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Earth history and life - 29202 > Hemichordates (graptolites) > Flashcards

Hemichordates (graptolites) Flashcards

1
Q

What is the age range for the Phylum Hemichordate?

A

Cambrian to recent

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2
Q

What is Phylum Hemichordate united by?

A

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

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3
Q

How does Hemichordate fall into the metazoans?

A

Bilaterian - deuterostome

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4
Q

What is the 3 relationship with hemichordates?

A

Hemichordates
Echinoderms
Chordates
(super phylum)

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5
Q

What can extant hemichordates be divided into?

A

Pterobranchs
Enteropneusts (acorn worm)

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6
Q

What is an example of a modern pterobranch?

A

Rhabdopleura

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7
Q

What are the characteristics of Rhabdopleura? (pterobranch)

A

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

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8
Q

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

A

Cephalic shield - with glands secreting zooidal tubes

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9
Q

How do Pterobranchs reproduce?

A

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

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10
Q

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

A

Recent = Rhabdopleura compacta
Cambrian = Rhabdopleura obuti

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11
Q

What are cephalodiscus? (pterobranchs)

A

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

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12
Q

What is the age range of Class Graptolithina?

A

Cambrian to mid-Carboniferous

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13
Q

What are the characteristics of class Graptolithinia?

A

Colonial
Rhabdosome
Periderm - scleroproteinaceous skeleton
Ribbon like cortical bandages

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14
Q

How are the cortical bandages produced? (graptolites)

A

Secreted by zooids

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15
Q

How is graptolithinia usually preserved?

A

Carbonaceous films

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16
Q

How are 3d graptolithina extracted from matrix?

A

Dissolved out of limestone as protein periderm is acid resistant

17
Q

What is the structure of rhabdosome?

A

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

18
Q

What 2 parts can the Sicula be split into?

A

Protosicula - net like
Metasicula - bandage like

19
Q

How is the colony of rhabdosome (graptolithina) connected?

A

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

20
Q

What are stipes in rhabdosome?

A

Branches of thecae

21
Q

How can graptolithina be divided?

A

Dendroidiea
Graptoloidea

22
Q

What is the age range of Dendroidea?

A

Mid Cambrian to carboniferous

23
Q

What is the age range of Graptoloidea?

A

Lower Ordovician to lower Devonian

24
Q

What is the Rhabdosome morphology of Dendroidea?

A

Multibranched
Numerous stipes
Connecting dissepiments

25
Q

What are the 3 type of thecae in Dendroidea?

A

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

26
Q

What is Wimans rules?

A

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

27
Q

What are Graptoloidea like in comparison to Dendroidea?

A

Reduced stipe number
Single thecae type = auto
Hemaphrodite

28
Q

What was the mode of life of dictyonema?

A

Thickened nema so thought epifaunal benthic

29
Q

What habitat is dictyonema associated with?

A

common in shallow water siltstones, sandstones & limestones

30
Q

What was the mode of life of Rhabdinopora?

A

Weak nema
Found in deep water sediments
Planktonic

31
Q

What was the feeding method of dendroids?

A

Passive

32
Q

Why are graptaloids so good for biostratigraphy?

A

Found in a range of sediments so not facie restricted

33
Q

What evidence is there for automobility of dendroids?

A

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

34
Q

What is the function of the thecal spines?

A

Increase water flow

35
Q

What are the stipe orientations of biserial graptoloids?

A

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

36
Q

What is an example of a scandent graptoloid?

A

Didymograptus bifidus

37
Q

Where is Didymograptus bifidus locally common?

A

Abereiddy Bay in Pembrokeshire

38
Q
A

Earth history and life - 29202 (29 decks)

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