HYOBRANCHIAL APPARATUS OF THE CRYPTOBRANCHOIDEA (AMPHIBIA) Douglas C. Cox and Wilmer W. Tanner Abstract. — This report is a comparative study of the hyobranchial skeleton of the three species in the family Cryptobranchidae and four species of the family Hynohiidae, all of which are figured. Anatomical differences between the cryptobranchids and their relationship to hynobiids are noted and discussed. Reference is made to a relationship that may exist between these families and other salamander families, particularly the possible relationship of the Hynohiidae to the super families Ambystomatoidea or possibly Plethodontoidea. The primary purpose of this study was to examine and compare the hyobranchial skele-ton of representatives of the families Crypto-branchidae and Hynobiidae. We were con-cerned not only with the anatomical rela-tionships of the two families, but also with the basic differences between available genera within the families. Much has been done to establish an understanding of anatomical rela-tionships primarily involving skeletal and soft tissue comparative anatomy of other families, particularly Ambystomatidae, Plethodonti-dae, and Salamandridae. The studies by Humphry (1872) and Dunn (1923, 1926) were followed by research of Noble (1931), Francis (1934), Edgeworth (1935), Piatt (1935, 1939, 1940), Taylor (1944), Tanner (1950, 1952), Fox (1954), Wake (1966), Wake and Ozeti (1969), Nickerson and Mays (1972), Estes (1981), Du-ellman and Trueb (1986), and others cited below, involving cytogenetic studies with the intent to provide data showing familial rela-tionships. The examination of the relationships of the Cryptobranchoidea by Dunn (1923) estab-lished the primitive characters of external fertilization and retention of the angular bone in the lower jaw. These characters have not only placed the cryptobranchids and hynobi-ids as primitive groups of salamanders, but also as possible descendants of ancestral stock similar to those from which other salamander lines might have arisen. Dunn (1923) also noted the following: both families possess nasals that meet at the middorsal line, and the premaxillary spines are short in contrast to other families with separate nasals and long spines. Recent studies also indicate that the crypto-branchids are primitive in that they have a large number of chromosomes (60). Mores-calchi et al. (1977, 1979) give the structure and numbers of chromosomes for the three cryp-tobranchid species, with each having 60, and list the following hynobiid species and their chromosome numbers: Ranodon sibiricus, 2n = 66; Batrachuperus mustersi, 2n = 62; Ony-chodactylus japonicus, 2n = 58 ± 2; Hyno-bius dunni, H. nebulosus, and H. tsuensis, each with 2n = 56. A study by Sessions et al. (1982) provides essentially the same informa-tion, listing 30 pairs of chromosomes in the genus Andrias as compared to 11-14 pairs in other families of North American salaman-ders. Taketa and Nickerson (1973) deter-mined the relative electrophoretic mobilities of the hemoglobins of three families of sala-manders represented by Cryptobranchus, Necturus, and Hynobius, when compared with adult human HbA, at pH 8.4. It is note-worthy that Cryptobranchus has a single com-ponent with greater mobility than the two components in Hynobius tsuensis. The relationship of the cryptobranchids to other families of salamanders and particularly to the hynobiids was noted by Dunn (1923). He indicated that cryptobranchids are more closely related to the hynobiids than perhaps to other salamander families. While this may yet be true, there are substantial differences between the basic structures of the throat anatomy of the hynobiids and the crypto-branchids. This is particularly evident in the bony and cartilaginous structures. If there is indeed a close relationship, it is apparent-ly one based on such characters as external Life Science Museum, Brigham Young University, Provo, Utah 84602 482
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