Lesson 6: Attack and Defense Flashcards

1
Q

Recall: What adaptations for attack/defense did tyrannosaurs, dromaeosaurs, ceratopsians, ankylosaurs and stegosaurs have?

A

Bone crushing jaws, sickle claws, big horns, and an array of spikes and armor.

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2
Q

What are deterrents?

A

Spikes, armor and horns act as deterrents, discouraging predators from attacking in the first place.

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3
Q

Based on their hind limb proportions, ornithomimids and many small ornithopods are ___ ___, and it is likely that these dinosaurs made use of their speed when threatened.

A

Cursorially adapted.

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4
Q

What are cryptic adaptations?

A

Crypsis is the ability of an animal to avoid detection, and cryptic adaptations include camouflage color patterns, hiding behaviors, and odor-masking chemicals. Crypsis is difficult to judge from only fossil evidence.

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5
Q

Finite element analysis is a technique that has been used by paleontologist to help evaluate hypotheses about the functions of many dinosaur adaptations. What is it?

A

Finite element analyses are computer simulations that apply set material properties to a digital object and that report data on how stresses are dispersed through the object, when a force is applied at a particular point.

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6
Q

A recent finite element analysis carried out by University of Alberta researchers attempted to evaluate the hypothesis that the tail cubs of ankylosaurs were used as weapons. Describe the process that was used.

A

The tail club of the ankylosaur Euoplocephalus was digitally scanned, and this digital model was then imported into a finite element analysis program. The digital tail club model was given material properties equivalent to that of bone. To simulate a tail club strike, the force of a Euoplocephalus tail swing was estimated and was applied to a point on the outer surface of the digital tail cub model.

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7
Q

What are some ways we can determine how well dino’s see, hear and smell?

A

The brain cases of dinosaurs offer some clues, because the sizes of different regions of the brain relate directly to the strength of specific senses. Eye size can be estimated from the size of the orbits, and the inner ear cavity of the skull offers many clues to the strength of a dinosaur’s hearing.

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8
Q

How do the sensory needs of predators and prey differ?

A
  1. Prey needs a wide field of vision and usually has eyes on the sides of its head.
  2. Predators benefit from being able to maximize their perception of a single target and usually have eyes near each other and facing forward.
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9
Q

What is stereoscopic vision?

A

Stereoscopic vision allows an animal to see the same object with both eyes, and thus to see it from two slightly different angles, which improves the animal’s ability to judge depth.

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10
Q

What are some different hunting styles among extant predators?

A

Some hunters are ambush predators, which lie in wait until prey comes within striking distance – a good example of this kind of hunting strategy is a crocodile, waiting for prey to enter the water, then lunging. Other hunters stalk and pursue prey, and may rely on stealth to approach quietly and then strike (large cats, also need sprint speed). Still others, like wolves, may pursue prey over long distances, using their endurance to tire out and eventually overtake their prey (wolves).

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11
Q

What are social predators?

A

Hunters that work cooperatively to acquire prey that would be too difficult to kill on their own. The downside of this is sharing the kill.

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12
Q

Hunting behaviours can be diverse even among closely related animals. Give an example.

A

For example, tigers are solitary hunters, lions hunt cooperatively, and cheetahs sometimes hunt alone and sometimes hunt in pairs or small groups.

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13
Q

In Dry Island Buffalo Jump Provincial Park in Alberta, a bonebed of the tyrannosaurid theropod Albertosaurus preserves the remains of more than 20 individuals. What does this suggest?

A

This seems to suggest that Albertosaurus may have lived in groups rather than as solitary individuals. But there are other reasons why many individual dinosaurs may have collected in one spot. However, the geological and taphonomic evidence at Dry Island suggests that these Albertosaurus represented a single pack that met some catastrophic end. It appears that at least some theropod dinosaurs formed groups, and therefore may have been social hunters.

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14
Q

An incredible fossil, called the “Fighting Dinosaurs”, from Mongolia preserves a Velociraptor (a dromaeosaurid theropod) and a Protoceratops (a ceratopsian) seemingly interacting with each other. One hand of the Velociraptor is in the mouth of the Protoceratops, and the other is holding on to the frill of the Protoceratops. The Velociraptor’s sickle-shaped claw is positioned in the throat of the Protoceratops. What does this suggest?

A

This amazing fossil pair seems to be a snapshot of a Velociraptor in the midst of killing a Protoceratops, and provides support for the use of the sickle-shaped toe claw as a predatory adaptation. Based on this fossil, we might guess that Velociraptor was a solitary hunter. However, maybe other Velociraptor were present, but were able to escape whatever killed the Fighting Dinosaurs.

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15
Q

What are agonistic behaviors?

A

It is common for members of the same species to fight over territory, mates, food resources, and for social rank within a group. Fighting and aggressive displays between members of the same species are called agonistic behaviors.

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16
Q

What is ritualized agonistic combat?

A

This kind of competition determines which of two individuals is the strongest without either combatant risking serious injury. A good example is male elk and their antlers.

17
Q

It has long been suspected that the thick domed skulls of many pachycephalosaurs were adaptations for agonistic head butting competitions. What supports this?

A

Finite element analyses of pachycephalosaur (Stegoceras) skulls have supported this hypothesis. Like modern animals that engage in ritualized agonistic head butting, such as musk oxen and big horn sheep, pachycephalosaur skulls were strong enough to withstand severe impact forces and had special mechanical stress reducing adaptations.

18
Q

What is evidence supporting dinos in groups?

A

Evidence of dinosaurs forming groups comes from a variety of social display adaptations and adaptations relating to agonistic behaviors and from trackways and monospecific bonebeds.

19
Q

Some ___ and ___ trackways show many sets of footprints, all from the same species of dinosaur and all heading in the same direction. These trackways suggest that the dinosaurs that made them were traveling together as a group.

A

Sauropod and ornithopod.

20
Q

What are monospecific bonebeds?

A

Monospecific bonebeds are large accumulations of fossil bones that are all from multiple individuals of the same species. Monospecific bonebeds are known for many kinds of dinosaurs, including ceratopsians, hadrosaurs, and tyrannosaurs (like the Albertosaurus at Dry Island).

21
Q

A locality called Bayan Mandahu in China preserved the articulated skeletons of juvenile ankylosaurs called Pinacosaurus, lined up next to each other like they had laid down to sleep. What is this evidence for?

A

This is very good evidence that juvenile Pinacosaurus (lacked armour of adults) traveled in groups. Adult Pinacosaurus have never been found in groups or bonebeds, which suggests that, while juvenile Pinacosaurus were social dinosaurs, adult Pinacosaurus lived solitary lives.

22
Q

Juvenile tyrannosaurs had proportionately longer legs, which would have made them more fleet-footed than the stockier, more heavily-built adults. What does this suggest?

A

Perhaps young tyrannosaurs hunted smaller and faster prey, while adults were better able to attack larger and slower prey. Alternatively, the more cursorial limbs of young tyrannosaurs may have been a defensive strategy that helped the youngsters to avoid themselves becoming prey for adults.

23
Q

Another source of potential information about dinosaur inter- or intraspecific interactions is the presence of pathologies. What does this include?

A

Palaeopathologies can include healed injuries or other evidence of diseases, such as infections, cancer, or arthritis. The cause of many pathologies can have multiple interpretations, so be careful.

24
Q

Nonlethal face biting is a common agonistic behavior among modern carnivores, such as crocodiles. Which dinosaur may have also exhibited this?

A

Several tyrannosaur skulls show signs of healed bite marks that can only have been made by other tyrannosaurs. Because the injuries had time to heal, these bite marks cannot have been formed by a tyrannosaur killing and feeding on the carcass of another.

25
Q

Adaptations that serve in predator defense may also be used in agonistic behaviors. Give an example.

A

A study examining healed injuries on skulls of two different species of ceratopsians found that injuries on the squamosal bone were more common in Triceratops than in Centrosaurus. This provides some evidence that Triceratops may have locked horns during intraspecific competitions similar to those of modern deer, cattle, and rhinos. Centrosaurus has smaller orbital horns, and there weren’t as many healed injuries on the squamosal, which might mean that the orbital horns were too small to cause injuries in that area, or that Centrosaurus did not use its cranial ornamentation for fighting.

26
Q

Can we conclusively prove a behavior of a dinosaur?

A

No, but we can support a hypothesis with evidence to improve our certainty.