BISC 120 - Lecture 14: Paleozoic Vertebrate Evolution

Vocabulary practice flashcards covering the key evolutionary transitions, anatomical features, and geologic periods of the Paleozoic Era from BISC 120 Lecture 14.

Paleozoic Era

About 550-250 mya; begins with the Cambrian and ends with the Permian extinction.

~550 mya - Cambrian explosion

Many modern animal phyla appear; first fossil chordates and vertebrates.

Chordate synapomorphies

Notochord and myotomes are shared derived characters of chordates.

~530 mya - early chordates

Pikaia and Haikouella show early chordate traits.

~500 mya - conodonts

Among the first true vertebrates; jawless and with mineralized tooth-like elements.

Agnathan

A jawless vertebrate.

~450 mya - gnathostomes

Jawed vertebrates with true jaws supported by the skeleton.

Gnathostome

A vertebrate with true jaws.

Devonian: 420-360 mya

Called the Age of Fishes because jawed fish diversified greatly.

Sarcopterygians

Lobe-finned bony fish with robust fin bones; the lineage leading to tetrapods.

Tiktaalik

Sarcopterygian with limb-like fins containing a humerus, radius, and ulna.

Acanthostega

Early tetrapod with full limbs and digits, but still mostly aquatic with gills.

Tetrapod

A vertebrate lineage with limbs that evolved from sarcopterygian ancestors.

Carboniferous: 360-300 mya

Amphibians diversify and the first amniotes appear.

Amniote

Tetrapod able to reproduce with an amniotic egg, reducing dependence on water.

Amniotic egg

A land-capable egg that allowed reproduction away from water.

Amniotic egg membranes

Amnion = fluid; yolk sac = nutrients; chorion = gas exchange; allantois = waste.

Carboniferous amniote split

Early amniotes gave rise to Reptilia and Synapsida.

Synapsida

Amniote lineage with one temporal fenestra; mammals are the surviving modern members.

Dimetrodon

Basal synapsid from the Permian; not a dinosaur.

Therapsids

More mammal-like synapsids that became common in the Permian.

Reptilia

Major amniote lineage; lecture notes many reptiles have two temporal fenestrae.

Permian: 300-250 mya

Synapsids and reptiles diversify; Pangaea forms and many regions become hot and dry.

~250 mya - Permian mass extinction

Mass extinction that ends the Paleozoic; massive volcanism is a possible cause.

Paleozoic sequence

Chordates -> jawless vertebrates -> jawed fish -> lobe-fins -> tetrapods -> amniotes -> reptiles + synapsids.