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2nd Year: Vertebrate Palaeontology > Ornithodira: the saurischian dinosaurs > Flashcards

Ornithodira: the saurischian dinosaurs Flashcards

1
Q

Define a dinosauromorph..

A

Mid-Triassic archosaurs that predecessed the dinosaurs.

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2
Q

Give an example of a dinosauromorph.

A

Marasuchus: 1m long bipedal predator from Argentina

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3
Q

What is the classic small dinosaur body plan? List 5 features.

A
  1. Bipedal
  2. Long neck and tail
  3. Hind limbs bought under the body for balance in bipedalism
  4. Reduced forelimbs
  5. Small head
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4
Q

What kind of predation does bipedalism suggest?

A

Active as opposed to the ancestral ambush.

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5
Q

As well as stance, would there be any other changes in a shift from ambush to active predation?

A

Yes, physiological such as a shift from fast to slow twitch muscle fibre.

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6
Q

What are the 2 major branches of dinosaurs?

A
  1. The ornithischians

2. The saurischians

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7
Q

Define the ornithischians.

A

‘Bird-hipped’ dinosaurs, species are herbivorous.

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8
Q

What way does the pubis point in ornithischians and why?

A

Backwards and down, to create more space for the guts. This is important as plant matter is nutrient poor so large amounts must be consumed.

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9
Q

Define the saurischians.

A

‘Lizard-hipped’

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10
Q

What way does the pubis point in saurischians?

A

Forwards and down

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11
Q

What are the 2 major saurischian clades?

A
  1. Theropoda

2. Sauropoda

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12
Q

Define the theropods.

A

Bipedal carnivores that gave rise to modern birds.

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13
Q

Give 3 synapomorphies of theropods.

A
  1. Open acetabulum: a rim of bone in the hip socket causes the weight to be transferred directly to the ground for bipedalism
  2. An opening between the premaxilla and maxilla
  3. Hyposphene-hypantrum vertebrae: hyposphene on the back of each vertebra locks into the hypantrum at the front of the next. Creates stability.
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14
Q

Why are museum specimens of theropods misleading?

A

In real life they were a lot more vertical in stance

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15
Q

Allosaurus is a characteristic theropod. What time period was it from?

A

The late Jurassic.

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16
Q

How big was allosaurus?

A

6-8m long.

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17
Q

What was the distribution of allosaurus like?

A

Global: North American and European forms are identical, as the Atlantic was just opening up so animals could still wander across.

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18
Q

What was one of the earliest dinosaurs ever found that happened to be a theropod?

A

Herrerasaurus.

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19
Q

What was characteristic about Ceratosaurus, a theropod?

A

It had horny bumps on the skull.

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20
Q

What was Baryonx?

A

A spinosaur, and the largest theropod dinosaur ever at 15m long.

21
Q

When was Baryonx from?

A

The late cretaceous

22
Q

What was characteristic about Baryonx?

A

It was adapted to eating fish, a unique ecological niche for dinosaurs.

23
Q

How do we know Baryonx ate fish? Give 3 reasons

A
  1. Small, conical, non-serrated dentition much like modern crocodiles
  2. Paddle-like hind feet
  3. Fish scales found in stomach contents
24
Q

Allosaurus ripped meat from its prey. How can we tell?

A

Laterally-compressed recurve teeth: these impale prey and prevent it escaping as they point backwards.

25
Q

Albertosaurus, a large theropod, was able to crush bone. How can we tell?

A

Heavily built skull with triangular teeth.

26
Q

What was ornithomimus?

A

A theropod omnivore closely related to birds, had a toothless beak.

27
Q

Theropod dinosaurs hunted alone. True or false?

A

False: there is evidence they hunted in packs

28
Q

Deinonychosaurs were small, predatory relatives of the birds. They have a large, hooked claw on the second toe of their hind foot. What was this for?

A

Originally was thought it was for disembowelling, now thought to have been used for climbing.

29
Q

Define the sauropods.

A

Quadrapedal, long-necked herbivores.

30
Q

Sauropods are saurischians, thus their pelvis points forwards. This means they do not have extra gut space like their relatives the ornithischians. How do they compensate for this?

A

They became super giant.

31
Q

What was plateosaurus?

A

Sauropods that became the first high-browsing tetrapods. Was still bipedal and only 6m tall.

32
Q

As sauropods increased in size, there was a shift from bipedalism to quadrapedalism. True or false?

A

True: they were too heavy for bipedalism.

33
Q

When did sauropods begin to increase in size?

A

The late Triassic to the Jurassic.

34
Q

What was the distribution of saurpods like?

A

Global.

35
Q

Giraffotitan is another name for which sauropod?

A

Brachiosaurus.

36
Q

How tall was brachiosaurus?

A

Its head was 14m above ground.

37
Q

What was argentinosaurus?

A

A titanosaur and the biggest dinosaur to have ever lived, weighing between 50-90 tonnes.

38
Q

The titanosaurs were low in diversity in the Jurassic. When did they radiate?

A

The cretaceous.

39
Q

Define the diplodocoids.

A

A group of sauropods approx. 26m in length.

40
Q

What was characteristic about the skeletons of diplodocoids?

A

They were lightly built and full of air sacs.

41
Q

What was characteristic about the vertebrae of diplodocoids?

A

They had double neural spines on each vertebra. This created a channel for a large ligament involved in pulling the head back, used for stripping vegetation.

42
Q

Brachiosaurus had small, intersecting teeth. How did it feed?

A

By cutting vegetation.

43
Q

In diplodicus the teeth all point forwards and are concentrated at the front end of the snout. How did it feed?

A

The ‘garden rake approach’ - it raked off the softer material from hard branches.

44
Q

Many theropods had different feeding strategies from each other, likewise with the saurpods. Why?

A

They were all successful at the same time and had to diversify to occupy different niches.

45
Q

There are 4 hypotheses as to why the sauropods got so large. What are they?

A
  1. Erect stance: allows direct transferral of body weight to ground, meaning you can be heavier.
  2. Predator-prey arms race
  3. Herbivory: plant matter is nutrient poor and takes 3-4 days for digested food to liberate energy. Larger animals have slower metabolisms.
  4. Competition with other sauropods: each species needed to be taller/longer to reach different vegetation
46
Q

Define scaling.

A

The effect of body size on physiological processes.

47
Q

What kind of SA:V ratio do large animals have?

A

A small SA:V ratio. They would gain and lose heat much slower than small animals.

48
Q

What is an advantage of having a small SA:V ratio?

A

These animals were ectotherms so it ensured a stable metabolism.

2nd Year: Vertebrate Palaeontology (17 decks)

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