Dinosaurs: Their Role in Paleogeography
•We are going through an extinction that it is man made.
•In late Triassic - dinosaurs experienced a small extinction
•What had contributed to the extinction?
•we are looking at plate tectonic were we have continents forming super
continents diversity is on the low side and as the continents separate it creates
diversity is going upward
•Dinosaurs achieved a global distribution
•more diversity more dinosaurs
•Vertebrate are rarer than invertebrates
•Ex. Patagonia have more fossil material that tells us more about dinosaurs
•Rare fossil of two species together
•what do these tell us ?
•they lived together and we can reconstruct that ecosystem
•Rare fossil of interspecific behavior
•Ex. One biting the other, protected themselves from predators
•Ex. lived together and died together in combat position
• Taxa which occur a specific geographic area and are related to certain
•Why are they endemic to Australia?
•The moment Australia separated the animals stayed in Australia and
they evolved. Migration routes are shut down.
•Mountain Range forms certain animals are not able to cross over.
Barriers of faunal migration.
•What period of the mesozoic has the most endemism ?
•A new dinosaur genus occurred every 4-8 Million years
•Possibly exceeded at time of mass extinctions
•Relatively complete fossil record
•A new species every 1.9 Million years
•Stegosaurs produces 1 new species every 5.6 Million years
Minimum Divergence Time: Sedimentary column
•one is able to date the sequence
•Y=125 Ma to X=100 Ma (eggs) MDT 25
•If X and Y are related, there must be an ancestor older than 125 Ma
•MDT is as old or older than 125 Ma, if not preserved ghost lineage
•Used for estimation of fossil completeness
•MDTs in Ceratopsian dinosaurs
•Range from 0-30 million years
•Average 5 Ma
•Good candidate or temporal and geographic distribution studies
•North america spread out nicely along the seaway and China
Late Triassic (231-208 Ma)
•Time of Pangea
•Climate: Heat and aridity
•those dinosaurs that managed to survive these extreme conditions they are
forming the assemblages for the late Triassic they are completely different
than dinosaurs from the cretaceous.
•Strong seasons (continental climate)
Evolution of Dinosaurs through time
•Who was around the Triassic?
•Earliest dinosaurs (231-223 Ma)
•Theropod, Middle to Late Triassic, Argentina
•China and India
•South Africa- Stromberg Series
•Ancient fluvial system
•Beautifully preserved therapsids
•Several localities in Europe
•Chile and Argentina
•New Mexico, Utah, and Arizona
•Ghost Ranch- Coelophysis (Cerapoda)
Early Jurassic 208-178 Ma
•Dinosaurs become more dominant
•Slow break up of Pangea