To: All Msg #121, Dec0992 05:20PM Subject: More vestiginal features. Fused bones. These ar

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From: Loren I. Petrich To: All Msg #121, Dec-09-92 05:20PM Subject: More vestiginal features... Organization: LLNL From: (Loren I. Petrich) Message-ID: <> Newsgroups: Fused bones. These are bones that start out separate and become knitted together for added strength. Human examples are the skull and the pelvis; birds have several bones in their front limbs (wings) fused. Bird alula or "bastard wing". A much-reduced digit on the front limb. The two others are retained, though they are fused into one piece. The Hoatzin chick's claws. The claws on their wing limbs enable them to climb away from potential predators; their presence indicates that all the clawless-winged birds have the potential of growing claws on their wing limbs, which is inherited from their clawed-limbed land ancestors, which were probably small theropod (carnivorous) dinosaurs. Hollowness of dodo and penguin bones. It is not critical for ground birds to reduce weight with hollow bones of the sort that flying birds have. Animals which make teeth as fetuses, then resorb them: Baleen whales, anteaters, and some ungulates (cows have upper front teeth which they later resorb). Gill bars of tetrapod (land-vertebrate and descendant) embryos. The cartilage gill bars appear, only to disappear or be reworked with later growth. Of these animals, only amphibians have gills, and that only in the larval (tadpole) stage. Most adult amphibians and all the rest are air breathers; even the aquatic ones do not grow gills to use underwater. Aquatic-tetrapod air breathing and land breeding. Largely aquatic animals like sea turtles, Galapagos iguanas, sea snakes, crocodilians, water birds including penguins, phocids (seals, sea lions, and walruses), and cetaceans (dolphins and whales) all have to come up to the surface to breathe; all of them but the sea snakes and the cetaceans lay eggs or give birth on the land. Though the sea snakes and cetaceans are completely aquatic, giving birth in the water, they still have to breathe air, which is a limitation for a completely aquatic animal. Jaw origins from gill bars. In jawed-vertebrate embryos, the jaws are formed from the gill bars closest to the mouth. In jawless fish (lampreys and hagfish), these gill bars stay gill bars. This circumstance indicates an origin of jaws from gill bars. The mammalian amniotic sac. This is a vestigial eggshell that surrounds the fetus. Live birth evolved out of retaining an egg inside. Tadpoles. Immature frogs go through this phase, in which they look and act much like fish. The aquatic embryos of land salamanders, which live on the land from hatching. Tails of human embryos. Though tails are a nearly universal vertebrate feature, and are present in all the embryos, they are lost in later growth in our species and the most closely related ones (the apes), leaving only a tiny bone on the pelvis, the coccyx. Rudimentary legs of some snakes (boas, etc.). Other species of snakes seem to do fine without them. The small lung of snakes with only one lung significantly large. It is an inheritance from two-lunged ancestors. Small wings of flightless female moths in certain species. In most other species, as with winged insects in general, both sexes, and not only the male, have functional wings. Stumpy tails and other such features of some domestic animals bred to have none. Nonfunctional pistils in male flowers. Since the predominant configuration of flowers is to have both sexes of reproductive organs (stamens and pistils), the pistil of a flower with only stamens functional is vestigial. Certain plants [Serophulariaceae (Darwin's Origin of Species)] have reduced stamens. -- /Loren Petrich, the Master Blaster /


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