THE HiSToRy oF LiFE 445
Futuyma Kirkpatrick Evolution, 4e
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Evolution4e_1712.ai Date 11-02-2016(A)(C)(B)(D) (E)FIGURE 17.12 Nautiloids and ammonoids. Shells housed the squidlike bodies of these
cephalopod molluscs. (A) The chambered nautilus (Nautilus pompilius), one of the
few living species of nautiloid. (B) An orthoconic nautiloid, believed to belong to the
same group as the modern Nautilus. These animals had noncoiled shells. (C) A Juras-
sic ammonoid, Craspedites, showing the intricate sutures that evolved in many later
ammonoids. (D) Kosmoceras, a Jurassic ammonoid. (E) Australoceras, a Cretaceous
ammonoid with a very different form of shell.Futuyma Kirkpatrick Evolution, 4e
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Evolution4e_1713.ai Date 11-02-2016(A)(B)(C)FIGURE 17.13 Extinct Paleozoic classes of fishlike vertebrates. (A) A jawless ostraco-
derm, class Heterostraci (Pteraspis, Devonian). (B) A gnathostome (jawed vertebrate),
class Acanthodii (Climatius, Devonian). Gnathostomes evolved from jawless ancestors.
(C) A placoderm (Bothriolepis, Devonian).17_EVOL4E_CH17.indd 445 3/22/17 1:37 PM