Lepidosauria

Question 1

• General characteristics of lepidosaurs (“scaly clade” )

Answer 1

• Triassic to recent
• Largest group of non-avian reptiles:
○ Tuataras - 1 living species
○ Lizards - 6,459 living species
○ Snakes - 3,619 living species
• Predominantly terrestrial
• Scaly skin relatively impermeable to water; sheds/molts
• Four limbs in many; limbless in others
• A diverse ecological history in the Mesozoic era, including many aquatic/marine forms

Question 2

skulls , skin

Answer 2

1. Diapsid skulls
   • Greater range of jaw and skull mobility, food habits, and feeding styles
   •
   
   2. Lack secondary palate (roof of mouth)
   3. Epidermal scales (cornified/hardened as in turtles)
   4. Skin is dry and non-glandular

Question 3

5. Vomeronasal organ (important)

Answer 3

• Jacobson’s organ
  
  • Passage from palate to mouth lined with olfactory epithelium
  • For additional smell - improves sense of smell
  • In adult squamates
  • In juvenile archosaurs (crocs; birds)

Question 4

growth? derived trait?

Answer 4

9. Determinate growth (growth stops at a certain size)
   • Long bones with a shaft
   ○ (diaphysis) and end (epiphysis)
   • Shaft ossifies whereas epiphysis are cartilaginous
   ○ Growth occurs at the ends of the long bones
   ○ Eventually the epiphysis ossify and fuse to the shaft - growth stops
   • A derived trait for lepidosaurs
   ○ Crocs and turtles have indeterminate growth (growing throughout life)

Question 5

• Lepidosaur clade 
	• Sphenodontids 
	• Squamates
		○ Lizards 
		○ Snakes

Answer 5

Question 6

describe sphenodontids

Answer 6

• Triassic to recent
  
  • Sister group to squamates
  • Sphenodont means “wedge tooth”
  • Found only on islands off new zealand
  • 1 extant species – sphenodon punctatus
  • Adults approx. 60 cm long
  • Nocturnal

Question 7

sphen jaw and teeth

Answer 7

• Quadrate fused to skull
• Primitive diapsid skull
Amphicoelous vertebrae ( hollow at both ends)
• Acrodont teeth
○ Lack roots; solidly attached to jaw bones; not replaceable
• Two rows of upper teeth, lower fit in between - scissor-like
• Feeds on arthropods and vertebrates (frogs, lizards, sea birds)

Question 8

sphen sensory and reproduction

Answer 8

• Pineal (median) eye 
		○ A photoreceptor located dorsally on the head 
		○ Used for thermoregulation 
		○ 
	• Lack eardrum 
	• Reproduction
	• Reproductive maturity at 10 years 
	• Males lack a copulatory organ 
	• Oviparous - lay eggs in a burrow 
Incubation period up to 15 months