Zoology – REPTILIAN GROUPS

THINGS YOU NEED TO KNOW FROM THIS CHAPTER…

1. In reptilian classification…
1. What makes a skull anapsid?

i. What are the only living anapsids?

2. What makes a skull diapsid?

i. Why is it considered a kinetic skull?

ii. To what Superorder do most modern reptiles belong to?

iii. What 3 animal groups belong in Order Squamata?

iv. What is the only member of Order Sphenodontida?

v. To what Superorder to Crocodylians belong?

vi. To what order do the Crocodylians belong?

3. What makes a skull synapsid?
1. What does amniote mean?
1. When did amniotes evolve?
2. What did they evolve from?
3. By the end of the Paleozoic Era, the amniotes diverged into what 3 animal groups?
2. Reptilian eggs
1. What is the shell like?
2. What is the amnion and what purpose does it serve?
3. What is the allantois and what purpose does it serve?
4. What is the chorion and what purpose does it serve?
3. Why is Class Reptilia a paraphyletic class?
1. How many species of reptiles inhabit the world? How many in the U.S.?
2. Which era is known as the Age of Reptiles?

i. What ended the dominion of dinosaurs (reptiles)?

5. Reptiles versus amphibians
1. What is reptilian skin like?

i. What are chormatophores?

ii. How are their scales different than fish scales?

iii. What are osteoderms?

2. How are reptilian juveniles different than amphibians?

i. What, more than anything else, allowed reptiles to conquer dry land?

3. How do reptiles process food differently than amphibians?
4. What type of fertilization do all reptiles have?
5. How is the reptilian heart (especially in crocodiles) more advanced than amphibians?

i. What are atria?

ii. What are ventricles?

iii. What is the systemic circuit?

iv. What is pulmonary circuit?

6. How do reptiles breathe differently than amphibians?

i. How do snakes and lizards suck air into their lungs?

ii. How do turtles and crocodiles suck air into their lungs?

iii. What respiratory structure (seen in mammals) is lacking in reptiles?

7. How do most reptiles stand and walk?
8. What brain structure is larger in reptiles?

i. What does a cerebral cortex allow for?

ii. What is the Jacobson’s organ?

6. What order do the turtles belong to?
1. Describe their shells.
2. How is their shell an advantage?
3. What does their shell hinder?
4. What is unique about their eating (compared to other reptiles)?
5. Why are turtles virtually mute?
6. How is the sex of their embryos determined?
7. What suborder do the lizards belong to?
1. List 4 examples of lizards.
2. How are they different than snakes?
3. What’s unique about the tails of some lizards?
4. List the 2 venomous lizards.
5. What does ectothermic mean?
8. What suborder do the worm lizards belong to?
1. What do they look like?
9. What suborder do the snakes belong to?
1. What is strange about pythons?
2. What is unique about their eating?
3. What is the glottis?
4. What is the main sense that snakes use to hunt?
5. Give 4 examples of snake locomotion. What is each suited for?
6. What are 3 hunting strategies employed by snakes?
7. What snakes belong to Family Viperidae?

i. What are pit vipers?

8. What snakes belong to Family Elapidae?
9. What snakes belong do Family Hydrophiidae?
10. What snakes belong to Family Colubridae?
11. What do neurotoxins in venom do?
12. What do Hemorrhagin toxins in venom do?
13. What is the LD₅₀?
9. What animals belong to Order Sphenodontida?
1. Where do you find them?
2. What do they look like?
10. What 3 animals belong to Order Crocodylia?
1. How could you tell them apart?
2. What does thecodont mean?
3. How is their heart different than other reptiles?
4. How is the sex of their embryos determined?
5. Do they show parental care to their offspring?

CLASSIFICATION OF EXTANT REPTILES

Phylum Chordata

Class Reptilia

Subclass Anapsida – skull with no temporal openings

Order Testudines – turtles

Subclass Diapsida – skull with two temporal openings

Superorder Archosauria – includes advanced diapsids,

some specialized for flight

Order Crocodylia – Crocodylians

Superorder Lepidosauria – sprawling posture, never

bipedal

Order Sphenodontida (or Rhynchocephalia) –

Tuataras with two extant species

Order Squamata – skin with horny epidermal scales

(or plates) that is shed

Suborder Sauria (or Lacertilia) – lizards

Suborder Serpentes – snakes

Suborder Amphisbaenia – worm lizards

I. Origin and Adaptive Radiation of Reptilian Groups

A. Recall that amphibians are semi-aquatic vertebrates.

1. Any animal with a shell-less egg remains tied to water.

B. What are amniotes?

1. _________________________ – innermost of the

extraembryonic membranes forming a fluid-filled sac around the

embryo in amniotes.

2. Amniotes include _____________________, ______________,

and _________________________.

3. Embryos develop within an “amniotic pond.”

4. These animals are free to become truly terrestrial.

C. History of amniotes

1. Amniotes arose from _________________________-like

tetrapods, the anthracosaurs, during the

_________________________ period.

2. By the late Carboniferous, amniotes had separated into three

Lineages, based upon skull anatomy.

a. _________________________ have a skull with no

temporal opening behind the orbits.

1) Modern _________________________ are

anaspids.

b. _________________________ gave rise to all other

reptilian groups and to the birds.

1) The diapsid skull has two temporal openings;

a) one pair below the cheeks

b) one pair above the cheeks.

2) _________________________ include

ichthyosaurs and most modern reptiles.

3) The more derived _________________________

included dinosaurs, living Crocodylians, and birds.

c. _________________________ are mammal-like reptiles

with a single pair of temporal openings.

D. Reptiles were the first vertebrates to become truly terrestrial and

exploit land habitats.

1. Reptiles lay porous, parchment-like, or leathery shelled eggs.

2. Within in the egg are membranes that provide complete support

for embryonic development.

a. The _________________________ encloses the “pond”

in which the developing embryo floats.

b. The _________________________ serves both as a

respiratory surface and a as a chamber to store nitrogenous

wastes.

c. The _________________________ encloses the other

two membranes.

1) It allows oxygen and carbon dioxide to freely pass.

3. Before the end of the Paleozoic Era, the amniotes diverged into

reptilian groups, birds and mammals.

E. Reptilian Diversity

1. Class Reptilian is a _________________________ class

because it excludes ________________, which have a most recent

common ancestor.

2. Nearly _________________________ reptilian species are

described.

a. About 340 occur in the United States and Canada.

3. The _________________________ Era is known as the Age of

Reptiles. It lasted over _________________________ years.

Dinosaurs reached their climax at the end of this era.

4. A mass extinction occurred at the end of the Mesozoic Era.

a. Modern reptiles represent surviving lineages.

5. Lizards and snakes radiated into diverse and abundant groups.

6. The tuataras of New Zealand are the sole survivor of a group

that otherwise disappeared 100 million years ago.

II. Characteristics Distinguishing Reptiles from Amphibians

A. Skin

1. Reptiles have a tough, dry, scaly skin.

a. Skin protects them from _________________________

and injury.

b. The thin epidermis is shed periodically.

c. A thicker, well-developed dermis underneath has

_________________________ that provide color.

3. Reptile scales are primarily of _________________________.

a. Reptile scales form from _________________________.

b. They are not homologous with fish scales (which were

dermal in origin).

4. Turtles add new layers of keratin underneath old layers of plate-

like _________________________.

5. Crocodiles and many lizards have bony plates called

_________________________ underneath the keratinized scale.

B. Shelled Egg

1. A shelled egg contains food and protective membranes to

support embryonic development on land.

a. Reptiles lay eggs on land.

b. Young hatch as lung-breathing juveniles, not as aquatic

larvae.

2. More than any other adaptation, this contributed to the

evolutionary establishment of reptiles.

C. Reptilian Jaws

1. The jaws of fish allowed fast jaw closure to seize food but little

force for chewing.

a. Recall that fish would suffocate if they chew because this

would block water flow over their gills.

2. In reptiles, jaw muscles became larger and arranged for the

mechanics of chewing.

D. Internal Fertilization

1. A shelled egg requires internal fertilization.

a. The sperm must reach the egg before it is enclosed.

2. Reptiles must, therefore, have some form of

__________________________________________________.

E. Circulatory System Modifications

1. Reptiles have an efficient circulatory system and higher blood

pressure than amphibians.

2. The _________________________ that receives deoxygenated

blood (_________________________ blood) is completely

partitioned from the _________________________ that receives

oxygenated blood (_________________________ blood).

3. Most reptiles have an incompletely separated ventricle but little

mixture of blood occurs.

a. The effect is two functionally separate circulations.

4. Crocodylians are more advanced and have separated ventricles

(they have a _________________________ heart).

a. This completely divides pulmonary and systemic

circulation.

b. There is no mixture of deoxygenated & oxygenated

blood.

c. This is the most efficient reptilian heart.

F. Lungs

1. Reptile lungs are better developed than those of amphibians.

2. Reptiles depend almost exclusively on __________________.

a. Reptiles have abandoned cutaneous breathing, which

was so common in amphibians.

b. Some aquatic turtles supplement lung breathing with

pharyngeal membranes.

3. Amphibians force air into their lungs with mouth muscles.

4. Reptiles suck air into lungs by enlarging the thoracic cavity.

a. Snakes and lizards expand their rib cage.

b. Turtles and crocodiles move internal organs.

5. Reptiles do NOT have a muscular diaphragm.

a. This structure is found only in mammals.

G. Water Conservation

1. All amniotes have a _________________________ kidney

drained by the _________________________.

2. Nitrogenous wastes are excreted as

_________________________ rather than urea or ammonia.

a. Uric acid has low solubility and precipitates readily; this

allows water to be conserved.

H. Support of Limbs for Locomotion

1. Except for limbless members, all reptiles have better body

support than amphibians.

2. Many modern reptiles still walk with legs

__________________________________________________ and

the belly close to the ground.

3. Most dinosaurs and some modern lizards have more efficient

legs directed beneath the body.

I. Nervous System

1. The reptilian nervous system is considerably more complex than

the amphibian.

2. The reptile brain is still small but the

_________________________ is relatively larger.

3. Crocodylians have the first true _________________________.

a. It allows complex behaviors not seen in amphibians.

4. Sense organs are generally well developed, except for hearing.

5. The _________________________ organ is highly developed in

lizards and snakes to detect odors carried by the tongue.

III. Characteristics and Natural History of Reptilian Orders

A. Anapsid Reptiles: Subclass Anapsida

1. Order _________________________ (Chelonia) includes the

turtles.

a. Turtles appeared in the Upper Triassic Period, 200

million years ago.

b. They have changed very little.

2. They are enclosed in shells consisting of a dorsal

_________________________ and a ventral

_________________________.

a. The shell is composed of two layers.

1) The outer horny layer is made up of keratin.

2) The inner layer is made up of bone.

b. The bony layer is a fusion of ribs, vertebrae, and dermally-

ossified elements.

c. Limbs and limb girdles are located inside the ribs!

d. Head and appendages can be drawn into the shell for

protection.

3. Turtles lack teeth and have tough, horny plates for gripping food.

4. Breathing

a. One consequence of having a rigid shell is that the turtle

cannot expand its chest to breathe.

b. Turtles solve this problem by using abdominal and

pectoral muscles as a “diaphragm.”

c. Both inhalation and exhalation is active.

5. Nervous system and sense organs.

a. Turtles have small brains, but can learn a maze as fast as

a rat.

b. They have acute senses of sight and smell, but poor

perception of sound.

1) Turtles are virtually mute.

2) Many tortoises roar or grunt only during mating.

6. All turtles bury their eggs in the ground.

a. Temperature determines embryo sex.

b. Low temperatures produce ______________________.

c. High temperature produce _______________________.

7. They have low metabolism and extreme longevity.

a. It is known that some turtles are older than 150 years.

B. Diapsid Reptiles: Subclass Diapsida

1. Order _________________________: Crocodiles and Alligators

a. Modern Crocodylians are the only surviving reptiles of the

archosaurian lineage.

1) This lineage gave rise to the Mesozoic radiation

of dinosaurs and to birds.

c. Modern Crocodylians differ little from primitive

Crocodylians of the early Mesozoic.

d. Modern Crocodylians are classified in three families.

1) Family _________________________ - 4 genera, 8

species

a) Alligators and caimans are found primarily in

the New World.

b) Alligators have a generally broader snout

than crocodiles.

c) When their mouths are closed, the 4^th lower

jaw tooth fits into a notch in the upper jaw and

is hidden.

d) Alligator mississippiensis is the only species

in the U.S.

2) Family _________________________ - 3 genera,

14 species

a) Crocodiles are widely distributed and include

the huge saltwater crocodile.

b) Crocodiles have a relatively narrow snout.

c) When their mouths are closed, the 4^th lower

jaw tooth is visible.

d) Crocodylus acutus, the only U.S. species, is

restricted to extreme southern Florida.

3) Family _________________________ - 1 genus,

1 species

a) The gavial occurs in India and Burma.

b) It has a very narrow snout.

e. All have a long, well-reinforced skull and jaw musculature

for a powerful bite.

1) Crocodylians are _________________________ –

their teeth are set in sockets.

f. They also share a four-chambered heart with birds and

mammals.

g. Alligators and crocodiles are oviparous; usually 20-50

eggs are laid in a mass of vegetation.

1) Nests left unguarded are easily discovered and

raided by predators.

2) High nest temperatures produce ______________.

3) Low temperatures produce _________________.

4) This can result in females outnumbering males five

to one.

2. Order _________________________ (Rhynchocephalia): The

Tuatara

a. Only two living species in New Zealand represent this

ancient lineage.

b. They are lizard-like and live in burrows often shared with

petrels.

c. The tuatara is slow growing and may live to 77 years of

age.

d. Its skull is nearly identical to diapsid skulls of 200 million

years ago.

3. Order _________________________: Lizards, Snakes and

Worm Lizards

a. Squamates are the most recent and diverse of diaspids;

1) They make up _____________ of living reptiles.

b. Lizards appeared in the fossil record in the Permian but

did not radiate until the Cretaceous.

c. Snakes appeared in the late Cretaceous from a group

whose descendants include monitor lizards.

1) Snakes gained specializations for losing their legs

and therefore for engulfing large prey.

2) Exceptional skull mobility of snakes is considered

a major factor in their diversification.

d. Diaspid skulls have lost dermal bone ventral and posterior

to the lower temporal opening.

e. This allowed evolution in lizards of a mobile skull with

movable joints, a _________________________ skull.

1) These skulls allow squamates to seize and

manipulate prey, and effectively close the jaw with

force.

f. Viviparity

1) Viviparity in reptiles is limited to squamates.

2) It is association with cold climates.

3) Viviparity involves increasing the length of time

eggs are kept in the oviduct.

4) Young obtain nutrition from yolk sacs or via the

mother, or a combination of both.

4. Suborder _________________________ (or Lacertilia):

Lizards

a. Lizards are a diverse group with terrestrial, burrowing,

aquatic, arboreal, and some aerial members.

1) _________________________ – adhesive toe

pads enable them to walk upside down and on

vertical surfaces.

2) _________________________ – includes most

familiar New World lizards and marine iguana of the

Galapagos Islands.

3) _________________________ – elongate bodies

with reduced limbs

4) _________________________ – arboreal lizards

with sticky-tipped tongues for catching insects (they

are _________________________)

b. Lizards have movable eyelids whereas snakes have a

transparent covering.

c. Lizards have an external ear that snakes lack.

d. Lizards conserve water by producing semisolid urine with

a high content of crystalline uric acid.

e. Some lizards can store fat in their tails to provide energy

and metabolic water during drought.

f. The ________________________________ and

_______________________________ are the only lizards

capable of a venomous bite.

g. Lizards keep their body temperature relatively constant by

behavioral thermoregulation (they are

_________________________).

5. Suborder _________________________: Snakes

a. Snakes are limbless and have lost the pectoral and pelvic

girdles (except in _________________________).

b. The many vertebrae are shorter and wider than in other

tetrapods, allowing undulation.

c. The feeding apparatus allows them to eat prey several

times their own diameter.

1) The two halves of the lower jaw are loosely joined,

allowing them to spread apart.

2) To keep breathing during the slow process of

swallowing, the tracheal opening

(_________________________) is extended.

d. Eyeballs have reduced mobility and a permanent corneal

membrane for protection.

1) Most snakes have poor vision but arboreal snakes

in tropical forests have highly developed vision.

e. Snakes lack external ears and do not respond to most

aerial sounds.

f. Snakes can feel vibrations at low frequencies, especially

vibrations carried in the ground.

g. Chemical senses rather than vision or hearing, are the

main senses snakes use to hunt prey.

1) Jacobson’s organs are a pair of pits in the roof of

the mouth; they are lined with olfactory epithelium and

the forked tongue picks up scent particles and

conveys them past this organ.

h. Snake Locomotion – How do you move without limbs?

1) _________________________________________

is the S-shaped movement that pushes against rough

ground and water.

2) _________________________________________

is extension of S-shaped loops to move in a narrow

passage as in climbing trees or striking.

3) _________________________________________

is a straight movement using minute lifting of

consecutive ribs.

a) A slow but effective way to move

inconspicuously toward prey.

4) _________________________________________

is a sideways looping by desert vipers that “walks”

them across loose sand.

i. Hunting

1) Most snakes actively forage, grasp, and swallow

live prey.

a) Feed upon worms, insects, fish, frogs, and,

infrequently, small mammals.

2) _________________________ are ambush

predators that specialize in large mammalian prey.

3) Venomous snakes

(_________________________of all snakes) kill their

prey before swallowing.

a) They are divided into 5 families, based

partly on fang type.

b) Of an average of 8,000 snake bites each

year in the U.S., only about 12 result in death.

j. Venomous Snakes

1) Family _________________________ – Viper

fangs are hollow and hinged to inject venom when the

snake strikes. The fangs lie within a membrane

sheath when the mouth is closed.

a) New World pit vipers – e.g. _____________,

_________________, ___________________

i) Pit vipers have “pits” with nerve

endings sensitive to heat emitted by

warm-bodied birds and mammals.

b) Old World true vipers – e.g. European adder

and African puff adder.

2) Family _________________________ – short,

permanently erect fangs in the front of their mouth.

a) Includes cobras, mambas, coral snakes,

and kraits.

3) Family _________________________ – highly

venmous sea snakes.

4) Family _________________________ – most

familiar (and nonvenomous) snakes includes a few

venomous snakes

a) The African boomslang and African twig

snake are rear-fanged and their bite can be

fatal to humans.

k. Snakebite and Toxicity

1) Most snake venoms are a complex combination of

venom types.

2) _________________________ act on the nervous

system, causing blindness or stopping respiration.

3) _________________________ type venoms broke

down blood vessels; much blood is leaked into tissue

spaces.

a) Tissues deprived of oxygen begin to die.

4) Toxicity is measured by the median lethal dose on

laboratory animals, called the __________________.

a) LD₅₀ is the dose that kills 50% of the

lab animals.

5) Sea snakes and the Australian tiger snake have

the most deadly venom per unit.

6) Large venomous snakes deliver more venom; a

king cobra may be the most dangerous snake on

earth.

7) The world total for deaths from snakebite is

estimated to be between 50,000 and 60,000 each

year.

l. Reproduction

1) Most snakes are _________________________

and lay shelled eggs under logs or rocks or in holes in

the ground.

2) Others, including pit vipers, are

_________________________.

3) A few snakes are _________________________,

having a primitive placenta to exchange nutrients with

the young.

4) Snakes can store sperm and lay several clutches

of fertile eggs long after a single mating.

6. Suborder _________________________: Worm Lizards

a. They are burrowing animals that mostly lack any trace of

external limbs.

b. The eyes and ears are rudimentary and hidden under the

skin; they resemble _________________________.

1) This is an example of

_________________________ evolution.

2) Both animals occupy similar habitats and thus

evolved similar structures.

c. One species occurs in Florida but most live in South

America and tropical Africa.