EARTH 7 Lecture Notes - Lecture 17: Quaternary Glaciation, Ceratopsia, Ornithopod
12/5/17
●Mammals
○ Generally small-sized in mesozoic. Ecologically diverse, but not dominant.
■ 18 orders today, 17 of these did not exist in mesozoic
■ Rapid speciation in early cenozoic
■ Trend towards larger sizes
● A similar story for aves
● Humans: an evolutionary overview
● Triassic generally hot and dry
● Jurassic generally hot and humid
● Cretaceous generally hot with shallow continental seas
● General cenozoic cooling trend, leading to current ice ages
○ Cooling due to the continued breakup of pangaea and closure of equatorial
currents
● The last 2.5 million years is known as the quaternary glaciation
○ This is when permanent ice sheets were established at both north and south
poles
○ In geological terms, “ice ages” correspond to times with permanent ice sheets at
both poles.
● Life is robustly opportunistic and increases in complexity seem to be an inherent part of
the process (not within every lineage, but on a broad scale)
● Convergence
○ Dinosaurs, pterosaurs, mammals, and insects all independently develop flight
● convergence : ceratopsians and ornithopods
○ From small & bipedal to large & quadrupedal
■ (also convergent with armored dinosaurs, and sauropods)
○ Lose upper front teeth
○ Develop dental batteries
○ Evolve extensive cranial ornamentation
Document Summary
18 orders today, 17 of these did not exist in mesozoic. Cretaceous generally hot with shallow continental seas. General cenozoic cooling trend, leading to current ice ages. Cooling due to the continued breakup of pangaea and closure of equatorial currents. The last 2. 5 million years is known as the quaternary glaciation. This is when permanent ice sheets were established at both north and south poles. In geological terms, ice ages correspond to times with permanent ice sheets at both poles. Life is robustly opportunistic and increases in complexity seem to be an inherent part of the process (not within every lineage, but on a broad scale) Dinosaurs, pterosaurs, mammals, and insects all independently develop flight. From small & bipedal to large & quadrupedal. (also convergent with armored dinosaurs, and sauropods)
