Video Assignments Microraptor PBS The Four-winged Dinosaur Mark Davis SUNY Cortland Library Online Radiolab Apocalyptical http://www.youtube.com/watch?v=k52vd4wbdlw&feature=youtu.be Minute 13 through minute 60 Link to this video will be emailed but you can search on Youtube for Radiolab Apocalyptical
Evolutionary Origin of Birds Outline Why birds are reptiles Archaeopteryx the link to reptiles Birds as dinosaurs What kind of dinosaur Theropods as bird precursors Feathered dinosaurs Molecular evidence
Characteristics that Define Birds Feathers Bills Lightweight Bones Furcula Opposable Hallux Efficient Respiratory System External Eggs & Parental Care Finely-tuned Nervous Systems
Why Birds are Reptiles Thomas Huxley 19 th Century Naturalist regarded birds as Glorified Reptiles Ancestor of A & B Species A Ancestor of A, B, & C Species B Cladistics classification application that attempts Species C to group organisms based on shared derived traits. (i.e., novel traits that were inherited through a common ancestor)
Evolutionary Origins Species A Species B Species C Ancestor of A, B, & C Ancestor of A & B
Why Birds are Reptiles Shared Derived Traits Single Occipital Condyle Female Heterogametic Sex Single Middle Ear bone Sclerotic Eye Ring Fused Jaw Bones Nucleated Red Blood Cells Epidermal Scales
Archaeopteryx as a Missing Link Archaeopteryx lithographic fossil from lithographic rock quarries in Germany 150 MYA
Archaeopteryx as a Missing Link Reptile-like traits Reptilian teeth Long tail Separate pelvic, hand, head, and foot bones Dinosaur-like hip Skull osteology of reptiles Floating gastric ribs
Archaeopteryx as a Missing Link Bird-like traits Asymetrical feathers on wings Furcula Reversed hallux (?) What was the life-style of Archaeopteryx? Arboreal or ground-dweller? Volant?
More Specimens of Archeopteryx 2005--Science 310:1483
Who were the direct ancestors to birds? Pterosaurs Pre-dinosaur, pre-crocodilian ancestor (Archosaurs)? Theropod dinosaurs
Ornithischians (Stegosaurus, Ankylosaurus, Corythosaurus, Iguanodon) Saurischians Lizard-hipped (Brachiosaurus, T. rex, Velociraptor, Deionychus) DINOSAURS Birds???? Thecodonts--Archosaurs
Dinosaur-Bird Connection Ornithischians (Stegosaurus, Ankylosaurus, Corythosaurus, Iguanodon) Saurischians Lizard-hipped (Brachiosaurus, T. rex, Velociraptor, Deionychus) Backward tilted pelvis, Predentary bone, Ossified vertebral tendons Hands rotate around digits III, IV, and V Pelvis tilted forward, No predentary No ossified tendons Digits II, III, and IV DINOSAURS
Potential Theropod Precursors Hollow bones Three-toed foot (digit I rotated backwards)
Caudipteryx Semilunar carpal Pectoral girdle enlargement Bipedal Reduction in digits and arms Feathers???
Elongated feathers worthy of flight Arms and legs of equal length
Enlarge pectoral girdle Fusion and reduction of bones Reduction in tail Motor system development Beak development Respiratory efficiency
Why Birds are Reptiles Cladistics of Morphology and Molecular Data Shark Amphibians Snakes Lizards Turtles Crocodilians Reptiles Birds Mammals
Habits of Archaeopteryx (Feduccia, 1993)
Glen & Bennett, 2007.
Cuckoos and Road Runners Pigeons
The first birds (Mesozoic) were very likely ground foragers and not arboreal foragers.
Feathered Dinosaurs Hot bed of dinosaur fossils in Chinese Liaong Province New species of feathered theropod dinosaurs-120 MYA Sinosauropteryx (first Chinese dragon feather) Caudipteryx
Caudipteryx zoui Filamentous tail feathers Other specimens that blur the line between dinosaurs and birds include Protoarchaeopteryx, Confuciusornis
Birds as Theropods Feathered Theropods Feathers evolved before flight Feathers are no longer a novel feature of birds Share large numbers of advanced traits Evolutionary trends in theropods are consistent with bird evolution
The Four-winged Dinosaur Microraptor Significance? What about non-avian dinosaur feet and Chukars?
Opposition to Theropod-bird lineage Feduccia--birds share an ancestor with an Archosaur Bird-theropod similarities are due to convergent evolution Bipedalism Flight evolved from the trees down. Deinonychus is 40 MY more recent than Archaeopteryx. Temporal Paradox: you can t be your own grandmother
Comparative Embryology Feducia s strongest argument. Top row-alligator Middle row-chicken Bottom row-turtle Assume: Digit IV forms the central axis of modern hands in birds, turtles, and crocodiles Counting backward it appears that birds retain digits II, III, and IV and not digits I, II, and III as in Theropods Photo from Burke and Fedducia, 1997
Who cares about finger number? (Pennisi-2005, Science 307:195) Digit I in terrestrial vertebrates has unusual development Digit I depends on the developmental gene Hoxd13 and not Hoxd12 Molecular genetics suggests that Digit I in birds is indeed Digit I
Amino Acid Sequence from Bone Collagen of Dinosaurs C, G, I are from Ostrich
Amino Acid Sequence of Dinosaur Collagen Birds share a more recent common ancestor with dinosaurs than to early reptiles.
Concluding Remarks The origin and evolution of birds is one of the greatest modern day debates in evolutionary biology Birds are reptiles Theropod origin of birds is gaining strength from many biological disciplines Remaining Questions; How did flight arise and & why did feathers evolve?