GEOL 102 Lecture Notes - Lecture 16: Cambrian Explosion, Mesozoic, Phanerozoic
Document Summary
Laurentia, siberia, and baltica split away from gondwana. Gondwana- africa, south america, antarctica, australia, eurasia, india. Melting of the great glaciers from the proterozoic meant that sea levels had risen (transgression) Cambrian characterized by flooding of continents- shallow seas. A massive evolutionary radiation occurred at the beginning of the cambrian. While the roots of many modern groups stretch into the proterozoic, they diversified ad thrived in the cambrian. Lagerstatten preserving some of the earliest metazoans known from the. Two valves (shells), lophophore(cilia for filter feeding), bilateral symmetry through hinge. Specialized stinging cells, radial symmetry, a single orifice. Undifferentiated cells (lack organs, different tissues) sessile, choanocytes. Notochord, dorsal hollow nerve chord, pharyngeal slits, tail. We don"t know where these things belong in the tree of life. Most groups found in chengjiang are present here as well- more diverse. Index assemblage for burgess shale type fauna . >10 lagerstatten, ranging from 525 mya (chengjiang) to 500 mya (kinekulle,
