The Hypertrophy of the Tympanic Bulla in Three Species of Dasypodids (Mammalia, Xenarthra) from Argentina

Squarcia, Silvia M; Sidorkewicj, Nora Silvia; Casanave, Emma Beatriz

doi:10.4067/s0717-95022007000300021

Cited by 15 publications

(9 citation statements)

References 30 publications

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“…Most of the bigger genera (e.g., Hydrochoerus , Lagostomus , or Myocastor ) live in open areas and display caudally displaced orbits, a relatively longer snout, longer tooth rows, and a narrow basicranium; whereas the medium‐sized rodents sharing the same type of habitat are characterized by well‐developed tympanic bullae and a wide basicranium. Enlarged tympanic bullae allow the rodent to detect a predator by increasing the amplification of sounds (Squarcia et al,2007). To some extent, selective pressures should act differently on the evolution of sensory systems of bigger rodents like capybaras, notably because they interact with types of predators other than the common birds of prey.…”

Section: Discussionmentioning

confidence: 99%

Patterns of covariation in the masticatory apparatus of hystricognathous rodents: Implications for evolution and diversification

Hautier¹,

Lebrun²,

Cox³

2012

Journal of Morphology

103

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The mammalian masticatory apparatus is a highly plastic region of the skull. In this study, a quantification of shape variation, the separation of phylogeny from ecology in the genesis of shape brings new insights on the relationships between morphological changes in the cranium, mandible, and muscle architecture. Our study focuses on the Ctenohystrica, a clade that is remarkably diverse and exemplifies a rich evolutionary history in the Old and New World. Current and past rodent diversity brings out the limitations of the qualitative descriptive approach and highlights the need for using integrative quantitative methods. We present here the first descriptive comparison of the whole masticatory apparatus within the Ctenohystrica, by combining geometric morphometric approaches with a noninvasive method of dissection in 3D, iodine-enhanced microcomputed tomography. We used these methods to explore the patterns of covariation between the cranium and the mandible, and the interspecific morphological variation of the skull with regard to several factors such as phylogeny, activity period, type of habitat, and diet. Our study revealed strong phylogenetic and ecological imprints on the morphological traits associated with masticatory mechanics. We showed that, despite a high diversification of lineages, the evolutionary history of Ctenohystrica comprises only a small number of morphotypes for the skull and mandible. The position of the eye was suggested as a key factor determining morphological evolution of the masticatory apparatus by limiting the number of possible pathways and promoting convergent evolution toward new habitats and diets between different clades.

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Section: Discussionmentioning

confidence: 99%

Patterns of covariation in the masticatory apparatus of hystricognathous rodents: Implications for evolution and diversification

Hautier¹,

Lebrun²,

Cox³

2012

Journal of Morphology

103

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“…Although many studies are available on the hearing adaptations in large and small burrowing mammals (Nevo;Burda et al, 1992;Mason, 2001;Schleich & Vassallo;Lange et al, 2004), the reports on dasypodids are less abundant. Some of the contributions on the morphology of the ear region in these animals come from Segall (1976), Patterson et al (1989Patterson et al ( , 1992, Gaudin et al, Wible & Gaudin (2004), Squarcia et al (2007) and Wible (2010).…”

Section: Introductionmentioning

confidence: 99%

Morphology of the Middle Ear in Three Species of Armadillos (Dasypodidae, Xenarthra) from Argentina

Sidorkewicj

Casanave

2012

Int. J. Morphol.

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. Morphology of the middle ear in three species of armadillos (Dasypodidae, Xenarthra) from Argentina. Int. J. Morphol., 30(4):1500-1507, 2012. SUMMARY:Middle ears of adult Chaetophractus villosus, C. vellerosus and Zaedyus pichiy were studied for qualitative and quantitative comparisons. A great similarity in the overall shape of the middle ear structures was observed in the three species. The well-developed auditory bulla was formed by the intimate fusion of the tympanic and entotympanic. Internally, a recessus meatus and a wide epitympanic recess extending dorsally into an epitympanic sinus were recognized. The petrosal promontorium, nearly triangular, was the most salient feature in the tympanic cavity. The auditory ossicles corresponded to the transitional middle ear type. The m. tensor tympani and the m. stapedius were conspicuous. The lack of a stapedial artery was confirmed in all cases. The tympanic area and middle ear ossicles were relatively larger in C. vellerosus than in the other two species. It is hoped that the results of the present paper coupled to the bullar hypertrophy found in a previous work will provide a significant basis for future functional studies on the hearing capabilities in the dasypodids.

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“…Petter () measured bullar length in gerbils and presented this as a percentage of skull length, in order to compare relative sizes between species. In their studies on armadillos, Roig () and Squarcia et al () referred to this percentage value as the ‘bullar hypertrophy index’ (BHI). Roig established three well‐defined groups based on BHI, and related the degree of hypertrophy of the species with the aridity of the environment they inhabit.…”

Section: Discussionmentioning

confidence: 99%

The middle ear of the pink fairy armadillo Chlamyphorus truncatus (Xenarthra, Cingulata, Chlamyphoridae): comparison with armadillo relatives using computed tomography

et al. 2020

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The pink fairy armadillo Chlamyphorus truncatus is the smallest extant armadillo and one of the least-known fossorial mammals. The aim of this study was to establish if its middle ear is specially adapted to the subterranean environment, through comparison with more epigeic relatives of the groups Euphractinae (Chaetophractus villosus, Chaetophractus vellerosus, Zaedyus pichiy) and Dasypodinae (Dasypus hybridus). We examined the middle ears using micro-computed tomography and subsequent three-dimensional reconstructions. D. hybridus has a relatively small middle ear cavity, an incomplete bulla and 'ancestral' ossicular morphology. The other species, including Chlamyphorus, have fully ossified bullae and middle ear ossicles, with a morphology between 'transitional' and 'freely mobile', but in all armadillos the malleus retains a long anterior process. Unusual features of armadillo ears include the lack of a pedicellate lenticular apophysis and the presence, in some species, of an element of Paaw within the stapedius muscle. In common with many subterranean mammals, Chlamyphorus has a relatively flattened malleo-incudal articulation and appears to lack a functional tensor tympani muscle. Its middle ear cavity is not unusually enlarged, and its middle ear ossicles seem less robust than those of the other armadillos studied. In comparison with the euphractines, there is no reason to believe that the middle ear of this species is specially adapted to the subterranean environment; some aspects may even be indicative of degeneration. The screaming hairy armadillo, Chaetophractus vellerosus, has the most voluminous middle ear in both relative and absolute terms. Its hypertrophied middle ear cavity likely represents an adaptation to low-frequency hearing in arid rather than subterranean conditions.

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The Hypertrophy of the Tympanic Bulla in Three Species of Dasypodids (Mammalia, Xenarthra) from Argentina

Cited by 15 publications

References 30 publications

Patterns of covariation in the masticatory apparatus of hystricognathous rodents: Implications for evolution and diversification

Patterns of covariation in the masticatory apparatus of hystricognathous rodents: Implications for evolution and diversification

Morphology of the Middle Ear in Three Species of Armadillos (Dasypodidae, Xenarthra) from Argentina

The middle ear of the pink fairy armadillo Chlamyphorus truncatus (Xenarthra, Cingulata, Chlamyphoridae): comparison with armadillo relatives using computed tomography

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