26-1 chapter 26 amniote origins and nonavian reptiles amniote origins and nonavian reptiles

26-1

CHAPTER 26CHAPTER 26CHAPTER 26CHAPTER 26

Amniote Origins Amniote Origins and Nonavian and Nonavian

ReptilesReptiles

Amniote Origins Amniote Origins and Nonavian and Nonavian

ReptilesReptiles

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

26-2


26-3

DiversityDiversity

Amniotic “Pond”Amniotic “Pond” Any animal with a shell-less egg remains tied to Any animal with a shell-less egg remains tied to

waterwater Development of a Development of a shelled eggshelled egg freed the reptilian freed the reptilian

groups to exploit landgroups to exploit land Extraembryonic membranesExtraembryonic membranes from previous from previous

evolutionary aquatic stages are maintainedevolutionary aquatic stages are maintained AllantoisAllantois serves as a respiratory surface and a serves as a respiratory surface and a

chamber to store nitrogenous wasteschamber to store nitrogenous wastes ChorionChorion allows O allows O22 and CO and CO22 to freely pass to freely pass Surrounding the organism is a porous, parchment-Surrounding the organism is a porous, parchment-

like or leathery shelllike or leathery shell


26-4

AmniotesAmniotes Amniota Amniota

Nonavian reptiles, birds, and mammalsNonavian reptiles, birds, and mammals Developing young enclosed by extraembryonic Developing young enclosed by extraembryonic

membrane called the membrane called the amnionamnion Secretes fluid, amniotic fluid, in which Secretes fluid, amniotic fluid, in which

embryo/fetus floatsembryo/fetus floats

DiversityDiversity


26-5

Origin and Early Evolution of AmniotesOrigin and Early Evolution of Amniotes

HistoryHistory separated into groupsseparated into groups based on three based on three

patterns of fenestra in the temporal region patterns of fenestra in the temporal region AnapsidsAnapsids

Have a skull with Have a skull with no temporal openingno temporal opening behind behind the orbitsthe orbits

Modern turtles Modern turtles Diapsids Diapsids

Gave rise to all other traditional “reptiles” Gave rise to all other traditional “reptiles” (except turtles) and to birds(except turtles) and to birds

Skull has Skull has two temporal openingstwo temporal openings One pair below the cheeks and another One pair below the cheeks and another

aboveabove


26-6


26-7

SynapsidsSynapsids Mammal-like reptiles with a Mammal-like reptiles with a single pairsingle pair of of

temporal openings low on the cheekstemporal openings low on the cheeks These openings are associated with large These openings are associated with large

muscles that elevate the lower jawmuscles that elevate the lower jaw Changes in jaw musculatureChanges in jaw musculature

Might reflect a shift from suction feeding in aquatic Might reflect a shift from suction feeding in aquatic vertebrates to terrestrial feeding vertebrates to terrestrial feeding

Required larger muscles to produce static pressureRequired larger muscles to produce static pressure Functional significance of the evolution of Functional significance of the evolution of

temporal openings in amniotes is not fully temporal openings in amniotes is not fully understoodunderstood



26-8


26-9

Derived Characters of AmniotesDerived Characters of Amniotes

Amniotic eggAmniotic egg All amniotes have eggs with All amniotes have eggs with four four

extraembryonic membranesextraembryonic membranes Amnion, allantois, chorion, and yolk sacAmnion, allantois, chorion, and yolk sac

AmnionAmnion Encloses the embryo in fluid-filled spaceEncloses the embryo in fluid-filled space Cushions the embryo and provides an aqueous Cushions the embryo and provides an aqueous

medium for growthmedium for growth Allantois Allantois

Stores metabolic wastesStores metabolic wastes



26-10


26-11

Chorion Chorion Surrounds embryo and all other extraembryonic Surrounds embryo and all other extraembryonic

membranes membranes Lies just beneath shellLies just beneath shell Highly vascularizedHighly vascularized Respiratory surfaceRespiratory surface Allantois and chorion sometimes fuse to form Allantois and chorion sometimes fuse to form

respiratory structure: chorioallantoic membranerespiratory structure: chorioallantoic membrane Yolk sacYolk sac

Nutrient storageNutrient storage



26-12

Amniotic egg permitted development of a Amniotic egg permitted development of a larger, larger, faster-growing embryofaster-growing embryo

One hypothesis suggests that one step in the One hypothesis suggests that one step in the evolution of the amniotic egg was evolution of the amniotic egg was replacement of the replacement of the jelly layer with a shelljelly layer with a shell Provided better support and movement of oxygenProvided better support and movement of oxygen Shell could also be broken down to provide calcium for Shell could also be broken down to provide calcium for

growing skeletal structuresgrowing skeletal structures All amniotes All amniotes

Lack gilled larvae and have internal fertilizationLack gilled larvae and have internal fertilization Eliminated the need for aquatic environmentsEliminated the need for aquatic environments

copulatory organcopulatory organ Derived from cloacal wall, appears to be an amniote Derived from cloacal wall, appears to be an amniote

innovationinnovation



26-13

Thicker and more waterproof skin Thicker and more waterproof skin Amniote skinAmniote skin is thick and tends to be more is thick and tends to be more

keratinized and less permeable to waterkeratinized and less permeable to water Variety of structures composed of keratin Variety of structures composed of keratin

such as scales, hair, feathers, and claws such as scales, hair, feathers, and claws project from the skinproject from the skin

Keratin protects the skin from physical Keratin protects the skin from physical trauma, and lipids prevent water losstrauma, and lipids prevent water loss

Few amniotes use skin as a primary Few amniotes use skin as a primary respiratory organ because respiratory organ because keratin and lipids keratin and lipids limit exchange of gaseslimit exchange of gases



26-14

Resistance to desiccation Resistance to desiccation Provided primarily hydrophobic lipids in epidermisProvided primarily hydrophobic lipids in epidermis

Scales of nonavian reptilesScales of nonavian reptiles Formed mostly of beta keratin and provide Formed mostly of beta keratin and provide

protection against wear in terrestrial environmentsprotection against wear in terrestrial environments In crocodilians,In crocodilians, scales remain throughout life scales remain throughout life In other nonavian reptiles such as In other nonavian reptiles such as lizards and lizards and

snakes,snakes, new keratinized epidermis replaces old new keratinized epidermis replaces old epidermis which is shedepidermis which is shed

Turtles have Turtles have scutesscutes Platelike modified scalesPlatelike modified scales

Crocodiles and many lizards possess Crocodiles and many lizards possess osteodermsosteoderms Bony plates located the dermis beneath scalesBony plates located the dermis beneath scales

Characteristics of Nonavian Reptiles Characteristics of Nonavian Reptiles


26-15


Nonavian reptiles have better developed Nonavian reptiles have better developed lungs than amphibianslungs than amphibians Nonavian lungs have more surface area than Nonavian lungs have more surface area than

amphibians’ lungsamphibians’ lungs Nonavian ventilation occurs by drawing air into Nonavian ventilation occurs by drawing air into

the lungs rather than pushing air into the lungsthe lungs rather than pushing air into the lungs Nonavian reptiles expand the thoracic cavity thus Nonavian reptiles expand the thoracic cavity thus

expanding the rib cage in order to draw air inexpanding the rib cage in order to draw air in Pulmonary respiration is supplemented by Pulmonary respiration is supplemented by

respiration in the cloaca or pharynx in many respiration in the cloaca or pharynx in many aquatic turtles and by cutaneous respiration in aquatic turtles and by cutaneous respiration in sea snakes and turtlessea snakes and turtles


26-16

Jaws of nonavian reptileJaws of nonavian reptile Efficiently designed for applying Efficiently designed for applying crushing or crushing or

gripping force to preygripping force to prey Larger jaw Larger jaw musclesmuscles have mechanical advantage have mechanical advantage

over the jaws of fishes which are designed for over the jaws of fishes which are designed for suction feeding or for quick closuresuction feeding or for quick closure

Tongue is muscular and mobileTongue is muscular and mobile Functions to move food in mouth for mastication Functions to move food in mouth for mastication

and swallowingand swallowing



26-17

Nonavian reptiles have an efficient and Nonavian reptiles have an efficient and versatile circulatory system and higher blood versatile circulatory system and higher blood pressure than amphibians pressure than amphibians Right atrium receives deoxygenated blood and is Right atrium receives deoxygenated blood and is

partitioned from the left atrium which receives partitioned from the left atrium which receives oxygenated bloodoxygenated blood

Crocodilians have Crocodilians have separated ventriclesseparated ventricles In other nonavian reptiles, ventricle is In other nonavian reptiles, ventricle is

incompletely partitioned into multiple incompletely partitioned into multiple chamberschambers

All nonavian reptiles have All nonavian reptiles have two functionally two functionally separate circulationsseparate circulations



26-18


26-19

Nonavian reptiles haveNonavian reptiles have efficient strategies for efficient strategies for water conservationwater conservation secrete nitrogenous wastes as secrete nitrogenous wastes as uric acid uric acid Relatively Relatively

non-toxicnon-toxic All amniotesAll amniotes have metanephric kidneys have metanephric kidneys

Nonavian reptilesNonavian reptiles cannot concentrate urine in cannot concentrate urine in the kidneysthe kidneys

Urinary bladder receives undiluted urineUrinary bladder receives undiluted urine Water and most saltsWater and most salts

Resorbed in the bladder Resorbed in the bladder ““urine” voided as a urine” voided as a semisolid masssemisolid mass of uric of uric

acidacid Salt is removed by Salt is removed by salt glandssalt glands near the nose, near the nose,

eyes, or tongueeyes, or tongue



26-20

The nervous system of nonavian reptiles is The nervous system of nonavian reptiles is more complex than that of amphibiansmore complex than that of amphibians Brain of nonavian reptiles small compared to Brain of nonavian reptiles small compared to

brain of other amniotesbrain of other amniotes However, However, cerebrumcerebrum of all amniotes is relatively of all amniotes is relatively

enlargedenlarged Enlargement of cerebrum correlated with Enlargement of cerebrum correlated with

integration of integration of sensory information and muscle sensory information and muscle control during locomotioncontrol during locomotion

Nonavian reptiles have Nonavian reptiles have good visiongood vision Snakes and many lizards use a highly sensitive Snakes and many lizards use a highly sensitive

sense of smell to find prey and matessense of smell to find prey and mates Olfaction assisted by a Olfaction assisted by a Jacobson’s organ,Jacobson’s organ, a specialized a specialized

olfactory chamber in the roof of the moutholfactory chamber in the roof of the mouth



Video LinksVideo Links

Reptiles of AfricaReptiles of Africa

The four monophyletic nonavian The four monophyletic nonavian reptilian groups are:reptilian groups are:

TurtlesTurtles CrocodiliansCrocodilians SquamatesSquamates tuatarastuataras

26-21


26-22

Characteristics and Natural History of Reptilian OrdersCharacteristics and Natural History of Reptilian Orders

Turtles (Chelonia)Turtles (Chelonia) Shells consist of a dorsal Shells consist of a dorsal carapace carapace and a and a

ventral ventral plastronplastron Unique among vertebrates,Unique among vertebrates, limbs and limb girdles limbs and limb girdles

are located deep to the ribsare located deep to the ribs Lack teethLack teeth and use tough, horny plates for gripping and use tough, horny plates for gripping

foodfood Consequence of having a Consequence of having a rigid shellrigid shell

Turtle cannot expand chest to breatheTurtle cannot expand chest to breathe Solve problem by using abdominal and pectoral Solve problem by using abdominal and pectoral

muscles as a “diaphragm” muscles as a “diaphragm” Air is drawn in by contraction of the limb flank Air is drawn in by contraction of the limb flank

muscles, muscles, increasing abdominal cavity volumeincreasing abdominal cavity volume


26-23


26-24

Snapping Turtles Snapping Turtles Have a reduced shell that does not permit full Have a reduced shell that does not permit full

withdrawal of the bodywithdrawal of the body Jaws are adequate defenseJaws are adequate defense Entirely carnivorous and can eat fish, frogs, Entirely carnivorous and can eat fish, frogs,

waterfowl, etc.waterfowl, etc. Aquatic but must come ashore to lay eggsAquatic but must come ashore to lay eggs Loggerhead TurtlesLoggerhead Turtles



26-25


26-26

Squamates: Lizards and Snakes Squamates: Lizards and Snakes Account for up Account for up 95%95% of living nonavian reptiles of living nonavian reptiles Allowed evolution in lizards of a Allowed evolution in lizards of a mobile skull mobile skull

with movable jointswith movable joints,, a kinetic skull a kinetic skull Exceptional skull mobility of snakes is Exceptional skull mobility of snakes is

considered a major factor in their considered a major factor in their diversificationdiversification

Snake FakesSnake Fakes Jesus Christ LizardJesus Christ Lizard



26-27


26-28


26-29

Suborder Sauria: Lizards Suborder Sauria: Lizards Diverse group with terrestrial, burrowing, aquatic, Diverse group with terrestrial, burrowing, aquatic,

arboreal, and some aerial membersarboreal, and some aerial members LizardsLizards Geckos Geckos

Small, agile, nocturnal formsSmall, agile, nocturnal forms Adhesive toe pads allow them to walk on ceilingsAdhesive toe pads allow them to walk on ceilings

Iguanids Iguanids Include many New World lizards as well as the marine Include many New World lizards as well as the marine

iguana of the Galápagosiguana of the Galápagos ChameleonsChameleons

Arboreal lizards of Africa and MadagascarArboreal lizards of Africa and Madagascar Many have an extendible tongue Many have an extendible tongue



26-30


26-31


26-32

Some have degenerate limbsSome have degenerate limbs Glass lizards are nearly limblessGlass lizards are nearly limbless

Movable eyelidsMovable eyelids whereas snakes have a whereas snakes have a transparent coveringtransparent covering

Amphisbaenians or “worm lizards”Amphisbaenians or “worm lizards” highly highly specialized for a fossorial (burrowing lifespecialized for a fossorial (burrowing life



26-33


26-34

Conserve water by producing Conserve water by producing semisolid urinesemisolid urine with a high content of crystalline uric acidwith a high content of crystalline uric acid

Some can Some can store fat in tailsstore fat in tails to provide energy to provide energy and metabolic water during droughtand metabolic water during drought

Gila monster and beaded lizard are the only Gila monster and beaded lizard are the only lizards capable of a lizards capable of a venomous bitevenomous bite

Lizards keep body temperature relatively Lizards keep body temperature relatively constant by behavioral thermoregulation, constant by behavioral thermoregulation, although they are although they are ectothermsectotherms Successful strategy in ecosystems with low Successful strategy in ecosystems with low

productivity and warm climates, such as tropical productivity and warm climates, such as tropical deserts and grasslandsdeserts and grasslands



26-35


26-36


26-37

Suborder Serpentes: Snakes Suborder Serpentes: Snakes Limbless and have lost pectoral and pelvic Limbless and have lost pectoral and pelvic

girdles (except in pythons)girdles (except in pythons) Feeding apparatusFeeding apparatus allows them to eat prey allows them to eat prey

several times their own diameterseveral times their own diameter Two halves of lower jaw are loosely joined, Two halves of lower jaw are loosely joined,

allowing them to spread apartallowing them to spread apart Skull bones also loosely articulated so mouth can Skull bones also loosely articulated so mouth can

accommodate large preyaccommodate large prey To allow breathing during the slow process of To allow breathing during the slow process of

swallowing, the swallowing, the tracheal opening is extendedtracheal opening is extended Sidewinding snakeSidewinding snake



26-38


26-39

Eyeballs have reduced mobility and a Eyeballs have reduced mobility and a permanent corneal membranepermanent corneal membrane for protection for protection

Most have Most have poor visionpoor vision Arboreal snakes in tropical forests have highly Arboreal snakes in tropical forests have highly

developed visiondeveloped vision Lack external earsLack external ears and do not respond to and do not respond to

most aerial soundsmost aerial sounds Can Can feel vibrationsfeel vibrations at low frequencies, at low frequencies,

especially vibrations carried in the groundespecially vibrations carried in the ground Chemical sensesChemical senses rather than vision or rather than vision or

hearing are main senses used to hunt preyhearing are main senses used to hunt prey



26-40


26-41

Jacobson’s organs Jacobson’s organs Pair of pits in the roof of the mouthPair of pits in the roof of the mouth Lined with olfactory epitheliumLined with olfactory epithelium Forked tongue picks up scent particles and Forked tongue picks up scent particles and

conveys them to this organconveys them to this organ Nonvenomous snakes Nonvenomous snakes

Kill prey by constriction or by biting and Kill prey by constriction or by biting and swallowing swallowing

SkinSkin is infolded between scales is infolded between scales When stretched by a large meal, the skin is When stretched by a large meal, the skin is

unfoldedunfolded



26-42


26-43


26-44


26-45

Snakebite and ToxicitySnakebite and Toxicity NeurotoxinsNeurotoxins act on the nervous system, causing act on the nervous system, causing

blindness or inhibit respirationblindness or inhibit respiration Hemorrhagin typeHemorrhagin type venoms break down blood venoms break down blood

vessels vessels Blood leaks into tissue spacesBlood leaks into tissue spaces Sea snakes and the Australian tiger snakeSea snakes and the Australian tiger snake have have

the most deadly venom per unit volumethe most deadly venom per unit volume ReproductionReproduction

Most are oviparous and lay shelled eggs, pit Most are oviparous and lay shelled eggs, pit vipers are ovoviviparous, A few snakes are vipers are ovoviviparous, A few snakes are viviparous, having a primitive placenta to viviparous, having a primitive placenta to exchange nutrients with the youngexchange nutrients with the young

Female snakes can store sperm and lay several Female snakes can store sperm and lay several clutches of fertile eggs long after a single matingclutches of fertile eggs long after a single mating



26-46


26-47

The Tuatara The Tuatara Only 2 living speciesOnly 2 living species in New Zealand in New Zealand

represent this ancient lineage represent this ancient lineage Loss of the tuatara populations caused by Loss of the tuatara populations caused by

human human introduction of nonnative speciesintroduction of nonnative species which preyed upon the tuatarawhich preyed upon the tuatara Tuatara are vulnerable because they have Tuatara are vulnerable because they have slow slow

growth and reproductive ratesgrowth and reproductive rates

Lizard-like and live in burrowsLizard-like and live in burrows Slow growingSlow growing and may live to 77 years of age and may live to 77 years of age Well-developed Well-developed median parietal eyemedian parietal eye buried buried

beneath skinbeneath skin



26-48


26-49

Crocodilia: Crocodiles and Alligators Crocodilia: Crocodiles and Alligators

Modern crocodilians differ little from Modern crocodilians differ little from primitive crocodilians of the early Mesozoicprimitive crocodilians of the early Mesozoic

There are 3 families of modern crocodilians There are 3 families of modern crocodilians Alligators and caimansAlligators and caimans are found primarily in the are found primarily in the

New World and have a broader snoutNew World and have a broader snout CrocodilesCrocodiles are widely distributed are widely distributed One species of One species of gavialgavial occurs in India and Burma occurs in India and Burma

and has a very narrow snoutand has a very narrow snout



26-50


26-51

All have long, well-reinforced skull and jaw All have long, well-reinforced skull and jaw musculature for a powerful bitemusculature for a powerful bite

Theocodont dentitionTheocodont dentition Teeth are set in socketsTeeth are set in sockets

Have a Have a complete secondary palate,complete secondary palate, a feature a feature only shared with mammalsonly shared with mammals

Four-chambered heartFour-chambered heart Alligators and crocodiles are Alligators and crocodiles are oviparousoviparous

Usually 20–50 eggs are laid in mass of vegetationUsually 20–50 eggs are laid in mass of vegetation Unguarded nests are easily discovered and raided Unguarded nests are easily discovered and raided

by predatorsby predators High nest temperaturesHigh nest temperatures produce males produce males Low temperaturesLow temperatures produce females produce females Can result in females outnumbering males Can result in females outnumbering males 5 to 15 to 1


26-1 chapter 26 amniote origins and nonavian reptiles amniote origins and nonavian reptiles

Documents

temporal openings skull

mcgrawhill companies

traditional reptiles

mammals nonavian reptiles

leathery shell slide

birds skull

amniotic fluid

aquatic vertebrates