RC 04 - NOV 22

Thomas Henry Huxley (1825−1895), one of Charles Darwin's earliest and
most staunch defenders, as well as an influential naturalist in his
own right, first observed the many similarities between reptiles and
birds. Huxley noted, for example, that the wings of a bird hid
reptilian fingers. Today, few scientists challenge not only the link
between birds and reptiles in general, but between birds and
theropods, a group of bipedal saurischian dinosaurs. Hundreds of
structural similarities exist, including elongated arms, large eye
openings, swiveling wrists, three forward-facing toes, and hollow
bones.
The most diverse theropod group is the coelurosaurs, a carnivorous
bipedal group that includes the Tyrannosaurus rex and the
Velociraptor, the latter of which is quite similar to the oldest known
bird, the Archaeopteryx. Coelurosauria, in fact, is the clade that
contains all theropods more closely related to birds than to
carnosaurs, and all coelurosaurs have been thought to possess
feathers.
However, a recent find of what seems to be an entirely new—and
apparently featherless—coelurosaur has complicated the subject.
Several suggestions have been made as to why this particular
chicken-sized dinosaur from the Late Jurassic period lacked feathers.
One possibility is that, in some creatures, feathers were replaced by
scales because the feathers were not needed for warmth, recognition of
family members, or mating rituals—uses that feathers were thought to
have had for dinosaurs that did not fly. It is also possible that some
coelurosaurs had feathers in only certain geographic areas.
Another idea is that this particular coelurosaur was so young that it
had not yet grown
feathers.
A more fundamentally profound alternative is that, contrary to
conventional scientific thought, birds and feathered dinosaurs
developed feathers independently of each other rather than from a
common ancestor. This would certainly not be the first case of what is
known as convergent evolution. Fish and certain mammals can swim,but
have evolved this attribute separately. Likewise, insects have wings,
but developed them independently from birds. Luckily, the new fossil
of what has been named a Juravenator is well-preserved almost in its
entirety. More insights into why it did not have feathers will likely
lead to new insights into how other animals did develop this trait.


1. In the passage, the author is primarily interested in:
(A) presenting possible solutions to a problem that has troubled scientists
for years
(B) providing background information and possible explanations for a
curious discovery
(C) answering critics of a controversial theory that is supported by a new
finding
(D) showing how an established idea can become too entrenched in
conventional scientific thought
(E) presenting historical background to a current phenomenon




2. According to the passage, the Archaeopteryx _______________________ .
(A) had feathers but did not fly
(B) is the oldest known coelurosaur
(C) was approximately the size of a chicken
(D) shares some similarities with carnivorous dinosaurs
(E) and the Juravenator developed feathers from a common ancestor




3. According to the passage, feathers on dinosaurs .
(A) were not used for flight
(B) were not always present at birth
(C) were first noted by Huxley
(D) might have evolved from scales
(E) were a characteristic of all coelurosaurs




4. Which of the following can be inferred from the passage?
(A) All adult coelurosaurs possessed feathers.
(B) Coelurosaurs who did not need feathers for warmth or mating rituals
shed those feathers for scales.
(C) Scientists have reached a consensus that certain birds and dinosaurs
are evolutionarily linked.
(D) Thomas Henry Huxley believed in the idea of convergent evolution.
(E) Coeulurosaurs that did not have feathers instead had scales.