End-Cretaceous Mass Extinction Flashcards
Hadrosaur Teeth vs. Sauropod Teeth
Sauropod: simple peg like teeth used for nipping off vegetation and swallowing it whole
Hadrosaur: complete dental battery forming “washboard” like surface for grinding and chewing before swallowing
Coevolution of herbivorous dinosaurs (teeth) and land plants with particular emphasis on the rise of angiosperms
- most gynosperms have reproductive cycles of 18 months or longer
- angiosperm grow from seed and release within a few weeks
- dinosaurs eat everything in their path causing angiosperm to be favored and continue after their intense grazing
What are angiosperm land plants?
flowering seed plants
- embryo develops in the protective ovary of the flower
- double fertilization
When do angiosperm land plants first appear in the fossil record?
early cretaceous
What do fossil nest sites and trackways tell us about dinosaur behavior and social structure?
- the young are reared in the nest showing parents are involved for long periods of time, similar to warm-blooded endotherms (like birds)
- communal nesting sites suggest seasonal breeding, migration, and birthing patterns
When was the “End-Cretaceous Mass Extinction”?
at the end of the cretaceous era
Walter & Luis Alvarez
Walter: wanted to know how much time clay layer at K/Pg boundary represented
Luis: knew that iridium was rare on earth but rained from space as cosmogenic dust and meteorites
CONCLUSION: if one could measure iridium concentration, one could estimate amount of time it took to accumulate assuming a steady input
Victims of the End-Cretaceous Mass Extinction
- 76% of marine invertebrate animal species
- non-avian dinosaurs
- 50% of plants in SOME areas
- some mammal groups
What are the various lines of evidence for extraterrestrial cause of End-Cretaceous Mass Extinction?
- shocked quartz
- microspherules (tektites)
- iridium anomoly
- Yucatan Crater (circle of potholes
