Buccal Floor of Reptiles, a Summary

Great Basin Naturalist Volume 42 Number 3 Article 1 9-30-1982 Buccal floor of eptiles,r a summary Wilmer W. Tanner Brigham Young University David F. Avery Southern Connecticut State College, New Haven Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Tanner, Wilmer W. and Avery, David F. (1982) "Buccal floor of eptiles,r a summary," Great Basin Naturalist: Vol. 42 : No. 3 , Article 1. Available at: https://scholarsarchive.byu.edu/gbn/vol42/iss3/1 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. The Great Basin Naturalist Published at Provo, Utah, by Brigham Young University ISSN 0017-3614 Volume 42 September 30, 1982 No. 3 BUCCAL FLOOR OF REPTILES, A SUMMARY Wilmer W. Tanner' and David F. Avery^ Abstract.— A general survey of the information presently available on the osteology and myology of the hyobranchial apparatus. Included in the survey are examples of the hyobranchial skeleton of the major groups of reptiles, including the Chelonia, Crocodilia, Rhynchocephalia, and Squamata. The myology treats the muscles directly associated with the hyoid as well as those associated with the functioning of the apparatus, but not arising or inserted directly on or from the hyoid. The innervation of the hyobranchial apparatus is reviewed and briefly discussed based on the information available in a few major studies. An attempt is made to cite all pertinent literature references, and in Tables 1 and 2 the references to basic areas are indicated. Twenty-nine plates and figures are included, some of which represent original research. I. Introduction skeletal elements are the jaws, hyoid apparatus, laryngeal cartilages, and tracheal rings. Few anatomical areas have been subjected The associated fleshy parts include the hypo- to such pronounced evolutionary changes as branchial throat musculature, the tongue, and have the branchial apparatus and its deriva- the nerves and blood vessels associated with tives in the vertebrate series. The hyoid ap- them. There is also a variety of glands associ- paratus has responded to these numerous ated with the buccal floor; these are usually adaptive changes with structural and func- -involved with the production of saliva that tional modifications. One needs only to con- may be poisonous. template the change necessary in adapting A complete comparative anatomical treat- from a structure bearing gills to one associ- ise on the buccal floor is not possible at this ated with lungs, from an immovable to a time, primarily because the necessary infor- highly flexible tongue, or to the development mation is not available. Some anatomical of a lamyx and archaic voice to appreciate studies on reptiles are precise and show con- the anatomical importance of this area. Fur- siderable detail; however, the studies have thermore, the class Reptilia consists of both too often been concerned primarily with one primitive (turtles, crocodilians, and Spheno- series of bones or one group of muscles rather don) and specialized (lizards and snakes) than an entire anatomical pattern. As a re- forms that include organisms possessing con- sult, we will confine our remarks to the pres- siderable structural diversification. ent knowledge of the hyoid structure and as- In reptiles the buccal floor consists of os- sociated muscles and nerves in the floor of seous and cartilaginous elements of the bran- the reptilian mouth. Many studies touch on chial skeleton and the associated connective the subject at hand in various ways. We have, and muscular tissues. Included among the therefore, included in the bibliography many 'Life Science Museum, Brigham Young University, Provo, Utah 84602. 'Department of Biology, Southern Connecticut State College, New Haven, Cormecticut 06515. 273 274 Great Basin Naturalist Vol. 42, No. 3 studies not cited in the text. These have been hyoid is composed of several osseous and car- useful in our examination of the materials tilagenous elements and exhibits a variety of available and are as follows: Adams 1919, degrees of ossification. As a general rule, the 1925, Ashley 1955, Barrows and Smith 1947, larger (or older) the animal, the more ossified Beddard 1905, Bellairs 1950, Bergman 1961, is the hyoid apparatus. In most reptiles, ex- 1965, Boltt and Ewer 1964, Brock 1938, Bull- cept in some snakes, the hyoid apparatus is a ock and Tanner 1966, Byerly 1926, Chaine spreading, flexible structure that occupies 1902, Chiasson 1962, Cowan and Hick 1951, space in, and forms a support for, most of the Davis 1934, Duda 1965, Dullemeijer 1956, floor of the oropharynx. 1958, El Toubi 1938, 1947a, 1947b, El Toubi Although the phylogenetic relationships of and Kalil 1952, Eyal-Giladi 1964, Evans the hyoid apparatus and visceral arches are 1955, Gandolfi 1908, Gans 1961, George not completely understood, it is known that 1948, George and Shad 1954, 1955, Haas the hyoid apparatus is derived from the hyoid 1973, Harris 1963, Hey- 1952, 1960, 1968, cartilage and the two succeeding arches. Ro- mans 1970, lordansky 1970, Iyer 1942, 1943, mer (1956) believes that the hyoid of ances- Kamal, Hammouda, and Mokhtar 1970, Kes- tral reptiles must have been more extensive teven 1944, Kingman 1932, Kluge 1962, and that traces of a third branchial cornu can Kochva 1958, Liem, Marx, and Rabb 1971, be seen in some reptilian embryos. The third Mahendra 1949, Malam 1941, McKay 1889, cornu is well demonstrated in monotreme Minot 1880, Mivart 1867, Norris and Lowe mammals. 1951, Oldham, Smith, and Miller 1970, Park- The nomenclature pertaining to the hyoid er 1880, Ping 1932, Presch 1971, Rathor is not uniform. Furbringer (1922) describes 1969, Reese 1923, Rice 1920, Rieppel 1981, the first two pairs of arches as the cornu Rosenberg 1968, Sanders 1870, 1872, 1874, hyale and the cornu brachiale I, respectively; Schumacher 1956c, Sewertzoff 1929, Shah the third arch is called the cornu branchiale 1963, Sidky 1967, Siebenrock 1892a, 1892b, II. This latter arch is referred to by Beddard 1893, 1894, 1895, Sinitsin 1928, and Varkey as the branchial process and as the 1979. (1907) basibranchial by Gnanamuthu (1937). The Tables 1 and 2 provide additional informa- third arch is seemingly absent in several rep- tion on the material covered by these and tiles, causing some workers to refer to the re- other authors dealing with buccal floor and maining two arches as the anterior and poste- associated structures. rior cornua. Unfortunately, the identity of the third arch has not been clearly ascer- II. Apparatus Hyoid tained. The third arch may be a degenerate structure expressed as projections from the General basihyoid or body of the hyoid, or it may be The branchial skeleton, including the vis- present as a separate arch with either the ceral arches, which we have associated with first or second arch being lost. In the Ophidia the more primitive gill-bearing vertebrates, and some burrowing lizards such as Anniella, has been recast in the tetrapods where its Dibamus, Acontias, Acontophiops, and Typh- structure and function have been modified. losaurus, the hyoid is greatly reduced and the The branchial skeleton now appears in tetra- identity of the posterior cornua is not posi- pods as a part of the skull; it includes the jaw tively established. (See Rieppel 1981 for a and the hearing apparatus, as well as the la- more complete discussion.) A similar situa- rynx and trachial cartilage supports. The tion exists in the Testudines and Crocodilia. tetrapod has also retained the more central The development of the hyoid apparatus has part of the old visceral skeleton, which is been discussed by Rathke (1839), Kallius now known as the hyoid apparatus. (1901), Howes and Swinnerton (1901), Peyer Because reptiles have lost the gill appa- (1912), Edgeworth (1935), DeBeer (1937), ratus in all stages of development, the hyoid Pringle (1954), El Toubi and Kamal apparatus has assumed the function of a sup- (1959a,b), El Toubi and Majid (1961), Kamal port for the tongue, glottis, and sometimes an and Hammouda (1965), Langebartel (1968), extended dewlap. In modern reptiles, the Rieppel (1981), and others (Table 1). These September 1982 Tanner, Avery: Buccal Floor of Reptiles 275 Table 1. Publications dealing with the buccal floor of reptiles. Genus Hyoid Tongue Musculature Nerves Order Chelonia Suborder Pleurodina Pelomedusidae Pehtsios Poglayen-Neuwall Poglayen-Neuwall 1953 1953 Chelidae Batrochemys Poglayen-Neuwall Poglayen-Neuwall 1953 1953 CJielodina Furbringer 1922 Winokur 1974 Graper 1932 Kesteren 1944 Kesteren 1944 Poglayen-Neuwall Poglayen-Neuwall 1953 1953 Shah 1963 Suborder Cryptodira Dermatemydidae Dennatemys Furbringer 1922 Chelydridae Chelydra Furbringer 1922 Winokur 1974 Camp 1923 Poglayen-Neuwall Edgeworth 1935 1953 Schumacher Graper 1932 Soliman 1964 1973 Poglayen-N euwall 1953 Schumacher 1973 Kinosternon Furbringer 1922 Poglayen-Neuwall Poglayen-Neuwall 1953 1953 Schumacher 1973 Schumacher 1973 Sternotherus Furbringer 1922 Poglayen-Neuwall Poglayen-Neuwall Schumacher 1973 1953 1953 Schumacher 1973 Testudinidae Chrysemys Furbringer 1922 Poglayen-Neuwall Poglayen-Neuwall Ashley 1955 1953 1953 Schumacher 1973 Ashley 1955 Schumacher 1973 Graper 1932 Lubosch 1933 C/em 771 1/5 Siebenrock 1898 Furbringer 1922 Lubosch 1933

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