File:The American Museum journal (c1900-(1918)) (17973279730).jpg

Title: The American Museum journal
Identifier: americanmuseumjo17amer (find matches)
Year: c1900-(1918) (c190s)
Authors: American Museum of Natural History
Subjects: Natural history
Publisher: New York : American Museum of Natural History
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: Biodiversity Heritage Library

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EVOLUTIOX OF THE Ili'MAN FACE 370 of tlie fislilikc vcrtelinitcs, that we sec the vertebrate face in its typical rm-iii and that we see all the elements which are characteristic of the face of maiii- mals. p)ven the familiar lamliiiarks ol' the human face are all ))resent. W'c have the nostrils, which are only in- definitely foreshadowed in earlier types ; we have the e3'es, the mouth, the tongue, and the lips. But in the shark teeth of vci'tchi-atcs lias had a ,L;iTat inihience upon the t'volut ion of the fa CO. in the shark the face is vci-y dis- tinctly the directing part of the animal, at the front end of the backbone. We may say that all the elaborate locomo- tive organs (the backbone, the fins, and the muscles which move them) exist chiefly for the purpose of bringing the
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In .sharks we see for the first time the vertebrate face in typical form, with all the elements of the face of man — mouth, tongue, and lips to he brought into contact with the food by the locomotive organs, and noi-trils and eyes to direct the locomotiv(> organs. In the frilled shark (('lilniiijidi).srlarhus) figured we see a suggestion of how teeth were formed in the higher vertebrates. The teeth within the .shark's mouth are enlarged shagreen denticles such as grow on the skin outside the mouth. Aflrr (lannaii the whole face is covered with a tough skin. In certain sharks (Chhuiiijiloscld- cJiiis) we see a suggestion as to how the teeth were formed in higher verte- brates. The tough skin, covering the head and body, is everywhere thickly studded with minute teeth, or denticles, the whole forming the "shagreen" of commerce. Xow the teeth in the .shark's mouth are nothing but enlarged sha- green denticles. At the sides of the mouth the denticles gradually become larger and the skin that bears them be- comes drawn over the margins and on to the inner side of the jaws. I need hardly say that the evolution of the mouth into contact with the food, and that the higher elements of the face, namely the eyes and the nose, exist for the purpose of directing the locomotive apparatus toward the ))rey. In order to consume the food and transform its ))0- tential energy into action, the shark must of course have oxygen, which among fishes is extracted by the Idood from the water surrounding the gills. These gills are supported by cartilagi- nous arches M'hich are of the greatest importance in the later evolution of the face, since there is good evidence tend- ing to show that the upper and lower halves of one of these gill arches actu- ally gave rise to the upper and lower

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