. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. A Jack of All Trades 212. made up of large dermal plates (Fig. 36d), which were usually embossed in bas relief, and sometimes bore along the back formidable spines project- ing upward two feet or more. The corium in modern reptiles plays a secondary role, while the epi- dermis reaches perhaps a greater elaboration than in any other group of vertebrates. Among birds and mammals scaliness is of ex- ceptional occurrence. The scaly legs and feet of feathered b
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. A Jack of All Trades 212. made up of large dermal plates (Fig. 36d), which were usually embossed in bas relief, and sometimes bore along the back formidable spines project- ing upward two feet or more. The corium in modern reptiles plays a secondary role, while the epi- dermis reaches perhaps a greater elaboration than in any other group of vertebrates. Among birds and mammals scaliness is of ex- ceptional occurrence. The scaly legs and feet of feathered birds (Fig. 149) reveal their reptilian an- cestry, while there are a few scale-specialists among mammals. 7. Birds Anyone who has ever attempted taxidermy i u i ti- i -i * • i • Fie. 149. Scaly foot of knows how loose, thin, and easilv torn is the skin & '. . J . an osprcy. (After of a bird. Those parts not covered by feathers, like Schaff.) the shanks and the bare areas around the base of the beak, exhibit a thickened corneal layer of epidermis, but everywhere else not only the epidermis but also the corium is reduced to a delicate thinness. The typical looseness of a bird's skin, so unlike the tightly fitting integument of the fishes, is an advantage in flight, enabling the muscles, unhampered by a binding integumentary covering, to contract freely and to change their shape easily. The looseness of the skin on the belly of penguins serves a special purpose adapted to icy an- tarctic conditions. During incubation the single egg is lifted off the frozen ground to a secure position on top of the webbed feet of the parent bird and a generous apron of loose skin from the region of the belly is snugly wrapped around the egg to keep it warm. Exoskeletal structures of birds, such as feathers, beaks, leg-scales and claws, are entirely epidermal, since dermal elements like the scales of fishes or the bony plates of certain reptiles are absent in this Please note tha
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