EARTH 7 Lecture Notes - Lecture 16: Ordovician, Extinction Event, Rudists
11/30/17
● The k-pg mass extinction (and a few highlights since than)
○ Mass extinction 250 MA
○ Mass extinction 65 MA
● The Five great mass extinctions
○ End ordivician
■ 45% genera
■ 70% species
○ Late devonian
■ 20% genera
■ 40% species
○ End permian
■ 60% genera
■ 80% species
○ End triassic
■ 35% genera
○ Cretaceous-paleogene
■ 40% genera
■ 60% species
● Are we in the middle of a 6th mass extinction??
○ Extinction rates right now may be 1000 times higher than normal background
rates
○ Hunting
○ Destruction of habitat
○ Disregard of ecosystem
○ Global warming
● Major features of the k-pg extinction
○ The 5th most severe extincton
○ Worldwide
○ The most studied mass extinction
○ Usually is focused on dinosaurs
○ Extinctions on land and oceans
● Main cast of characters that went extinct in k-pg
○ Ammonoids
○ Belemnites
○ Rudist bivalves
○ Marine reptiles (plesiosaurs, mosasaurs)
○ Non-avian dinosaurs
○ Pterosaurs
■ During a mass extinction the last place you want to be is on top of
the food chain (t-rex)
● Microfossil extinctions
○ Coccolithophorids went from 106 to 14 species
○ Planktonic diatoms went from 192 to 161
○ Silicoflagellates 14 to 3
○ Planktonic foraminifera 46 to 16
○ Radiolaria 45 to 42
■ Huge part of worldwide photosysnthesis happens in the ocean with
single celled eukaryotes
● Those who made it through k-pg
○ Flowering plants (angiosperms)
○ Insects
○ Amphibians
○ Turtles, snakes, lizards
○ Flying dinosaurs with beaks (Aves)
○ Some mammals went extinct (many groups of marsupials), but others survived
and thrived afterwards
● Many terrestrial dinosaurs had already gone extinct, but at 65 MA all remaining groups
(except birds) abruptly join them
○ All dinosaurs now gone except flying ones with beaks
● Explaining the k-pg
○ Ridiculous hypotheses over the years
Document Summary
The k-pg mass extinction (and a few highlights since than) Extinction rates right now may be 1000 times higher than normal background rates. Main cast of characters that went extinct in k-pg. During a mass extinction the last place you want to be is on top of. Coccolithophorids went from 106 to 14 species. Planktonic diatoms went from 192 to 161. Huge part of worldwide photosysnthesis happens in the ocean with. Those who made it through k-pg single celled eukaryotes. Some mammals went extinct (many groups of marsupials), but others survived and thrived afterwards. Many terrestrial dinosaurs had already gone extinct, but at 65 ma all remaining groups (except birds) abruptly join them. All dinosaurs now gone except flying ones with beaks. Caterpillars or mammals ate all the food. The k-pg mass extinction (and a few highlights since then) In 1980, walter and luis alvarez (ucb) proposed that 10 km diameter asteroid struck the earth causing mass extinction.
