Class Reptilia – Amniote Origins Class Reptilia – Amniote Origins and Nonavian Reptiles and Nonavian Reptiles

With the reptile group(s) we see better With the reptile group(s) we see better adaptation to a terrestrial existence.adaptation to a terrestrial existence.

1) shelled amniotic egg1) shelled amniotic egg 2) tough, dry and scaly skin2) tough, dry and scaly skin 3) efficient jaws for crushing and gripping prey3) efficient jaws for crushing and gripping prey 4) efficient circulatory system with a higher 4) efficient circulatory system with a higher

blood pressureblood pressure 5) internal fertilization using some form of 5) internal fertilization using some form of

copulatory organcopulatory organ 6) better developed lungs6) better developed lungs 7) better body support; more efficient limbs7) better body support; more efficient limbs 8) more complex nervous systems8) more complex nervous systems

The Amniotic EggThe Amniotic Egg

The liquid environment needed for the The liquid environment needed for the eggs/embryo of amphibians has been eggs/embryo of amphibians has been enclosed within the amniotic eggenclosed within the amniotic egg

No longer a necessity to breed in waterNo longer a necessity to breed in water Amniotic egg consists of 4 Amniotic egg consists of 4

extraembryonic membranes; the amnion, extraembryonic membranes; the amnion, yolk sac, allantois, and the chorion all yolk sac, allantois, and the chorion all surrounded by a protective, porous shell.surrounded by a protective, porous shell.

Ancestral reptiles gave rise to the Ancestral reptiles gave rise to the monophyletic group of the Amniota which monophyletic group of the Amniota which include modern reptiles, birds, and include modern reptiles, birds, and mammalsmammals

Figure 18_04Figure 18_04

Skull Structures of Reptilian Skull Structures of Reptilian GroupsGroups

Evolutionary development within the Evolutionary development within the late Carboniferous gave rise to 3 major late Carboniferous gave rise to 3 major groups of amniotes based upon skull groups of amniotes based upon skull structurestructure

AnapsidsAnapsids – no temporal opening behind – no temporal opening behind orbits; gave rise to turtlesorbits; gave rise to turtles

DiapsidsDiapsids – 2 temporal openings behind – 2 temporal openings behind orbit; gave rise to modern reptilian orbit; gave rise to modern reptilian groups and birdsgroups and birds

SynapsidsSynapsids – 1 temporal opening behind – 1 temporal opening behind orbit; gave rise to modern mammals orbit; gave rise to modern mammals

Paraphyly of ReptiliansParaphyly of Reptilians

Class Reptilia is a paraphyletic group; Class Reptilia is a paraphyletic group; does not include birds (Aves) within the does not include birds (Aves) within the clade of Reptilia although birds are the clade of Reptilia although birds are the direct descendants of reptilesdirect descendants of reptiles

Crocodilians and birds share a more Crocodilians and birds share a more recent common ancestor (along with recent common ancestor (along with dinosaurs) and represent the Archosauriadinosaurs) and represent the Archosauria

Lepidosauria represents the snakes, Lepidosauria represents the snakes, lizards, tuataras, and worm lizardslizards, tuataras, and worm lizards

Figure 18_01Figure 18_01

Order Testudines - turtlesOrder Testudines - turtles

Anapsid group having diverged early in the Anapsid group having diverged early in the evolutionary history of the reptilian groupevolutionary history of the reptilian group

Possess distinctive shellsPossess distinctive shells Long-lived adapted to terrestrial (tortoises typically), Long-lived adapted to terrestrial (tortoises typically),

semi-aquatic, aquatic, and marine existence (sea semi-aquatic, aquatic, and marine existence (sea turtles)turtles)

Lack teethLack teeth All are oviparous and bury eggs on land (including All are oviparous and bury eggs on land (including

aquatic and sea turtlesaquatic and sea turtles No specific distinction between the words turtle, No specific distinction between the words turtle,

tortoise, and terrapin; tortoise and terrapin generally tortoise, and terrapin; tortoise and terrapin generally refers to terrestrial types and turtles to aquatic typesrefers to terrestrial types and turtles to aquatic types

Diapsid groups – Lizards (Order Diapsid groups – Lizards (Order Squamata)Squamata)

Highly diversified and successfully adapted for Highly diversified and successfully adapted for walking, running, climbing, swimming, and walking, running, climbing, swimming, and burrowing; common groups are geckos, iguanas, burrowing; common groups are geckos, iguanas, skinks, monitors, and chameleonsskinks, monitors, and chameleons

Differentiated from snakes by:Differentiated from snakes by: 2 pair of legs (although a few are legless)2 pair of legs (although a few are legless) Fused lower jaw halvesFused lower jaw halves Movable eyelidsMovable eyelids External earsExternal ears Absense of fangsAbsense of fangs The Amphisbaenia are the worm lizards well adapted The Amphisbaenia are the worm lizards well adapted

for burrowingfor burrowing

Diapsid groups - SnakesDiapsid groups - Snakes

Completely legless (python and boa Completely legless (python and boa groups possess vestigial limbs) and groups possess vestigial limbs) and elongatedelongated

Kinetic skull allowing for swallowing of Kinetic skull allowing for swallowing of prey wholeprey whole

Many possess Jacobson’s organs to Many possess Jacobson’s organs to detect preydetect prey

Pit vipers possess infrared sensorsPit vipers possess infrared sensors Some venomous and with fangs (rear-Some venomous and with fangs (rear-

fanged vs. front-fanged types)fanged vs. front-fanged types)

Diapsid groups – Tuataras Order Diapsid groups – Tuataras Order SphenodontaSphenodonta

Ancient, relic lizard like species Ancient, relic lizard like species found in New Zealandfound in New Zealand

Possess diapsid skull like that of Possess diapsid skull like that of ancient ancestors and a median ancient ancestors and a median parietal “third eye”parietal “third eye”

Diapsid groups – Order Diapsid groups – Order CrocodiliaCrocodilia

Only extant reptilian representatives of the Only extant reptilian representatives of the archosauria that gave rise to dinosaurs and archosauria that gave rise to dinosaurs and birdsbirds

Large skulls with powerful jawsLarge skulls with powerful jaws Secondary palateSecondary palate Most complex social behavior of any reptilians Most complex social behavior of any reptilians

(mating and reproductive behavior)(mating and reproductive behavior) High nest temps produce males, low temps High nest temps produce males, low temps

produce females (opposite in turtles)produce females (opposite in turtles) Alligator common to Florida; North American Alligator common to Florida; North American

crocodile in South Florida alsocrocodile in South Florida also