Middle Paleozoic Life
End Ordovician Extinction-reradiation in the Silurian
Better Reef Builders
Decline of Trilobites
GRAPTOLITE evolution
Evolution of Fish and Swimming Predators
Not many new body types, but diversification within the major groups
Coral Strome Reefs:
Pioneer phase-rugose corals and some tabulate corals
Intermediate phase-hemispherical bryozoa, tabulate corals
Mature-large reefs with Stromatoporoids and back lagoon area, crinoids also common
Silurian: First early land plants, Jawless fishes, earliest Jawed fishes
Devonian: Seed plants, first insects, ammonoids, trees, and amphibians
Ammonoids became important predators (swimming-nektonic)
Euripterid Arthropods (scorpion relatives)-brackish to fresh water environments
FISH-Devonian is the “Age of the Fishes”
Silurian and Devonian have diverser, fully preserved fish for the first time-also in fresh water
Ostracoderms (“bony skinned fish”)-lacked jaws, and probably had cartilege skeletons
Jawed fish appear late in Silurian (Acanthodians)-paired fins, scales, jaws all common to later
fishes. Jaws probably derived from the gill support structure of ancestor fish
Sharks most important fish in the Devonian
Placoderms-armored fish of the Devonian-some up to 7 meters long
Ray-finned fishes-ancestors to most modern fish, thin bones radiate from body to support fins
Fish with Lungs are part of the group of Lobe finned fishes
Coelacanths modern example.
Lobe finned fish gave rise to the Amphibians and the invasion of the land
Rise of Fish and other swimming predators = decline of Trilobites?
Vascular Plants
Spore bearing plants in the Silurian, vascular plants in the Devonian
Spore bearing plants need a lot of moisture, seed bearing plants in the Devonian allowed for
invasion of drier climate zones-TREES
Amphibians: return to water to lay their eggs and live their juvenile life
ICHTHYOSTEGA-intermediate between lobe finned fish and amphibians, sometimes
called Labyrithodonts (for the structure of their teeth)
Lung fish used it occasionally-“opportunism” of evolution for labyrithodonts…
Evolution of trees and shade on land aided amphibians protection from the sun