The Chordata
Chapter 34
Chordate characteristics
Figure 34.1 Clades of extant chordates
Subphylum Cephalochordata: the lancelet Branchiostoma
Subphylum Cephalochordata: lancelet anatomy
Pikaia, the Burgess-shale chordate, with evident somites
Primitive chordates suggest first steps in their evolution ---
Figure 34.1 Clades of extant chordates
tunicates
The hagfish: a skull of cartilage and primitive eyes, but no jaw, no vertebrae
Figure 34.1 Clades of extant chordates
Figure 34.9 A sea lamprey
Origin of the jaw: transformation of skeletal rods accompanying gills
Figure 34.11 Cartilaginous fishes (class Chondrichthyes): Great white shark (top left), silky shark (top right), southern stingray (bottom left), blue spotted stingray
(bottom right)
Figure 34.12a Ray-finned fishes (class Actinopterygii): yellow perch
Figure 34.12b Ray-finned fishes (class Actinopterygii): long-snouted sea horse
Figure 34.13 Anatomy of a trout, a representative ray-finned fish
Figure 34.1 Clades of extant chordates
Figure 34.7 Phylogeny of the major groups of extant vertebrates
Figure 34.18 A coelocanth (Latimeria), the only extant lobe-finned genus
Figure 34.15 The origin of tetrapods
Figure 34.16 Skeleton of Acanthostega, a Devonian tetrapod fish
Transitional tetrapods -- feet in place but gills and tail with fin
Figure 34.17 Amphibian orders: Newt (left), frog (right)
Figure 34.18 “Dual life” of a frog (Rana temporaria)
Figure 34.22 A hatching reptile
Figure 34.24 Amniotic egg
Amnion: cushioning chamber for embryo
Chorion: gas exchange to exterior
Allantois: disposal sac
A phylogeny of amniotes
Figure 34.24 Extant reptiles: Desert tortoise (top left), lizard (top right), king snake (bottom left), alligators (bottom right)
Figure 25.16 Building a phylogenetic tree of dinosaurs
Figure 34.23 A phylogeny of amniotes
Figure 34.27x Archaeopteryx
Pelvises:Left, a saurischian carnivoreCenter, an ornithischian herbivoreRight, Archaeopteryx
Figure 34.27 Archaeopteryx, a Jurassic bird-reptile
Figure 34.28b Cretaceous theropod dinosaurs with putative feathers from Chinese sediments: Caudipteryx
Figure 34.29 A small sample of birds: Blue-footed boobies (top left), male peacock (top right), penguins (bottom left), perching bird (bottom right)
Figure 34.23 A hypothetical phylogeny of amniotes
Figure 34.32 Evolution of the mammalian jaw and ear bones
Figure 34.36 Hypothetical cladogram of mammals
Figure 34.32 Evolutionary convergence of marsupial and eutherian (placental) mammals
Figure 34.34 Prosimians:Lemurs
A phylogenetic tree of primates
The Cenozoic
Fig. 24.40: A timeline for some selected hominin species:
Australopithecus afarensis and the Laetoli footprints
3.24 mya 3.5 mya
The Cenozoic
Closeup --- Late Cenozoic
Fig. 24.40: A timeline for some selected hominin species:
Neanderthal and human
Mitochondrial DNA phylogeny for Homo sapiens and H. neanderthalis
HUMAN MIGRATIONS
Secondary contact between the last Neanderthals and humans