Study Guide for a Geol Exam

Study Guide for a Geol Exam - Mesozoic birds &...

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Unformatted text preview: Mesozoic birds & Pterosaurs Evolution Many adaptations strengthened the skeleton to withstand the stresses associated with flying *Development of perching and limited flight * Fusion of tail and fully folding wing * Fusion of hand and tarsal region of food * Loss of teeth (Feeding Adaption) The next more modern bird above Archaeopteryx is Rahonavis .-A synsacrum- Still retained some primitive characters, including a long tail- No carpometacarpus A major evolutionary step occurred with the development of a pygostyle- shortened tail composed of few vertebrae. The group of birds with a pygostyle is called the Pygostylia and is composed of the Conficiusornithidae and the Ornithothraces. Ornithothraces- Lead into the evolution of modern birds Modifications- Development of the alula- the bastard wing, a series of feathers attached to the 1 st digit Functions much like the slat on an airplane wing Within the Ornithothraces are two major lineages Enantiornithes- Extinct- Have many of the characteristics of modern birds including keeled sternum and partly fused carpometacarpus- Tarsal region is quite distinct- Only the proximal (near the ankle) area of the tarsals is fused, so there is no tarsometatarsus as in modern birds. Ornithuromorpha-includes extinct subgroups - Hesperornithiforms- Large, long-necked, flightless diving/fishing birds- Similar to modern birds but retain teeth in their mouth-Restricted to the Cretaceous- Big fused synsacrum- Very different in arm region- No big keel (used for flight)- No wing, First birds to lose flight- Ichthyornithiformes - Long-necked, toothed, flying, fishing birds that resemble modern birds Even more closely than the Hesperornithiformes Restricted to Cretaceous, Most were the size of gulls Modern Birds ( Aves ) become much more diverse in the Cenozoic Period The Avalrezesaurid Controversy - Look very m uch like non-avian theropod dinosaurs- Lack a tarsometatarsus and a pygostyle- However, they have a carpometacarpus and a keeled sternum- This is a n exa mple of convergent evolution - Cladistic a n alyses do not a gre e on where the alvarezesaurids belong Pterosaurs- Not birds and not dinosaurs- The first flying vertebrates- Evolved in the Late Triassic and went extinct at the end of the - Have a global distribution- Like the dinosaurs, are Ornithodirans - Two Basic Types o Rhamphorhyncoids Small, long tail, short necks Go extinct at the end of the Jurassic Not a natural group Pterodactyloids-Small to large, short tail, relatively long neck-Evolve in Jurassic and go extinct at the end of the Cretaceous - Pterosaurs are the largest flying vertebrates to have ever lived - marine shoreline deposits was their preferred habitat- Many of them were piscivorous- they ate fish, - supported by their sharp needle like teeth- some had no teeth or teeth that were very thin and used for sieving- fur like covering on the body, suggesting they were warm blooded...
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This test prep was uploaded on 04/22/2008 for the course GEOL 111 taught by Professor Getty during the Fall '07 term at UConn.

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Study Guide for a Geol Exam - Mesozoic birds &...

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