Evolution, 4th Edition

THE HiSToRy oF LiFE 455

flourished from the late Triassic to the end of the Cretaceous, among them the

dolphin-like ichthyosaurs, which gave birth to live young (FIGURE 17.25A).

The diapsids, with two temporal openings, became one of the most diverse

groups of amniotes. One major diapsid lineage, the lepidosaurs, includes the liz-

ards, which became differentiated into modern families in the late Cretaceous.

Among several lineages of lizards in which legs became reduced or lost, one

evolved into the snakes. Snakes became ecologically very diverse during the Cre-

taceous, and again during the Cenozoic.

Futuyma Kirkpatrick Evolution, 4e

Sinauer Associates

Troutt Visual Services

Evolution4e_17.24.ai Date 01-06-2017

Paleozoic Mesozoic Cenozoic

359 299 252 201 145 66 23 Present

Time (Mya)

C P Tr J K Pg Ng

Mammals

Turtles

Crocodilians

Pterosaurs

Ichthyosaurs

Dinosaurs (including birds)

Rhynchocephalians (tuatara)

Squamates (lizards and snakes)

Therapsids

Pelycosaurs

Mesosaurs

Procolophonids

Pareiasaurs

Synapsids

Parareptiles

Reptiles

Diapsids

Amniotes

Captorhinids

Protorothyridids

Archosaurs

Archosauromorphs

Lepidosauromorphs

Lepidosaurs

Ornithodirans

FIGURE 17.24 Phylogenetic relation-

ships and temporal duration (thick bars)

of major groups of amniote vertebrates.

Some authors define “reptiles” as one

of the two major lineages of amniotes,

the other being the synapsids, which

includes mammals. (After [53].)

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