1. From Amphibians to Reptiles
Porsha Chillis and Cameron Volpe

2. Amphibians begin Evolved from Sarcopterygii-rhipistidians
Late Devonian (about 400 mya)
Early amphibians
Acanthostega
Ichthyostega
The amphibians arose from their ancestor, the rhipidistian group of the class Sarcopterygii, in the late Devonian period about 400 million year ago. The earliest amphibians seen in the fossil record are the Acanthostega and Ichthyostega. Acanthostega is one of the earliest tetrapods, having internal gills and living its life in the water. Ichthyostega, however, was more advanced. It used lungs rather than gills to breathe oxygen and had advanced forelimbs that were capable of bearing weight, allowing it to move on land (Futuyma 80).

3. Characteristics of Amphibians
Cold-blooded
Moist skin-absorbs oxygen and water
Fertilization and development of eggs in water
Tied to the water

4. Orders of amphibians Anura Urodela Gymnophionia Frogs Toads Newts
Salamanders
Gymnophionia
Caecilians
“Naked snake”

5. Anura
Urodela
Gymnophionia

6. Amphibians start to evolve
Developed lungs and scales
Stronger legs
Shelled egg
Oldest fossilized egg-280 mya
Shell prevented drying out
Seymouria
Class-Labyrinthodont
Carboniferous period
Westlothiana lizziae
350 mya
Seymouria
Skull like amphibians, rest of the skeleton more like a reptile
Skin-overlapping scales
Had the ability to breathe through its nostrils with its mouth shut
Westlothiana lizziae
-long and slender
-very lizard like
-no sufficient evidence to prove this species is actually a reptile

8. Tuatara-native to new zealand.

9. Lepidosauria Tuatara Lizard Snake Tuatara-native to new zealand
-”living fossils”
Lepidosauria is the superorder that includes all reptiles with overlapping scales
Snake

10. Testudines Crocodylia
Order Testudines-all turtles
Order Crocodylia-all alligators and crocodiles

11. Reptiles become more abundant
Hylonomus lizziae (350 mya)
Oceans receded
Plants well established
Insects abundant
Hylonomus lizziae-first confirmed reptile
Small, slender, gecko like
Reasons they became more abundant:
-Oceans receded-this Increased competition for survival in the seas-move to land
-by the Mesozoic era, gymnosperms were well established and insects were abundant
-reptiles fed on these plants and insects
-evolved sharp teeth to eat their prey and musculature suited for grappling with struggling insects

12. Reptilian advantage Independent from water Thick impermeable skin
Internal fertilization
Laid eggs on land
Thick impermeable skin
Stronger limbs
Internal fertilization-less room for error in fertilizing eggs
Eggs on land
-Eggs more likely to stay where they were laid instead of being carried away by moving water
-Less predators on land to feed on the eggs
-Hatchlings immediately able to breathe air (whereas amphibians go through a tadpole stage)
Skin-scales prevented water loss
Stronger limbs-had to support greater weight on land, water supports against the force of gravity more than air

13. Return to water 80 million years after reptiles evolved
Earliest marine reptiles-Mesosaurus
Webbed feet, paddle-like tail
Became marine dinosaurs
Return to land to lay eggs
Turtles arose
Late Triassic (220 mya)
Anapsids
Plesiosaurs, ichthyosaurs
Meat eaters-prey on land
-when that wasn’t available, evolved to live back in the water
Anapsid-reversion of evolution

14. Diapsid skulls became more modified and larger to make stronger bites and more jaw muscles
Turtles were anapsid-probably a reverse evolution effect
-maybe didn’t need to have such a strong bite for their prey

15. Snake evolution Came from a group of lizards
Lost legs and external ears
Developed a clear eye covering
Developed distinctive way of moving
Hox gene evolution
The lizards liked to burrow. Loss of legs was more conducive to this lifestyle
May have been more predators above ground, or prey below ground, so they began burrowing
Fossil record very poor because of snakes’ fragile bodies
Vestigial hind limbs in pythons and boas-used in mating for grasping
Hox gene for thorax became dominant over front limb gene, body became one big thorax

16. Study on the limbs of tetrapods
Virginia Abdala and Rui Diogo
Dissections of the pectoral and forelimb muscles
General skeletal pattern of amphibians and reptiles was acquired early in evolutionary history
Highly conserved characters
Many homologies
Confirmed reptilian musculature stronger than amphibian

17. Works Cited
Abdala, Virgina, and Rui Diogo. "Comparative Anatomy, Homologies and Evolution of the Pectoral and Forelimb Musculature of Tetrapods with Special Attention to Extant Limbed Amphibians and Reptiles." Journal of Anatomy (2010):
"Amphibians." UXL Encyclopedia of Science Encyclopedia.com. 26 Feb <
Jothi. "Changeover from Amphibians to Reptiles." LexisNexis Academic. LexisNexis, 27 Dec Web. 29 Jan
Futuyma, Douglas J. “Chapter 4: Evolution in the Fossil Record” Evolution. Sunderland, MA: Sinauer Associates,
"Hylonomus." Wikipedia: The Free Encyclopedia. Wikimedia Foundation, Inc., Web. 2 Mar <
“Origin of snakes makes a long story.” The Press (2000): 19. Lexis Nexis. Web. 29 Jan
Pough, F. Harvey. Herpetology. Upper Saddle River, NJ: Prentice Hall, Print.
"Reptile and Amphibian Evolution." Scared Cricket. Michelle Caldwell. Web. 02 Mar <
"Reptile Evolution: Humble Beginnings." Reptiles: Great As Pets Or In The Wild. 16 Nov Web. 03 Mar <
Sheen, Judy P.. "Reptilia." Animal Sciences Encyclopedia.com. 26 Feb <
Short, Kevin, and Yomiuri. "Reptiles and Their Wriggling Relatives." LexisNexis Academic. LexisNexis, 2 Nov Web. 29 Jan
"Snake." Wikipedia, The Free Encyclopedia. Wikimedia Foundation Inc., 28 Feb Web. 03 Mar <
"Weslothiana." Wikipedia: The Free Encyclopedia. Wikimedia Foundation, 21 Feb Web. 2 Mar <

18. Questions?