end-cretaceous and whalesteststrata.geology.wisc.edu/teachpaleobiology/...end-cretaceous mass...
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Paleontology!University of Wisconsin – Madison Andrew A. Zaffos April 25, 2016
End-Cretaceous and Whales
End-Cretaceous mass extinction n Approximately 75% of species go extinct
n This number is actually a very crude estimate. It is based on the number of fossil families that go extinct, and then multiplying that number by the species in analogous families today.
n Dinosaurs n All “22”-orders [a lot] of non-avian dinosaurs go extinct.
n “Non-Dinosaur Dinosaurs” n Pterosaurs n Plesiosaurs n Mosasaurs
n Marine Invertebrates n Rudist bivalves n Ammonites
n Plants n Cycads [dead clade walking] n Lycopods [dead clade walking]
Triggers and Kill Mechanisms
Who is winning?
~ 5,000
~ 10,000
The progression of reefs
The progression of reefs
The progression of reefs
Why are horns so for reefs?
The plants that barely pull through
Dead clades walking
Outstanding questions about DCWs n Would these clades have declined even without the mass extinction?
n Why don’t more clades show a dead clade walking effect?
n Why are there spatial patterns in the frequency of Dead Clades Walking?
n What is it about the post-extinction world that stops DCWs from recovering? n Environmental? n Biological?
Whales! Whales Whales! n Whales have a suite of unique features that set them apart from other
mammals. n Absence of rear legs (remember all mammals are tetrapods!) n Front limbs shaped like paddles (remember we’re all lobe-finned fish!) n A flattened tail n A blowhole (a nostril on the top of the head) n A super short neck n Special ears for listening underwater n Stronger spinal column to anchor the swimming muscles of the tail.
Two Types of Whales
Odontocetes (toothed whales)
n Simple conical, curved, and smooth teeth.
n Most mammals have much more complex teeth.
Mysticetes (filter feeding)
The progression of whale evolution
The Ear
The fins came next
Probably lived more like a Hippo or Croc
Shortening of legs and lengthening tail
Nostril moves back
Side eye and fluke
The leg disappears
Leg memory is still a thing n A dolphin with two extra back
legs.
n Found in Japan in 2006
n Goldschmidt and hopeful monsters.
n Allometry? Evo-Devo?
