Jaw Muscles of the Crocodiles: Structure, Synonymy, and Some Implications on Homology and Functions

Nikolai N. Iordansky

Abstract


Structure of jaw muscles and their tendons in crocodiles is reviewed. Crocodiles are characterized by following peculiarities of jaw musculature: 1) the jaw adductors consist of the whole muscle mass, and their portions are poorly differentiated; 2) there is large M. pterygoideus anterior; 3) M. pseudotemporalis is represented by two small bundles of fibers; 4) there is large M. intramandibularis. It is hypothesized, that M. pterygoideus anterior evolved from the main part of the pseudotemporal muscle, by shifting of its site of origin into the orbit. Crocodilian M. intramandibularis may be homologous to the intramandibular belly of the chelonian M. adductor mandibulae internus digastricus. Functions of M. intramandibularis are discussed. Probably, the most important of these is distribution and dissipation of enormous loads applied to lower jaw by the powerful anterio-dorsal jaw adductors.

Keywords


jaw musculature; crocodiles; homology; functions

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References


Anderson H. (1936), «The jaw musculature of the phytosaur, Machaeroprosopus», J. Morphol., 59(3), 549 – 589.

Busbey A. B., III (1989), «Form and function of the feeding apparatus of Alligator mississippiensis», J. Morphol., 202(1), 99 – 127.

Cleuren J. and De Vree F. (1992), «Kinematics of the jaw and hyolingual apparatus during feeding in Caiman crocodilus», J. Morphol., 212(2), 141 – 154.

van Drongelen V. and Dullemeijer P. (1982), «The feeding apparatus of Caiman crocodilus, a functional-morphological study», Anat. Anz., 151(4), 337 – 366.

Iordansky N. N. (1964), «The jaw muscles of the crocodiles and some relating structures of the crocodilian skull», Anat. Anz., 115(3), 256 – 280.

Iordansky N. N. (1973), «The skull of the Crocodilia», in: C. Gans (ed.), Biology of the Reptilia. Vol. 4. Morphology D, Acad. Press, London – New York, pp. 201 – 262.

Iordansky N. N. (1990), Evolution of Complex Adaptations: Jaw Apparatus of the Amphibians and Reptiles, Nauka, Moscow [in Russian].

Iordansky N. N. (1994), «Tendons of jaw muscles in Amphibia and Reptilia: homology and evolution», Russ. J. Herpetol., 1(1), 13 – 20.

Iordansky N. N. (1996), «Evolution of the musculature of the jaw apparatus in the Amphibia», in: Advances in Amphibian Research in the Former Soviet Union, Vol. 1, Sofia – Moscow, pp. 3 – 26.

Lakjer T. (1926), Studien über die Trigeminus-versorgte Kaumuskulatur der Sauropsiden, Rietzel, Copenhagen.

Lubosch W. (1933), «Untersuchungen über die Visceralmuskulatur der Sauropsiden», Gegenb. Morphol. Jahrb., 72(4), 584 – 666.

Luther A. (1913), «Über die vom N. trigeminus versorgte Muskulatur der Ganoiden und Dipneusten», Acta Soc. Sci. Fennicae, 41(9), 1 – 72.

Poglayen-Neuwall I. (1953a), «Untersuchungen der Kiefermuskulatur und deren Innervation bei Schidkröten», Acta Zool. Stockholm, 34, 241 – 292.

Poglayen-Neuwall I. (1953b), «Untersuchungen der Kiefermuskulatur und deren Innervation an Krokodilen», Anat. Anz., 99(16 – 17), 257 – 276.

Schumacher G.-H. (1973), «The head muscles and hyolaryngeal skeleton of turtles and crocodilians», in: C. Gans (ed.), Biology of the Reptilia. Vol. 4. Morphology D, Acad. Press, London – New York, pp. 101 – 200.

Shimada K., Sato I., and Ezure H. (1993), «Morphological analysis of tendinous structure in the American Alligator jaw muscles», J. Morphol., 217(2), 171 – 181.

Shute C. C. D. and Bellairs A. d’A. (1955), «The external ear in Crocodilia», Proc. Zool. Soc. London, 124(4), 741 – 748.




DOI: http://dx.doi.org/10.30906/1026-2296-2019-7-%25s-41-50

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