Biology Now, 2e

262 ■ CHAPTER 14 The History of Life

BIODIVERSITY

Eosinopteryx

Roadrunner

Dromaeosaurids

Troodontids

Aurornis

Anchiornis

Xiaotingia

Archaeopteryx

Other early birds

Node separating

early birds from

dinosaurs

Xiaotingia

Archaeopteryx

Aurornis

Contrary to the tree that arose from his

first study, Godefroit’s second tree places

Archaeopteryx back on its roost in the bird

family, although no longer as the oldest bird.

That place belongs to Aurornis, says Godefroit

(Figure 14.14).

Still, the debate is not over. “Of course we need

more evidence and more work,” says Xu. “Many

of these new species are a possible candidate for

4 cm4 cm

Head

Forelimbs

Tail

Hind limbs

Figure 14.13

A namesake fossil, Aurornis xui,

illuminates the dinosaur-bird transition

Figure 14.14

The early birds

Godefroit’s 2013 study places Archaeopteryx and

Xiaotingia with birds rather than dinosaurs, as in

the traditional dinosaur-bird evolutionary tree

(see Figure 14.6, top). But it places Aurornis as the

earliest known bird on the evolutionary tree.

Q1: Is Xiaotingia an earlier or later bird than

Archaeopteryx in this tree?

Q2: If a future study, based on more fossils

or new measurements, placed Archaeopteryx

back with dinosaurs, would this suggest

that birds are not related to dinosaurs? Why

or why not?

Q3: If you were to create an evolutionary

tree of modern birds, where would you

expect to place the roadrunner (judging by

its appearance in this figure) as compared

to a house sparrow or pigeon?

thousand characteristics of skeletons of 101

species of dinosaurs and birds. “It’s very impres-

sive,” paleontologist Mike Lee at the South

Australian Museum told National Geographic.

“They considered more than twice as much

anatomical information as even the best previ-

ous analyses.”

4 cm

Head

Forelimbs

Tail

Hind limbs

Figure 14.12

Another feathered dinosaur, Eosinopteryx

brevipenna, supports Xu’s new tree