Evolutionary Principles of the Mammalian Middle Ear

Fleischer, Gerald

doi:10.1007/978-3-642-67143-2

Cited by 174 publications

(310 citation statements)

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“…During and after this time, the middle ear slowly evolved towards lighter, more freely suspended ossicles, but not uniformly. Two types of eutherian middle ear, with many intermediates, have been recognized (Fleischer 1978;Lavender et al 2011), a "microtype" in small mammals and a "freely mobile" type in medium to large mammals. Ossicular rotational axes differ between species (Puria and Steele 2010) and scaling with animal size is a general, but not universal, principle (Hemilä et al 1995).…”

Section: A Decisive and Unique Step In Evolution: The Integration Of mentioning

confidence: 99%

Evolutionary Paths to Mammalian Cochleae

Manley

2012

JARO

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Evolution of the cochlea and high-frequency hearing (920 kHz; ultrasonic to humans) in mammals has been a subject of research for many years. Recent advances in paleontological techniques, especially the use of micro-CT scans, now provide important new insights that are here reviewed. True mammals arose more than 200 million years (Ma) ago. Of these, three lineages survived into recent geological times. These animals uniquely developed three middle ear ossicles, but these ossicles were not initially freely suspended as in modern mammals. The earliest mammalian cochleae were only about 2 mm long and contained a lagena macula. In the multituberculate and monotreme mammalian lineages, the cochlea remained relatively short and did not coil, even in modern representatives. In the lineage leading to modern therians (placental and marsupial mammals), cochlear coiling did develop, but only after a period of at least 60 Ma. Even Late Jurassic mammals show only a 270°cochlear coil and a cochlear canal length of merely 3 mm. Comparisons of modern organisms, mammalian ancestors, and the state of the middle ear strongly suggest that high-frequency hearing (920 kHz) was not realized until the early Cretaceous (~125 Ma). At that time, therian mammals arose and possessed a fully coiled cochlea. The evolution of modern features of the middle ear and cochlea in the many later lineages of therians was, however, a mosaic and different features arose at different times. In parallel with cochlear structural evolution, prestins in therian mammals evolved into effective components of a new motor system. Ultrasonic hearing developed quite late-the earliest bat cochleae (~60 Ma) did not show features characteristic of those of modern bats that are sensitive to high ultrasonic frequencies.

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Section: A Decisive and Unique Step In Evolution: The Integration Of mentioning

confidence: 99%

Evolutionary Paths to Mammalian Cochleae

Manley

2012

JARO

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“…Purves and Pilleri, 1983) and only loosely connected to it via ligaments to the mastoid process (Pilleri et al, 1987). The detachment allows separate reception of sound and isolated vibrations of the ear bones (Miller, 1923;Fleischer, 1978;Pilleri et al, 1987). The anatomy of the cetacean organ of hearing is well described (Pilleri et al, 1987) but was usually studied by producing serial sections by grinding the petrosals (e.g.…”

Section: Fossil Ear Bonesmentioning

confidence: 99%

Three-dimensional Magnetic Resonance Imaging of fossils across taxa

Mietchen

Aberhan²,

Manz

et al. 2008

Biogeosciences

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Abstract. The frequency of life forms in the fossil record is largely determined by the extent to which they were mineralised at the time of their death. In addition to mineral structures, many fossils nonetheless contain detectable amounts of residual water or organic molecules, the analysis of which has become an integral part of current palaeontological research. The methods available for this sort of investigations, though, typically require dissolution or ionisation of the fossil sample or parts thereof, which is an issue with rare taxa and outstanding materials like pathological or type specimens. In such cases, non-destructive techniques could provide a valuable methodological alternative. While Computed Tomography has long been used to study palaeontological specimens, a number of complementary approaches have recently gained ground. These include Magnetic Resonance Imaging (MRI) which had previously been employed to obtain three-dimensional images of pathological belemnites non-invasively on the basis of intrinsic contrast. The present study was undertaken to investigate whether 1 H MRI can likewise provide anatomical information about nonpathological belemnites and specimens of other fossil taxa. To this end, three-dimensional MR image series were acquired from intact non-pathological invertebrate, vertebrate and plant fossils. At routine voxel resolutions in the range of several dozens to some hundreds of micrometers, these images reveal a host of anatomical details and thus highlight the potential of MR techniques to effectively complement existing methodological approaches for palaeontological investigations in a wide range of taxa. As for the origin of the MR signal, relaxation and diffusion measurements as well as 1 H and 13 C MR spectra acquired from a belemnite suggest intracrystalline water or hydroxyl groups, rather than organic residues.

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“…The likely position of the axis of rotation is shown in Figure 9 where no improvement in the lever ratio is evident. On the contrary, the studies of Fleischer [50] indicate that the center of mass is moving towards the axis of rotation, which would minimize the inertial forces generated during vibration rather than cause any increase in the lever ratio effect. Therefore the idea that the middle-ear is evolving to a more optimal lever is not supported by phyletic analyses.…”

Section: Evolution Of the Middle Ear And The Possibility Of An Optimummentioning

confidence: 99%

“…Fleischer [50] proposed that the middle-ear in all extant mammals evolved from an 'ancestral case' where the malleus was U-shaped with one arm connected to the circumference of the tympanic membrane, followed by an intermediate case where the one arm of the U-shaped malleus became a ligament, to the present case where is has almost disappeared to form the anterior mallear ligament. Concomitant with these adaptations, the axis of rotation of the ossicles changed.…”

Section: Evolution Of the Middle Ear And The Possibility Of An Optimummentioning

confidence: 99%

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Prendergast

2002

Meccanica

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Abstract. The musculo-skeletal system serves the mechanical function of creating motion and transmitting loads. It is made up mainly of four components: bone, cartilage, muscle and fibrous connective tissue. These have evolved over millions of years into the complex and diverse shapes of the animal skeleton. The skeleton, however, is not built to a static plan: it can adapt to mechanical forces during growth, it can remodel if the forces change, and it can regenerate if it is damaged. In this paper, the regulation of skeletal construction by mechanical forces is analyzed from both ontogenetic and phylogenetic standpoints. In the first part, models of biomechanical processes that act during skeletal ontogenesis -tissue differentiation and bone remodeling -are presented and, in the second, the evolution of the middle ear is used as an example of biomechanical change in skeletal phylogenesis. Because the constitutive laws for skeletal tissues are relatively well understood, and because the skeleton is preserved in the fossil record, application of mechanics to skeletal evolution seems to present a good opportunity to explore the relationships governing ontogenetic adaptations and phylogenetic change.

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Evolutionary Principles of the Mammalian Middle Ear

Cited by 174 publications

References 0 publications

Evolutionary Paths to Mammalian Cochleae

Evolutionary Paths to Mammalian Cochleae

Three-dimensional Magnetic Resonance Imaging of fossils across taxa

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