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The feeding mechanism of the salamanders has never been discussed comparatively. While a detailed review must await a more complete knowledge of the morphology, ecology, and behavior of these animals, certain broad generalizations are now possible. These have direct bearing upon the classification of salamanders, and are attempted here. Salamander families with terrestrial representatives, the Hynobiidae, Ambystomatidae, Plethodontidae, and Salamandridae, each contain species which undergo transformation from an aquatic to a terrestrial existence. Both aquatic and terrestrial life forms have structural modifications correlated with their specific habitat. Thus one must discuss not only the phylogeny of functional shifts in feeding structures, but their ontogeny as well. The present discussion emphasizes the interaction of the tongue and palatal teeth. Minimal mention will be made of paedomorphic evolutionary pathways, notorious in salamanders. This is best handled elsewhere and at appropriate length. The result is a certain amount of taxonomic generalization. THE GENERAL PATTERN OF ADAPTATION Structural Progression of Tongue Types

Regional variation in the vertebral column of several species of salamanders (families Ambystomatidae, Salamandridae and Plethodontidae) is analyzed. Measurements of three dimensions, centrum length, prezygapophyseal width, and transverse process length, provide the data. Ontogenetic, interspecific, intergeneric and interfamilial patterns of positional variation are diagrammed and discussed. Distinctive patterns of variation characterize the families, genera, and to a lesser extent, the species. The patterns of ambystomatid salamanders are the most generalized, and probably reflect derivation from a primitive ancestral stock. The most specialized conditions occur in the fully terrestrial plethodontids, a group generally considered to be highly derived. Data such as those presented here will aid in the identification of fossils. The patterns described have functional significance. For example, species which have an aquatic larval stage and which return to aquatic breeding sites have vertebrae which taper in length and width behind the pelvis. This is a feature associated with production of a traveling wave in the tail which is necessary for propulsion in water. Fully terrestrial species do not have a tapering column. In them, standing waves, such as occur in the trunk region of all species, typically occur in the tail. The caudal vertebrae of terrestrial species are rather uniform in dimensions for some distance, and the tail is cylindrical in form. Other functionally important features include the narrowing and shortening of some anterior vertebrae, associated with the development of a neck in some species with tongue feeding mechanisms. In contrast, species which use their heads as wedges during locomotion have broadened anterior vertebrae which serve as sites of origin for hypertrophied neck muscles.

The primitive structure of the salamander otic capsule (exemplified by Hynobius) includes both operculum and columella in the fenestra vestibuli and connection of operculum with suprascapsular cartilage by an “opercularis” muscle formed by levator scapulae. Larvae of Hynobiidae, Ambystomatidae, and Salamandridae have early development of columella and stilus, which are used in sound transmission via the suspensorium until the development of the operculum and its muscular connection with the shoulder girdle at metamorphosis. Hynobiids and ambystomatids show parallel trends toward reduction or fusion of the operculum and widening of the attachment area of the levator scapulae on the suprascapular cartilage, and some members of both families have lost the operculum. The Salamandridae have lost columella and stilus as adult structures, but extend the attachment of levator scapulae ventrally by a division resulting in attachment to the scapulocoracoid, probably as an adaptation for better reception and transmission of sound vibrations in terrestrial environments. The Plethodontidae differ strikingly in otic structure from the other families in having an operculum present in the larval stage and fused to columella, and in utilization of part of the cucullaris major as an “opercularis” muscle. These changes are probably the result of changes in orientation of the fenestra vestibuli. In plethodontids with aquatic larval stages the columella is retained as a sound-transmitting element, but in many specialized forms it is reduced or absent. Close correlation of otic structures with ecology limits their use as evolutionary indicators in salamanders. However, the general pattern of otic structures in salamanders, and the magnitude of differences in this region seen in plethodontids, indicates that the latter are probably not derived from the salamandrids, but from a primitive salamander stock.

Eastern red-spotted newts (Notophthalmus viridescens, Salamandridae) are rarely attacked by leeches. This protection is not shared by related salamandrids or by Ambystoma (Ambystomatidae). Tetrodotoxin is not the repelent. The immunity of Notophthalmus to leech parasitism is probably most significant in its aquatic stages, although the terrestrial efts are also protected.

Triton littoreus [spec. nov.] Triton. Habitat in foraminibus Rupium submarinarum., Published as part of Linnaeus, Carolus, 1758, Systema Naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, Stockholm :Laurentius Salvius on page 658, DOI: 10.5962/bhl.title.542, http://zenodo.org/record/3922206

Triton [gen. nov.] Corpus oblongum. Os lingua involuta, spirali. Tentacula XVI: utrinque 6: posticis cheliferis., Published as part of Linnaeus, Carolus, 1758, Systema Naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, Stockholm :Laurentius Salvius on page 658, DOI: 10.5962/bhl.title.542, http://zenodo.org/record/3922206

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