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Friday, February 17, 2023

Oops, We Did It Again -- Energy Sector This Year -- You Never Expect To See This -- "Worst Results Ever" -- February 17, 2023

Link here.


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The Book Page
The Rise and Reign of the Mammals
Steve Brusatte
c. 2022

In round numbers:

  • amphibians appear on land, 365 million years ago
  • the "link" from amphibian to reptile/mammal ancestor appears: 300 million years ago
  • mammal/reptile split --> direct mammalian ancestor (cynodont): 260 million years ago
  • dinosaurs appear: 250 million years ago
  • mammals flourish; non-dinosaur reptiles persist (birds, crocodile and their ancestors)

Amphibians --> reptile/mammal ancestor

  • skull difference
    • one group develops two large skull openings behind each of their eyes -->disapsids --> reptiles
    • the other group: the two large skull openings fuse into one --> synapsids --> mammals
  • for test-taking, how does one remember which is which?
    • these large openings -- windows -- fenestrae -- that's where muscles attach
    • the stronger the muscles, the more windows needed
  • which have stronger jaw muscles: crocodiles or humans?
    • so, crocodiles are diapsids; mammals are synapsids
  • note: the synapsides in humans have anatomically closed but one can feel "functional" "windows" - the synapsid -- when opening and closing jaws

This book is c. 2022 but it's already somewhat out of date, or perhaps in period of transition

  • the ancestor -- amphibian -->reptile/mammal ancestor -- has most recently been "called" a pelycosaur
  • but now, pelycosaur is already falling out of favor
    • pelycosaur is still used informally, as in this book, but purists in formal settings use a new term
  • now, the preferred term: Eupelycosauria (Eu = true; pelycosaur)
  • the term Eupelycosauria includes most pelycosaurs, but also Therapsida and Mammalia

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