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  • 1
    Electronic Resource
    Electronic Resource
    Structural correlates of function in the “opercularis” muscle of amphibians (1977)
    Springer
    Cell & tissue research 175 (1977), S. 499-522 
    Details
    ISSN: 1432-0878
    Keywords: Muscle ; Audition ; Ultrastructure ; Amphibian ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This study characterizes the fine structure of the “opercularis” muscles of selected frogs and salamanders (Genera: Hyla; Desmognathus; Ambystoma). The “opercularis” muscle originates on the shoulder girdle and inserts on the opercular plate in the fenestra ovalis of the otic capsule. Each of the three genera used exhibits one of the major gross dispositions of this muscle found in amphibians. In each case the “opercularis” muscle contains large numbers of tonic fibers: 80% in Hyla; 90% in Desmognathus; 45% in Ambystoma. These fibers correspond to the class-5 tonic fibers of Smith and Ovalle (1973). The remainder of the fibers in the “opercularis” correspond to those in the class-3 “phasic” of Smith and Ovalle. The muscle from which the “opercularis” is derived (levator scapulae in Hyla, cucullaris in Desmognathus) is comprised of fibers which correspond to the class-2 phasic fibers of Smith and Ovalle. The fiber composition of the “opercularis” indicates that it is constructed to sustain contraction over long periods of time. This composition is supportive of the functional role in audition proposed for the muscle by Lombard and Straughan (1974). Evidence is presented that indicates that fiber size may be body size dependent and thus is an inappropriate criterion of fiber type identification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222415
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative morphology of the amphibian opercularis system: I. General design features and functional interpretation (1986)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 190 (1986), S. 43-61 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the opercularis system of anuran and caudate amphibians suggests that it acts to produce motion of the operculum that in turn produces fluid motion within the inner ear. The operculum and opercularis muscle form a lever system, with a narrow connection between the operculum and otic capsule acting as a fulcrum about which the operculum moves in response to forces applied via the muscle. The opercula of many species possess a muscular process on which the muscle inserts, thereby increasing the moment arm through which the muscle acts. The tonicity of the opercularis muscle allows tensile forces produced by substrate vibration or other mechanical energy applied to the forelimb to be effectively transmitted to the operculum; the elasticity of the connective tissue holding the operculum in place should act to return the operculum to its original position. The opercularis systems of frogs and non-plethodontid salamanders are similar structurally and functionally; that of plethodontid salamanders is structurally distinct but also functions as a lever system. Fluid motion produced by opercular motion could stimulate various end organs of the inner ear; the saccule, lagena, and amphibian papilla are in close approximation and wave energy could directly affect their otoconial or tectorial structures. In those anurans with a tympanic ear, the stapedial footplate and operculum articulate, but this articulation allows both to move independently. The stapes-tympanum complex and opercularis system therefore appear to be independent functional systems, and it is unlikely that the opercularis system modulates middle ear responsiveness. The general design of the opercularis system is consistent with a function in reception of substrate vibrations.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051900105
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  • 3
    Electronic Resource
    Electronic Resource
    Tongue evolution in the lungless salamanders, family plethodontidae I. Introduction, theory and a general model of dynamics (1976)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 148 (1976), S. 265-286 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Plethodontid salamanders capture prey by projecting the tongue from the mouth. An analysis of theoretical mechanics of the hyobranchial skeleton is used to formulate a working hypothesis of tongue movements. Predictions that the skeletal elements of the tongue are included in the projectile and that the hyobranchial skeleton is folded during projection are central to the analysis, When decapitated in a particular way, salamanders project the tongue, and it is not retracted. When these heads are fixed and sectioned, examination confirms the predictions, In turn, these observations are used to refine the working hypothesis and to generate a general model of tongue dynamics for plethodontids. Muscles performing the major roles of projection (subarcualis rectus I) and retraction (rectus cervicis profundus) are identified. The skeleton is folded passively along a morphological track having the form of a tractrix, Predictions concerning the shape of the track and the exact configuration of the folded skeleton are confirmed by study of sectioned material. The skeleton unfolds along the track during retraction and is spread into the resting state, The model developed herein will be used as a basis for predictions concerning selection patterns in the family and for analytical purposes in comparative and evolutionary studies.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051480302
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  • 4
    Electronic Resource
    Electronic Resource
    Electromyography of the opercularis muscle of Rana catesbeiana: An amphibian tonic muscle (1983)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 175 (1983), S. 17-26 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The opercularis muscle of Rana catesbeiana originates on the suprascapular cartilage of the shoulder girdle and inserts on the otic opercular element. It is part of the levator scapulae musculature and lies dorsomedial to the levator scapulae superior and inferior muscles. Bipolar electrode recordings from all three muscles show electrical activity linked to cyclical firing of the posterior intermandibularis muscle, an important ventilatory muscle. The opercularis muscle shows low amplitude, erratic signals when animals are sumerged. Upon emergence of the snout region, the opercularis muscle shows rhythmic low amplitude activity at twice the rate of buccal pumping. Lung ventilation is synchronized with this rhythm and at ventilation the opercularis muscle shows higher amplitude activity. Upon submergence, opercularis activity again shows low level activity with no rhythmic pattern. Opercularis muscle activity has a major low frequency component (about 30 Hz) that probably corresponds to activity of tonic muscle fibers. Higher frequency signals (about 200-250 Hz) comparable to those of the levator scapulae muscles are also present and probably represent activity of phasic muscle fibers. Activity of the opercularis muscle is correlated with conditions in which aerial respiration is possible, and this pattern of activity supports an opercularis role in aerial hearing and/or detection of substrate vibrations. As far as we know, this is the first report of electromyographic analysis of a vertebrate tonic muscle.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051750103
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  • 5
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    Palate and braincase of Whatcheeria deltae Lombard & Bolt, 1995 (2018)
    Cambridge University Press
    Details
    Publication Date: 2018
    Description: 〈div data-abstract-type="normal"〉〈p〉The reconstructed palate of 〈span〉Whatcheeria deltae〈/span〉 indicates a skull that was unusually narrow: at least 2.2 times longer than wide if the pterygoids are conservatively placed in the horizontal plane. This maximum width is narrower than any other early tetrapod reconstructed so far. Rotating the pterygoids to produce a vaulted palate would produce an even narrower skull. Primitive palatal features include very narrow interpterygoid vacuities and a vomer, palatine, and ectopterygoid with fang-sized replacement pairs. It is derived in that there is no anterior palatal fenestra and the premaxilla has a substantial palatal shelf – a combination of characters shared only with Proterogyrinus among early tetrapods. There is a possible septomaxilla in one specimen. 〈span〉Whatcheeria〈/span〉 differs from and is more derived than 〈span〉Pederpes〈/span〉, its likely sister taxon, in that only the pterygoid is covered with denticles, the vomer, palatine, and ectopterygoid containing labyrinthine teeth only. Reconstructed dental occlusion indicates that the large choana apparently accommodated the large dentary fangs; this would be a unique feature among early tetrapods. The palatal ramus of the pterygoid is longer than the quadrate ramus, which does not have a descending flange. Like Meckel's cartilage in the lower jaw, the palatoquadrate is fully ossified in larger specimens, such that in a posterior view of the skull the pterygoid is mostly hidden from sight by the epipterygoid. The ossified neurocranium consists of the basiparasphenoid and basioccipital; no ossified sphenethmoid has been found. Remains of otic capsules are partial, crushed, and smeared, so no useful morphology is available. The stapes appears to be more columnar and less plate-like than in many other primitive, early tetrapods.〈/p〉〈/div〉
    Print ISSN: 1755-6910
    Electronic ISSN: 1755-6929
    Topics: Geosciences
    Published by Cambridge University Press
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  • 6
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    Palate and braincase of Whatcheeria deltae Lombard & Bolt, 1995 (2018)
    Cambridge University Press
    Details
    Publication Date: 2018-12-18
    Description: The reconstructed palate of Whatcheeria deltae indicates a skull that was unusually narrow: at least 2.2 times longer than wide if the pterygoids are conservatively placed in the horizontal plane. This maximum width is narrower than any other early tetrapod reconstructed so far. Rotating the pterygoids to produce a vaulted palate would produce an even narrower skull. Primitive palatal features include very narrow interpterygoid vacuities and a vomer, palatine, and ectopterygoid with fang-sized replacement pairs. It is derived in that there is no anterior palatal fenestra and the premaxilla has a substantial palatal shelf – a combination of characters shared only with Proterogyrinus among early tetrapods. There is a possible septomaxilla in one specimen. Whatcheeria differs from and is more derived than Pederpes, its likely sister taxon, in that only the pterygoid is covered with denticles, the vomer, palatine, and ectopterygoid containing labyrinthine teeth only. Reconstructed dental occlusion indicates that the large choana apparently accommodated the large dentary fangs; this would be a unique feature among early tetrapods. The palatal ramus of the pterygoid is longer than the quadrate ramus, which does not have a descending flange. Like Meckel's cartilage in the lower jaw, the palatoquadrate is fully ossified in larger specimens, such that in a posterior view of the skull the pterygoid is mostly hidden from sight by the epipterygoid. The ossified neurocranium consists of the basiparasphenoid and basioccipital; no ossified sphenethmoid has been found. Remains of otic capsules are partial, crushed, and smeared, so no useful morphology is available. The stapes appears to be more columnar and less plate-like than in many other primitive, early tetrapods.
    Print ISSN: 1755-6910
    Electronic ISSN: 1755-6929
    Topics: Geosciences
    Published by Cambridge University Press
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  • 7
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    Deltaherpeton hiemstrae, a new colosteid tetrapod from the Mississippian of Iowa (2010)
    Paleontological Society
    Details
    Publication Date: 2010-11-01
    Description: A new colosteid, Deltaherpeton hiemstrae gen. et sp. nov., is described from the Mississippian Upper Viséan site at Delta, Iowa. Deltaherpeton is represented by a skull roof and both jaws. The new taxon is unique among colosteids in having an internasal and single midline postparietal. An additional midline pair of cf. ‘interfrontonasals’ may be present. Characters previously used to define the colosteids are reviewed and a refined diagnosis for the family Colosteidae is presented. Synapomorphies which unite Deltaherpeton, Colosteus, Greererpeton, and Pholidogaster as Colosteidae are: premaxilla with fang pair; dentary with notch for receipt of premaxillary fang; mandible with single elongate exomeckelian fenestra; pre-narial infraorbital lateral line terminating at ventral margin of premaxilla just anterior to external naris; and post-narial infraorbital lateral line terminating at the ventral margin of the maxilla just posterior to the external naris. Our review of dermal bones in the colosteid snout concludes that no specimen is sufficiently free of distortions or breakage to indicate clearly whether or not the prefrontal borders the external naris, or that an anterior tectal is present. The morphology of Deltaherpeton and the revised data presented for colosteids do not clarify the relationship of colosteids to other early tetrapods.
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
    Published by Paleontological Society
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  • 8
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    SIGOURNEA MULTIDENTATA, A NEW STEM TETRAPOD FROM THE UPPER MISSISSIPPIAN OF IOWA, USA (2006)
    Paleontological Society
    Details
    Publication Date: 2006-07-01
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
    Published by Paleontological Society
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  • 9
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    The atlas-axis complex in the late Paleozoic genus Diadectes and the characteristics of the atlas-axis complex across the amphibian to amniote transition (1991)
    Paleontological Society
    Details
    Publication Date: 1991-11-01
    Description: The atlas-axis complex in the Early Permian diadectomorph Diadectes is shown to be similar to those of a variety of primitive amniotes. Diadectes does not possess elements in addition to the standard complement seen in advanced batrachosaurs and primitive amniotes as previously thought. Characteristics of the complex include: paired, well-developed proatlases and atlantal neural arches, lack of atlantal neural spines, an extremely robust atlantal intercentrum, fusion of the atlantal pleurocentrum and axial intercentrum, a large anterior projection of the axial intercentrum, exclusion of the atlantal pleurocentrum from ventral exposure, fusion of axial neural arch and pleurocentrum, and a robustly developed axial neural spine. An analysis of the transformations of the atlas-axis complex in advanced anthracosaurs and primitive amniotes indicates that many of the characteristics of the complex previously thought to be definitive of amniotes or reptiles appear to be conditions common to Diadectes plus Amniota.
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
    Published by Paleontological Society
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  • 10
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    A microsaur from the Mississippian of illinois and a standard format for morphological characters (1999)
    Paleontological Society
    Details
    Publication Date: 1999-09-01
    Description: The oldest known microsaur is preserved in a nodule from the Kinkaid Formation (Mississippian; Elvirian) collected near Goreville, Illinois. At least eight individuals are represented: three by partial skulls plus vertebral column segments with associated limb elements, and five by postcrania only. Skulls are crushed, incomplete, and exposed mainly in palatal view. Palatal bones are denticulate and the palatine has in addition a single large tooth. The basipterygoid process is laterally directed and the basipterygoid joint is open. The atlas carries large articulating facets for proatlantes, a pair of which are identifiable in one specimen. These features have not been found previously in a microsaur. All vertebral segments are dominated by a biconcave pleurocentrum; sutures between the pleurocentrum and neural arch are visible in presacral vertebrae. Distinctive microsaurian intercentra occur between all presacral pleurocentra. Their presence reinforces the hypothesis that microsaur intercentra are homologous with those of other early tetrapods. Caudal vertebrae retain separate haemal arches and some have ribs.Observed microsaur synapomorphies include: atlas with large median odontoid; atlas with concave lateral facets for occipital condyle; paired occipital condyles that are broad and concave; and thin, straplike intercentra. No observed features support a sister-group relationship with any other microsaur species, or placement within any higher level microsaur group. Because significant portions of the skeleton are missing or inaccessible, the Goreville microsaur is not formally named. A standardized, hierarchical format for skeletal characters is introduced that facilitates data sharing and comparison and fosters rapid archiving and retrieval.
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
    Published by Paleontological Society
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