Lepidosaurs Flashcards
Characteristics of Amphisbaenians digging lizards
- Integument characterized by annuli
- Integument not connected to trunk
- Integument forms tube in that allows the body to slide forwards or backwards inside
- Rigid skulls form tunneling
- Single median tooth in the upper jaw
- Nipper rips off small pieces of tissue
Characteristics of Lizards
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
Conflict between locomotion and respiration is avoided by whom and how
Varidae monitor lizards
Use positive pressure pump to assist axial muscles
As a result can sustain a large level of activity
Characteristics of Lepidosaurs
Skin covered by scales Four limbs, reduction of limbs, legless Transverse cloaca Shedding of skin Invertebral breakage zones
Characteristics of Sphenodontids
arboreal, terrestrial, marine
herbivores and insectivores
15-35 cm in length in Triassic
1.5 m in length in Cretaceous and Jurassic
Characteristics of Tutara
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
Describe the jaw and teeth shearing effect
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
Ancestral condition of Snakes
Represented by Scoecophidia
three families of burrowing snakes
vestigal pelvic girdle
brain case resembles most snakes
Important derived character of Squamates
determinate growth
max size limited
may be the result of insectivore diet
Two major lineages of Squamates
Iguania
Scleroglossa
Origin of Snakes
Evolved from subterrean lizards with reduced eyes
Surface dwelling redeveloped later
Eyes of snakes are different than lizards
Characteristics of Snakes
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.
Characteristics of Colubroidea
venomous
Chemosensation important for many species.
Tongue projected and waved in air or contact ground.
Chemicals transferred to vomeronasal organs.
Characteristics of Sea Snakes
50 marine species All marine species are venomous Tail flattened Feed primarily on fish. Ovoviviparous
Respiration of Sea Snakes
Nostrils located dorsally.
Single lung extends to cloaca.
Modified trachea.
Capable of cutaneous respiration.
Types of Snake locomotion
Rectilinear
Sidewiding
Concertina
Describe Snake locomotion
Lateral undulation.
“Serpentine” locomotion.
Body thrown into series of irregular curves
Rectilinear Locomotion
• Alternate sections of ventral integument are lifted and
pulled forward by muscles attached to ribs.
• Intervening section rest on ground and support body
Concertina Locomotion
- Posterior anchored by pressing loops against walls.
- Anterior extended.
- Anterior forms loops and posterior drawn forward.
Sidewinding Locomotion
• 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.
Characteristics of Solenoglyphous snakes for consuming
larger prey:
• 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.
Solenoglyphous
- Hollow fangs only teeth on maxillae.
- Fangs rotate against roof of mouth when jaws closed.
- Venom includes enzymes.
Proteroglyphous
- Hollow fangs at front of maxilla.
* Fangs short and permanently erect.
Opisthoglyphous
• One or more enlarged teeth at rear of maxilla.
• Teeth may be solid or with groove to conduct saliva into
wounds.
Snakes further increase kinesis by
• 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.
Describe snake feeding
• 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.
allow snakes to consume large prey without injury.
constriction and venom
Two hypotheses about what kills constricted prey
• Prey suffocates because it is unable to expand thorax
for inhalation.
• Increased internal body pressures interrupt and stop
heart from beating.
Morphological Specializations of Constrictors
• 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.
Benefit of venom capable of killing prey in snakes
allowed snakes to reduce need for constriction and
become specialized for rapid locomotion.
Purpose of Duvernoy’s gland
•capable of
producing toxins that immobilize prey.
• Homologous with venom glands.
• Ancestral character of one snake lineage
Three categories of venomous snakes
Opisthoglyphous, proteroglyphous, and solenoglyphous.
Foraging
- Changes in temporal fenestration.
- Loss of lower temporal bar and quadratojugal bone.
- Changes contribute to increasing skull kinesis.
- Complete lower temporal arch present.
Changes in Foraging
• 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.
