Jawless fishes (exam 3)

What group produced the first vertebates? What features did they give?

Cephalochordates
Bilaterall symmetry
Free-swimming
cephalic sensory structures
gills
without bones, jaws or paired fins

What are the synapomorphies of vertebrates?

Bone
Spine column of vertebrae
Pronounced cephalization

What was the original function for bone?

Phosphate and calcium reserve

What is the name of the first vertebrates?

Conodonts

When did the ostracoderms become abundant? extinct?

Ordovician/Silurian
Late Devonian

What is the synapomorphie of ostracoderms?

Boney armor

Why were ostracoderms very successful?

Made first use of bones and were filter feeders

What are the 2 limitations of ostracoderm?

Heavy armor caused poor swimming and forced benthic style
No jaws

What are the 2 classes of jawless fishes still alive today?

Myxini (hagfish)
Cephalaspidomorphi (lampreys)

What are the key characteristics of hagfish?

No dorsal fin
blind
barbels present
High mucus secretion

What are the key features of the lampreys?

1 or 2 dorsal fins
eyes well developed
barbels absent
teeth on the tongue and oral disc