoros que lo evidenciado exclusivamente por índices dentarios.Sesiones libresFacultad de Ciencias Naturales y Muse
In the last few decades, the relationships between form and locomotory habits of extant and fossi... more In the last few decades, the relationships between form and locomotory habits of extant and fossil predators have been studied mainly through morphometric techniques (Van Valkenburgh, 1987; MacLeod & Rose, 1993; Andersson, 2003, 2004; Schutz & Guralnick, ...
Cetaceans swim by the alternate action of their epiaxial and hypaxial muscles and their propulsiv... more Cetaceans swim by the alternate action of their epiaxial and hypaxial muscles and their propulsive movements are confined to the vertical plane. Changes in the shape and mechanical properties of vertebrae strongly affect their function during oscillatory swimming. The first objective of this study was to provide a quantitative characterization of vertebral morphology in representatives of the Delphinidae and Pontoporiidae families. A novel morphometric approach was applied, using nine vertebral measurements and three indices. The second objective was to assess the relationship between morphology and both habitat and size through regression analyses. The phylogenetic structure of the distribution of characters was also explored by estimating phylogenetic signal. No relationship was found between morphology and habitat or size, but vertebral measurements and indices showed a significant phylogenetic signal. Morphological profiles indicated that coastal and oceanic delphinid species ha...
ABSTRACT South American caviomorph rodents comprise four major lineages encompassing wide taxonom... more ABSTRACT South American caviomorph rodents comprise four major lineages encompassing wide taxonomic and ecological diversity, but the morphological diversity of their postcranial skeleton has not been thoroughly explored using phylogenetic comparative methods. The main goal of this work is to analyze their humerus using geometric morphometrics in a phylogenetic context and attempt to tease apart the influence of locomotory preferences and shared evolutionary history on morphological variation. We examined 28 genera in 9 families representing all major clades. Humeral shape was captured by 13 landmarks and four semilandmarks in 2D. In the morphospace of the first two principal components, most taxa were located near the origin along both axes. Fossorial octodontoids were apart from this central group. Most caviids were separated in one extreme of the morphospace; the specialized digging ctenomyid Ctenomys, the fossorial chinchillid Lagostomus and the generalized cavioid Cuniculus were located at the opposite end. Phylogenetic signal was significant. Regressions of shape on size were not significant; regression of shape on habit was significant for raw data and not significant after phylogenetic control. Humeral shape variation was primarily associated with the phylogenetic structure of the group; additionally, some morphological traits were associated with particular habits and interpreted as functional specializations. This association between humeral shape and both phylogeny and habit at different hierarchical levels suggests early ecomorphological diversification of caviomorphs.
ABSTRACT Caviomorph rodents represent an excellent model to explore morphological diversification... more ABSTRACT Caviomorph rodents represent an excellent model to explore morphological diversification on a macroevolutionary scale, as they are ecologically and morphologically diverse. We analysed cranial shape variation using geometric morphometrics and phylogenetic comparative methods. Most variation involved the shape of the rostrum, basicranium, and cranial vault, and clearly matched the phylogenetic structure. At the same time, a strong allometric pattern was associated with the length of the rostrum and cranial vault, size of the auditory bulla, and depth of the zygomatic arch. After accounting for size influence, and taking phylogenetic structure into account, shape variation was significantly associated with habitat. Our results highlight the presence of complex relationships between morphological, phylogenetic, and ecological dimensions in the diversification of the caviomorph cranium
Abstract †Prospaniomys is a basal octodontoid recorded in
the early Miocene in Patagonia (Argenti... more Abstract †Prospaniomys is a basal octodontoid recorded in the early Miocene in Patagonia (Argentina; Colhuehuapian SALMA). Nearly complete cranial and mandibular remains known for this genus provide a unique opportunity to explore its paleobiology. For this, masticatory muscles were reconstructed and craniomandibular shape variation assessed. While such reconstruction indicates that most masticatory muscles would have presented moderate development, both the masseter lateralis and posterior muscles were poorly developed. In contrast, we found that the temporalis muscle was well developed, while conspicuous postorbital constriction, postorbital processes, and superior temporal lines revealed a substantial orbital portion of this muscle. According to geometric morphometric results, craniomandibular shape was interpreted as generalized. Features such as shortened palate, narrower bizygomatic width, orthodont incisors, enlarged incisive foramina, and a shallow jaw could be linked to epigean habits. The moderate development of auditory bullae in Prospaniomys suggests that it is unlikely that it may have lived in extreme arid environments. Additionally, based on its generalized dental morphology, an omnivorous or generalized herbivorous diet that may have included leaves, fruit, and potentially animal matter was inferred. By the early Miocene, Patagonia experienced the initial expansion stage of arid-adapted vegetation, with grasses present in low amounts and abundant forests. Generalized habits and soft and nonabrasive diet suggest that Prospaniomys was possibly associated with more closed environments. Morphology alone cannot be used as an environmental proxy, but it could undoubtedly contribute to the interpretations based on data provided by paleobotanical and geological frameworks in studies on the evolution of environments.
tWe assessed the influence of a variety of aspects of locomotion and ecology including gait and l... more tWe assessed the influence of a variety of aspects of locomotion and ecology including gait and locomotortypes, maximal running speed, home range, and body size on postcranial shape variation in small tomedium-sized mammals, employing geometric morphometric analysis and phylogenetic comparativemethods. The four views analyzed, i.e., dorsal view of the penultimate lumbar vertebra, lateral view ofthe pelvis, posterior view of the proximal femur and proximal view of the tibia, showed clear phylogeneticsignal and interesting patterns of association with movement. Variation in home range size was relatedto some tibia shape changes, while speed was associated with lumbar vertebra, pelvis and tibia shapechanges. Femur shape was not related to any locomotor variables. In both locomotor type and high-speedgait analyses, locomotor groups were distinguished in both pelvis and tibia shape analyses. These resultssuggest that adaptations to both typical and high-speed gaits could explain a considerable portion ofthe shape of those elements. In addition, lumbar vertebra and tibia showed non-significant relationshipswith body mass, which suggests that they might be used in morpho-functional analyses and locomotorinferences on fossil taxa, with little or no bias for body size. Lastly, we observed morpho-functionalconvergences among several mammalian taxa and detected some taxa that achieve similar locomotorfeatures following different morphological paths.
Mustelids are a morphofunctionally diversified group. However, there are no descriptions of the p... more Mustelids are a morphofunctionally diversified group. However, there are no descriptions of the postcranial musculature of South American mustelid species except for some comments from the 19th century. Here, we present the first description of the myology of the hind limbs, and lumbar, sacral, and caudal regions of the lesser grison (Galictis cuja), a short-legged South American mustelid, including muscle maps and weight data. We interpret the function and the evolution of several muscular features within a comparative framework and through the optimization of these traits onto a phylogeny. The configuration of the axial musculature (e.g., m. quadratus lumborum with short bundles, heavy iliocostalis, and forward originated sacrocaudalis dorsalis) and the presence of strong ankle musculature are features shared with mustelines and, to a lesser degree, with other musteloids. These could be related to a high mobility of the axial skeleton and strong control of the movement of the ankle joint, in relation to the acquisition of epigean bounding gaits, a crouched locomotion, and enhanced maneuverability inside burrows. We recorded many phylogenetically significant traits, shared with other arctoids (e.g., subdivision of m. gluteus profundus and semimembranosus, presence of a single belly for m. sartorius, and absence of articularis coxae) or exclusively musteloids (e.g., frequent fusion between m. piriformis and gluteus medius). Some features (e.g., restricted origin of the caudal belly of the m. semitendinosus, absence of gluteofemoralis, and unusually complex fibularis brevis) seem to be derived conditions acquired in some mustelid clades. Our results sustain the value of myological data for functional and phylogenetic studies.
"Morphological variation is one of the most studied dimensions of evolutionary biology, given its... more "Morphological variation is one of the most studied dimensions of evolutionary biology, given its close relationship with the ecological aspects of biological
diversification. In this work we examine the differences between the use of two- and three-dimensional morphometric techniques for the analysis of macroevolutionary patterns of morphological variation in the mandible of the
South American caviomorph rodents, which displays varying degrees of hystricognathy. The variation patterns were similar for 2D and 3D coordinate datasets. However, phylogenetic comparative statistical analyses showed
widely different results for mandible variation. Both the phylogenetic signal values and the results of phylogenetic regressions were markedly different between the two macroevolutionary mandible datasets. This suggests that
the inclusion of the third coordinate to characterize a hystricognathous mandible may lead to completely different interpretations concerning the processes that could be regulating the morphological diversification of the caviomorph mandible. We also compare these results with the 2D and 3D macroevolutionary patterns of variation in cranial shape and the intra-specific mandible variation. The variation patterns were similar for 2D and 3D coordinate for all these comparative datasets. The differing results
obtained at different evolutionary scales, give strength to the statement about careful selection of data not only in studies of morphological variation in caviomorphs but also for other groups of organisms."
In this study, we analysed locomotory habits in extant predators and Sparassodonta species throug... more In this study, we analysed locomotory habits in extant predators and Sparassodonta species through geometric morphometric techniques and discriminant analyses of the distal humerus in anterior view, proximal ulna in lateral view, and tibia in proximal view. We included a wide sample of extant predators, and considered the phylogenetic and allometric structure in the data sets. We also included some Sparassodonta, a group of carnivorous metatherians that inhabited South America during the Cenozoic, and inferred their locomotory habits. Results suggest the presence of a close relationship between shape and locomotory habits, even after removing the shape component explained by phylogeny in the three postcranial elements. Terrestrial habits were inferred for Arctodictis sinclairi, Borhyaena tuberata, ‘Lycopsis’ longirostrus, and Thylacosmilus atrox. Some degree of cursoriality was highlighted in B. tuberata and T. atrox, and climbing abilities in ‘L.’ longirostrus, and to a lesser degree in B. tuberata. Scansorial habits were inferred for Cladosictis patagonica, Sipalocyon gracilis, Prothylacynus patagonicus, and Pseudonotictis pusillus, and in the case of C. patagonica, some digging ability was also tentatively inferred.
Ontogenetic allometries of craniomandibular and dental features linked to digging were analyzed i... more Ontogenetic allometries of craniomandibular and dental features linked to digging were analyzed in 5 species of the South American subterranean rodent Ctenomys (tuco-tucos). With the exception of upper incisor procumbency, variables showed high correlation with overall skull size. In particular, craniomandibular variables related to the production of bite forces at the incisors showed near-geometric similarity during postnatal growth and interspecific changes in early developmental stages resulting in different starting forms (lateral transposition). Such an interspecific pattern of change is similar to one previously reported to occur among living and extinct ctenomyid genera. These results suggest more evolutionary flexibility for changes in early ontogenetic stages and allow rejection of the hypothesis that interspecific shape differences in the skull of Ctenomys would be associated with differences in size alone.
Caviomorphs are a clade of South American rodents recorded at least since the
early Oligocene (> ... more Caviomorphs are a clade of South American rodents recorded at least since the early Oligocene (> 31.5 Ma) that exhibit ample eco-morphological variation. It has been proposed that phylogenetic structure is more important than ecological factors for understanding mandibular shape variation in this clade. This was interpreted as a result of the long-standing evolutionary history of caviomorphs and the early divergence of major lineages. In this work, we test this hypothesis through the analysis of morphological variation in the mandible of living and extinct species and compare this information with that obtained through comparative phylogenetic analyses. Our results support the hypothesis of early origin of mandibular variation; moreover, they suggest the conservation of early differentiated morphologies, which could indicate the existence of constrained evolutionary diversification
We analyzed mandible shape variation of 17 genera belonging to three superfamilies (Cavioidea, Ch... more We analyzed mandible shape variation of 17 genera belonging to three superfamilies (Cavioidea, Chinchilloidea, and Octodontoidea) of South American caviomorph rodents using geometric morphometrics. The relative influence of phylogeny and ecology on this variation was assessed using phylogenetic comparative methods. Most morphological variation was concentrated in condylar, coronoid, and angular processes, as well as the diastema. Features potentially advantageous for digging (i.e. high coronoid and condylar processes, relatively short angular process, and diastema) were present only in octodontoids; cavioids showed opposing trends, which could represent a structural constraint for fossorial habits. Chinchilloids showed intermediate features. Genera were distributed in the morphospace according to their classification into superfamilial clades. The phylogenetic signal for shape components was significant along phylogeny, whereas the relationship between mandibular shape and ecology was nonsignificant when phylogenetic structure was taken into account. An early evolutionary divergence in the mandible shape among major caviomorph clades would explain the observed strong phylogenetic influence on the variation of this structure.
Sparassodonta ha sido descripto como un grupo de predadores diverso en lo que respecta a dieta, i... more Sparassodonta ha sido descripto como un grupo de predadores diverso en lo que respecta a dieta, incluyendo desde formas omnívoras a netamente carnívoras o con hábitos carroñeros-osífragos. Estudios previos se han basado en descripciones cualitativas e índices dentarios para realizar estas inferencias. En este trabajo, se estudió una muestra de 541 especímenes depredadores actuales (145 de Metatheria y 396 de Carnivora), representantes de un amplio rango de dietas (hipercarnívoros, mesocarnívoros, omnívoros, herbívoros, insectívoros) y 13 especímenes del Mioceno pertenecientes al Orden Sparassodonta. Utilizando morfometría geométrica, se analizó la variación de forma de la mandíbula y el molar "carnicero" inferior. Mediante un análisis discriminante basado en los componentes principales de forma (variables dependientes) y la dieta (variable categórica independiente), se obtuvieron las siguientes asignaciones dietarias: Arctodictis munizi (Mercerat), A. sinclairi (Marshall) y Borhyaena tuberata (Ameghino), hipercarnívoros con altas probabilidades (más de 80% por especie); Prothylacynus patagonicus (Ameghino), intermedio entre hipercarnívoro (48%) y mesocarnívoro (44%); y Cladosictis patagonica (Ameghino) y Sipalocyon gracilis (Ameghino), mesocarnívoros con altas probabilidades (más de 75%). Los clasificados como hipercarnívoros presentaron talónidos altamente reducidos, carniceros ubicados posteriormente y mandíbulas robustas; los asignados al grupo de mesocarnívoros talónidos poco reducidos y ramas horizontales más delgadas y curvas; mientras que P. patagonicus presentó una morfología intermedia, con talónido reducido y rama horizontal delgada. Los resultados son congruentes y refuerzan las inferencias obtenidas en trabajos previos; sin embargo, C. patagonica y P. patagonicus son aquí descriptos como menos hipercarnívoros que lo evidenciado exclusivamente por índices dentarios.Sesiones libresFacultad de Ciencias Naturales y Muse
In the last few decades, the relationships between form and locomotory habits of extant and fossi... more In the last few decades, the relationships between form and locomotory habits of extant and fossil predators have been studied mainly through morphometric techniques (Van Valkenburgh, 1987; MacLeod & Rose, 1993; Andersson, 2003, 2004; Schutz & Guralnick, ...
Cetaceans swim by the alternate action of their epiaxial and hypaxial muscles and their propulsiv... more Cetaceans swim by the alternate action of their epiaxial and hypaxial muscles and their propulsive movements are confined to the vertical plane. Changes in the shape and mechanical properties of vertebrae strongly affect their function during oscillatory swimming. The first objective of this study was to provide a quantitative characterization of vertebral morphology in representatives of the Delphinidae and Pontoporiidae families. A novel morphometric approach was applied, using nine vertebral measurements and three indices. The second objective was to assess the relationship between morphology and both habitat and size through regression analyses. The phylogenetic structure of the distribution of characters was also explored by estimating phylogenetic signal. No relationship was found between morphology and habitat or size, but vertebral measurements and indices showed a significant phylogenetic signal. Morphological profiles indicated that coastal and oceanic delphinid species ha...
ABSTRACT South American caviomorph rodents comprise four major lineages encompassing wide taxonom... more ABSTRACT South American caviomorph rodents comprise four major lineages encompassing wide taxonomic and ecological diversity, but the morphological diversity of their postcranial skeleton has not been thoroughly explored using phylogenetic comparative methods. The main goal of this work is to analyze their humerus using geometric morphometrics in a phylogenetic context and attempt to tease apart the influence of locomotory preferences and shared evolutionary history on morphological variation. We examined 28 genera in 9 families representing all major clades. Humeral shape was captured by 13 landmarks and four semilandmarks in 2D. In the morphospace of the first two principal components, most taxa were located near the origin along both axes. Fossorial octodontoids were apart from this central group. Most caviids were separated in one extreme of the morphospace; the specialized digging ctenomyid Ctenomys, the fossorial chinchillid Lagostomus and the generalized cavioid Cuniculus were located at the opposite end. Phylogenetic signal was significant. Regressions of shape on size were not significant; regression of shape on habit was significant for raw data and not significant after phylogenetic control. Humeral shape variation was primarily associated with the phylogenetic structure of the group; additionally, some morphological traits were associated with particular habits and interpreted as functional specializations. This association between humeral shape and both phylogeny and habit at different hierarchical levels suggests early ecomorphological diversification of caviomorphs.
ABSTRACT Caviomorph rodents represent an excellent model to explore morphological diversification... more ABSTRACT Caviomorph rodents represent an excellent model to explore morphological diversification on a macroevolutionary scale, as they are ecologically and morphologically diverse. We analysed cranial shape variation using geometric morphometrics and phylogenetic comparative methods. Most variation involved the shape of the rostrum, basicranium, and cranial vault, and clearly matched the phylogenetic structure. At the same time, a strong allometric pattern was associated with the length of the rostrum and cranial vault, size of the auditory bulla, and depth of the zygomatic arch. After accounting for size influence, and taking phylogenetic structure into account, shape variation was significantly associated with habitat. Our results highlight the presence of complex relationships between morphological, phylogenetic, and ecological dimensions in the diversification of the caviomorph cranium
Abstract †Prospaniomys is a basal octodontoid recorded in
the early Miocene in Patagonia (Argenti... more Abstract †Prospaniomys is a basal octodontoid recorded in the early Miocene in Patagonia (Argentina; Colhuehuapian SALMA). Nearly complete cranial and mandibular remains known for this genus provide a unique opportunity to explore its paleobiology. For this, masticatory muscles were reconstructed and craniomandibular shape variation assessed. While such reconstruction indicates that most masticatory muscles would have presented moderate development, both the masseter lateralis and posterior muscles were poorly developed. In contrast, we found that the temporalis muscle was well developed, while conspicuous postorbital constriction, postorbital processes, and superior temporal lines revealed a substantial orbital portion of this muscle. According to geometric morphometric results, craniomandibular shape was interpreted as generalized. Features such as shortened palate, narrower bizygomatic width, orthodont incisors, enlarged incisive foramina, and a shallow jaw could be linked to epigean habits. The moderate development of auditory bullae in Prospaniomys suggests that it is unlikely that it may have lived in extreme arid environments. Additionally, based on its generalized dental morphology, an omnivorous or generalized herbivorous diet that may have included leaves, fruit, and potentially animal matter was inferred. By the early Miocene, Patagonia experienced the initial expansion stage of arid-adapted vegetation, with grasses present in low amounts and abundant forests. Generalized habits and soft and nonabrasive diet suggest that Prospaniomys was possibly associated with more closed environments. Morphology alone cannot be used as an environmental proxy, but it could undoubtedly contribute to the interpretations based on data provided by paleobotanical and geological frameworks in studies on the evolution of environments.
tWe assessed the influence of a variety of aspects of locomotion and ecology including gait and l... more tWe assessed the influence of a variety of aspects of locomotion and ecology including gait and locomotortypes, maximal running speed, home range, and body size on postcranial shape variation in small tomedium-sized mammals, employing geometric morphometric analysis and phylogenetic comparativemethods. The four views analyzed, i.e., dorsal view of the penultimate lumbar vertebra, lateral view ofthe pelvis, posterior view of the proximal femur and proximal view of the tibia, showed clear phylogeneticsignal and interesting patterns of association with movement. Variation in home range size was relatedto some tibia shape changes, while speed was associated with lumbar vertebra, pelvis and tibia shapechanges. Femur shape was not related to any locomotor variables. In both locomotor type and high-speedgait analyses, locomotor groups were distinguished in both pelvis and tibia shape analyses. These resultssuggest that adaptations to both typical and high-speed gaits could explain a considerable portion ofthe shape of those elements. In addition, lumbar vertebra and tibia showed non-significant relationshipswith body mass, which suggests that they might be used in morpho-functional analyses and locomotorinferences on fossil taxa, with little or no bias for body size. Lastly, we observed morpho-functionalconvergences among several mammalian taxa and detected some taxa that achieve similar locomotorfeatures following different morphological paths.
Mustelids are a morphofunctionally diversified group. However, there are no descriptions of the p... more Mustelids are a morphofunctionally diversified group. However, there are no descriptions of the postcranial musculature of South American mustelid species except for some comments from the 19th century. Here, we present the first description of the myology of the hind limbs, and lumbar, sacral, and caudal regions of the lesser grison (Galictis cuja), a short-legged South American mustelid, including muscle maps and weight data. We interpret the function and the evolution of several muscular features within a comparative framework and through the optimization of these traits onto a phylogeny. The configuration of the axial musculature (e.g., m. quadratus lumborum with short bundles, heavy iliocostalis, and forward originated sacrocaudalis dorsalis) and the presence of strong ankle musculature are features shared with mustelines and, to a lesser degree, with other musteloids. These could be related to a high mobility of the axial skeleton and strong control of the movement of the ankle joint, in relation to the acquisition of epigean bounding gaits, a crouched locomotion, and enhanced maneuverability inside burrows. We recorded many phylogenetically significant traits, shared with other arctoids (e.g., subdivision of m. gluteus profundus and semimembranosus, presence of a single belly for m. sartorius, and absence of articularis coxae) or exclusively musteloids (e.g., frequent fusion between m. piriformis and gluteus medius). Some features (e.g., restricted origin of the caudal belly of the m. semitendinosus, absence of gluteofemoralis, and unusually complex fibularis brevis) seem to be derived conditions acquired in some mustelid clades. Our results sustain the value of myological data for functional and phylogenetic studies.
"Morphological variation is one of the most studied dimensions of evolutionary biology, given its... more "Morphological variation is one of the most studied dimensions of evolutionary biology, given its close relationship with the ecological aspects of biological
diversification. In this work we examine the differences between the use of two- and three-dimensional morphometric techniques for the analysis of macroevolutionary patterns of morphological variation in the mandible of the
South American caviomorph rodents, which displays varying degrees of hystricognathy. The variation patterns were similar for 2D and 3D coordinate datasets. However, phylogenetic comparative statistical analyses showed
widely different results for mandible variation. Both the phylogenetic signal values and the results of phylogenetic regressions were markedly different between the two macroevolutionary mandible datasets. This suggests that
the inclusion of the third coordinate to characterize a hystricognathous mandible may lead to completely different interpretations concerning the processes that could be regulating the morphological diversification of the caviomorph mandible. We also compare these results with the 2D and 3D macroevolutionary patterns of variation in cranial shape and the intra-specific mandible variation. The variation patterns were similar for 2D and 3D coordinate for all these comparative datasets. The differing results
obtained at different evolutionary scales, give strength to the statement about careful selection of data not only in studies of morphological variation in caviomorphs but also for other groups of organisms."
In this study, we analysed locomotory habits in extant predators and Sparassodonta species throug... more In this study, we analysed locomotory habits in extant predators and Sparassodonta species through geometric morphometric techniques and discriminant analyses of the distal humerus in anterior view, proximal ulna in lateral view, and tibia in proximal view. We included a wide sample of extant predators, and considered the phylogenetic and allometric structure in the data sets. We also included some Sparassodonta, a group of carnivorous metatherians that inhabited South America during the Cenozoic, and inferred their locomotory habits. Results suggest the presence of a close relationship between shape and locomotory habits, even after removing the shape component explained by phylogeny in the three postcranial elements. Terrestrial habits were inferred for Arctodictis sinclairi, Borhyaena tuberata, ‘Lycopsis’ longirostrus, and Thylacosmilus atrox. Some degree of cursoriality was highlighted in B. tuberata and T. atrox, and climbing abilities in ‘L.’ longirostrus, and to a lesser degree in B. tuberata. Scansorial habits were inferred for Cladosictis patagonica, Sipalocyon gracilis, Prothylacynus patagonicus, and Pseudonotictis pusillus, and in the case of C. patagonica, some digging ability was also tentatively inferred.
Ontogenetic allometries of craniomandibular and dental features linked to digging were analyzed i... more Ontogenetic allometries of craniomandibular and dental features linked to digging were analyzed in 5 species of the South American subterranean rodent Ctenomys (tuco-tucos). With the exception of upper incisor procumbency, variables showed high correlation with overall skull size. In particular, craniomandibular variables related to the production of bite forces at the incisors showed near-geometric similarity during postnatal growth and interspecific changes in early developmental stages resulting in different starting forms (lateral transposition). Such an interspecific pattern of change is similar to one previously reported to occur among living and extinct ctenomyid genera. These results suggest more evolutionary flexibility for changes in early ontogenetic stages and allow rejection of the hypothesis that interspecific shape differences in the skull of Ctenomys would be associated with differences in size alone.
Caviomorphs are a clade of South American rodents recorded at least since the
early Oligocene (> ... more Caviomorphs are a clade of South American rodents recorded at least since the early Oligocene (> 31.5 Ma) that exhibit ample eco-morphological variation. It has been proposed that phylogenetic structure is more important than ecological factors for understanding mandibular shape variation in this clade. This was interpreted as a result of the long-standing evolutionary history of caviomorphs and the early divergence of major lineages. In this work, we test this hypothesis through the analysis of morphological variation in the mandible of living and extinct species and compare this information with that obtained through comparative phylogenetic analyses. Our results support the hypothesis of early origin of mandibular variation; moreover, they suggest the conservation of early differentiated morphologies, which could indicate the existence of constrained evolutionary diversification
We analyzed mandible shape variation of 17 genera belonging to three superfamilies (Cavioidea, Ch... more We analyzed mandible shape variation of 17 genera belonging to three superfamilies (Cavioidea, Chinchilloidea, and Octodontoidea) of South American caviomorph rodents using geometric morphometrics. The relative influence of phylogeny and ecology on this variation was assessed using phylogenetic comparative methods. Most morphological variation was concentrated in condylar, coronoid, and angular processes, as well as the diastema. Features potentially advantageous for digging (i.e. high coronoid and condylar processes, relatively short angular process, and diastema) were present only in octodontoids; cavioids showed opposing trends, which could represent a structural constraint for fossorial habits. Chinchilloids showed intermediate features. Genera were distributed in the morphospace according to their classification into superfamilial clades. The phylogenetic signal for shape components was significant along phylogeny, whereas the relationship between mandibular shape and ecology was nonsignificant when phylogenetic structure was taken into account. An early evolutionary divergence in the mandible shape among major caviomorph clades would explain the observed strong phylogenetic influence on the variation of this structure.
Uploads
Papers
the early Miocene in Patagonia (Argentina; Colhuehuapian
SALMA). Nearly complete cranial and mandibular remains
known for this genus provide a unique opportunity to explore
its paleobiology. For this, masticatory muscles were reconstructed
and craniomandibular shape variation assessed.
While such reconstruction indicates that most masticatory
muscles would have presented moderate development, both
the masseter lateralis and posterior muscles were poorly developed.
In contrast, we found that the temporalis muscle was
well developed, while conspicuous postorbital constriction,
postorbital processes, and superior temporal lines revealed a
substantial orbital portion of this muscle. According to geometric
morphometric results, craniomandibular shape was
interpreted as generalized. Features such as shortened palate,
narrower bizygomatic width, orthodont incisors, enlarged
incisive foramina, and a shallow jaw could be linked to
epigean habits. The moderate development of auditory bullae
in Prospaniomys suggests that it is unlikely that it may
have lived in extreme arid environments. Additionally,
based on its generalized dental morphology, an omnivorous or
generalized herbivorous diet that may have included leaves,
fruit, and potentially animal matter was inferred. By the early
Miocene, Patagonia experienced the initial expansion stage of
arid-adapted vegetation, with grasses present in low amounts
and abundant forests. Generalized habits and soft and nonabrasive
diet suggest that Prospaniomys was possibly associated
with more closed environments. Morphology alone cannot
be used as an environmental proxy, but it could undoubtedly
contribute to the interpretations based on data provided by
paleobotanical and geological frameworks in studies on the
evolution of environments.
diversification. In this work we examine the differences between the use of two- and three-dimensional morphometric techniques for the analysis of macroevolutionary patterns of morphological variation in the mandible of the
South American caviomorph rodents, which displays varying degrees of hystricognathy. The variation patterns were similar for 2D and 3D coordinate datasets. However, phylogenetic comparative statistical analyses showed
widely different results for mandible variation. Both the phylogenetic signal values and the results of phylogenetic regressions were markedly different between the two macroevolutionary mandible datasets. This suggests that
the inclusion of the third coordinate to characterize a hystricognathous mandible may lead to completely different interpretations concerning the processes that could be regulating the morphological diversification of the caviomorph mandible. We also compare these results with the 2D and 3D macroevolutionary patterns of variation in cranial shape and the intra-specific mandible variation. The variation patterns were similar for 2D and 3D coordinate for all these comparative datasets. The differing results
obtained at different evolutionary scales, give strength to the statement about careful selection of data not only in studies of morphological variation in caviomorphs but also for other groups of organisms."
morphometric techniques and discriminant analyses of the distal humerus in anterior view, proximal ulna in
lateral view, and tibia in proximal view. We included a wide sample of extant predators, and considered the
phylogenetic and allometric structure in the data sets. We also included some Sparassodonta, a group of
carnivorous metatherians that inhabited South America during the Cenozoic, and inferred their locomotory habits.
Results suggest the presence of a close relationship between shape and locomotory habits, even after removing the
shape component explained by phylogeny in the three postcranial elements. Terrestrial habits were inferred for
Arctodictis sinclairi, Borhyaena tuberata, ‘Lycopsis’ longirostrus, and Thylacosmilus atrox. Some degree of cursoriality
was highlighted in B. tuberata and T. atrox, and climbing abilities in ‘L.’ longirostrus, and to a lesser degree
in B. tuberata. Scansorial habits were inferred for Cladosictis patagonica, Sipalocyon gracilis, Prothylacynus
patagonicus, and Pseudonotictis pusillus, and in the case of C. patagonica, some digging ability was also tentatively
inferred.
early Oligocene (> 31.5 Ma) that exhibit ample eco-morphological variation.
It has been proposed that phylogenetic structure is more important than
ecological factors for understanding mandibular shape variation in this clade.
This was interpreted as a result of the long-standing evolutionary history of
caviomorphs and the early divergence of major lineages. In this work, we test
this hypothesis through the analysis of morphological variation in the
mandible of living and extinct species and compare this information with
that obtained through comparative phylogenetic analyses. Our results support
the hypothesis of early origin of mandibular variation; moreover, they suggest
the conservation of early differentiated morphologies, which could indicate
the existence of constrained evolutionary diversification
and Octodontoidea) of South American caviomorph rodents using geometric morphometrics. The relative influence
of phylogeny and ecology on this variation was assessed using phylogenetic comparative methods. Most morphological
variation was concentrated in condylar, coronoid, and angular processes, as well as the diastema. Features
potentially advantageous for digging (i.e. high coronoid and condylar processes, relatively short angular process,
and diastema) were present only in octodontoids; cavioids showed opposing trends, which could represent a
structural constraint for fossorial habits. Chinchilloids showed intermediate features. Genera were distributed in
the morphospace according to their classification into superfamilial clades. The phylogenetic signal for shape
components was significant along phylogeny, whereas the relationship between mandibular shape and ecology was
nonsignificant when phylogenetic structure was taken into account. An early evolutionary divergence in the
mandible shape among major caviomorph clades would explain the observed strong phylogenetic influence on the
variation of this structure.
the early Miocene in Patagonia (Argentina; Colhuehuapian
SALMA). Nearly complete cranial and mandibular remains
known for this genus provide a unique opportunity to explore
its paleobiology. For this, masticatory muscles were reconstructed
and craniomandibular shape variation assessed.
While such reconstruction indicates that most masticatory
muscles would have presented moderate development, both
the masseter lateralis and posterior muscles were poorly developed.
In contrast, we found that the temporalis muscle was
well developed, while conspicuous postorbital constriction,
postorbital processes, and superior temporal lines revealed a
substantial orbital portion of this muscle. According to geometric
morphometric results, craniomandibular shape was
interpreted as generalized. Features such as shortened palate,
narrower bizygomatic width, orthodont incisors, enlarged
incisive foramina, and a shallow jaw could be linked to
epigean habits. The moderate development of auditory bullae
in Prospaniomys suggests that it is unlikely that it may
have lived in extreme arid environments. Additionally,
based on its generalized dental morphology, an omnivorous or
generalized herbivorous diet that may have included leaves,
fruit, and potentially animal matter was inferred. By the early
Miocene, Patagonia experienced the initial expansion stage of
arid-adapted vegetation, with grasses present in low amounts
and abundant forests. Generalized habits and soft and nonabrasive
diet suggest that Prospaniomys was possibly associated
with more closed environments. Morphology alone cannot
be used as an environmental proxy, but it could undoubtedly
contribute to the interpretations based on data provided by
paleobotanical and geological frameworks in studies on the
evolution of environments.
diversification. In this work we examine the differences between the use of two- and three-dimensional morphometric techniques for the analysis of macroevolutionary patterns of morphological variation in the mandible of the
South American caviomorph rodents, which displays varying degrees of hystricognathy. The variation patterns were similar for 2D and 3D coordinate datasets. However, phylogenetic comparative statistical analyses showed
widely different results for mandible variation. Both the phylogenetic signal values and the results of phylogenetic regressions were markedly different between the two macroevolutionary mandible datasets. This suggests that
the inclusion of the third coordinate to characterize a hystricognathous mandible may lead to completely different interpretations concerning the processes that could be regulating the morphological diversification of the caviomorph mandible. We also compare these results with the 2D and 3D macroevolutionary patterns of variation in cranial shape and the intra-specific mandible variation. The variation patterns were similar for 2D and 3D coordinate for all these comparative datasets. The differing results
obtained at different evolutionary scales, give strength to the statement about careful selection of data not only in studies of morphological variation in caviomorphs but also for other groups of organisms."
morphometric techniques and discriminant analyses of the distal humerus in anterior view, proximal ulna in
lateral view, and tibia in proximal view. We included a wide sample of extant predators, and considered the
phylogenetic and allometric structure in the data sets. We also included some Sparassodonta, a group of
carnivorous metatherians that inhabited South America during the Cenozoic, and inferred their locomotory habits.
Results suggest the presence of a close relationship between shape and locomotory habits, even after removing the
shape component explained by phylogeny in the three postcranial elements. Terrestrial habits were inferred for
Arctodictis sinclairi, Borhyaena tuberata, ‘Lycopsis’ longirostrus, and Thylacosmilus atrox. Some degree of cursoriality
was highlighted in B. tuberata and T. atrox, and climbing abilities in ‘L.’ longirostrus, and to a lesser degree
in B. tuberata. Scansorial habits were inferred for Cladosictis patagonica, Sipalocyon gracilis, Prothylacynus
patagonicus, and Pseudonotictis pusillus, and in the case of C. patagonica, some digging ability was also tentatively
inferred.
early Oligocene (> 31.5 Ma) that exhibit ample eco-morphological variation.
It has been proposed that phylogenetic structure is more important than
ecological factors for understanding mandibular shape variation in this clade.
This was interpreted as a result of the long-standing evolutionary history of
caviomorphs and the early divergence of major lineages. In this work, we test
this hypothesis through the analysis of morphological variation in the
mandible of living and extinct species and compare this information with
that obtained through comparative phylogenetic analyses. Our results support
the hypothesis of early origin of mandibular variation; moreover, they suggest
the conservation of early differentiated morphologies, which could indicate
the existence of constrained evolutionary diversification
and Octodontoidea) of South American caviomorph rodents using geometric morphometrics. The relative influence
of phylogeny and ecology on this variation was assessed using phylogenetic comparative methods. Most morphological
variation was concentrated in condylar, coronoid, and angular processes, as well as the diastema. Features
potentially advantageous for digging (i.e. high coronoid and condylar processes, relatively short angular process,
and diastema) were present only in octodontoids; cavioids showed opposing trends, which could represent a
structural constraint for fossorial habits. Chinchilloids showed intermediate features. Genera were distributed in
the morphospace according to their classification into superfamilial clades. The phylogenetic signal for shape
components was significant along phylogeny, whereas the relationship between mandibular shape and ecology was
nonsignificant when phylogenetic structure was taken into account. An early evolutionary divergence in the
mandible shape among major caviomorph clades would explain the observed strong phylogenetic influence on the
variation of this structure.