5. A long, forward-jutting prong on the ilium.
6. A hip socket formed as a wide hole between the three hip
bones.
7. A birdlike hinge in the ankle, where two small ankle bones
were firmly fused onto the lower ends of the shank (the joint here
was formed between the two ankle bones and the lower part of
the ankle).
8. A breast bone (sternum) divided into two parts that lay side
by side.
All these observations constituted a fair case for Anchisaurus
as a missing link. Peter Galton and I were feeling proud of our
fledgling heresy until we did some reading in the old monographs
that dated from before 1920. Most of the characteristics we had
recognized had already been identified by the earlier scholars. And
Thomas Henry Huxley had made nearly as good an argument for
the naturalness of the Dinosauria as a single group in 1880. Some-
how all of this was simply forgotten after 1930.
There remained one nagging difficulty that obstructed our ar-
gument for the dinosaurs as a single group: All of the anchisaurs
and all of the primitive meat-eating dinosaurs possessed that very
distinctive twist-thumb, but not one of the ornithischians had it.
Ornithischian thumbs were usually short and terminated in a blunt
hoof, not a curved claw. To clinch our theory, an ornithischian with
a twist-thumb that ended in a claw was indispensable. And what
happened next was nearly a miracle of serendipity.
The miraculous find took the form of Fuzz Crompton's fanged
ornithischian. Fuzz—the nickname derived from his days in South
Africa, when his bushy hair made him a standout in that socially
DINOSAURS HAVE CLASS I 455
Recent discoveries suggest that the archosaur family tree was complex, with
many basal branches. On this chart, some key evolutionary developments are
shown marking the major splitting points. Straight-ankle hinge lines seem to
mark the true Dinosauria, and double breastbones (sterna) mark the plant-
eating dinosaurs.
conservative atmosphere—Crompton was director of the museum
at Harvard. He had excavated a fine three-foot-long ornithischian
from the Early Jurassic beds of Lesotho. This fossil caused quite a
stir—it was the finest specimen from such an early geological age.
The animal was primitive in many ways, and—most striking of all
its features—it had fangs, large, sharp teeth arranged in pairs in
the front of its mouth. Most ornithischians were herbivores, so
possessed no dangerous biting teeth. Crompton's fanged ornithis-
456 I DYNASTIC FRAILTY AND THE PULSES OF ANIMAL HISTORY
chian therefore presented a nice puzzle. What precisely had it used
those fangs for?
What was absolutely riveting about this ornithischian, how-
ever, was its hand: the fingers were all long, not stubby like those
of other primitive ornithischians, and the thumb possessed a wicked
claw mounted on a twisted bone. There could be no doubt that
here was the missing link Peter Galton and I had concluded we
needed. This animal proved that the Order Ornithischia was the
sister group of the Order Saurischia. Anchisaurus and Crompton's
fanged ornithischian taken together made the argument. Anchi-
saurus was a saurischian leaning forward toward the Ornithischia,
while Crompton's beast was an ornithischian leaning backward
toward the Saurischia. The two dinosaurs were very close cousins,
and they proved that the Dinosauria were a natural group.
Excited by our conclusion, Peter Galton and I rushed off a
paper to the British journal Nature, announcing the resurrection
of the Dinosauria as a legitimate scientific term. This marked the
first time in half a century that anyone had made a serious case for
their naturalness. All hell broke loose. We expected debate, dis-
cussion, dissent—and we certainly got it. But as good fortune would
have it, shortly after Galton and I had published our piece, the
brilliant Argentine paleontologist Jose Bonaparte published his work
on the lineage of the dinosaurs—work that Galton and I had no
knowledge of until that moment. Bonaparte was similarly unaware
of our work, but he had arrived at the very same conclusions we
had: The dinosaurs were a natural group and the Ornithischia had
evolved from an anchisaurlike ancestor. Bonaparte argued that the
earliest ancestor of all dinosaurs had been something like Lagosu-
chus, the tiny bunny-croc of the Mid Triassic. In fact, except for a
few details, Jose Bonaparte's description of the dinosaurs' family
tree was nearly identical to ours. And the fine nature of his work
was a powerful support for this conception of the dinosaur's evo-
lution.
While Peter Galton and I were at it, we also went one step
further in our resurrection of the Dinosauria. We made them un-
extinct. We accomplished this by a simple rearrangement of the
formal scientific nomenclature. We placed the birds into the Di-
nosauria. And if birds are members of the Dinosauria, then the
dinosaurs are not extinct.
DINOSAURS HAVE CLASS | 457
John Ostrom had proved that birds were direct descendants
of small, advanced carnivorous dinosaurs. Traditional classification
placed the birds in their own Class Aves and the dinosaurs in the
Class Reptilia, because birds were feathered, warm-blooded fliers
with advanced hearts and lungs, whereas dinosaurs were scaly-
skinned, cold-blooded beasts with only limited capacity for vigor.
But we were convinced the birds had inherited their heart-lung
system and their warm-bloodedness from dinosaurs. Of course,
dinosaurs hadn't flown. But the small, predatory dinosaurs had all
the necessary adaptive prerequisites for evolving into flight. And
feathers of some sort may well have insulated the body of some
theropod dinosaurs. It might even appear that birds owed most of
their distinctive adaptations to their dinosaur ancestors. Birds might
never have evolved flight if their dinosaur forebears had not
undergone a long history of evolutionary transformation into ever
more active, fast-moving, warm-blooded predators. It was neither
fair nor accurate to deny the dinosaurs credit for evolving into birds.
It was therefore only proper to demote the Class Aves to a sub-
division of the Class Dinosauria (or Class Archosauria with dino-
saurs as a subclass).
The notion of birds as dinosaurs gave conservative zoologists
yet another issue over which to protest. And after a lecture on the
topic I delivered in Philadelphia, a woman arose to ask whether
this meant her parakeet was dangerous! Some large dinosaurs ob-
viously were most unbirdlike, Diplodocus or Triceratops, for ex-
ample. But the bipedal predators were very avian in structure. And
the small, advanced predators like Deinonychus were so close to
Archaeopteryx in nearly every detail that Archaeopteryx might be
called a flying Deinonychus, and Deinonychus a flightless Archaeop-
teryx. There simply was no great anatomical gulf separating birds
/>
from dinosaurs. And that implies dinosaurs are not extinct. One
great, advanced clan of them still survives in today's ecosystem and
the more than eight thousand species of modern bird are an elo-
quent testimony to the success in aerial form of the dinosaurs'
heritage.
Finally, I suggest the standard terminology applied to dino-
saurs stands in need of radical reorganization. Most popular books
about dinosaurs today employ the traditional classification and di-
vide them into Saurischia and Ornithischia. But the distinction im-
plied by this nomenclature is misleading, if not obfuscatory.
458 | DYNASTIC FRAILTY AND THE PULSES OF ANIMAL HISTORY
Traditionally, herbivorous dinosaurs are not placed into one nat-
ural group, they are separated into two "orders"—the anchisaurs
and brontosaurs are put into the Saurischia, and all the beaked di-
nosaurs into the Ornithischia. This separation is damaging because
it obscures the fact that beaked dinosaurs are close relatives of an-
chisaurs. The ornithischians descended from anchisaurlike sauris-
chians, just as the brontosaurs trace from a close relative of
Anchisaurus. Therefore all the plant-eating dinosaurs of every sort
really constitute one, single natural group branching out from one
ancestor, a primitive anchisaurlike dinosaur. And a new name is
required for this grand family of vegetarians. So I hereby christen
them the Phytodinosauria, the "plant dinosaurs."
Of course, all the carnivores are also descended from a com-
mon ancestor that first evolved that birdlike hind foot—three toes
to the front and one turned backward and inward. These meat-
eaters already enjoy a good name, the theropods. Now, birds should
be placed in as a subdivision of the Theropoda.
There are some very primitive, very early carnivorous dino-
saurs from the Triassic that are presently hard to define. They had
not yet evolved the birdlike foot or the expanded hip bone (iliac
blade) found in all other predatory dinosaurs. Until these archaic
creatures are better known, they can informally be left as a group
of ancient uncles of the theropods.
At the very base of this system for classifying dinosaurs must
be placed Lagosuchus, the bunny-croc, and its kind. And this raises
another interesting wrinkle. Pterodactyls were most probably the
evolutionary products of Lagosuchus or a very similar animal. They
too are traditionally assigned their own order, the Order Ptero-
sauria, but this arrangement obscures the very close relationship
between early pterodactyls and early dinosaurs. It would be far
clearer to make the Pterosauria a subdivision of the Dinosauria as
well.
At the broadest level, then, how would this resurrected Class
Dinosauria fit into the overall classification of land vertebrates? This
is an important question and care must be taken. If the Dinosauria
were to be located in the Class Reptilia, irretrievable damage would
be done; once again, the dinosaurs would be subjected to more
guilt by association—arguments that dinosaurs were cold-blooded
because reptiles are, and so on. No, definitely not, the Dinosauria
are not Reptilia Vera. And while we are at it, those uncles of the
DINOSAURS HAVE CLASS I 459
The Dinosaurian Family Tree:
Each figure represents a family.
dinosaurs, the crimson crocodiles, should also be taken out of the
Class Reptilia. Most of them had all the basic adaptations of warm-
bloodedness—fast growth, fast evolution, low predator-to-prey ra-
tios (though not as low as the dinosaurs'). What I am proposing,
then, is that we should remove the entire Archosauria from the
Reptilia. (The same ought to be done for our own ancestors, the
protomammals of the Late Permian and the Triassic. These fel-
lows are usually left in the Order Therapsida in the Class Reptilia.
They don't belong there. Even the earliest Kazanian therapsids
displayed the telltale signs of warm-bloodedness in their bone
structure and predator ratios.)
I proposed this sort of classification in 1975 in an article I
published in Scientific American. Most taxonomists, however, have
viewed such new terminology as dangerously destabilizing to the
traditional and well-known scheme that has been with us since the
time of Baron Cuvier. I cannot see any benefit to be gained by
refusing to remove the dinosaurs (and the therapsids) from the
confines of the Reptilia. Classification is a type of scientific defi-
nition, and definitions should help express our perceptions of na-
ture, not hinder them. As long as textbooks and museum labels
unreflectively repeat the message. "Dinosaurs are reptiles," it will
be difficult to establish an intelligent debate about the true nature
of the dinosaurs' adaptations. Some of the orthodox paleontolo-
gists act as though the dinosaurs must be assumed cold-blooded
until their warm-bloodedness is proved beyond any reasonable
doubt. That is at least highly unscientific. And it certainly repre-
sents "argument by definition"—dinosaurs are reptiles, reptiles are
cold-blooded, therefore dinosaurs were cold-blooded.
A truly scientific skeptic would start by assuming neither cold-
bloodedness nor warm-bloodedness, and then reevaluate the evi-
dence without prior terminological bias. So long as the Dinosauria
remain stuck in the Class Reptilia, this type of analysis is nearly
impossible. Let dinosaurs be dinosaurs. Let the Dinosauria stand
proudly alone, a Class by itself. They merit it. And let us squarely
face the dinosaurness of birds and the birdness of the Dinosauria.
When the Canada geese honk their way northward, we can say:
"The dinosaurs are migrating, it must be spring!"
462 | DYNASTIC FRAILTY AND THE PULSES OF ANIMAL HISTORY
NOTES AND REFERENCES
The literature on dinosaurs and other fossil vertebrates is a sprawling mass of short and long
contributions, with many of the short technical papers being excellent but written in inac-
cessible jargon and many of the popular summaries being dreary repetitions of the "cold-
blooded musheater in the swamps" myths. So I have listed here the best overall summaries
that have good bibliographies, plus some of the old gems that have been forgotten, plus
some key papers on important aspects of physiology and ecology.
GENERAL REFERENCES
The two milestone volumes are: 1) the A A A S Select Symposium 28, Westview Press, 1 9 8 0
(ALMOST out of print—call the publisher so they will add another printing); and 2) the
Los Angeles County Museum of Natural History Special Colloquium Dinosaurs Past and
Present, LACM Press (1986). Nearly every important paper about warm-bloodedness, pro
and con, are cited in these two volumes. The difference in tone between the two is remark-
able. The 1980 A A A S book was unapologetically skeptical—even the title Cold Look at the
Warm-Blooded Dinosaurs suggested that belief in warm-blooded Dinosauria was rash and be-
yond the boundaries of level-headed science. But the LACM volume contains articles by
> those who reconstruct dinosaurs and their world, and, with few exceptions, the artists, anat-
omists, and paleontologists accord the dinosaurs a much, much higher level of locomotor
energetics than was widely believed six years ago. Sylvia Czerkas, the editor and organizer
of the LACM colloquium, said to me after the conference, "You must be feeling pretty
good, seeing your ideas vindicated more and more." Maybe so. At least the general attitude
is shifting away from the view that dinosaurs must be assumed to be cold-blooded in all
points and any contrary evidence dismissed with a "harrumph."
Czerkas, Sylvia, ed., Dinosaurs Past and Present, Los Angeles County Museum Special Sym-
posium (Los Angeles: LACM Press, 1986).
Thomas, Roger D. K. and Everett C. Olson, eds., A Cold Look at the Warm-Blooded Dino-
saurs, A A A S Selected Symposium 28 (Boulder, Colo.: Westview Press, 1980).
Wilford, John Noble, The Riddle of the Dinosaur (New York: Alfred A. Knopf, 1985).
1. BRONTOSAURUS IN THE GREAT HALL AT YALE
Notes:
I use Brontosaurus not Apatosaurus even though, according to the International Code of Zoological Nomenclature, the latter is the legal name. Al Romer used to complain that "rules
463
of nomenclature should serve the cause of science, not the other way round." The same man—Yale's Professor Marsh—coined both Apatosaurus and Brontosaurus; the former name is just a bit older, but the latter is much, much better known by the public at large. Science
should take every opportunity to divest itself of unnecessary obscurantism, and so I will use
Brontosaurus. The type specimen (the specimen used first to define the genus) of Brontosaurus is the wonderfully complete skeleton mounted at Yale, and I'm sure that Marsh's ghost
won't mind a bit when I use Brontosaurus in preference to Apatosaurus. The nomenclatural Law of Priority—the rule that says the legal name is the oldest name based on an adequate
type specimen—was originally developed to honor the first discoverer of a species or genus
and to stabilize the system of names. Using Brontosaurus honors Marsh, who discovered the
genus, and certainly reduces confusion and instability when scientists communicate to the
public.
Speaking of genera . . . it's common practice to talk about dinosaurs and other extinct
vertebrates in the generic sense, not in the specific. Most popular and technical articles speak
of Triceratops and Allosaurus and do not identify the species—for example, Triceratops hor-ridus or Allosaurus fragilis. That's like talking about all the dog species together in one lump—
Robert T Bakker Page 47
