To: All Msg #121, Dec0992 05:20PM Subject: More vestiginal features. Fused bones. These ar
From: Loren I. Petrich
To: All Msg #121, Dec-09-92 05:20PM
Subject: More vestiginal features...
From: email@example.com (Loren I. Petrich)
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
Bird alula or "bastard wing". A much-reduced digit on the
front limb. The two others are retained, though they are fused into
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
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
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
E-Mail Fredric L. Rice / The Skeptic Tank