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Scientists studying the physiology
of dinosaurs have long debated whether
dinosaurs were warm- or cold-blooded.
Line Those who suspect they were warm-
(5) blooded point out that dinosaur bone
is generally fibro-lamellar in nature;
because fibro-lamellar bone is formed
quickly, the bone fibrils, or filaments, are
laid down haphazardly. Consistent with
(10) their rapid growth rate, warm-blooded
animals, such as birds and mammals,
tend to produce fibro-lamellar bone,
whereas reptiles, which are slowgrowing
and cold-blooded, generally
(15) produce bone in which fibrils are laid
down parallel to each other. Moreover,
like the bone of birds and mammals,
dinosaur bone tends to be highly
vascularized, or filled with blood
(20) vessels. These characteristics,
first recognized in the 1930’s,
were documented in the 1960’s by
de Ricqlès, who found highly vascularized,
fibro-lamellar bone in several
(25) groups of dinosaurs. In the 1970’s,
Bakker cited these characteristics as
evidence for the warm-bloodedness of
dinosaurs. Although de Ricqlès urged
caution, arguing for an intermediate type
(30) of dinosaur physiology, a generation of
paleontologists has come to believe
that dinosaur bone is mammalianlike.
In the 1980’s, however, Bakker’s
contention began to be questioned, as a
(35) number of scientists found growth rings
in the bones of various dinosaurs that
are much like those in modern reptiles.
Bone growth in reptiles is periodic in
nature, producing a series of concentric
(40) rings in the bone, not unlike the growth
rings of a tree. Recently, Chinsamy
investigated the bones of two dinosaurs
from the early Jurassic period
(208-187 million years ago), and found
(45) that these bones also had growth rings;
however, they were also partially fibrolamellar
in nature. Chinsamy’s work
raises a question central to the debate
over dinosaur physiology: did dino-
(50) saurs form fibro-lamellar bone because
of an innately high metabolic rate associated
with warm-bloodedness or
because of periods of unusually fast
growth that occurred under favorable
(55) environmental conditions? (Although
modern reptiles generally do not form
fibro-lamellar bone, juvenile crocodiles
raised under optimal environmental
conditions do.) This question remains
(60) unanswered; indeed, taking all the evidence
into account, one cannot make
a definitive statement about dinosaur
physiology on the basis of dinosaur
bone. It may be that dinosaurs had an
(65) intermediate pattern of bone structure
because their physiology was neither
typically reptilian, mammalian, nor avian.
The author of the passage mentions bone growth patterns in juvenile crocodiles most
likely in order to
A. provide support for the argument that reptiles are not related to dinosaurs
B. undermine the claim that most reptiles are slow-growing
C. offer an explanation as to why juvenile crocodiles differ from most modern
reptiles
D. suggest the juvenile crocodiles have a type of physiology intermediate between
that of mammals and that of reptiles
E. suggest that the presence of fibro-lamellar bone does not resolve the debate over
请教，我实在不知道怎样推出E答案（正确答案给的是E），我没思路，或许是没看懂
谢谢 | 
