Arthropods and Trilobites

Question 1

What is the age range of phylum Arthropoda?

Answer 1

Cambrian to recent

Question 2

What % of all animals described are Arthropods?

Answer 2

75%

Question 3

What ranking debate is there concerning arthropods?

Answer 3

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

Question 4

What variety if there for arthropods?

Answer 4

Position, number and morphology of their limbs

Question 5

Where do Arthropods fall on the group tree?

Answer 5

Metazoa, Bilateria, Protosomes, Ecdysozoa

Question 6

What are phylum arthropoda united by?

Answer 6

Possession of a jointed exoskeleton which is often hard and inflexible

Question 7

What are the advantages of exoskeletons?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

What are the limitations of exoskeletons?

Answer 9

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

Question 10

What % of arthropod mortality arises from Ecdysis?

Answer 10

70%

Question 11

What can an exoskeleton allow to happen within a lifecycle?

Answer 11

allows animals to change morphology (metamorphosis)

Question 12

What is the segmentation of Arthropoda like?

Answer 12

Segments = Metameres
Grouped into Tagmata

Question 13

What does the grouping of segments into tagmata allow for?

Answer 13

feeding
locomotion
sensory systems
visceral elements (gut carrying)

Question 14

What is a sister group of arthropods?

Answer 14

Phylum Onychophora (Cambrian - recent)

Question 15

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

Answer 15

Peripatus (recent)

Question 16

What is a fossil record example of Onychophora?

Answer 16

Hallucigenia (Mid Cambrian), Burgess shale

Question 17

What is a fossil record example of Chelicerata?

Answer 17

Sanctacaris (Mid Cambrian), Burgess Shale

Question 18

What are some examples of present day Chelicerata?

Answer 18

Spiders
Mites
Scorpions

Question 19

What is a group that branches from Chelicerata?

Answer 19

Merostomata

Question 20

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

Answer 20

Xiphosurids (Limulus) - present
Eurypterids - past

Question 21

What was Eurypterid like in its environment?

Answer 21

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

Question 22

What are Chelicerata like at present day?

Answer 22

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

Question 23

What is the fossil record and recent example of Myriapoda?

Answer 23

Centipedes - present
Arthropleura from Carboniferous

Question 24

What is characteristics about subphylum Hexapoda?

Answer 24

They have six legs (limbs) - insects

Question 25

What species dominates the oligostraca group?

Answer 25

ostracods

Question 26

What is the exoskeleton of ostracods like?

Answer 26

Produce bi-valve protective exoskeleton

Question 27

What is the exoskeleton like for Subphylum Vericrustacea?

Answer 27

Folded (almost bi-valve) carapace

Question 28

What is an example of Subphylum Vericrustacea?

Answer 28

Phyllocarids (Mid Cambrian, Burgess / Early Cambrian Chenjiang)

Question 29

What are recent examples of Subphylum Vericrustacea?

Answer 29

Shrimps Crabs Lobsters Barnacles (predominantly marine)

Question 30

What is the age range of subphylum Trilobitomorpha?

Answer 30

Cambrian to Permian

Question 31

What is the environment of Trilobitomorpha

Answer 31

wholly marine

Question 32

How many genera and species of Trilobitomorpha have been described?

Answer 32

>4000 genera (40,000 species)

Question 33

How is Trilobitomorpha's body split?

Answer 33

Longitudinal (length ways "tip to tail")

Question 34

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

Answer 34

Marrella

Question 35

Why are the appendages of Trilobitomorpha rarely preserved?

Answer 35

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

Question 36

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

Answer 36

Burgess shale

Question 37

What is the variation between Trilobitomorpha appendages like?

Answer 37

Minor

Question 38

What do most appendages appear to be like in Trilobitomorpha

Answer 38

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

Question 39

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

Answer 39

The Coxa

Question 40

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

Answer 40

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

Question 41

What are the "tails" at either end of Trilobitomorpha called?

Answer 41

At head - Antenna Tail - Cerci

Question 42

What is the hypostome?

Answer 42

hard mouth part of Trilobitomorpha

Question 43

What are the 3 types of trilobite facial structures?

Answer 43

Proparian Gonatoparian Opisthoparian

Question 44

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

Answer 44

Hard parts Compared to recent forms Distribution in sedimentary environment

Question 45

Where can Opipeuterella be found in the fossil record?

Answer 45

Spitsbergen Ireland Sweden Utah Australia

Question 46

What was the size of Opipeuterella?

Answer 46

1-2 cm length

Question 47

What were the eyes of Opipeuterella like?

Answer 47

Large convex eye (2000 lenses) giving 360 view

Question 48

What do the large eyes of Opipeuterella suggest?

Answer 48

It was pelagic (lived in water column)

Question 49

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

Answer 49

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

Question 50

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

Answer 50

Provided for for powerful musculature (needed for swimming)

Question 51

What is the length to width ratio like for Opipeuterella

Answer 51

3:1 (similar to modern day dimensions)

Question 52

How do we know Opipeuterella was pelagic?

Answer 52

As it appears in both deep and shallow water sediments

Question 53

What is the purpose of the types of facial suture?

Answer 53

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