Hemichordates

Question 1

Hemichordates

Answer 1

Cambrian to recent
Sister groups to chordates
Low diversity
Prosome (head) + mesosome (collar) + metasome (trunk)
Ciliated gill slits
Both dorsal and ventral nerve cord

Question 2

Enteropneusta - “acorn worms”

Answer 2

Cambrian to recent
Solitary organisms
Burrowers - produce a lot of mucus
Straight gut

Question 3

Pterobranchia

Answer 3

Cambrian stage 3 to recent
Colonial organisms (zooids)
Marine + epibenthic organisms
U shaped gut
1 or 2 ciliated gill slits
Organic exoskeleton w/ C shaped half ring
Prosome = arms w/ tentacles

Question 4

Cephalodiscida

Answer 4

Silurian to recent - only a few genera left
Colonies of few individuals

Question 5

Graptolithina

Answer 5

Cambrian to recent
Prominent in the Paleozoic
Many samples have been carbonized

Question 6

Graptolites

Answer 6

Cambrian to recent
Exclusively marine
Colonial skeletons - rhabdosomes - made of C shaped rings
Organisms (zooids) live in the thecae