Test two stats • Mean 65.8 • Median 65 • Max 100 • Min 24 20 30 40 50 60 70 80 90 100 12691712741 Archosauria Chapter 16 Crocodilians • 23 surviving species • Alligatoridae, Crocodylidae, and Gavialidae • http://www.youtube . com/watch?v=BTpa9j60Npg Alligatoridae • Caimans (central and south america) • Alligator (North America and China) Crocodylidae • Tropics worldwide • Largest living reptile – CdlCrocodylus porosus recorddded up to 7 meters Gavialidae • 1 species • India • Fihish speciliialists with long skinny snouts Crocodilian heart • 4 chambered heart • Some differences from other 4 chambered hearts – 2 aortas leaving heart (one from each ventricle) connected by the foramen of panizza • 3 differen t patterns of blood flow are possible – Resting – AiiActivity – Thermoregulation Crocodilian parental care • build nests which are sometimes gaurded some species even aid the hatching by digging the offspring out and carrying them to water • Have TSD (we talked about this earlier) Dinosaurs • Ornithischians • Saurischians – BthBoth have a gait with the legs direc tly under the body (not sprawling as in crocodilians) – Both groups have bipedal forms, the Saurischians are mostly bipedal and this trend opened new adaptive zones for changes in forelimbs. Dinosauria Origin of flight • Flight evolved in 2 lineages of diapsids – Pterosaurs and birds Birds Birds are derived Theropod dinosaurs They were called reptiles more than a century ago by Huxley but this was largely ignored until recently Share d didderived characters wihith Theropo ds Hollow, pneumatic bones; Elongate, mobile S‐shaped neck; Tridactyl foot; Digitigrade posture; Ankle joint forms between tarsal bones rather than tarsals and tibia/fubula; Feather precursors or true fthfeathers; RdReduce d genome size Dromeosaurs • A derived group of Coelurosaurs • Showed character changes that led to flight – WitWrist stttructure tha t allowe d them to flex the writist sideways while rotating them – A more derived dromeosaur have a change in the shoulder joint. The glenoid fossa is orientated laterally instead of ventrally Feathered Dinosaurs • Most dramatic birdlike character of dromeosaurs – Simplest types of feathers are single hollow filaments • Vaned feathers – Caudipteryx and Protoarchaeopteryx Caudipteryx and Protoarchaeopteryx • Had vaned feathers on the second finger and a tuft on the tail • Feathers were symmetrical which are used for social displays or insulation • Asymmetrical feathers appeared with Archaeopteryx Origins of flight • 2 theories – “from the trees down” – “from the ground up” • Trees down says that Archaeopteryx was arblboreal and jdjumped around from tree to tree • http://www.youtube.com/watch?v=FxSGpCOt kSc From ground up • Dromeosaurs consisted of bipedal, cursorial, terrestrial predators. • Arms (wings) used to aid in the bipedal running for balance, used like a chicken running away from a dog, this later evolved into short flights. (this version dropped) • Arms used to catch prey by swatting it down, or for horizontal jumps, more recently modified to include wing assisted incline running Terrestrial origin • Ground up currently seems most consistent with evidence – Arm and wrist movements seem to be consistent with prey seizing – Feathered forelimbs seem poorly suited for climbing • Body size also decreased with flight, surface area of wings and wing loadings must be in the range of 252.5 gm per cm2 Archaeopteryx • Had many characteristics that make us believe that it could fly – Wing loadings – Glenoid fossa – Furcula – Rectangular sternum – Assymetrical flight feathers.