Lecture 11

Question 1

What is Tetrapoda?

Answer 1

A superclass

Question 2

When did Tetrapoda arise?

Answer 2

During the Devonian period

Question 3

What kind of organisms did Tetrapods arise from?

Answer 3

Lungfish-like Sarcopterygians

Question 4

Name a few Sarcopterygians

Answer 4

Coelocanths, lungfishes, tetrapodamorph fishes & tetrapods

Question 5

Describe Osteolepiforms

Answer 5

Cylindrical-like bodies, big heads and thick scales

Question 6

Name some of the features that Osteolepiforms shared with tetrapods

Answer 6

Paired crescentic vertebrae and labrynthine teeth

Question 7

What was one feature that was different between tetrapods and osteolepiforms?

Answer 7

Their ribs extended dorsally

Question 8

What is a possible sister group to tetrapods?

Answer 8

Elpistostegalids

Question 9

Elpistostegalids are more derived for shallow water life true or false?

Answer 9

True

Question 10

What did elpistostegalids lose?

Answer 10

Unpaired dorsal and anal fins, their tail was also reduced

Question 11

Name the two organisms that were the earliest known tetrapods until recently

Answer 11

Acanthostega & Ichthyostega

Question 12

What was the recent discovery in regards to tetrapods?

Answer 12

Tiktaalik/Inuktituk fresh water fish seen in the shallows

Question 13

In what period was Tiktaalik/Inuktituk around?

Answer 13

The Devonian period

Question 14

Why was Tiktaalik significant time-wise?

Answer 14

It was 20 my older than acanthostega and ichthyosteag

Question 15

Structurally, why was Tiktaalik significant?

Answer 15

Loss of bony operculum, ribs large & overlapping and forelimbs could bend in the middle

Question 16

What did the loss of the operculum mean for tiktaalik?

Answer 16

It could raise its head up and snap up prey

Question 17

What did large and overlapping ribs mean for tiktaalik?

Answer 17

Its body could be supported for being partially out of the water

Question 18

What is the evidence for the aquatic life of acanthostega and ichthyostega?

Answer 18

Groove on the ventral side of the ceratobranchials to accommodate gill arteries, suggesting internal gills

Question 19

What does polydactyl mean?

Answer 19

More than five toes

Question 20

What digit number was variable across lineages?

Answer 20

Digit 5

Question 21

What Hox gene clusters were responsible for digit development?

Answer 21

There are four gene clusters, HOXA-HOXD

Question 22

When were the earliest known tetrapod tracks found?

Answer 22

Tetrapod trackways were found 18 my before the earliest known tetrapod fossils

Question 23

Where were the tetrapod tracks found?

Answer 23

In the intertidal zone

Question 24

What does the discovery of tetrapod tracks in the intertidal zone tell us?

Answer 24

That tetrapods and elpistostegalids overlapped for >10 my

Question 25

Explain what was found in regards to movement in Icthyostega and current tetrapods

Answer 25

Icthyostega had limited ability to twist its main limb bones so couldn't use ‘normal’ quadrupedal gaits. Couldn't have made tetrapod tracks

Question 26

Describe the classic theory of how tetrapods moved onto land

Answer 26

They moved from pond to pond before they dried out, although unsure as to how this would lead to being on land

Question 27

What is another theory to describe how tetrapods moved onto land (juveniles)?

Answer 27

Juveniles congregated into shallow ponds to avoid predation and then fed on land

Question 28

Describe the theory on how juvenile dispersal helped dispersal onto land

Answer 28

They were smaller and more able to cope with life on land with things like support, respiration & locomotion

Question 29

What anatomical changes could be seen as adaptions to life on land?

Answer 29

Digits (support), ankles & wrists (articulation), pelvic girdle to vertebral column (predatory lunge in water) & distinct head (lifting to breathe)

Question 30

When did the radiation of nonamniotic Palaeozoic tetrapods occur?

Answer 30

Late Devonian to early Cretacious period

Question 31

Describe the habitat of the early Palaeozoic period

Answer 31

High sea & CO2 levels, greenhouse effect, hot and dry, few plants

Question 32

Describe the habitat of the late Ordovician period

Answer 32

Glaciation, cooled some areas, invasion of land by aquatic plants

Question 33

Describe the habitat of the Devonian period

Answer 33

Spread of plants affecting soils & climate change, cooling, soil development, increased weathering of rocks lead to trapped CO2 & high O2

Question 34

Describe the development of the environment in the late Devonian period

Answer 34

Extensive vegetation & stabilised banks enabled a variety of microhabitats. Detrital inputs & wetlands vegetation provided a trophic base for complex food webs. 1st insects

Question 35

Give a brief description of the role of oxygen levels

Answer 35

Low oxygen in mid Devonian favoured lung breathers & high oxygen/low co2 levels late Devonian/carboniferous period favoured insects

Question 36

What were the main groups of Palaeozoic period

Answer 36

Stem tetrapods, Batrachomorphs, Reptilomorphs & Lepospondyls

Question 37

What period is known as the major period of diversification?

Answer 37

The Palaeozoic

Question 38

What are labyrinthodonts?

Answer 38

Stem tetrapods with deeply folded structure of enamel and dentine layers in the teeth

Question 39

Give an example of stem tetrapods

Answer 39

Acanthostega and Ichthyostega

Question 40

What is a Hynerpeton?

Answer 40

Had characteristics of tetrapods like shoulder girdle

Question 41

What are stem amphibians?

Answer 41

Two main groups of Palaeozoic non-amniotic tetrapods, stem amphibians and stem amniotes

Question 42

What is a temnospondyli?

Answer 42

Chubby short lookin crocodile thang

Question 43

What is a large monophyletic group?

Answer 43

Amniotes