Project 833: E. G. Ekdale. 2013. Comparative Anatomy of the Bony Labyrinth (Inner Ear) of Placental Mammals. PLOS ONE. 8 (6):e66624.
Specimen: Dasypus novemcinctus (TMM/M:1885)

Abstract

Background

Variation is a naturally occurring phenomenon that is observable at all levels of morphology, from anatomical variations of DNA molecules to gross variations between whole organisms. The structure of the otic region is no exception. The present paper documents the broad morphological diversity exhibited by the inner ear region of placental mammals using digital endocasts constructed from high-resolution X-ray computed tomography (CT). Descriptions cover the major placental clades, and linear, angular, and volumetric dimensions are reported.

Principal Findings

The size of the labyrinth is correlated to the overall body mass of individuals, such that large bodied mammals have absolutely larger labyrinths. The ratio between the average arc radius of curvature of the three semicircular canals and body mass of aquatic species is substantially lower than the ratios of related terrestrial taxa, and the volume percentage of the vestibular apparatus of aquatic mammals tends to be less than that calculated for terrestrial species. Aspects of the bony labyrinth are phylogenetically informative, including vestibular reduction in Cetacea, a tall cochlear spiral in caviomorph rodents, a low position of the plane of the lateral semicircular canal compared to the posterior canal in Cetacea and Carnivora, and a low cochlear aspect ratio in Primatomorpha.

Significance

The morphological descriptions that are presented add a broad baseline of anatomy of the inner ear across many placental mammal clades, for many of which the structure of the bony labyrinth is largely unknown. The data included here complement the growing body of literature on the physiological and phylogenetic significance of bony labyrinth structures in mammals, and they serve as a source of data for future studies on the evolution and function of the vertebrate ear.



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Project DOI: 10.7934/P833, http://dx.doi.org/10.7934/P833
This project containsMatrices
  • 214 Media
  • 1 Matrix
  • 2 Documents
  • 36 Taxa
  • 37 Specimens
  • 6 Characters
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Total scored cells: 216
Total media associated with cells: 291
Total labels associated with cell media: 219
Characters
Total characters: 6
Total characters with associated media: 0
Total characters with media with labels: 0
Total character states: 16
Total character states with associated media: 16
Total character states with media with labels:14
Total unordered/ordered characters:6/0
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    Eric Ekdale
    Project Administrator
    Last logged in 06/23/13
    36372142086061610216
    (216, 0, 0)
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    Taxonomic Overview for Matrix 'M1905' (36 Taxa)

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    [1] Didelphis virginiana
    Last Modified in 12/05/13
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    [2] † Kulbeckia kulbecke
    Last Modified in 12/05/13
    06000861
    [3] † Ukhaatherium nessovi
    Last Modified in 12/05/13
    06000861
    [4] † Zalambdalestes lechei
    Last Modified in 12/05/13
    06000861
    [5] † Zhelestid
    Last Modified in 12/05/13
    06000861
    [6] Chrysochloris sp.
    Last Modified in 12/05/13
    06000861
    [7] † Elephantimorpha
    Last Modified in 12/05/13
    06000861
    [8] Hemicentetes semispinosum
    Last Modified in 12/05/13
    06000861
    [9] Macroscelides proboscideus
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    [10] Orycteropus afer
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    06000861
    [11] Procavia capensis
    Last Modified in 12/05/13
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    [12] Trichechus manatus
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    [13] Dasypus novemcinctus
    Last Modified in 12/05/13
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    [14] Atelerix albiventris
    Last Modified in 12/05/13
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    [15] † Balaenopteridae
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    06000971
    [16] † Bathygenys reevesi
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    [17] Canis familiaris
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    [18] Equus caballus
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    [19] Eumetopias jubatus
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    [20] Felis catus
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    [21] Manis tricuspis
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    [22] Nycteris grandis
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    [23] Pteropus lylei
    Last Modified in 12/05/13
    06000861
    [24] Rhinolophus ferrumequinum
    Last Modified in 12/05/13
    06000861
    [25] Sorex monticolus
    Last Modified in 12/05/13
    06000971
    [26] Sus scrofa
    Last Modified in 12/05/13
    06000861
    [27] Tadarida brasiliensis
    Last Modified in 12/05/13
    06000861
    [28] Tursiops truncatus
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    [29] Cavia porcellus
    Last Modified in 12/05/13
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    [30] Cynocephalus volans
    Last Modified in 12/05/13
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    [31] Homo sapiens
    Last Modified in 12/05/13
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    [32] Lepus californicus
    Last Modified in 12/05/13
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    [33] Macaca mulatta
    Last Modified in 12/05/13
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    [34] Mus musculus
    Last Modified in 12/05/13
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    [35] Sylvilagus floridanus
    Last Modified in 12/05/13
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    [36] Tupaia glis
    Last Modified in 12/05/13
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