Lesson 2: death and fossilization Flashcards
Taphonomy definition and what it includes
Tells us what happened between the time of death of the animal and the time it was buried and eventually dug up This includes: How it decays Is scavenged by other organisms Becomes fossilized Erodes
Bloat-and-float
Shortly after death, decay may cause a body to swell with putrid gasses, and this may cause the carcasses of even large animals to float easily and to be transported by shallow and weakly flowing water
Plastic deformation
Taphonomic alteration to the shape of a fossil by the pressure of sediments and rocks result in fracture or breakage causes the shape of a buried fossil to be changed such that, even when the pressure is later removed, the fossil does not return to its original shape
Fossilization
Burial occurs when water washes sand or mud over a carcass (more common at low elevations), hence, it is more common to find bones in wet environments than in dry environments where there is no water to help bury carcasses
Sedimentology
Is the science of how sedimentary rocks form
Sedimentary rocks
- All fossils are found in sedimentary rocks
- Are rocks that form when mineral and organic particles accumulate and become either cemented or compacted together
- Rocks that form when mineral and organic particles accumulate and become either cemented or compacted together
- Take on many forms such as sand stones, mud stones, shales, iron stones, etc.
Igneous rocks
Rocks formed by cooling magma (underground) or lava (above ground)
Metamorphic rocks
When new rocks, sedimentary or igneous rocks, formed by the chemical or physical alteration of other rocks by extreme heat and pressure
Mudstone and shale
- Sedimentary rocks that form from mud and silt
- Lakes are places where large amounts of mud and silt accumulate, and large deposits of mudstone and shale often indicate a former lake bottom environment
- A type of fine-grained sedimentary rock that forms in slow-moving water; typical of a lake or floodplain deposit
Sandstone
- Sedimentary rocks that form from sand
- Sandstone can indicate a former beach, river channel, or ocean floor environment
- Rocks made out of sand
- A type of sedimentary rock composed of sand-sized grains; typically forms in fast moving water such as in rivers, or in alluvial fans, lakes, deserts, beaches, or tidal flats
Coal
A combustible sedimentary rock that forms from dead and compressed remains of plants (usually from wetland forests) that are deeply buried, heated, and pressurized
Limestone
- Usually formed from the accumulation of shells and exoskeletons of small marine invertebrates like plankton
- Almost always indicates a former shallow marine environment
- Lagoons and shallow seas
- A kind of sedimentary rock that is typically composed from the accumulation of shells, exoskeletons, and skeletal fragments from marine organisms like plankton
Preservation styles
Fossils may form in a variety of ways
Permineralization
- Occurs when the empty internal spaces of a bone are filled with minerals
- Most dinosaur bone fossils form through either permineralization or replacement
- These minerals are first dissolved in water and are then deposited in the empty bone spaces as water soaks through the bone
Replacement
Fossilization process in which the original bone gradually decays and minerals fill the space that the bone once occupied
Badlands
Environments that are covered with vegetation are bad places to hope to find fossils. Vegetation covers and holds together an environment’s topsoil and prevents erosion
What is the first step first step in the excavation of a large fossil specimen
overburden removal. where the rock and earth that covers a fossil specimen and that must be removed before the full extent of the specimen can be judged
What is the second step in the excavation of a large fossil specimen
Before any one bone is removed, it is important to map its location relative to the other bones
What is the final step in the excavation of a large fossil specimen
Soak the bone in plaster so that once the plaster hardens, it forms a strong and rigid jacket around the fossil prior to being transported to the laboratory
Disarticulation
- Disarticulation of a skeleton may occur as carnivores eat the carcass, or because the specimen was transported by water
- A skeleton that is separated into its various components
Orientation
In a bonebed, the orientation of the fossils is important: long bones (like the femur or humerus) that are aligned in the same direction indicate that the bones were transported by water, and tell us the direction the water was flowing
Abrasion
The amount of abrasion on the bones can give a relative sense for how far the bones may have been transported by flowing water
Tooth marks
Scratches on the bones can be tooth marks, which indicate that carnivores fed on the carcasses (but do not necessarily indicate that the dinosaur was killed by that carnivore)
what are the Two types of preservation styles
Preminelization and Replacement
Preminelization
Occurs when the internal spaces of tissue and bones are filled with dissolved minerals carried by water
Replacement
Occurs when the original material is replaced by minerals. This is no longer the original material. It is a cast, or impression of the original material
how is the age of formation recorded
The age of formation is usually recorded by GPS, where it gives us information about the latitude, longitude, or any other system and the altitude that the specimen is found on
Long-bone alignment
- This means the long bones, like the bones of the arms and legs will be oriented in the same direction because of the physics behind how water flows
- The degree to which the axes of long bones (usually limb bones) share a similar orientation within a given deposit; in a fluvial context, long-bone alignment is often taken as an indicator of current direction and force
Fluvial deposits
Sediment deposited by rivers and streams. Good for fossil preservation
Lacustrine deposits
Sediment deposited in lake environments; excellent for preserving soft tissues like hair or feathers in the fossil
Airscribe
A tiny jackhammer used to pick at the rocks around the bone without damaging the bone
Gypsona
A type of plaster
Dinosaur provincial park is a great place to look for dinosaur bones because: 2 points
- The region was once covered by massive glaciers
- The dry climate limits plant growth
Do you think bones will fossilize today in the dinosaur provincial park? yes or no, and why?
No, because it is very dry in the badlands and so sand and mud do not build up over animal carcasses which is required for the fossilization process
Are dinosaur fossils ever found in ancient marine sediments? yes or no?
yes
Why may we not find a complete articulated skeleton. three points
- Skeleton is in flowing river
- Carcass is scavenged
- Bones scattered by other animals
Of the following, what is the correct order of events that occur between the death and excavation of a dinosaur? 5 things to order
Death, burial, fossilization, erosion, excavation
Which of the following topics is not part of the science of taphonomy?
How a dinosaur’s injuries heal
Which of the following topics IS part of the science of taphonomy? 3 points
How a dinosaur’s skeleton is fossilized
How a dinosaur’s flesh is scavenged
How a dinosaur’s skin decays
Which of the following helps make Dinosaur Provincial Park a great place to hunt for dinosaur fossils?
The absence of lush vegetation
Which of the following sedimentary rocks is formed in primarily marine environments?
Limestone
What causes plastic deformation?
The weight of rocks and sediments
Which of the following environmental conditions often improves the chance that a skeleton will be preserved as a fossil?
Strong rainstorms
Hadrosaurs can be divided into two groups
Hardosaurines and Lambeosaurus
Hardosaurines
Don’t have anything on their heads
Lambeosaurus
Have big nasal crests
Thought used to produce sounds for communications
3 types of fossils
Isolated fossils, Associated skeleton, Articulated skeleton
Isolated fossils
A single bone found of a particular dinosaur
Associated skeleton
Several bones in a quarry but hard to identify which bones are for which animal
Articulated skeleton
Bones are still together
Biomechanical modelling
- Range of motion
- Bringing the arm out is abduction, bringing the arm in is adduction
