Reptile Anatomy

Question 1

List the taxonomic terms used to classify reptiles commonly seen in practice.

Answer 1

4 orders: crocodilia, sphenodontia, squamata, testudines
Clinically important:
Squamata: snakes( serpentes), lizards( sauria)
Testudines/Chelonian in the UK:
Tortoise = terrestrial
Turtle = marine
Terrapin = freshwater

Question 2

What are some features of the lizards axial skeleton?

Answer 2

• 8 Cervical vertebrae
• 11-18 Trunk vertebrae ( ribs which wrap all the way round and gastralia)
• Variable caudal vertebrae

Question 3

What is a lizards anti defence mechanism?

Answer 3

Dropping their tails at the fracture planes which then thrashes about.

Question 4

What are some disadvantages to the lizards anti defence mechanism?

Answer 4

• Fat stores
• Divert energy
• Tail regrowth - different
• May affect locomotion, reproduction
• Less able to defend territory or fight other males

Question 5

What are some features of the snakes axial skeleton?

Answer 5

• 100-300 preocloacal vertebrae (all with very flexible ribs)
• 2-10 lumbar vertebrae (no ribs)
• 10-20 caudal vertebrae
• Special processes give vertebral column added stability (zygosphene and zygantrum)

Question 6

What are some features of the chelonian axial skeleton?

Answer 6

• Cervical vertebrae: 8
• Trunk/dorsal vertebrae: 10
• Trunk ribs
• Sacral vertebrae: 2
• Caudal vertebrae: <24 - Sex difference in number- males have more

Question 7

What are the two suborders of chelonian, based on neck type?

Answer 7

• Cryptodira (hidden neck) - retract neck= majority

- Pleurodira (side neck) - turn head to side = small suborder

Question 8

What are some features of the chelonian shell?

Answer 8

Chelonian shell = dermal and endochondral bone fused
carapace = top shell (49 bones)
plastron = bottom shell (9 bones)
- bones in shell (some paired, some unpaired) all named
- Shell covered with epidermal ‘scutes’- named for parts of body they’re adjacent to
- Seams of scutes and dermal bones in shells do not overlap (greater strength to shell); both can regenerate
- Blood and nerve supply to shell, shell has metabolically active bone (drug doses)

Question 9

Summarise the pectoral and pelvic girdles of snakes and lizards.

Answer 9

Lizard:
- Sternum - cartilage or bone not fully ossified
- Unpaired interclavicle (dermal bone)
- May have gastralia (dermal ribs)
Snake:
- No pectoral girdle
- No pelvic girdle (most), except boidae (pelvic remmants: spurs)

Question 10

Summarise the pectoral and pelvic girdles of chelonians.

Answer 10

• Both within ribcage

- Vertical orientation - greater stability - Ilium & scapula (or coracoid)