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Earth history and life - 29202 > Molluscs part 2 - cephalopods and gastropods > Flashcards

Molluscs part 2 - cephalopods and gastropods Flashcards

1
Q

What are the most common single shelled molluscs?

A

Cephalopods and gastropods

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2
Q

What is the shell growth of molluscs like?

A

Incrementally grown

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3
Q

What 4 parameters are used to define the shell shape of molluscs?

A

Shape of generating curve or axial ratio of the shell’s cross-sectional ellipse
Rate of whorl expansion per revolution (W)
Position of generating curve with respect to axis (X)
Whorl translation rate (T)

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4
Q

How can different shapes of shell be produced in bivalves?

A

whorl translation (T) =0 but whorl
expansion (W) is very high

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5
Q

How can different shapes of shell be produced in gastropods?

A

gastropods controlled by translation rate (T)

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6
Q

What is the underlying reason for why shells of molluscs do not occupy all morphospace?

A

Iterative evolution

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7
Q

What is iterative evolution?

A

The resurgence/ reoccurrence of morphologies throughout evolution

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8
Q

What is an example of iterative evolution of molluscs?

A

Ammonite in the Jurassic and the Nautiloid in the Silurian

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9
Q

How is the Cephalopoda class divided?

A

Into 3 subclasses:
1. Coleoidea
2. Nautiloidea
3. Ammonoidea

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10
Q

What is the age range of coleoidea?

A

Carboniferous to recent

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11
Q

What are some examples of coleoidea?

A

Octopuses
Squid
Cuttlefish
Paper nautilus

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12
Q

What is the fossil record of coleoidea like?

A

Typically poor due to being soft bodied except paper-nautilus

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13
Q

What is the paper nautilus?

A

Type of coleoidea which has a very thin mineralised exoskeleton for reproductive purposes

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14
Q

What will the mineralisation of coleoidea typically be?

A

Internal (besides Argonauta)

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15
Q

What is the scientific name of the paper-nautilus

A

Argonauta

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16
Q

What are the belemnites?

A

Geologically important group of molluscs with a bullet shape

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17
Q

What are the three components of belemnites?

A

Bullet shaped guard
Alveolus
Pro-ostracum

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18
Q

What is the bullet guard?

A

massive cylinder of calcite
formed through concentric growth

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19
Q

Why are belemnites so important?

A

Used as a standard for Jurassic ocean composition

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20
Q

What is the Alveolus of belemnites?

A

A hollow in the anterior end

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21
Q

What is the alveolus filled by?

A

anteriorly expanding phragmocone
formed from aragonite

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22
Q

What will aragonites and calcite look in fossil sample?

A

Aragonite is shiny
Calcite is dull

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23
Q

What does the pro-ostracum look like?

A

Flattened spatula (used as protection)

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24
Q

In what direction does the pro-ostracum project?

A

Anteriorly

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25
Q

What might some soft tissue fossils of belemnites be like?

A

Show tentacles and hooks
Ink sac at shell anterior

26
Q

What is the shell (phramocene) like in Nautoloids?

A

external

27
Q

How is a nautilus shell internally divided up?

A

Into chambers (camerae) separated by simple sutures

28
Q

How are the chambers in a nautilus shell connected?

A

By a siphuncle

29
Q

What is a siphuncle and what is its purpose?

A

Porous tube needed equalize pressure or
transfer gas between chambers

30
Q

How will the siphuncle of nautiloids be positioned?

A

Central/ subcentral

31
Q

What directions does the septal neck point in nautiloids?

A

Backwards

32
Q

Where is the body of the nautilus housed?

A

In the body chamber

33
Q

How can the age of nautilus be predicted?

A

The body chamber moves forward every 2 weeks

34
Q

What are the internal parts of nautilus’s?

A

Head foot
Lateral eyes
Hyponome
Four gills
Tentacles
Parrot like jaw

35
Q

What is the purpose of the hyponome?

A

A way to move rapidly/ escape which is done by the mantle cavity rapidly compressing sending out a jet of water for propulsion

36
Q

What is the name of straight shelled forms of nautilus?

A

orthocones

37
Q

What is the name of partially coiled shelled forms of nautilus?

A

cyrtocones

38
Q

What forms can nautilus be found?

A

Cyrtocones
Planispirals
Orthocones

39
Q

When were Nautiloids the dominant cephalopod?

A

Cambrian to Devonian

40
Q

Where did orthocones and cyrtocones live and hunt?

A

Near the sea floor

41
Q

What problem is faced by orthocones and cyrtocones?

A

As shell grows buoyancy is a problem due to a shift in gravity and centre of buoyancy

42
Q

How was the buoyancy problem of cyrtocones and orthocones prevented?

A

thickening of cameral and siphuncular

43
Q

What is the age range of ammonoids?

A

Lower Dev. - Upper Cret

44
Q

What will ammonites usually be like?

A

Shell normally planispiral
Siphuncle is near the venter
Septal necks forwardly directed
Shells ribbed often with tubercles and spines (hydrodynamics)

45
Q

What is the main basis for ammonite classification?

A

Sutures

46
Q

What are goniatites?

A

Most ancient ammonite which can be identified by simple folds of suture

47
Q

How are ceratites identified?

A

increase in number of saddles and lobes and lobes become frilled

48
Q

How can ammonites be identified?

A

Due to very high level of suture complexity

49
Q

How can the sexual dimorphism of ammonites be described?

A

strongly sexually dimorphic

50
Q

How are adult ammonites divided sexually?

A

Microconch
Macroconch

51
Q

What is associated with marcoconches?

A

Large numbers of embryonic ammonites

52
Q

What are heteromorphic ammonites

A

Partially uncolied

53
Q

Why is it thought heteromorphic ammonites evolved?

A

As there was a transition form living in the water column to living near the sea floor

54
Q

What is the general info about habitat and feeding of gastropods?

A

Wide variety of ecological niches
Marine, freshwater and terrestrial
Creeping, floating and swimming
Grazing, suspension feeding, predatory and parasitic

55
Q

What process have gastropods have experienced which makes them have their mouth and anus be so close?

A

Torsion

56
Q

What is the problem with torsion?

A

Anus above mouth and dont want to eat poo

57
Q

What does the mantle cavity being above the head allow for in gastropods?

A

mantle cavity and gills rotated to above the head allows head to be retracted into shell before the foot - which carries
the operculum

58
Q

What is the operculum?

A

Protective cover like part

59
Q

What characteristics will all gastropods share?

A

All have true head, usually with tentacles and eyes more or less continuous with the body, visceral elements lie within the shell

60
Q

How did gastropods adapt to combat the effect of their anus being above their mouth?

A

Development of siphons
Slit band (scar allows siphon out of side)

61
Q

What are gastropods good at surviving in?

A

High stress environments

62
Q

What is the effect of the fossil record due to gastropods being able to survive high stress environments?

A

Leads to high abundance of one gastropods and thus low diversity

Earth history and life - 29202 (29 decks)

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