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IGUANA  •  VOLUME 13, NUMBER 2  •  JUNE 2006 145HISTORICAL PERSPECTIVE

below. Finally, Hans Klingel (1965) set forth the results of some
interesting experiments on the method of gliding in Draco; parts
of his paper are summarized below.

From these reports it is obvious that Draco is able to glide
and is, indeed, an accomplished glider. In spite of the observa-
tions by the several authorities who have described the gliding
aptitudes of the oriental “flying dragon,” there have been no
analyses of its anatomical adaptations for gliding. There are no

INTRODUCTION

In connection with the detailed description of a Triassic reptile,
obviously adapted for gliding because of the presence of enor-

mously elongated and curved ribs, it became apparent that a
comparative study of the modern gliding lizard Draco was in
order. Various pertinent publications were examined, with the
surprising discovery that, until recently, very little attention has
been given to the gliding activities of this lizard. In fact, some
authors have expressed doubts as to the ability of Draco to glide
at all. Other authors have, however, given definite proof of glid-
ing ability in this reptile. Two good descriptions are those of
Hairston (1957) and Herre (1958), quoted in part below. Dr.
John R. Hendrickson of Honolulu, Hawaii, has made excellent
observations of the gliding behavior of Draco, of which one
account, taken from a letter to the present writer, is also quoted

H I S T O R I C A L  P E R S P E C T I V E

Adaptations for Gliding 
in the Lizard Draco1

Edwin H. Colbert

1 Permission to reprint this article is courtesy of the American Museum
of Natural History Library, New York, New York. The article was orig-
inally published as American Museum Novitates No. 2283, 10 March
1967. This and other Museum herpetological publications can be
downloaded in full, free of charge, at http://research.amnh.org/her-
petology/pubindex/.

Lizards in the genus Draco are accomplished gliders. The “wings” of this nesting D. sumatranus are clearly visible.

M
A

R
C

U
S 

N
G

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146 IGUANA  •  VOLUME 13, NUMBER 2  •  JUNE 2006

descriptions of the muscles involved in the control of the wings
(the word “wing,” as used herein, designates the gliding mem-
brane of Draco), no measurements based on wing shapes and
areas and body weights, and no correlative interpretations of rela-
tionships between wing areas and body weights. The purpose of
the present paper is to correct, in some small way, this deficiency
in our knowledge of gliding by Draco.

This paper has been inspired not only by curiosity about
gliding in Draco but also by the evidence gained from the study
of the fossil reptile, mentioned above, as well as from closely
related fossils found within recent years in the Triassic fissure fill-
ings of the Bristol Channel area of England, that the Draco mode
of gliding, whereby a wing is formed of a membrane stretched
between greatly elongated, free ribs, is geologically probably the
oldest attempt at aerial locomotion among the backboned ani-
mals. Reptiles that were able to glide on a rib-supported wing,
with the four legs completely free for landing and for running
about on the trunks and limbs of trees or on cliffs and rocks, were
living in the Northern Hemisphere during late Triassic times
some 200 million years ago perhaps 20 million years or more
before the first true flying reptiles, the pterosaurs, and 60 million
years or more before the first birds. Here we see the first experi-
ment among the vertebrates in aerial locomotion, and as such it
is important in the long perspective of aerial locomotion among
animals and by man.

GLIDING FLIGHT OF DRACO
Four eyewitness accounts of flight in this lizard are presented [edi-
tor’s note: two of these have been omitted here]. These descrip-
tions, all by herpetologists, show that its gliding abilities are more
extensive and subtle than is generally realized.

COLBERT

In these lizards, elongated ribs on each side support the wing mem-
branes. Historical drawing from Dover’s Animals.

Editor’s Remarks
Elsewhere in this issue, an article by Lee Grismer focuses on the “flying” reptiles found in southeastern Asia. To accompany
that piece, we chose to include a classic paper on a similar topic by Edwin H. Colbert, whose rich biography is summarized
after the article.

This piece was published in 1967, the year that saw the world’s first successful human heart transplant. The DNA mol-
ecule, today fodder for endless TV whodunits and real-life courtroom dramas, was fully decoded just the year before. Biological
exploration of some parts of the world was in full swing, but the main involvement of the United States in Asia stemmed from
the ongoing war in Vietnam. By the time that war ended in the early 1970s, over 2.5 million Americans had served and almost
50,000 had died there, but few of them had had the time to engage in scientific research. Our understanding of the biology
of the region was extremely poor. Thus, it is not surprising that Edwin Colbert begins his paper by discussing what even ama-
teur herpetologists now take for granted: That lizards of the genus Draco have “wings” and can effectively glide between trees.
A paleontologist first, Colbert became interested in the issue because of his focus on flight in dinosaurs. This paper provided
some of the earliest descriptions of reptilian “flight” and the mechanisms that support it. It is, in many ways, far ahead of its
times, bringing a mechanistic, engineering approach that would not become common in herpetology until many years later.
This paper is still frequently cited in studies of reptilian gliding in general and the biology of the genus Draco in particular.

Parts of Asia remain remote and poorly studied even today. Just a few weeks ago, in early 2006, reports emerged in all
the major media of the results of an expedition to a previously unexplored part of Indonesia. Despite the brevity of the visit,
the work yielded many new species and biological insights. Just imagine how much less accessible the world was only a few
decades ago, before travel became so commonplace.

Gad Perry
Texas Tech University, Lubbock

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IGUANA  •  VOLUME 13, NUMBER 2  •  JUNE 2006 147HISTORICAL PERSPECTIVE

“Draco volans is an accomplished glider. Ten flights ranged
from 4.5 to 12 meters, and averaged 8 meters in length. The dis-
tances were doubtless conditioned by the fact that coconut trees
are ordinarily planted 8–10 meters apart. Mertens (1930)
recorded flights of 15 to 20 meters, and no doubt longer ones are
possible, although a habitat in which such flights were necessary
would probably be unattractive to the species. In two observa-
tions the angle of the glide was estimated. For the first, the esti-
mate was between 200 and 300 degrees from horizontal; for the
second, the starting and ending heights were estimated as 6
meters and 3 meters, respectively, and the horizontal distance
measured 7.6 meters. Thus, the angle is close to 220 degrees, and
is in agreement with the more subjective first estimate. Draco
would therefore qualify for a gliding animal by the definition of
Oliver (1951), who distinguishes ‘gliding’ from ‘parachuting’
when the angle is greater than 450 degrees from vertical. The
flight appeared rather slow, as though being maintained at close
to the stalling point, an observation that agrees with the slight
amount of upturn at the end of the glide (see also Schmidt, 1935,
on D. spilopterus)” (Hairston, 1957, p. 262).

Finally, the recent experiments and observations by Klingel
are described. These, seemingly the first carefully controlled
experiments, are particularly interesting in that they corroborate
the field observations of Hairston, Herre, and Hendrickson.

To measure the distance of flights and their elapsed times,
Klingel erected vertical poles, 3.25 and 10 meters high, in an
open area, and placed targets, consisting of artificial trees, 20 cen-
timeters wide and 3 meters high, at varying distances from the
central poles. According to Klingel: “Usually the animals would
immediately run to the top of the pole and within a few minutes
would jump off spontaneously.” The length of each flight and the
height of the landing point on the target were measured. Some
of the flights were timed. In some cases the lizards did not fly to
the targets, and these targetless flights were also recorded.

In another set of experiments, to determine the control of
flight directions, Klingel used a room 4.25 meters square, painted
white, and lit by a centrally placed electric bulb. In the middle of
one wall was placed a black paper strip, 30 centimeters wide, to
serve as a target. The lizards were then thrown upward toward the
ceiling, beneath the light, and their flight directions and meth-
ods of controlling these directions were observed.

Klingel found that the flight pattern in Draco is clearly
divisible into three phases. The first phase is the dive flight, in
which the lizard launches itself from a tree. In this phase there is
a steep downward glide. The kinetic energy developed during
the dive flight is then utilized for the second phase of the flight
pattern, the glide flight, which can be quite extended. Finally,
the third phase of the flight pattern is the ascent flight, or land-
ing phase, in which the trajectory of the lizard rises from the
glide flight so that the animal swoops upward as it lands on the
target. Klingel recorded flights of as long as 60 meters for ani-
mals taking off from a 10-meter pole and flying toward a target.
In such flights there was a loss of altitude during the long glide
flight of as much as 2 meters, but some of this was recovered
during the upward landing. The recovery of altitude at landing
was not great, however, because of the slow speed of the glide
flight as it reached its end.

ANATOMY OF THE WING IN DRACO
Draco is an oriental lizard of the family Agamidae, ranging from
the Philippines, through the East Indies, to Indo-China and por-
tions of India. There are perhaps as many as 14 or 15 species of
Draco, varying in size from rather small or moderate-sized lizards,
with body weights in an adult of 5 or 6 grams, to the relative
giant, Draco maximus, in which the body weight may be as much
as 30 grams.

In these lizards there are five, six, or seven free and elongated
ribs on each side, for the support of the wing membranes.
Apparently the first of the elongated ribs belong to the eleventh
presacral vertebra and thus are situated well behind the pectoral
girdle, a position that gives the forelimbs complete freedom of
movement. The most posterior of the elongated ribs, whether
there be five, six, or seven on a side to support the wing mem-
brane, are likewise at some distance in front of the pelvic girdle,
again allowing for freedom of movement of the hind limbs. Each
membrane, however, has a free edge, extending from the tip of the
last supporting rib to a position just lateral to the cloaca. Thus the
posteromedial segments of the membranes are in part beneath the
upper segments of the hind legs, but this posterior attachment of
the membranes apparently does not limit the movements of the
hind limbs when the animal is walking or running.

In a normal resting or walking pose the wings are folded
back against the body. But when the animal launches itself into

Diagram to show the general arrangement of muscles and ligaments,
and their direction of force, in the wing of Draco.

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148 IGUANA  •  VOLUME 13, NUMBER 2  •  JUNE 2006 COLBERT

a glide, the wings are expanded to their full extent, making a large
gliding surface relative to the size and weight of the body.

WING AREA AND BODY WEIGHT
If wings for gliding are to be truly functional, they must be of
such size, as well as of such form, as to permit the animal to glide
through the air at a relatively low horizontal angle. As mentioned
above, Oliver defined gliding, as distinct from parachuting, as
descent at an angle greater than 45 degrees from the vertical (or,
conversely, less than 450 degrees from the horizontal). It is obvi-
ous from the descriptions of flight in this lizard that the condi-
tions for true gliding are fulfilled. Indeed, it appears that, if there
are any air currents, Draco is able to take advantage of them and
rise through the air during its forward flight. What are the rela-
tions of wing areas to body weight that make the rather astonish-
ing flights of Draco possible? How are the ratios of wing areas as
related to body weight to be compared with the same ratios in
birds of similar size? Careful measurements were made of the
wing areas in Draco, and for each specimen so measured the
weight was recorded. Several species of Draco were used, but the
present discussion is based largely on Draco whiteheadi, of which
a considerable series, consisting of 54 specimens ranging from
small individuals to full adults, was available. A single specimen
of Draco maximus, kindly lent to the author by Hendrickson, is
also included, because it is the giant among these lizards.

From a comparison of the weight of certain preserved lizards
with their live weight, as determined in the field, it was established
that the weight of the pickled animal should be, on the average,
about nine tenths of its live weight. Consequently, the weights of
the specimens as preserved were increased by a factor of one-tenth.
Each specimen was then placed on a board covered with paper,
with the wing on one side stretched to its maximum extent. As
can be seen from the figure, in the series of Draco whiteheadi the
wing area increases more or less directly as body weight increases,
but there is a great deal of individual variation in wing area as
related to body weight. It thus appears that there is no very cru-
cial weight- wing-area relationship among these animals, which is
to say that a lizard may have a wing area of almost a half less than
another individual of approximately the same weight, yet presum-
ably is nonetheless able to glide perfectly well. Perhaps many of
these animals have wing surface “to spare,” i.e., that they have
more wing than is absolutely required for their flights.

A comparison of Draco with birds shows that wing loadings
in the lizard are similar to those of the large soaring birds (the
hawks and vultures) rather than to those of the small birds that
approach Draco in size. The very low wing loading of Draco is
probably necessary to offset the relatively inefficient shape of the
wing. It is semicircular, as seen from above, not a conventional
transversely elongated wing like that in birds or airplanes. Thus
in effect it has no well-defined leading or trailing edges. Both of
these regions merge into what might be considered as the tip or
lateral edge of the wing, this constituting by far the largest part
of the border of the flying surface. It seems that the problem of
weight and wing area is rather different from that in birds; one
might expect solutions to this problem also to be different.

CONCLUSIONS
This study of Draco demonstrates that gliding, so efficiently per-
formed by the several species belonging to the genus, is simply

Weights, in grams, and corresponding wing areas, in square centimeters, of 54 individuals of Draco whiteheadi.

Outlines of the wings. A. Draco whiteheadi, A.M.N.H. No. 30905
(smallest individual). B. Draco whiteheadi, A.M.N.H. No. 30917
(largest individual). C. Draco maximus, John R. Hendrickson No. 5338.
D. Draco sp., newly hatched, John R. Hendrickson No. 2228. A and B
show the comparative wing areas in the smallest and largest individuals
available of one species. C shows the wing area of an individual of the
largest known species, and D shows that of an individual recently
hatched.

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IGUANA  •  VOLUME 13, NUMBER 2  •  JUNE 2006 149HISTORICAL PERSPECTIVE

effected. The spreading of the flight membrane, which is sup-
ported by five, six, or seven elongated ribs, is accomplished by the
use of a few muscles, particularly the iliocostalis and the inter-
costals, while the arching and the stiffening of the ribs are per-
formed by the very long, slender muscle slips that run along the
length of each rib. The wings in Draco, when expanded, provide
a flight surface that is very similar in relative extent, and thus of
wing loading, to that in the large soaring birds. Perhaps this sim-
ilarity is due to the fact that the lizards and the birds in question,
though quite dissimilar in size, have similar problems of aerody-
namics. The significance of the adaptation for gliding in Draco is
twofold. First, it represents the one example among modern rep-
tiles for aerial locomotion through considerable distances.

Second, although in itself perhaps comparatively recent in reptil-
ian evolution, it seems to represent the earliest type of aerial loco-
motion to be adopted by the vertebrates. Recent studies of fossil
lacertilians of Triassic age show adaptations for gliding that are
remarkably similar to those in Draco. Hence it is probable that
the first aerial vertebrates were reptiles equipped to glide from tree
to tree on expanded membranes supported by elongated ribs,
leaving all four limbs free for arboreal and terrestrial locomotion.
Apparently such adaptations for flight preceded by several mil-
lion years the first attempts at true flight, attained by the
pterosaurs. Thus, looking at Draco, we are, in effect, looking back
through some 200 million years, to view the manner in which
backboned animals first took to the air.

My grandfather, Edwin Harris (Ned) Colbert, had a long
and distinguished career in vertebrate paleontology. Much

of this was at the American Museum of Natural History
(AMNH) in New York, where he started as a graduate research
assistant, and wound up as Chairman of the Department of
Fossil Vertebrates. He made good use of the museum’s world-class
fossil collections and was involved in a number of great fossil dis-
coveries around the world. One of the most significant was the
late Triassic Ghost Ranch Quarry of New Mexico, where he
recovered multiple skeletons of the early dinosaur Coelophysis, a

discovery that profoundly influenced our understanding of early
dinosaur evolution. These global travels also took him on a pio-
neering trip to Antarctica, where his fossil finds supported emerg-
ing plate-tectonic theories. His outstanding publication record
includes more than 300 published papers and two textbooks. He
also wrote a number of popular books on dinosaurs (including a
few targeted at young readers), on plate tectonics, a biography,
and two autobiographies. In many ways, his legacy to the field of
paleontology was as much a consequence of his efforts at reach-
ing out to the general public, as was his scientific output. Rather
than summarize this remarkable career, I here attempt a more
intimate portrait using the excavation of Coelophysis at Ghost
Ranch as a vignette to better understand his life. 

When I knew him, my grandfather’s research focused on
Triassic terrestrial vertebrate faunas from around the world. This
research program incorporated newly emerging plate-tectonic
theories to explain the distribution of ancient faunas. You can
imagine my surprise to find that he wrote a couple of papers on
fossil tapirs, a group I now study and one that didn’t originate
until the Cenozoic! To compound the somewhat inbred feeling
that gave me, one of these papers actually reinterprets an earlier
tapir-paper by my namesake, great-grandfather William D.
Matthew, whose daughter my grandfather had married. Only
then did I come to realize the extent of grandfather’s work in the
middle to late Cenozoic, the study of which was the focus of his
Ph.D. dissertation and early career.

My earliest memories of my grandparents predate grandfa-
ther’s retirement from the AMNH in 1969. My family lived in

B I O G R A P H I C A L  S K E T C H

Ned Colbert in his office at the American Museum of Natural History,
ca. 1940s.

Remembrances of Edwin H. Colbert, Paleontologist
Matthew Colbert

University of Texas, Austin
(www.digimorph.org and www.ctlab.geo.utexas.edu)

Photographs courtesy of the author except where indicated.

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