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1A Earth > Practical Work - Fossils > Flashcards

Practical Work - Fossils Flashcards

1
Q

What anatomical orientations can be drawn?

A 
Dorsal (top view)
Ventral (bottom view)
Anterior (front view)
Posterior (back view)
Left
Right
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2
Q

By convention, which way is the umbo oriented and pointing for bivalves?

A

Dorsal and oriented upwards

Pointing towards the anterior

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3
Q

Concentric parallel lines on a bivalve’s shell indicate what kind of growth?
How could something about the past climate be inferred from the shell?

A

Accretionary

Isotope ratios for oxygen etc

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4
Q

Which labels can be added on an interior sketch of a bivalve shell?

A 
Pallial line
Pallial sinus
Umbo
Tooth and socket zone
Adductor muscles (posterior and anterior)
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5
Q

What was the purpose of both the adductor muscles and the ligaments in a bivalve?

A

Adductors for closing the shell

Ligaments for opening the shell

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6
Q

How did the ligaments of a bivalve open the shell?

Why does this lead to most bivalves being found open or disarticulated?

A

They were elastic

The natural state of the bivalve was open so unless buried in sediment, they would die like this/open after death

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7
Q

What was the purpose of the tooth and socket zone in a burrowing bivalve?

A

Keep the valves aligned when burrowing, no rotation

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8
Q

What does the presence of a prominent pallial sinus in a bivalve shell indicate?

A

Deep burrower

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9
Q

How do bivalves secrete new shell material?

Why are no growth lines apparent on the inside of the shell?

A

The mantle must extend out beyond the pallial line to lay down new shell, but is not permanently attached at that point
New shell is deposited across the entire inner surface of the shell

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10
Q

How do brachiopods differ from bivalves in terms of movement?

A

Brachiopods are sessile, they can’t move or burrow

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11
Q

How do brachiopods attach themselves to a surface?

A

A pedicle, a fleshy stalk at the posterior

It comes out the pedicle valve

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12
Q

What is the symmetry of a brachiopod?

A

Bilateral symmetry

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13
Q

How do brachiopods open and close their shell?

A

Diductor muscles open

Adductor muscles close

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14
Q

Why are brachiopods more often found closed than bivalves are?

A

Different tooth and socket positioning means a larger surface area remains closed
Lower chance of disarticulation
No ligament that automatically opens the valves

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15
Q

What kind of feeders are bivalves and brachiopods?

A

Suspension feeder

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16
Q

What is the lophophore structure in a brachiopod used for?

A

Feeding

Gas exchange

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17
Q

What factors have led to the success of bivalves and marginalisation of brachiopods in terms of diversity?

A

Brachiopods were more susceptible to mass extinction, particularly the end Permian
Bivalves have a greater range of functions such as mobility and burrowing

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18
Q

Which features can be labelled on a trilobite?

A 
Cephalon (head)
Pygidium (tail)
Thorax (middle part)
Glabella
Compound eye
Facial sutures (lines on the head)
Free cheek
Thoracic segment
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19
Q

What is the nature of the segmentation of each of the three body parts in a trilobite?

A

Cephalon: fused, differentiated and highly integrated segments
Thorax: simple unfused segments
Pygidium: simple fused segments

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20
Q

How does the level of integration of each body part in a trilobite relate to its function?

A

Cephalon: for mechanical integrity
Thorax: allows movement and enrollment
Pygidium: mechanical stability, helps enrollment

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21
Q

How does the segmentation in a trilobite affect the preservation of the fossil?

A

Thoracic segments are prone to disarticulation

Pygidium and cephalon tend to remain intact

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22
Q

How does a trilobite grow?

What are the two ways it can perform this?

A

Moulting the exoskeleton and growing a new one (ecdysis)

Exit from underneath, or between the cephalon/thorax

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23
Q

How can you tell if a trilobite fossil is a moult or a carcass?

A

A carcass will be fully articulated and free cheeks still attached

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24
Q

What may have been the function of the trilobite appendages, both the segmented and the frilled parts?

A

Frilled part like a gill so gas exchange

Segmented part for movement/burrowing

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25
Q

What are trilobites likely to have done for a living?

A

Sift the sediment of the sea bed

Process small prey and detritus

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26
Q

Which features can be labelled on an echinoid?

A 
Apical system
Ambulacral area
Inter ambulacral area
Periproct
Pore pairs
Tubercle
Ambulacral pores
Peristome
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27
Q

Which features are lost in an echinoid between death and semi-mummification?
If treated with bleach, what else would be lost?

A

Behaviour, internal soft parts, tube feet

External epidermis, spines, Aristotle’s lantern

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28
Q

How do echinoids grow their skeleton?

A

Addition of new ossicles and accretionary growth/remodelling of existing ones

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29
Q

How can the ecological habit of an echinoid be inferred from the observable features/missing features?

A

Ambulacral pores indicate a water vascular system and mobility
Presence of spines indicates whether infaunal/epifaunal
Pentaradial symmetry and Aristotle’s lantern so a grazer/scavenger

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30
Q

What are the three principal parts of a crinoid?

A

Calyx
Crown
Stalk

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31
Q

Which four kinds of ossicles of a crinoid can be seen in a fossil?

A

Crown ossicle
Calyx ossicle
Stalk ossicle (penta-radial symmetry)
Stalk-arm ossicle (called cirri)

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32
Q

What did crinoids do for a living?

A

Marine, suspension feeder

Water passed through the crown and minerals were picked up

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33
Q

Why did stalked crinoids disappear from shelf settings in the late Mesozoic and Cenozoic?

A

Permanently attached to a substrate with a long exposed stalk is easily preyed upon

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34
Q

If a surface is well preserved, what does this indicate with respect to burial?
How might crinoids be preserved well?

A

Buried very rapidly

Rapidly buried in a storm deposit

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35
Q

If crinoids are attached to wood, how might that explain good preservation?

A

Attached to floating log
Log eventually sunk into anoxic bottom waters so those on the bottom would be preserved, but the ones on top would decay and disarticulate

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36
Q

Why can graptolites and bryozoans be identified as colonial?
How would the soft bits have been distributed?
What is the genetic relationship between individual zooids?

A

Multiple compartments
Coordinated colony so interconnected soft parts
Genetically identical clones

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37
Q

What is the nature of the bryozoan skeleton?
How did it grow?
Is the colony genetically or environmentally controlled?

A

Calcite
Accretionary on existing zooids, additive for new zooids
Environmentally controlled

38
Q

What is the nature of the graptolite skeleton?
How did it grow?
Is the colony genetically or environmentally controlled?
Why is it useful that the colony is controlled this way?

A

Carbonaceous skeleton
Primarily additive
Genetically determined colony form
Helps with biostratigraphy

39
Q

What is the palaeoecology of bryozoans?

Why can’t it move?

A 
Marine
Benthic
Sessile
Epifaunal
Suspension feeders
The calcitic skeleton is massive and immobile
40
Q

What is the palaeoecology of graptolites?

A

Marine
Pelagic
Planktic
Suspension feeders

41
Q

What are some of the ecological or evolutionary advantages of living in a colony? (bryozoans/graptolites)

A

The colony can survive if some die
Environmental buffer
Large scale forms can generate hydrodynamic properties
Individuals can become specialised

42
Q

Why are graptolites such great index fossils?

A

Planktic
Superabundant
Evolved rapidly in Ord-Dev
Taxa are distinctive and easy to identify
Anoxic conditions required for preservation were prevalent at that time

43
Q

Which features can be labelled on a coral if they are present?

A 
Corallum
Calice
Septa
Columella
Epitheca
Growth lines (if solitary)
Tabulae
Dissepiments
Apex (if solitary)
Coenosteum (if colonial)
44
Q

What are the three coral types?

A

Rugose
Tabulate
Scleractinian

45
Q

How do you tell apart the three coral types?

A 
Tabulate = no septae, Rugose = bilateral symmetry in septae, Scleractinian = hexa radial symmetry in septae
Tabulate = always colonial, Rugose/scleractinian = colonial or solitary
Tabulate/scleractinian = high level of integration in colony
Fossilised = more likely to be rugose or tabulate
46
Q

What do the coral types mineralise in?

A

Scleractinian in aragonite

Tabulate and rugosa in calcite

47
Q

What is the higher-order taxonomy for corals?

A 
Domain - Eukaryota
Kingdom - Metazoa
Phylum - Cnidaria
Class - Anthozoa
Order - Scleractinia/Tabulate/Rugose
48
Q

What kind of integration is expected to be seen in the colonial forms of each coral type?

A

Scleractinia: highly integrated, often no walls between individual corallites
Rugose: no integration, just loosely packed corallites
Tabulate: substantially integrated, significant amounts of coenosteum

49
Q

Looking at a fossilised stem in thin section, what would allow you to say it was from an embryophyte?

A

Tissue differentiation

50
Q

What were the advantages of growing larger and taller for early plants?
Why aren’t they even taller/larger?

A

More sunlight exposure, greater distribution of spores

Required structural reinforcement and a good vascular system (wood not evolved yet)

51
Q

What are the similarities between early spore-bearing plants and mosses?

A

Terminal sporangia
No vascular system
No real roots

52
Q

What is the diagenesis of Rhynie Chert?

What makes the colour in the thin section?

A

Quartz permineralised - from a hot spring - plant nearby

A small amount of organic material left

53
Q

Why is stomatal density currently on a downward trend in trees?

A

Rise of atmospheric CO2 since the industrial revolution

54
Q

Bituminous coal can have a characteristic banded fabric of alternating vitrinite (reflective, conchoidal fractures) and liptinite (duller background material), what may be the sources of these?

A

Vitrinite derives from mostly solid wood

Liptinite from leaf cuticle, spore walls etc

55
Q

How do peat and anthracite coal differ from bituminous coal in terms of fabric?

A

Peat is uncompacted plant material so just has regular vertical layering
Anthracite coal is more homogeneous due to metamorphic overprinting

56
Q

What is the depositional environment of bituminous coal, including the hydrological regime?

A

Stagnant
Low oxygen
Low pH
Continuous rainfall

57
Q

What makes ammonoids useful for biostratigraphy?

A

Three types - ammonitic, ceratitic and goniatitic

They have distinct suture lines for these species and time frames

58
Q

What was the likely palaeoecology of ammonoids?

How does the habit make it useful for biostratigraphy

A

Marine, pelagic, nekton, predator

Remains spread widely

59
Q

How can the increasingly complex suture lines in ammonoids be explained?

A

Possibly shell strengthening

60
Q

What is the biomineral for belemnites?
What is the mode of growth?
Describe the arrangement of the crystals

A

Calcite
Accretionary growth (laterally)
Large and radially oriented

61
Q

What do the growth lines for a belemnite indicate about the position of the secretory tissue and the guard relative to the squid?

A

Guard was inside the squid

Surrounded by secretory tissue

62
Q

Why are belemnites suitable for oxygen isotope measurements?

A

Solid macrocrystalline calcite

Somewhat immune to diagenesis

63
Q

In the evolution from an epifaunal to an infaunal echinoid, how does the test change?

A

More flat, more gently curved anterior, steeper posterior

Pentaradial symmetry develops into bilateral symmetry

64
Q

How do the tubercles change in the evolution from an epifaunal to an infaunal echinoid?

A

Tubercles decrease in size

Tubercles increase in density

65
Q

How have the openings moved in the evolution from an epifaunal to an infaunal echinoid?
Why?

A

Anus moves from the top to the posterior
Mouth moves to the anterior
Feeding on the sediment as they move forward in it

66
Q

How do the pore pairs change in the evolution from an epifaunal to an infaunal echinoid?
What did the increased surface area provide?

A

Pore pairs become non-symmetrical
One pore is circular, the other is a thin slit
Increased gas exchange and feeding

67
Q

If a dead echinoid is encrusted with worms, how can you tell if they were around at death or came after?

A

If after death, worms encrust over disarticulated spines or cover the mouth/peristome

68
Q

What do infaunal echinoids feed on?

How has their skeleton been adapted for this?

A

Detritus feeders
Spines reduced in size (easier movement)
Vertical tube for ventilation
Trailing tube for waste

69
Q

Why are trace fossils for infaunal echinoids hard to find?

What are the consequences of extensive feeding?

A

Destruction by bioturbation

Ventilation and mixing of sediments

70
Q

Why did the rise of infaunal echinoids and bivalves coincide with a decline in free lying brachiopods?

A

Mud sitting brachiopods didn’t fare well when their substrate was constantly being turned over

71
Q

Why have infaunal echinoids been so successful since they evolved?

A

Rise in predators during their evolution like fish and crustaceans, safe in the sediment

72
Q

Why does the probability of extinction remain constant?

A

While the prey evolves to be better at avoiding predators, the predators also evolve to get better at catching the prey
No real ground gained

73
Q

How do benthic forams grow?

A

Coiled accretionary skeletons with the outer wall enveloping all previously formed shell

74
Q

How are fusilinids and nummulite LBFs similar/different in terms of overall form, internal compartmentalisation, wall microstructure and mode of life?

A

Both are large accretionary structures with spiral geometry, but fusilinids are more drawn out
Both have inter-connected compartments, but fusilinids have more open space
The microstructure of fusilinids is granular vs the larger crystalline habit of nummulites
Both live in shallow water carbonates settings

75
Q

What do benthic forams do for a living?

Why do they have a high level of diversity?

A

On the seafloor eating detritus etc

A diverse range of environments at the microscopic range

76
Q

What are the three types of benthic forams?

A

Agglutinating
Hyaline
Porcellaneous

77
Q

How do planktic forams differ from benthic forams?

A

Generally thin-walled
Often porous
Often with inflated chambers
No agglutinating or porcellaneous

78
Q

When are gastropods index fossils for?

A

Very common in the Cenozoic (but have been present throughout even as far back as Cambrian)

79
Q

When are Megalodon teeth index fossils for?

A

Mid Cenozoic

80
Q

Outline the shell of an ammonoid

A

Planispiral coiled shell
Shell has chambers separated by septa that meet the shell wall at a suture
Chambers joined by a tube (siphuncle) through the outer edge of each septum
Chambers contain gas/fluid to control buoyancy

81
Q

How are ammonoids often preserved?
What is revealed in this preservation?
Why are they preserved this way?

A

As internal moulds
Suture lines
Aragonite shells

82
Q

When are the three types of ammonoids index fossils for?

A

Goniatites: Mid Devonian to end Permian
Ceratites: Triassic
Ammonites: Jurassic and Cretaceous

83
Q

When are the types of nautiloids index fossils for?

A

Coiled and straight forms: Ordovician to end Permian

Coiled only: Triassic to now

84
Q

When are belemnites index fossils for?

A

Very common in Jurassic and Cretaceous

85
Q

When are bivalves good index fossils for?

A

Very common in Cenozoic

Somewhat common in Mesozoic

86
Q

When are brachiopods good index fossils for?

A

Very common Ordovician to end Permian

Common Triassic to end Cretaceous

87
Q

When are the coral forms good index fossils for?

A

Rugose and Tabulate: early/mid-Ordovician to end Permian

Scleractinian: mid-Triassic to now

88
Q

When are echinoids good index fossils for?

A

Regular echinoids: mid-Ordovician to now
Irregular echinoids: Jurassic onwards
Very common from Jurassic to now

89
Q

When are crinoids good index fossils for?

A

Carboniferous and Permian

90
Q

When are graptolites good index fossils for?

A

Ordovician and Silurian

91
Q

When are trilobites good index fossils for?

A

Very common in early Palaeozoic (Cam-Sil)

92
Q

With trilobites, when would few segments and a roughly equally sized cephalon and pygidium be indicative of?

A

Early Cambrian

1A Earth (15 decks)

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