Week 2 - Death and Fossilization

Question 1

what is taphonomy?

Answer 1

the study of all natural process that involve an organism after it dies, includes how it decays, if it’s scavenged, how it becomes fossilized and erodes

Question 2

what are two mechanisms explaining how dino carcasses can be moved considerable distances from the original site of death

Answer 2

1. predators or scavengers can move a carcass
2. bloat and float

Question 3

explain bloat-and-float

Answer 3

decay –> body swells with gasses –> carcass can float easily and can be transported by shallow and weakly flowing water

Question 4

What are some taphonomic factors that can contribute to both the transportation and the disarticulation of a skeleton?

Answer 4

1. partial consumption by carnivores
2. rotten carcasses are easily torn apart and swept away by rivers or floods
3. water currents can carry different portions of a skeleton to diff locations
4. prolonged exposure to sunlight –> weakens and disintegrates bone
5. partial burial –> lose exposed portions
6. portions of skeletons may be trampled by animals or their mineral content leached away by plant roots

Question 5

How can taphonomic factors modify a skeleton even when buried?

Answer 5

1. weight of rock layers and sediment above a bone may flatten it
2. plastic deformation - occurs when pressure causes the shape of a buried fossil to be changed such that, even when the fossil is removed, the fossil does not return to its original shape

Question 6

Describe the processes that must occur for a fossil to be formed and discovered

Answer 6

death –> burial –> fossilization –> erosion –> excavation

Question 7

Describe four different ways a body can be buried, which is the most common way?

Answer 7

1. dies in its own burrow
2. falls into a sinkhole
3. bones are buried by a predator
4. water washes sand or mud over a carcass (most common)

Question 8

What conditions are best for fossilization?

Answer 8

• wet environments
• low elevations where sand and mud carried by water are able to build up

Question 9

Where do we mostly find dino skeletons?

Answer 9

in ancient rivers, streams and lake deposits (fluvial deposits)

Question 10

What deposits have the better chance of preserving soft tissues and why?

Answer 10

lacustrine deposits (lakes):
- little water movement in the lake to disrupt the skeleton
- sediments in lakes are very fine grained (easier to preserve impression of feathers in mud than sand)

Question 11

Why is dino park a good place to find fossils?

Answer 11

1. the region was once covered by massive glaciers: acted like giant bulldozers that removed the top layer of sediment. when they melted it created a lot of water to further erode the rock
2. wind and rain continued to erode the rock
3. sparse vegetation: plant roots help keep the top soil intact

Question 12

Why don’t we usually find dinos in sediments representing ancient deserts?

Answer 12

there wasn’t enough sediment being deposited to preserve the skeleton

Question 13

How is it possible to find dino in sediments representing ancient deserts?

Answer 13

• ancient oasis allowed desert animals to be buried
• sand dune could collapse on the living animal –> burial (occurs when dunes become wet and saturated as during a heavy rainstorm)

Question 14

Describe the three different types of rocks, and which type best preserves fossils

Answer 14

1. sedimentary = mineral and organic particles accumulate and become cemented or compacted together (best for preserving fossils)
2. igneous = forms when magma/lava cools
3. metamorphic = form when sedimentary or igneous rocks are changed by heat and pressure

Question 15

What is sedimentology?

Answer 15

science of how rocks form

Question 16

Why is it important to understand the environmental conditions that form different sedimentary rocks?

Answer 16

clues about the habitat of the organism

Question 17

What minerals make up mudstone and shale, and what environment(s) produce this?

Answer 17

minerals = mud and slit
environments = lakes; therefore, large deposits of mudstone and shale = former lake bottoms

Question 18

What minerals make up sandstone, and what environment(s) produce this?

Answer 18

mineral = sand
environments = beach, river channels, or ocean floor

Question 19

What minerals make up coal, and what environment(s) produce this?

Answer 19

mineral = compressed remains of plants
environment = former swampy environ

Question 20

What minerals make up limestone, and what environment(s) produce this?

Answer 20

mineral = accumulation of shells and exoskeletons of small marine invertebrates
environment = shallow marine environ

Question 21

Why wouldn’t dino park be a good place to preserve fossils today?

Answer 21

very dry - sand and mud won’t accumulate

Question 22

Describe dino park when the dinos lived

Answer 22

• wet and humid
• flat
• rivers and wetlands

Question 23

What are four criteria to find dino bones?

Answer 23

1. exposure
2. rocks have to represent the right age (have to be from the Cretaceous)
3. right environment represented (terrestrial)
4. previous finds

Question 24

What is a preservation style?

Answer 24

different ways that fossils form

Question 25

What are the two different fossilization mechanisms?

Answer 25

1. permineralization = empty internal spaces of a bone are filled with minerals (minerals are dissolved in water and then deposited as water soaks through the bone
2. replacement = original bone gradually decays and minerals fill the space that the bone once occupied

Question 26

Why can’t we find most dino fossils?

Answer 26

most dino fossils formed have been destroyed or are buried too deep for current excavation techniques to detect or reach

Question 27

What are Badlands?

Answer 27

arid environments where vegetation is sparse, erosion rates are large, and where expanses of ancient sedimentary rocks are exposed

Question 28

Why do paleontologists use geologic maps?

Answer 28

identify locations where there are exposures of sedimentary rocks that are the right age to contain dino fossils

Question 29

What is the purpose of a specimen card mark?

Answer 29

identifies:
- where the fossil was found
- identification of the fossil
- age of the formation

Question 30

What are some features of ideal dino skeletons? Why?

Answer 30

freshly and just barely exposed above ground
- fossils not exposed at all = undetectable
- fossily completely exposed for a long time = badly weathered

Question 31

what is overburden?

Answer 31

rock and earth that covers a fossil specimen

Question 32

What tools are used in overburden removal?

Answer 32

far proximity = shovels, pickaxes, jackhammers, and bulldozers

close proximity = hand picks and brushes

Question 33

What are bonebeds?

Answer 33

accumulations of dino bones

Question 34

Why do we map bones relative location to other bones?

Answer 34

• may help in putting a skeleton back together
• may give taphonomic clues

Question 35

Describe how fossil bones are transported

Answer 35

1. bone is wrapped in a layer of protective material
2. covered by strips of burlap that have been soaked in plaster
3. once the plaster hardens, it forms a strong and rigid jacket around the fossil
4. plaster jackets are not open until they’ve reached the lab
5. special glues are applied to fossils to strengthen them

Question 36

What are taphonomic features common to dino bones and what do they indicate?

Answer 36

1. disarticulation –> carnivores ate the carcass or the specimen was transported by water
2. orientation of the fossils is important –> long bones aligned in the same direction indicate that the bones were transported by flowing water
3. amount of abrasions on the bones –> how far the bones were transported by flowing water
4. scratches –> possible tooth marks –> indicate that carnivores fed on the carcasses