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

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

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