Evolution, 4th Edition

EvoluTion And dEvEloPmEnT 373

body. Heterotopic differences among species are very common in plants (FIGURE

15.4A,B). In vertebrates, many phylogenetically new bones have arisen in tendons

or other connective tissues subject to stress. Many dinosaurs had bony tendons in

the tail, and the giant panda (Ailuropoda melanoleuca) has a novel “thumb” that is

not a true jointed digit (see Fig ure 20.9). Bony elements are conspicuous in the skin

of armadillos and crocodiles (FIGURE 15.4C,D).

The bodies of many organisms consist of modules—distinct units that have

distinct genetic specifications, developmental patterns, locations, and interactions

with other modules [57]. Some such modules are repeated at various sites on the

body and are termed serially homologous. In some cases, serially homologous fea-

tures lack distinct individual identities (e.g., leaves of many plants, teeth of most

amphibians and reptiles) and may be considered representatives of a single charac-

ter. An important evolutionary phenomenon is the acquisition of distinct identities

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

Troutt Visual Services

Evolution4e_1503.ai Date 11-02-2016

(A) (B)

FIGURE 15.3 Neoteny in salamanders.

(A) The tiger salamander (Ambystoma tigri-

num), like most salamanders, undergoes

metamorphosis from an aquatic larva (left;

note the gills) to a terrestrial adult (right).

(B) The adult axolotl (Ambystoma mexica-

num), with gills and tail fin, resembles the

larva of its terrestrial relative. The axolotl

remains aquatic throughout its life.

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

Troutt Visual Services

Evolution4e_1504.ai Date 11-02-2016

(B)

(C)

(D)

(A)

Stem

Roots

FIGURE 15.4 Examples of heterotopy. (A) The vine Monstera deliciosa

has evolved exposed roots that grow from an aerial stem. (B) Entire

plants develop on the leaf margins of Bryophyllum; they eventually drop

off and take root. (C, D) Platelets of bone (osteoderms) develop in the

skin of diverse vertebrates, such as armadillos (C) and crocodiles (D).

15_EVOL4E_CH15.indd 373 3/22/17 1:30 PM