Morphological analysis of tendinous structure in the American alligator jaw muscles

Shimada, Kazuyuki; Sato, Iwao; Ezure, Hiromitsu

doi:10.1002/jmor.1052170206

Cited by 5 publications

(8 citation statements)

References 27 publications

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“…Snively & Russell 2007). More recent descriptions of crocodilian jaw musculature and tendons may be found in Schumacher (1973), van Drongelen & Dullemeijer (1982), Busbey (1989), Iordansky (2000), Holliday & Witmer (2007) and Bona & Desojo (2011), and of the tendons in Shimada et al (1993). Although the conclusions presented here are considered reliable, they are based on several levels of inference.…”

Section: Methodsmentioning

confidence: 54%

“…The tendinous structure of the adductors of Alligator mississippiensis is shown in Figures 1 and 2 and described by Iordansky (1964), Schumacher (1973), Busbey (1989), Shimada et al (1993) and Iordansky (2000).…”

Section: Reconstruction Of Tendons and Comparison With Alligator Missmentioning

confidence: 92%

“…The reconstruction of the musculature is based largely on dissections of A. mississipiensis and P. trigonatus and descriptions of crocodilian jaw musculature in the literature (Poglayen-Neuwall 1953, and particularly Iordansky, 1964). More recent descriptions of crocodilian jaw musculature and tendons may be found in Schumacher (1973), van Drongelen & Dullemeijer (1982), Busbey (1989), Iordansky (2000), Holliday & Witmer (2007) and Bona & Desojo (2011), and of the tendons in Shimada et al (1993).…”

Section: Methodsmentioning

confidence: 97%

“…The lever arms and lengths of the various muscles were estimated from a physical model of a lateral projection of the reconstructed skull and jaws of AMNH 3160. Shimada et al (1993) suggested that, in A. mississippiensis, the tendons attaching to the M. pseudotemporalis and M. intramandibularis may be sufficiently elastic to store potential energy during the opening of the jaws, to be released during closing. Details of this process are given in Molnar (2013, fig.…”

Section: Methodsmentioning

confidence: 99%

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Jaw musculature and jaw mechanics ofSebecus icaeorhinusSimpson, 1937 (Mesoeucrocodylia, Sebecosuchia)

Molnar

2012

Earth and Environmental Science Transactions of the Royal Socie

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Sebecus icaeorhinus possessed a narrow, elevated snout and laterally compressed, serrate teeth, unlike modern crocodilians, but superficially similar to those of theropod dinosaurs. Lever arms of the mandibular adductors were generally relatively greater than those of Crocodylus niloticus. Some of the adductors and the depressor mandibulae were relatively larger than in Alligator mississippiensis. Thus Sebecus may have had a stronger bite than the modern forms examined. The form of the teeth suggests use in cutting. Some theropod dinosaurs are similar to sebecosuchians in the possession of relatively deep, narrow snouts and laterally-compressed, serrate teeth. However, the adductor structure was substantially different from that of Sebecus. The presence of muscle and tendon attachments in Sebecus suggests the adductor structure of mesoeucrocodylians is conservative and was established before divergence of the sebecosuchian and neosuchian lineages. No results presented here contradict the interpretation of sebecosuchians as land-dwelling predators.

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Section: Methodsmentioning

confidence: 54%

Section: Reconstruction Of Tendons and Comparison With Alligator Missmentioning

confidence: 92%

Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

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Jaw musculature and jaw mechanics ofSebecus icaeorhinusSimpson, 1937 (Mesoeucrocodylia, Sebecosuchia)

Molnar

2012

Earth and Environmental Science Transactions of the Royal Socie

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“…We consider that these differences may be due to the different morphology of the masticatory muscles induced by the different sizes of the jaw and jaw muscles. The alligator is a violent reptile animal, and has a big jaw with seven bundles of tendinous structures (Shimada et al, 1993) which are completely different from those of mammals. These structure reflect the kinetic forces of the stretch applied to each tendon by the muscle during jaw movements.…”

Section: Discussionmentioning

confidence: 99%

Morphometric Comparison of the Motor Trigeminal Neurons

Setoyama

Zhou

Goto

et al. 1997

Okajimas Folia Anatomica Japonica

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Summary: Comparative morphological and morphometric studies of the motor trigeminal nucleus (MTN) were carried out on the brains of an alligator, a human being and a rat for the first time. Differences in neurons regarding sizes, areas, numbers, column volumes, neuropil indices and circularity ratios were found. The results showed that the positions and shapes of the MTN were different, and the shapes of motor neurons were different, too. The average area of motor trigeminal neurons was the largest in the alligator, compared with the area in the human being, and the rat; the number of neurons and the column volume of MTN were the largest in the human being. As for the neuropil indices, the value was in descending order: alligator, human being and rat; whereas for the circularity ratio of neuronal cell bodies, the order was: rat, alligator, and human being. We concluded that the size of motor neurons in the MTN may be related to the power of masticatory muscles, and there may be a connection between jaw sizes and shapes and sizes of the motor neurons in the MTN.The motor trigeminal nucleus (MTN), which supplies motor fibres to the masticatory muscles responsible for controlling the closing and opening movement of the jaw, is an oval column of somatotopically organised cells (Palkovits & Brownstein, 1988), and consists of large motor neurons in the human being Mogoseanu et al., 1993;Palkovits & Brownstein, 1988).There have been reports about the human brainstem nuclei studied by morphometric method (Konigmark & Murphy, 1972;Moatamed, 1966;Monagle, 1974;Tomasch & Etemadi, 1962) and a few comparative studies concerning the motor neuron organization of the MTN in rats , as well as a morphometric study of the MTN in developing human brain (Hamano et al., 1988).In this study, we checked whether there were any morphological and morphometrical differences of the MTN among various animals including humans in relation to different jaw sizes. We chose the alligator, the human being and the rat as large, medium and small jaw samples. The position of the MTN innervating masticatory muscles is considered to be practically the same in various animals such as rats (Card et al., 1986;Limwongse & DeSantis, 1977;Mogoseanu et al., 1993;Weijs et al., 1993), cats (Mizuno et al., 1975), guinea pigs (Hecht et al., 1993;Uemura et al., 1982), rabbits (Matsuda et al., 1978) and macaque monkeys (Mizuno et al., 1981), although there might be slight differences in the MTN depending on the animal considered. No data, however, have been included in the literature concerning the morphometric analysis of neurons in the MTN from a comparative point of view. With the help of an image-analyzer and a computer, it is possible to get detailed data about nuclei of the brain stem. In this study the areas of neuronal cells of the MTN in the alligator, the human being and the rat were carefully measured. The relationship between jaw size and neuronal size of the MTN is discussed. Material and MethodsThe brains used in this study were as follows: a human b...

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Feeding in Crocodylians and Their Relatives: Functional Insights from Ontogeny and Evolution

Gignac

O’Brien

Turner

et al. 2019

Fascinating Life Sciences

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Morphological analysis of tendinous structure in the American alligator jaw muscles

Cited by 5 publications

References 27 publications

Jaw musculature and jaw mechanics ofSebecus icaeorhinusSimpson, 1937 (Mesoeucrocodylia, Sebecosuchia)

Jaw musculature and jaw mechanics ofSebecus icaeorhinusSimpson, 1937 (Mesoeucrocodylia, Sebecosuchia)

Morphometric Comparison of the Motor Trigeminal Neurons

Feeding in Crocodylians and Their Relatives: Functional Insights from Ontogeny and Evolution

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