AN EVOLUTIONARY ANALYSIS OF THE STYLOID PROCESS: TRANSFORMATIONAL HISTORY OF THE DORSALMOST DERIVATIVES OF THE HYOID ARCH.
Item
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Title
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AN EVOLUTIONARY ANALYSIS OF THE STYLOID PROCESS: TRANSFORMATIONAL HISTORY OF THE DORSALMOST DERIVATIVES OF THE HYOID ARCH.
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Identifier
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AAI8401891
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identifier
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8401891
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Creator
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CAMBAS, CAROL ANN.
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Contributor
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Dr. Frederick Szalay
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Date
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1983
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Language
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English
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Publisher
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City University of New York.
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Subject
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Anthropology, Physical
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Abstract
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An evolutionary analysis of the styloid process was undertaken because its presence or absence in various mammalian orders, including primates, has not been studied systematically, its morphological homologues in other gnathostomes are not known, and it seems to have a potentially significant functional articulation with the otic capsule (petrosal).;This study demonstrates that the process, or its cartilaginous homologue, is present on all primate basicrania and always articulates with the petrosal. It is the dorsalmost part of the mammalian hyoid apparatus and articulates with the ear in all mammals examined.;Because it is a hyoid arch derivative, its homologues were tested in other gnathostomes. It is concluded that the rhipidistian hyomandibula and lower tetrapod columella are not the homologues of the mammalian stapes alone, as widely believed, but rather the stapes and styloid process.;A functional hypothesis suggests that dorsalmost derivatives of the hyoid arch (DDHA) together with first arch derivatives are a form-function complex in all gnathostomes, with a mechanical function of facultative vibration and a possible biological role of transferring mechanical energy to the ear.;The inner ear is an energy transducer. In fish and lower tetrapods, mechanical energy in the form of forced vibrations applied to the jaws during feeding are transferred to the chondrocranium and/or otic capsule by the processes of this complex. Derived terrestrial tetrapods evolve adaptations for more efficient transfer of different types of mechanical energy (i.e., airborne sounds), but use the same morphological system. Morphological changes are considered in terms of how they would affect acoustical impedance.;In non-mammalian tetrapods, internally generated forced vibrations and externally generated airborne sounds are both transferred by a single element, the columella. In mammals, the DDHA produces two elements: the stapes and styloid process. The former transfers mainly airborne acoustical energy. The latter secondarily attaches the hyoid apparatus directly to the otic capsule and creates a separate pathway for internally generated sounds from the tongue and larynx. In this way, efficient perception of externally generated sounds is not interfered with by internally generated bone-conducted sound.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Anthropology
