. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Skeleton 625 Amphibian larvae, as well as adult perennibranchs, have a caudal fin that may extend some distance anteriorly, but which differs from the caudal fin of fishes in being without skeletal support. Dorsal fins occur in cetaceans (Fig. 75) as they did in ichthyosaurs. Sirenians as well as cetaceans develop caudal appendages, usually spoken of as flukes, which are horizontal rather than vertical in arrangement (Figs. 72 and 73). Like the caudal
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Skeleton 625 Amphibian larvae, as well as adult perennibranchs, have a caudal fin that may extend some distance anteriorly, but which differs from the caudal fin of fishes in being without skeletal support. Dorsal fins occur in cetaceans (Fig. 75) as they did in ichthyosaurs. Sirenians as well as cetaceans develop caudal appendages, usually spoken of as flukes, which are horizontal rather than vertical in arrangement (Figs. 72 and 73). Like the caudal fins of amphibians, all these special appendages of mammals are unsupported by fin rays of any kind. (b) Lateral Appendages in General.—Typically there are two pairs of lateral appendages in all vertebrates. They serve a great variety of uses aside from the primary function of 2 Mo. 5 Mo. Newborn 2Yrs. 6Yrs. 12Yrs. 25Yrs. Foetal Fig. 554. Figures illustrating changes in body proportions during pre- natal and postnatal growth. (After Stratz.) Of vertebrates without paired appendages, the cyclostomes represent a primitive condition. Other legless vertebrates, such as caecilians, snakes, and certain lizards when adult, may be said to be reduced secondarily to this state, for some of them have appendages, at least in their early stages. Legs have been found, for instance, in the embryo of the apodous amphibian, Gymnophiona, -by P. and F. Sarasin. A few vertebrates have only anterior appendages. The list includes the chondrostean Calamoichthys; representatives of the teleost order of Apodes; the caudate Siren; the lizard Chirotes; the orders of Sirenia and Cetacea (although Kiikenthal found hind legs in the embryo of one species of whales) ; and some other Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the or
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