LECTURE 21 - Reptilia: Archosauria and Testudines Flashcards
1
Q
(IN REPTILIA) What are Archosauria?
A
- Diapsids
- Laminae on vertebrate
- Extensive debate about the inclusion of Testudines in Archosauromorpha
2
Q
(IN REPTILIA - IN ARCHOSAURIA) What are Testudines?
A
- Turtles
- ~300 species
- Anapsids (no temporal fenestrae)
- Characterized by a shell composed of a carapace and plastron that completely encloses both limb girdles
- Generally opportunistic omnivores
- Most abundant in tropics, but also fairly diverse in temperate regions
3
Q
How did turtles get their shell?
A
- The carapace and plastron are formed by fused and structured bones, ribs, and vertebrae that enclose the shoulder and pelvic girdle
4
Q
What does shell variation depend on?
A
- Defense against predators
- Swimming performance
- Squeezing between rocks
5
Q
How do turtles protect their head?
A
- CRYTODIRA (“hidden neck”): contracting their necks under their spine
- PLEURODIRA (“side neck”): Contract their necks to the side
6
Q
Describe turtle jaws
A
- Last testudines with teeth lived about 150-200 million years ago
- Upper and lower jaws of modern turtles are covered in horny ridges to make a rigid beak
- Carnivorous turtles usually have sharp ridges for slicing prey, whereas herbivorous turtles often have serrated ridges for cutting through plants
7
Q
How do turtles breathe?
A
- Rigid shells cannot expand, so unable to breathe through expansion.contraction of ribs like other reptiles
- Instead breathe by abdominal contractions that pull and push on organs to change the internal volume of the shell and compress and expand the lungs
- Some species can also respire through their cloaca (anus)
8
Q
How do turtles move?
A
- Typically slow moving on land, but can be quite fast in the water
- Leg length and toe webbing vary based on habitat use
9
Q
How do turtles hibernate?
A
- Many turtles spend the winter trapped under ice and unable to breathe
- To retain function they undergo a ~160-fold reduction in metabolic rate
- Exploit the buffering capacity of their shells to neutralize the lactic acid that does accumulate
10
Q
In turtles, what does sex expression depend on?
A
- Temperature
- In some species, temperature determines whether an egg develops into a male or female
- High temperature = female, low temperature = male
- Potentially adaptive but mechanism not well understood
11
Q
At what rate have turtles evolves?
A
- Slow and steady
- Many turtle organs do not show clear signs of senescence
- e.g., the liver, lungs, and kidneys of 100 year old turtles have been found to show the same functional capacity as in immature turtles
- some species do not reach sexual maturity until their 40s
- Lineage is slowly evolving too - basic body plan has not changed in 200 million years, and genomic analyses suggest some species evolve at about 1/3 the evolutionary rate of humans
12
Q
(IN REPTILIA - IN ARCHOSAUROMORPHA - IN ARCHOSAURIA) What are Crocodylia?
A
- Diapsids
- 28 species in three families
- Predatory and semiaquatic
- Long flattened snouts, laterally compressed tails
- Eyes, ears, and nostrils on top of heads
- Thick skin with non-overlapping scales
- Four-chambered heart
13
Q
What are the main crocodilian groups?
A
- The order Crocodylia includes the “true” crocodiles (family Crocodylidae), the alligators and caimans (family Alligatoridae), and the gharial (family Gavialidae)
- Phylogenetic relationships among these groups have been debated, but most recent molecular studies placed the gharials and crocodiles as being more closely related to each other than with alligators and caimans
14
Q
How do Crocodilians optimize stealth?
A
- they use their diaphragm, pelvic, abdominal and rib muscles to shift their lung like internal floatation devices
- “periscope” senses
15
Q
Snout shape variation
A
CHECK SCREEN SHOT
