Molluscs part 2 - cephalopods and gastropods

Question 1

What are the most common single shelled molluscs?

Answer 1

Cephalopods and gastropods

Question 2

What is the shell growth of molluscs like?

Answer 2

Incrementally grown

Question 3

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

Answer 3

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)

Question 4

How can different shapes of shell be produced in bivalves?

Answer 4

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

Question 5

How can different shapes of shell be produced in gastropods?

Answer 5

gastropods controlled by translation rate (T)

Question 6

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

Answer 6

Iterative evolution

Question 7

What is iterative evolution?

Answer 7

The resurgence/ reoccurrence of morphologies throughout evolution

Question 8

What is an example of iterative evolution of molluscs?

Answer 8

Ammonite in the Jurassic and the Nautiloid in the Silurian

Question 9

How is the Cephalopoda class divided?

Answer 9

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

Question 10

What is the age range of coleoidea?

Answer 10

Carboniferous to recent

Question 11

What are some examples of coleoidea?

Answer 11

Octopuses
Squid
Cuttlefish
Paper nautilus

Question 12

What is the fossil record of coleoidea like?

Answer 12

Typically poor due to being soft bodied except paper-nautilus

Question 13

What is the paper nautilus?

Answer 13

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

Question 14

What will the mineralisation of coleoidea typically be?

Answer 14

Internal (besides Argonauta)

Question 15

What is the scientific name of the paper-nautilus

Answer 15

Argonauta

Question 16

What are the belemnites?

Answer 16

Geologically important group of molluscs with a bullet shape

Question 17

What are the three components of belemnites?

Answer 17

Bullet shaped guard
Alveolus
Pro-ostracum

Question 18

What is the bullet guard?

Answer 18

massive cylinder of calcite
formed through concentric growth

Question 19

Why are belemnites so important?

Answer 19

Used as a standard for Jurassic ocean composition

Question 20

What is the Alveolus of belemnites?

Answer 20

A hollow in the anterior end

Question 21

What is the alveolus filled by?

Answer 21

anteriorly expanding phragmocone
formed from aragonite

Question 22

What will aragonites and calcite look in fossil sample?

Answer 22

Aragonite is shiny
Calcite is dull

Question 23

What does the pro-ostracum look like?

Answer 23

Flattened spatula (used as protection)

Question 24

In what direction does the pro-ostracum project?

Answer 24

Anteriorly

Question 25

What might some soft tissue fossils of belemnites be like?

Answer 25

Show tentacles and hooks Ink sac at shell anterior

Question 26

What is the shell (phramocene) like in Nautoloids?

Answer 26

external

Question 27

How is a nautilus shell internally divided up?

Answer 27

Into chambers (camerae) separated by simple sutures

Question 28

How are the chambers in a nautilus shell connected?

Answer 28

By a siphuncle

Question 29

What is a siphuncle and what is its purpose?

Answer 29

Porous tube needed equalize pressure or transfer gas between chambers

Question 30

How will the siphuncle of nautiloids be positioned?

Answer 30

Central/ subcentral

Question 31

What directions does the septal neck point in nautiloids?

Answer 31

Backwards

Question 32

Where is the body of the nautilus housed?

Answer 32

In the body chamber

Question 33

How can the age of nautilus be predicted?

Answer 33

The body chamber moves forward every 2 weeks

Question 34

What are the internal parts of nautilus's?

Answer 34

Head foot Lateral eyes Hyponome Four gills Tentacles Parrot like jaw

Question 35

What is the purpose of the hyponome?

Answer 35

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

Question 36

What is the name of straight shelled forms of nautilus?

Answer 36

orthocones

Question 37

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

Answer 37

cyrtocones

Question 38

What forms can nautilus be found?

Answer 38

Cyrtocones Planispirals Orthocones

Question 39

When were Nautiloids the dominant cephalopod?

Answer 39

Cambrian to Devonian

Question 40

Where did orthocones and cyrtocones live and hunt?

Answer 40

Near the sea floor

Question 41

What problem is faced by orthocones and cyrtocones?

Answer 41

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

Question 42

How was the buoyancy problem of cyrtocones and orthocones prevented?

Answer 42

thickening of cameral and siphuncular

Question 43

What is the age range of ammonoids?

Answer 43

Lower Dev. - Upper Cret

Question 44

What will ammonites usually be like?

Answer 44

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

Question 45

What is the main basis for ammonite classification?

Answer 45

Sutures

Question 46

What are goniatites?

Answer 46

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

Question 47

How are ceratites identified?

Answer 47

increase in number of saddles and lobes and lobes become frilled

Question 48

How can ammonites be identified?

Answer 48

Due to very high level of suture complexity

Question 49

How can the sexual dimorphism of ammonites be described?

Answer 49

strongly sexually dimorphic

Question 50

How are adult ammonites divided sexually?

Answer 50

Microconch Macroconch

Question 51

What is associated with marcoconches?

Answer 51

Large numbers of embryonic ammonites

Question 52

What are heteromorphic ammonites

Answer 52

Partially uncolied

Question 53

Why is it thought heteromorphic ammonites evolved?

Answer 53

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

Question 54

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

Answer 54

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

Question 55

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

Answer 55

Torsion

Question 56

What is the problem with torsion?

Answer 56

Anus above mouth and dont want to eat poo

Question 57

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

Answer 57

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

Question 58

What is the operculum?

Answer 58

Protective cover like part

Question 59

What characteristics will all gastropods share?

Answer 59

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

Question 60

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

Answer 60

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

Question 61

What are gastropods good at surviving in?

Answer 61

High stress environments

Question 62

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

Answer 62

Leads to high abundance of one gastropods and thus low diversity