LECTURE 20 - Reptilia: Lepidosauria Flashcards
1
Q
How did the amniotic egg influence terrestrial ecosystems?
A
- Sturdy eggs with amniotic fluid were critical for allowing amniotes to colonize and spread across the terrestrial globe
- They no longer needed to return to water for reproduction (like amphibians)
2
Q
(IN AMNIOTA) What are reptiles?
A
- Sauropsids that are not birds
- Paraphyletic: not a PHYLOGENETICALLY defensible classification
- No skin glands (little respiratory function)
- Epidermis with scales or scutes
- 3-chambered heart
- Ectotherms
3
Q
Describe the metabolism of reptiles
A
- the more body mass they have, the higher their metabolic rate is
- at around 27° in body temperature, they expend the most energy (in J)
4
Q
What is the earliest reptile?
A
- HYLONOMUS LYELLI
- Found in Nova Scotia in fossil tree stumps
- ~20 cm long and probably similar to modern lizards
- Apomorphies:
- single occipital condyle
- Toothed flange on pterygoid bone
5
Q
(IN AMNIOTA - IN REPTILIA) What are Lepidosauria?
A
- Diapsids
- Reptiles with overlapping scales
- Notched, protrusible tongue
- Transverse cloacal slits
- Males have hemipenes
- Tail regeneration
6
Q
(IN AMNIOTA - IN REPTILIA - IN LEPIDOSAURIA) What are Sphenodontia?
A
- Tuataras
- Endemic to New Zealand
- Retain many basal characteristics from the squamate-rhynchocephalian split ~240 million years ago
- Photosensory “third eye”
- Double rows of teeth in upper jaw
- Highly threatened by habitat loss and introduced predators
7
Q
What is the parietal eye?
A
- Parietal “third eye” is well-developed, with a lens and retina
- Visible as a translucent spot on the top of the head in juveniles, and covered by pigment and scales in adults
- Function not understood, but may be useful in producing vitamin D or determining circadian rhythm
8
Q
How are biting and chewing described in Sphenodontia?
A
- Wedge-shaped front teeth for biting
- Double rows of teeth in upper jaw which close on either side of a single row of teeth in the lower jaw to allow Tuataras to slice and chew prey
9
Q
How does diet change with age in Sphenodontia?
A
- Teeth cannot be replaced and eventually get worn down, so older individuals have to switch to softer prey
10
Q
How does diet change with age in Sphenodontia?
A
- Teeth cannot be replaced and eventually get worn down, so older individuals have to switch to softer prey
11
Q
(IN AMNIOTA - IN REPTILIA - IN LEPIDOSAURIA) What are Squamata?
A
- Largest order of reptiles (> 10,000 species)
- Scaly skin and movable quadrate bones
- Historically divided into three suborders: Lacertilia (lizards), Serpentes (snales), and Amphisbaenia (worm lizards)
12
Q
(IN REPTILIA - IN LEPIDOSAURIA - IN SQUAMATA) What are Lizards?
A
- Traditionally recognized as the suborder Lacertilia, and defined as extant members of Squamates that are neither snakes or amphisbaenians
- Distributed across all continents except Antarctica
- Over 6000 species
13
Q
What is caudal autonomy in lizards?
A
- “Self amputation” by shedding part of the tail structure
- Tail will continue to wriggle, which can distract the predator’s attention
- Partial tail regeneration is usually accomplished over a few weeks
- New tail section will contain cartilage rather than new vertebrae of bone
- Some lizards will return to a dropped tail and eat it to recover energy supplies
14
Q
Describe territoriality and sexual signalling in lizards
A
- Territoriality is common in lizards
- Signalling is used to attract mates and intimidate rivals
- Species-specific pattern of bobs and pushups
- Dewlap colours used in reproductive isolation
15
Q
What are some adaptive differentiation in Anolis lizards?
A
- Camouflage
- sticky-like structures on their footpads which allows them to walk up and down along vertical surfaces
16
Q
(IN REPTILIA - IN LEPIDOSAURIA - IN SQUAMATA) What are Amphisbaenians?
A
- “Worm lizards” are poorly understood other than their morphology
- ~180 species
- Widely distributed, occurring in North America, Europe, Africa, South America, and the Caribbean
- Limbless except Bipes (which retains forelimbs)
- Scales fused into rings (annuli) encircling the body
- Deeply recessed and poorly functioning eyes, and no outer ears
17
Q
What is special about the heads of Amphisbaenians?
A
- Skulls highly specialized as digging tools
- Highly specialized for fossorial life
- Burrow head-first with rigid and compact skull
- Shovel-headed
- Rounded-headed
- Keel-headed
18
Q
(IN REPTILIA - IN LEPIDOSAURIA - IN SQUAMATA) What are snakes?
A
- Suborder Serpentes
- ~3900 species
- Found on every continent except Antarctica
- No limbs, eyelids, or external ears
- Elongated body with 200+ vertebrae
19
Q
How are organs organized in snakes?
A
- Organ line up
- To accommodate their narrow bodies, paired organs are often arranged one after another rather than side by side
- Most snakes only possess one functional lung
20
Q
What is so special about the skull of snakes?
A
- Highly kinetic skull
- Tradeoff of power for flexibility
- Two lower jaws are not connected by bone but rather an elastic ligament, and can thereby move independently of each other
- Quadrate bone is articulated and not rigidly attached to the skull
- Neurocranium is fused and solid
21
Q
What is constriction in snakes?
A
- Most snakes using constriction lack venom
- They strike and hold on, then pull the prey into their coils
- Do not crush prey but rather hold tightly enough to cause asphyxia
22
Q
What are venomous snakes?
A
- Two main families of venomous snakes: Elapsids and Viperids
- Fangs are modified teeth on shortened maxillae
- Snake venom is typically prey-specific
23
Q
What is the venom made of in snakes?
A
- Modified saliva, and therefore a pre-digestant that initiates the breakdown of food in soluble compounds
- Complex mixture including proteins such as neurotoxins (attack the nervous system) and hemotoxins (attack the circulatory system), and enzymes that cause rapid diffusion
