EPSC 233 Lecture Notes - Lecture 21: Ammonoidea, Swim Bladder, Teleost
6 Nov 2018
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Coal gap apparently delayed recovery of large trees in swampy areas. Only mollusks and ammonoids reasonably abundant in early triassic. Ammonoids thrived after near extinction (just two genera survived) Evolution of the swim bladder to regulate buoyancy. Some modern sharks (tiger sharks) evolved by early. Nothosaurs the first marine reptiles to appear; restricted to triassic. Placodonts large, turtle-like, broad teeth for crushing shell fish. Plesiosaurs derived from nothosaurs, appeared in triassic and the dominant marine carnivore through most of the. Mososaurs marine lizards up to 15 m long. Ichthyosaurs, known as the fish-lizard appeared somewhat later in the mesozoic and are distinct from the other swimming reptiles in that they gave birth to live young. Skeleton of mother giving birth to live young (not eggs?) Crocodiles also emerged in the mesozoic, although later than the other groups. They diverged from the last common ancestor to the dinosaurs, and hence are a sister group to the dinosaurs.
