M_W_Chapter_21-2A_Later_Paleozoic_Life_partial_short_version...

Paleozoic Life (continued)
•
Mass extinction at end of Ordovician wiped out most
warm-water invertebrates
•
Survivors: cold-adapted animals from high latitudes or
deep water
•
Low diversity in Silurian
•
Marine ecosystem recovered by Devonian

What lived in the Middle and Late
Paleozoic?
•
Marine invertebrates
–
new species of trilobites, brachiopods, corals, graptolites (until
end Silurian) etc.
–
trilobites become less abundant
–
straight nautiloids gradually replaced by the ammonite ancestors
(mostly coiled)
–
“sea scorpions” (Eurypterids) become dominant predators in the
Silurian

Eurypterids
(“Sea scorpions”)
dominant predators in Silurian,
spreading into freshwater environments

What lived in the Middle and Late
Paleozoic?
•
Marine invertebrates
•
Great diversification of fish
Late Silurian and Devonian
-
fish became very abundant
-
Note that a fossil from
Chengjiang (Middle Cambrian)
is believed to be a primitive
jawless true fish)
1. jawless fish

Agnatha (Jawless fish): from Cambrian