Chapter 7 Evolution of Reptiles

Introduction
Class Reptilia: turtles, tuatara, lizards, snakes, and crocodilians
Class Aves: birds
Saurapsida group (cladistics): turtles (Testudomorpha);tuataras, lizards,
snakes (Lepidosauromorpha); crocodilians, birds (Archosauromorpha)

Evolution
Fig.1 The evolutionary origin of amniotes
Fig.2 Cladogram of living amniotes
1.
Ancestral Reptiles
Earliest amniotes : Low Carboniferous of Scotland, 338 m.y.a.
Upper Carboniferous: synapsids-mammals
Anapsids-turtles
Diapsid-other reptilian groups
Low Permian: Seymour Fig.7.3
Combination of amphibians and repliles
Difference between amphibians and reptiles: egg produced and
young development
Fig. 7.4 Amniotic egg: chorion, amnion, yolk sac, allantois
Romer (1957): It was the egg which ashore first; the adult followed.
Terrestrial eggs evolved as a device for escaping predation
2.
Ancient and Living Reptiles
Dominant in Mesozoic era
Terrestrial, aquatic, aerial groups
Bipedal and quadrupedal group
Carnivorous and herbivorous groups
Now, 4 orders remain
Traditional classification of reptiles is based on temporal fenestrae
Fig.7.5 three groups
Anapsida
Diapsida
Synapsida
Cladistic classification: Testudomorpha: turtles (anapsida)
Lepidosauomorpha: tuataras, lizard and snakes (diapsid)
Archosaura: crocodilians and birds (diapsid)
(1)
Turtles (Testudomorpha)
Early Carboniferous
Fig.7.6 ancestor of turtles
Living turtle: Triassic 210 m.y.a
Largest turtle: Fig.7.7c 3.3 m
(2)
Ichthyosaurs, plesiosaurs, Tuatara, Lizard, and Snakes
(Lepidosauromorpha)
Two major extinct groups: ichthyosaurs and plesiosaurs
One living group: Aquamata: Sphenodontia( tuataras), Lacertilia
(lizard), Serpents (snakes)
Ichthyosauria: Fig.7.8 paddlelike limbs, sharklike dorsal fin
Extinct in Cretaceous
Plesiosauria: Fig.7.9 broad, flattened limbs, dorsoventrally
compressed trunk
Extinct in Cretaceous
Sephenodontidae: 喙頭目 Fig.7.10 鱷蜥 relics from Triassic,
new Zealand, two living species
Characters:
Dentition
Pineal or third eyes
Living in burrow, nocturnal
0.6m, 20 years old
Squamata:有鱗目
Since Triassic
Snakes, lizards, amphisbaenans
(3)
Thecodonts, Nonavian, Dinosaurs, Pterosaurs, Crocodilians,
and Birds (Archosauromorpha)
Diapsids
Extinct: Thecodonts, Dinosaurs, Pterosaurs
Living: crocodilians and birds
Thecodontia: Proterosuchia
Fig. 7.11 primitive thecodontia was ancestral to the dinosaurs,
pterosaurs, and birds
20Kg-80,000Kg
Fig7.12 Dinosaur tracks, 64Km/hr
Dinosaurs: 350 species, Fig.13 Saurischia, Orithischia, Fig.7.15
Fog.7.14Herrerasaurus: protodinosaurs 225-230m.y.a.
Saurischia:
Lizard-hipped pelvic girdle
Quadrupedal and bipedal herbivores and carnivores
Two types of Saurischia:
Theropods, and sauropodomorphs
Theropods: birds, carnivorous dinosaur genera Fig. 7.16
Largest terrestrial carnivores: Tyrannosaurus length: 16m,
heigh:5.8m, weight:9000kg
Bio-Note 7.4 Coprolites: fossil feces-44cm
CT scan technique to study the
skeleton system of dinosaurs
Homeothermic or not?
Air canals ramifying through their skull: regulation temperature
Absence of turbinate bone: poikilothermic
Annual growth ringsFig.7.17
hepatic-piston diaphragm
Sauropodomorphs: Fig.7.18a all herbivorous
Largest quadrupeds: 18m tall, 30m long, 54,000kg
Cyberpaleontology: use computer-generated images to better
understand the biomechanical movements
Ornithischia: Fig. 7.15b
Birdlike pelvic girdle
Thin, pencil-shaped teeth
Lower jaw : horn-covered beak
Long, slender bodies
Whiplike tails
Bipedal or quadrupedal herbivores
Five groups : ornithopod, ceratopsians, pachycehalosaurs,
stegosaurs, and ankylosaurs
Ornithopod: duck-billed dinosaurs Fig.7.18b
Ceratopsian: parrotlike beak Fig.17.18c
Pachycephalosaurs: domed and reinforced head Fig.7.19a
Stegosaurs: plated dinosaurs Fig.7.19b
Ankylosaurs: heavily armored Fig.7.19c
Pterosauria: Archosaurians
The earliest known flying vertebrate
Fig.7.20 skeleton
Bones: hollow and air-filled
Fig7.21flight membrane
Locomotion
Extinct in Cretaceous
Crocodiles: alligators, crocodiles, caimans
Giant crocodiles: 12m long, 2.5 m tall, 12000kg
Aves:
Fig.7.23 Evolution of modern birds
The origin of birds
(1)
dinosaur (theropod)-bird, 200 anatomical features shared by
birds and dinosaurs
(2)
dinosaurs and birds shared a common thecodont ancestor
(3)
Dinosauria- dinosaurs, the therapsids, and the birds
(4)
Crocodilians and birds are living sister groups
(5)
Feathered dinosaurs 1996, from Upper Jurassic-unable to
actually fly, ground-living, bipedal dinosaurs
Ancestral Birds
1861 – impression of feather
1876 – Fig. 7.25 Archaeopteryx lithographica – Jurassic , 150 m.y.a.
intermediate between modern birds and thecodonts
Fig. 7.26 Late Jurassic primitive birds
Fig.7.27 Upper Cretaceous bird
Fig. 7.28 Fossil reveals living birds are just one branch on the avian
family tree
1986 Protoavis Fig. 7.29 from Triassic
Modern Birds
The greatest radiation in the Cenozoic era
The avian fauna during the Pleistocene was even richer
Origin of Flight
Two hypothesiscursorial,
(1) groung-dwelling form – gliding flight – flapping flight
(2) arboreal – jumping