Hemichordates (graptolites)

Question 1

What is the age range for the Phylum Hemichordate?

Answer 1

Cambrian to recent

Question 2

What is Phylum Hemichordate united by?

Answer 2

the presence stomochord (convergent with the notochord of chordates) for at
least half their life cycle

Question 3

How does Hemichordate fall into the metazoans?

Answer 3

Bilaterian - deuterostome

Question 4

What is the 3 relationship with hemichordates?

Answer 4

Hemichordates
Echinoderms
Chordates
(super phylum)

Question 5

What can extant hemichordates be divided into?

Answer 5

Pterobranchs
Enteropneusts (acorn worm)

Question 6

What is an example of a modern pterobranch?

Answer 6

Rhabdopleura

Question 7

What are the characteristics of Rhabdopleura? (pterobranch)

Answer 7

Colonial organism
Mouth at base of arms
Individual zooids ciliated, tentacle bearing arms

Question 8

What are the individual zooids like of Rhabdopleura? (pterobranch)

Answer 8

Cephalic shield - with glands secreting zooidal tubes

Question 9

How do Pterobranchs reproduce?

Answer 9

Initially sexually produced zooid generates a stolon which in turn produces other zooids asexually

Question 10

What are the different names for the pterobranchs of the recent and Cambrian?

Answer 10

Recent = Rhabdopleura compacta
Cambrian = Rhabdopleura obuti

Question 11

What are cephalodiscus? (pterobranchs)

Answer 11

Individual zooids which crawl out of the colony and wander onto spines to feed away from low regime of the sea bed

Question 12

What is the age range of Class Graptolithina?

Answer 12

Cambrian to mid-Carboniferous

Question 13

What are the characteristics of class Graptolithinia?

Answer 13

Colonial
Rhabdosome
Periderm - scleroproteinaceous skeleton
Ribbon like cortical bandages

Question 14

How are the cortical bandages produced? (graptolites)

Answer 14

Secreted by zooids

Question 15

How is graptolithinia usually preserved?

Answer 15

Carbonaceous films

Question 16

How are 3d graptolithina extracted from matrix?

Answer 16

Dissolved out of limestone as protein periderm is acid resistant

Question 17

What is the structure of rhabdosome?

Answer 17

Sicula - point of origination
Nema - projection
If Nema buried in colony = Virgula
Zooids housed in Theca
Apertural spines
Stipes

Question 18

What 2 parts can the Sicula be split into?

Answer 18

Protosicula - net like
Metasicula - bandage like

Question 19

How is the colony of rhabdosome (graptolithina) connected?

Answer 19

Connected by a common canal (stolon in pterobranch) runs close to nema

Question 20

What are stipes in rhabdosome?

Answer 20

Branches of thecae

Question 21

How can graptolithina be divided?

Answer 21

Dendroidiea
Graptoloidea

Question 22

What is the age range of Dendroidea?

Answer 22

Mid Cambrian to carboniferous

Question 23

What is the age range of Graptoloidea?

Answer 23

Lower Ordovician to lower Devonian

Question 24

What is the Rhabdosome morphology of Dendroidea?

Answer 24

Multibranched
Numerous stipes
Connecting dissepiments

Question 25

What are the 3 type of thecae in Dendroidea?

Answer 25

Stolothecae - continuous chain Autothecae - large (female?) Bithecae - smaller and narrower (male?)

Question 26

What is Wimans rules?

Answer 26

Triad budding of Thecae with chain of Stolothecae with branches of individual Auto and Bi

Question 27

What are Graptoloidea like in comparison to Dendroidea?

Answer 27

Reduced stipe number Single thecae type = auto Hemaphrodite

Question 28

What was the mode of life of dictyonema?

Answer 28

Thickened nema so thought epifaunal benthic

Question 29

What habitat is dictyonema associated with?

Answer 29

common in shallow water siltstones, sandstones & limestones

Question 30

What was the mode of life of Rhabdinopora?

Answer 30

Weak nema Found in deep water sediments Planktonic

Question 31

What was the feeding method of dendroids?

Answer 31

Passive

Question 32

Why are graptaloids so good for biostratigraphy?

Answer 32

Found in a range of sediments so not facie restricted

Question 33

What evidence is there for automobility of dendroids?

Answer 33

Based on structures which promote/ enhance spinnign and thought that zooids used to "swim" back up the water column

Question 34

What is the function of the thecal spines?

Answer 34

Increase water flow

Question 35

What are the stipe orientations of biserial graptoloids?

Answer 35

scandent (ridges point out) reclined reflexed horizontal deflexed declined pendant (ridge pointing in- rotation of scandent)

Question 36

What is an example of a scandent graptoloid?

Answer 36

Didymograptus bifidus

Question 37

Where is Didymograptus bifidus locally common?

Answer 37

Abereiddy Bay in Pembrokeshire