Scaling and adaptations of incisors and cheek teeth in caviomorph rodents (Rodentia, Hystricognathi)

Becerra, Federico; Vassallo, Aldo Iván; Echeverría, Alejandra Isabel; Casinos, Adriá

doi:10.1002/jmor.20051

Cited by 33 publications

(35 citation statements)

References 59 publications

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“…The mandibular apparatus of rodents, which is adapted to process hard food items, is particularly capable of producing strong bite forces (Van Daele et al, 2009;Becerra et al, 2012;Vassallo and Antenucci, 2015). Therefore, it must be able to withstand large reaction forces received on incisors, molars, and jaw condyle.…”

Section: Discussionmentioning

confidence: 98%

Analysis of arch‐like bones: The rodent mandible as a case study

Vassallo¹

2016

Journal of Morphology

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Bone strength is determined by the mechanical properties of bone material, and the size and shape of the whole bone, i.e., its architecture. The mandible of vertebrates has been traditionally regarded as a beam oriented in relation to main masticatory loads, i.e., the longer dimension of its cross-section being parallel to the load. Rodents follow this pattern but, in addition, their mandible possesses an intriguing arch-like shape that is apparent when seen in the lateral view. Little attention was given to the structural capacity of this trait. The advantage of an arch is that it can withstand a greater load than a horizontal beam. The objective of this study was to model the rodent mandible like an arch to evaluate its structural strength. The bending moment in an arch-like mandible was 15-25% lower with respect to a beam-like mandible. Further, bending varies with mandible "slenderness" and incisor procumbency, a functionally relevant rodent trait. In the rodent Ctenomys talarum (Caviomorpha; Ctenomyidae), bone stress was substantially reduced when the mandible was modeled as an arch-like structure as compared with a beam-like structure, and safety factors were 15-34% higher. The shape of rodents' mandible might confer a functional advantage to high and repeatedly applied loads resulting from a unique feeding mode: gnawing. J. Morphol. 277:879-887, 2016. © 2016 Wiley Periodicals, Inc.

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Section: Discussionmentioning

confidence: 98%

Analysis of arch‐like bones: The rodent mandible as a case study

Vassallo¹

2016

Journal of Morphology

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“…In the calculation of ( I ) we used external measurements because the incisor part that is under bending stress is solid. The 2nd moment of area of the incisors about the sagittal (anterior–posterior) axis was calculated as:

I = \frac{π}{4 [(W_{i} / 2) {(D_{i} / 2)}^{3}]}

considering incisor cross section as an ellipse with major axis ( W i ) represented by the transverse diameter of the incisor, and minor axis ( D i ) represented by its antero‐posterior diameter (Verzi et al, ; Becerra et al, ). These variables were taken at the incisor's tip just behind the chisel.…”

Section: Methodsmentioning

confidence: 99%

Biting Performance and Skull Biomechanics of a Chisel Tooth Digging Rodent (Ctenomys tuconax; Caviomorpha; Octodontoidea)

2012

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Biting performance is a key factor in vertebrate groups possessing particular food habits. In subterranean rodents that use the incisors as a digging tool, apart from requirements related to gnawing abrasive diets, the force exerted at the incisors tips must be sufficient to break down soils that are often exceedingly compact. The subterranean genus Ctenomys diversified in the southern portion of South America closely associated with the relatively open environments that characterize that region. This genus is considered a "claw and chisel tooth digger," that is, during the excavation of their galleries, the animals break down the soil with both the fore-claws and the incisors. We report here measurements of in vivo bite force in one of the largest species of the genus, C. tuconax, which occupies highland grasslands with compacted soils. We document the combined use of claws and incisors observed under field conditions, also providing measurements of soil compaction in the habitat occupied by this species. We report estimates of bite force at the level of the incisors and cheek teeth calculated from the physiological cross-sectional area of jaw muscles. To this aim, anatomical and biomechanical analyses of the mandibular apparatus were performed in preserved specimens. We found that C. tuconax bites with a higher force than expected for a mammal of its size. To assess anatomical correlates of biting performance, the morphology of the skull and jaw, and incisor second moment of area were compared with those of other caviomorph rodents with different lifestyle.

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“…In addition, among fossorial rodents two burrow strategies have been developed: with the incisors (chisel-tooth digging) or with the forelimbs (scratch-digging), while they can use both types or only one of them. The cranio-dental morphology of Tympanoctomys is not similar to that of those corresponding to chisel-tooth digging as the case of Spalacopus , subterranean octodontid (Vassallo and Verzi 2001; Bacigalupe et al 2002; Verzi 2002; Olivares et al 2004; Lessa et al 2008; Becerra et al 2012). Based on this idea, some authors have analyzed skeletal features in few related genera and members of the family, but including only one species of Tympanoctomys ( T. barrerae ), proposing novel functional inferences (Morgan and Verzi 2006; Lessa et al 2008; Morgan 2009; Morgan and Verzi 2011; Morgan and Alvarez 2013).…”

Section: Introductionmentioning

confidence: 95%

Morphology of the limbs in the semi-fossorial desert rodent species of Tympanoctomys (Octodontidae, Rodentia)

Perez¹,

Bárquez²,

Díaz³

2017

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Here, a detailed description of the forelimbs and hindlimbs of all living species of the genus Tympanoctomys are presented. These rodents, highly adapted to desert environments, are semi-fossorial with capacity to move on the surface as well as to build burrows. The shape, structure, and size of the limbs are described. Contrary to what was expected for scratch digging semi-fossorial species, Tympanoctomys have slender humerus, radius and ulna; with narrow epicondyles of the humerus and short olecranon of the ulna with poorly developed processes. Following our descriptions, no intrageneric morphological variation regarding to the configuration of the limbs was detected, probably due to phylogenetic proximity, and not related to specific variations in response to different use of substrates or habits. The obtained results constitute a source of previously unpublished information as well as an important base for future analysis in different studies, such as morphometric, morpho-functional, or phylogenetic researches.

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Scaling and adaptations of incisors and cheek teeth in caviomorph rodents (Rodentia, Hystricognathi)

Cited by 33 publications

References 59 publications

Analysis of arch‐like bones: The rodent mandible as a case study

Analysis of arch‐like bones: The rodent mandible as a case study

Biting Performance and Skull Biomechanics of a Chisel Tooth Digging Rodent (Ctenomys tuconax; Caviomorpha; Octodontoidea)

Morphology of the limbs in the semi-fossorial desert rodent species of Tympanoctomys (Octodontidae, Rodentia)

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