Herpetology

Lecture 12:

Typhlopidae (blindsnakes)

Uropeltidae (shield tails and earthsnakes)

Acrochorididae (filesnakes)

Bolyeridae (split-jaw snakes)

Pythonidae (pythons)

Boidae (true boas)

Xenopeltidae (sunbeam snakes)

Elapidae (elapids)

Colubridae (colubrids)

Viperidae (vipers)

Lecture 13:

Snake prey detection and handling process

Chemical and visual sensory methods

Forked tongues: Samples odors that are then detected by the Jacobson’s organ.
Some snakes, such as pit vipers, pythons, and boas, have infrared detectors that help them detect warmth.

Adaptations and prey detection in specific snakes

Rattlesnakes can detect prey through temperature changes in their tails.
The Jacobson’s organ is located above the secondary palate (the roof of the mouth).

Prey capture and strike mechanisms:

Snakes teeth curve backwards toward the digestive track to pull prey further in.
Snakes have highly kinetic skulls (they have barely any bone in their skulls) which allows them to jostle the prey around without causing too much damage.
Prey capture begins with the first strike which is when some snakes inject venom. They strike and do not let go.
The speed of snake strikes allows them to capture prey before they have time to react. They are just as fast or faster than their prey.
Snakes reach their prey in 15 to 90 milliseconds.

Q & A:

How do snakes detect prey? Chemical cues, visual cues, touch, and infrared heat detection.
How fast can a snake strike? 15 to 90 milliseconds.
What make snake teeth unique? Snake teeth are recurved, meaning they curve backwards towards the digestive tract which helps them grip the prey and pull them further into their mouths when they try to escape.
How do snakes use their tongues? They sample chemical cues in the environment. Their tongues collect odor particles and then they press it against their Jacobson’s organ in the roof of their mouth to analyze the chemical information.

Lecture 14:

Lecture goals

compare the evolutionary relatedness of crocs w/ other reptiles, amniotes,
tetrapods, etc
rank the three extant crocodilian families based on diversity
list and distinguish the two native crocs in the United States
explain how alligator farming might aid in conservation efforts of wild
populations
explain the function of the death roll in crocs
explain the evolution of narrow-snoutedness in an ecomorphological
context
describe trunk and limb and tail morphology in crocs and explain their
function
describe osteoderms in crocs and compare them to similar structures in
other reptiles
provide an adaptive explanation for the heart structure in crocs

3 Families

Morphology:

Skull: Crocodile skull is skinny/smushed while alligator skull is wider.
Teeth: Both have enlarged tooth near the front of lower jaw. Crocodiles tooth tends to protude more while alligator’s tooth is hidden (fits into a socket in the upper jaw).
Trunk: Alligators have broad, U-shaped snouts and crocodiles have narrow, V shaped snouts.
Limbs: Alligators have short limbs and webbed feet while crocodiles have long limbs and separated toes.
Tail: Alligators are taller than wider with tall crests of scales and crocodiles tails are flat on the sides with scales that stick up.
Osteoderms: Bony plates under the skin that serve as armor and aid in temperature regulation
Heart: Four-chambered heart with a special valve that allows them to shunt blood away from their lungs during conditions such as prolonged submersion.
Foramina: A hole that connects the left and right aorta in the heart.
Eyes: Nearly 270 degrees of vision, third eyelid (nictitating membrane) acts as “goggles”, retractable eyeball for protection, tapetum lucidum for enhanced night vision, and a horizontal fovea for scanning the shoreline.

New Hampshire taxa