Graptolites

Question 1

Describe hemichordates and name the two classes

Answer 1

A phylum of bilateral soft-bodied invertebrates, with classes enteropneusta (acorn worms) and pterobranchia

Question 2

Describe the class pterobranchia

Answer 2

Minute, fixed, colonial, deap-sea organisms what secrete an external cuticular skeleton. Includes graptolites.

Question 3

Where are graptolite fossils commonly found?

Answer 3

Lower Palaeozoic black shales

Question 4

What is the possible phylogeny of extant pterobranchia?

Answer 4

Highly derived graptolites

Question 5

When do hemichordates first appear in the fossil record and when did they peak?

Answer 5

First appear in Cambrian rocks and peak in the Ordovician

Question 6

Why do deeper water fauna often appear more diverse?

Answer 6

More fossils in rocks that are deposited in deeper waters. Fossil abundance is also a proxy for sea level.

Question 7

What is the sicula of a graptolite?

Answer 7

The skeleton of the initial zooid of a colony of graptolites. The apex from which it grows

Question 7

What are the stipes of a graptolite?

Answer 7

The branch of a colony, coming from the sicula.

Question 8

What is the theca of a graptolite?

Answer 8

A cup-like structure along the stipe. Each houses a zooid.

Question 9

What is the nema of a graptolite?

Answer 9

The long, hollow, thread-like structure that extends beyond the sicula

Question 10

Describe the graptolite order Dendroidea

Answer 10

Middle Cambrian to Lower Carboniferous. Benthic but occasionally planktonic.

Question 11

Describe the graptolite order Graptoloids

Answer 11

Lower Ordovician to Lower Devonian. Probably free-floating as there is no evidence for attachment structures. Filter feeders.