1. 26-1 CHAPTER 26 Amniote Origins and Nonavian Reptiles Amniote Origins and Nonavian Reptiles

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3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-3 Diversity Amniotic “Pond” Any animal with a shell-less egg remains tied to water Any animal with a shell-less egg remains tied to water Development of a shelled egg freed the reptilian groups to exploit land Development of a shelled egg freed the reptilian groups to exploit land Extraembryonic membranes from previous evolutionary aquatic stages are maintained Extraembryonic membranes from previous evolutionary aquatic stages are maintained Allantois serves as a respiratory surface and a chamber to store nitrogenous wastes Allantois serves as a respiratory surface and a chamber to store nitrogenous wastes Chorion allows O 2 and CO 2 to freely pass Chorion allows O 2 and CO 2 to freely pass Surrounding the organism is a porous, parchment- like or leathery shell Surrounding the organism is a porous, parchment- like or leathery shell

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-4 Amniotes Amniota Amniota Nonavian reptiles, birds, and mammals Nonavian reptiles, birds, and mammals Developing young enclosed by extraembryonic membrane called the amnion Developing young enclosed by extraembryonic membrane called the amnion Secretes fluid, amniotic fluid, in which embryo/fetus floats Secretes fluid, amniotic fluid, in which embryo/fetus floats Diversity

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-5 Origin and Early Evolution of Amniotes History separated into groups based on three patterns of fenestra in the temporal region separated into groups based on three patterns of fenestra in the temporal region Anapsids Anapsids Have a skull with no temporal opening behind the orbits Have a skull with no temporal opening behind the orbits Modern turtles Modern turtles Diapsids Diapsids Gave rise to all other traditional “reptiles” (except turtles) and to birds Gave rise to all other traditional “reptiles” (except turtles) and to birds Skull has two temporal openings Skull has two temporal openings One pair below the cheeks and another above One pair below the cheeks and another above

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7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-7 Synapsids Synapsids Mammal-like reptiles with a single pair of temporal openings low on the cheeks Mammal-like reptiles with a single pair of temporal openings low on the cheeks These openings are associated with large muscles that elevate the lower jaw These openings are associated with large muscles that elevate the lower jaw Changes in jaw musculature Changes in jaw musculature Might reflect a shift from suction feeding in aquatic vertebrates to terrestrial feeding Might reflect a shift from suction feeding in aquatic vertebrates to terrestrial feeding Required larger muscles to produce static pressure Required larger muscles to produce static pressure Functional significance of the evolution of temporal openings in amniotes is not fully understood Functional significance of the evolution of temporal openings in amniotes is not fully understood Origin and Early Evolution of Amniotes

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9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-9 Derived Characters of Amniotes Amniotic egg All amniotes have eggs with four extraembryonic membranes All amniotes have eggs with four extraembryonic membranes Amnion, allantois, chorion, and yolk sac Amnion, allantois, chorion, and yolk sac Amnion Amnion Encloses the embryo in fluid-filled space Encloses the embryo in fluid-filled space Cushions the embryo and provides an aqueous medium for growth Cushions the embryo and provides an aqueous medium for growth Allantois Allantois Stores metabolic wastes Stores metabolic wastes Origin and Early Evolution of Amniotes

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11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-11 Chorion Chorion Surrounds embryo and all other extraembryonic membranes Surrounds embryo and all other extraembryonic membranes Lies just beneath shell Lies just beneath shell Highly vascularized Highly vascularized Respiratory surface Respiratory surface Allantois and chorion sometimes fuse to form respiratory structure: chorioallantoic membrane Allantois and chorion sometimes fuse to form respiratory structure: chorioallantoic membrane Yolk sac Yolk sac Nutrient storage Nutrient storage Origin and Early Evolution of Amniotes

12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-12 Amniotic egg permitted development of a larger, faster-growing embryo Amniotic egg permitted development of a larger, faster-growing embryo One hypothesis suggests that one step in the evolution of the amniotic egg was replacement of the jelly layer with a shell One hypothesis suggests that one step in the evolution of the amniotic egg was replacement of the jelly layer with a shell Provided better support and movement of oxygen Provided better support and movement of oxygen Shell could also be broken down to provide calcium for growing skeletal structures Shell could also be broken down to provide calcium for growing skeletal structures All amniotes All amniotes Lack gilled larvae and have internal fertilization Lack gilled larvae and have internal fertilization Eliminated the need for aquatic environments Eliminated the need for aquatic environments copulatory organ copulatory organ Derived from cloacal wall, appears to be an amniote innovation Derived from cloacal wall, appears to be an amniote innovation Origin and Early Evolution of Amniotes

13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-13 Thicker and more waterproof skin Amniote skin is thick and tends to be more keratinized and less permeable to water Amniote skin is thick and tends to be more keratinized and less permeable to water Variety of structures composed of keratin such as scales, hair, feathers, and claws project from the skin Variety of structures composed of keratin such as scales, hair, feathers, and claws project from the skin Keratin protects the skin from physical trauma, and lipids prevent water loss Keratin protects the skin from physical trauma, and lipids prevent water loss Few amniotes use skin as a primary respiratory organ because keratin and lipids limit exchange of gases Few amniotes use skin as a primary respiratory organ because keratin and lipids limit exchange of gases Origin and Early Evolution of Amniotes

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-14 Resistance to desiccation Resistance to desiccation Provided primarily hydrophobic lipids in epidermis Provided primarily hydrophobic lipids in epidermis Scales of nonavian reptiles Scales of nonavian reptiles Formed mostly of beta keratin and provide protection against wear in terrestrial environments Formed mostly of beta keratin and provide protection against wear in terrestrial environments In crocodilians, scales remain throughout life In crocodilians, scales remain throughout life In other nonavian reptiles such as lizards and snakes, new keratinized epidermis replaces old epidermis which is shed In other nonavian reptiles such as lizards and snakes, new keratinized epidermis replaces old epidermis which is shed Turtles have scutes Turtles have scutes Platelike modified scales Platelike modified scales Crocodiles and many lizards possess osteoderms Crocodiles and many lizards possess osteoderms Bony plates located the dermis beneath scales Bony plates located the dermis beneath scales Characteristics of Nonavian Reptiles

15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-15 Characteristics of Nonavian Reptiles Nonavian reptiles have better developed lungs than amphibians Nonavian reptiles have better developed lungs than amphibians Nonavian lungs have more surface area than amphibians’ lungs Nonavian lungs have more surface area than amphibians’ lungs Nonavian ventilation occurs by drawing air into the lungs rather than pushing air into the lungs Nonavian ventilation occurs by drawing air into the lungs rather than pushing air into the lungs Nonavian reptiles expand the thoracic cavity thus expanding the rib cage in order to draw air in Nonavian reptiles expand the thoracic cavity thus expanding the rib cage in order to draw air in Pulmonary respiration is supplemented by respiration in the cloaca or pharynx in many aquatic turtles and by cutaneous respiration in sea snakes and turtles Pulmonary respiration is supplemented by respiration in the cloaca or pharynx in many aquatic turtles and by cutaneous respiration in sea snakes and turtles

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-16 Jaws of nonavian reptile Jaws of nonavian reptile Efficiently designed for applying crushing or gripping force to prey Efficiently designed for applying crushing or gripping force to prey Larger jaw muscles have mechanical advantage over the jaws of fishes which are designed for suction feeding or for quick closure Larger jaw muscles have mechanical advantage over the jaws of fishes which are designed for suction feeding or for quick closure Tongue is muscular and mobile Tongue is muscular and mobile Functions to move food in mouth for mastication and swallowing Functions to move food in mouth for mastication and swallowing Characteristics of Nonavian Reptiles

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-17 Nonavian reptiles have an efficient and versatile circulatory system and higher blood pressure than amphibians Nonavian reptiles have an efficient and versatile circulatory system and higher blood pressure than amphibians Right atrium receives deoxygenated blood and is partitioned from the left atrium which receives oxygenated blood Right atrium receives deoxygenated blood and is partitioned from the left atrium which receives oxygenated blood Crocodilians have separated ventricles Crocodilians have separated ventricles In other nonavian reptiles, ventricle is incompletely partitioned into multiple chambers In other nonavian reptiles, ventricle is incompletely partitioned into multiple chambers All nonavian reptiles have two functionally separate circulations All nonavian reptiles have two functionally separate circulations Characteristics of Nonavian Reptiles

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19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-19 Nonavian reptiles have efficient strategies for water conservation Nonavian reptiles have efficient strategies for water conservation secrete nitrogenous wastes as uric acid Relatively non-toxic secrete nitrogenous wastes as uric acid Relatively non-toxic All amniotes have metanephric kidneys All amniotes have metanephric kidneys Nonavian reptiles cannot concentrate urine in the kidneys Nonavian reptiles cannot concentrate urine in the kidneys Urinary bladder receives undiluted urine Urinary bladder receives undiluted urine Water and most salts Water and most salts Resorbed in the bladder Resorbed in the bladder “urine” voided as a semisolid mass of uric acid “urine” voided as a semisolid mass of uric acid Salt is removed by salt glands near the nose, eyes, or tongue Salt is removed by salt glands near the nose, eyes, or tongue Characteristics of Nonavian Reptiles

20. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-20 The nervous system of nonavian reptiles is more complex than that of amphibians The nervous system of nonavian reptiles is more complex than that of amphibians Brain of nonavian reptiles small compared to brain of other amniotes Brain of nonavian reptiles small compared to brain of other amniotes However, cerebrum of all amniotes is relatively enlarged However, cerebrum of all amniotes is relatively enlarged Enlargement of cerebrum correlated with integration of sensory information and muscle control during locomotion Enlargement of cerebrum correlated with integration of sensory information and muscle control during locomotion Nonavian reptiles have good vision Nonavian reptiles have good vision Snakes and many lizards use a highly sensitive sense of smell to find prey and mates Snakes and many lizards use a highly sensitive sense of smell to find prey and mates Olfaction assisted by a Jacobson’s organ, a specialized olfactory chamber in the roof of the mouth Olfaction assisted by a Jacobson’s organ, a specialized olfactory chamber in the roof of the mouth Characteristics of Nonavian Reptiles

21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Video Links Reptiles of Africa Reptiles of Africa Reptiles of Africa Reptiles of Africa The four monophyletic nonavian reptilian groups are: The four monophyletic nonavian reptilian groups are: Turtles Turtles Crocodilians Crocodilians Squamates Squamates tuataras tuataras 26-21

22. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-22 Characteristics and Natural History of Reptilian Orders Turtles (Chelonia) Shells consist of a dorsal carapace and a ventral plastron Shells consist of a dorsal carapace and a ventral plastron Unique among vertebrates, limbs and limb girdles are located deep to the ribs Unique among vertebrates, limbs and limb girdles are located deep to the ribs Lack teeth and use tough, horny plates for gripping food Lack teeth and use tough, horny plates for gripping food Consequence of having a rigid shell Consequence of having a rigid shell Turtle cannot expand chest to breathe Turtle cannot expand chest to breathe Solve problem by using abdominal and pectoral muscles as a “diaphragm” Solve problem by using abdominal and pectoral muscles as a “diaphragm” Air is drawn in by contraction of the limb flank muscles, increasing abdominal cavity volume Air is drawn in by contraction of the limb flank muscles, increasing abdominal cavity volume

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24. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-24 Snapping Turtles Snapping Turtles Have a reduced shell that does not permit full withdrawal of the body Have a reduced shell that does not permit full withdrawal of the body Jaws are adequate defense Jaws are adequate defense Entirely carnivorous and can eat fish, frogs, waterfowl, etc. Entirely carnivorous and can eat fish, frogs, waterfowl, etc. Aquatic but must come ashore to lay eggs Aquatic but must come ashore to lay eggs Loggerhead Turtles Loggerhead Turtles Loggerhead Turtles Loggerhead Turtles Characteristics and Natural History of Reptilian Orders

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26. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-26 Squamates: Lizards and Snakes Account for up 95% of living nonavian reptiles Account for up 95% of living nonavian reptiles Allowed evolution in lizards of a mobile skull with movable joints, a kinetic skull Allowed evolution in lizards of a mobile skull with movable joints, a kinetic skull Exceptional skull mobility of snakes is considered a major factor in their diversification Exceptional skull mobility of snakes is considered a major factor in their diversification Snake Fakes Snake Fakes Snake Fakes Snake Fakes Jesus Christ Lizard Jesus Christ Lizard Jesus Christ Lizard Jesus Christ Lizard Characteristics and Natural History of Reptilian Orders

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29. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-29 Suborder Sauria: Lizards Diverse group with terrestrial, burrowing, aquatic, arboreal, and some aerial members Diverse group with terrestrial, burrowing, aquatic, arboreal, and some aerial members Lizards Lizards Lizards Geckos Geckos Small, agile, nocturnal forms Small, agile, nocturnal forms Adhesive toe pads allow them to walk on ceilings Adhesive toe pads allow them to walk on ceilings Iguanids Iguanids Include many New World lizards as well as the marine iguana of the Galápagos Include many New World lizards as well as the marine iguana of the Galápagos Chameleons Chameleons Arboreal lizards of Africa and Madagascar Arboreal lizards of Africa and Madagascar Many have an extendible tongue Many have an extendible tongue Characteristics and Natural History of Reptilian Orders

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32. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-32 Some have degenerate limbs Some have degenerate limbs Glass lizards are nearly limbless Glass lizards are nearly limbless Movable eyelids whereas snakes have a transparent covering Movable eyelids whereas snakes have a transparent covering Amphisbaenians or “worm lizards” highly specialized for a fossorial (burrowing life Amphisbaenians or “worm lizards” highly specialized for a fossorial (burrowing life Characteristics and Natural History of Reptilian Orders

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34. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-34 Conserve water by producing semisolid urine with a high content of crystalline uric acid Conserve water by producing semisolid urine with a high content of crystalline uric acid Some can store fat in tails to provide energy and metabolic water during drought Some can store fat in tails to provide energy and metabolic water during drought Gila monster and beaded lizard are the only lizards capable of a venomous bite Gila monster and beaded lizard are the only lizards capable of a venomous bite Lizards keep body temperature relatively constant by behavioral thermoregulation, although they are ectotherms Lizards keep body temperature relatively constant by behavioral thermoregulation, although they are ectotherms Successful strategy in ecosystems with low productivity and warm climates, such as tropical deserts and grasslands Successful strategy in ecosystems with low productivity and warm climates, such as tropical deserts and grasslands Characteristics and Natural History of Reptilian Orders

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37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-37 Suborder Serpentes: Snakes Limbless and have lost pectoral and pelvic girdles (except in pythons) Limbless and have lost pectoral and pelvic girdles (except in pythons) Feeding apparatus allows them to eat prey several times their own diameter Feeding apparatus allows them to eat prey several times their own diameter Two halves of lower jaw are loosely joined, allowing them to spread apart Two halves of lower jaw are loosely joined, allowing them to spread apart Skull bones also loosely articulated so mouth can accommodate large prey Skull bones also loosely articulated so mouth can accommodate large prey To allow breathing during the slow process of swallowing, the tracheal opening is extended To allow breathing during the slow process of swallowing, the tracheal opening is extended Sidewinding snake Sidewinding snake Sidewinding snake Sidewinding snake Characteristics and Natural History of Reptilian Orders

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39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-39 Eyeballs have reduced mobility and a permanent corneal membrane for protection Eyeballs have reduced mobility and a permanent corneal membrane for protection Most have poor vision Most have poor vision Arboreal snakes in tropical forests have highly developed vision Arboreal snakes in tropical forests have highly developed vision Lack external ears and do not respond to most aerial sounds Lack external ears and do not respond to most aerial sounds Can feel vibrations at low frequencies, especially vibrations carried in the ground Can feel vibrations at low frequencies, especially vibrations carried in the ground Chemical senses rather than vision or hearing are main senses used to hunt prey Chemical senses rather than vision or hearing are main senses used to hunt prey Characteristics and Natural History of Reptilian Orders

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41. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-41 Jacobson’s organs Jacobson’s organs Pair of pits in the roof of the mouth Pair of pits in the roof of the mouth Lined with olfactory epithelium Lined with olfactory epithelium Forked tongue picks up scent particles and conveys them to this organ Forked tongue picks up scent particles and conveys them to this organ Nonvenomous snakes Nonvenomous snakes Kill prey by constriction or by biting and swallowing Kill prey by constriction or by biting and swallowing Skin is infolded between scales Skin is infolded between scales When stretched by a large meal, the skin is unfolded When stretched by a large meal, the skin is unfolded Characteristics and Natural History of Reptilian Orders

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45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-45 Snakebite and Toxicity Snakebite and Toxicity Neurotoxins act on the nervous system, causing blindness or inhibit respiration Neurotoxins act on the nervous system, causing blindness or inhibit respiration Hemorrhagin type venoms break down blood vessels Blood leaks into tissue spaces Hemorrhagin type venoms break down blood vessels Blood leaks into tissue spaces Sea snakes and the Australian tiger snake have the most deadly venom per unit volume Sea snakes and the Australian tiger snake have the most deadly venom per unit volume Reproduction Reproduction Most are oviparous and lay shelled eggs, pit vipers are ovoviviparous, A few snakes are viviparous, having a primitive placenta to exchange nutrients with the young Most are oviparous and lay shelled eggs, pit vipers are ovoviviparous, A few snakes are viviparous, having a primitive placenta to exchange nutrients with the young Female snakes can store sperm and lay several clutches of fertile eggs long after a single mating Female snakes can store sperm and lay several clutches of fertile eggs long after a single mating Characteristics and Natural History of Reptilian Orders

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47. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-47 The Tuatara Only 2 living species in New Zealand represent this ancient lineage Only 2 living species in New Zealand represent this ancient lineage Loss of the tuatara populations caused by human introduction of nonnative species which preyed upon the tuatara Loss of the tuatara populations caused by human introduction of nonnative species which preyed upon the tuatara Tuatara are vulnerable because they have slow growth and reproductive rates Tuatara are vulnerable because they have slow growth and reproductive rates Lizard-like and live in burrows Lizard-like and live in burrows Slow growing and may live to 77 years of age Slow growing and may live to 77 years of age Well-developed median parietal eye buried beneath skin Well-developed median parietal eye buried beneath skin Characteristics and Natural History of Reptilian Orders

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49. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-49 Crocodilia: Crocodiles and Alligators Crocodilia: Crocodiles and Alligators Modern crocodilians differ little from primitive crocodilians of the early Mesozoic Modern crocodilians differ little from primitive crocodilians of the early Mesozoic There are 3 families of modern crocodilians There are 3 families of modern crocodilians Alligators and caimans are found primarily in the New World and have a broader snout Alligators and caimans are found primarily in the New World and have a broader snout Crocodiles are widely distributed Crocodiles are widely distributed One species of gavial occurs in India and Burma and has a very narrow snout One species of gavial occurs in India and Burma and has a very narrow snout Characteristics and Natural History of Reptilian Orders

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51. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-51 All have long, well-reinforced skull and jaw musculature for a powerful bite All have long, well-reinforced skull and jaw musculature for a powerful bite Theocodont dentition Theocodont dentition Teeth are set in sockets Teeth are set in sockets Have a complete secondary palate, a feature only shared with mammals Have a complete secondary palate, a feature only shared with mammals Four-chambered heart Four-chambered heart Alligators and crocodiles are oviparous Alligators and crocodiles are oviparous Usually 20–50 eggs are laid in mass of vegetation Usually 20–50 eggs are laid in mass of vegetation Unguarded nests are easily discovered and raided by predators Unguarded nests are easily discovered and raided by predators High nest temperatures produce males High nest temperatures produce males Low temperatures produce females Low temperatures produce females Can result in females outnumbering males 5 to 1 Can result in females outnumbering males 5 to 1 Characteristics and Natural History of Reptilian Orders