Lepidosaurs

Question 1

Characteristics of Amphisbaenians digging lizards

Answer 1

1. Integument characterized by annuli
2. Integument not connected to trunk
3. Integument forms tube in that allows the body to slide forwards or backwards inside
4. Rigid skulls form tunneling
5. Single median tooth in the upper jaw
6. Nipper rips off small pieces of tissue

Question 2

Characteristics of Lizards

Answer 2

Length of 3 cm to 3 m
More than 80% are less than 20 g and are insectivores
Large lizards are herbivores
Some have blunt heads, while others have a vertical or horizontally keeled snout
Have a conflict between respiration and locomotion
Legless has evolved over more than 60 times

Question 3

Conflict between locomotion and respiration is avoided by whom and how

Answer 3

Varidae monitor lizards
Use positive pressure pump to assist axial muscles
As a result can sustain a large level of activity

Question 4

Characteristics of Lepidosaurs

Answer 4

Skin covered by scales
Four limbs, reduction of limbs, legless
Transverse cloaca
Shedding of skin 
Invertebral breakage zones

Question 5

Characteristics of Sphenodontids

Answer 5

arboreal, terrestrial, marine
herbivores and insectivores
15-35 cm in length in Triassic
1.5 m in length in Cretaceous and Jurassic

Question 6

Characteristics of Tutara

Answer 6

Adults up to 60 cm in length
Nocturnal
Jaws and teeth cause sheering effect
Insectivores-as well as lizards, birds, frogs
Eat arthropods
Color change, vocalization, behavioral display used in social behavior
Nest with sea birds- 2-3cm separation in burrows
Can feed on birds
Don’t represent the ancestral condition

Question 7

Describe the jaw and teeth shearing effect

Answer 7

Upper jaw has two rows of teeth- maxilla and palatine bones
Lower jaw- teeth fit between spaces of of upper jaw teeth
Jaw closes vertically and followed by anterior sliding
Anterior sliding allows food to be bent or sheared by triangular cusps of jaw teeth

Question 8

Ancestral condition of Snakes

Answer 8

Represented by Scoecophidia
three families of burrowing snakes
vestigal pelvic girdle
brain case resembles most snakes

Question 9

Important derived character of Squamates

Answer 9

determinate growth
max size limited
may be the result of insectivore diet

Question 10

Two major lineages of Squamates

Answer 10

Iguania

Scleroglossa

Question 11

Origin of Snakes

Answer 11

Evolved from subterrean lizards with reduced eyes
Surface dwelling redeveloped later
Eyes of snakes are different than lizards

Question 12

Characteristics of Snakes

Answer 12

2/3 belong to Colubroidea.
   lost of pelvic girdle
   highly kinetic skull
   single cartoid artery 
• One lung reduced or absent.
• Gallbladder posterior to liver.
• Right kidney anterior to left kidney.
• Paired gonads may be displaced.

Question 13

Characteristics of Colubroidea

Answer 13

venomous
Chemosensation important for many species.
Tongue projected and waved in air or contact ground.
Chemicals transferred to vomeronasal organs.

Question 14

Characteristics of Sea Snakes

Answer 14

50 marine species
All marine species are venomous
Tail flattened
Feed primarily on fish.
Ovoviviparous

Question 15

Respiration of Sea Snakes

Answer 15

Nostrils located dorsally.
Single lung extends to cloaca.
Modified trachea.
Capable of cutaneous respiration.

Question 16

Types of Snake locomotion

Answer 16

Rectilinear
Sidewiding
Concertina

Question 17

Describe Snake locomotion

Answer 17

Lateral undulation.
“Serpentine” locomotion.
Body thrown into series of irregular curves

Question 18

Rectilinear Locomotion

Answer 18

• Alternate sections of ventral integument are lifted and
pulled forward by muscles attached to ribs.
• Intervening section rest on ground and support body

Question 19

Concertina Locomotion

Answer 19

• Posterior anchored by pressing loops against walls.
• Anterior extended.
• Anterior forms loops and posterior drawn forward.

Question 20

Sidewinding Locomotion

Answer 20

• Body raised in loops with two or three points in contact
with ground.
• Loops moved through air and points of contact move
smoothly along body.

Question 21

Characteristics of Solenoglyphous snakes for consuming

larger prey:

Answer 21

• Triangular head reflects outward extension of skull.
• Quadrates at rear of skull are wide-spread allowing large
objects to pass through mouth.
• Adaptations do not appear to inhibit locomotion.

Question 22

Solenoglyphous

Answer 22

• Hollow fangs only teeth on maxillae.
• Fangs rotate against roof of mouth when jaws closed.
• Venom includes enzymes.

Question 23

Proteroglyphous

Answer 23

• Hollow fangs at front of maxilla.

* Fangs short and permanently erect.

Question 24

Opisthoglyphous

Answer 24

• One or more enlarged teeth at rear of maxilla.
• Teeth may be solid or with groove to conduct saliva into
wounds.

Question 25

Snakes further increase kinesis by

Answer 25

• Loss of second temporal bar.
• Increasing flexibility of joints between bones of palate
and roof of skull.
• Skull has eight links with joints that allow rotation.
• Links are paired allowing each side of the skull to act
independently.
• Mandibles only attached by muscles and skin allowing
independent movement anteriorly and laterally.

Question 26

Describe snake feeding

Answer 26

• Snakes generally swallow prey head first to allow limbs to
press against body
• Mandibular and pterygoid teeth of one side of the head
anchor prey while head is rotated to advance opposite
jaw.
• After prey has reached esophagus, neck muscles contract
to move prey to stomach.
• Most snakes eat prey while it is still struggling.

Question 27

allow snakes to consume large prey without injury.

Answer 27

constriction and venom

Question 28

Two hypotheses about what kills constricted prey

Answer 28

• Prey suffocates because it is unable to expand thorax
for inhalation.
• Increased internal body pressures interrupt and stop
heart from beating.

Question 29

Morphological Specializations of Constrictors

Answer 29

• Tight loops made possible by having short vertebrae
and trunk muscles that only span a few vertebrae.
• Tradeoff is that specialization for tight loops limits speed
of locomotion.

Question 30

Benefit of venom capable of killing prey in snakes

Answer 30

allowed snakes to reduce need for constriction and

become specialized for rapid locomotion.

Question 31

Purpose of Duvernoy’s gland

Answer 31

•capable of
producing toxins that immobilize prey.
• Homologous with venom glands.
• Ancestral character of one snake lineage

Question 32

Three categories of venomous snakes

Answer 32

Opisthoglyphous, proteroglyphous, and solenoglyphous.

Question 33

Foraging

Answer 33

• Changes in temporal fenestration.
• Loss of lower temporal bar and quadratojugal bone.
• Changes contribute to increasing skull kinesis.
• Complete lower temporal arch present.

Question 34

Changes in Foraging

Answer 34

• Gap between quadrate and jugal widened.
• Suture between frontal and parietal bones became
straighter and more hinge-like.
• Quadrate became more mobile with development of
flexible connection between quadrate and squamosal.
• Condition called streptostyly.