Dinosaur Renaissance

DINOSAUR RENAISSANCE
The dinosaurs were not obsolescent reptiles
but were a novel group of "warm-blooded"
animals. And the birds are their descendants
by Robert T. Bakker
T
he dinosaur is for most people the
10 kilograms or more are endothermic
epitome of extinctness, the proto­
birds and mammals. Why?
type of an animal so maladapted
The term "cold-bloodedness" is a bit
to a changing environment that it dies
misleading: on a sunny day.a lizard's
out, leaving fossils but no descendants.
body temperature may be higher than a
Dinosaurs have a bad public image as
man's. The key distinction between ec­
symbols of obsolescence and hulking in­
tothermy and endothermy is the rate
efficiency; in political cartoons they are
of body-heat production and long-term
know-nothing conservatives that plod
temperature stability. The resting meta­
through miasmic swamps to inevitable
bolic heat production of living reptiles is
extinction. Most contemporary paleon­
too low to affect body temperature sig­
million years ago, confront one another in
HAIRY THERAPSIDS, mammal-like rep­
tiles of the late Permian period some 250
tologists have had little interest in dino­
nificantly in most situations, and reptiles
the snows o f southern Gondwanaland, at a
saurs; the creatures were an evolutionary
of today must use external heat sources
site that is now in South Africa. Anteosau-
novelty, to be sure, and some were very
to raise their body temperature above
big, but they did not appear to merit
the air temperature-which is why they
much serious study because they did not
bask in the sun or on warm rocks. Once
seem to go anywhere: no modern verte­
big lizards, big crocodiles or turtles in a
brate groups were descended from them.
warm climate achieve a high body tem­
Recent research is rewriting the dino­
perature they can maintain it for days
saur dossier. It appears that they were
because large size retards heat loss, but
more interesting creatures, better adapt­
they are still vulnerable to sudden heat
ed to a wide range of environments and
drain during cloudy weather or cool
immensely more sophisticated in their
nights or after a rainstorm, and so they
bioenergetic machinery than had been
cannot match the performance of endo­
thought. In this article I shall be present­
thermic birds and mammals.
ing some of the evidence that has led to
The key to avian and mammalian en­
reevaluation of the dinosaurs' role in ani­
dothermy is high basal metabolism: the
mal evolution. The evidence suggests, in
level of heat-producing chemical activ­
completely. One group still lives. We
in an endotherm than in an ectotherm of
fact, that the dinosaurs never died out
call them birds.
ity in each cell is about four times higher
the same weight at the same body tem­
perature. Additional heat is produced as
Ectothermy and Endothermy
Dinosaurs are usually portrayed as
it is needed, by shivering and some other
special forms of thermogenesis. Except
for some large tropical endotherms (ele­
"cold-blooded" animals, with a physiol­
phants and ostriches, for example), birds
ogy like that of living lizards or croco­
and mammals also have a layer of hair
diles. Modern land ecosystems clearly
or feathers that cuts the rate of thermal
show that in large animals "cold-blood­
loss. By adopting high heat production
edness" (ectothermy) is competitively in­
and insulation endotherms have pur­
ferior to "warm-bloodedness" (endother­
chased the ability to maintain more near­
my), the bioenergetic system of birds
ly constant high body temperatures than
and mammals. Small reptiles and am­
their ectothermic competitors can. A
phibians are common and diverse, par­
guarantee of high, constant body tem­
ticularly in the Tropics, but in nearly all
perature is a powerful adaptation be­
sues a gliding lizard across the sand dunes
habitats the overwhelming majority of
cause the rate of work output from mus­
of Rho desia in the early Jurassic period
land vertebrates with an adult weight of
cle tissue, heart and lungs is greater at
some 180 million years ago. This small dino·
58
© 1975 SCIENTIFIC AMERICAN, INC
FEATHERED DINOSAUR, Syntarsus, pur­
rus
(right), weighin g ahout 600 kilo grams, had bony rid ges on the
and the knowledge, from several kinds of data, that therapsids were
snout and brow for head·to·head contact in sexual or territorial
endothermic, or "warm.blooded"; those adapted to cold would
behavior. Pristerognathids (left ) weighed about 50 kilo grams and
have had hairy insulation. The advent of endothermy, competitive.
represent a group that included the direct ancestors of mammals.
ly superior to the ectothermy ("cold·bloodedness") of typical rep·
The reconstructions were made by the author on the basis of fossils
tiles, is the basis of author's new classification of land vertebrates.
saur ( adult weight about 30 kilo grams) and others were restored
cal similarities between dinosaurs and early birds. Dinosaurs, it ap­
by Michael Raath of the Queen Victoria Museum in Rhodesia and
pears, were endother"!ic, and the smaller species required insula.
the author on the basis of eviden ce that some thecodonts, ancestors
tion. Feathers would have conserved metabolic heat in cold environ·
of the dinosaurs, had insulation and on the basis of close anatomi·
ments and reflected the heat of the sun in hot climates such a s this.
59
© 1975 SCIENTIFIC AMERICAN, INC
i<E---MODERN MAMMALS---?> i
o
BIRDS
GREAT
NORTHERN
ICE AGE
16
25
0
(5
26
N
0
Z
W
0
�
Z
W
is
«
a:
<.?
W
a:
=>
50
�----- DINOSAURS-----?)i
�
r-_r---+--------------------�--�f_----------r_Tl--_r,_--,_----�,_�--�r_--t_--------ffi
�
75
::;;
W
�
o
a:
«
12
DINOSAUR
COMMUNITIES
20
00
=>
0
W
0
«
�
W
a:
0
100
(fj
«
W
a:
o
00
-'
«
::;;
::;;
«
::;;
0
125
0
<.?
«
00
a:
«
W
>u.. 150
0
00
z
0
::J
-'
3:
W
-'
o
�
<.?
Z
�
(5
MINIMUM
N
0
00
W
0
(5
LATITUDINAL
::;;
N
0
00
W
DINOSAUR
COMMUNITIES
::;;
TEMPERATURE
-'
-'
«
::;;
00
GRADIENT
0
(fj
00
«
a:
=>
....,
�
175
�
Z
W
Ci
«
a:
<.?
W
a:
=>
�
a:
r---+---------------------------------�------�----��._���-- --------------- ::;;
�
200
W
�
MIXED THERAPSID­
THECODONT COMMUNITIES
�
THECODONT
«
3:
W
-'
o
�
<.?
225
�-+��-+----------r--���-��--------��--�
w
THERAPSID
�
-'
i��tr7'",-�
--i---
COMMUNITIES
------------
z
«
250
�
o
(5
N
8
-'
275
a:
W
�
>­
-'
a:
«
W
ALL- ECTOTHERMIC
COMMUNITIES
«
W
a:
0
W
o
GREAT
GONDWANA
� r-L-+------r-��-ff-+�����--�--��ICE AGE
zOO
O=>
mO
a: a:
«W
o�
PREDATOR-PREY SYSTEMS of land vertebrates and the paths
groups named and pictured in the illustrations on pages 64 through
of descent of successive groups are diagrammed with the preda­
67_ The relative importance of the live biomass represented by
tors (color ) and the prey animals (gray) numbered to refer to the
fossils is indicated by the width of the gray and colored pathways.
60
© 1975 SCIENTIFIC AMERICAN, INC
high temperatures than at low tempera­
tures, and the endothermic animal's bio­
chemistry can be finely tuned to operate
within a narrow thermal range.
The adaptation carries a large bioen­
u
B
N
o
Z
w
U
CLASS
MAMMALIA
CLASS
AVES
CLASS
REPTILIA
ergetic price, however. The total energy
budget per year of a population of endo­
thermic birds or mammals is from 10 to
30 times higher than the energy budget
of an ectothermic population of the same
size and adult body weight. The price
is nonetheless justified. Mammals and
birds have been the dominant large and
medium-sized land vertebrates for 60
u
B
N
o
(f)
w
::;;
million years in nearly all habitats.
In view of the advantage of endother­
my the remarkable success of the dino­
saurs seems puzzling. The first land­
erous and early Permian periods, were
generally considered to be primitive and
ectothermic. Replacing this first ecto­
thermic dynasty were the mammal-like
d8
�i3
(f)
er
«
THERAPSIDA
vertebrate communities, in the Carbonif­
composed of reptiles and amphibians
I
:!
(f)er
(f)�
««
{
DINOSAURIA
--...-...
THECODONTIA
u
B
N
o
W
...J
«
"-
reptiles (therapsids), which eventually
produced the first true mammals near
the end of the next period, the Triassic,
USUAL CLASSIFICATION of land vertebrates ( excluding the Amphihia) is diagrammed
about when the dinosaurs were originat­
here in a highly simplified form. The classes are all descended from the original stem rep·
ing. One might expect that mammals
tiles. Birds ( class Aves) were considered descendants of early thecodonts, not of dinosaurs,
would have taken over the land-verte­
brate
communities
immediately,
but
and endothermy (color) was thought to have appeared gradually, late in the development
of mammals and birds. The author proposes a reclassification (see illustration on page 77).
they did not. From their appearance in
the Triassic until the end of the Creta­
ceous, a span of 140 million years, mam­
energy flow in ectotherms places little
those of the mid-Atlantic or East Africa.
mals remained small and inconspiCUOUS
demand on the bone compartment of the
Paleomagnetic data make it possible to
while all the ecological roles of large ter­
blood and calcium-phosphate system,
reconstruct the ancient positions of the
restrial herbivores and carnivores were
and so the compact bone of living rep­
continents to within about five degrees
monopolized by dinosaurs; mammals did
tiles has a characteristic "low activity"
of latitude, and sedimentary indicators
not begin to radiate and produce large
pattern: a low density of blood vessels
such as glacial beds and salt deposits
species until after the dinosaurs had al­
and few Haversian canals, which are
show the severity of the latitudinal tem­
ready become extinct at the end of the
the site of rapid calcium-phosphate ex­
perature gradient from the Equator to
the poles in past epochs. Given the lati­
Cretaceous. One is forced to conclude
change. Moreover, in strongly seasonal
that dinosaurs were competitively su­
climates, where drought or winter cold
tude and the gradient, one can plot tem­
perior to mammals as large land verte­
forces ectotherms to become dormant,
perature zones, and such zones should
brates. And that would be baffiing if
growth rings appear in the outer layers
separate endotherms from ectotherms.
dinosaurs were "cold-blooded." Perhaps
of compact bone, much like the rings in
Large reptiles with a lizardlike physiol­
they were not.
the wood of trees in similar environ­
ogy cannot survive cool winters because
Measuring Fossil Metabolism
In order to rethink traditional ideas
ments. The endothermic bone of birds
they cannot warm up to an optimal body.
and mammals is dramatically different.
temperature during the short winter day
It almost never shows growth rings, even
and they are too large to find safe hiding
in severe climates, and it is rich in blood
places for winter hibernation. That is
about Permian and Mesozoic vertebrates
vessels
Haversian
why small lizards are found today as far
one needs bioenergetic data for dino­
canals. Fossilization often faithfully pre­
north as Alberta, where they hibernate
saurs, therapsids and early mammals.
How does one measure a fossil animal's
metabolism? Surprising as it may seem,
recent research provides three indepen­
dent methods of extracting quantitative
metabolic information from the fossil
record. The first is bone histology. Bone
is an active tissue that contributes to the
formation of blood cells and participates
and frequently
in
serves the structure of bone, even in
underground during the winter,
specimens 300 million years old; thus it
crocodiles and big lizards do not get
provides one window through which to
much farther north than the northern
look back at the physiology of ancient
animals.
but
coast of the Gulf of Mexico.
The third meter of heat production in
The second analytic tool of paleobio­
extinct vertebrates is the predator-prey
energetics is latitudinal zonation. The
ratio: the relation of the "standing crop"
present continental masses have floated
of a predatory animal to that of its prey.
across the surface of the globe on litho­
The ratio is a constant that is a character­
in maintaining the calcium-phosphate
spheric rafts, sometimes colliding and
istic of the metabolism of the predator,
balance, vital to the proper functioning
pushing up mountain ranges, sometimes
regardless of the body size of the animals
of muscles and nerves. The low rate of
pulling apart along rift zones such as
of the predator-prey system. The reason-
61
© 1975 SCIENTIFIC AMERICAN, INC
Do
a:
u
c.!l
z
o
z 100
«
f0Ul
Ul
«
w
c.!l
a:
« 10
..J
Ul
«
Ul
w
�
f=
u.
o
a:
w
en
�
::::J
Z
w
::::J
..J
«
>
>c.!l
a:
w
z
w
ing is as follows: The energy budget of
an endothermic population is an order of
a
magnitude larger than that of an ecto­
thermic population of the same size and
adult weight, but the productivity-the
yield of prey tissue available to preda·
tors-is about the same for both an en­
b
dothermic and an ectothermic popula­
tion. In a steady-state population the
yearly gain in weight and energy value
from growth and reproduction equals
the weight and energy value of the car­
casses of the animals that die during the
year; the loss of biomass and energy
through death is balanced by additions.
The maximum energy value of all the
carcasses a steady-state population of
.1
lizards can provide its predators is about
the same as that provided by a prey
population of birds or mammals of about
the same numbers and adult body size,
1 KILOGRAM
1 METRIC TON
ADULT WEIGHT OF PREDATOR AND PREY
PREDATOR·PREY RATIO remain s about constant regardless of the size of the animals
involved because of the scaling relations in predator.prey energy flow. The yearly energy
bud get, or the amount of meat required per year per kilo gram o f predator, decreases with
increasing wei ght for endotherms (colored curve) and for ectotherms (solid black curve).
The energy value of carcasses provided per kilo gram by a prey population decreases with
increasin g weight at the same rate (broken black curve). The vertical lines are propor·
tional to the size of the prey "standin g crop" required to support one. unit of predator
Therefore a given prey population, ei­
ther ectotherms or endotherms, can sup­
port an order of magnitude greater bio·
mass of ectothermic predators than of
endothermic predators, because of the
endotherms' higher energy needs. The
term standing crop refers to the biomass,
01'
the energy value contained in the bio­
mass, of a population, In both ecto­
standing crop: about an order of magnitude greater for endothermic predators (color) than
therms and endotherms the energy value
for ectothermic ones (gray), whether for a lizard·size system (a) or a lion·size one (b).
of carcasses produced per unit of stand­
ing crop decreases with increasing adult
weight of prey animals:
a
herd of zebra
yields from about a fourth to a third of
b
a
PREY
its weight in prey carcasses a year, but a
C MAXIMUM
PREY
PREY
(ADULT
STANDING
CARCASSES
SUPPLIED
STANDING
PREDATOR
(ADULT
WEIGHT)
CROP
PER YEAR
CROP
WEIGHT)
SMALL
LIZARDS
50 GRAMS
MICE
50 GRAMS
PIGS,
DEER
100 TONS
100 TONS
100 TONS
100 KG.
ANTELOPE
100 KG,
100 TO NS
PREDATOR
1 1
8
8
--78---
--7
--7
--7
.ro TOO.
--7
---
--7
40 TONS
MOUNTAIN
BOOMER
LIZARD
100 GRAMS
"herd" of mice can produce up to six
times its weight because of its rapid turn­
over, reRected in a short life span and
high metabolism per unit weight.
Now, the energy budget per unit of
predator standing crop also decreases
with increasing weight:
lions require
more than 10 times their own weight in
meat per year, whereas shrews need 100
2 .5 TONS
WEASEL
100 GRAMS
times their weight. These two bioener­
getic scaling factors cancel each other,
so that if the adult size of the predator is
roughly the same as that of the prey (and
40 TONS
KOMODO
DRAGON
LIZARD
150 KG.
in land-vertebrate ecosystems it usually
is), the maximum ratio of predator stand­
ing crop to prey standing crop in a
steady-state community is a constant in­
dependent of the adult body size in the
predator-prey system [see top illustra­
2.5 TONS
LION
150 KG.
ENERGY FLOW and predator.prey relation are illustrated for predator.prey systems of
various sizes. Standing crop is the biomass of a population ( o r the potential energy value
c ontained in the tissue) averaged over a year. For a given adult size, ectothermic prey
(gray ) produce as much meat (b) per unit standing crop (a) as end otherms (color). En do·
thermic predators, however, require an order of ma gnitude more meat (b) per unit stand·
tion at left). For example, spiders are
ectotherms, and the ratio of a spider
population's standing crop to its prey
standing crop reaches a maximum of
about 40 percent. Mountain boomer liz­
ards, about 100 grams in adult weight,
feeding on other lizards would reach a
similar maximum ratio, So would the
giant Komodo dragon lizards (up to 150
in g crop (c). The maximum predator.prey biomass ratio (cia) is therefore about an
kilograms in body weight) preying on
order of magnitude greater in an endothermic system than it is in an ectothermic one.
deer, pigs and monkeys. Endothermic
62
© 1975 SCIENTIFIC AMERICAN, INC
mammals and birds, on the other hand,
thousands of individuals representing a
because they are the direct result of
reach a maximum predator-prey biomass
single community; their live body weight
predator metabolism.
ratio of only from 1 to 3 percent-wheth­
can be calculated from the reconstruc­
er they are weasel and mouse or lion
tion of complete skeletons, and the total
and zebra [see bottom illustration on op­
predator-prey biomass ratios are then
posite page].
Some fossil deposits yield hundreds or
•
HY.]
D
1::::::1
Vt.�1
easily worked out. Predator-prey ratios
are powerful tools for paleophysiology
The Age of Ectothermy
The paleobioenergetic methodology I
have outlined can be tested by analyzing
GLACIERS
EVAPORITE SEAS
•
MESOSAURUS
• FINBACKS
SHALLOW EPICONTINENTAL SEAS
ERODED MOU NTAINS
MOUNTAINS
• THERAPSIDS
•
CASEIDS, BIG CAPTORHINIDS
PERMIAN WORLD is reconstructed here (on an oblique Moll­
Gondwanaland was the little Mesosaurus, which apparently hiber­
weide projection, which minimizes distortion o f area) on the basis
nated in the mud during the winters. The late Permian world (bot­
of paleomagnetic and other geophysical data. All major land
tom) was less glaciated, but the south was still cold and the lati­
masses except China were welded into a supercontinent, Pangaea.
'
tudinal temperature gradient was still steep. Big reptiles with ecto­
In the early Permian (top) the Gondwana g laciation was at its
thermic b one, caseids and captorhinids, were restricted to the hot
maximum, covering much of the southern part of the continent.
Tropics, as large reptiles had been in the early Permian. By now,
Big finback pelycosaurs and contemporary large reptiles and am­
however, many early therapsids, all with endothermic bone and
phibians were confined to the Tropics; they had e ctothermic bone
low predator-prey ratios, had invaded southern Gondwanaland.
and high predator-prey ratios. The only reptile in cold southern
They must have acquired high heat production and some insulation.
.
© 1975 SCIENTIFIC AMERICAN, INC
63
the first land-vertebrate predator-prey
toonists. Although this family included
system, the early Permian communities
the direct ancestors of mammal-like rep­
canals and the distinct growth rings that
of primitive reptiles and amphibians.
tiles and hence of mammals, the sphenac­
are common in specimens from season­
The first predators capable of killing
odonts themselves had a very primitive
ally arid climates.
relatively large prey were the finback
level of organization, with a limb anat­
One might suspect that finbacks and
pelycosaurs of the family Sphenacodon­
omy less advanced than that of living
their prey would be confined to warm,
tidae, typified by Dimetrodon, whose
tall-spined fin makes it popular with cai-
lizards. Finback bone histology was em­
equable climates, and early Permian
phatically ectothermic, with a low den-
paleogeography offers an excellent op-
�
'''","ACODON '"
PREDA���:
0
�a:
en
en
«
::;; i='
0 Z
iii w
()
>- a:
w w
a:
Cl. �
ci:
0
I«
0
w
a:
Cl.
70
sity of blood vessels, few Haversian
�
�
:
I
4 PRISTEROGNATHIDS 50 KG
�
5 GORGONS 200 KG.
===========
=== =�
2 DIMETRODON 150 KG.
3 ANTEOSAURUS 500 KG.
�---------------- --------- FINBACKS ----------------------��� fE�------------------------ ---­
�----------------------- ECTOTHERMIC --------�). I
�(�-------------- ----------------
60
50
40
30
2
2
2
20
4
10
5
3
0
FORMATION
AGE
LO CATION
ADMIRAL
ABO
EARLY HERMIAN
EARLY PERMIAN
TEXAS
NEW MEXICO
BELLE PLAINS
EARLY PERMIAN
TEXAS
ARROYO
EARLY PERMIAN
TEXAS
3 DIADECTES 250 KG.
2 ERYOPS 175 KG.
3 KG.
N·T···········
�
-;;��
----
7 TAPINOCEPHALID
1 1 AULACEPHALODONT
........................................�
AND
200 KG.
6 STRUTHIOCEPHALID 1,000 KG.
5 TITANOSUCHUS 1,500 KG.
1 OPHIACODON 150 KG.
PREDATOR-PREY RATIO
�
ZAMBIA
8 MOSCHOPID 700 KG.
4 TRIMERORHACHIS 3 KG.
�
LATE PERMIAN
SOUTH AFRICA
9 SMAL
�
KISTE. ZONE
TAP. ZONE
LATE PERMIAN
PREY COMPOSITION
are
depositional environment. Tbe predator (top) and prey (bottom)
shown on these two pages and the next two pages for a number of
animals involved at each site are illustrated. For each deposit the
fossil communitie s, each repre senting a particular time zone and
histogram (color) gives the predator biomass as a percent of the
© 1975 SCIENTIFIC AMERICAN, INC
•
10 OUDENODONT 100 KG.
tudinal temperature gradient in the Per­
portunity to test this prediction. During
sian geologists [see illustration on page
the early part of the period ice caps cov­
63].
The Permian Equator crossed what
mian must have been at least as steep
ered the southern tips of the continen­
are now the American Southwest, the
as it is at present. Three Permian Horal
tal land masses, all of which were part
Maritime Provinces of Canada and west­
zones reHect the strong poleward tem­
of the single southern supercontinent
ern Europe. Here are found sediments
perature gradient. The Angaran Hora of
Gondwanaland, and glacial sediment is
produced in very hot climates: thick­
Siberia displays wood with growth rings
reported at the extreme northerly tip of
bedded evaporite salts and fully oxi­
from a wet environment, implying a
the Permian land mass in Siberia by Rus-
dized, red-stained mudstones. The lati-
moist climate with cold winters.
The
-----------------�
7 CYNODONT 80 KG.
�
8 ERYTHROSUCHID 300 KG.
6 MOSCHORHINIDS 20 KG.
----------------------- THERAPSIDS
-=�������====================== ====�
IE
________
________________________
____
ENDOT HERMIC
PREDATORS
THECODONTS
�
�====
=====:
BONE
==��
�I
�����
�
-.-----r--,---��--_r--�--�� 70
60
50
40
30
20
8
6
5
DAPT. ZONE
LATE PERMIAN
KISTE.-DAPT. ZONE
LATE PERMIAN
SOUTH AFRICA
SOUTH AFRICA
(ORANGE RIVER)
5
5
5
7
8
10
o
o
�a::
en
en
«
�
�
iIi w
>w
u
ffi
g: �
ct
o
!;(
o
w
a::
a..
DAPT. ZONE
ZONE IV
CYNOGN. ZONE
LATE PERMIAN
LATE PERMIAN
EARLY TRIASSIC
EARLY TRIASSIC
AGE
TANZANIA
WEST URALS
SOUTH AFRICA
SHANSI. CHINA
LOCATION
ER-MA-YING
FORMATION
"
�--�
12 DAPTOCEPHALID 300 KG.
12 DAPTOCEPHALID 300 KG.
11 AULACEPHALODONT 200 KG.
13 PAREIASAUR 1,000 KG.
14 CYNODONT 80 KG.
total prey biomass, in other words, the predator-prey ratio. The pie
charts give the composition of the available prey. Note the sud­
den drop in the predator-prey ratios during the transition from the
finback pelycosaurs to the early therapsids, which coincided with
the first appearance of endothermic bone and also with the inva·
sion of cold southern Gondwanaland by early therapsids of all sizes.
·6
5
© 1975 SCIENTIFIC AMERICAN, INC
Euramerian flora of the equatorial region
with wood from wet environments show­
had two plant associations: wet swamp
ing sharp growth rings.
The ectothermy of the finbacks is con­
communities with no growth rings in the
warm­
firmed by their geographic zonation.
moist growing season, and semiarid, red­
Finback communities are known only
wood,
implying a continuous
no
ing reptile, Mesosaurus, is known from
southern Gondwanaland, and its bone
has sharp growth rings. The animal must
have fed and reproduced during the
Gondwanaland summer and then bur­
bed-evaporite communities with some
from near the Permian Equator;
growth rings, reflecting a tropical dry
large early Permian land vertebrates of
season. In glaciated Gondwanaland the
hibernate, much as large snapping tur­
any kind are found in glaciated Gond­
peculiar Glossopteris flora dominated,
wanaland. (One peculiar little fish-eat-
tles do today in New England.)
rowed into the mud of lagoon bottoms to
Excellent samples of finback commu-
� 70
1
------�
1 0 3,0 0
12
-=Af
9 20
DEINONYCHID
_______
7600
5400
3200
100
COELOPHYSID
KG.
ALLOSAUR
KG.
PREDATORSI �(�------ DINOSAURS
BONE �----------------------------------------------------- ENDOTHERMIC
0
i=
<{
a:
Cf)
Cf)
<{
::;;
0
co
>w
a:
o..
ri:
0
t<{
0
i=='
z
w
U
a:
w
e:-
w
a:
0..
KG.
TYRANNOSAUR
2,0 0
KG.
--------­
10
9
9
---
12
1
10
FORMATION
LUFENG
KUEPER
MORRISON
TENDAGURU
AGE
LATE TRIASSIC
LATE TRIASSIC
LATE JURASSIC
LATE JURASSIC
EARLY CRETACEOUS
LOCATION
CHINA
EUROPE
AMERICAN WEST
EAST AFRICA
AMERICAN WEST
17
15
PROSAUROPOD
1,50
KG.
CAMARASAUR
1
9
25,0 0
KG.
16 17,0 0
DIPLOCID
BRACHIOSAUR
KG.
40,0 0
CLOVERLY
OLD MAN
LATE CRETACEOUS
ALBERTA
KG.
21
20
ANKYLOSAUR
ORNITHOPOD
2,0 0
2,0 0
KG.
KG.
EVIDENCE FROM FOSSIL COMMUNITIES is continued from
to the same scale ; their adult weights are given. The drawings are
the preceding two pages. The animals are of course not all drawn
presented with the same limb·stride positions in each to emphasize
66
© 1975 SCIENTIFIC AMERICAN, INC
nities are available for predator-prey
gether in a sediment representing one
respect to the body in the prey and the
studies, thanks largely to the lifework
particular environment. In working with
predator and should give a ratio that
of the late Alfred Sherwood Romer of
scattered and disarticulated skeletons it
faithfully represents the ratio of the ani­
Harvard University. In order to derive a
is best to count only bones that have
mals in life.
predator-prey ratio from a fossil commu­
about the same robustness, and hence
In the earlier early Permian zones the
nity one simply calculates the number
the same preservability, in both predator
most important finback prey were semi­
of individuals, and thus the total live
and prey. The humerus and the femur
aquatic fish-eating amphibians and rep­
weight, represented by all the predator
are good choices for finback communi­
tiles, particularly the big-headed am­
and prey specimens that are found to-
ties: they are about the same size with
phibian Eryops and the long-snouted
�
15 MESONYCHID100 KG.
�
14 MIACID20 KG.
�
� 1(\
1__-
-
16 CATS, DOGS 10-200 KG.
� ---
13 CREDONT 10-200 KG.
-------
DINOSAURS
-------o)� lf<;-<---
-
-
----------------
-
-
----
MAMMALS
1
:
--71 PREDATORS
---------
ENDOT H ERMIC -
�>
--------------------
BONE
---,--r--1r--.- 70
-r60
50
0
0
0
0
�==�==�==��==���==�����=1�==���==�� 0
4
3
2
12
12
LOWER EDMONTON A, LOWER EDMONTON B
14
13
12
15
16
1
13
16
o
i=
«
a:
en
en
«
�
�
10 m
>w
a:
()
a:
W
a.�
ci:
�
o
W
a:
a.
FORMATI ON
LANCE-HELL CREEK
WASATCH
CHADRON
HARRISON
LATE CRETACEOUS
LATE CRETACEOUS
LATE CRETACEOUS
EOCENE
OLIGOCENE
PLIOCENE
AGE
ALBERTA
ALBERTA
AMERICAN WEST
SOUTH DAKOTA
NEBRASKA
LOCATION
AMERICAN WEST
MW
26 ARTIODACTYL 10-1 ,000 KG
25 CONDYLARTH1-100 KG.
24 PERRISODACTYL 10-1,000 KG.
23 CORYPHODON400 KG.
relative limb length. Long.limbed, fast'sprinting vertebrates of
Note the remarkably low predator.prey ratios of the dinosaur� , as
large size appeared only with the dinosaurs, in the middle Triassic.
low as or lower than those of the Cenozoic ( and modern) mammals.
67
© 1975 SCIENTIFIC AMERICAN, INC
pelycosaur Ophiacodon. As the climate
became more arid in Europe and Ameri­
ca these water-linked forms decreased in
numbers, and the fully terrestrial herbi­
vore Diadectes became the chief prey
genus. In all zones from all environments
the calculated biomass ratio of predator
to prey in finback communities is very
high: from 35 to 60 percent, the same
range seen in living ectothermic spiders
and lizards.
All three of the paleobioenergetic in
dicators agree: the finback pelycosaurs
and their contemporaries were ecto­
therms with low heat production and a
lizardlike physiology that confined their
distribution to the Tropics.
Therapsid Communities
The
mammal-like
reptiles
Therapsida), descendants of
(order
the
fin­
backs, made their debut at the transition
from the early to the late Permian and
immediately became the dominant large
land vertebrates all over the world. The
three metabolism-measuring techniques
show that they were endotherms.
LONGISQUAMA, a small animal whose fossil was discovered in middle Triassic lake beds
in Turkestan by the Russian paleontologist A. Sharov, was a thecodont. Its body was cov·
ered by long overlapping scales that were keeled, suggesting that they constituted a struc·
tural stage in the evolution of feathers. The long devices along the back were V.shaped in
cross section ; they may have served as parachutes and also as threat devices, as shown here.
The earliest therapsids retained many
finback characteristics but had acquired
limb adaptations that made possible a
trotting gait and much higher running
speeds. From early late Permian to the
middle Triassic one line of therapsids
became increasingly like primitive mam­
mals in all details of the skull, the teeth
and the limbs, so that some of the very
advanced mammal-like therapsids (cyn­
odonts) are difficult to separate from
the first true mammals. The change in
physiology, however, was not so gradual.
Detailed studies of bone histology con­
ducted by Armand Riqles of the Univer­
sity of Paris indicate that the bioener­
getic transition was sudden and early:
all the finbacks had fully ectothermic
bone; all the early therapsids-and there
is an eXb'aordinary variety of them-had
fully endothermic bone, with no growth
rings and with closely packed blood ves­
sels and Haversian canals.
The late Permian world still had a
severe latitudinal temperature gradient;
some glaciation continued in Tasmania,
and the southern end of Gondwanaland
retained its cold-adapted Glossopteris
flora.
If the earliest therapsids were
equipped with endothermy, they would
presumably have been able to invade
southern Africa, South America and the
other parts of the southern cold-tempera­
SORDUS PILOSUS, also found by Sharov, was a pterosaur: a fiying reptile of the Jurassic
ture realm. They did exactly that. A rich
diversity of early therapsid families has
p eriod that was a descendant of the co donts or of very early dinosaurs. Superbly preserved
fossils show that the animal was insulated with a dense growth of hair or hair like feathers ;
been found in the southern Cape District
hence the name, which means "hairy devil." Insulation strongly suggests endothermy.
of South Africa, in Rhodesia, in Brazil
68
© 1975 SCIENTIFIC AMERICAN, INC
and in India-regions reaching to 65 de­
mian finback communities. Equally low
Such ratios indicate that the therapsids
grees south Permian latitude [see illus­
ratios are found for tropical therapsids
achieved endothermy with a moderately
tration on page 63]. Early therapsids
from the U.S.S.R. even though the prey
high heat production, far higher than in
as large as rhinoceroses were common
species there were totally different from
typical reptiles but still lower than in
there, and many species grew to an adult
those of Africa. The sudden decrease in
most modern mammals. Predator-prey
predator-prey ratios from finbacks to
ratios of early Cenozoic communities
early therapsids coincides exactly with
seem to be lower than those of therap­
weight greater than 10 kilograms, too
large for true hibernation. These early
therapsids must have had phYSiological
adaptations that enabled them to feed in
and move through the snows of the cold
Gondwanaland winters. There were also
some ectothermic holdovers from the
early Permian that survived into the late
Permian, notably the immense herbivo­
rous caseid pelycosaurs and the big­
headed, seed-eating captorhinids. As one
might predict, large species of these two
ectothermic families were confined to
the sudden change in bone histology
sids, and so one might conclude that a
from ectothermic to endothermic report­
further increase in metabolism occurred
ed by Riqles and also with the sudden
somewhere between the advanced the­
invasion of the southern cold-temperate
rapsids of the Triassic and the mammals
zone by a rich therapsid fauna. The con­
of the post-Cretaceous era. Therapsids
clusion is unavoidable that even early
may have operated at a lower body tem­
therapsids were endotherms with high
perature than most living mammals do,
heat production.
and thus they may have saved energy
It seems certain, moreover, that in the
with a lower thermostat setting. This
cold Gondwanaland winters the therap­
suggestion is reinforced by the low body
sids would have required surface insula­
temperature of the most primitive living
tion. Hair is usually thought of as a late
mammals:
caseids and captorhinids are not found
development that first appeared in the
spiny anteater) and the insectivorous
with the therapsids in cold Gondwana­
advanced therapsids, but it must have
tenrecs of Madagascar; they maintain a
land. In the late Permian, then, there
been present in the southern African en­
temperature of about 30 degrees Celsius
areas near the late Permian Equator; big
monotremes
(such
as
the
was a "modern" faunal zonation of large
dotherms of the early late Permian. How
instead of the 36 to 39 degrees of most
vertebrates, with endothermic therap­
did hair originate? Possibly the ancestors
modern mammals.
sids and some big ectotherms in the
of therapsids had touch-sensitive hairs
TropiGs giving way to an all-endothermic
scattered over the body as adaptations
therapsid fauna in the cold south.
In the ea�liest therapsid communities
for
could then have favored increased den­
The vigorous and successful therapsid
of southern Africa, superbly represented
sity of hair as the animals' heat produc­
dynasty ruled until the middle of the
night
foraging;
natural
selection
Thecodont Transition
in collections built up by Lieuwe Boon­
tion increased and they moved into cold­
Triassic. Then their fortunes waned and
stra of the South African Museum and
er climates.
a new group, which was later to include
by James Kitching of the University of
The therapsid predator-prey ratios, al­
the dinosaurs, began to take over the
the Witwatersrand, the predator-prey
though much lower than those of ecto­
roles of large predators and herbivores.
ratios are between 9 ·and 16 percent.
therms, are still about three times higher
These were the Archosauria, and the
That is much lower than in early Per-
than those of advanced mammals today.
first wave of archosaurs were the the-
ARCHAEOPTERYX, generally considered the first bird, is known
and could not fly. The presence of insulation in the thecodont
from late Jurassic fossils that show its feather covering clearly. In
Longisquama and in Sordus and Archaeopteryx, which were de­
spite of its very birdlike appearance, Archaeopteryx was closely
scendants of thecodonts, indicates that insulation and endothermy
related to certain small dinosaurs (see illustration on next page)
were acquired very early, probably in early Triassic theco donts.
69
© 1975 SCIENTIFIC AMERICAN, INC
codonts. The earliest thecodonts, small
dence is clearer. World climate was
and medium-sized animals found in the­
moderating in the Triassic (the glaciers
the Jurassic with the first bird, Archae­
rapsid communities during the Permian­
were gone), but a distinctive flora and
Triassic transition, had an ectothermic
some wood growth rings suggest that
bone histology. In modern ecosystems
opteryx. The likelihood that some the­
codonts had insulation is supported,
however, by another of Sharov's dis­
southern Gondwanaland was not yet
the role played by large freshwater pred­
coveries: a pterosa
' ur, or flying reptile,
warm all year. What is significant in this
ators seems to be one in which ecto­
whose fossils in Jurassic lake beds still
regard is the distribution of phytosaurs,
thermy is competitively superior to en­
show the epidermal covering. This beast
the big ectothermic fish-eating theco­
dothermy; the low metabolic rate of
(appropriately named Sordus pilosus, the
donts. Their fossils are common in North
ectotherms may be a key advantage be­
"hairy devil") had a dense growth of hair
America and Europe (in the Triassic
cause it allows much longer dives. Two
or hairlike feathers all over its body and
Tropics)
limbs.
groups of thecodonts became large fresh­
warmed by the equatorial Tethys Ocean,
Triassic thecodonts or perhaps of very
water fish-eaters: the phytosaurs, which
but they have not been found in south­
primitive dinosaurs. The insulation in
were confined to the Triassic, and the
ern Gondwanaland, in southern Africa
both Sordus and Longisquama, and the
crocodilians, which remain successful to­
or in Argentina, even though a rich
presence of big erythrosuchid thecodonts
day. Both groups have ectothermic bone.
endothermic thecodont fauna did exist
at the southern limits of Gondwanaland,
(The crocodilian endothermy was either
there.
strongly suggest that some endothermic
inherited directly from the first theco­
and
in
India,
which
was
Did some of the thecodonts have ther­
donts or derived secondarily from endo­
mal insulation? Direct evidence comes
thermic intermediate ancestors.) In most
from the discoveries of A. Sharov of the
Pterosaurs
are descendants of
thecodonts had acquired insulation by
the early Triassic.
of the later, fully terrestrial advanced
Academy of Sciences of the U.S.S.R.
thecodonts, on the other hand, Riqles
Sharov found a partial skeleton of a small
discovered a typical endothermic bone
thecodont and named it Longisquama
Di{lOsaurs, descendants of early the­
histology; the later thecodonts were ap­
for its long scales: strange parachutelike
codonts, appeared first in the middle
parently endothermic.
devices along the back that may have
Triassic and by the end of the period
served to break the animal's fall when it
had replaced thecodonts and the remain­
codonts is scanty. The ratios are hard to
leaped from trees. More important is the
ing therapsids as the dominant terrestrial
compute because big carnivorous cyn­
covering of long, overlapping, keeled
vertebrates. Zonal evidence for endo­
odonts and even early dinosaurs usually
scales that trapped an insulating layer of
thermy in dinosaurs is somewhat equivo­
shared the predatory role with theco­
air next to its body [see top illustration
cal. The Jurassic was a time of climatic
The predator-prey evidence for the­
The Dinosaurs
donts. One sample from China that has
on page 68]. These scales lacked the
only one large predator genus, a big­
complex anatomy of real feathers, but
ture gradient was the gentlest that has
headed erythrosuchid thecodont, does
they are a perfect ancestral stage for the
prevailed from the Permian until the
optimum, when the poleward tempera­
give a ratio of about 10 percent, which is
insulation of birds. Feathers are usually
present day. In the succeeding Creta­
in the endothermic range. The zonal evi-
assumed to have appeared only late in
ceous period latitudinal zoning of ocean-
DINOSAURIAN ANCESTRY of Archaeopteryx (left), and thus of
Ostrom of Yale University demon strated that they were virtually
birds, is indicated by its close anatomical relation to such small
identical in all details of joint anatomy. The long forelimbs of
dinosaurs as Microvenator (right )
Archaeopteryx were probably used for capturing prey, not for flight.
and Deinonychus;
John H.
70
© 1975 SCIENTIFIC AMERICAN, INC
ic plankton and land plants seems, how-
a
ever, to have been a bit sharper. Rhinoc­
eros-sized Cretaceous dinosaurs and big
marine lizards are found in the rocks of
the Canadian far north, within the Cre­
taceous Arctic Circle. Dale A. Russell of
the National Museums of Canada points
out that at these latitudes the sun would
have been below the horizon for months
at a time. The environment of the dino­
saurs would have been far severer than
the environment of the marine reptiles
b
because of the lack of a wind-chill factor
in the water and because of the ocean's
temperature-buffering effect. Moreover,
locomotion costs far less energy per kilo­
meter in water than on land, so that
the marine reptiles could have migrated
away from the arctic winter. These con­
siderations suggest, but do not prove,
that arctic dinosaurs must have been
able to cope with cold stress.
Dinosaur bone histology is less equivocal. All dinosaur species that have been
investigated
show
fully
endothermic
bone, some with a blood-vessel density
higher than that in living mammals.
Since bone histology separates endo­
therms from ectotherms in the Permian
and the Triassic, this evidence alone
should be a strong argument for the en­
dothermy of dinosaurs. Yet the predatorprey ratios are even more compelling.
Dinosaur carnivore fossils are exceeding­
ly rare. The predator-prey ratios for di­
c
nosaur communities in the Triassic, Ju­
rassic and Cretaceous are usually from 1
to 3 percent, far lower even than those
of therapsids and fully as low as those
in large samples of fossils from advanced
mammal communities in the Cenozoic. I
am persuaded that all the available
quantitative evidence is in favor of high
heat production and a large annual energy budget in dinosaurs.
Were dinosaurs insulated? Explicit
evidence comes from a surprising source:
d
Archaeopteryx. As an undergraduate a
decade ago I was a member of a paleon­
tological field party led by John H. Ostrom of Yale University. Near Bridger,
Mont., Ostrom found a remarkably pre­
served little dinosaurian carnivore, D ei­
nonychus, that shed a great deal of light
on carnivorous dinosaurs in general. A
few years later, while looking for pterosaur fossils in European museums, Ostrom came on a specimen of Archae­
opteryx that had been mislabeled for
years as a flying reptile, and he noticed
extraordinary points of resemblance be­
tween Archaeopteryx and carnivorous
dinosaurs. After a detailed anatomical
analysis Ostrom has now established
beyond any reasonable doubt that the
LIMB LENGTHS of dinosaurs are compared with those of two ecologically equivalent
therapsids. The limbs were relatively longer in the dinosaurs and the appended muscles
were larger, indicating that the dinosaurs had a larger capacity for high levels of exercise
metabolism. The two top drawings represent the animals as if they were the same wei ght ;
the adult carnivorous therap sid Cynognathus (a ) actually weighed 100 kilo grams and
the juvenile dinosaur Albertosaurus (b ) 600 kilo grams. Two herbivores, therapsid Stru·
thiocephalus (c ) and horned dinosaur Centrosaurus (d ) , weighed ahout 1,500 kilo grams.
71
© 1975 SCIENTIFIC AMERICAN, INC
immediate ancestor of Archaeopteryx
joints appeared during the Cretaceous,
the proper functioning o f a complex
must have been a small dinosaur, per­
long after Archaeopteryx.
cenb·al nervous system calls for the guar­
haps one related to Deinonychus. Pre­
It has been suggested a number of
viously it had been thought that the
times that dinosaurs could have achieved
ancestor of Archaeopteryx, and thus of
a fairly constant body temperature in a
birds, was a thecodont rather far re­
warm environment by sheer bulk alone;
moved from dinosaurs themselves.
large alligators approach this condition
Therapsids had small brains with rep­
in the swamps of the U. S. Gulf states.
tilian organization; not until the Ceno­
Archaeopteryx was quite thoroughly
proposed
thermal
antee of a constant body temperature. It
is not surprising that endothermy ap­
peared before brain enlargement in the
evolutionary line leadi�g to mammals.
feathered, and yet it probably could not
This
mechanism
zoic did mammals attain the large brain
fly: the shoulder joints were identical
would not give rise to endothermic bone
size characteristic of most modern spe­
with those of carnivorous dinosaurs and
histology or low predator-prey ratios,
cies. A large brain is certainly not neces­
were adapted for grasping prey, not for
however, nor would it explain arctic di­
sary for endothermy, since the physio­
the peculiar arc of movement needed for
nosaurs or the success of many small
logical feedback mechanisms responsible
wing-flapping. The feathers were prob­
dinosaur species with an adult weight of
for thermoregulation are deep within the
ably adaptations not for powered flight
between five and 50 kilograms.
"old" region of the brain, not in the high­
er learning centers. Most large dinosaurs
or gliding but primarily for insulation.
Archaeopteryx is so nearly identical in
Dinosaur Brains and Limbs
all known features with small carnivo­
rous dinosaurs that it is hard to believe
Large
brain size and
endothermy
did have relatively small brains. Russell
has shown, however, that some small
and medium-sized carnivorous dinosaurs
feathers were not present in such dino­
seem to be linked; most birds and mam­
had brains as large as or larger than
saurs. Birds inherited their high meta­
mals have a ratio of brain size to body
modern birds of the same body size.
bolic rate and most probably their feath­
size much larger than that of living rep­
Up to this point I have concentrated
ered insulation from dinosaurs; powered
tiles and amphibians. The acquisition of
on thermoregulatory heat production.
Bight probably did not evolve until the
endothermy is probably a prerequisite
Metabolism during exercise can also be
first birds with flight-adapted shoulder
for the enlargement of the brain because
read from fossils. Short bursts of intense
exercise are powered by anaerobic me­
tabolism within muscles, and the oxygen
debt incurred is paid back afterward by
BONE
PRESENT IN
PREDATOR-
LIMB
HISTOLOGY
TEMPERATE ZONE
PREY RATIO
LENGTH
50 PE RCENT
NO
SHORT
LAND VERTEBRATES
oxygen debt much faster. Apparently
this difference does not keep small ecto­
top running speeds of small lizards equal
NO
NOT APP L I C A B LE
SHORT
CAPTORHINIDS
or exceed those of small mammals. The
difficulty of repaying oxygen debt in­
creases with increasing body size, how­
ever, and the living large reptiles (croco­
LATE PERMIANEARL Y TRIASSIC
levels of maximum aerobic metabolism
thermic animals from moving fast: the
LATE PERMIAN
CASEIDS AND B IG
Most modern
than living reptiles and can repay an
FINBACKS. OTHER
EARLY PERMIAN
the heart-lung system.
birds and mammals have much higher
10 PERCENT
YES
SHORT
THERAPSIDS
dilians, giant lizards and turtles) have
noticeably shorter limbs, less limb mus­
culature and lower top speeds than many
large mammals, such as the big cats and
EARLIEST
THECODONTS
?
?
SHORT
the hoofed herbivores.
The early Permian ectothermic dy­
nasty was also strikingly short-limbed;
MOST LAND
THECODONTS
FRESHWATER
THECODONTS
YES
UP TO 600
10 PERCENT
SHORT
KILOGRAMS
NO
UP TO 500
KILOGRAMS
evidently the physiological capacity for
high sprinting speeds in large animals
had not yet evolved. Even the late the­
rapsids, including the most advanced
?
SHORT
cynodonts, had very short limbs com­
pared with the modern-looking running
mammals that appeared early in the
DINOSAURS
YES
1-3 PERCENT
LONG
Cenozoic. Large dinosaurs, on the other
hand, resembled modern running mam­
mals, not therapsids, in locomotor anat­
omy and limb proportions. Modern, fast­
CENOZOIC
MAMMALS
YES
1-5 PERCENT
LONG
running mammals utilize an anatomical
trick that adds
:m
extra limb segment to
the forelimb stroke. The scapula, or
PALEOB I O ENERGETIC EVIDEN C E is summed up here. The appro priate blocks are
shaded to show whether the available data constitute evid ence for e ctothermy (gray ) or
shoulder blade, which is relatively im­
mobile in most primitive vertebrates, is
endothermy (color) accordin g to criteria discussed in the text of this article. Caseids and
free to swing backward and forward and
captorhinids are herbivores, so that there is no predator-prey ratio. There are early theco­
thus incr0ase the sb·ide length. Jane A.
donts in temperate-zone depo sits, but they are small and so the evidence is not significant.
Peterson of Harvard has shown that
72
© 1975 SCIENTIFIC AMERICAN, INC
Al u m i n u m ta kes the
beati n g . Not you .
For 20 years Alcoa has been
developing aluminum highway prod­
ucts to help save l i ves and tax doll ars.
Products l ike alumi num light poles,
signs, sign stru ctures and bridge
raili ngs are well suited to the rigors of
our nation's h i ghways. Because they
require a m i n imum of maintenance.
B e c a use they can save l i ves.
t h e re a re seco n d a ry p l u s e s . T h ey ' re
Co n s i d e r the s p u n a l u m i n u m l i g h t
n a n ce a l u m i n u m p ro d u cts h e l p
l i g h t , d u ra b l e and easy to h an d l e a n d
m a i n t a i n . I n a d d i t i o n , t h e re i s a l u m i ­
n u m ' s h i g h s c ra p v a l u e a n d i t s a b i l i ty
to be recyc l e d at t h e b a rg a i n rate of
f i v e p e r c e n t of t h e e n e rg y o r i g i n a l l y
req u i red to p rod u c e t h e m o l te n metal
f r o m t h e o re .
N o w o n d e r recy c l a b l e , l ow - m a i n te­
p o l e s h ow n a b o v e . I t ' s d e s i g n e d to
red u c e t h e cost of h i g hway
b re a k c l ean o n i m pact-not stop
yo u r car dead. Hit o n e a n d t h e p o l e
m a i n te n a n c e .
I f y o u w o u l d l i ke m o r e i n f o r m a t i o n o n
b re a k s a w a y at t h e b a s e , f l i ps i n t o
recy c l a b l e a l u m i n u m , w r i t e f o r o u r
t h e a i r a n d f a l l s h a r m l es s l y b e h i n d
b ro c h u re s . W e ' re A l u m i n u m C o m .
t h e c a r . A l t h o u g h safety a n d
pany of A m e r i c a , 986 - D A l c o a
pe rfo r m a n c e a re p r i m a ry co n s i d e ra­
t i o n s w i t h h i g hway p ro d u cts,
B u i l d i n g , P i tt s b u rg h , PA 1 52 1 9 .
,
The reasons for using a l u m i n u m
a r e found i n a l u m i n u m i tself.
m ALCOA
© 1975 SCIENTIFIC AMERICAN, INC
© 1975 SCIENTIFIC AMERICAN, INC
©197 5 Pol a roid Corporation
Pola roid® SX-70"
Now you can get
h eavenly close-ups liI"e this,
on the spot.
With the SX:70.
A l l you need i s a te le scope a n d
te l e s co pe eyepiece, you a re a s s u red
ti o n s of e x ce l l e n t q u a l i ty ca n be
a C e l e stron Te l e s cope Ada pter for
that your ph otog ra ph w i l l i n c l u d e
obta i n ed .
the P o l a roid SX-70 La nd Ca mera .
the entire viewing fie l d .
A n d you ca n ph otog ra ph the moo n ,
Fi n a l l y, beca u s e a stro-photogra­
T i m e e x p o s u re s of u p to 1 4 s e c­
s u n a n d p l a n ets ( n ot t o mention
o n d s a re l o n g e n o u g h for a l most
such e a rt h b o u n d s u bj e cts as a
a l l p l a n etary photo g ra p h y.
p h y is s u s ce pt i b l e to s o m a n y
p ro b l e m s ( s u c h a s a t m o s p h e r i c
cha n g e s a nd te l e s cope v i b ra ti o n s )
m o u n ta i n goat on a n i n acce s s i b l e
SX-70 L a n d fi l m d e l i vers h i g h l y
i t ' s e s pe ci a l ly co mforti n g t o be a b l e
cra g , o r t h e orna me ntati o n o n a
a ccu rate co l o r reprod u ction u nd e r
t o s e e your ph otog ra ph on t h e s pot.
b u i l d i n g 3 m i l e s a wa y ) .
a w i d e va ri ety o f a t m o s p h e r i c a nd
If s o m et h i n g has g o n e wron g , you
With the a d a pte r, you can atta ch
e x p o s u re co n d i t i o n s . ( O n e s o l a r
ca n re-shoot to correct it. I n stead of
s i m p l y m oo n i n g a bout.
the SX-70 to a l most any te l e scope.
a u t h o r i ty ca l l s i t " t h e m o s t t r u e
T h i s p r o v i d e s a n u m b e r of a d v a n ­
r e n d i t i o n of t h e h y d r o g e n - a l p h a
For fu l l data on the C e l estron
ta g e s ,
color t h a t I ha ve y e t to s e e : ' ) A n d
Te l e s c o p e A d a pte r for the S X - 7 0 ,
pa rti c u l a r l y f o r
a m a te u r
a stro n o mers:
With o u r s i n g l e- l e n s reflex a s the
beca use t h e fi l m ha s v i rtu a l l y n o
write t o C e l e stron P a cific, 283 5A
g ra i n , e n l a rg e m e nts a n d reprod u c-
C o l u m b i a St. , To rra n ce , C a l . 9050 3 .
Another use for the Polaroid
5X-70
t o a ll1ws t an.l}
telescope.
© 1975 SCIENTIFIC AMERICAN, INC
Camera.
FUELING THE FUTURE
O
nly yesterday, space flight challenged the world of
technology to new heights of achievement. Now, the
twin problems of energy and environment challenge the
growth, even the survival of society. But quick solutions
can create more problems than they solve. That's why so
many different options are being so carefully examined.
TRW, for example, has multidisciplinary teams work­
ing with government, labor, and industry on conservation
studies and pollution control as well as on specific energy
development projects.
We're working on advanced electric batteries for load
leveling in power plants and for vehicle propulsion . . .
designing solar energy systems for heating and cooling
buildings and dehydrating fruits and vegetables . . . and
developing geothermal and shale oil technology as well
as investigating the use of ocean thermal gradients to
produce power.
Our new smokestack scrubber uses charged water
droplets to remove more than 90 % of the particles from
flue gases. Smaller and less costly than conventional
scrubbers, it has no moving parts, so it's silent and vibra­
tionless. It's a direct offshoot from our spacecraft attitude
control technology.
Another group has developed a special burner for oil or
gas-fired furnaces. It reduces emissions of nitrogen oxides
and costs no more than conventional burners.
Yet another team is now ready for pilot-plant tests of
a simple, low-cost system for removing pyritic sulphur
from coal. It is expected to make some 3 0 % of the Appa­
lachian reserves clean enough to meet EPA standards.
The total energy problem, however, is the most chal­
lenging of all. It requires objective trade-offs between
supply, conversion, and distribution capabilities and the
varying parameters of demand. Of real value here is the
fact that our people are not directly involved in the pro­
duction of fuels. This frees them to ask the kind of basic
questions that are essential to obj ective analysis.
Our work in space technology, which may seem irrele­
vant to energy problems, also turns out to be useful.
Among other things, it has given us a lot of experience
in using very little energy with maximum efficiency.
Our most recent interplanetary probe, for example, has
JUSt enough power to light an ordinary desk lamp; yet
it warms components in temperatur�s far below zero . . .
energizes a whole complex of sensing, recording, and
computing systems . . . and transmits streams of pictures
and other data over distances as great as half a billion
miles.
Admittedly, that's not the same as powering a city but
it does induce a miserly attitude. That helps in a practical
way : What we've learned about handling miIliwatts effi­
ciently is surprisingly useful when you're trying to get
more megawatts out of increasingly precious fuel supplies.
If you are interested in using TRW's capabilities in
any of these areas, we invite you to write and tell us
about your specific needs.
TRW.
SYSTEMS GROUP
Attention : Marketing Communications, E2 /9043
One Space Park, Redondo Beach, California 902 78
© 1975 SCIENTIFIC AMERICAN, INC
also
to diversify until after all the dinosaur
cal events decrease the variety of habi­
evolved scapular swinging, although its
groups (except birds ! ) had disappeared.
tats that are available to land animals,
details are different from those in mam­
Some geochemical and microfossil evi­
and thus increase competition. They can
mals. Quadrupedal dinosaurs evolved a
dence suggests a moderate drop in ocean
also cause the collapse of intricate, high­
chameleon-type scapula, and they must
temperature at the transition from the
ly evolved ecosystems; the larger ani­
have
running
Cretaceous to the Cenozoic, and so cold
mals seem to be the more affected. At the
speeds comparable to those of big savan­
na mammals today.
has been suggested as the reason. But
end of the Permian similar changes had
the very groups that would have been
been accompanied by catastrophic ex­
When the dinosaurs fell at the end of
most sensitive to cold, the large croco­
tinctions among therapsids and other
the Cretaceous, they were not a senile,
dilians, are found as far north as Sas­
land groups. Now, at the end of the
living chameleonid lizards have
had long strides
and
moribund group that had played out its
katchewan and as far south as Argentina
Cretaceous, it was the dinosaurs that
evolutionary options. Rather they were
before and immediately after the end of
suffered a catastrophe; the mammals and
vigorous, still diversifying into new or­
the Cretaceous. A more likely reason is
birds, perhaps because they were so
ders and prodUcing a variety of big­
the draining of shallow seas on the con­
much smaller, found places for them­
highest
tinents and a lull in mountain-building
selves in the changing landscape and
grade of intelligence yet present on land.
activity in most parts of the world, which
survived.
What caused their fall? It was not com­
would have produced vast stretches of
The success of the dinosaurs, an enig­
petition, because mammals did not begin
monotonous topography. Such geologi-
ma as long as they were considered
brained carnivores
with
the
B IRDS
u
z
o
o
o
z
w
I
n.
CIl
SUB CLASS
MAMMALIA
6
N
o
Z
w
U
SUBCLASS
DINOS AURIA
«
o
u
6
N
o
CIl
w
::;;
Ui
n.
o
ex:
w
I
I­
CIl
CIl
«
...J
u
S UBCLAS S
TH ERAPS IDA
u
2
o
W
...J
«
n.
RECLASSIFICATION of land vertebrates
( excluding the Am·
tiles. Birds almost certainly inherited their bioenergetics (as well
phibia) is suggested by the author on the basis o f bioenergetic and
as their j oint anatomy ) from dinosaurs. The new classes presented
anatomical evidence. The critical break comes with the develop.
here, the Theropsida and the Archo sauria, reflect energetic evolu·
ment of endothermy ( color) , which is competitively superior to
tion more faithfully than the traditional groupings (see illustration
ectothermy (gray) for large land vertebrates. Therapsids were en·
on
dothermic, closer in physi ology to mammals than to to day's rep·
groups is proportional to the biomass represented by their fossils.
page
61 ) . The width of the pathways representing the various
.
© 1975 SCIENTIFIC AMERICAN, INC
77
"cold-blooded," can now be seen as the
predictable result of the superiority of
their high heat production, high aero­
bic exercise metabolism and insulation.
They were endotherms. Yet the concept
of dinosaurs as ectotherms is deeply en­
trenched in a century of paleontological
literature. Being a reptile connotes being
an ectotherm, and the dinosaurs have
always been classified in the subclass
Archosauria of the class Reptilia; the
other land-vertebrate classes were the
Mammalia and the Aves. Perhaps, then,
it is time to reclassify.
Replica of double-manual harpsichord by Pascal
Taskin ( 1 769). Range FF-g"', 2 x S', I x 4' ,
manual coupler, buff stop, optional
peau de buffle
Taxonomic Conclusion
register. Ebony and IVOry keyboards with unbushed
rack-guided levers. A single-manual kit is also
available.
HARPSICHORD
& FORTEPIANO
KITS
THE FINEST AVAILABLE
INSTRUMENTS
IN KIT FORM
What better dividing line than the in­
vention of endothermy? There has been
Replica of Viennese fortepiano by J . A. Stein
( 1 784). Range FF-f"', double-strung throughout,
Viennese acnon with escapement. E bony and ivory
keyboard with unbushed rear-guided levers.
All ki ts supply pre-cut and fitted parts, complete
no more far-reaching adaptive break­
through, and so the transition from ecto­
thermy to endothermy can serve to sep­
arate the land vertebrates into higher
materials and supplies. special tools, detailed
taxonomic categories. For some time it
instructions and drawings on Mylar. The instru­
has been suggested that the therapsids
ments are also available in assembled form
requiring only decoration and installation of
musical parts.
should be removed from the Reptilia and
jOined with the Mammalia; in the light
of the sudden increase in heat produc­
tion and the probable presence of hair
For an illustrated brochure write:
FRANK HU BBARD, Harpsichord Maker
I S5A-S Lyman SI.
Waltham, Mass. 02154
in early therapsids, I fully agree. The
term Theropsida has been applied to
mammals and their therapsid ancestors.
Let us establish a new class Theropsida,
with therapsids and true mammals as
two subclasses { see illustration on pre­
ceding page].
How about the class Aves? All the
quantitative data from bone histology
and predator-prey ratios, as well as the
dinosaurian nature of Archaeopteryx,
show that all the essentials of avian bi­
ology-very high heat production, very
high aerobic exercise metabolism and
feathery insulation-were present in the
dinosaur ancestors of birds. I do not be­
lieve birds deserve to be put in a taxo­
nomic class separate from dinosaurs.
Peter Galton of the University of Bridge­
.port and I have suggested a more rea­
sonable classification: putting the birds
into the Dinosauria. Since bone histol­
ogy suggests that most thecodonts were
endothermic, the thecodonts could then
be joined with the Dinosauria in a great
endothermic class Archosauria, compa­
rable to the Theropsida. The classifica­
tion may seem radical at first, but it is
actually a good deal neater bioenergeti­
cally than the traditional Reptilia, Aves
and Mammalia. And for those of us who
are fond of dinosaurs the new classifica­
tion has a particularly happy implica­
tion: The dinosaurs are not extinct. The
colorful and successful diversity of the
living birds is a continuing expression of
basic dinosaur biology.
78
© 1975 SCIENTIFIC AMERICAN, INC
CheckbOOk
with a brain
Never make another che ckbook error
with America 's firs t computerized
banking center in a case. '
--�
.c _-�.--::-
_____,..._
...
_�___�!:IIi .
The new Corvus Check Master is a checkbook holder
with a built-in computer-a time-sa ving device tha t
will keep y o u in perfect balance for every check y o u write, every day o f the year.
Y O U R BAN K W I L L L O V E YOU
I f y o u ' re l i k e m o st A m er i c a n s , y o u r
chec k b o o k i s a d i sa ster a rea . A n d you r
e l ectro n i c ca l c u l a tor i s n ' t h e l p i n g m u c h .
N ow, t h e r e ' s a great n e w space-age
prod u c t ca l l ed t h e C o rvu s C h ec k M a ster
des i g n ed spec i f i ca l l y to keep you i n
perfect b a l a nce, f o r every check you
write, every d a y of t h e year. A n d i t ' s
actu a l l y e a s i e r to u se tha n a ca l c u l a t o r .
5.
Safety switch I f you forget to t u r n off y o u r
6.
Priv ate viewing a n g l e D o n 't worry a bo u t
co mputer, d o n ' t w o r r y . W h e never you cl ose
your case, your u n it shuts off automat ica l l y .
a n y o n e see i n g your b a l a nce. T h e r e d d i sp l a y
ca n o n l y be v i ewed by the u s e r a n d regi sters
up to $9,999.99 o r any six d i g i t s .
7. Perfect size The Check M a ster 's h a n d so m e
ta n a n d cream-co l o red c a s e measu res 7 / 8 " x 3
5/8" x 6 3/4" a n d weighs o n l y 8 ou nces.
H E R E 'S HOW I T WOR KS
Open y o u r checkbook h o l der a n d
turn o n t h e b u i l t- i n c o m p u t e r . Press
the " B a l a nce" key, and you r ba n k
ba l a nce i s reca l l ed o n the d i sp l a y . The
Check M a ster memory i s so powerfu l
that it n ever forgets y o u r b a l a nce­
even m o n t h s after you l a st reca l l it.
E nter the a m o u n t of your check,
a n d p ress the " C h ec k " key. The check
amount i s automatica l l y deducted
fro m y o u r ba l a nce, and your new
ba l a nce i s d i s p l a yed-and a l l with j u st
one key stro k e .
M A N Y EXTRA F E ATU R ES
1.
NATIONAL
I NTRODUCTO R Y
PRice
The C h ec k M a ster is perfect i n s u r a n ce
aga i n st bou nced c h ecks, overdrafts, a r i t h m e t i c
errors a n d b a n k e r r o r s . I ts powerf u l memory,
si m p l e o pera t i o n , a n d m a n y extra features
make it a nother exa m p l e of how space-age
tec h n o l ogy h a s made fu n out of o n e of the
most t i m e-consu m i ng h o u seho l d tasks.
MO R E THAN G U A R A N T E E D
T h e Corv u s C h e c k M aster wi l l m a k e such a n
i m provement i n h e l p i n g y o u ba l a nce y o u r
checkbook that w e m a k e the fo l l ow i n g u n ­
u s u a l mo ney-back g u a ra n t e e : u se the C h eck·
M a ster u n t i l y o u r next b a n k statement a r r i ves
or for one fu l l m o n t h . If the C h ec k M a ster
does not ba l a nce your checkbook perfec t l y
and actu a l l y pay f o r itse l f i n e i t h e r conven­
ience o r actu a l sav i n gs, ret u r n it for a pro m pt
and cou rteo u s ref u n d . You ca n 't lose.
A NAT I O N A L I N T R O D U C TO R Y P R I C E
O r e n t e r the a mo u n t of a deposit,
a n d press t h e " D eposit" key. Y o u r
deposit i s a u t o m a t i ca l l y added to y o u r
ba l a nce, a n d aga i n , y o u r new ba l a nce
is d i sp l a yed.
The Corvu s C h e c k M a ster does so
m u c h , so easi l y , a n d it's great f u n to
use. H e re are seven reaso n s wh y :
$3995
To find out your exact balance, even months after
you 've last recalled it, simply open your case and
press the balance key. Check Master's memory never
T h e A m e r i c a n - m a d e C h eck M a ster i s m a n ­
ufactu red by C o r v u s , a wh o l l y-owned subsid­
iary of M o stek Corpora t i o n a nd a lead i ng
co nsu mer e l ectro n i cs m a n u facturer. M o stek
was t h e f i rst co m p a n y to m a n ufacture the
i ntegrated c i rcu it-the heart of today's pocket
ca lcu l ator. JS&A i s the wo r l d ' s l a rgest s i n g l e
so u rce o f e l ectro n ic c a l c u l ators, d i g i ta l watch­
es and other space-age products. W e have
purchased the entire i n i t i a l C h ec k M a ster prod·
uct i o n to se l l exc l u sively through the mail for
only $39 . 9 5 d u r i n g its n a t i o n a l i n t r o d u ct i o n .
HOW TO ORDER
Cred i t card bu yers m a y order b y ca l l i n g o u r
I f you
forgets. Designed for both men and women, Check·
nat i o n a l to l l -free n u m ber o r a n y of the local
enter t h e wro n g d i g its, press the
Master holds any standard-sized personal checks,
check register, credit cards and important papers.
n u m bers l i sted b e l o w . O r you m a y send y o u r
" C l ea r " key . O n l y you r m i stake wi l l
L--' c h e c k o r money order for $42.45 per u n i t
be c l ea red - n ever the b a l a nce.
($39 . 9 5 p l u s $ 2 . 50 postage, i n s u rance a n d
R U G G E D A N D S H OC K P ROO F
.2. Worry-free dec i m a l J u st enter the d i g i t s .
The u n i t ' s d o l l a r-position d ec i m a l a l ways
Drop i t , s i t on i t , d r o p it aga i n - C h ec k M a st­ h a nd l i n g- I l l i no i s residents a d d 5% sa l es t a x )
keeps the d ec i m a l p o i n t where it b e l o ngs.
er's shock-proof case w i l l w i t h stand p l enty of to the a d d ress s h o w n b e l o w . B u t a c t q u i c k l y !
abuse. The i ntegrated c i r c u i t i s hermetica l l y See for yourself how easy it is t o keep y o u r
sea led for a l i fet i m e o f trou b l e-free serv i c e . A c h e c k b o o k i n perfect b a l a nce every day of the
spot of g o l d is even u sed in t h e c i rc u i t ' s f i n a l yea r . Order y o u r Check M a ster at no o b l i sea l i n g process t o i n sure Check M a ster's very gat i o n today.
Easily
corrects
m i stakes
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
ONE Y E A R WA R R A N T Y
high l evel of rel i a b i l i t y .
CON T R O L Y O U R P U R C H ASES
3.
Low battery signal The u n it's pen l i ght
batter i es will l a st o n e year with average u se. A
low battery s i g n a l on the d i sp l a y w i l l i n d i cate
when it's time to replace t h e m .
4,
Overdraft a lert Check M a ster wi I I s i g n a l a n
overd rawn acco u n t p l u s s h o w the overdraft
a m o u n t and h e l p you avo i d the e m ba rrass­
ment of havi ng a check acc i d e n ta l l y bounce.
Take CheckM aster w i t h you to the super­
market. Set a d o l l a r l i m i t o n what you intend
to b u y , Then enter each item you pu rchase as
if you were w r i t i n g a check. When y o u r
ba l a nce r e a c h e s y o u r l i m i t , s t o p b u y i ng a n d
h e a d for t h e check-o u t counter. I t's a great
way to control your b u d get and prevent
overc h a rg i n g by the c h eck-out c l e r k .
T H E P E R F ECT G I FT
C h eck M a ster makes the i de al g i f t for y o u r
wife, h u s ba n d , f r i e n d or a n ybody who has a
perso n a l check i n g acco u n t . Even a person
who a l ready owns a ca l c u l ator wi l l appreciate
Check M a ster's value a n d conve n i ence.
CA L L T O L L - F R E E . . . . . . . . . . . . . . . . . . .
In the State o f Illinois call . . . . . . . . . .
In
In
In
In
In
( 800) 323-6400
(3 12) 498-6900
the San F rancisco a rea ca l l . . . . . ( 4 1 5 ) 39 1 - 1 700
the N ew York C i ty area ca l l . . . ( 2 1 2 ) 964-0690
Mo ntreal Canada ca l l . . . . . . . . . . . . . . ( 5 1 4 ) 332-9523
Toronto Canada ca l l . . . . . . . . . . . . . . . ( 4 1 6 ) 445-8 1 36
Austra l ia ca l l . . . . . . . . . . . . . . . . . . . . M e l bourne 53 5286
I � (0), ANfJIONAL
��L�6up
4200 D U N D E E R O A D
N O R T H B R O O K , I L L I N O I S 60062
D E PT. SCA- 9
( 3 1 2 ) 564-9000 © J S & A Group, I nc . , 1 97 5
79
© 1975 SCIENTIFIC AMERICAN, INC