Class Reptilia – Amniote Origins and Nonavian Reptiles With the reptile group(s) we see better adaptation to a terrestrial existence. With the reptile group(s) we see better adaptation to a terrestrial existence. 1) shelled amniotic egg 1) shelled amniotic egg 2) tough, dry and scaly skin 2) tough, dry and scaly skin 3) efficient jaws for crushing and gripping prey 3) efficient jaws for crushing and gripping prey 4) efficient circulatory system with a higher blood pressure 4) efficient circulatory system with a higher blood pressure 5) internal fertilization using some form of copulatory organ 5) internal fertilization using some form of copulatory organ 6) better developed lungs 6) better developed lungs 7) better body support; more efficient limbs 7) better body support; more efficient limbs 8) more complex nervous systems 8) more complex nervous systems

The Amniotic Egg The liquid environment needed for the eggs/embryo of amphibians has been enclosed within the amniotic egg The liquid environment needed for the eggs/embryo of amphibians has been enclosed within the amniotic egg No longer a necessity to breed in water No longer a necessity to breed in water Amniotic egg consists of 4 extraembryonic membranes; the amnion, yolk sac, allantois, and the chorion all surrounded by a protective, porous shell. Amniotic egg consists of 4 extraembryonic membranes; the amnion, yolk sac, allantois, and the chorion all surrounded by a protective, porous shell. Ancestral reptiles gave rise to the monophyletic group of the Amniota which include modern reptiles, birds, and mammals Ancestral reptiles gave rise to the monophyletic group of the Amniota which include modern reptiles, birds, and mammals

Figure 18_04

Skull Structures of Reptilian Groups Evolutionary development within the late Carboniferous gave rise to 3 major groups of amniotes based upon skull structure Evolutionary development within the late Carboniferous gave rise to 3 major groups of amniotes based upon skull structure Anapsids – no temporal opening behind orbits; gave rise to turtles Anapsids – no temporal opening behind orbits; gave rise to turtles Diapsids – 2 temporal openings behind orbit; gave rise to modern reptilian groups and birds Diapsids – 2 temporal openings behind orbit; gave rise to modern reptilian groups and birds Synapsids – 1 temporal opening behind orbit; gave rise to modern mammals Synapsids – 1 temporal opening behind orbit; gave rise to modern mammals

Paraphyly of Reptilians Class Reptilia is a paraphyletic group; does not include birds (Aves) within the clade of Reptilia although birds are the direct descendants of reptiles Class Reptilia is a paraphyletic group; does not include birds (Aves) within the clade of Reptilia although birds are the direct descendants of reptiles Crocodilians and birds share a more recent common ancestor (along with dinosaurs) and represent the Archosauria Crocodilians and birds share a more recent common ancestor (along with dinosaurs) and represent the Archosauria Lepidosauria represents the snakes, lizards, tuataras, and worm lizards Lepidosauria represents the snakes, lizards, tuataras, and worm lizards

Figure 18_01

Order Testudines - turtles Anapsid group having diverged early in the evolutionary history of the reptilian group Anapsid group having diverged early in the evolutionary history of the reptilian group Possess distinctive shells Possess distinctive shells Long-lived adapted to terrestrial (tortoises typically), semi- aquatic, aquatic, and marine existence (sea turtles) Long-lived adapted to terrestrial (tortoises typically), semi- aquatic, aquatic, and marine existence (sea turtles) Lack teeth Lack teeth All are oviparous and bury eggs on land (including aquatic and sea turtles All are oviparous and bury eggs on land (including aquatic and sea turtles No specific distinction between the words turtle, tortoise, and terrapin; tortoise and terrapin generally refers to terrestrial types and turtles to aquatic types No specific distinction between the words turtle, tortoise, and terrapin; tortoise and terrapin generally refers to terrestrial types and turtles to aquatic types

Diapsid groups – Lizards (Order Squamata) Highly diversified and successfully adapted for walking, running, climbing, swimming, and burrowing; common groups are geckos, iguanas, skinks, monitors, and chameleons Highly diversified and successfully adapted for walking, running, climbing, swimming, and burrowing; common groups are geckos, iguanas, skinks, 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 halves Fused lower jaw halves Movable eyelids Movable eyelids External ears External ears Absense of fangs Absense of fangs The Amphisbaenia are the worm lizards well adapted for burrowing The Amphisbaenia are the worm lizards well adapted for burrowing

Diapsid groups - Snakes Completely legless (python and boa groups possess vestigial limbs) and elongated Completely legless (python and boa groups possess vestigial limbs) and elongated Kinetic skull allowing for swallowing of prey whole Kinetic skull allowing for swallowing of prey whole Many possess Jacobson’s organs to detect prey Many possess Jacobson’s organs to detect prey Pit vipers possess infrared sensors Pit vipers possess infrared sensors Some venomous and with fangs (rear-fanged vs. front-fanged types) Some venomous and with fangs (rear-fanged vs. front-fanged types)

Diapsid groups – Tuataras Order Sphenodonta Ancient, relic lizard like species found in New Zealand Ancient, relic lizard like species found in New Zealand Possess diapsid skull like that of ancient ancestors and a median parietal “third eye” Possess diapsid skull like that of ancient ancestors and a median parietal “third eye”

Diapsid groups – Order Crocodilia Only extant reptilian representatives of the archosauria that gave rise to dinosaurs and birds Only extant reptilian representatives of the archosauria that gave rise to dinosaurs and birds Large skulls with powerful jaws Large skulls with powerful jaws Secondary palate Secondary palate Most complex social behavior of any reptilians (mating and reproductive behavior) Most complex social behavior of any reptilians (mating and reproductive behavior) High nest temps produce males, low temps produce females (opposite in turtles) High nest temps produce males, low temps produce females (opposite in turtles) Alligator common to Florida; North American crocodile in South Florida also Alligator common to Florida; North American crocodile in South Florida also