278 Evolution? The Fossils Say YES!
the creationists, who attack one tiny detail of the subject without addressing all the rest of
the evidence.
New discoveries have further reinforced the point that theropod dinosaurs were bird-
like not only in their anatomy but also in their behavior. In the 1990s, expeditions from the
American Museum of Natural History to the Gobi Desert in Mongolia made some remark-
able discoveries, including nests of eggs of the dinosaur Oviraptor. These eggs were so com-
mon in Mongolia that the original American Museum expeditions in the 1920s had attributed
them to the most common dinosaur of these beds, the primitive horned Protoceratops
(fig. 12.7). When bones of a small theropod were found near some nests, they were given the
name Oviraptor (“egg thief”). But the recent expeditions show that this name is slanderous:
Oviraptor wasn’t stealing the eggs—it was their mother! In some cases, the female Oviraptor
skeleton was entombed in brooding posture right on top of the eggs as they were both buried
in a sandstorm and fossilized. The details of this brooding posture and the way in which it
was preserved show that many theropod dinosaurs acted more like birds than like reptiles.
Fastovsky and Weishampel (2005:261) point to another problem: the media. The debate
has been unnaturally prolonged by media attention. The origin of birds has been a topic of
great public interest for the past 20 years, so much so that the leading proponents are fre-
quently interviewed for newspaper articles and TV specials. The rules of journalism require
that “equal time” be given to representatives of each viewpoint. So the supports of the basal
diapsid origin of birds often have as much airtime as the supporters of birds as dinosaurs,
even though the latter represent probably more than 99 percent of working vertebrate
paleontologists.
Before we deal with the creationist distortions about Archaeopteryx, let us review the
evidence that convinced 99 percent of legitimate scientists that birds are dinosaurs. Much
of this evidence is visible in Archaeopteryx itself (fig. 12.9A) and pointed out by Huxley from
the beginning. Darwin could not have asked for a better transitional form than Archaeop-
teryx. As we saw earlier, most of its skeleton is so dinosaurian that one specimen was mis-
taken for the little theropod dinosaur Compsognathus. Like most theropod dinosaurs (but
no living birds), it had a long bony tail, a highly perforated skull with teeth, theropod (not
birdlike) vertebrae, a strap-like shoulder blade, a pelvis midway between that of typical
saurischian dinosaurs and later birds, gastralia (rib bones found in the belly region of dino-
saurs), and unique specializations in the limbs. The most striking of these are in the wrist.
Birds and some theropod dinosaurs, such as the dromaeosaurs (Deinonychus and Velocirap-
tor and its kin), all have a half-moon-shaped wristbone formed of fusion of multiple wrist-
bones known as the semilunate carpal (fig. 12.9B). This bone serves as the main hinge for the
movement of the wrist, allowing dromaeosaurs to extend their wrists and grab prey with
a rapid protraction and retraction. It so happens that exactly the same motion is part of the
downward flight stroke of birds. Archaeopteryx had the same three fingers (thumb, index
finger, and middle finger) as most other theropod dinosaurs, and the middle digit (the index
finger) is by far the longest. In addition, the claws of Archaeopteryx are very similar to those
of theropod dinosaurs.
The hind limbs of Archaeopteryx also have many dinosaurian hallmarks. The most strik-
ing of these is in the ankle (fig. 12.9C). All pterosaurs, dinosaurs, and birds have a unique
ankle arrangement known as the mesotarsal joint. Instead of the typical vertebrate ankle, which
hinges between the shin bone (tibia) and the first row of ankle bones (as your ankle does),
pterosaurs, dinosaurs, and birds developed a hinge between the first and second row of ankle