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• What makes up the Lepidosaurs?

  Tuatara, Lizards and Snakes
• What is determinate growth? Species

  Growth stops at some genetically determined point rather than continuing throughout an organism's life.

  Lizards and snakes
• How is the skin of Lepidosaurs?

  covered in scales (impermeable to water)- outer layer shed at intervals
• Do Lepidosaurs have limbs?

  4 limbs or complete loss of limbs (snakes).
• What is the sister lineage of Lepidosaurs? Habitat?

  Crocodiles and Birds

  Predominantly terrestrial (200 mybp)
• What is the sister lineage of Tuatara? Species?

  Lizards and snakes -- 1 species lives in New Zealand (60 cm height)
• Behavior of Tuatara?

  Nocturnal - Bask in sun during day --> Night activity due to feeding specializations- exploit food resources in bird colonies (dead, young birds and arthropods) easier to hunt at night.
• Why were Tuatara extirpated from mainland?

  Introduction of non-native species (cat, dog, rats, sheep, goats)
• What does the distribution of Tuatara looks like?

  Several small islands off the coast --> Rescued via introduction.
• What species are part of the Squamata?

  Lizards and snakes
• Lizards facts

  Diverse habitats (Swamp, deserts, beaches, forests, above timberline)

  Diverse feeding specializations

  4800 spp. many lineages
• Iguanidae (45 spp.)

  Part of Squamates

  Mainly Central South, North America

  Varying sizes - most large ones are herbivores and are arboreal
• Chameleonidae (219 spp.)

  Part of Squamates

  Mainly Africa, Madagascar

  Varying sizes - most arboreal

  Laterally flattened bodies

  Zygodactyl feet

  Prehensile tails

  Swivel eyes
• What are Zygodactyl feet?

  Grasping branches
• What are Prehensile tails?

  Grasping branches
• Gekkonidae (1433 spp.)

  Everywhere except Antarctica

  Small to medium-sized lizards (3-30 cm)

  Modified scales (setae) on bottom toes for climbing vertical surfaces

  Most Nocturnal
• Scincidae (1730 spp.)

  Everywhere except Antarctica

  Small to medium-sized lizards (10-40 cm)

  Mainly insectivorous, some herbivores

  Some have limb reduction
• Varandiae (84 spp.)

  Monitor lizards - small to very large

  Africa, Asia, East Indies, Australia

  Active predators (larger species have home ranges)

  Most are carnivorous
• How do Varanidae overcome lung ventilation/ respiration challenge?

  Use a positive pressure gular (throat) pump --> assists in lung ventilation to help axial muscles sustain high levels of activity.
• Komodo Dragons (84 spp.)

  World's largest Lizard

  Australia, East Indies, Asia and Africa

  Active predator

  Venomous

  Exhibit purposeful hunting behavior
• How are Komodo dragons different from other lizards but similar to snakes?

  Understand prey and geography of where prey forage - different than opportunistic seizure of prey of lizards
• How many times have limb reduction evolved?

  At least 60 times
• What is associated with reduction of limbs?

  Life in thick grass/shrubbery or habitat with small opening among rocks
• Amphisbaenians (204 spp.)

  Borrowers/ diggers

  Rigidly constructed skulls for tunneling

  often shovel-snouted

  Small (10 - 80 cm)

  West Indies, South America, Africa, Mediterranean
• Snakes (2900 spp.)

  Distinguished form lizards colloquially and morphologically but not phylogenetically

  Appeared to have evolved terrestrial environment (some marine now)

  Venomous species

  Jaw specializations

  • Small burrowing -- termite feeders
  • Large Constrictors -- active predators
• What protein is responsible for Legless in snakes?

  Sonic Hedgehog (Shh) protein - stimulate limb formation and controlled by regulatory protein ZRS --> mutation in ZRS gene in snakes reduces its activity and expression of Shh leading to suppression of limb formation.
• What do snake locomotor specializations depends on?

  Type of predation of the species and types of substrate inhabited
• Lateral Undulation

  Body is thrown into a series of curves - curves press backward (snake exerts force of substrate)
• Rectilinear locomotion – mainly used by heavy-bodied snakes

  Alternate sections of the body are lifted off the ground and pulled forward by rib muscles

  Moves slowly in a straight line

  Inconspicuous movement, so used when stalking prey
• Concertina locomotion – mainly used in narrow passages (e.g., rodent burrows) where lateral undulations are not possible

  Posterior part of body anchored with small loops pressed against wall; anterior part of body moved forward; anterior loops formed and anchored; posterior end moved forward
• Sidewinding locomotion–mainly used by desert snakes • Wind blowns and provides a substrate that slips away

  during lateral undulation

  • Body is raised in loops; force is exerted downwards

  • Body is extended nearly perpendicular to its line of travel, so effective only for small snakes that live in habitats with few plants or other obstacles
• What does diverse feeding specializactions Lead to?

  changes in structure of skull and jaws (evolution toward more rapid movemen)
• Compare to the ancestral (Tuatara) what is the skull of the lizard? Snake?

  derived - loss of lower bar

  derived - loss of lower bar and upper bar
• Squamate - Sit-and-wait’ predators

  • Lizards make short dashes from a perch to capture prey and return to perch, or

  • Snakes wait in ambush for prey to pass, some use lures

  • Have patterns of blotches that make them cryptic when they

  are motionless

  • High anaerobic metabolic capacities support short dashes to capture prey, but the metabolic substrates stored in muscles are quickly depleted. Hence, little ability to sustain locomotion

  • Lizards are often territorial
• Widely-foraging’ predators

  • Move nearly continuously

  • Some snakes are trapliners – routinely follow the same route

  and check sites where they have capture prey in the past

  • Elongated bodies and solid or striped patterns are cryptic when in motion

  • High aerobic metabolic capacities and better endurance than ‘sit-and-wait’ predators but slower sprint speeds

  • Rarely territorial
• How do squamate escape predators ?

  autotomy- self amputation of tail (Salamanders, tuatara, lizards, snakes, some rodents) freshly cut tails jerks like real prey

  cost: male social status and mating - female fat store
• Snake -Slow swallowing:

  Swallow prey head first thus pressing prey’s limbs out of the way

  Once prey reaches the esophagus, it is forced toward the stomach via contractions of the snake’s neck muscles
• Snake feeding specializations ?

  Slow swallowing

  struggling prey

  constriction

  venom
• How do snake deal with struggling prey?

  Extended frontal/parietal bones in the skull protect brain from kicks by prey
• In lizards, ’sit-and-wait’ species are territorial and use visual displays for intraspecific communication whereas ‘widely foraging’ species are rarely territorial and use olfaction for species and sex identification