Arthropods and Trilobites Flashcards

1
Q

What is the age range of phylum Arthropoda?

A

Cambrian to recent

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2
Q

What % of all animals described are Arthropods?

A

75%

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3
Q

What ranking debate is there concerning arthropods?

A

Whether phylum or superphylum
and
If they form a natural (monophyletic) group

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4
Q

What variety if there for arthropods?

A

Position, number and morphology of their limbs

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5
Q

Where do Arthropods fall on the group tree?

A

Metazoa, Bilateria, Protosomes, Ecdysozoa

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6
Q

What are phylum arthropoda united by?

A

Possession of a jointed exoskeleton which is often hard and inflexible

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7
Q

What are the advantages of exoskeletons?

A

Support for soft tissue
Firm site for muscle insertion
Protection (predators and environment change)
Division of skeleton into jointed sections

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8
Q

What is the advantage of exoskeletons dividing the skeleton into jointed sections?

A

Will act as a series of levers allowing for precision in locomotion, feeding etc

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9
Q

What are the limitations of exoskeletons?

A

To grow Ecdysis must occur (moulting) leaving the arthropod vulnerable

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10
Q

What % of arthropod mortality arises from Ecdysis?

A

70%

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11
Q

What can an exoskeleton allow to happen within a lifecycle?

A

allows animals to change morphology (metamorphosis)

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12
Q

What is the segmentation of Arthropoda like?

A

Segments = Metameres
Grouped into Tagmata

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13
Q

What does the grouping of segments into tagmata allow for?

A

feeding
locomotion
sensory systems
visceral elements (gut carrying)

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14
Q

What is a sister group of arthropods?

A

Phylum Onychophora (Cambrian - recent)

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15
Q

What is the closest relative to true (eu) arthropods from Onychophora?

A

Peripatus (recent)

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16
Q

What is a fossil record example of Onychophora?

A

Hallucigenia (Mid Cambrian), Burgess shale

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17
Q

What is a fossil record example of Chelicerata?

A

Sanctacaris (Mid Cambrian), Burgess Shale

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18
Q

What are some examples of present day Chelicerata?

A

Spiders
Mites
Scorpions

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19
Q

What is a group that branches from Chelicerata?

A

Merostomata

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20
Q

What is the present day and fossil record example of Merostomata?

A

Xiphosurids (Limulus) - present
Eurypterids - past

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21
Q

What was Eurypterid like in its environment?

A

In the middle paleozoic shallow water and terrestrial setting it was t

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22
Q

What are Chelicerata like at present day?

A

Predominantly terrestrial (being one of the first to transition to land)

23
Q

What is the fossil record and recent example of Myriapoda?

A

Centipedes - present
Arthropleura from Carboniferous

24
Q

What is characteristics about subphylum Hexapoda?

A

They have six legs (limbs) - insects

25
Q

What species dominates the oligostraca group?

A

ostracods

26
Q

What is the exoskeleton of ostracods like?

A

Produce bi-valve protective exoskeleton

27
Q

What is the exoskeleton like for Subphylum Vericrustacea?

A

Folded (almost bi-valve) carapace

28
Q

What is an example of Subphylum Vericrustacea?

A

Phyllocarids (Mid Cambrian, Burgess / Early Cambrian Chenjiang)

29
Q

What are recent examples of Subphylum Vericrustacea?

A

Shrimps
Crabs
Lobsters
Barnacles
(predominantly marine)

30
Q

What is the age range of subphylum Trilobitomorpha?

A

Cambrian to Permian

31
Q

What is the environment of Trilobitomorpha

A

wholly marine

32
Q

How many genera and species of Trilobitomorpha have been described?

A

> 4000 genera (40,000 species)

33
Q

How is Trilobitomorpha’s body split?

A

Longitudinal (length ways “tip to tail”)

34
Q

What is a burgess shale example of the sister group to Trilobita?

A

Marrella

35
Q

Why are the appendages of Trilobitomorpha rarely preserved?

A

As the ventral side is organic and easily decays
While dorsal side heavily mineralised (calcite)

36
Q

Where is an example of where Trilobitomorpha appendages have been preserved as Lagerstatte?

A

Burgess shale

37
Q

What is the variation between Trilobitomorpha appendages like?

A

Minor

38
Q

What do most appendages appear to be like in Trilobitomorpha

A

Biramous (2 projections) wit a 6 segment walking leg and gill branch for respiration

39
Q

What are the upper and lower leg of Trilobitomorpha attached to?

A

The Coxa

40
Q

What variation with Trilobitomorpha appendages has been identified to show behavioural changes?

A

Gnathobase- goes from smooth and chunky for Eoredlichia and then transition to Sharp edge Naraoia (predatory)

41
Q

What are the “tails” at either end of Trilobitomorpha called?

A

At head - Antenna
Tail - Cerci

42
Q

What is the hypostome?

A

hard mouth part of Trilobitomorpha

43
Q

What are the 3 types of trilobite facial structures?

A

Proparian
Gonatoparian
Opisthoparian

44
Q

What is used to make inferences about Trilobitomorpha mode of life?

A

Hard parts
Compared to recent forms
Distribution in sedimentary environment

45
Q

Where can Opipeuterella be found in the fossil record?

A

Spitsbergen
Ireland
Sweden
Utah
Australia

46
Q

What was the size of Opipeuterella?

A

1-2 cm length

47
Q

What were the eyes of Opipeuterella like?

A

Large convex eye (2000 lenses) giving 360 view

48
Q

What do the large eyes of Opipeuterella suggest?

A

It was pelagic (lived in water column)

49
Q

What meant that Opipeuterella was not adapted to resting on the sediment?

A

cephalon steeply arched cheeks project down well below the pleurae with border
facing down

50
Q

What did a wide convex axis exoskeleton allow for with Opipeuterella?

A

Provided for for powerful musculature (needed for swimming)

51
Q

What is the length to width ratio like for Opipeuterella

A

3:1 (similar to modern day dimensions)

52
Q

How do we know Opipeuterella was pelagic?

A

As it appears in both deep and shallow water sediments

53
Q

What is the purpose of the types of facial suture?

A

important for mode of life
Proparian wider - shovel like
Gonatoparian - streamlined