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Animal Diversity > Amniote origins and Lepidosauria (Tuataras and Squamata) > Flashcards

Amniote origins and Lepidosauria (Tuataras and Squamata) Flashcards

1
Q

Amniote Origins and Diversification

A
  • Tetrapods that are NOT amphibians
    Why/how did they evolve??
  • Late carboniferous; 312 mya
  • Via Anthracosaurs (Reptilliomorphs)
    2 early diversifications:
  • *Synapsids (to mammals)
  • *Sauropsids -> *Diapsids (to reptiles & birds)
    The Mesozoic was “The Age of Reptiles”
  • Dinosaurs!
    Truly terrestrial
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2
Q

The Early Split

A
  • *Synapsids (mammals) & *Sauropsids (birds/reptiles)
  • Diverged very early in Amniote evolution (312-306 mya)
    - e.g. *Protoclepsydrops (early fossil synapsid - 1st known?) & *Paleothyris (early sauropsid) both from Joggins Fossil cliffs in NS!
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3
Q

Amniotes Synapomorphies

A
  1. Amniotic egg
  2. Thicker and more waterproof skin
  3. Rib ventilation of the lungs
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4
Q

Enclosing “the Pond”

A
  1. The *amnion is an *extraembryonic membrane that encloses a *fluid-filled cavity – i.e., *“the pond”
  2. Embryonic development occurs in the *amnion (larger & faster too)
  3. Most evolved a *shelled egg that did not depend on water!!
    - *Protective & *semipermeable, (allows gasses, limits water loss)
  4. Paleozoic amniote diversification gave rise to all *nonavian reptiles, birds, & mammals
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5
Q
  1. Amniotic Egg
A
  • All amniotes have eggs with *4 extraembryonic membranes
    1. *Chorion (O2/CO2)
    2. * Allantois (O2/CO2, waste)
    3. *Amnion (fluid, cushion)
    4. *Yolk sac (food)
  • Better protection & nourishment
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6
Q
  1. Thicker & More Waterproof Skin
A
  • Mostly gas-proof; cannot breathe through the skin
  • Keratinized (scales, hair, feathers, claws…)
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7
Q
  1. Rib Ventilation of the Lungs
A
  1. Anamniote: “Mouth breather”
    - Mouth/throat muscular contraction & expansion
    - *Pushing air into lungs
    - *Positive pressure ventilation
  2. Amniote: Aspiration
    - Rib/muscular contraction & expansion
    - *Sucking air into lungs
    - *Negative pressure ventilation
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8
Q
  1. Jaws
A
  • Jaws efficiently designed for applying *crushing or gripping force to prey
  • Move from fast closure/suction feeding to *large muscles to grip and chew
  • E.g., Pliosaurs!
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9
Q

Skulls: Holes for Jaw Musculature

A

*Anapsids (ancestral)
- Have a skull with *no temporal opening behind the orbits
- E.g. ancestral, and secondarily derived in turtles (truly diapsids)

*Diapsids
- Skull has “two pairs of temporal opening (fenestra)
- one pair below the cheeks and another above
- Gave rise to all other traditional “reptiles” and to birds
- e.g., dinosaurs, snakes, lizards, crocodiles
- Turtles appear anapsid, but secondarily lost diapsid condition

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10
Q

Amniotes Synapomorphies

A
  1. Amniotic egg
  2. Thicker and more waterproof skin
  3. Rib ventilation of the lungs
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11
Q
  1. Thicker and More Waterproof Skin
A
  • Mostly gas-proof; Cannot breath through the skin
  • Karatinised (scales, hair, feathers, claws)
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12
Q
  1. Rib Ventilation of the Lungs
A

Anamniote: “Mouth breather”
- Mouth/throat muscular contraction and expansion
- Pushing air into lungs
- Positive pressure ventilation
Amniote: Aspiration
- Rib/muscular contraction & expansion
- Sucking air into lungs
- Negative pressure ventilation

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13
Q

Anamniotes vs Amniotes

A
  1. Jaws Efficiently Designed for Applying Crushing or Gripping Force to Prey
    - Move from fast closure/suction feeding to large muscles to grip and chew
    - e.g., Pliosaurs
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14
Q

Skulls: Holes for Jaw Musculature

A
  1. Anapsid skull (ancestral)
    - Skull with no temporal opening behind orbits
    - E.g., ancestral; secondarily derived in turtles (lost diapsid condition)
  2. Synapsid skull
    - Single pair of temporal openings (fesetra)
    - E.g., Mammals & early mammal-like reptiles
  3. Diapsid skull
    - Two pairs of temporal openings (fenestra)
    - Gave rise to all other “reptiles” and birds
    - E.g., dinosaurs, snakes, lizards, crocodiles
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15
Q
  1. Efficient and versatile Circulatory System (4-chambered heart)
A

Amphibian: 3-chambered heart
Amniote: 4-chambered heart
- Incomplete ventricle separation in some “reptiles” is handy for hibernation (winter) or estivation (summer)

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16
Q
  1. Efficient Strategies for Water Conservation (Uric Acid, Salt Glands)
A

Kidneys and urinary bladder adaptive for life on land
- Water mostly reabsorbed
- Mammals; kidney most efficient; urine made of urea
- “Reptiles” & birds: urine voided as semi-solid paste of uric acid
- Some reptiles need to excrete salt via salt glands!

17
Q

Salt Glands (“Reptiles”)

A
  1. Nasal glands:
    - Lizards (also marine birds); under nasal passage/above orbit
  2. Salivary gland
    - sea snakes, under tongue
  3. Lacrimal gland
    - sea turtles; tear ducts
  4. Lingual gland
    - crocodiles; on tongue
18
Q
  1. A more Complex Nervous System
A

“Lizard brain”: Bigger cerebrum and cerebellum
- Better integration of sensory info & control of muscles
- Some lizards and snakes can “see” UV and infrared lights
- Lizards and snakes have Jacobsone’s organ
- Olfactory in the roof of mouth transmitted from the tongue

19
Q

Classification of Non-Avian “Reptiles”

A

Diapsida
- Lepidosauria
- Squamata (snakes + lizards)
- Sphenodonta (Tuatara)
- Testudines (Turtles)
- Archosauria
- Crocodilia
- Dinosaurs, led to birds

20
Q

Lepidosaur Synapomorphies:

A
  1. Overlapping keratinous scales (from epidermis)
  2. Transverse cloacal slit (longitudinal in the other tetrapods)
  3. Automise tails (may or may not grow back)
21
Q

Clade Sphanodonta (AKA Rhynchocephalia)

A
  • Tuataras
  • 200 mya
  • “Living Fossil”
  • 1 remnant sp (Sphenodon punctatus)
  • Lizard-like, with no external ears
  • New Zealand; lives in burrows
  • Slow growing: may live to 77 yrs
  • Skull is nearly identical to diapsid skulls of 200 mya!!
  • A well-developed media parietal/pineal eye buried beneath its skin, function is unknown
22
Q

Order Squamata

A
  • “Lizards” & snakes
  • 95% of living reptiles
  • Diapsid skull mods
  • Lazard fossils in Permian; radiated in Cretaceous
  • Snake fossils in Jurassic; highly modified
  • Synapomorphy:
    • Males with hemipenes (Bilateral penis; only one used is copulation)
23
Q

Squamata Skulls: Diapsis w. Lost Bone(s)

A
  • Permitting evolution of the mobile kinetic skull with moveable joints
  • Joints in the palate and across the roof of the skull permit the snout to be tilted up
  • Squamates seize and manipulate prey; they close the jaw with force
  • Flexible Braincase
  • Extreme skull mobility of snakes lead to major diversification!
24
Q

Order Squamata -> “Lizards”

A

Typical “Lizards”
- 7000+ spp.
- Small, mostly insectivores, mods for climbers, some legless
- Moveable eyelids
- External ear openings
- Hot & dry regions
- Ectothermic
- e.g., geckos, iguanids, skinks, monitors, chameleons, glass lizards, worm lizards

25
Q

“Lizards” -> Geckos

A
  1. Geckos
    ~1500 spp; small & agile
    - usually nocturnal; excellent night/colour binocular vision; vocal
    - Climbers
    • adhesive toe pads covered in micro hairs
    • Can even walk on ceilings!
26
Q

“Lizards” -> Iguanids

A
  1. Iguanids
    ~700 spp.
    - Include many New World lizards as well as the only marine lizards (Galapagos)
    - Small scales, crest on back and tail (elongated scales), large dewlap
27
Q

“Lizards” -> Chameleons

A
  1. Chameleons
    - 150+ spp.
    - Arboreal (climbing) lizards of Africa and Madagascar
    - Many have projectile tongues
    - Zygodactylous feet, prehensile tail, binocular vision, colour change
28
Q

“Lizards” -> Skinks

A
  1. Skinks
    - 1500+ species
    - No visible neck
    - Smooth shiny scales
    - Small legs (sometimes lost)
29
Q

Squamate Lizards

A
  • Monitor Lizards
    ~80 spp.
  • The only venomous lizrds
  • Typically large and carnivorous
    • e.g., Komodo dragon: largest lizard
  • Thought most closely related to snakes
30
Q

Order Squamata -> Suborder Serpentes

A

~4000+ spp.; the snakes (extreme modified squamates)!
- Evolved in the Cretaceous from burrowing lizards
- Limbless
- No pectoral or pelvic girdles, short wide vertebrae (undulatory), many ribs (Columnal rigidity/lateral stress)
- No eyelids (Clear scale cover), no external ears
- How to eat without limbs?: Venom, teeth, a crazy kinetic skull, and construction

31
Q

Snake Skull and jaws

A
  • Bones not all connected
  • Kinetic skull!
32
Q

Sensory Systems

A
  • Most have poor vision
    • except tree snakes (binocular vision)
  • No external ears
  • Unique sensing organs!
    • e.g., Jacobson’s organ (olfactory via forked tongue)
    • e.g., temperature-sensing pit organs (pit vipers, pythons, rattlesnakes)
33
Q

A Nasty Bite

A

Most snakes are venomous
- **Poisonous = inhaled or ingested
- **Venom = injected
Injected in modified saliva through fangs
- Hollow or grooved
- Primary for predation; self-defense secondary

34
Q

The “Deadliest” snake

A
  1. Inland Taipan (AKA “Fierce Snake”)
    - Central East America
    - Based on unit of venom (single drop = kill 100 humans)
    - rarely bites - minimal human deaths!
  2. Saw-Scaled Viper
    - Africa, Middle East, Sri Lanka, Pakistan
    - V. aggressive, more deaths/yr than all other snakes combined
35
Q

Not Just Venom!

A

Constriction
- Prey squeezed & dies from asphyxiation/cardiac arrest
- E.g., Boa constrictors, anacondas, pythons

36
Q

Snake Reproduction

A

Internal fertilization
- Hemipene: grooves, hooks and spines!
- Oviparity, ovoviviparity (e.g., vipers), viviparity (e.g. boa constrictor, anaconda)
- Most abandon eggs, some make nests (e.g., king cobra), coil around (e.g., python)

Animal Diversity (20 decks)

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