Early Mesozoic 1
Especially well-exposed and well-studied in Europe
Pangea took final form near the PT in the Early Triassic
Pangea so immense that much of it was arid and far removed from
the sea
Broke apart by the Jurassic
Overall sea level rise during this time period
Marine Benthic Life
Early Triassic
PT crisis removed previously diverse groups from marine habitats
Ammonoids abundant
Cyanobacterial stromatolites returned in the
Low-diversity bivalve mollusks abundant
Brachiopods also make a short-term comeback
Triassic
Sea urchins greatly diversified
Reefs recovered in the Middle Triassic, dominated by hexacorals, symbiosis with algae (zooxanthaellae) did not begin until the Latest Triassic and Early Jurassic
Marine Pelagic Life
Dinoflagellate cysts radiated in the Middle Jurassic
Calcareous nannoplankton radiated in the Middle Jurassic, began the sediment coverage of the deep world oceans and is a part of our knowledge of sea floor spreading
Ammonoids and belemnoids (squid-like ammonoids) were important swimming predators
Conodonts present in the Triassic, but extinct in the Jurassic
Ray-finned bony fish, still primitive with scales that did
not cover all of their bodies, swim bladders evolved from primitive
lungs
Sharks were abundant, with many modern forms present, including
tiger sharks
Placodonts marine reptiles that resembled turtles, Triassic only
Nothosaurs first reptiles to invade the sea, paddle-like limbs, lived onshore and in the water, Triassic only
Plesiosaurs more fully marine reptiles, originated in Triassic and by Cretaceous reached lengths of 12 meters (40 feet)
Ichthyosaurs fishlike marine reptiles convergent evolution with dolphin-like mammals
Crocodiles last important early Mesozoic reptiles to evolve, originated in terrestrial conditions in the Triassic, but by Jurassic were adapted to the marine environment
Terrestrial Flora
Land plants were the base of the food web for dinosaurs, thus they will be briefly reviewed first
Land plants did not experience a major mass extinction at the PT boundary, decline of Paleozoic floras (lycopods, sphenopsids, cordaites) started long before the end of the Permian
Ferns and seed ferns survived into the Triassic, but seed ferns went extinct in the Jurassic. Ferns dominate Triassic fossil flora.
Most trees were gymnosperms. The most diverse gymnosperms were the cycadeoids or cycads, followed by conifers and ginkos (gymnosperms = exposed seeds)
Jurassic period called "Age of the Cycads" due to their dominance of forests in the Jurassic
Flowering plants did not evolve until the Cretaceous